FRANCISCAN ENGINEERING REVIEW PROGRAM ELECTRICAL

ELECTRICAL ENGINEERING
ENGINEERING - DC (MACHINES
- DC MACHINES GENERATOR / MOTOR) SEPTEMBER
SUMMER 2019 2020

a = Number of parallel paths in the armature

GENERATOR a = m P ( if simplex lap winding ) Z  2m y  yf
- A machine that converts the inter – action of mechanical energy a = 2 m ( if simplex wave winding ) y y b
and magnetic energy into electrical energy. P 2
- A dynmo is an example of simple generator . m = multiplicity
m = 1 ( if simplex ) , m = 2 ( if duplex )
y = Average pitch
Mech’l Elect’l
Magnetism PARTS OF A DC MACHINE ( GENERATOR ) Z = no. of winding elements on the surface
Input Output of armature core
1. Stationary part - Produces magnetic flux
Generator Nb = 2 ( wave winding )
2. Rotating part
FARADAY’S LAW OF ELECTROMAGNETIC INDUCTION - Armature responsible of converting mechanical energy into
electrical energy
“ Whenever a conductor cuts magnetic flux, dynamically it induces Sample Problems
an emf “ according to the formula TYPES OF ARMATURE WINDINGS
- Armature windings usually uses closed coil type than the open 1. A 4 pole, lap – wound dc armature, the back pitch is 17, if the
coil type. There are two types of closed coil type namely : winding is progressive what is the front pitch ?
a) 32 b) 15 *
1. Ring winding c) 17 d) 13
PNZ
E  =kN 2. Drum winding 2. A 4 pole dc generator with duplex lap winding has 48 slots and
60 a a) lap winding – ( for low voltage, high current generator ). The four element per slot. The flux per pole is 2.5 x 106 maxwells and
finish of each coil is connected to the start of it runs at 1,500 rpm. What is the output voltage ?
the next coil so the winding pitch or a) 60 volts * b) 360 volts
Comparison of emf formula: commutator pitch is unity or one. c) 225 volts d) 120 volts
3. A 4-pole wave wound dc generator has 50 slots and 24 conductors
yb  y f  2m
E2 N  per slot. The flux per pole is 10 mWb. Determine the induced emf in
= 2 2
E1 N1 1 the armature, it it is rotating at a speed of 600 rpm.
a) 240 V* b) 230 V c) 220 V d) 210 V
yb = back pitch ( should be an odd. no. )
yf = front pitch ( should be an odd. no. ) 4. A 4-pole, simplex lap wound, direct current armature has 48 slots
Where : E = generated or induced emf per parallel path + = if the winding is progressive containing 48 coils, each of 10 turns. The flux per pole in the field
E  K N  ( if P , Z and a is considered constants ) - = if the winding is retrogressive structure for this armature, is 500,000 lines. Calculate the speed for
this machine in order that its generated emf be 220 V.
P = Number of Poles a) 2,750 rpm* b) 2,550 rpm c) 2,250 rpm d) 2,000 rpm
Nb = P ( lap winding ) hint: z = 48 (10) (2) = 960 conductors multiply by two kay a = mP =
 = Flux per pole in Weber 8 so in every pole 2 parallel paths or two conductors per element
–8
( 1 Maxwell = 1 x 10 Wb ) Nb = Number of brushes 5. When a generator is being driven at 1,200 rpm, the generated emf
P = No. of poles NZ
P generated
is 125 volts. What will be the emf if the field flux is
GENERATORZ = Total number of conductors Generator decreased by 12% with E the speed increased
= k  Nto 1,800 rpm?
- = Number
A machine that ofthe
converts slots x no.
inter of conductors
– action per slot
of mechanical energy b) wave winding – ( for high voltage, low current generator ). 60 a
a) 135 V b) 145 V c) 155 V d) 165 V*
and magnetic energy into electrical energy. The finish of the coil INDUCTION
FARADAY’S LAW OF ELECTROMAGNETIC is connected to the hint: φ2 = ( 1 – 0.2 ) φ1
- N is=anRotational
A dynmo or simple
example of armature speed in. rpm
generator start of another coil away from the first coil.
“ Whenever a conductor cuts magnetic flux, dynamically it induces Comparison of emf formula:
an emf “ according to the formula
Mech’l Elect’l
E2 N 
Magnetism = 2 2
Input Output E1 N1 1
FRANCISCAN ENGINEERING REVIEW PROGRAM ELECTRICAL
ELECTRICAL ENGINEERING
ENGINEERING - DC (MACHINES
- DC MACHINES GENERATOR / MOTOR) SEPTEMBER
SUMMER 2019 2020

a = Number of parallel paths in the armature

GENERATOR a = m P ( if simplex lap winding ) Z  2m y  yf
- A machine that converts the inter – action of mechanical energy a = 2 m ( if simplex wave winding ) y y b
and magnetic energy into electrical energy. P 2
- A dynmo is an example of simple generator . m = multiplicity
m = 1 ( if simplex ) , m = 2 ( if duplex )
y = Average pitch
Mech’l Elect’l
Magnetism PARTS OF A DC MACHINE ( GENERATOR ) Z = no. of winding elements on the surface
Input Output of armature core
1. Stationary part - Produces magnetic flux
Generator Nb = 2 ( wave winding )
2. Rotating part
FARADAY’S LAW OF ELECTROMAGNETIC INDUCTION - Armature responsible of converting mechanical energy into
electrical energy
“ Whenever a conductor cuts magnetic flux, dynamically it induces Sample Problems
an emf “ according to the formula TYPES OF ARMATURE WINDINGS
- Armature windings usually uses closed coil type than the open 1. A 4 pole, lap – wound dc armature, the back pitch is 17, if the
coil type. There are two types of closed coil type namely : winding is progressive what is the front pitch ?
a) 32 b) 15 *
1. Ring winding c) 17 d) 13
PNZ
E  =kN 2. Drum winding 2. A 4 pole dc generator with duplex lap winding has 48 slots and
60 a a) lap winding – ( for low voltage, high current generator ). The four element per slot. The flux per pole is 2.5 x 106 maxwells and
finish of each coil is connected to the start of it runs at 1,500 rpm. What is the output voltage ?
the next coil so the winding pitch or a) 60 volts * b) 360 volts
Comparison of emf formula: commutator pitch is unity or one. c) 225 volts d) 120 volts
3. A 4-pole wave wound dc generator has 50 slots and 24 conductors
yb  y f  2m
E2 N  per slot. The flux per pole is 10 mWb. Determine the induced emf in
= 2 2
E1 N1 1 the armature, it it is rotating at a speed of 600 rpm.
a) 240 V* b) 230 V c) 220 V d) 210 V
yb = back pitch ( should be an odd. no. )
yf = front pitch ( should be an odd. no. ) 4. A 4-pole, simplex lap wound, direct current armature has 48 slots
Where : E = generated or induced emf per parallel path + = if the winding is progressive containing 48 coils, each of 10 turns. The flux per pole in the field
E  K N  ( if P , Z and a is considered constants ) - = if the winding is retrogressive structure for this armature, is 500,000 lines. Calculate the speed for
this machine in order that its generated emf be 220 V.
P = Number of Poles a) 2,750 rpm* b) 2,550 rpm c) 2,250 rpm d) 2,000 rpm
Nb = P ( lap winding ) hint: z = 48 (10) (2) = 960 conductors multiply by two kay a = mP =
 = Flux per pole in Weber 8 so in every pole 2 parallel paths or two conductors per element
–8
( 1 Maxwell = 1 x 10 Wb ) Nb = Number of brushes 5. When a generator is being driven at 1,200 rpm, the generated emf
Z = Total P = No.ofof
number poles
conductors m =What
is 125 volts. 1 ( will
if simplex
be the )generated
, m = 2 (emf
if duplex )
if the field flux is
Z = Total number of conductors = Number of slots x no. of conductors per slot decreased by 12% with the speed increased to 1,800 rpm?
Where : E =
= Number
generatedof or
slots x no. emf
induced of conductors per
per parallel slot
path b) wave winding – ( for high voltage, low current generator ). a) 135 V b) 145 V c) 155 V d) 165 V*
E  K N  ( if P , Z and a is considered constants ) N = RotationalTheorfinish of thespeed
armature coil is in
connected
rpm to the PARTS
hint: φOF A DC MACHINE ( GENERATOR )
2 = ( 1 – 0.2 ) φ1
N = Rotational or armature speed in rpm start of another coil away from the first coil.
P = Number of Poles a = Number of parallel paths in the armature 1. Stationary part - ( Stator ) Produces magnetic flux
a = m P ( if simplex lap winding )
 = Flux per pole in Weber a = 2 m ( if simplex wave winding ) 2. Rotating part
( 1 Maxwell = 1 x 10 –8 Wb ) - ( Rotor ) Armature responsible of converting mechanical
m = multiplicity energy into electrical energy
FRANCISCAN ENGINEERING REVIEW PROGRAM ELECTRICAL
ELECTRICAL ENGINEERING
ENGINEERING - DC (MACHINES
- DC MACHINES GENERATOR / MOTOR) SEPTEMBER
SUMMER 2019 2020

a = Number of parallel paths in the armature

GENERATOR a = m P ( if simplex lap winding ) Z  2m y  yf
- A machine that converts the inter – action of mechanical energy a = 2 m ( if simplex wave winding ) y y b
and magnetic energy into electrical energy. P 2
- A dynmo is an example of simple generator . m = multiplicity
m = 1 ( if simplex ) , m = 2 ( if duplex )
y = Average pitch
Mech’l Elect’l
Magnetism PARTS OF A DC MACHINE ( GENERATOR ) Z = no. of winding elements on the surface
Input Output of armature core
1. Stationary part - Produces magnetic flux
Generator Nb = 2 ( wave winding )
2. Rotating part
FARADAY’S LAW OF ELECTROMAGNETIC INDUCTION - Armature responsible of converting mechanical energy into
electrical energy
“ Whenever a conductor cuts magnetic flux, dynamically it induces Sample Problems
an emf “ according to the formula TYPES OF ARMATURE WINDINGS
- Armature windings usually uses closed coil type than the open 1. A 4 pole, lap – wound dc armature, the back pitch is 17, if the
coil type. There are two types of closed coil type namely : winding is progressive what is the front pitch ?
a) 32 b) 15 *
1. Ring winding c) 17 d) 13
PNZ
E  =kN 2. Drum winding 2. A 4 pole dc generator with duplex lap winding has 48 slots and
60 a a) lap winding – ( for low voltage, high current generator ). The four element per slot. The flux per pole is 2.5 x 106 maxwells and
finish of each coil is connected to the start of it runs at 1,500 rpm. What is the output voltage ?
the next coil so the winding pitch or a) 60 volts * b) 360 volts
Comparison of emf formula: commutator pitch is unity or one. c) 225 volts d) 120 volts
3. A 4-pole wave wound dc generator has 50 slots and 24 conductors
yb  y f  2m
E2 N  per slot. The flux per pole is 10 mWb. Determine the induced emf in
= 2 2
E1 N1 1 the armature, it it is rotating at a speed of 600 rpm.
a) 240 V* b) 230 V c) 220 V d) 210 V
yb = back pitch ( should be an odd. no. )
yf = front pitch ( should be an odd. no. ) 4. A 4-pole, simplex lap wound, direct current armature has 48 slots
Where : E = generated or induced emf per parallel path + = if the winding is progressive containing 48 coils, each of 10 turns. The flux per pole in the field
E  K N  ( if P , Z and a is considered constants ) - = if the winding is retrogressive structure for this armature, is 500,000 lines. Calculate the speed for
this machine in order that its generated emf be 220 V.
P = Number of Poles a) 2,750 rpm* b) 2,550 rpm c) 2,250 rpm d) 2,000 rpm
Nb = P ( lap winding ) hint: z = 48 (10) (2) = 960 conductors multiply by two kay a = mP =
 = Flux per pole in Weber 8 so in every pole 2 parallel paths or two conductors per element
–8
( 1 Maxwell = 1 x 10 Wb ) Nb = Number of brushes 5. When a generator is being driven at 1,200 rpm, the generated emf
P = No. ofpitch
commutator polesis unity or one. is 125 volts. What will be the generated emf if the field flux is
Z = Total number
TYPES OF ARMATURE WINDINGS of conductors
decreased by 12% with the speed increased to 1,800 rpm?
- Armature windings usually usesx closed
= Number of slots no. of conductors perthe
coil type than slotopen b) wave winding – ( for high voltage,
y  ylow current generator ).
f is
2m a) 135 V b) 145 V Nb =
c) P
155( V
lap windingd)) 165 V*
coil type. There are two types of closed coil type namely : The finish ofbthe coil connected to the hint: φ2 = ( 1 – 0.2 ) φ1
N = Rotational or armature speed in rpm start of another coil away from the first coil. Nb = Number of brushes
1. Ring winding P = No. of poles
yb = back pitch ( should be an odd. no. )
2. Drum winding
yf = front pitch ( should be an odd. no. )
a) lap winding – ( for low voltage, high current generator ). The b) wave winding – ( for high voltage, low current generator ).
+ = if the winding is progressive
finish of each coil is connected to the start of The finish of the coil is connected to the
- = if the winding is retrogressive
the next coil so the winding pitch or start of another coil away from the first coil.
FRANCISCAN ENGINEERING REVIEW PROGRAM ELECTRICAL
ELECTRICAL ENGINEERING
ENGINEERING - DC (MACHINES
- DC MACHINES GENERATOR / MOTOR) SEPTEMBER
SUMMER 2019 2020

a = Number of parallel paths in the armature

GENERATOR a = m P ( if simplex lap winding ) Z  2m y  yf
- A machine that converts the inter – action of mechanical energy a = 2 m ( if simplex wave winding ) y y b
and magnetic energy into electrical energy. P 2
- A dynmo is an example of simple generator . m = multiplicity
m = 1 ( if simplex ) , m = 2 ( if duplex )
y = Average pitch
Mech’l Elect’l
Magnetism PARTS OF A DC MACHINE ( GENERATOR ) Z = no. of winding elements on the surface
Input Output of armature core
1. Stationary part - Produces magnetic flux
Generator Nb = 2 ( wave winding )
2. Rotating part
FARADAY’S LAW OF ELECTROMAGNETIC INDUCTION - Armature responsible of converting mechanical energy into
electrical energy
“ Whenever a conductor cuts magnetic flux, dynamically it induces Sample Problems
an emf “ according to the formula TYPES OF ARMATURE WINDINGS
- Armature windings usually uses closed coil type than the open 1. A 4 pole, lap – wound dc armature, the back pitch is 17, if the
coil type. There are two types of closed coil type namely : winding is progressive what is the front pitch ?
a) 32 b) 15 *
1. Ring winding c) 17 d) 13
PNZ
E  =kN 2. Drum winding 2. A 4 pole dc generator with duplex lap winding has 48 slots and
60 a a) lap winding – ( for low voltage, high current generator ). The four element per slot. The flux per pole is 2.5 x 106 maxwells and
finish of each coil is connected to the start of it runs at 1,500 rpm. What is the output voltage ?
the next coil so the winding pitch or a) 60 volts * b) 360 volts
Comparison of emf formula: commutator pitch is unity or one. c) 225 volts d) 120 volts
3. A 4-pole wave wound dc generator has 50 slots and 24 conductors
yb  y f  2m
E2 N  per slot. The flux per pole is 10 mWb. Determine the induced emf in
= 2 2
E1 N1 1 the armature, it it is rotating at a speed of 600 rpm.
a) 240 V* b) 230 V c) 220 V d) 210 V
yb = back pitch ( should be an odd. no. )
yf = front pitch ( should be an odd. no. ) 4. A 4-pole, simplex lap wound, direct current armature has 48 slots
Where : E = generated or induced emf per parallel path + = if the winding is progressive containing 48 coils, each of 10 turns. The flux per pole in the field
E  K N  ( if P , Z and a is considered constants ) - = if the winding is retrogressive structure for this armature, is 500,000 lines. Calculate the speed for
this machine in order that its generated emf be 220 V.
P = Number of Poles a) 2,750 rpm* b) 2,550 rpm c) 2,250 rpm d) 2,000 rpm
Nb = P ( lap winding ) hint: z = 48 (10) (2) = 960 conductors multiply by two kay a = mP =
 = Flux per pole in Weber 8 so in every pole 2 parallel paths or two conductors per element
–8
( 1 Maxwell = 1 x 10 Wb ) Nb = Number of brushes 5. When a generator is being driven at 1,200 rpm, the generated emf
P = No. of poles Sample
is 125Problems
volts. What will be the generated emf if the field flux is
Z = Total number of conductors
Z  2m yb  y f Nb = 2 ( wave winding ) decreased by 12% with the speed increased to 1,800 rpm?
y = Number of slots x no. yofconductors per slot b) wave winding – ( for high voltage, low current generator ). 1. A
a)4135
pole,
V lap – wound
b) 145 dc
V armature,c)the
155back
V pitch is d)
17,165
if the
V*
P 2 The finish of the coil is connected to the winding
hint: φ2 =is progressive
( 1 – 0.2 ) φ1what is the front pitch ?
N = Rotational or armature speed in rpm start of another coil away from the first coil. a) 32 b) 15 *
Number of parallel current paths ( a ) in the armature. c) 17 d) 13
y = Average pitch
2. A 4 pole dc generator with duplex lap winding has 48 slots and
a = mP for lap winding
Z = no. of winding elements on the surface four element per slot. The flux per pole is 2.5 x 106 maxwells and
a = 2m for wave winding
of armature core it runs at 1,500 rpm. What is the output voltage ?
FRANCISCAN ENGINEERING REVIEW PROGRAM ELECTRICAL
ELECTRICAL ENGINEERING
ENGINEERING - DC (MACHINES
- DC MACHINES GENERATOR / MOTOR) SEPTEMBER
SUMMER 2019 2020

a = Number of parallel paths in the armature

GENERATOR a = m P ( if simplex lap winding ) Z  2m y  yf
- A machine that converts the inter – action of mechanical energy a = 2 m ( if simplex wave winding ) y y b
and magnetic energy into electrical energy. P 2
- A dynmo is an example of simple generator . m = multiplicity
m = 1 ( if simplex ) , m = 2 ( if duplex )
y = Average pitch
Mech’l Elect’l
Magnetism PARTS OF A DC MACHINE ( GENERATOR ) Z = no. of winding elements on the surface
Input Output of armature core
1. Stationary part - Produces magnetic flux
Generator Nb = 2 ( wave winding )
2. Rotating part
FARADAY’S LAW OF ELECTROMAGNETIC INDUCTION - Armature responsible of converting mechanical energy into
electrical energy
“ Whenever a conductor cuts magnetic flux, dynamically it induces Sample Problems
an emf “ according to the formula TYPES OF ARMATURE WINDINGS
- Armature windings usually uses closed coil type than the open 1. A 4 pole, lap – wound dc armature, the back pitch is 17, if the
coil type. There are two types of closed coil type namely : winding is progressive what is the front pitch ?
a) 32 b) 15 *
1. Ring winding c) 17 d) 13
PNZ
E  =kN 2. Drum winding 2. A 4 pole dc generator with duplex lap winding has 48 slots and
60 a a) lap winding – ( for low voltage, high current generator ). The four element per slot. The flux per pole is 2.5 x 106 maxwells and
finish of each coil is connected to the start of it runs at 1,500 rpm. What is the output voltage ?
the next coil so the winding pitch or a) 60 volts * b) 360 volts
Comparison of emf formula: commutator pitch is unity or one. c) 225 volts d) 120 volts
3. A 4-pole wave wound dc generator has 50 slots and 24 conductors
yb  y f  2m
E2 N  per slot. The flux per pole is 10 mWb. Determine the induced emf in
= 2 2
E1 N1 1 the armature, it it is rotating at a speed of 600 rpm.
a) 240 V* b) 230 V c) 220 V d) 210 V
yb = back pitch ( should be an odd. no. )
yf = front pitch ( should be an odd. no. ) 4. A 4-pole, simplex lap wound, direct current armature has 48 slots
Where : E = generated or induced emf per parallel path + = if the winding is progressive containing 48 coils, each of 10 turns. The flux per pole in the field
E  K N  ( if P , Z and a is considered constants ) - = if the winding is retrogressive structure for this armature, is 500,000 lines. Calculate the speed for
this machine in order that its generated emf be 220 V.
P = Number of Poles a) 2,750 rpm* b) 2,550 rpm c) 2,250 rpm d) 2,000 rpm
Nb = P ( lap winding ) hint: z = 48 (10) (2) = 960 conductors multiply by two kay a = mP =
 = Flux per pole in Weber 8 so in every pole 2 parallel paths or two conductors per element
–8
( 1 Maxwell = 1 x 10 Wb ) Nb = Number of brushes 5. When a generator is being driven at 1,200 rpm, the generated emf
a) 60 volts * b) 360 volts P = isNo.
structure for this armature, of poles
500,000 lines. Calculate the speed is
is 125
125 volts.
volts. What
What will
will be
be the
the generated
generated emf
emf ifif the
the field
field flux
flux is
is
Z = Total number of conductors
c) 225 volts d) 120 volts for decreased
decreased by by 12%
12% with
with the
the speed
speed increased
increased to to 1,800
1,800 rpm?
rpm?
= Number of slots x no. of conductors per slot b)machine
this wave winding
in order–that
( foritshigh voltage,emf
generated lowbecurrent generator ).
220 V. a)
3. A 4-pole wave wound dc generator has 50 slots and 24 conductors a) 135
135 VV b)
b) 145
145 V V c)
c) 155
155 V
V d)
d) 165
165 V*V*
a) 2,750 rpm* b) 2,550The rpmfinish c)of 2,250
the coil is connected
rpm to the
d) 2,000 rpm hint:
hint: φ
φ22 == (( 11 –– 0.2
0.2 )) φφ11
per slot. The
N flux per pole isor10
= Rotational mWb. Determine
armature the induced emf
speed in rpm start of another coil away from the first coil.
in
hint: z = 48 (10) (2) = 960 conductors multiply by two kay a = mP TWO GENERAL TYPES OF GENERATOR
the armature, it it is rotating at a speed of 600 rpm.
=
a) 240 V* b) 230 V c) 220 V d) 210 V
8 so in every pole 2 parallel paths or two conductors per element 1. Separately Excited Generator
4. A 4-pole, simplex lap wound, direct current armature has 48 slots These are generators whose fields are energized from an
5. When a generator is being driven at 1,200 rpm, the generated emf
containing 48 coils, each of 10 turns. The flux per pole in the field independent external source of dc voltage.
FRANCISCAN ENGINEERING REVIEW PROGRAM ELECTRICAL
ELECTRICAL ENGINEERING
ENGINEERING - DC (MACHINES
- DC MACHINES GENERATOR / MOTOR) SEPTEMBER
SUMMER 2019 2020

a = Number of parallel paths in the armature

GENERATOR a = m P ( if simplex lap winding ) Z  2m y  yf
- A machine that converts the inter – action of mechanical energy a = 2 m ( if simplex wave winding ) y y b
and magnetic energy into electrical energy. P 2
- A dynmo is an example of simple generator . m = multiplicity
m = 1 ( if simplex ) , m = 2 ( if duplex )
y = Average pitch
Mech’l Elect’l
Magnetism PARTS OF A DC MACHINE ( GENERATOR ) Z = no. of winding elements on the surface
Input Output of armature core
1. Stationary part - Produces magnetic flux
Generator Nb = 2 ( wave winding )
2. Rotating part
FARADAY’S LAW OF ELECTROMAGNETIC INDUCTION - Armature responsible of converting mechanical energy into
electrical energy
“ Whenever a conductor cuts magnetic flux, dynamically it induces Sample Problems
an emf “ according to the formula TYPES OF ARMATURE WINDINGS
- Armature windings usually uses closed coil type than the open 1. A 4 pole, lap – wound dc armature, the back pitch is 17, if the
coil type. There are two types of closed coil type namely : winding is progressive what is the front pitch ?
a) 32 b) 15 *
1. Ring winding c) 17 d) 13
PNZ
E  =kN 2. Drum winding 2. A 4 pole dc generator with duplex lap winding has 48 slots and
60 a a) lap winding – ( for low voltage, high current generator ). The four element per slot. The flux per pole is 2.5 x 106 maxwells and
finish of each coil is connected to the start of it runs at 1,500 rpm. What is the output voltage ?
the next coil so the winding pitch or a) 60 volts * b) 360 volts
Comparison of emf formula: commutator pitch is unity or one. c) 225 volts d) 120 volts
3. A 4-pole wave wound dc generator has 50 slots and 24 conductors
yb  y f  2m
E2 N  per slot. The flux per pole is 10 mWb. Determine the induced emf in
= 2 2
E1 N1 1 the armature, it it is rotating at a speed of 600 rpm.
a) 240 V* b) 230 V c) 220 V d) 210 V
yb = back pitch ( should be an odd. no. )
yf = front pitch ( should be an odd. no. ) 4. A 4-pole, simplex lap wound, direct current armature has 48 slots
Where : E = generated or induced emf per parallel path + = if the winding is progressive containing 48 coils, each of 10 turns. The flux per pole in the field
E  K N  ( if P , Z and a is considered constants ) - = if the winding is retrogressive structure for this armature, is 500,000 lines. Calculate the speed for
this machine in order that its generated emf be 220 V.
P = Number of Poles a) 2,750 rpm* b) 2,550 rpm c) 2,250 rpm d) 2,000 rpm
Nb = P ( lap winding ) hint: z = 48 (10) (2) = 960 conductors multiply by two kay a = mP =
 = Flux per pole in Weber 8 so in every pole 2 parallel paths or two conductors per element
–8
( 1 Maxwell = 1 x 10 Wb ) Nb = Number of brushes 5. When a generator is being driven at 1,200 rpm, the generated emf
The field winding is inP series
= No.with of poles
the armature. This type of is I125
= Ivolts.
a = If What
I =will
Po be
/ Vthe generated emf if the field flux is
2. Z = Total
Self – Excited number of conductors
Generator generator cannot build-up induced voltage at no-load condition. decreased by 12% with the speed increased to 1,800 rpm?
= Number of slotsfield
These are generators whose x no. of conductors
magnets per slotfrom
are energized b) wave
Hence, winding
to start – ( rheostat
a load for high voltage,
must below current generator
connected in order to ). 2. a)Voltage
135 V b) 145 V c) 155 V I d) 165 V*
its own output. start a series generator.TheIt finish of the coil
is impossible to is connected
determine theto the hint: φ2 = ( 1 – 0.2 ) φ1
N = Rotational or armature speed in rpm no-load terminal voltage.start of another coil away from the first coil. E = V + Ia Ra + If Rf + Vbrush Fff
I
3. Power V
TYPES OF SELF – EXCITED GENERATOR Circuit Analysis : IA P
Po = V I
A. The series generator 1. Current Pin = Po + PLOSSES O

E R
A
FRANCISCAN ENGINEERING REVIEW PROGRAM ELECTRICAL
ELECTRICAL ENGINEERING
ENGINEERING - DC (MACHINES
- DC MACHINES GENERATOR / MOTOR) SEPTEMBER
SUMMER 2019 2020

a = Number of parallel paths in the armature

GENERATOR a = m P ( if simplex lap winding ) Z  2m y  yf
- A machine that converts the inter – action of mechanical energy a = 2 m ( if simplex wave winding ) y y b
and magnetic energy into electrical energy. P 2
- A dynmo is an example of simple generator . m = multiplicity
m = 1 ( if simplex ) , m = 2 ( if duplex )
y = Average pitch
Mech’l Elect’l
Magnetism PARTS OF A DC MACHINE ( GENERATOR ) Z = no. of winding elements on the surface
Input Output of armature core
1. Stationary part - Produces magnetic flux
Generator Nb = 2 ( wave winding )
2. Rotating part
FARADAY’S LAW OF ELECTROMAGNETIC INDUCTION - Armature responsible of converting mechanical energy into
electrical energy
“ Whenever a conductor cuts magnetic flux, dynamically it induces Sample Problems
an emf “ according to the formula TYPES OF ARMATURE WINDINGS
- Armature windings usually uses closed coil type than the open 1. A 4 pole, lap – wound dc armature, the back pitch is 17, if the
coil type. There are two types of closed coil type namely : winding is progressive what is the front pitch ?
a) 32 b) 15 *
1. Ring winding c) 17 d) 13
PNZ
E  =kN 2. Drum winding 2. A 4 pole dc generator with duplex lap winding has 48 slots and
60 a a) lap winding – ( for low voltage, high current generator ). The four element per slot. The flux per pole is 2.5 x 106 maxwells and
finish of each coil is connected to the start of it runs at 1,500 rpm. What is the output voltage ?
the next coil so the winding pitch or a) 60 volts * b) 360 volts
Comparison of emf formula: commutator pitch is unity or one. c) 225 volts d) 120 volts
3. A 4-pole wave wound dc generator has 50 slots and 24 conductors
yb  y f  2m
E2 N  per slot. The flux per pole is 10 mWb. Determine the induced emf in
= 2 2
E1 N1 1 the armature, it it is rotating at a speed of 600 rpm.
a) 240 V* b) 230 V c) 220 V d) 210 V
yb = back pitch ( should be an odd. no. )
yf = front pitch ( should be an odd. no. ) 4. A 4-pole, simplex lap wound, direct current armature has 48 slots
Where : E = generated or induced emf per parallel path + = if the winding is progressive containing 48 coils, each of 10 turns. The flux per pole in the field
E  K N  ( if P , Z and a is considered constants ) - = if the winding is retrogressive structure for this armature, is 500,000 lines. Calculate the speed for
this machine in order that its generated emf be 220 V.
P = Number of Poles a) 2,750 rpm* b) 2,550 rpm c) 2,250 rpm d) 2,000 rpm
Nb = P ( lap winding ) hint: z = 48 (10) (2) = 960 conductors multiply by two kay a = mP =
 = Flux per pole in Weber 8 so in every pole 2 parallel paths or two conductors per element
–8
( 1 Maxwell = 1 x 10 Wb ) Nb = Number of brushes 5. When a generator is being driven at 1,200 rpm, the generated emf
PD = E Ia = Power Developed b) P = No. of poles
Electrical Efficiency Circuit Analysis
is 125 :
volts. What will be the generated emf if the field flux is
Z = Total number of conductors
decreased by 12% with the speed increased to 1,800 rpm?
Power Flow =: P
Number of slots x no. of conductors per slot
in - PSP = PD
b) %wave winding
ee = ( Po / P–D()for high voltage, low current generator ).
x 100 1. a)Current
135 V b) 145 V c) 155 V d) 165 V*
PD – Pcu = Po The finish of the coil is connected to the hint: φ2 = ( 1 – 0.2 ) φ1
N = Rotational or armature speed in rpm B. Shunt Generator start of another coil away from the first coil. I = I a + If I = Po / V I I
4. Efficiency The field winding is connected in parallel with the armature A f

a) Commercial Efficiency circuit. Hence, shunt generator can build up voltage even at no- If = V f / R f
load condition. Current will then flow from the armature circuit to I V
E RA Rf
% e = ( Po / Pin ) x 100 the field windings and vice versa. 2. Voltages PO
FRANCISCAN ENGINEERING REVIEW PROGRAM ELECTRICAL
ELECTRICAL ENGINEERING
ENGINEERING - DC (MACHINES
- DC MACHINES GENERATOR / MOTOR) SEPTEMBER
SUMMER 2019 2020

a = Number of parallel paths in the armature

GENERATOR a = m P ( if simplex lap winding ) Z  2m y  yf
- A machine that converts the inter – action of mechanical energy a = 2 m ( if simplex wave winding ) y y b
and magnetic energy into electrical energy. P 2
- A dynmo is an example of simple generator . m = multiplicity
m = 1 ( if simplex ) , m = 2 ( if duplex )
y = Average pitch
Mech’l Elect’l
Magnetism PARTS OF A DC MACHINE ( GENERATOR ) Z = no. of winding elements on the surface
Input Output of armature core
1. Stationary part - Produces magnetic flux
Generator Nb = 2 ( wave winding )
2. Rotating part
FARADAY’S LAW OF ELECTROMAGNETIC INDUCTION - Armature responsible of converting mechanical energy into
electrical energy
“ Whenever a conductor cuts magnetic flux, dynamically it induces Sample Problems
an emf “ according to the formula TYPES OF ARMATURE WINDINGS
- Armature windings usually uses closed coil type than the open 1. A 4 pole, lap – wound dc armature, the back pitch is 17, if the
coil type. There are two types of closed coil type namely : winding is progressive what is the front pitch ?
a) 32 b) 15 *
1. Ring winding c) 17 d) 13
PNZ
E  =kN 2. Drum winding 2. A 4 pole dc generator with duplex lap winding has 48 slots and
60 a a) lap winding – ( for low voltage, high current generator ). The four element per slot. The flux per pole is 2.5 x 106 maxwells and
finish of each coil is connected to the start of it runs at 1,500 rpm. What is the output voltage ?
the next coil so the winding pitch or a) 60 volts * b) 360 volts
Comparison of emf formula: commutator pitch is unity or one. c) 225 volts d) 120 volts
3. A 4-pole wave wound dc generator has 50 slots and 24 conductors
yb  y f  2m
E2 N  per slot. The flux per pole is 10 mWb. Determine the induced emf in
= 2 2
E1 N1 1 the armature, it it is rotating at a speed of 600 rpm.
a) 240 V* b) 230 V c) 220 V d) 210 V
yb = back pitch ( should be an odd. no. )
yf = front pitch ( should be an odd. no. ) 4. A 4-pole, simplex lap wound, direct current armature has 48 slots
Where : E = generated or induced emf per parallel path + = if the winding is progressive containing 48 coils, each of 10 turns. The flux per pole in the field
E  K N  ( if P , Z and a is considered constants ) - = if the winding is retrogressive structure for this armature, is 500,000 lines. Calculate the speed for
this machine in order that its generated emf be 220 V.
P = Number of Poles a) 2,750 rpm* b) 2,550 rpm c) 2,250 rpm d) 2,000 rpm
Nb = P ( lap winding ) hint: z = 48 (10) (2) = 960 conductors multiply by two kay a = mP =
 = Flux per pole in Weber 8 so in every pole 2 parallel paths or two conductors per element
–8
( 1 Maxwell = 1 x 10 Wb ) Nb = Number of brushes 5. When a generator is being driven at 1,200 rpm, the generated emf
E = V + I a Ra V = V f VNL  VPFL = No. of poles is 125 volts. What will be the generated emf if the field flux is
Z = Total number of conductors % Reg. = X100 Power Flow
VFL– ( for high voltage, low current generator ). decreased by :12%
Pin with
- PSPthe
=Pspeed
D increased to 1,800 rpm?
E = Vf + Ia=RNumber
a + Vbrush
of slots x no. of conductors per slot b) wave winding a) 135 V PD145
b) – Pcu
V = Po c) 155 V d) 165 V*
The finish of the coil is connected to the hint: φ2 = ( 1 – 0.2 ) φ1
N = Rotational or armature speed in rpm 4. Power start of another coil away from the first coil. 5. Efficiency
3. Voltage Regulation a) Commercial Efficiency
The degree of change in armature voltage produce by the Po = V I
application of load. Pin = Po + PLOSSES % e = ( Po / Pin ) x 100

PD = E Ia = Power Developed b) Electrical Efficiency

FRANCISCAN ENGINEERING REVIEW PROGRAM ELECTRICAL
ELECTRICAL ENGINEERING
ENGINEERING - DC (MACHINES
- DC MACHINES GENERATOR / MOTOR) SEPTEMBER
SUMMER 2019 2020

a = Number of parallel paths in the armature

GENERATOR a = m P ( if simplex lap winding ) Z  2m y  yf
- A machine that converts the inter – action of mechanical energy a = 2 m ( if simplex wave winding ) y y b
and magnetic energy into electrical energy. P 2
- A dynmo is an example of simple generator . m = multiplicity
m = 1 ( if simplex ) , m = 2 ( if duplex )
y = Average pitch
Mech’l Elect’l
Magnetism PARTS OF A DC MACHINE ( GENERATOR ) Z = no. of winding elements on the surface
Input Output of armature core
1. Stationary part - Produces magnetic flux
Generator Nb = 2 ( wave winding )
2. Rotating part
FARADAY’S LAW OF ELECTROMAGNETIC INDUCTION - Armature responsible of converting mechanical energy into
electrical energy
“ Whenever a conductor cuts magnetic flux, dynamically it induces Sample Problems
an emf “ according to the formula TYPES OF ARMATURE WINDINGS
- Armature windings usually uses closed coil type than the open 1. A 4 pole, lap – wound dc armature, the back pitch is 17, if the
coil type. There are two types of closed coil type namely : winding is progressive what is the front pitch ?
a) 32 b) 15 *
1. Ring winding c) 17 d) 13
PNZ
E  =kN 2. Drum winding 2. A 4 pole dc generator with duplex lap winding has 48 slots and
60 a a) lap winding – ( for low voltage, high current generator ). The four element per slot. The flux per pole is 2.5 x 106 maxwells and
finish of each coil is connected to the start of it runs at 1,500 rpm. What is the output voltage ?
the next coil so the winding pitch or a) 60 volts * b) 360 volts
Comparison of emf formula: commutator pitch is unity or one. c) 225 volts d) 120 volts
3. A 4-pole wave wound dc generator has 50 slots and 24 conductors
yb  y f  2m
E2 N  per slot. The flux per pole is 10 mWb. Determine the induced emf in
= 2 2
E1 N1 1 the armature, it it is rotating at a speed of 600 rpm.
a) 240 V* b) 230 V c) 220 V d) 210 V
yb = back pitch ( should be an odd. no. )
yf = front pitch ( should be an odd. no. ) 4. A 4-pole, simplex lap wound, direct current armature has 48 slots
Where : E = generated or induced emf per parallel path + = if the winding is progressive containing 48 coils, each of 10 turns. The flux per pole in the field
E  K N  ( if P , Z and a is considered constants ) - = if the winding is retrogressive structure for this armature, is 500,000 lines. Calculate the speed for
this machine in order that its generated emf be 220 V.
P = Number of Poles a) 2,750 rpm* b) 2,550 rpm c) 2,250 rpm d) 2,000 rpm
Nb = P ( lap winding ) hint: z = 48 (10) (2) = 960 conductors multiply by two kay a = mP =
 = Flux per pole in Weber 8 so in every pole 2 parallel paths or two conductors per element
–8
( 1 Maxwell = 1 x 10 Wb ) Nb = Number of brushes 5. When a generator is being driven at 1,200 rpm, the generated emf
P = No. of poles
Short-shunt compound generator is 125 volts. What will be the generated emf if the field flux is
% eZe = =( PTotal number of conductors
o / PD ) x 100 When the series field is connected in series with the load If = V f / R
decreased byf 12% with the speed increased to 1,800 rpm?
= Number of slots x no. of conductors per slot b) wave winding – ( for high voltage, low current generator ). a) 135 V b) 145 V c) 155 V d) 165 V*
6. Application Circuit Analysis : The finish of the coil is connected to the 2. hint:
Voltages
φ2 = ( 1 – 0.2 ) φ1
Exciter N = field
to the Rotational or armature speed in rpm
of AC generators start of another coil away from the first coil.
Charge Batteries 1. Currents E = V + Is Rs + Ia Ra + Vbrush
C. Compound Generator IA
Rf RS
When there is an additional field which we call as the series field. Ia = I + If or Ia = Is + If Vf = V + V s
Generally, there are two types of compound generator namely :
I
Is = I I s = V s / Rs E
If V
PO
FRANCISCAN ENGINEERING REVIEW PROGRAM ELECTRICAL
ELECTRICAL ENGINEERING
ENGINEERING - DC (MACHINES
- DC MACHINES GENERATOR / MOTOR) SEPTEMBER
SUMMER 2019 2020

a = Number of parallel paths in the armature

GENERATOR a = m P ( if simplex lap winding ) Z  2m y  yf
- A machine that converts the inter – action of mechanical energy a = 2 m ( if simplex wave winding ) y y b
and magnetic energy into electrical energy. P 2
- A dynmo is an example of simple generator . m = multiplicity
m = 1 ( if simplex ) , m = 2 ( if duplex )
y = Average pitch
Mech’l Elect’l
Magnetism PARTS OF A DC MACHINE ( GENERATOR ) Z = no. of winding elements on the surface
Input Output of armature core
1. Stationary part - Produces magnetic flux
Generator Nb = 2 ( wave winding )
2. Rotating part
FARADAY’S LAW OF ELECTROMAGNETIC INDUCTION - Armature responsible of converting mechanical energy into
electrical energy
“ Whenever a conductor cuts magnetic flux, dynamically it induces Sample Problems
an emf “ according to the formula TYPES OF ARMATURE WINDINGS
- Armature windings usually uses closed coil type than the open 1. A 4 pole, lap – wound dc armature, the back pitch is 17, if the
coil type. There are two types of closed coil type namely : winding is progressive what is the front pitch ?
a) 32 b) 15 *
1. Ring winding c) 17 d) 13
PNZ
E  =kN 2. Drum winding 2. A 4 pole dc generator with duplex lap winding has 48 slots and
60 a a) lap winding – ( for low voltage, high current generator ). The four element per slot. The flux per pole is 2.5 x 106 maxwells and
finish of each coil is connected to the start of it runs at 1,500 rpm. What is the output voltage ?
the next coil so the winding pitch or a) 60 volts * b) 360 volts
Comparison of emf formula: commutator pitch is unity or one. c) 225 volts d) 120 volts
3. A 4-pole wave wound dc generator has 50 slots and 24 conductors
yb  y f  2m
E2 N  per slot. The flux per pole is 10 mWb. Determine the induced emf in
= 2 2
E1 N1 1 the armature, it it is rotating at a speed of 600 rpm.
a) 240 V* b) 230 V c) 220 V d) 210 V
yb = back pitch ( should be an odd. no. )
yf = front pitch ( should be an odd. no. ) 4. A 4-pole, simplex lap wound, direct current armature has 48 slots
Where : E = generated or induced emf per parallel path + = if the winding is progressive containing 48 coils, each of 10 turns. The flux per pole in the field
E  K N  ( if P , Z and a is considered constants ) - = if the winding is retrogressive structure for this armature, is 500,000 lines. Calculate the speed for
this machine in order that its generated emf be 220 V.
P = Number of Poles a) 2,750 rpm* b) 2,550 rpm c) 2,250 rpm d) 2,000 rpm
Nb = P ( lap winding ) hint: z = 48 (10) (2) = 960 conductors multiply by two kay a = mP =
 = Flux per pole in Weber 8 so in every pole 2 parallel paths or two conductors per element
–8
( 1 Maxwell = 1 x 10 Wb ) Nb = Number of brushes 5. When a generator is being driven at 1,200 rpm, the generated emf
VNL  VFL P = No. of poles is 125 volts. What will be the generated emf if the field flux is
3. % Reg. Z= = Total number
X100of conductors Power Flow : Pin - PSP = PD % ee by
decreased = 12%
( Po /with
PD )the
x 100
speed increased to 1,800 rpm?
VFL of slots x no. of conductors per slot
= Number b) wave winding
PD – –Pcu
( for= high
Po voltage, low current generator ). a) 135 V b) 145 V c) 155 V d) 165 V*
The finish of the coil is connected to the Long-shunt
hint: φ2 =compound
( 1 – 0.2 ) generator
φ1
4. Power N = Rotational or armature speed in rpm 5. Efficiency start of another coil away from the first coil. When the series field is connected in series with the armature
a) Commercial Efficiency circuit.
Po = V I
Pin = Po + PLOSSES % e = ( Po / Pin ) x 100 Circuit Analysis :

PD = E Ia = Power Developed b) Electrical Efficiency 1. Currents

FRANCISCAN ENGINEERING REVIEW PROGRAM ELECTRICAL
ELECTRICAL ENGINEERING
ENGINEERING - DC (MACHINES
- DC MACHINES GENERATOR / MOTOR) SEPTEMBER
SUMMER 2019 2020

a = Number of parallel paths in the armature

GENERATOR a = m P ( if simplex lap winding ) Z  2m y  yf
- A machine that converts the inter – action of mechanical energy a = 2 m ( if simplex wave winding ) y y b
and magnetic energy into electrical energy. P 2
- A dynmo is an example of simple generator . m = multiplicity
m = 1 ( if simplex ) , m = 2 ( if duplex )
y = Average pitch
Mech’l Elect’l
Magnetism PARTS OF A DC MACHINE ( GENERATOR ) Z = no. of winding elements on the surface
Input Output of armature core
1. Stationary part - Produces magnetic flux
Generator Nb = 2 ( wave winding )
2. Rotating part
FARADAY’S LAW OF ELECTROMAGNETIC INDUCTION - Armature responsible of converting mechanical energy into
electrical energy
“ Whenever a conductor cuts magnetic flux, dynamically it induces Sample Problems
an emf “ according to the formula TYPES OF ARMATURE WINDINGS
- Armature windings usually uses closed coil type than the open 1. A 4 pole, lap – wound dc armature, the back pitch is 17, if the
coil type. There are two types of closed coil type namely : winding is progressive what is the front pitch ?
a) 32 b) 15 *
1. Ring winding c) 17 d) 13
PNZ
E  =kN 2. Drum winding 2. A 4 pole dc generator with duplex lap winding has 48 slots and
60 a a) lap winding – ( for low voltage, high current generator ). The four element per slot. The flux per pole is 2.5 x 106 maxwells and
finish of each coil is connected to the start of it runs at 1,500 rpm. What is the output voltage ?
the next coil so the winding pitch or a) 60 volts * b) 360 volts
Comparison of emf formula: commutator pitch is unity or one. c) 225 volts d) 120 volts
3. A 4-pole wave wound dc generator has 50 slots and 24 conductors
yb  y f  2m
E2 N  per slot. The flux per pole is 10 mWb. Determine the induced emf in
= 2 2
E1 N1 1 the armature, it it is rotating at a speed of 600 rpm.
a) 240 V* b) 230 V c) 220 V d) 210 V
yb = back pitch ( should be an odd. no. )
yf = front pitch ( should be an odd. no. ) 4. A 4-pole, simplex lap wound, direct current armature has 48 slots
Where : E = generated or induced emf per parallel path + = if the winding is progressive containing 48 coils, each of 10 turns. The flux per pole in the field
E  K N  ( if P , Z and a is considered constants ) - = if the winding is retrogressive structure for this armature, is 500,000 lines. Calculate the speed for
this machine in order that its generated emf be 220 V.
P = Number of Poles a) 2,750 rpm* b) 2,550 rpm c) 2,250 rpm d) 2,000 rpm
Nb = P ( lap winding ) hint: z = 48 (10) (2) = 960 conductors multiply by two kay a = mP =
 = Flux per pole in Weber 8 so in every pole 2 parallel paths or two conductors per element
–8
( 1 Maxwell = 1 x 10 Wb ) Nb = Number of brushes 5. When a generator is being driven at 1,200 rpm, the generated emf
Vf = V P = No. of poles is P125
D =volts.
E Ia What
= Power
will Developed
be the generated emf if the field flux is
Ia = I +Z If or = Total
Is = number
I + If of conductors decreased by 12% with the speed increased to 1,800 rpm?
= Number of slots x no. of conductors
RS perI slot b) wave winding
VNL  –VFL
( for high voltage, low current generator ). a)Power
135 V Flow : b)
Pin145
- PSP
V = PD c) 155 V d) 165 V*
Is = I a I s = V s / Rs Rf 3. % Reg. = TheX100
finish of the coil is connected to the PD –) φ
hint: φ2 = ( 1 – 0.2 P1cu = Po
N = Rotational or armature speed in rpm VFL start of another coil away from the first coil.
If = V f / R f IA V 5. Efficiency
PO 4. Power a) Commercial Efficiency
If
2. Voltages E
Po = V I Pin = Po + PLOSSES % e = ( Po / Pin ) x 100
E = V + Is Rs + Ia Ra + Vbrush
FRANCISCAN ENGINEERING REVIEW PROGRAM ELECTRICAL
ELECTRICAL ENGINEERING
ENGINEERING - DC (MACHINES
- DC MACHINES GENERATOR / MOTOR) SEPTEMBER
SUMMER 2019 2020

a = Number of parallel paths in the armature

GENERATOR a = m P ( if simplex lap winding ) Z  2m y  yf
- A machine that converts the inter – action of mechanical energy a = 2 m ( if simplex wave winding ) y y b
and magnetic energy into electrical energy. P 2
- A dynmo is an example of simple generator . m = multiplicity
m = 1 ( if simplex ) , m = 2 ( if duplex )
y = Average pitch
Mech’l Elect’l
Magnetism PARTS OF A DC MACHINE ( GENERATOR ) Z = no. of winding elements on the surface
Input Output of armature core
1. Stationary part - Produces magnetic flux
Generator Nb = 2 ( wave winding )
2. Rotating part
FARADAY’S LAW OF ELECTROMAGNETIC INDUCTION - Armature responsible of converting mechanical energy into
electrical energy
“ Whenever a conductor cuts magnetic flux, dynamically it induces Sample Problems
an emf “ according to the formula TYPES OF ARMATURE WINDINGS
- Armature windings usually uses closed coil type than the open 1. A 4 pole, lap – wound dc armature, the back pitch is 17, if the
coil type. There are two types of closed coil type namely : winding is progressive what is the front pitch ?
a) 32 b) 15 *
1. Ring winding c) 17 d) 13
PNZ
E  =kN 2. Drum winding 2. A 4 pole dc generator with duplex lap winding has 48 slots and
60 a a) lap winding – ( for low voltage, high current generator ). The four element per slot. The flux per pole is 2.5 x 106 maxwells and
finish of each coil is connected to the start of it runs at 1,500 rpm. What is the output voltage ?
the next coil so the winding pitch or a) 60 volts * b) 360 volts
Comparison of emf formula: commutator pitch is unity or one. c) 225 volts d) 120 volts
3. A 4-pole wave wound dc generator has 50 slots and 24 conductors
yb  y f  2m
E2 N  per slot. The flux per pole is 10 mWb. Determine the induced emf in
= 2 2
E1 N1 1 the armature, it it is rotating at a speed of 600 rpm.
a) 240 V* b) 230 V c) 220 V d) 210 V
yb = back pitch ( should be an odd. no. )
yf = front pitch ( should be an odd. no. ) 4. A 4-pole, simplex lap wound, direct current armature has 48 slots
Where : E = generated or induced emf per parallel path + = if the winding is progressive containing 48 coils, each of 10 turns. The flux per pole in the field
E  K N  ( if P , Z and a is considered constants ) - = if the winding is retrogressive structure for this armature, is 500,000 lines. Calculate the speed for
this machine in order that its generated emf be 220 V.
P = Number of Poles a) 2,750 rpm* b) 2,550 rpm c) 2,250 rpm d) 2,000 rpm
Nb = P ( lap winding ) hint: z = 48 (10) (2) = 960 conductors multiply by two kay a = mP =
 = Flux per pole in Weber 8 so in every pole 2 parallel paths or two conductors per element
–8
( 1 Maxwell = 1 x 10 Wb ) Nb = Number of brushes 5. When a generator is being driven at 1,200 rpm, the generated emf
b) Electrical Efficiency P = No. of poles
s t s will be the generated emf iftthe field flux is
is 125 volts. What
Z = Total number of conductors
f low current generator ). decreased by 12% with the speed increased
f to 1,800 rpm?
% ee = =( PNumber of slots x no. of conductors per slot
o / PD ) x 100
b) wave winding – ( for high voltage, a) 135 V b) 145 V c) 155 V d) 165 V*
The finish of the coil is connected to the hint: φ2 = ( 1 – 0.2 ) φ1
N = Rotational
CLASSIFICATION or armature
OF COMPOUND speed in rpm
GENERATOR ACCORDING t start
s ofanother
f coil away from the first coil.  t   f  s
TO MAIN AND SERIES FIELD FLUX DIRECTION :
TYPES ACCORDING TO COMPOUNDING
1. Commulative Compound 2. Differential Compound
If the series field flux is aiding the main field flux If the series field flux is opposing the main field flux Over-compounded
FRANCISCAN ENGINEERING REVIEW PROGRAM ELECTRICAL
ELECTRICAL ENGINEERING
ENGINEERING - DC (MACHINES
- DC MACHINES GENERATOR / MOTOR) SEPTEMBER
SUMMER 2019 2020

a = Number of parallel paths in the armature

GENERATOR a = m P ( if simplex lap winding ) Z  2m y  yf
- A machine that converts the inter – action of mechanical energy a = 2 m ( if simplex wave winding ) y y b
and magnetic energy into electrical energy. P 2
- A dynmo is an example of simple generator . m = multiplicity
m = 1 ( if simplex ) , m = 2 ( if duplex )
y = Average pitch
Mech’l Elect’l
Magnetism PARTS OF A DC MACHINE ( GENERATOR ) Z = no. of winding elements on the surface
Input Output of armature core
1. Stationary part - Produces magnetic flux
Generator Nb = 2 ( wave winding )
2. Rotating part
FARADAY’S LAW OF ELECTROMAGNETIC INDUCTION - Armature responsible of converting mechanical energy into
electrical energy
“ Whenever a conductor cuts magnetic flux, dynamically it induces Sample Problems
an emf “ according to the formula TYPES OF ARMATURE WINDINGS
- Armature windings usually uses closed coil type than the open 1. A 4 pole, lap – wound dc armature, the back pitch is 17, if the
coil type. There are two types of closed coil type namely : winding is progressive what is the front pitch ?
a) 32 b) 15 *
1. Ring winding c) 17 d) 13
PNZ
E  =kN 2. Drum winding 2. A 4 pole dc generator with duplex lap winding has 48 slots and
60 a a) lap winding – ( for low voltage, high current generator ). The four element per slot. The flux per pole is 2.5 x 106 maxwells and
finish of each coil is connected to the start of it runs at 1,500 rpm. What is the output voltage ?
the next coil so the winding pitch or a) 60 volts * b) 360 volts
Comparison of emf formula: commutator pitch is unity or one. c) 225 volts d) 120 volts
3. A 4-pole wave wound dc generator has 50 slots and 24 conductors
yb  y f  2m
E2 N  per slot. The flux per pole is 10 mWb. Determine the induced emf in
= 2 2
E1 N1 1 the armature, it it is rotating at a speed of 600 rpm.
a) 240 V* b) 230 V c) 220 V d) 210 V
yb = back pitch ( should be an odd. no. )
yf = front pitch ( should be an odd. no. ) 4. A 4-pole, simplex lap wound, direct current armature has 48 slots
Where : E = generated or induced emf per parallel path + = if the winding is progressive containing 48 coils, each of 10 turns. The flux per pole in the field
E  K N  ( if P , Z and a is considered constants ) - = if the winding is retrogressive structure for this armature, is 500,000 lines. Calculate the speed for
this machine in order that its generated emf be 220 V.
P = Number of Poles a) 2,750 rpm* b) 2,550 rpm c) 2,250 rpm d) 2,000 rpm
Nb = P ( lap winding ) hint: z = 48 (10) (2) = 960 conductors multiply by two kay a = mP =
 = Flux per pole in Weber 8 so in every pole 2 parallel paths or two conductors per element
–8
( 1 Maxwell = 1 x 10 Wb ) Nb = Number of brushes 5. When a generator is being driven at 1,200 rpm, the generated emf
1. Over-Compounded P = No. of poles is The
125 full-load voltage
volts. What is less
will be than the no-load
the generated voltage
emf if the field which
flux is will
Z = Total number of conductors The full-load voltage is greater than the no-load voltage which result intoby
positive voltage regulation. Here,to
the voltage decreases
decreased 12% with the speed increased 1,800 rpm?
= Number of slots x no. of conductors per slot b) result
will waveinto
winding – ( for
negative high voltage,
voltage low Here,
regulation. current
thegenerator
voltage ). a)as load
135 V increases.
b) 145 V c) 155 V d) 165 V*
VNL Flat-compounded The finish of the coil is connected to the
increases as load increases. hint: φ2 = ( 1 – 0.2 ) φ1
N = Rotational or armature speed in rpm start of another coil away from the first coil. POWER LOSSES IN D.C. GENERATOR
2. Flat-Compounded
The full-load voltage is just equal to the no-load voltage which Total Power Loss = Copper loss + Iron loss + Mechanical loss
will result into a zero voltage regulation. Zero voltage regulation
Under-compounded is impossible to attain. Here, voltage is constant. Copper Loss = I2 R losses = losses due copper conductors
3. Under-Compounded
FRANCISCAN ENGINEERING REVIEW PROGRAM ELECTRICAL
ELECTRICAL ENGINEERING
ENGINEERING - DC (MACHINES
- DC MACHINES GENERATOR / MOTOR) SEPTEMBER
SUMMER 2019 2020

a = Number of parallel paths in the armature

GENERATOR a = m P ( if simplex lap winding ) Z  2m y  yf
- A machine that converts the inter – action of mechanical energy a = 2 m ( if simplex wave winding ) y y b
and magnetic energy into electrical energy. P 2
- A dynmo is an example of simple generator . m = multiplicity
m = 1 ( if simplex ) , m = 2 ( if duplex )
y = Average pitch
Mech’l Elect’l
Magnetism PARTS OF A DC MACHINE ( GENERATOR ) Z = no. of winding elements on the surface
Input Output of armature core
1. Stationary part - Produces magnetic flux
Generator Nb = 2 ( wave winding )
2. Rotating part
FARADAY’S LAW OF ELECTROMAGNETIC INDUCTION - Armature responsible of converting mechanical energy into
electrical energy
“ Whenever a conductor cuts magnetic flux, dynamically it induces Sample Problems
an emf “ according to the formula TYPES OF ARMATURE WINDINGS
- Armature windings usually uses closed coil type than the open 1. A 4 pole, lap – wound dc armature, the back pitch is 17, if the
coil type. There are two types of closed coil type namely : winding is progressive what is the front pitch ?
a) 32 b) 15 *
1. Ring winding c) 17 d) 13
PNZ
E  =kN 2. Drum winding 2. A 4 pole dc generator with duplex lap winding has 48 slots and
60 a a) lap winding – ( for low voltage, high current generator ). The four element per slot. The flux per pole is 2.5 x 106 maxwells and
finish of each coil is connected to the start of it runs at 1,500 rpm. What is the output voltage ?
the next coil so the winding pitch or a) 60 volts * b) 360 volts
Comparison of emf formula: commutator pitch is unity or one. c) 225 volts d) 120 volts
3. A 4-pole wave wound dc generator has 50 slots and 24 conductors
yb  y f  2m
E2 N  per slot. The flux per pole is 10 mWb. Determine the induced emf in
= 2 2
E1 N1 1 the armature, it it is rotating at a speed of 600 rpm.
a) 240 V* b) 230 V c) 220 V d) 210 V
yb = back pitch ( should be an odd. no. )
yf = front pitch ( should be an odd. no. ) 4. A 4-pole, simplex lap wound, direct current armature has 48 slots
Where : E = generated or induced emf per parallel path + = if the winding is progressive containing 48 coils, each of 10 turns. The flux per pole in the field
E  K N  ( if P , Z and a is considered constants ) - = if the winding is retrogressive structure for this armature, is 500,000 lines. Calculate the speed for
this machine in order that its generated emf be 220 V.
P = Number of Poles a) 2,750 rpm* b) 2,550 rpm c) 2,250 rpm d) 2,000 rpm
Nb = P ( lap winding ) hint: z = 48 (10) (2) = 960 conductors multiply by two kay a = mP =
 = Flux per pole in Weber 8 so in every pole 2 parallel paths or two conductors per element
–8
( 1 Maxwell = 1 x 10 Wb ) Nb = Number of brushes 5. When a generator is being driven at 1,200 rpm, the generated emf
Mechanical Loss = friction, windage and miscellaneous loss P = No. when
1. A separately excited generator, of poles
running at 1000 rpm 3. A
is 50
125kW, 500What
volts. voltswill
short
be shunt generatoremf
the generated hasif an
thearmature
field flux is
Z = Total number of conductors supplied 200 A at 125 V. What will be the load current when resistance, series
decreased by 12%field
withresistance
the speedand shunt field
increased resistance
to 1,800 rpm? of
Core and Iron Loss = Number of slots
= constant loss,x heat
no. ofloss
conductors per slotin the
due to heating theb)speed
wave winding
drops – ( rpm.
to 800 for high voltage,
Assume low current generator ).
armature 0.05 ohms,
a) 135 V 0.06b)ohms 145 Vand 253 ohms respectively.
c) 155 V What
d) 165is V*
the
core due to hysteresis and eddy current. resistance = 0.04 ohm and Thebrush
finish drop
of the= coil
2 V is ans.
connected to the
I2 = 159.4 A armature
hint: φ2 = power generated
( 1 – 0.2 ) φ1 ?
N = Rotational or armature speed in rpm start of another coil away from the first coil. a) 58.28 kW b) 48.74 kW
Physteresis = kh N ɸ ; Peddy = ke N2 ɸ2 ; Pcore = Physteresis + Peddy 2. The output of a shunt generator is 24 kW at a terminal voltage c) 51.76 kW * d) 52.13 kW
of 200 V. Armature resistance 0.05 ohm, shunt field resistance
4. ( Bd. Exam Sept. 2003 )
of 40 ohms. If the iron and friction losses equal to the copper loss
The pulley of an old generator set has a diameter of 20 inches.
SAMPLE PROBLEMS at this load., Find the overall efficiency. Ans. 87.07%
The belt exerts a pull of 353 lbs. on the pulley and the gen.-set
FRANCISCAN ENGINEERING REVIEW PROGRAM ELECTRICAL
ELECTRICAL ENGINEERING
ENGINEERING - DC (MACHINES
- DC MACHINES GENERATOR / MOTOR) SEPTEMBER
SUMMER 2019 2020

a = Number of parallel paths in the armature

GENERATOR a = m P ( if simplex lap winding ) Z  2m y  yf
- A machine that converts the inter – action of mechanical energy a = 2 m ( if simplex wave winding ) y y b
and magnetic energy into electrical energy. P 2
- A dynmo is an example of simple generator . m = multiplicity
m = 1 ( if simplex ) , m = 2 ( if duplex )
y = Average pitch
Mech’l Elect’l
Magnetism PARTS OF A DC MACHINE ( GENERATOR ) Z = no. of winding elements on the surface
Input Output of armature core
1. Stationary part - Produces magnetic flux
Generator Nb = 2 ( wave winding )
2. Rotating part
FARADAY’S LAW OF ELECTROMAGNETIC INDUCTION - Armature responsible of converting mechanical energy into
electrical energy
“ Whenever a conductor cuts magnetic flux, dynamically it induces Sample Problems
an emf “ according to the formula TYPES OF ARMATURE WINDINGS
- Armature windings usually uses closed coil type than the open 1. A 4 pole, lap – wound dc armature, the back pitch is 17, if the
coil type. There are two types of closed coil type namely : winding is progressive what is the front pitch ?
a) 32 b) 15 *
1. Ring winding c) 17 d) 13
PNZ
E  =kN 2. Drum winding 2. A 4 pole dc generator with duplex lap winding has 48 slots and
60 a a) lap winding – ( for low voltage, high current generator ). The four element per slot. The flux per pole is 2.5 x 106 maxwells and
finish of each coil is connected to the start of it runs at 1,500 rpm. What is the output voltage ?
the next coil so the winding pitch or a) 60 volts * b) 360 volts
Comparison of emf formula: commutator pitch is unity or one. c) 225 volts d) 120 volts
3. A 4-pole wave wound dc generator has 50 slots and 24 conductors
yb  y f  2m
E2 N  per slot. The flux per pole is 10 mWb. Determine the induced emf in
= 2 2
E1 N1 1 the armature, it it is rotating at a speed of 600 rpm.
a) 240 V* b) 230 V c) 220 V d) 210 V
yb = back pitch ( should be an odd. no. )
yf = front pitch ( should be an odd. no. ) 4. A 4-pole, simplex lap wound, direct current armature has 48 slots
Where : E = generated or induced emf per parallel path + = if the winding is progressive containing 48 coils, each of 10 turns. The flux per pole in the field
E  K N  ( if P , Z and a is considered constants ) - = if the winding is retrogressive structure for this armature, is 500,000 lines. Calculate the speed for
this machine in order that its generated emf be 220 V.
P = Number of Poles a) 2,750 rpm* b) 2,550 rpm c) 2,250 rpm d) 2,000 rpm
Nb = P ( lap winding ) hint: z = 48 (10) (2) = 960 conductors multiply by two kay a = mP =
 = Flux per pole in Weber 8 so in every pole 2 parallel paths or two conductors per element
–8
( 1 Maxwell = 1 x 10 Wb ) Nb = Number of brushes 5. When a generator is being driven at 1,200 rpm, the generated emf
runs at 900 rpm. What is the approximate kilowatt rating of the will cause additionalPlosses.
= No. of poles If External Magnitude
is 125 volts. arebegiven
What will If internal
the generated emfmagnitudes areisgiven
if the field flux
generatorZset =
? Total number of conductors decreased by 12% with the speed increased to 1,800 rpm?
a) 255 = Number of slots xb)no.75.5
of conductors per slot 2. b) voltages
The wave winding – be
should ( foridentical
high voltage,
so thatlow current
each generator
machine will ). a) 135 V b) 145 V c) 155 V d) 165 V*
c) 200 d) 37.5 contribute. Otherwise The finish of thewill
the generators coilnot
is connected to the
share the load hint: φ2 = ( 1 – 0.2 ) φ1
N = Rotational or armature speed in rpm properly. start of another coil away from the first coil.
IA IB
A
GENERATOR PARALLEL OPERATION CONDITIONS 3. Prime movers should have similar and stable rotational speed
characteristics L
A Ix L Iy B
1. The polarities of both generators must be the same
otherwise, current will circulate through the two machines that
B
FRANCISCAN ENGINEERING REVIEW PROGRAM ELECTRICAL
ELECTRICAL ENGINEERING
ENGINEERING - DC (MACHINES
- DC MACHINES GENERATOR / MOTOR) SEPTEMBER
SUMMER 2019 2020

a = Number of parallel paths in the armature

GENERATOR a = m P ( if simplex lap winding ) Z  2m y  yf
- A machine that converts the inter – action of mechanical energy a = 2 m ( if simplex wave winding ) y y b
and magnetic energy into electrical energy. P 2
- A dynmo is an example of simple generator . m = multiplicity
m = 1 ( if simplex ) , m = 2 ( if duplex )
y = Average pitch
Mech’l Elect’l
Magnetism PARTS OF A DC MACHINE ( GENERATOR ) Z = no. of winding elements on the surface
Input Output of armature core
1. Stationary part - Produces magnetic flux
Generator Nb = 2 ( wave winding )
2. Rotating part
FARADAY’S LAW OF ELECTROMAGNETIC INDUCTION - Armature responsible of converting mechanical energy into
electrical energy
“ Whenever a conductor cuts magnetic flux, dynamically it induces Sample Problems
an emf “ according to the formula TYPES OF ARMATURE WINDINGS
- Armature windings usually uses closed coil type than the open 1. A 4 pole, lap – wound dc armature, the back pitch is 17, if the
coil type. There are two types of closed coil type namely : winding is progressive what is the front pitch ?
a) 32 b) 15 *
1. Ring winding c) 17 d) 13
PNZ
E  =kN 2. Drum winding 2. A 4 pole dc generator with duplex lap winding has 48 slots and
60 a a) lap winding – ( for low voltage, high current generator ). The four element per slot. The flux per pole is 2.5 x 106 maxwells and
finish of each coil is connected to the start of it runs at 1,500 rpm. What is the output voltage ?
the next coil so the winding pitch or a) 60 volts * b) 360 volts
Comparison of emf formula: commutator pitch is unity or one. c) 225 volts d) 120 volts
3. A 4-pole wave wound dc generator has 50 slots and 24 conductors
yb  y f  2m
E2 N  per slot. The flux per pole is 10 mWb. Determine the induced emf in
= 2 2
E1 N1 1 the armature, it it is rotating at a speed of 600 rpm.
a) 240 V* b) 230 V c) 220 V d) 210 V
yb = back pitch ( should be an odd. no. )
yf = front pitch ( should be an odd. no. ) 4. A 4-pole, simplex lap wound, direct current armature has 48 slots
Where : E = generated or induced emf per parallel path + = if the winding is progressive containing 48 coils, each of 10 turns. The flux per pole in the field
E  K N  ( if P , Z and a is considered constants ) - = if the winding is retrogressive structure for this armature, is 500,000 lines. Calculate the speed for
this machine in order that its generated emf be 220 V.
P = Number of Poles a) 2,750 rpm* b) 2,550 rpm c) 2,250 rpm d) 2,000 rpm
Nb = P ( lap winding ) hint: z = 48 (10) (2) = 960 conductors multiply by two kay a = mP =
 = Flux per pole in Weber 8 so in every pole 2 parallel paths or two conductors per element
–8
( 1 Maxwell = 1 x 10 Wb ) Nb = Number of brushes 5. When a generator is being driven at 1,200 rpm, the generated emf
a) 231 kW and 369 P kW= No. ofb)poles 242 kW and 358 kW c)125
is 231volts.
voltsWhat
* d) 315emf
will be the generated volts
if the field flux is
Z = Total number of conductors c) 238 kW and 362 kW d) 234 kW and 366 kW decreased by 12% with the speed increased to 1,800 rpm?
= Number of slots x no. of conductors per slot b) wave winding – ( for high voltage, low current generator ). SAMPLE PROBLEMS
a) 135 V b) 145DCV GENERATORc) 155 V d) 165 V*
2. Two shunt generators AThe andfinish of the coil
B operates is connected
in parallel to the
and their load hint: φ2 = ( 1 – 0.2 ) φ1
N = Rotational or armature speed in rpm
SAMPLE PROBLEMS characteristics may be start
takenofasanother
straightcoil away
line. Thefrom the of
voltage first coil. 1. A conductor 0.5 meter long is moved at right angles to a uniform
generator A fall from 240 volts at no-load to 220 volts at 200 magnetic field strength of 1,200 gauss at a speed of 0.2 meter per
1. Two shunt generators A and B, with ratings of 250 and 400 kW Amperes while that of B falls from 245 volts at no-load to 220 second. Find the value of the emf generated. 0.012 volts
respectively having equal no – load voltage of 260 volts and full- volts at 150 Amperes. Determine the common terminal voltage
load voltage of 240 volts, calculate the load of each when the when the load is 67 kW.
total output is 600 kW. a) 320 volts b) 241 volts
FRANCISCAN ENGINEERING REVIEW PROGRAM ELECTRICAL
ELECTRICAL ENGINEERING
ENGINEERING - DC (MACHINES
- DC MACHINES GENERATOR / MOTOR) SEPTEMBER
SUMMER 2019 2020

a = Number of parallel paths in the armature

GENERATOR a = m P ( if simplex lap winding ) Z  2m y  yf
- A machine that converts the inter – action of mechanical energy a = 2 m ( if simplex wave winding ) y y b
and magnetic energy into electrical energy. P 2
- A dynmo is an example of simple generator . m = multiplicity
m = 1 ( if simplex ) , m = 2 ( if duplex )
y = Average pitch
Mech’l Elect’l
Magnetism PARTS OF A DC MACHINE ( GENERATOR ) Z = no. of winding elements on the surface
Input Output of armature core
1. Stationary part - Produces magnetic flux
Generator Nb = 2 ( wave winding )
2. Rotating part
FARADAY’S LAW OF ELECTROMAGNETIC INDUCTION - Armature responsible of converting mechanical energy into
electrical energy
“ Whenever a conductor cuts magnetic flux, dynamically it induces Sample Problems
an emf “ according to the formula TYPES OF ARMATURE WINDINGS
- Armature windings usually uses closed coil type than the open 1. A 4 pole, lap – wound dc armature, the back pitch is 17, if the
coil type. There are two types of closed coil type namely : winding is progressive what is the front pitch ?
a) 32 b) 15 *
1. Ring winding c) 17 d) 13
PNZ
E  =kN 2. Drum winding 2. A 4 pole dc generator with duplex lap winding has 48 slots and
60 a a) lap winding – ( for low voltage, high current generator ). The four element per slot. The flux per pole is 2.5 x 106 maxwells and
finish of each coil is connected to the start of it runs at 1,500 rpm. What is the output voltage ?
the next coil so the winding pitch or a) 60 volts * b) 360 volts
Comparison of emf formula: commutator pitch is unity or one. c) 225 volts d) 120 volts
3. A 4-pole wave wound dc generator has 50 slots and 24 conductors
yb  y f  2m
E2 N  per slot. The flux per pole is 10 mWb. Determine the induced emf in
= 2 2
E1 N1 1 the armature, it it is rotating at a speed of 600 rpm.
a) 240 V* b) 230 V c) 220 V d) 210 V
yb = back pitch ( should be an odd. no. )
yf = front pitch ( should be an odd. no. ) 4. A 4-pole, simplex lap wound, direct current armature has 48 slots
Where : E = generated or induced emf per parallel path + = if the winding is progressive containing 48 coils, each of 10 turns. The flux per pole in the field
E  K N  ( if P , Z and a is considered constants ) - = if the winding is retrogressive structure for this armature, is 500,000 lines. Calculate the speed for
this machine in order that its generated emf be 220 V.
P = Number of Poles a) 2,750 rpm* b) 2,550 rpm c) 2,250 rpm d) 2,000 rpm
Nb = P ( lap winding ) hint: z = 48 (10) (2) = 960 conductors multiply by two kay a = mP =
 = Flux per pole in Weber 8 so in every pole 2 parallel paths or two conductors per element
–8
( 1 Maxwell = 1 x 10 Wb ) Nb = Number of brushes 5. When a generator is being driven at 1,200 rpm, the generated emf
2. What is the average voltage generated in a single conductor of a 4. A six pole, wave wound P = No. of poles
armature has 640 conductors. If the flux is 125 volts. What will be the generated emf if the field flux is
four pole dc Zgenerator
= Total number
if the of conductors
effective flux per pole is 2.8 mWb and per pole is 16 mWb, at what speed must the armature be driven in 6. decreased
A 10-pole by40012%
kW,with 250the
V dc generator
speed has atolap
increased wound
1,800 armature
rpm?
= Number of slots
the speed of the armature is 1,800 rpm x no.?of conductors0.34
per slot
volts orderb)to generate
wave winding – ( for high voltage,
256 volts.? 500 rpmlow current generator ). with
a)75
135slots
V each b) having
145 V12 conductors. The
c) 155 V cross section of V*
d) 165 each
The finish of the coil is connected to the conductor
hint: φ2 is
= 35
( 1 mm
2
– 0.2. If) φ
the average length of one turn is 150 cm,
1
N = at
3. A wire moving Rotational
a speed or of armature speed
18.6 meters per in rpm passes
second 5. A four pole generator hasstart384
of another coil away
conductors from theof
each capable first coil. determine the power wasted in the armature. Assume the resistivity of
through a magnetic field whose magnetic flux density is 2 Tesla. Find carrying 30 Amp of current without over heating. The emf generated copper to be 2 micro ohm – cm. 9874 Watts
the length of the wire if it cuts an average of 2.8 Webers of flux in 0.5 in each conductor is 3 volts. Neglecting internal voltage drop in the
seconds. 0.075 meter. generator, calculate the total generated emf and the maximum kW 7. A two pole dc generator has an armature containing a total of 40
output of the generator if the armature were conductors in two parallel paths. The flux per pole is 6.48 x 108
a) wave connected b) lap connected maxwells and the speed of the prime mover is 2 revolutions per
FRANCISCAN ENGINEERING REVIEW PROGRAM ELECTRICAL
ELECTRICAL ENGINEERING
ENGINEERING - DC (MACHINES
- DC MACHINES GENERATOR / MOTOR) SEPTEMBER
SUMMER 2019 2020

a = Number of parallel paths in the armature

GENERATOR a = m P ( if simplex lap winding ) Z  2m y  yf
- A machine that converts the inter – action of mechanical energy a = 2 m ( if simplex wave winding ) y y b
and magnetic energy into electrical energy. P 2
- A dynmo is an example of simple generator . m = multiplicity
m = 1 ( if simplex ) , m = 2 ( if duplex )
y = Average pitch
Mech’l Elect’l
Magnetism PARTS OF A DC MACHINE ( GENERATOR ) Z = no. of winding elements on the surface
Input Output of armature core
1. Stationary part - Produces magnetic flux
Generator Nb = 2 ( wave winding )
2. Rotating part
FARADAY’S LAW OF ELECTROMAGNETIC INDUCTION - Armature responsible of converting mechanical energy into
electrical energy
“ Whenever a conductor cuts magnetic flux, dynamically it induces Sample Problems
an emf “ according to the formula TYPES OF ARMATURE WINDINGS
- Armature windings usually uses closed coil type than the open 1. A 4 pole, lap – wound dc armature, the back pitch is 17, if the
coil type. There are two types of closed coil type namely : winding is progressive what is the front pitch ?
a) 32 b) 15 *
1. Ring winding c) 17 d) 13
PNZ
E  =kN 2. Drum winding 2. A 4 pole dc generator with duplex lap winding has 48 slots and
60 a a) lap winding – ( for low voltage, high current generator ). The four element per slot. The flux per pole is 2.5 x 106 maxwells and
finish of each coil is connected to the start of it runs at 1,500 rpm. What is the output voltage ?
the next coil so the winding pitch or a) 60 volts * b) 360 volts
Comparison of emf formula: commutator pitch is unity or one. c) 225 volts d) 120 volts
3. A 4-pole wave wound dc generator has 50 slots and 24 conductors
yb  y f  2m
E2 N  per slot. The flux per pole is 10 mWb. Determine the induced emf in
= 2 2
E1 N1 1 the armature, it it is rotating at a speed of 600 rpm.
a) 240 V* b) 230 V c) 220 V d) 210 V
yb = back pitch ( should be an odd. no. )
yf = front pitch ( should be an odd. no. ) 4. A 4-pole, simplex lap wound, direct current armature has 48 slots
Where : E = generated or induced emf per parallel path + = if the winding is progressive containing 48 coils, each of 10 turns. The flux per pole in the field
E  K N  ( if P , Z and a is considered constants ) - = if the winding is retrogressive structure for this armature, is 500,000 lines. Calculate the speed for
this machine in order that its generated emf be 220 V.
P = Number of Poles a) 2,750 rpm* b) 2,550 rpm c) 2,250 rpm d) 2,000 rpm
Nb = P ( lap winding ) hint: z = 48 (10) (2) = 960 conductors multiply by two kay a = mP =
 = Flux per pole in Weber 8 so in every pole 2 parallel paths or two conductors per element
–8
( 1 Maxwell = 1 x 10 Wb ) Nb = Number of brushes 5. When a generator is being driven at 1,200 rpm, the generated emf
second. The resistance of each conductor is 0.025 ohms. Calculate P =ofNo.
generator delivers a current 40 of
A poles
at 100 Volts to tis load what is is 125 volts. What will be the generated emf if the field flux is
the terminal Zvoltage
= Total number
of the of conductors
generator when each of the conductors is the efficiency ? 3. decreased
Determinebythe
12%terminal voltage
with the speedofincreased
a generator whichrpm?
to 1,800 develops an
= Number
carrying a current of 12 Amp. of slots x no. volts
512.4 of conductors per slot b) wave winding – ( for high voltage,
a) 96.54% b) 97.30%low current generator ). emfa)of135
240V V and has an Varmature current
b) 145 c) 155 of
V 50A on load. Assume
d) 165 V* the
c) 97.65% The finish d)
of 95.15%
the coil is connected to the armature
hint: φ2resistance
= ( 1 – 0.2is)40
φ1 milliohms.
8. N = Rotational or armature speed in rpm start of another coil away from the first coil. a) 215 V b) 125 V
2. A generator assembled with six pole shoes and six interpoles c) 238 V d) 218 V
PRACTICE PROBLEMS DC GENERATOR when driven to a speed of 1,800 rpm should generate a frequency of
_________ Hertz. 4. What is the average voltage generated across a 2 meter conductor
1. The armature of a separately excited shunt generator has 0.05 a) 90 b) 50 if it is moved in parallel to a uniform magnetic field with a density of 2.8
ohms effective resistance and a brush resistance of 0.02 ohm. If this c) 60 d) 180 Tesla at a speed of 0.4 meters per second ?
FRANCISCAN ENGINEERING REVIEW PROGRAM ELECTRICAL
ELECTRICAL ENGINEERING
ENGINEERING - DC (MACHINES
- DC MACHINES GENERATOR / MOTOR) SEPTEMBER
SUMMER 2019 2020

a = Number of parallel paths in the armature

GENERATOR a = m P ( if simplex lap winding ) Z  2m y  yf
- A machine that converts the inter – action of mechanical energy a = 2 m ( if simplex wave winding ) y y b
and magnetic energy into electrical energy. P 2
- A dynmo is an example of simple generator . m = multiplicity
m = 1 ( if simplex ) , m = 2 ( if duplex )
y = Average pitch
Mech’l Elect’l
Magnetism PARTS OF A DC MACHINE ( GENERATOR ) Z = no. of winding elements on the surface
Input Output of armature core
1. Stationary part - Produces magnetic flux
Generator Nb = 2 ( wave winding )
2. Rotating part
FARADAY’S LAW OF ELECTROMAGNETIC INDUCTION - Armature responsible of converting mechanical energy into
electrical energy
“ Whenever a conductor cuts magnetic flux, dynamically it induces Sample Problems
an emf “ according to the formula TYPES OF ARMATURE WINDINGS
- Armature windings usually uses closed coil type than the open 1. A 4 pole, lap – wound dc armature, the back pitch is 17, if the
coil type. There are two types of closed coil type namely : winding is progressive what is the front pitch ?
a) 32 b) 15 *
1. Ring winding c) 17 d) 13
PNZ
E  =kN 2. Drum winding 2. A 4 pole dc generator with duplex lap winding has 48 slots and
60 a a) lap winding – ( for low voltage, high current generator ). The four element per slot. The flux per pole is 2.5 x 106 maxwells and
finish of each coil is connected to the start of it runs at 1,500 rpm. What is the output voltage ?
the next coil so the winding pitch or a) 60 volts * b) 360 volts
Comparison of emf formula: commutator pitch is unity or one. c) 225 volts d) 120 volts
3. A 4-pole wave wound dc generator has 50 slots and 24 conductors
yb  y f  2m
E2 N  per slot. The flux per pole is 10 mWb. Determine the induced emf in
= 2 2
E1 N1 1 the armature, it it is rotating at a speed of 600 rpm.
a) 240 V* b) 230 V c) 220 V d) 210 V
yb = back pitch ( should be an odd. no. )
yf = front pitch ( should be an odd. no. ) 4. A 4-pole, simplex lap wound, direct current armature has 48 slots
Where : E = generated or induced emf per parallel path + = if the winding is progressive containing 48 coils, each of 10 turns. The flux per pole in the field
E  K N  ( if P , Z and a is considered constants ) - = if the winding is retrogressive structure for this armature, is 500,000 lines. Calculate the speed for
this machine in order that its generated emf be 220 V.
P = Number of Poles a) 2,750 rpm* b) 2,550 rpm c) 2,250 rpm d) 2,000 rpm
Nb = P ( lap winding ) hint: z = 48 (10) (2) = 960 conductors multiply by two kay a = mP =
 = Flux per pole in Weber 8 so in every pole 2 parallel paths or two conductors per element
–8
( 1 Maxwell = 1 x 10 Wb ) Nb = Number of brushes 5. When a generator is being driven at 1,200 rpm, the generated emf
-8
a) 2.24 x 10 volt b) 2.24 volts c) 4450 W P = No. ofd)poles
5153 W 7. isA125
generator is connected
volts. What togenerated
will be the a 50 ohmsemfload andfield
if the a current
flux is of 10 A
c) 0 volt Z = Total number of conductors
d) 7 volts flows. If the armature resistance is 0.5 ohms, determine the terminal
decreased by 12% with the speed increased to 1,800 rpm?
= Number of slots x no. of conductors per slot 6. Ab)fourwave
polewinding – ( for high
shunt generator voltage,
with low current
lap connected generator
armature ).
having voltage.
a) 135 V b) 145 V c) 155 V d) 165 V*
5. A four pole dc shunt generator with a shunt filed resistance of 100 The finish of
field and armature resistances of the
50coil is connected
ohms and 0.1to the
ohms a) 455
hint:Vφ2 = ( 1 – 0.2 ) φ1 b) 505 V
ohms and an N armature
= Rotational or armature
resistance of 1 ohm speed
has in rpm
378 wave connected start
respectively supplied sixty 100of volt
another
40 coil
wattaway from
lamps. the first coil.
Calculate the c) 500 V d) 510 V
conductors in its armature. The flux per pole is 0.02 Wb. If a load generated emf.
resistance of 10 ohms is connected across the armature terminals a) 128.5 V b) 212.8 V 8. A separately excited generator develops a no-load emf of 180 V at
and the generator is driven at 1000 rpm, calculate the power c) 104.6 V d) 145.5 V an armature speed of 15 rev/sec. and a flux per pole of 0.20 Wb.
absorbed by the load. Calculate the generated emf when the speed remains at 15 rev/sec.
a) 8215 W b) 1278 W and the pole flux is decreased to 0.125 Wb.
FRANCISCAN ENGINEERING REVIEW PROGRAM ELECTRICAL
ELECTRICAL ENGINEERING
ENGINEERING - DC (MACHINES
- DC MACHINES GENERATOR / MOTOR) SEPTEMBER
SUMMER 2019 2020

a = Number of parallel paths in the armature

GENERATOR a = m P ( if simplex lap winding ) Z  2m y  yf
- A machine that converts the inter – action of mechanical energy a = 2 m ( if simplex wave winding ) y y b
and magnetic energy into electrical energy. P 2
- A dynmo is an example of simple generator . m = multiplicity
m = 1 ( if simplex ) , m = 2 ( if duplex )
y = Average pitch
Mech’l Elect’l
Magnetism PARTS OF A DC MACHINE ( GENERATOR ) Z = no. of winding elements on the surface
Input Output of armature core
1. Stationary part - Produces magnetic flux
Generator Nb = 2 ( wave winding )
2. Rotating part
FARADAY’S LAW OF ELECTROMAGNETIC INDUCTION - Armature responsible of converting mechanical energy into
electrical energy
“ Whenever a conductor cuts magnetic flux, dynamically it induces Sample Problems
an emf “ according to the formula TYPES OF ARMATURE WINDINGS
- Armature windings usually uses closed coil type than the open 1. A 4 pole, lap – wound dc armature, the back pitch is 17, if the
coil type. There are two types of closed coil type namely : winding is progressive what is the front pitch ?
a) 32 b) 15 *
1. Ring winding c) 17 d) 13
PNZ
E  =kN 2. Drum winding 2. A 4 pole dc generator with duplex lap winding has 48 slots and
60 a a) lap winding – ( for low voltage, high current generator ). The four element per slot. The flux per pole is 2.5 x 106 maxwells and
finish of each coil is connected to the start of it runs at 1,500 rpm. What is the output voltage ?
the next coil so the winding pitch or a) 60 volts * b) 360 volts
Comparison of emf formula: commutator pitch is unity or one. c) 225 volts d) 120 volts
3. A 4-pole wave wound dc generator has 50 slots and 24 conductors
yb  y f  2m
E2 N  per slot. The flux per pole is 10 mWb. Determine the induced emf in
= 2 2
E1 N1 1 the armature, it it is rotating at a speed of 600 rpm.
a) 240 V* b) 230 V c) 220 V d) 210 V
yb = back pitch ( should be an odd. no. )
yf = front pitch ( should be an odd. no. ) 4. A 4-pole, simplex lap wound, direct current armature has 48 slots
Where : E = generated or induced emf per parallel path + = if the winding is progressive containing 48 coils, each of 10 turns. The flux per pole in the field
E  K N  ( if P , Z and a is considered constants ) - = if the winding is retrogressive structure for this armature, is 500,000 lines. Calculate the speed for
this machine in order that its generated emf be 220 V.
P = Number of Poles a) 2,750 rpm* b) 2,550 rpm c) 2,250 rpm d) 2,000 rpm
Nb = P ( lap winding ) hint: z = 48 (10) (2) = 960 conductors multiply by two kay a = mP =
 = Flux per pole in Weber 8 so in every pole 2 parallel paths or two conductors per element
–8
( 1 Maxwell = 1 x 10 Wb ) Nb = Number of brushes 5. When a generator is being driven at 1,200 rpm, the generated emf
a) 112.5 V b) 244.2 V 10.A six-pole lap wound P =dcNo.generator
of poles has 144 slots with 4 0.004 ohms
is 125 resistance.
volts. What willCalculate the terminal
be the generated emf voltage when
if the field fluxrunning
is at
c) 275.4 V Z = Total number of conductors
d) 125.8 V conductors per slot. The effective flux between each pole face is 36 900decreased
rpm if the by
armature current
12% with is 50 A.
the speed increased to 1,800 rpm?
= Number of slots x no. of conductors per slot mW.b) wave
If the winding
armature – ( for
of this high voltage,
machine lowbycurrent
is driven generator
its prime mover to ). a a) 458 V V b)
a) 135 b) 145 V c) 384
155 V
V d) 165 V*
9. A dc generator has a generated emf of 210 V when running at speed of 1,400 rpm, howThe finishvoltage
much of the coil is connected
is generated in to
a the
single c) 540
hint:Vφ2 = ( 1 – 0.2 ) φ1 d) 440 V
700 rpm andN the= flux
Rotational
per poleorisarmature
120 mWb. speed in rpm the generated
Determine conductor in the armature start
? of another coil away from the first coil.
emf at a speed of 1155 rpm and a flux of 132 mWb. a) 1.32 V b) 0.84 V 12.A dc generator running at 25 rev/sec. generates an emf of 150 V.
a) 318.2 V b) 381.2 V c) 0.55 V d) 1.72 V Determine the percentage increase in the flux per pole required to
c) 328.1 V d) 342.6 V generate 180 V at 20 rev/sec.
11.A four pole lap wound dc shunt generator has a useful flux per a) 20% b) 60%
pole of 0.07 Wb. The armature winding consists of 220 turns each of c) 25% d) 50%
FRANCISCAN ENGINEERING REVIEW PROGRAM ELECTRICAL
ELECTRICAL ENGINEERING
ENGINEERING - DC (MACHINES
- DC MACHINES GENERATOR / MOTOR) SEPTEMBER
SUMMER 2019 2020

a = Number of parallel paths in the armature

GENERATOR a = m P ( if simplex lap winding ) Z  2m y  yf
- A machine that converts the inter – action of mechanical energy a = 2 m ( if simplex wave winding ) y y b
and magnetic energy into electrical energy. P 2
- A dynmo is an example of simple generator . m = multiplicity
m = 1 ( if simplex ) , m = 2 ( if duplex )
y = Average pitch
Mech’l Elect’l
Magnetism PARTS OF A DC MACHINE ( GENERATOR ) Z = no. of winding elements on the surface
Input Output of armature core
1. Stationary part - Produces magnetic flux
Generator Nb = 2 ( wave winding )
2. Rotating part
FARADAY’S LAW OF ELECTROMAGNETIC INDUCTION - Armature responsible of converting mechanical energy into
electrical energy
“ Whenever a conductor cuts magnetic flux, dynamically it induces Sample Problems
an emf “ according to the formula TYPES OF ARMATURE WINDINGS
- Armature windings usually uses closed coil type than the open 1. A 4 pole, lap – wound dc armature, the back pitch is 17, if the
coil type. There are two types of closed coil type namely : winding is progressive what is the front pitch ?
a) 32 b) 15 *
1. Ring winding c) 17 d) 13
PNZ
E  =kN 2. Drum winding 2. A 4 pole dc generator with duplex lap winding has 48 slots and
60 a a) lap winding – ( for low voltage, high current generator ). The four element per slot. The flux per pole is 2.5 x 106 maxwells and
finish of each coil is connected to the start of it runs at 1,500 rpm. What is the output voltage ?
the next coil so the winding pitch or a) 60 volts * b) 360 volts
Comparison of emf formula: commutator pitch is unity or one. c) 225 volts d) 120 volts
3. A 4-pole wave wound dc generator has 50 slots and 24 conductors
yb  y f  2m
E2 N  per slot. The flux per pole is 10 mWb. Determine the induced emf in
= 2 2
E1 N1 1 the armature, it it is rotating at a speed of 600 rpm.
a) 240 V* b) 230 V c) 220 V d) 210 V
yb = back pitch ( should be an odd. no. )
yf = front pitch ( should be an odd. no. ) 4. A 4-pole, simplex lap wound, direct current armature has 48 slots
Where : E = generated or induced emf per parallel path + = if the winding is progressive containing 48 coils, each of 10 turns. The flux per pole in the field
E  K N  ( if P , Z and a is considered constants ) - = if the winding is retrogressive structure for this armature, is 500,000 lines. Calculate the speed for
this machine in order that its generated emf be 220 V.
P = Number of Poles a) 2,750 rpm* b) 2,550 rpm c) 2,250 rpm d) 2,000 rpm
Nb = P ( lap winding ) hint: z = 48 (10) (2) = 960 conductors multiply by two kay a = mP =
 = Flux per pole in Weber 8 so in every pole 2 parallel paths or two conductors per element
–8
( 1 Maxwell = 1 x 10 Wb ) Nb = Number of brushes 5. When a generator is being driven at 1,200 rpm, the generated emf
P = No.
14.A shunt generator delivers 50 Aofof
poles
current to a load at 110 V, at is 125 volts. What will be the generated emf if the field flux is
Z = Total
13.Two permanent number with
magnets of conductors
a circular corss-section are an efficiency of 35 %. The total constant losses are 480 W, and the 16.A four pole shuntwith
connected
decreased by 12% the speedgenerator
increased has a lap
to 1,800 rpm?connected
mounted in a position such that thexN-pole
= Number of slots no. of conductors
of one facesper
theslot
S-pole of shuntb)field
wave windingis–65
resistance ( for highCalculate
ohms. voltage, low
the current generator
armature ).
resistance. armature
a) 135 Vwith 728b)conductors.
145 V Thec)flux
155per
V pole is d)
25165
mWb.V* If the
the other. Determine the average flux density between the pole faces a) 0.185 ohms The finish b)
of 0.558
the coilohms
is connected to the generator
hint: φ2 supplies two) φ
= ( 1 – 0.2 hundred, 110 V 75 Watts bulbs, determine the
1
N =through
if a wire moving Rotational or armature
the gap at a speedspeed in meters
of 2.5 rpm per second c) 0.235 ohms start of another coilohms
d) 0.114 away from the first coil. speed of the generator. The field and armature resistance are 110
generates an average voltage of 3.2 volts. The area of either pole ohms and 0.075 ohms respectively.
face is 78.54 cm2. 15.The armature of a six pole generator carries a total current of 350 a) 450 rpm b) 725 rpm
a) 23.2 Tesla b) 12.8 Tesla A. What current flows in each path if the winding is duplex lap ? c) 396.6 rpm d) 525 rpm
c) 10.8 Tesla d) 7.25 Tesla a) 58.33 A b) 175 A
c) 29.17 A d) 14.58 A
FRANCISCAN ENGINEERING REVIEW PROGRAM ELECTRICAL
ELECTRICAL ENGINEERING
ENGINEERING - DC (MACHINES
- DC MACHINES GENERATOR / MOTOR) SEPTEMBER
SUMMER 2019 2020

a = Number of parallel paths in the armature

GENERATOR a = m P ( if simplex lap winding ) Z  2m y  yf
- A machine that converts the inter – action of mechanical energy a = 2 m ( if simplex wave winding ) y y b
and magnetic energy into electrical energy. P 2
- A dynmo is an example of simple generator . m = multiplicity
m = 1 ( if simplex ) , m = 2 ( if duplex )
y = Average pitch
Mech’l Elect’l
Magnetism PARTS OF A DC MACHINE ( GENERATOR ) Z = no. of winding elements on the surface
Input Output of armature core
1. Stationary part - Produces magnetic flux
Generator Nb = 2 ( wave winding )
2. Rotating part
FARADAY’S LAW OF ELECTROMAGNETIC INDUCTION - Armature responsible of converting mechanical energy into
electrical energy
“ Whenever a conductor cuts magnetic flux, dynamically it induces Sample Problems
an emf “ according to the formula TYPES OF ARMATURE WINDINGS
- Armature windings usually uses closed coil type than the open 1. A 4 pole, lap – wound dc armature, the back pitch is 17, if the
coil type. There are two types of closed coil type namely : winding is progressive what is the front pitch ?
a) 32 b) 15 *
1. Ring winding c) 17 d) 13
PNZ
E  =kN 2. Drum winding 2. A 4 pole dc generator with duplex lap winding has 48 slots and
60 a a) lap winding – ( for low voltage, high current generator ). The four element per slot. The flux per pole is 2.5 x 106 maxwells and
finish of each coil is connected to the start of it runs at 1,500 rpm. What is the output voltage ?
the next coil so the winding pitch or a) 60 volts * b) 360 volts
Comparison of emf formula: commutator pitch is unity or one. c) 225 volts d) 120 volts
3. A 4-pole wave wound dc generator has 50 slots and 24 conductors
yb  y f  2m
E2 N  per slot. The flux per pole is 10 mWb. Determine the induced emf in
= 2 2
E1 N1 1 the armature, it it is rotating at a speed of 600 rpm.
a) 240 V* b) 230 V c) 220 V d) 210 V
yb = back pitch ( should be an odd. no. )
yf = front pitch ( should be an odd. no. ) 4. A 4-pole, simplex lap wound, direct current armature has 48 slots
Where : E = generated or induced emf per parallel path + = if the winding is progressive containing 48 coils, each of 10 turns. The flux per pole in the field
E  K N  ( if P , Z and a is considered constants ) - = if the winding is retrogressive structure for this armature, is 500,000 lines. Calculate the speed for
this machine in order that its generated emf be 220 V.
P = Number of Poles a) 2,750 rpm* b) 2,550 rpm c) 2,250 rpm d) 2,000 rpm
Nb = P ( lap winding ) hint: z = 48 (10) (2) = 960 conductors multiply by two kay a = mP =
 = Flux per pole in Weber 8 so in every pole 2 parallel paths or two conductors per element
–8
( 1 Maxwell = 1 x 10 Wb ) Nb = Number of brushes 5. When a generator is being driven at 1,200 rpm, the generated emf
17.The armature of a six pole generator carries a total of 350 A. What 19.A dc generator has aP generated
= No. of poles
emf of 210 V when running at a) 270
is 125V volts. What will be the generated
b) 205 emf
V if the field flux is
current flowsZ in each
= Total
pathnumber of conductors
if the winding is lap ? 700 rpm and the flux per pole is 120 mWb. Determine the generated c) 350 V
decreased by 12% with the speedd)increased
225 V to 1,800 rpm?
a) 175 A = Number of slots xb)no. of conductors
58.3 A per slot emf b) wave winding – ( for high voltage, low current generator ). a) 135 V b) 145 V c) 155 V d) 165 V*
c) 50 A d) 356 A at 1050 rpm. The finish of the coil is connected to the 21.A 15φkW
hint: shunt generator having an armature circuit resistance of
2 = ( 1 – 0.2 ) φ1
N = Rotational or armature speed in rpm a) 300 V start of another
b) 315coil
V away from the first coil. 0.4 ohms and a field resistance of 100 ohms generates a terminal
18.How many parallel paths are there in an eight pole triplex wave c) 381 V d) 175 V voltage of 240 V at full load. Determine the efficiency of the generator
armature ? at full load assuming the iron, friction and windage losses amount to 1
a) 6 * b) 8 20.A 250 V dc shunt wound generator has an armature resistance of kW.
c) 4 d) 2 0.1 ohms. Determine the generated emf when the generator is a) 88.12% b) 82.14%
supplying 50 kW, neglecting the field current of the generator. c) 80.40% d) 78.92%
FRANCISCAN ENGINEERING REVIEW PROGRAM ELECTRICAL
ELECTRICAL ENGINEERING
ENGINEERING - DC (MACHINES
- DC MACHINES GENERATOR / MOTOR) SEPTEMBER
SUMMER 2019 2020

a = Number of parallel paths in the armature

GENERATOR a = m P ( if simplex lap winding ) Z  2m y  yf
- A machine that converts the inter – action of mechanical energy a = 2 m ( if simplex wave winding ) y y b
and magnetic energy into electrical energy. P 2
- A dynmo is an example of simple generator . m = multiplicity
m = 1 ( if simplex ) , m = 2 ( if duplex )
y = Average pitch
Mech’l Elect’l
Magnetism PARTS OF A DC MACHINE ( GENERATOR ) Z = no. of winding elements on the surface
Input Output of armature core
1. Stationary part - Produces magnetic flux
Generator Nb = 2 ( wave winding )
2. Rotating part
FARADAY’S LAW OF ELECTROMAGNETIC INDUCTION - Armature responsible of converting mechanical energy into
electrical energy
“ Whenever a conductor cuts magnetic flux, dynamically it induces Sample Problems
an emf “ according to the formula TYPES OF ARMATURE WINDINGS
- Armature windings usually uses closed coil type than the open 1. A 4 pole, lap – wound dc armature, the back pitch is 17, if the
coil type. There are two types of closed coil type namely : winding is progressive what is the front pitch ?
a) 32 b) 15 *
1. Ring winding c) 17 d) 13
PNZ
E  =kN 2. Drum winding 2. A 4 pole dc generator with duplex lap winding has 48 slots and
60 a a) lap winding – ( for low voltage, high current generator ). The four element per slot. The flux per pole is 2.5 x 106 maxwells and
finish of each coil is connected to the start of it runs at 1,500 rpm. What is the output voltage ?
the next coil so the winding pitch or a) 60 volts * b) 360 volts
Comparison of emf formula: commutator pitch is unity or one. c) 225 volts d) 120 volts
3. A 4-pole wave wound dc generator has 50 slots and 24 conductors
yb  y f  2m
E2 N  per slot. The flux per pole is 10 mWb. Determine the induced emf in
= 2 2
E1 N1 1 the armature, it it is rotating at a speed of 600 rpm.
a) 240 V* b) 230 V c) 220 V d) 210 V
yb = back pitch ( should be an odd. no. )
yf = front pitch ( should be an odd. no. ) 4. A 4-pole, simplex lap wound, direct current armature has 48 slots
Where : E = generated or induced emf per parallel path + = if the winding is progressive containing 48 coils, each of 10 turns. The flux per pole in the field
E  K N  ( if P , Z and a is considered constants ) - = if the winding is retrogressive structure for this armature, is 500,000 lines. Calculate the speed for
this machine in order that its generated emf be 220 V.
P = Number of Poles a) 2,750 rpm* b) 2,550 rpm c) 2,250 rpm d) 2,000 rpm
Nb = P ( lap winding ) hint: z = 48 (10) (2) = 960 conductors multiply by two kay a = mP =
 = Flux per pole in Weber 8 so in every pole 2 parallel paths or two conductors per element
–8
( 1 Maxwell = 1 x 10 Wb ) Nb = Number of brushes 5. When a generator is being driven at 1,200 rpm, the generated emf
Calculate the generatedPemf = when
No. ofthe
poles
speed increases to 25 rev / c) 11.5
is 125kW d) 10 kW
volts. What will be the generated emf if the field flux is
Z is= connected
22.A generator Total number
to aof50conductors
ohms load and a current of 10 A sec. and the pole flux is decreased to 0.18 Wb. decreased by 12% with the speed increased to 1,800 rpm?
= Number of slots
flows. If the armature resistance x no.
is of0.5
conductors per slot
ohms, determine the b) V wave winding – ( for high voltage,
a) 112 b) 240 Vlow current generator ). 25.A four Vpole duplex
a) 135 b) 145lap
V wound dc generator
c) 155 V has d)48165slots
V* with 4
generated emf. c) 270 V The finish d)
of 250
the coil
V is connected to the elements
hint: φ2per
= (slot. When
1 – 0.2 ) φ1driven by its prime mover at a speed of 1,500
a) 455 V N = Rotational or armature b) 500speed
V in rpm start of another coil away from the first coil. rpm, the flux per pole is 2.5 x 106 maxwells. Solve for the output
c) 505 V d) 510 V 24.The armature resistance and shunt field resistance of a dc shunt voltage.
generator are 0.625 and 55 ohms respectively. Determine the power a) 110 V b) 89 V
23.A separately excited generator develops a no-load emf of 180 V at developed in the armature if the load of this machine takes 44 A at c) 60 V d) 57 V
an armature speed of 15 rev / sec. and a flux per pole of 0.20 Wb. 220 volts.
a) 12 kW b) 8.5 kW
FRANCISCAN ENGINEERING REVIEW PROGRAM ELECTRICAL
ELECTRICAL ENGINEERING
ENGINEERING - DC (MACHINES
- DC MACHINES GENERATOR / MOTOR) SEPTEMBER
SUMMER 2019 2020

a = Number of parallel paths in the armature

GENERATOR a = m P ( if simplex lap winding ) Z  2m y  yf
- A machine that converts the inter – action of mechanical energy a = 2 m ( if simplex wave winding ) y y b
and magnetic energy into electrical energy. P 2
- A dynmo is an example of simple generator . m = multiplicity
m = 1 ( if simplex ) , m = 2 ( if duplex )
y = Average pitch
Mech’l Elect’l
Magnetism PARTS OF A DC MACHINE ( GENERATOR ) Z = no. of winding elements on the surface
Input Output of armature core
1. Stationary part - Produces magnetic flux
Generator Nb = 2 ( wave winding )
2. Rotating part
FARADAY’S LAW OF ELECTROMAGNETIC INDUCTION - Armature responsible of converting mechanical energy into
electrical energy
“ Whenever a conductor cuts magnetic flux, dynamically it induces Sample Problems
an emf “ according to the formula TYPES OF ARMATURE WINDINGS
- Armature windings usually uses closed coil type than the open 1. A 4 pole, lap – wound dc armature, the back pitch is 17, if the
coil type. There are two types of closed coil type namely : winding is progressive what is the front pitch ?
a) 32 b) 15 *
1. Ring winding c) 17 d) 13
PNZ
E  =kN 2. Drum winding 2. A 4 pole dc generator with duplex lap winding has 48 slots and
60 a a) lap winding – ( for low voltage, high current generator ). The four element per slot. The flux per pole is 2.5 x 106 maxwells and
finish of each coil is connected to the start of it runs at 1,500 rpm. What is the output voltage ?
the next coil so the winding pitch or a) 60 volts * b) 360 volts
Comparison of emf formula: commutator pitch is unity or one. c) 225 volts d) 120 volts
3. A 4-pole wave wound dc generator has 50 slots and 24 conductors
yb  y f  2m
E2 N  per slot. The flux per pole is 10 mWb. Determine the induced emf in
= 2 2
E1 N1 1 the armature, it it is rotating at a speed of 600 rpm.
a) 240 V* b) 230 V c) 220 V d) 210 V
yb = back pitch ( should be an odd. no. )
yf = front pitch ( should be an odd. no. ) 4. A 4-pole, simplex lap wound, direct current armature has 48 slots
Where : E = generated or induced emf per parallel path + = if the winding is progressive containing 48 coils, each of 10 turns. The flux per pole in the field
E  K N  ( if P , Z and a is considered constants ) - = if the winding is retrogressive structure for this armature, is 500,000 lines. Calculate the speed for
this machine in order that its generated emf be 220 V.
P = Number of Poles a) 2,750 rpm* b) 2,550 rpm c) 2,250 rpm d) 2,000 rpm
Nb = P ( lap winding ) hint: z = 48 (10) (2) = 960 conductors multiply by two kay a = mP =
 = Flux per pole in Weber 8 so in every pole 2 parallel paths or two conductors per element
–8
( 1 Maxwell = 1 x 10 Wb ) Nb = Number of brushes 5. When a generator is being driven at 1,200 rpm, the generated emf
26.Two 6-pole generators A and B have similar operating c) 180 mWb P = No. ofd)poles
0.08 Wb 29.An 8-pole
is 125 volts.dc shunt
What willgenerator with 778emf
be the generated wave connected
if the armature
field flux is
Z except
characteristics = Total number
their of conductors
windings. Find the ratio of their generated conductors
decreasedand running
by 12% withatthe500 rpmincreased
speed supplies toa 1,800
load ofrpm?12.5 ohms
= Number of slots
voltages if A is wound duplex lap and x no.
B isofwound
conductors
duplexper slot
wave. b) armature
28.The wave winding – ( for high
of a 4-pole, voltage,
128 slot shunt low current generator
generator is lap wound ). resistance
a) 135 Vat a terminal
b) 145voltage
V of 250 volts.VIf the armature
c) 155 d) 165resistance
V*
a) 2 : 3 b) 1 : 3 with four conductors per The
slot.finish
The of theper
flux coilpole
is connected
is 50 mWb.to theThe andhint:
fieldφ2resistance
= ( 1 – 0.2are
) φ0.24
1
and 250 ohms respectively, find the flux
c) 3 : 4 N = Rotational or armature d) 1 : speed
2 in rpm armature and shunt field start of another
resistances arecoil away
0.04 ohmfrom the50
and firstohms
coil. per pole.
respectively. Determine the speed of the machine when supplying a) 0.085 Wb b) 2.045 mWb
27.Determine the flux per pole of a six pole generator required to 400 Amp at a terminal voltage of 250 volts. c) 9.83 mWb d) 12.6 mWb
generate 240 V at 500 rpm. The armature has 120 slots with eight a) 580 rpm b) 624 rpm
conductors per slot and is lap wound. c) 645 rpm d) 634 rpm 30.A four pole lap wound dc generator has 48 slots. How many coils
a) 0.015 Wb b) 30 mWb does it have if there are 4 elements per slot ?
FRANCISCAN ENGINEERING REVIEW PROGRAM ELECTRICAL
ELECTRICAL ENGINEERING
ENGINEERING - DC (MACHINES
- DC MACHINES GENERATOR / MOTOR) SEPTEMBER
SUMMER 2019 2020

a = Number of parallel paths in the armature

GENERATOR a = m P ( if simplex lap winding ) Z  2m y  yf
- A machine that converts the inter – action of mechanical energy a = 2 m ( if simplex wave winding ) y y b
and magnetic energy into electrical energy. P 2
- A dynmo is an example of simple generator . m = multiplicity
m = 1 ( if simplex ) , m = 2 ( if duplex )
y = Average pitch
Mech’l Elect’l
Magnetism PARTS OF A DC MACHINE ( GENERATOR ) Z = no. of winding elements on the surface
Input Output of armature core
1. Stationary part - Produces magnetic flux
Generator Nb = 2 ( wave winding )
2. Rotating part
FARADAY’S LAW OF ELECTROMAGNETIC INDUCTION - Armature responsible of converting mechanical energy into
electrical energy
“ Whenever a conductor cuts magnetic flux, dynamically it induces Sample Problems
an emf “ according to the formula TYPES OF ARMATURE WINDINGS
- Armature windings usually uses closed coil type than the open 1. A 4 pole, lap – wound dc armature, the back pitch is 17, if the
coil type. There are two types of closed coil type namely : winding is progressive what is the front pitch ?
a) 32 b) 15 *
1. Ring winding c) 17 d) 13
PNZ
E  =kN 2. Drum winding 2. A 4 pole dc generator with duplex lap winding has 48 slots and
60 a a) lap winding – ( for low voltage, high current generator ). The four element per slot. The flux per pole is 2.5 x 106 maxwells and
finish of each coil is connected to the start of it runs at 1,500 rpm. What is the output voltage ?
the next coil so the winding pitch or a) 60 volts * b) 360 volts
Comparison of emf formula: commutator pitch is unity or one. c) 225 volts d) 120 volts
3. A 4-pole wave wound dc generator has 50 slots and 24 conductors
yb  y f  2m
E2 N  per slot. The flux per pole is 10 mWb. Determine the induced emf in
= 2 2
E1 N1 1 the armature, it it is rotating at a speed of 600 rpm.
a) 240 V* b) 230 V c) 220 V d) 210 V
yb = back pitch ( should be an odd. no. )
yf = front pitch ( should be an odd. no. ) 4. A 4-pole, simplex lap wound, direct current armature has 48 slots
Where : E = generated or induced emf per parallel path + = if the winding is progressive containing 48 coils, each of 10 turns. The flux per pole in the field
E  K N  ( if P , Z and a is considered constants ) - = if the winding is retrogressive structure for this armature, is 500,000 lines. Calculate the speed for
this machine in order that its generated emf be 220 V.
P = Number of Poles a) 2,750 rpm* b) 2,550 rpm c) 2,250 rpm d) 2,000 rpm
Nb = P ( lap winding ) hint: z = 48 (10) (2) = 960 conductors multiply by two kay a = mP =
 = Flux per pole in Weber 8 so in every pole 2 parallel paths or two conductors per element
–8
( 1 Maxwell = 1 x 10 Wb ) Nb = Number of brushes 5. When a generator is being driven at 1,200 rpm, the generated emf
a) 192 b) 96 a) Armature P = No. ofb)poles
Field winding 34.A 6-pole
is 125 generator
volts. What willhas
beathelapgenerated
wound armature with
emf if the 40flux
field slots
is with 20
c) 12 Z = Total number of conductors
d) 52 c) Yoke d) Interpole conductors perbyslot.
decreased 12%Thewithflux
theper poleincreased
speed is 25 mWb. Calculate
to 1,800 rpm?the speed
= Number of slots x no. of conductors per slot b) wave winding – ( for high voltage, low current generator ). at which
a) 135the
V machine must
b) 145 V be drivenc)to155
generate
V an emfd) of
165300
V*V.
31.A shunt generator supplies a 50 kW load at 400 V through cables The finish
33.A 4-pole, wave connected of theofcoil
armature a is
dcconnected
machine to hasthe750 a) 750
hint:rpm
φ2 = ( 1 – 0.2 ) φ1 b) 15 rpm
of resistanceN0.2=ohms.
Rotational
If the or armature
field windingspeed in rpmis 50 ohms and
resistance start
conductors and is driven at 720ofrpm.
another coil
If the awayflux
useful from the
per firstiscoil.
pole 15 c) 1200 rpm d) 900 rpm
the armature resistance is 0.05 ohms, determine the terminal voltage. mWb, determine the generated emf.
a) 431.68 V b) 413.68 V a) 250 V b) 270 V 35.A short shunt compound generator supplies 50 A at 300 V. If the
c) 425.00 V d) 452.52 V c) 225 V d) 288 V field resistance is 30 ohms, the series resistance 0.03 ohms and the
armature resistance 0.05 ohms, determine the emf generated.
32.Which part of a generator provides the path for the magnetic flux ? a) 308.5 V b) 325 V
FRANCISCAN ENGINEERING REVIEW PROGRAM ELECTRICAL
ELECTRICAL ENGINEERING
ENGINEERING - DC (MACHINES
- DC MACHINES GENERATOR / MOTOR) SEPTEMBER
SUMMER 2019 2020

a = Number of parallel paths in the armature

GENERATOR a = m P ( if simplex lap winding ) Z  2m y  yf
- A machine that converts the inter – action of mechanical energy a = 2 m ( if simplex wave winding ) y y b
and magnetic energy into electrical energy. P 2
- A dynmo is an example of simple generator . m = multiplicity
m = 1 ( if simplex ) , m = 2 ( if duplex )
y = Average pitch
Mech’l Elect’l
Magnetism PARTS OF A DC MACHINE ( GENERATOR ) Z = no. of winding elements on the surface
Input Output of armature core
1. Stationary part - Produces magnetic flux
Generator Nb = 2 ( wave winding )
2. Rotating part
FARADAY’S LAW OF ELECTROMAGNETIC INDUCTION - Armature responsible of converting mechanical energy into
electrical energy
“ Whenever a conductor cuts magnetic flux, dynamically it induces Sample Problems
an emf “ according to the formula TYPES OF ARMATURE WINDINGS
- Armature windings usually uses closed coil type than the open 1. A 4 pole, lap – wound dc armature, the back pitch is 17, if the
coil type. There are two types of closed coil type namely : winding is progressive what is the front pitch ?
a) 32 b) 15 *
1. Ring winding c) 17 d) 13
PNZ
E  =kN 2. Drum winding 2. A 4 pole dc generator with duplex lap winding has 48 slots and
60 a a) lap winding – ( for low voltage, high current generator ). The four element per slot. The flux per pole is 2.5 x 106 maxwells and
finish of each coil is connected to the start of it runs at 1,500 rpm. What is the output voltage ?
the next coil so the winding pitch or a) 60 volts * b) 360 volts
Comparison of emf formula: commutator pitch is unity or one. c) 225 volts d) 120 volts
3. A 4-pole wave wound dc generator has 50 slots and 24 conductors
yb  y f  2m
E2 N  per slot. The flux per pole is 10 mWb. Determine the induced emf in
= 2 2
E1 N1 1 the armature, it it is rotating at a speed of 600 rpm.
a) 240 V* b) 230 V c) 220 V d) 210 V
yb = back pitch ( should be an odd. no. )
yf = front pitch ( should be an odd. no. ) 4. A 4-pole, simplex lap wound, direct current armature has 48 slots
Where : E = generated or induced emf per parallel path + = if the winding is progressive containing 48 coils, each of 10 turns. The flux per pole in the field
E  K N  ( if P , Z and a is considered constants ) - = if the winding is retrogressive structure for this armature, is 500,000 lines. Calculate the speed for
this machine in order that its generated emf be 220 V.
P = Number of Poles a) 2,750 rpm* b) 2,550 rpm c) 2,250 rpm d) 2,000 rpm
Nb = P ( lap winding ) hint: z = 48 (10) (2) = 960 conductors multiply by two kay a = mP =
 = Flux per pole in Weber 8 so in every pole 2 parallel paths or two conductors per element
–8
( 1 Maxwell = 1 x 10 Wb ) Nb = Number of brushes 5. When a generator is being driven at 1,200 rpm, the generated emf
c) 300 V d) 304.5 V * a) 450 V P = No. ofb)poles245 V 39.The
is 125voltage build up
volts. What willinbea the
shunt generator
generated is generally
emf if the field restricted
flux is by
Z = Total number of conductors c) 400 V d) 488 V a) speed limitations
decreased by 12% with the speedb)increased
copper heating
to 1,800 rpm?
= generator,
36.For a six-pole Number of slots
how xmany
no. ofmechanical
conductorsdegrees
per slot is the b) wave winding – ( for high voltage, low current generator ). c) saturation
a) 135 V of ironb) 145 V d)
c) brush
155 V resistanced) 165 V*
equivalent of 210 electrical degrees ? The finishdevelops
38.A separately excited generator of the coila is connected
no-load emf ofto the
180 V hint: φ2 = ( 1 – 0.2 ) φ1
a) 35 N = Rotational or armature
b) 70 speed in rpm at an armature speed of 15 start
revof/ sec
another
and coil
a fluxaway
per from
pole the first Wb.
of 0.20 coil.
c) 10.28 d) 3.5 Calculate the generated emf when the speed increases to 20 rev /
sec and the flux per pole remaining unchanged.
37.A 4-pole armature of a dc machine has 1000 conductors and a a) 240 V b) 225 V
flux per pole of 20 mWb. Determine the emf generated when running c) 200 V d) 288 V
at 600 rev / min when the armature is wave wound.
FRANCISCAN ENGINEERING REVIEW PROGRAM ELECTRICAL
ELECTRICAL ENGINEERING
ENGINEERING - DC (MACHINES
- DC MACHINES GENERATOR / MOTOR) SEPTEMBER
SUMMER 2019 2020

a = Number of parallel paths in the armature

GENERATOR a = m P ( if simplex lap winding ) Z  2m y  yf
- A machine that converts the inter – action of mechanical energy a = 2 m ( if simplex wave winding ) y y b
and magnetic energy into electrical energy. P 2
- A dynmo is an example of simple generator . m = multiplicity
m = 1 ( if simplex ) , m = 2 ( if duplex )
y = Average pitch
Mech’l Elect’l
Magnetism PARTS OF A DC MACHINE ( GENERATOR ) Z = no. of winding elements on the surface
Input Output of armature core
1. Stationary part - Produces magnetic flux
Generator Nb = 2 ( wave winding )
2. Rotating part
FARADAY’S LAW OF ELECTROMAGNETIC INDUCTION - Armature responsible of converting mechanical energy into
electrical energy
“ Whenever a conductor cuts magnetic flux, dynamically it induces Sample Problems
an emf “ according to the formula TYPES OF ARMATURE WINDINGS
- Armature windings usually uses closed coil type than the open 1. A 4 pole, lap – wound dc armature, the back pitch is 17, if the
coil type. There are two types of closed coil type namely : winding is progressive what is the front pitch ?
a) 32 b) 15 *
1. Ring winding c) 17 d) 13
PNZ
E  =kN 2. Drum winding 2. A 4 pole dc generator with duplex lap winding has 48 slots and
60 a a) lap winding – ( for low voltage, high current generator ). The four element per slot. The flux per pole is 2.5 x 106 maxwells and
finish of each coil is connected to the start of it runs at 1,500 rpm. What is the output voltage ?
the next coil so the winding pitch or a) 60 volts * b) 360 volts
Comparison of emf formula: commutator pitch is unity or one. c) 225 volts d) 120 volts
3. A 4-pole wave wound dc generator has 50 slots and 24 conductors
yb  y f  2m
E2 N  per slot. The flux per pole is 10 mWb. Determine the induced emf in
= 2 2
E1 N1 1 the armature, it it is rotating at a speed of 600 rpm.
a) 240 V* b) 230 V c) 220 V d) 210 V
yb = back pitch ( should be an odd. no. )
yf = front pitch ( should be an odd. no. ) 4. A 4-pole, simplex lap wound, direct current armature has 48 slots
Where : E = generated or induced emf per parallel path + = if the winding is progressive containing 48 coils, each of 10 turns. The flux per pole in the field
E  K N  ( if P , Z and a is considered constants ) - = if the winding is retrogressive structure for this armature, is 500,000 lines. Calculate the speed for
this machine in order that its generated emf be 220 V.
P = Number of Poles a) 2,750 rpm* b) 2,550 rpm c) 2,250 rpm d) 2,000 rpm
Nb = P ( lap winding ) hint: z = 48 (10) (2) = 960 conductors multiply by two kay a = mP =
 = Flux per pole in Weber 8 so in every pole 2 parallel paths or two conductors per element
–8
( 1 Maxwell = 1 x 10 Wb ) Nb = Number of brushes 5. When a generator is being driven at 1,200 rpm, the generated emf
P = No.
because direct current, of poles
when required, is mainly is (iii) The torque
125 volts. – speed
What will characteristics
be the generated of d.c.
emf if the field motors
flux is
Z = Total number of conductors produced by electronic rectifiers. However, d.c. motors can bybe12%
varied
decreased withover a wide
the speed range while
increased to 1,800retaining
rpm? high
= Number of slots x no. of conductors per slot b)
are wave winding
widely – ( industry
used in for high voltage,
due tolow
thecurrent generator ).
following a) 135 efficiency.
V b) 145 V c) 155 V d) 165 V*
reasons: The finish of the coil is connected to the Due
hint: φ2 to
= above
( 1 – 0.2reasons,
) φ1 d.c. motors are used to drive
N = Rotational or armature speed in rpm start of another coil away from the first coil.
such devices as hoists, fans, pumps, punch-presses etc.
QUESTIONS AND ANSWERS DC GENERATOR (i) speed of s d.c. motor can be changed easily over a
wide range. 2. What purpose is served by the pole shoe in a d.c.
1. What is the importance of d.c. machines ? (ii) speed regulation of d.c. motors is very good. machine?
D.C. generators are not as common as they used to be,
FRANCISCAN ENGINEERING REVIEW PROGRAM ELECTRICAL
ELECTRICAL ENGINEERING
ENGINEERING - DC (MACHINES
- DC MACHINES GENERATOR / MOTOR) SEPTEMBER
SUMMER 2019 2020

a = Number of parallel paths in the armature

GENERATOR a = m P ( if simplex lap winding ) Z  2m y  yf
- A machine that converts the inter – action of mechanical energy a = 2 m ( if simplex wave winding ) y y b
and magnetic energy into electrical energy. P 2
- A dynmo is an example of simple generator . m = multiplicity
m = 1 ( if simplex ) , m = 2 ( if duplex )
y = Average pitch
Mech’l Elect’l
Magnetism PARTS OF A DC MACHINE ( GENERATOR ) Z = no. of winding elements on the surface
Input Output of armature core
1. Stationary part - Produces magnetic flux
Generator Nb = 2 ( wave winding )
2. Rotating part
FARADAY’S LAW OF ELECTROMAGNETIC INDUCTION - Armature responsible of converting mechanical energy into
electrical energy
“ Whenever a conductor cuts magnetic flux, dynamically it induces Sample Problems
an emf “ according to the formula TYPES OF ARMATURE WINDINGS
- Armature windings usually uses closed coil type than the open 1. A 4 pole, lap – wound dc armature, the back pitch is 17, if the
coil type. There are two types of closed coil type namely : winding is progressive what is the front pitch ?
a) 32 b) 15 *
1. Ring winding c) 17 d) 13
PNZ
E  =kN 2. Drum winding 2. A 4 pole dc generator with duplex lap winding has 48 slots and
60 a a) lap winding – ( for low voltage, high current generator ). The four element per slot. The flux per pole is 2.5 x 106 maxwells and
finish of each coil is connected to the start of it runs at 1,500 rpm. What is the output voltage ?
the next coil so the winding pitch or a) 60 volts * b) 360 volts
Comparison of emf formula: commutator pitch is unity or one. c) 225 volts d) 120 volts
3. A 4-pole wave wound dc generator has 50 slots and 24 conductors
yb  y f  2m
E2 N  per slot. The flux per pole is 10 mWb. Determine the induced emf in
= 2 2
E1 N1 1 the armature, it it is rotating at a speed of 600 rpm.
a) 240 V* b) 230 V c) 220 V d) 210 V
yb = back pitch ( should be an odd. no. )
yf = front pitch ( should be an odd. no. ) 4. A 4-pole, simplex lap wound, direct current armature has 48 slots
Where : E = generated or induced emf per parallel path + = if the winding is progressive containing 48 coils, each of 10 turns. The flux per pole in the field
E  K N  ( if P , Z and a is considered constants ) - = if the winding is retrogressive structure for this armature, is 500,000 lines. Calculate the speed for
this machine in order that its generated emf be 220 V.
P = Number of Poles a) 2,750 rpm* b) 2,550 rpm c) 2,250 rpm d) 2,000 rpm
Nb = P ( lap winding ) hint: z = 48 (10) (2) = 960 conductors multiply by two kay a = mP =
 = Flux per pole in Weber 8 so in every pole 2 parallel paths or two conductors per element
–8
( 1 Maxwell = 1 x 10 Wb ) Nb = Number of brushes 5. When a generator is being driven at 1,200 rpm, the generated emf
(i) They spread out the flux in the air gaps. (i) They lubricate P and
= No. of poles
polish the commutator loss. What will be the generated emf if the field flux is
is 125 volts.
Z =
(ii) Since Total
they arenumber of conductors
of lager cross-section, the reluctance (ii) If sparking occurs, they damage the commutator (ii) Dueby to12%highwith
voltage drop, the commutator must be
decreased the speed increased to 1,800 rpm?
= Number of slots x no. of conductors per slot b) wave
of the magnetic path is reduced less winding – ( for
than with thehigh voltage,
copper low current generator ).
brushes a) 135 made
V larger
b) 145than
V for copper
c) 155brushes.
V d) 165 V*
(iii) they support the field coils (iii) They provide good commutationis connected to the
The finish of the coil (iii)φ2Their
hint: = ( 1 low
– 0.2current
) φ1 density necessitates large brush
N = Rotational or armature speed in rpm start of another coil away from the first coil.
holders.
3. What are the advantages and disadvantages of Disadvantages:
carbon brushes ? (i) The contact resistance is high and causes a loss of 4. Why is the armature of d.c. machine made of
about 2V. Hence, they are unsuited for low voltage silicon?
Advantages: machines in which this forms a larger percentage
FRANCISCAN ENGINEERING REVIEW PROGRAM ELECTRICAL
ELECTRICAL ENGINEERING
ENGINEERING - DC (MACHINES
- DC MACHINES GENERATOR / MOTOR) SEPTEMBER
SUMMER 2019 2020

a = Number of parallel paths in the armature

GENERATOR a = m P ( if simplex lap winding ) Z  2m y  yf
- A machine that converts the inter – action of mechanical energy a = 2 m ( if simplex wave winding ) y y b
and magnetic energy into electrical energy. P 2
- A dynmo is an example of simple generator . m = multiplicity
m = 1 ( if simplex ) , m = 2 ( if duplex )
y = Average pitch
Mech’l Elect’l
Magnetism PARTS OF A DC MACHINE ( GENERATOR ) Z = no. of winding elements on the surface
Input Output of armature core
1. Stationary part - Produces magnetic flux
Generator Nb = 2 ( wave winding )
2. Rotating part
FARADAY’S LAW OF ELECTROMAGNETIC INDUCTION - Armature responsible of converting mechanical energy into
electrical energy
“ Whenever a conductor cuts magnetic flux, dynamically it induces Sample Problems
an emf “ according to the formula TYPES OF ARMATURE WINDINGS
- Armature windings usually uses closed coil type than the open 1. A 4 pole, lap – wound dc armature, the back pitch is 17, if the
coil type. There are two types of closed coil type namely : winding is progressive what is the front pitch ?
a) 32 b) 15 *
1. Ring winding c) 17 d) 13
PNZ
E  =kN 2. Drum winding 2. A 4 pole dc generator with duplex lap winding has 48 slots and
60 a a) lap winding – ( for low voltage, high current generator ). The four element per slot. The flux per pole is 2.5 x 106 maxwells and
finish of each coil is connected to the start of it runs at 1,500 rpm. What is the output voltage ?
the next coil so the winding pitch or a) 60 volts * b) 360 volts
Comparison of emf formula: commutator pitch is unity or one. c) 225 volts d) 120 volts
3. A 4-pole wave wound dc generator has 50 slots and 24 conductors
yb  y f  2m
E2 N  per slot. The flux per pole is 10 mWb. Determine the induced emf in
= 2 2
E1 N1 1 the armature, it it is rotating at a speed of 600 rpm.
a) 240 V* b) 230 V c) 220 V d) 210 V
yb = back pitch ( should be an odd. no. )
yf = front pitch ( should be an odd. no. ) 4. A 4-pole, simplex lap wound, direct current armature has 48 slots
Where : E = generated or induced emf per parallel path + = if the winding is progressive containing 48 coils, each of 10 turns. The flux per pole in the field
E  K N  ( if P , Z and a is considered constants ) - = if the winding is retrogressive structure for this armature, is 500,000 lines. Calculate the speed for
this machine in order that its generated emf be 220 V.
P = Number of Poles a) 2,750 rpm* b) 2,550 rpm c) 2,250 rpm d) 2,000 rpm
Nb = P ( lap winding ) hint: z = 48 (10) (2) = 960 conductors multiply by two kay a = mP =
 = Flux per pole in Weber 8 so in every pole 2 parallel paths or two conductors per element
–8
( 1 Maxwell = 1 x 10 Wb ) Nb = Number of brushes 5. When a generator is being driven at 1,200 rpm, the generated emf
The most important function of an armature is to P = No. of poles pressure.
is 125 volts. What will be the generated emf if the field flux is
provideZ a low
= Total number of
reluctance conductors
path for the flux through the The slotted armature has the following advantages : decreased by 12% with the speed increased to 1,800 rpm?
= Number of slots x no. of conductors per slot b) waveair-gap
winding can
– ( for
armature from the N – pole – shoe to the S ones. It is (i) The behigh voltage,
reduced tolow current
a value generator
required for). 6. a)Why
135 Vis armature
b) 145 Vwindingc)placed
155 V on thed) rotor
165 V*of a
therefore, made of a material having high permeability The finish of the coil is connected
mechanical clearance. This reduces the reluctance to the d.c.machine?
hint: φ2 = ( 1 – 0.2 ) φ1
N = Rotational or armature speed in rpm start of another coil away from the first coil.
e.g. silicon steel. An additional advantage of silicon of the magnetic circuit.
steel is that it has low hysteresis loss. (ii) The conductors can be properly placed so that The armature winding of a d.c. machine is placed on
there is little fear of them being displaced. the rotor to facilitate commutation i.e. to convert the
5. Why do we use slotted armature in a d.c. (iii) The drag on the conductors is greatly reduced so alternating voltage produced in the winding into direct
machine? that their insulation is in no danger of damage by voltage at the brushes.
FRANCISCAN ENGINEERING REVIEW PROGRAM ELECTRICAL
ELECTRICAL ENGINEERING
ENGINEERING - DC (MACHINES
- DC MACHINES GENERATOR / MOTOR) SEPTEMBER
SUMMER 2019 2020

a = Number of parallel paths in the armature

GENERATOR a = m P ( if simplex lap winding ) Z  2m y  yf
- A machine that converts the inter – action of mechanical energy a = 2 m ( if simplex wave winding ) y y b
and magnetic energy into electrical energy. P 2
- A dynmo is an example of simple generator . m = multiplicity
m = 1 ( if simplex ) , m = 2 ( if duplex )
y = Average pitch
Mech’l Elect’l
Magnetism PARTS OF A DC MACHINE ( GENERATOR ) Z = no. of winding elements on the surface
Input Output of armature core
1. Stationary part - Produces magnetic flux
Generator Nb = 2 ( wave winding )
2. Rotating part
FARADAY’S LAW OF ELECTROMAGNETIC INDUCTION - Armature responsible of converting mechanical energy into
electrical energy
“ Whenever a conductor cuts magnetic flux, dynamically it induces Sample Problems
an emf “ according to the formula TYPES OF ARMATURE WINDINGS
- Armature windings usually uses closed coil type than the open 1. A 4 pole, lap – wound dc armature, the back pitch is 17, if the
coil type. There are two types of closed coil type namely : winding is progressive what is the front pitch ?
a) 32 b) 15 *
1. Ring winding c) 17 d) 13
PNZ
E  =kN 2. Drum winding 2. A 4 pole dc generator with duplex lap winding has 48 slots and
60 a a) lap winding – ( for low voltage, high current generator ). The four element per slot. The flux per pole is 2.5 x 106 maxwells and
finish of each coil is connected to the start of it runs at 1,500 rpm. What is the output voltage ?
the next coil so the winding pitch or a) 60 volts * b) 360 volts
Comparison of emf formula: commutator pitch is unity or one. c) 225 volts d) 120 volts
3. A 4-pole wave wound dc generator has 50 slots and 24 conductors
yb  y f  2m
E2 N  per slot. The flux per pole is 10 mWb. Determine the induced emf in
= 2 2
E1 N1 1 the armature, it it is rotating at a speed of 600 rpm.
a) 240 V* b) 230 V c) 220 V d) 210 V
yb = back pitch ( should be an odd. no. )
yf = front pitch ( should be an odd. no. ) 4. A 4-pole, simplex lap wound, direct current armature has 48 slots
Where : E = generated or induced emf per parallel path + = if the winding is progressive containing 48 coils, each of 10 turns. The flux per pole in the field
E  K N  ( if P , Z and a is considered constants ) - = if the winding is retrogressive structure for this armature, is 500,000 lines. Calculate the speed for
this machine in order that its generated emf be 220 V.
P = Number of Poles a) 2,750 rpm* b) 2,550 rpm c) 2,250 rpm d) 2,000 rpm
Nb = P ( lap winding ) hint: z = 48 (10) (2) = 960 conductors multiply by two kay a = mP =
 = Flux per pole in Weber 8 so in every pole 2 parallel paths or two conductors per element
–8
( 1 Maxwell = 1 x 10 Wb ) Nb = Number of brushes 5. When a generator is being driven at 1,200 rpm, the generated emf
The lower limit is Pdue= to
No.current
of polesper brush arm which is In
125order
volts. to avoid
What will this difficulty,
be the generated the
emfcoils
if theare generally
field flux is
7. What Zfactors
= Total number of conductors
determine the number of poles in a should not exceed 400 A otherwise an excessively long arrangedbyin12%
decreased twowith
layers. Eachincreased
the speed coil has one of its
to 1,800 sides at
rpm?
= Number of slots x no. of conductors per slot b) wave winding
d.c. machine? commutator will –be
( for high voltage, low current generator ).
necessary. a)the
135top
V of the slot Vand the other
b) 145 c) 155atV the bottom of some
d) 165 V*
The finish of the coil is connected to the other
hint: φ2 =slot.
( 1 –The
0.2 )coil
φ1 ends will then lie side by side.
N = Rotational or armature speed in rpm start of another coil away from the first coil.
The number of poles in a d.c. machine is governed by : 8. Why is armature winding of a d.c. machine always
(i) frequency (ii) current per brush arm double layer winding? 9. What is the essential difference between lap and
The upper limit to the number of poles is imposed by wave windings?
frequency which is of the order 20-3- Hz for large When the coil sides are placed in one layer, it is difficult
machines and not exceeding 50 Hz for small machines. to arrange their ends so that they will pass each other. The essential difference between a lap winding and a
FRANCISCAN ENGINEERING REVIEW PROGRAM ELECTRICAL
ELECTRICAL ENGINEERING
ENGINEERING - DC (MACHINES
- DC MACHINES GENERATOR / MOTOR) SEPTEMBER
SUMMER 2019 2020

a = Number of parallel paths in the armature

GENERATOR a = m P ( if simplex lap winding ) Z  2m y  yf
- A machine that converts the inter – action of mechanical energy a = 2 m ( if simplex wave winding ) y y b
and magnetic energy into electrical energy. P 2
- A dynmo is an example of simple generator . m = multiplicity
m = 1 ( if simplex ) , m = 2 ( if duplex )
y = Average pitch
Mech’l Elect’l
Magnetism PARTS OF A DC MACHINE ( GENERATOR ) Z = no. of winding elements on the surface
Input Output of armature core
1. Stationary part - Produces magnetic flux
Generator Nb = 2 ( wave winding )
2. Rotating part
FARADAY’S LAW OF ELECTROMAGNETIC INDUCTION - Armature responsible of converting mechanical energy into
electrical energy
“ Whenever a conductor cuts magnetic flux, dynamically it induces Sample Problems
an emf “ according to the formula TYPES OF ARMATURE WINDINGS
- Armature windings usually uses closed coil type than the open 1. A 4 pole, lap – wound dc armature, the back pitch is 17, if the
coil type. There are two types of closed coil type namely : winding is progressive what is the front pitch ?
a) 32 b) 15 *
1. Ring winding c) 17 d) 13
PNZ
E  =kN 2. Drum winding 2. A 4 pole dc generator with duplex lap winding has 48 slots and
60 a a) lap winding – ( for low voltage, high current generator ). The four element per slot. The flux per pole is 2.5 x 106 maxwells and
finish of each coil is connected to the start of it runs at 1,500 rpm. What is the output voltage ?
the next coil so the winding pitch or a) 60 volts * b) 360 volts
Comparison of emf formula: commutator pitch is unity or one. c) 225 volts d) 120 volts
3. A 4-pole wave wound dc generator has 50 slots and 24 conductors
yb  y f  2m
E2 N  per slot. The flux per pole is 10 mWb. Determine the induced emf in
= 2 2
E1 N1 1 the armature, it it is rotating at a speed of 600 rpm.
a) 240 V* b) 230 V c) 220 V d) 210 V
yb = back pitch ( should be an odd. no. )
yf = front pitch ( should be an odd. no. ) 4. A 4-pole, simplex lap wound, direct current armature has 48 slots
Where : E = generated or induced emf per parallel path + = if the winding is progressive containing 48 coils, each of 10 turns. The flux per pole in the field
E  K N  ( if P , Z and a is considered constants ) - = if the winding is retrogressive structure for this armature, is 500,000 lines. Calculate the speed for
this machine in order that its generated emf be 220 V.
P = Number of Poles a) 2,750 rpm* b) 2,550 rpm c) 2,250 rpm d) 2,000 rpm
Nb = P ( lap winding ) hint: z = 48 (10) (2) = 960 conductors multiply by two kay a = mP =
 = Flux per pole in Weber 8 so in every pole 2 parallel paths or two conductors per element
–8
( 1 Maxwell = 1 x 10 Wb ) Nb = Number of brushes 5. When a generator is being driven at 1,200 rpm, the generated emf
wave winding is in the commutator connections. In a lap commutator, two Por =more
No. of poles paths are formed
parallel is generators?
125 volts. What will be the generated emf if the field flux is
Z the
winding, = Total number ofpitch
commutator conductors
is 1 whereas for a wave depending upon the type of winding. Each parallel path decreased by 12% with the speed increased to 1,800 rpm?
= Number of slots x no. of conductors per slot
winding it is about twice the pole pitch. b) wave of
consists winding
same–number
( for highof
voltage,
coils inlow current generator ).
series. a)For
135aVgiven number
b) 145 V of armature
c) 155conductors,
V d)a165
lapV*
The finish of the coil is
(i) With a lap winding, the number of parallelconnected to the
paths winding can carry
hint: φ2 = ( 1 – 0.2 ) φ1a heavier current than a wave winding
N = Rotational or armature speed in rpm start of another coil away from the first coil. because it has more parallel paths. Therefore, lap
10. The armature winding of a d.c. machine is a single formed is equal to the number of poles.
closed loop. How do we get parallel paths? winding is used in large multipolar d.c. generators to
(ii) With a wave winding, the number of parallel paths avoid having conductors of large cross-section.
Whether the winding be lap or wave, when the brushes formed is 2 irrespective of the number of poles.
are lifted, the armature circuit is a single closed loop. 12. Why are equalizers not used in wave winding?
However, when brushes are lowered on to the 11. Why is lap winding used in large multipolar d.c.
FRANCISCAN ENGINEERING REVIEW PROGRAM ELECTRICAL
ELECTRICAL ENGINEERING
ENGINEERING - DC (MACHINES
- DC MACHINES GENERATOR / MOTOR) SEPTEMBER
SUMMER 2019 2020

a = Number of parallel paths in the armature

GENERATOR a = m P ( if simplex lap winding ) Z  2m y  yf
- A machine that converts the inter – action of mechanical energy a = 2 m ( if simplex wave winding ) y y b
and magnetic energy into electrical energy. P 2
- A dynmo is an example of simple generator . m = multiplicity
m = 1 ( if simplex ) , m = 2 ( if duplex )
y = Average pitch
Mech’l Elect’l
Magnetism PARTS OF A DC MACHINE ( GENERATOR ) Z = no. of winding elements on the surface
Input Output of armature core
1. Stationary part - Produces magnetic flux
Generator Nb = 2 ( wave winding )
2. Rotating part
FARADAY’S LAW OF ELECTROMAGNETIC INDUCTION - Armature responsible of converting mechanical energy into
electrical energy
“ Whenever a conductor cuts magnetic flux, dynamically it induces Sample Problems
an emf “ according to the formula TYPES OF ARMATURE WINDINGS
- Armature windings usually uses closed coil type than the open 1. A 4 pole, lap – wound dc armature, the back pitch is 17, if the
coil type. There are two types of closed coil type namely : winding is progressive what is the front pitch ?
a) 32 b) 15 *
1. Ring winding c) 17 d) 13
PNZ
E  =kN 2. Drum winding 2. A 4 pole dc generator with duplex lap winding has 48 slots and
60 a a) lap winding – ( for low voltage, high current generator ). The four element per slot. The flux per pole is 2.5 x 106 maxwells and
finish of each coil is connected to the start of it runs at 1,500 rpm. What is the output voltage ?
the next coil so the winding pitch or a) 60 volts * b) 360 volts
Comparison of emf formula: commutator pitch is unity or one. c) 225 volts d) 120 volts
3. A 4-pole wave wound dc generator has 50 slots and 24 conductors
yb  y f  2m
E2 N  per slot. The flux per pole is 10 mWb. Determine the induced emf in
= 2 2
E1 N1 1 the armature, it it is rotating at a speed of 600 rpm.
a) 240 V* b) 230 V c) 220 V d) 210 V
yb = back pitch ( should be an odd. no. )
yf = front pitch ( should be an odd. no. ) 4. A 4-pole, simplex lap wound, direct current armature has 48 slots
Where : E = generated or induced emf per parallel path + = if the winding is progressive containing 48 coils, each of 10 turns. The flux per pole in the field
E  K N  ( if P , Z and a is considered constants ) - = if the winding is retrogressive structure for this armature, is 500,000 lines. Calculate the speed for
this machine in order that its generated emf be 220 V.
P = Number of Poles a) 2,750 rpm* b) 2,550 rpm c) 2,250 rpm d) 2,000 rpm
Nb = P ( lap winding ) hint: z = 48 (10) (2) = 960 conductors multiply by two kay a = mP =
 = Flux per pole in Weber 8 so in every pole 2 parallel paths or two conductors per element
–8
( 1 Maxwell = 1 x 10 Wb ) Nb = Number of brushes 5. When a generator is being driven at 1,200 rpm, the generated emf
There is no need for “Equilizers” in a wave-wound restricted to eitherP two
= No. of poles
parallel circuits (wave) or ten 14.is Discuss
125 volts. the
Whatnomenclature of multiplex
will be the generated winding.
emf if the field flux is
Z because
machine = Total number of conductors
conductors in each of the two parallel parallel circuits (lap). However, sometimes, it is desired decreased by 12% with the speed increased to 1,800 rpm?
= Number of slots x no. of conductors per slot
paths pass under all the N and S poles successively. b) wave winding
to increase – ( for high
the number of voltage,
parallel low current
paths, generator
enabling the). a)The
135 nomenclature
V b) 145 Vof multiplex winding
c) 155 V is according
d) 165 V* to
The finish of the coil is connected
armature to carry large current and at the same time to the the number of parallel
hint: φ2 = ( 1 – 0.2 ) φ1 paths formed.
13. What N = Rotational
is the need ofor armature speed
multiplex in rpm
winding? start of another coil away from the first coil.
reducing the conductor current. For this purpose, (i) The number of parallel paths in a multiplex lap
multiplex windings are used. Thus with duplex wave winding is given by :
With simple wave winding, there are only 2 parallel
paths whereas for a lap winding, the number of parallel winding, the above 10-pole machine will have 4 parallel
paths. Likewise, with duplex lap winding, the machine No. of parallel paths = No. of poles(P) x Degree of plex
paths is equal to the number of poles. Thus in case of a Thus, a duplex wave winding is one in which the number
10-pole machine, using simple winding, the designer is will have 20 parallel paths.
of parallel paths = 2 x 2 = 4. A triplex wave winding
FRANCISCAN ENGINEERING REVIEW PROGRAM ELECTRICAL
ELECTRICAL ENGINEERING
ENGINEERING - DC (MACHINES
- DC MACHINES GENERATOR / MOTOR) SEPTEMBER
SUMMER 2019 2020

a = Number of parallel paths in the armature

GENERATOR a = m P ( if simplex lap winding ) Z  2m y  yf
- A machine that converts the inter – action of mechanical energy a = 2 m ( if simplex wave winding ) y y b
and magnetic energy into electrical energy. P 2
- A dynmo is an example of simple generator . m = multiplicity
m = 1 ( if simplex ) , m = 2 ( if duplex )
y = Average pitch
Mech’l Elect’l
Magnetism PARTS OF A DC MACHINE ( GENERATOR ) Z = no. of winding elements on the surface
Input Output of armature core
1. Stationary part - Produces magnetic flux
Generator Nb = 2 ( wave winding )
2. Rotating part
FARADAY’S LAW OF ELECTROMAGNETIC INDUCTION - Armature responsible of converting mechanical energy into
electrical energy
“ Whenever a conductor cuts magnetic flux, dynamically it induces Sample Problems
an emf “ according to the formula TYPES OF ARMATURE WINDINGS
- Armature windings usually uses closed coil type than the open 1. A 4 pole, lap – wound dc armature, the back pitch is 17, if the
coil type. There are two types of closed coil type namely : winding is progressive what is the front pitch ?
a) 32 b) 15 *
1. Ring winding c) 17 d) 13
PNZ
E  =kN 2. Drum winding 2. A 4 pole dc generator with duplex lap winding has 48 slots and
60 a a) lap winding – ( for low voltage, high current generator ). The four element per slot. The flux per pole is 2.5 x 106 maxwells and
finish of each coil is connected to the start of it runs at 1,500 rpm. What is the output voltage ?
the next coil so the winding pitch or a) 60 volts * b) 360 volts
Comparison of emf formula: commutator pitch is unity or one. c) 225 volts d) 120 volts
3. A 4-pole wave wound dc generator has 50 slots and 24 conductors
yb  y f  2m
E2 N  per slot. The flux per pole is 10 mWb. Determine the induced emf in
= 2 2
E1 N1 1 the armature, it it is rotating at a speed of 600 rpm.
a) 240 V* b) 230 V c) 220 V d) 210 V
yb = back pitch ( should be an odd. no. )
yf = front pitch ( should be an odd. no. ) 4. A 4-pole, simplex lap wound, direct current armature has 48 slots
Where : E = generated or induced emf per parallel path + = if the winding is progressive containing 48 coils, each of 10 turns. The flux per pole in the field
E  K N  ( if P , Z and a is considered constants ) - = if the winding is retrogressive structure for this armature, is 500,000 lines. Calculate the speed for
this machine in order that its generated emf be 220 V.
P = Number of Poles a) 2,750 rpm* b) 2,550 rpm c) 2,250 rpm d) 2,000 rpm
Nb = P ( lap winding ) hint: z = 48 (10) (2) = 960 conductors multiply by two kay a = mP =
 = Flux per pole in Weber 8 so in every pole 2 parallel paths or two conductors per element
–8
( 1 Maxwell = 1 x 10 Wb ) Nb = Number of brushes 5. When a generator is being driven at 1,200 rpm, the generated emf
will have 2 x 3 = 6 parallel paths. (ii) The length ofP the
= No. of polescircuit is reduced,
magnetic is (v) Too What
125 volts. smallwill
a number of polesemf
be the generated means
if theafield
large
flux is
Z = Total number of conductors resulting in the reduction of field ampere turns. number of with
armature ampere-turns per pole and a
decreased by 12% the speed increased to 1,800 rpm?
15. What are=the Number of slots x no.
advantages of conductors
of using a largepernumber
slot b) wave winding – ( for high voltage, low current generator ). a) 135 Vhigh value of Varmature c)
b) 145 reaction,
155 V which d) requires
165 V* a
of poles in a d.c. machine? (iii) The length of The
the armature
finish of theend connections
coil is connected toisthe hint: φ2 longer
= ( 1 – air-gap.
0.2 ) φ1
N = Rotational or armature speed in rpm reduced. start of another coil away from the first coil.
The advantages of using a large number of poles in a 16. What are the disadvantages of using a large
d.c. machine are : (iv) The current per brush arm is reduced. This number of poles in a d.c. machine?
(i) The flux per pole is reduced. This reduces the reduces
thickness of armature core and yoke and hence the length of the commutator. The disadvantages of a large number of poles in a d.c.
the weight of the machine. machine are :
FRANCISCAN ENGINEERING REVIEW PROGRAM ELECTRICAL
ELECTRICAL ENGINEERING
ENGINEERING - DC (MACHINES
- DC MACHINES GENERATOR / MOTOR) SEPTEMBER
SUMMER 2019 2020

a = Number of parallel paths in the armature

GENERATOR a = m P ( if simplex lap winding ) Z  2m y  yf
- A machine that converts the inter – action of mechanical energy a = 2 m ( if simplex wave winding ) y y b
and magnetic energy into electrical energy. P 2
- A dynmo is an example of simple generator . m = multiplicity
m = 1 ( if simplex ) , m = 2 ( if duplex )
y = Average pitch
Mech’l Elect’l
Magnetism PARTS OF A DC MACHINE ( GENERATOR ) Z = no. of winding elements on the surface
Input Output of armature core
1. Stationary part - Produces magnetic flux
Generator Nb = 2 ( wave winding )
2. Rotating part
FARADAY’S LAW OF ELECTROMAGNETIC INDUCTION - Armature responsible of converting mechanical energy into
electrical energy
“ Whenever a conductor cuts magnetic flux, dynamically it induces Sample Problems
an emf “ according to the formula TYPES OF ARMATURE WINDINGS
- Armature windings usually uses closed coil type than the open 1. A 4 pole, lap – wound dc armature, the back pitch is 17, if the
coil type. There are two types of closed coil type namely : winding is progressive what is the front pitch ?
a) 32 b) 15 *
1. Ring winding c) 17 d) 13
PNZ
E  =kN 2. Drum winding 2. A 4 pole dc generator with duplex lap winding has 48 slots and
60 a a) lap winding – ( for low voltage, high current generator ). The four element per slot. The flux per pole is 2.5 x 106 maxwells and
finish of each coil is connected to the start of it runs at 1,500 rpm. What is the output voltage ?
the next coil so the winding pitch or a) 60 volts * b) 360 volts
Comparison of emf formula: commutator pitch is unity or one. c) 225 volts d) 120 volts
3. A 4-pole wave wound dc generator has 50 slots and 24 conductors
yb  y f  2m
E2 N  per slot. The flux per pole is 10 mWb. Determine the induced emf in
= 2 2
E1 N1 1 the armature, it it is rotating at a speed of 600 rpm.
a) 240 V* b) 230 V c) 220 V d) 210 V
yb = back pitch ( should be an odd. no. )
yf = front pitch ( should be an odd. no. ) 4. A 4-pole, simplex lap wound, direct current armature has 48 slots
Where : E = generated or induced emf per parallel path + = if the winding is progressive containing 48 coils, each of 10 turns. The flux per pole in the field
E  K N  ( if P , Z and a is considered constants ) - = if the winding is retrogressive structure for this armature, is 500,000 lines. Calculate the speed for
this machine in order that its generated emf be 220 V.
P = Number of Poles a) 2,750 rpm* b) 2,550 rpm c) 2,250 rpm d) 2,000 rpm
Nb = P ( lap winding ) hint: z = 48 (10) (2) = 960 conductors multiply by two kay a = mP =
 = Flux per pole in Weber 8 so in every pole 2 parallel paths or two conductors per element
–8
( 1 Maxwell = 1 x 10 Wb ) Nb = Number of brushes 5. When a generator is being driven at 1,200 rpm, the generated emf
(iv) The armaturePdiameter
= No. of is
poles
increased. is excessively long
125 volts. What willcommutator will emf
be the generated be necessary. These
if the field flux is
(i) MoreZ commutator
= Total number segments are needed or
of conductors limits usually
decreased by 12%restrict
with thethe choice
speed to about
increased two rpm?
to 1,800
= Number
alternatively of slots
there must x no.
be of conductors
more per segment
volts per slot 17. b)
What decides
wave windingthe upper
– ( for and lower
high voltage, limit generator
low current to the ). a)alternatives.
135 V b) 145 V c) 155 V d) 165 V*
for a given commutator diameter and thickness of number of polesThe in afinish
d.c.ofmachine?
the coil is connected to the hint: φ2 = ( 1 – 0.2 ) φ1
N = Rotational or armature speed in rpm
segment. start of another coil away from the first coil. 18. What are the advantages and disadvantages of a
(ii) The brush arms are closer together, increasing the The upper limit to the number of poles is imposed by separately excited generator over a self-excited
danger of flash-over. frequency which is of the order 20-30 Hz for large generator?
(iii) Frequency is proportional to number of poles and machines and not exceeding 50 Hz for small ones. The
lower limit is decided by the current per brush arm The advantages of a separately excited generator over a
core loss depends upon frequency. which should not exceed 400 A otherwise an self-excited generator are:
FRANCISCAN ENGINEERING REVIEW PROGRAM ELECTRICAL
ELECTRICAL ENGINEERING
ENGINEERING - DC (MACHINES
- DC MACHINES GENERATOR / MOTOR) SEPTEMBER
SUMMER 2019 2020

a = Number of parallel paths in the armature

GENERATOR a = m P ( if simplex lap winding ) Z  2m y  yf
- A machine that converts the inter – action of mechanical energy a = 2 m ( if simplex wave winding ) y y b
and magnetic energy into electrical energy. P 2
- A dynmo is an example of simple generator . m = multiplicity
m = 1 ( if simplex ) , m = 2 ( if duplex )
y = Average pitch
Mech’l Elect’l
Magnetism PARTS OF A DC MACHINE ( GENERATOR ) Z = no. of winding elements on the surface
Input Output of armature core
1. Stationary part - Produces magnetic flux
Generator Nb = 2 ( wave winding )
2. Rotating part
FARADAY’S LAW OF ELECTROMAGNETIC INDUCTION - Armature responsible of converting mechanical energy into
electrical energy
“ Whenever a conductor cuts magnetic flux, dynamically it induces Sample Problems
an emf “ according to the formula TYPES OF ARMATURE WINDINGS
- Armature windings usually uses closed coil type than the open 1. A 4 pole, lap – wound dc armature, the back pitch is 17, if the
coil type. There are two types of closed coil type namely : winding is progressive what is the front pitch ?
a) 32 b) 15 *
1. Ring winding c) 17 d) 13
PNZ
E  =kN 2. Drum winding 2. A 4 pole dc generator with duplex lap winding has 48 slots and
60 a a) lap winding – ( for low voltage, high current generator ). The four element per slot. The flux per pole is 2.5 x 106 maxwells and
finish of each coil is connected to the start of it runs at 1,500 rpm. What is the output voltage ?
the next coil so the winding pitch or a) 60 volts * b) 360 volts
Comparison of emf formula: commutator pitch is unity or one. c) 225 volts d) 120 volts
3. A 4-pole wave wound dc generator has 50 slots and 24 conductors
yb  y f  2m
E2 N  per slot. The flux per pole is 10 mWb. Determine the induced emf in
= 2 2
E1 N1 1 the armature, it it is rotating at a speed of 600 rpm.
a) 240 V* b) 230 V c) 220 V d) 210 V
yb = back pitch ( should be an odd. no. )
yf = front pitch ( should be an odd. no. ) 4. A 4-pole, simplex lap wound, direct current armature has 48 slots
Where : E = generated or induced emf per parallel path + = if the winding is progressive containing 48 coils, each of 10 turns. The flux per pole in the field
E  K N  ( if P , Z and a is considered constants ) - = if the winding is retrogressive structure for this armature, is 500,000 lines. Calculate the speed for
this machine in order that its generated emf be 220 V.
P = Number of Poles a) 2,750 rpm* b) 2,550 rpm c) 2,250 rpm d) 2,000 rpm
Nb = P ( lap winding ) hint: z = 48 (10) (2) = 960 conductors multiply by two kay a = mP =
 = Flux per pole in Weber 8 so in every pole 2 parallel paths or two conductors per element
–8
( 1 Maxwell = 1 x 10 Wb ) Nb = Number of brushes 5. When a generator is being driven at 1,200 rpm, the generated emf
(i) The field ampere-turns can be independently P = No. of poles is (i) The field
125 volts. Whatconnections are incorrect.
will be the generated emf if the field flux is
Z = Total number of conductors
controlled. Note: D.C generators are rarely separately excited. But (ii) The byresistance of the field circuit is
decreased 12% with the speed increased to too
1,800high.
rpm?
= Number of slots x no. of conductors per slot b) wave winding
practically – ( for high voltage,
all a.c. generators low current
are separately generator ).
excited.
(ii) It will operate in a stable condition with any field a)(iii)
135 the
V speed is too
b) 145 V low. c) 155 V d) 165 V*
excitation. The finish of the coil is connected to the (iv)φ2 there
hint: = ( 1 –is0.2
sufficient
) φ1 residual magnetism.
N = Rotational or armature speed in rpm 19. what are the factors that
start of affect
another coilthe
awayvoltage
from the build-
first coil.
(iii) We can have a wide range of output voltages.
up of a d.c. shunt generator? 20. Why is series generator not generally used?
The disadvantages of a separately excited generator as
The voltage of a shunt generator may fail to build up The external characteristic of a series generator shows
compared to a self-excited generator are:
for that during the initial portion of the curve, the terminal
(i) A separate d.c. source is required.
one or more of the following reasons: voltage increase with the increase in load. This is an
(ii) It is an inconvenient arrangement.
FRANCISCAN ENGINEERING REVIEW PROGRAM ELECTRICAL
ELECTRICAL ENGINEERING
ENGINEERING - DC (MACHINES
- DC MACHINES GENERATOR / MOTOR) SEPTEMBER
SUMMER 2019 2020

a = Number of parallel paths in the armature

GENERATOR a = m P ( if simplex lap winding ) Z  2m y  yf
- A machine that converts the inter – action of mechanical energy a = 2 m ( if simplex wave winding ) y y b
and magnetic energy into electrical energy. P 2
- A dynmo is an example of simple generator . m = multiplicity
m = 1 ( if simplex ) , m = 2 ( if duplex )
y = Average pitch
Mech’l Elect’l
Magnetism PARTS OF A DC MACHINE ( GENERATOR ) Z = no. of winding elements on the surface
Input Output of armature core
1. Stationary part - Produces magnetic flux
Generator Nb = 2 ( wave winding )
2. Rotating part
FARADAY’S LAW OF ELECTROMAGNETIC INDUCTION - Armature responsible of converting mechanical energy into
electrical energy
“ Whenever a conductor cuts magnetic flux, dynamically it induces Sample Problems
an emf “ according to the formula TYPES OF ARMATURE WINDINGS
- Armature windings usually uses closed coil type than the open 1. A 4 pole, lap – wound dc armature, the back pitch is 17, if the
coil type. There are two types of closed coil type namely : winding is progressive what is the front pitch ?
a) 32 b) 15 *
1. Ring winding c) 17 d) 13
PNZ
E  =kN 2. Drum winding 2. A 4 pole dc generator with duplex lap winding has 48 slots and
60 a a) lap winding – ( for low voltage, high current generator ). The four element per slot. The flux per pole is 2.5 x 106 maxwells and
finish of each coil is connected to the start of it runs at 1,500 rpm. What is the output voltage ?
the next coil so the winding pitch or a) 60 volts * b) 360 volts
Comparison of emf formula: commutator pitch is unity or one. c) 225 volts d) 120 volts
3. A 4-pole wave wound dc generator has 50 slots and 24 conductors
yb  y f  2m
E2 N  per slot. The flux per pole is 10 mWb. Determine the induced emf in
= 2 2
E1 N1 1 the armature, it it is rotating at a speed of 600 rpm.
a) 240 V* b) 230 V c) 220 V d) 210 V
yb = back pitch ( should be an odd. no. )
yf = front pitch ( should be an odd. no. ) 4. A 4-pole, simplex lap wound, direct current armature has 48 slots
Where : E = generated or induced emf per parallel path + = if the winding is progressive containing 48 coils, each of 10 turns. The flux per pole in the field
E  K N  ( if P , Z and a is considered constants ) - = if the winding is retrogressive structure for this armature, is 500,000 lines. Calculate the speed for
this machine in order that its generated emf be 220 V.
P = Number of Poles a) 2,750 rpm* b) 2,550 rpm c) 2,250 rpm d) 2,000 rpm
Nb = P ( lap winding ) hint: z = 48 (10) (2) = 960 conductors multiply by two kay a = mP =
 = Flux per pole in Weber 8 so in every pole 2 parallel paths or two conductors per element
–8
( 1 Maxwell = 1 x 10 Wb ) Nb = Number of brushes 5. When a generator is being driven at 1,200 rpm, the generated emf
(i) number, sizePand
= connection
No. of poles of armature coils. is should operate
125 volts. with
What will be field resistance
the generated emfappreciably below
if the field flux is
Z =condition.
unstable Total number
For of conductors
this reason, a series generator the critical value.
decreased by 12% withIfthe
thespeed
field increased
circuit resistance is more
to 1,800 rpm?
= Number of slots x no. of conductors per slot b)
has very limited applications. (ii) wave winding
contact – ( for high
resistance voltage,
between thelowcarbon
currentbrush
generator
and). a)than
135 Vthe critical
b) 145field
V resistance,c) 155the
V generator willV*
d) 165 fail to
The finish
the copper commutator. of the coil is connected to the build
hint: φ2 =up( 1
any voltage.
– 0.2 ) φ1
21. Upon N = Rotational
what or armature
factors the speed
armature in rpm
resistance (Ra) of start of another coil away from the first coil.
a d.c. machine depends? 22. Why is the resistance of the field winding of a d.c. 23. Why does the field winding of a series d.c.
shunt generator kept low? machine have less number of turns than that of
The armature resistance of a d.c. machine depends d.c. shunt machine?
upon: For satisfactory working (shunt generator) , the
machine The resistance of the shunt field winding is large so that
FRANCISCAN ENGINEERING REVIEW PROGRAM ELECTRICAL
ELECTRICAL ENGINEERING
ENGINEERING - DC (MACHINES
- DC MACHINES GENERATOR / MOTOR) SEPTEMBER
SUMMER 2019 2020

a = Number of parallel paths in the armature

GENERATOR a = m P ( if simplex lap winding ) Z  2m y  yf
- A machine that converts the inter – action of mechanical energy a = 2 m ( if simplex wave winding ) y y b
and magnetic energy into electrical energy. P 2
- A dynmo is an example of simple generator . m = multiplicity
m = 1 ( if simplex ) , m = 2 ( if duplex )
y = Average pitch
Mech’l Elect’l
Magnetism PARTS OF A DC MACHINE ( GENERATOR ) Z = no. of winding elements on the surface
Input Output of armature core
1. Stationary part - Produces magnetic flux
Generator Nb = 2 ( wave winding )
2. Rotating part
FARADAY’S LAW OF ELECTROMAGNETIC INDUCTION - Armature responsible of converting mechanical energy into
electrical energy
“ Whenever a conductor cuts magnetic flux, dynamically it induces Sample Problems
an emf “ according to the formula TYPES OF ARMATURE WINDINGS
- Armature windings usually uses closed coil type than the open 1. A 4 pole, lap – wound dc armature, the back pitch is 17, if the
coil type. There are two types of closed coil type namely : winding is progressive what is the front pitch ?
a) 32 b) 15 *
1. Ring winding c) 17 d) 13
PNZ
E  =kN 2. Drum winding 2. A 4 pole dc generator with duplex lap winding has 48 slots and
60 a a) lap winding – ( for low voltage, high current generator ). The four element per slot. The flux per pole is 2.5 x 106 maxwells and
finish of each coil is connected to the start of it runs at 1,500 rpm. What is the output voltage ?
the next coil so the winding pitch or a) 60 volts * b) 360 volts
Comparison of emf formula: commutator pitch is unity or one. c) 225 volts d) 120 volts
3. A 4-pole wave wound dc generator has 50 slots and 24 conductors
yb  y f  2m
E2 N  per slot. The flux per pole is 10 mWb. Determine the induced emf in
= 2 2
E1 N1 1 the armature, it it is rotating at a speed of 600 rpm.
a) 240 V* b) 230 V c) 220 V d) 210 V
yb = back pitch ( should be an odd. no. )
yf = front pitch ( should be an odd. no. ) 4. A 4-pole, simplex lap wound, direct current armature has 48 slots
Where : E = generated or induced emf per parallel path + = if the winding is progressive containing 48 coils, each of 10 turns. The flux per pole in the field
E  K N  ( if P , Z and a is considered constants ) - = if the winding is retrogressive structure for this armature, is 500,000 lines. Calculate the speed for
this machine in order that its generated emf be 220 V.
P = Number of Poles a) 2,750 rpm* b) 2,550 rpm c) 2,250 rpm d) 2,000 rpm
Nb = P ( lap winding ) hint: z = 48 (10) (2) = 960 conductors multiply by two kay a = mP =
 = Flux per pole in Weber 8 so in every pole 2 parallel paths or two conductors per element
–8
( 1 Maxwell = 1 x 10 Wb ) Nb = Number of brushes 5. When a generator is being driven at 1,200 rpm, the generated emf
current in the winding is small compared to the rated P = No.
24. What is the necessity ofofapoles
compound generator? is In
125a volts.
compound generator,
What will both series
be the generated emf if and shunt
the field flux is
Z current
armature = Total number of conductors
of the machine. To produce the windingsbyare placed onspeed
each increased
field pole.toThe series
decreased 12% with the 1,800 rpm?
= Number of slots x no. of conductors per slot In practice,
b) power
wave winding – ( circuits require low
for high voltage, a constant voltage,).
current generator
necessary e.m.f. the winding consist of many turns. The a)winding
135 V is sob)connected
145 V thatc)flux
155 produced
V by it aids
d) 165 V*
resistance of the series field winding is made as low as especially lighting circuits.
The finishShunt andisseries
of the coil generators
connected to the theφ2flux
hint: = ( by
1 –shunt
0.2 ) φwinding.
1 The generator so connected
N = Rotational or armature speed in rpm start of
cannot be used in such another coilAsaway
situations. the from
loadthe first coil.
current
possible so that voltage drop across the winding is is said to be commutatively-compounded. As the load
minimum. To produce the same flux at rated of a generator increases, its terminal voltages falls. In current increases, the flux produced by the series
conditions, the turns of a series winding are fewer than the series generator, on the other hand , an increase in winding compensates for the loss of flux due to
those of a shunt winding since the series winding the load current is accompanied by rise in the terminal armature reaction. Consequently, the terminal voltage
carries the rated current of the machine. voltage. of the generator remains constant.
FRANCISCAN ENGINEERING REVIEW PROGRAM ELECTRICAL
ELECTRICAL ENGINEERING
ENGINEERING - DC (MACHINES
- DC MACHINES GENERATOR / MOTOR) SEPTEMBER
SUMMER 2019 2020

a = Number of parallel paths in the armature

GENERATOR a = m P ( if simplex lap winding ) Z  2m y  yf
- A machine that converts the inter – action of mechanical energy a = 2 m ( if simplex wave winding ) y y b
and magnetic energy into electrical energy. P 2
- A dynmo is an example of simple generator . m = multiplicity
m = 1 ( if simplex ) , m = 2 ( if duplex )
y = Average pitch
Mech’l Elect’l
Magnetism PARTS OF A DC MACHINE ( GENERATOR ) Z = no. of winding elements on the surface
Input Output of armature core
1. Stationary part - Produces magnetic flux
Generator Nb = 2 ( wave winding )
2. Rotating part
FARADAY’S LAW OF ELECTROMAGNETIC INDUCTION - Armature responsible of converting mechanical energy into
electrical energy
“ Whenever a conductor cuts magnetic flux, dynamically it induces Sample Problems
an emf “ according to the formula TYPES OF ARMATURE WINDINGS
- Armature windings usually uses closed coil type than the open 1. A 4 pole, lap – wound dc armature, the back pitch is 17, if the
coil type. There are two types of closed coil type namely : winding is progressive what is the front pitch ?
a) 32 b) 15 *
1. Ring winding c) 17 d) 13
PNZ
E  =kN 2. Drum winding 2. A 4 pole dc generator with duplex lap winding has 48 slots and
60 a a) lap winding – ( for low voltage, high current generator ). The four element per slot. The flux per pole is 2.5 x 106 maxwells and
finish of each coil is connected to the start of it runs at 1,500 rpm. What is the output voltage ?
the next coil so the winding pitch or a) 60 volts * b) 360 volts
Comparison of emf formula: commutator pitch is unity or one. c) 225 volts d) 120 volts
3. A 4-pole wave wound dc generator has 50 slots and 24 conductors
yb  y f  2m
E2 N  per slot. The flux per pole is 10 mWb. Determine the induced emf in
= 2 2
E1 N1 1 the armature, it it is rotating at a speed of 600 rpm.
a) 240 V* b) 230 V c) 220 V d) 210 V
yb = back pitch ( should be an odd. no. )
yf = front pitch ( should be an odd. no. ) 4. A 4-pole, simplex lap wound, direct current armature has 48 slots
Where : E = generated or induced emf per parallel path + = if the winding is progressive containing 48 coils, each of 10 turns. The flux per pole in the field
E  K N  ( if P , Z and a is considered constants ) - = if the winding is retrogressive structure for this armature, is 500,000 lines. Calculate the speed for
this machine in order that its generated emf be 220 V.
P = Number of Poles a) 2,750 rpm* b) 2,550 rpm c) 2,250 rpm d) 2,000 rpm
Nb = P ( lap winding ) hint: z = 48 (10) (2) = 960 conductors multiply by two kay a = mP =
 = Flux per pole in Weber 8 so in every pole 2 parallel paths or two conductors per element
–8
( 1 Maxwell = 1 x 10 Wb ) Nb = Number of brushes 5. When a generator is being driven at 1,200 rpm, the generated emf
25. Why do we use over-compounded generators in P = No. of poles
winding of the commulatively compounded generator is As
125the load
volts. on will
What a generator changes
be the generated emfsuddenly, the is
if the field flux
Z stations?
power = Total number of conductors so armature
decreased byreaction
12% withcauses severe
the speed distortion
increased to 1,800of rpm?
flux in the
= Number of slots x no. of conductors per slot b)
thatwave winding – voltage
the terminal ( for highincreases
voltage, low
ascurrent generator
the load current). a)air-gap.
135 V Thisb)causes
145 V irregular c) voltage
155 V distributiond) 165 V*
In power stations, there is a considerable distance The finish of the coil is
rises. Such a generator is called over-compoundedconnected to the around
hint: φ2 = (the
1 – commutator.
0.2 ) φ1 The high value of voltage
N = Rotational or armature speed in rpm start of another coil away from the first coil.
between the generator and the load. We have to generator and compensates for the voltage drop in the between segments over a portion of the commutator
compensate not only for armature reaction and the line to maintain constant voltage at the load terminals. may cause flash-over, particularly in high voltages
armature voltage drop, but also for IR drop in the line machines where the average voltage per segment is
between the generator and the load. In such 26. How does sudden changes of load in a d.c. necessarily high.
situations, we place a few additional turns on the series machine cause “flash over” ?
27. What does the name plate of a d.c. generator
FRANCISCAN ENGINEERING REVIEW PROGRAM ELECTRICAL
ELECTRICAL ENGINEERING
ENGINEERING - DC (MACHINES
- DC MACHINES GENERATOR / MOTOR) SEPTEMBER
SUMMER 2019 2020

a = Number of parallel paths in the armature

GENERATOR a = m P ( if simplex lap winding ) Z  2m y  yf
- A machine that converts the inter – action of mechanical energy a = 2 m ( if simplex wave winding ) y y b
and magnetic energy into electrical energy. P 2
- A dynmo is an example of simple generator . m = multiplicity
m = 1 ( if simplex ) , m = 2 ( if duplex )
y = Average pitch
Mech’l Elect’l
Magnetism PARTS OF A DC MACHINE ( GENERATOR ) Z = no. of winding elements on the surface
Input Output of armature core
1. Stationary part - Produces magnetic flux
Generator Nb = 2 ( wave winding )
2. Rotating part
FARADAY’S LAW OF ELECTROMAGNETIC INDUCTION - Armature responsible of converting mechanical energy into
electrical energy
“ Whenever a conductor cuts magnetic flux, dynamically it induces Sample Problems
an emf “ according to the formula TYPES OF ARMATURE WINDINGS
- Armature windings usually uses closed coil type than the open 1. A 4 pole, lap – wound dc armature, the back pitch is 17, if the
coil type. There are two types of closed coil type namely : winding is progressive what is the front pitch ?
a) 32 b) 15 *
1. Ring winding c) 17 d) 13
PNZ
E  =kN 2. Drum winding 2. A 4 pole dc generator with duplex lap winding has 48 slots and
60 a a) lap winding – ( for low voltage, high current generator ). The four element per slot. The flux per pole is 2.5 x 106 maxwells and
finish of each coil is connected to the start of it runs at 1,500 rpm. What is the output voltage ?
the next coil so the winding pitch or a) 60 volts * b) 360 volts
Comparison of emf formula: commutator pitch is unity or one. c) 225 volts d) 120 volts
3. A 4-pole wave wound dc generator has 50 slots and 24 conductors
yb  y f  2m
E2 N  per slot. The flux per pole is 10 mWb. Determine the induced emf in
= 2 2
E1 N1 1 the armature, it it is rotating at a speed of 600 rpm.
a) 240 V* b) 230 V c) 220 V d) 210 V
yb = back pitch ( should be an odd. no. )
yf = front pitch ( should be an odd. no. ) 4. A 4-pole, simplex lap wound, direct current armature has 48 slots
Where : E = generated or induced emf per parallel path + = if the winding is progressive containing 48 coils, each of 10 turns. The flux per pole in the field
E  K N  ( if P , Z and a is considered constants ) - = if the winding is retrogressive structure for this armature, is 500,000 lines. Calculate the speed for
this machine in order that its generated emf be 220 V.
P = Number of Poles a) 2,750 rpm* b) 2,550 rpm c) 2,250 rpm d) 2,000 rpm
Nb = P ( lap winding ) hint: z = 48 (10) (2) = 960 conductors multiply by two kay a = mP =
 = Flux per pole in Weber 8 so in every pole 2 parallel paths or two conductors per element
–8
( 1 Maxwell = 1 x 10 Wb ) Nb = Number of brushes 5. When a generator is being driven at 1,200 rpm, the generated emf
generally indicate? P = satisfactorily
machine will perform No. of poles during a long is 125 volts. What will be the generated emf if the field flux is
Z = Total number of conductors machine life if operated under the limits and conditions If a d.c. by
machine is the
operated at a speed belowrpm?
the rated
decreased 12% with speed increased to 1,800
The name =plate
Number
of aofd.c
slots x no. of conductors
generator generally per slot
indicates: b) wave winding
specified on the – ( for high voltage,
nameplate. It must lownot
current generatorthat
be inferred ). a)value,
135 V the machine
b) 145 V may be c) overheated
155 V due d)
to165
: V*
(i) output in kW (ii) output voltage The finish of the coil is
the machine cannot be operated under conditions connected to the (i) φ2increased
hint: = ( 1 – 0.2field
) φ1 current necessary to produce rated
N = Rotational or(iv)
(iii) speed armature speed intemperature
permissible rpm rise start of another coil away from the first coil.
different from those on the nameplate. However, voltage.
28. Can a d.c. machine be operated under conditions operation that exceeds any of the nameplate ratings (ii) decrease in fanning action because of decrease in
different from those on the name plate? may result in premature failure of the machine. speed.

The nameplate values of a generator imply that the 29. What happens if a d.c. machine is operated at a 30. How does higher permeability of magnetic
speed below the rated speed. material of a d.c. machine affect its performance?
FRANCISCAN ENGINEERING REVIEW PROGRAM ELECTRICAL
ELECTRICAL ENGINEERING
ENGINEERING - DC (MACHINES
- DC MACHINES GENERATOR / MOTOR) SEPTEMBER
SUMMER 2019 2020

a = Number of parallel paths in the armature

GENERATOR a = m P ( if simplex lap winding ) Z  2m y  yf
- A machine that converts the inter – action of mechanical energy a = 2 m ( if simplex wave winding ) y y b
and magnetic energy into electrical energy. P 2
- A dynmo is an example of simple generator . m = multiplicity
m = 1 ( if simplex ) , m = 2 ( if duplex )
y = Average pitch
Mech’l Elect’l
Magnetism PARTS OF A DC MACHINE ( GENERATOR ) Z = no. of winding elements on the surface
Input Output of armature core
1. Stationary part - Produces magnetic flux
Generator Nb = 2 ( wave winding )
2. Rotating part
FARADAY’S LAW OF ELECTROMAGNETIC INDUCTION - Armature responsible of converting mechanical energy into
electrical energy
“ Whenever a conductor cuts magnetic flux, dynamically it induces Sample Problems
an emf “ according to the formula TYPES OF ARMATURE WINDINGS
- Armature windings usually uses closed coil type than the open 1. A 4 pole, lap – wound dc armature, the back pitch is 17, if the
coil type. There are two types of closed coil type namely : winding is progressive what is the front pitch ?
a) 32 b) 15 *
1. Ring winding c) 17 d) 13
PNZ
E  =kN 2. Drum winding 2. A 4 pole dc generator with duplex lap winding has 48 slots and
60 a a) lap winding – ( for low voltage, high current generator ). The four element per slot. The flux per pole is 2.5 x 106 maxwells and
finish of each coil is connected to the start of it runs at 1,500 rpm. What is the output voltage ?
the next coil so the winding pitch or a) 60 volts * b) 360 volts
Comparison of emf formula: commutator pitch is unity or one. c) 225 volts d) 120 volts
3. A 4-pole wave wound dc generator has 50 slots and 24 conductors
yb  y f  2m
E2 N  per slot. The flux per pole is 10 mWb. Determine the induced emf in
= 2 2
E1 N1 1 the armature, it it is rotating at a speed of 600 rpm.
a) 240 V* b) 230 V c) 220 V d) 210 V
yb = back pitch ( should be an odd. no. )
yf = front pitch ( should be an odd. no. ) 4. A 4-pole, simplex lap wound, direct current armature has 48 slots
Where : E = generated or induced emf per parallel path + = if the winding is progressive containing 48 coils, each of 10 turns. The flux per pole in the field
E  K N  ( if P , Z and a is considered constants ) - = if the winding is retrogressive structure for this armature, is 500,000 lines. Calculate the speed for
this machine in order that its generated emf be 220 V.
P = Number of Poles a) 2,750 rpm* b) 2,550 rpm c) 2,250 rpm d) 2,000 rpm
Nb = P ( lap winding ) hint: z = 48 (10) (2) = 960 conductors multiply by two kay a = mP =
 = Flux per pole in Weber 8 so in every pole 2 parallel paths or two conductors per element
–8
( 1 Maxwell = 1 x 10 Wb ) Nb = Number of brushes 5. When a generator is being driven at 1,200 rpm, the generated emf
machine? P = No. of poles is 125 volts. What will be the generated emf if the field flux is
If the permeability of the of
Z = Total number magnetic material is large, a
conductors 32. How will you show that the same power output, a
decreased by 12% with the speed increased to 1,800 rpm?
high value =of Number of slots
flux density x no.
can beofestablished.
conductors per slot
A higher The wave
b) design of a d.c.
winding machine
– ( for can be
high voltage, lowimproved by one).
current generator low-speed
a) 135 V b)machine
145 V is always
c) 155 bigger
V than a high-
d) 165 V*
flux density will allow less armature coil turns for the of The finish of the coil is connected to the speed machine?
hint: φ2 = ( 1 – 0.2 ) φ1
N = Rotational
same performance. or armature
This speedininlower
would result rpm winding the following two waysstart of
: another coil away from the first coil.
resistance and at the same time less coil inductance. (i) By using a low-cost winding material with less Suppose we have a 100 kW, 250 V, 2000 rpm
Both results are highly beneficial in reducing losses and resistance than copper. Of the pure metals, only generator. Now, it is desired to build another generator
improving commutation. silver has a lower resistivity. having the same power and voltage, but running at half
(ii) By using a low-cost magnetic material with a higher the speed.
31. How can you improve the design of a d.c. permeability than present magnetic material.
FRANCISCAN ENGINEERING REVIEW PROGRAM ELECTRICAL
ELECTRICAL ENGINEERING
ENGINEERING - DC (MACHINES
- DC MACHINES GENERATOR / MOTOR) SEPTEMBER
SUMMER 2019 2020

a = Number of parallel paths in the armature

GENERATOR a = m P ( if simplex lap winding ) Z  2m y  yf
- A machine that converts the inter – action of mechanical energy a = 2 m ( if simplex wave winding ) y y b
and magnetic energy into electrical energy. P 2
- A dynmo is an example of simple generator . m = multiplicity
m = 1 ( if simplex ) , m = 2 ( if duplex )
y = Average pitch
Mech’l Elect’l
Magnetism PARTS OF A DC MACHINE ( GENERATOR ) Z = no. of winding elements on the surface
Input Output of armature core
1. Stationary part - Produces magnetic flux
Generator Nb = 2 ( wave winding )
2. Rotating part
FARADAY’S LAW OF ELECTROMAGNETIC INDUCTION - Armature responsible of converting mechanical energy into
electrical energy
“ Whenever a conductor cuts magnetic flux, dynamically it induces Sample Problems
an emf “ according to the formula TYPES OF ARMATURE WINDINGS
- Armature windings usually uses closed coil type than the open 1. A 4 pole, lap – wound dc armature, the back pitch is 17, if the
coil type. There are two types of closed coil type namely : winding is progressive what is the front pitch ?
a) 32 b) 15 *
1. Ring winding c) 17 d) 13
PNZ
E  =kN 2. Drum winding 2. A 4 pole dc generator with duplex lap winding has 48 slots and
60 a a) lap winding – ( for low voltage, high current generator ). The four element per slot. The flux per pole is 2.5 x 106 maxwells and
finish of each coil is connected to the start of it runs at 1,500 rpm. What is the output voltage ?
the next coil so the winding pitch or a) 60 volts * b) 360 volts
Comparison of emf formula: commutator pitch is unity or one. c) 225 volts d) 120 volts
3. A 4-pole wave wound dc generator has 50 slots and 24 conductors
yb  y f  2m
E2 N  per slot. The flux per pole is 10 mWb. Determine the induced emf in
= 2 2
E1 N1 1 the armature, it it is rotating at a speed of 600 rpm.
a) 240 V* b) 230 V c) 220 V d) 210 V
yb = back pitch ( should be an odd. no. )
yf = front pitch ( should be an odd. no. ) 4. A 4-pole, simplex lap wound, direct current armature has 48 slots
Where : E = generated or induced emf per parallel path + = if the winding is progressive containing 48 coils, each of 10 turns. The flux per pole in the field
E  K N  ( if P , Z and a is considered constants ) - = if the winding is retrogressive structure for this armature, is 500,000 lines. Calculate the speed for
this machine in order that its generated emf be 220 V.
P = Number of Poles a) 2,750 rpm* b) 2,550 rpm c) 2,250 rpm d) 2,000 rpm
Nb = P ( lap winding ) hint: z = 48 (10) (2) = 960 conductors multiply by two kay a = mP =
 = Flux per pole in Weber 8 so in every pole 2 parallel paths or two conductors per element
–8
( 1 Maxwell = 1 x 10 Wb ) Nb = Number of brushes 5. When a generator is being driven at 1,200 rpm, the generated emf
To generate the same voltage at half the speed, we 33. What are two mainP = requirements
No. of poles to be met while is 125 volts. What will be the generated emf if the field flux is
either Zhave
= to
Total number
double theofnumber
conductors
of conductors on the connecting shunt generators in parallel? (ii) The terminal voltages of the machines being
decreased by 12% with the speed increased to 1,800 rpm?
= Number of slots x no. of conductors per slot
armature, or double the flux from the poles. b) wave winding – ( for high voltage, low current generator ). a) 135 paralleled
V must
b) 145 V be the same.
c) 155 V d) 165 V*
Consequently, we must either increase the size of the The finish
The following two main of the coil isare
requirements connected to the
to be met hint: φ = ( 1 – 0.2 ) φ
N = Rotational or armature speed in rpm start of another coil away from the first coil. 34. How will you disconnect one of the two shunt
2 1
armature or increase the size of the poles. In practice, while connecting shut generators in parallel : generators operating in parallel?
we increase both. It follows, therefore, that for a given
power output, a low-speed machine is always bigger (i) The positive terminals of all the machines must be In order to disconnect one of the two shunt generators
than a high-speed machine. This is true for the both d.c. connected to the positive bus-bar and the negative operating in parallel, the following procedure is adopted
and a.c. machines. terminals must be connected to the negative bus-
bar.
FRANCISCAN ENGINEERING REVIEW PROGRAM ELECTRICAL
ELECTRICAL ENGINEERING
ENGINEERING - DC (MACHINES
- DC MACHINES GENERATOR / MOTOR) SEPTEMBER
SUMMER 2019 2020

a = Number of parallel paths in the armature

GENERATOR a = m P ( if simplex lap winding ) Z  2m y  yf
- A machine that converts the inter – action of mechanical energy a = 2 m ( if simplex wave winding ) y y b
and magnetic energy into electrical energy. P 2
- A dynmo is an example of simple generator . m = multiplicity
m = 1 ( if simplex ) , m = 2 ( if duplex )
y = Average pitch
Mech’l Elect’l
Magnetism PARTS OF A DC MACHINE ( GENERATOR ) Z = no. of winding elements on the surface
Input Output of armature core
1. Stationary part - Produces magnetic flux
Generator Nb = 2 ( wave winding )
2. Rotating part
FARADAY’S LAW OF ELECTROMAGNETIC INDUCTION - Armature responsible of converting mechanical energy into
electrical energy
“ Whenever a conductor cuts magnetic flux, dynamically it induces Sample Problems
an emf “ according to the formula TYPES OF ARMATURE WINDINGS
- Armature windings usually uses closed coil type than the open 1. A 4 pole, lap – wound dc armature, the back pitch is 17, if the
coil type. There are two types of closed coil type namely : winding is progressive what is the front pitch ?
a) 32 b) 15 *
1. Ring winding c) 17 d) 13
PNZ
E  =kN 2. Drum winding 2. A 4 pole dc generator with duplex lap winding has 48 slots and
60 a a) lap winding – ( for low voltage, high current generator ). The four element per slot. The flux per pole is 2.5 x 106 maxwells and
finish of each coil is connected to the start of it runs at 1,500 rpm. What is the output voltage ?
the next coil so the winding pitch or a) 60 volts * b) 360 volts
Comparison of emf formula: commutator pitch is unity or one. c) 225 volts d) 120 volts
3. A 4-pole wave wound dc generator has 50 slots and 24 conductors
yb  y f  2m
E2 N  per slot. The flux per pole is 10 mWb. Determine the induced emf in
= 2 2
E1 N1 1 the armature, it it is rotating at a speed of 600 rpm.
a) 240 V* b) 230 V c) 220 V d) 210 V
yb = back pitch ( should be an odd. no. )
yf = front pitch ( should be an odd. no. ) 4. A 4-pole, simplex lap wound, direct current armature has 48 slots
Where : E = generated or induced emf per parallel path + = if the winding is progressive containing 48 coils, each of 10 turns. The flux per pole in the field
E  K N  ( if P , Z and a is considered constants ) - = if the winding is retrogressive structure for this armature, is 500,000 lines. Calculate the speed for
this machine in order that its generated emf be 220 V.
P = Number of Poles a) 2,750 rpm* b) 2,550 rpm c) 2,250 rpm d) 2,000 rpm
Nb = P ( lap winding ) hint: z = 48 (10) (2) = 960 conductors multiply by two kay a = mP =
 = Flux per pole in Weber 8 so in every pole 2 parallel paths or two conductors per element
–8
( 1 Maxwell = 1 x 10 Wb ) Nb = Number of brushes 5. When a generator is being driven at 1,200 rpm, the generated emf
(i) The load of the generator to be disconnected is P = No.instead
generators in parallel of poles of a single large variable.
is 125 volts. What As
will machines operate
be the generated emfatif greatest
the field flux is
Z = over
shifted Total to
number of conductors
the other by gradually reducing its shunt generator. Why? efficiency
decreased by 12% at
withorthe
near full-load
speed it istopossible
increased 1,800 rpm?with
= Number of slots x no. of conductors per slot b) wave winding – ( for high voltage, low current generator ).
field current and increasing the field current of the a) 135 Vseveralb)machines
145 V to keep each
c) 155 V machine d)either
165 V*fully
other generator. The
It is generally more finish of the
desirable in acoil is connected
generating to the to
station hint: φ2 loaded or shut
= ( 1 – 0.2 ) φ1 down entirely.
N = Rotational or armature speed in rpm start of another coil away from the first coil.
have several small generators that may be paralleled (ii) A generator that breaks down may be removed
(ii) When the current output of the machine to be than to have one large generator to supply all the from the circuit for repairs without interrupting the
disconnected is reduced almost to zero, the main load. power supply.
switch is opened. This is due to the following reasons :
(i) The load supplied by a generating station is usually (iii) Generators may be added to the system as the
35. In a power station, we have several shunt power demand increases.
FRANCISCAN ENGINEERING REVIEW PROGRAM ELECTRICAL
ELECTRICAL ENGINEERING
ENGINEERING - DC (MACHINES
- DC MACHINES GENERATOR / MOTOR) SEPTEMBER
SUMMER 2019 2020

a = Number of parallel paths in the armature

GENERATOR a = m P ( if simplex lap winding ) Z  2m y  yf
- A machine that converts the inter – action of mechanical energy a = 2 m ( if simplex wave winding ) y y b
and magnetic energy into electrical energy. P 2
- A dynmo is an example of simple generator . m = multiplicity
m = 1 ( if simplex ) , m = 2 ( if duplex )
y = Average pitch
Mech’l Elect’l
Magnetism PARTS OF A DC MACHINE ( GENERATOR ) Z = no. of winding elements on the surface
Input Output of armature core
1. Stationary part - Produces magnetic flux
Generator Nb = 2 ( wave winding )
2. Rotating part
FARADAY’S LAW OF ELECTROMAGNETIC INDUCTION - Armature responsible of converting mechanical energy into
electrical energy
“ Whenever a conductor cuts magnetic flux, dynamically it induces Sample Problems
an emf “ according to the formula TYPES OF ARMATURE WINDINGS
- Armature windings usually uses closed coil type than the open 1. A 4 pole, lap – wound dc armature, the back pitch is 17, if the
coil type. There are two types of closed coil type namely : winding is progressive what is the front pitch ?
a) 32 b) 15 *
1. Ring winding c) 17 d) 13
PNZ
E  =kN 2. Drum winding 2. A 4 pole dc generator with duplex lap winding has 48 slots and
60 a a) lap winding – ( for low voltage, high current generator ). The four element per slot. The flux per pole is 2.5 x 106 maxwells and
finish of each coil is connected to the start of it runs at 1,500 rpm. What is the output voltage ?
the next coil so the winding pitch or a) 60 volts * b) 360 volts
Comparison of emf formula: commutator pitch is unity or one. c) 225 volts d) 120 volts
3. A 4-pole wave wound dc generator has 50 slots and 24 conductors
yb  y f  2m
E2 N  per slot. The flux per pole is 10 mWb. Determine the induced emf in
= 2 2
E1 N1 1 the armature, it it is rotating at a speed of 600 rpm.
a) 240 V* b) 230 V c) 220 V d) 210 V
yb = back pitch ( should be an odd. no. )
yf = front pitch ( should be an odd. no. ) 4. A 4-pole, simplex lap wound, direct current armature has 48 slots
Where : E = generated or induced emf per parallel path + = if the winding is progressive containing 48 coils, each of 10 turns. The flux per pole in the field
E  K N  ( if P , Z and a is considered constants ) - = if the winding is retrogressive structure for this armature, is 500,000 lines. Calculate the speed for
this machine in order that its generated emf be 220 V.
P = Number of Poles a) 2,750 rpm* b) 2,550 rpm c) 2,250 rpm d) 2,000 rpm
Nb = P ( lap winding ) hint: z = 48 (10) (2) = 960 conductors multiply by two kay a = mP =
 = Flux per pole in Weber 8 so in every pole 2 parallel paths or two conductors per element
–8
( 1 Maxwell = 1 x 10 Wb ) Nb = Number of brushes 5. When a generator is being driven at 1,200 rpm, the generated emf
P (ii)
(i) shunt field loss = No. of poles
series field loss determined
is 125 volts. What bywill direct loading?emf if the field flux is
be the generated
36. WhichZ losses
= Total number
occur of d.c.
in a conductors
generator? (iii) interpole loss decreased by 12% with the speed increased to 1,800 rpm?
= Number of slots x no. of conductors per slot b) wave winding – ( for high voltage, low current generator ). a)It is V
135 wastefulb)and145 difficult
V toc)measure
155 V the input and
d) 165 V*
The losses of a d.c. generator consist of (i) copper Mechanical losses :The finish of the coil is connected to the output
hint: φ2 = of
( 1 a– d.c.
0.2 ) generator
φ1 by direct loading, especially in
N = Rotational or armature speed in rpm start of another coil away from the first coil.
losses in the electric circuit (ii) mechanical losses due to A. Iron losses larger sizes. In practice, losses of the generator are
the rotation of the machine. (i) eddy current loss (ii) hysteresis loss measured and efficiency found from the following
relation
Copper Losses : B. Friction losses
A. Armature copper loss ( Ia2 Ra )
B. Field losses 37. Why is the efficiency of a d.c. machine not
FRANCISCAN ENGINEERING REVIEW PROGRAM ELECTRICAL
ELECTRICAL ENGINEERING
ENGINEERING - DC (MACHINES
- DC MACHINES GENERATOR / MOTOR) SEPTEMBER
SUMMER 2019 2020

a = Number of parallel paths in the armature

GENERATOR a = m P ( if simplex lap winding ) Z  2m y  yf
- A machine that converts the inter – action of mechanical energy a = 2 m ( if simplex wave winding ) y y b
and magnetic energy into electrical energy. P 2
- A dynmo is an example of simple generator . m = multiplicity
m = 1 ( if simplex ) , m = 2 ( if duplex )
y = Average pitch
Mech’l Elect’l
Magnetism PARTS OF A DC MACHINE ( GENERATOR ) Z = no. of winding elements on the surface
Input Output of armature core
1. Stationary part - Produces magnetic flux
Generator Nb = 2 ( wave winding )
2. Rotating part
FARADAY’S LAW OF ELECTROMAGNETIC INDUCTION - Armature responsible of converting mechanical energy into
electrical energy
“ Whenever a conductor cuts magnetic flux, dynamically it induces Sample Problems
an emf “ according to the formula TYPES OF ARMATURE WINDINGS
- Armature windings usually uses closed coil type than the open 1. A 4 pole, lap – wound dc armature, the back pitch is 17, if the
coil type. There are two types of closed coil type namely : winding is progressive what is the front pitch ?
a) 32 b) 15 *
1. Ring winding c) 17 d) 13
PNZ
E  =kN 2. Drum winding 2. A 4 pole dc generator with duplex lap winding has 48 slots and
60 a a) lap winding – ( for low voltage, high current generator ). The four element per slot. The flux per pole is 2.5 x 106 maxwells and
finish of each coil is connected to the start of it runs at 1,500 rpm. What is the output voltage ?
the next coil so the winding pitch or a) 60 volts * b) 360 volts
Comparison of emf formula: commutator pitch is unity or one. c) 225 volts d) 120 volts
3. A 4-pole wave wound dc generator has 50 slots and 24 conductors
yb  y f  2m
E2 N  per slot. The flux per pole is 10 mWb. Determine the induced emf in
= 2 2
E1 N1 1 the armature, it it is rotating at a speed of 600 rpm.
a) 240 V* b) 230 V c) 220 V d) 210 V
yb = back pitch ( should be an odd. no. )
yf = front pitch ( should be an odd. no. ) 4. A 4-pole, simplex lap wound, direct current armature has 48 slots
Where : E = generated or induced emf per parallel path + = if the winding is progressive containing 48 coils, each of 10 turns. The flux per pole in the field
E  K N  ( if P , Z and a is considered constants ) - = if the winding is retrogressive structure for this armature, is 500,000 lines. Calculate the speed for
this machine in order that its generated emf be 220 V.
P = Number of Poles a) 2,750 rpm* b) 2,550 rpm c) 2,250 rpm d) 2,000 rpm
Nb = P ( lap winding ) hint: z = 48 (10) (2) = 960 conductors multiply by two kay a = mP =
 = Flux per pole in Weber 8 so in every pole 2 parallel paths or two conductors per element
–8
( 1 Maxwell = 1 x 10 Wb ) Nb = Number of brushes 5. When a generator is being driven at 1,200 rpm, the generated emf
output output P = No. of poles is 125 volts. What will be the generated emf if the field flux is
Efficiency  of conductors
Z == Total number
decreased by 12% with the speed increased to 1,800 rpm?
= Number of slots x no.oflosses
input output conductors per slot b) wave winding – ( for high voltage, low current generator ). a) 135 V b) 145 V c) 155 V d) 165 V*
The finish of the coil is connected to the hint: φ2 = ( 1 – 0.2 ) φ1
N = Rotational or armature speed in rpm start of another coil away from the first coil.
FRANCISCAN ENGINEERING REVIEW PROGRAM ELECTRICAL
ELECTRICAL ENGINEERING
ENGINEERING - DC (MACHINES
- DC MACHINES GENERATOR / MOTOR) SEPTEMBER
SUMMER 2019 2020

a = Number of parallel paths in the armature

GENERATOR a = m P ( if simplex lap winding ) Z  2m y  yf
- A machine that converts the inter – action of mechanical energy a = 2 m ( if simplex wave winding ) y y b
and magnetic energy into electrical energy. P 2
- A dynmo is an example of simple generator . m = multiplicity
m = 1 ( if simplex ) , m = 2 ( if duplex )
y = Average pitch
Mech’l Elect’l
Magnetism PARTS OF A DC MACHINE ( GENERATOR ) Z = no. of winding elements on the surface
Input Output of armature core
1. Stationary part - Produces magnetic flux
Generator Nb = 2 ( wave winding )
2. Rotating part
FARADAY’S LAW OF ELECTROMAGNETIC INDUCTION - Armature responsible of converting mechanical energy into
electrical energy
“ Whenever a conductor cuts magnetic flux, dynamically it induces Sample Problems
an emf “ according to the formula TYPES OF ARMATURE WINDINGS
- Armature windings usually uses closed coil type than the open 1. A 4 pole, lap – wound dc armature, the back pitch is 17, if the
coil type. There are two types of closed coil type namely : winding is progressive what is the front pitch ?
a) 32 b) 15 *
1. Ring winding c) 17 d) 13
PNZ
E  =kN 2. Drum winding 2. A 4 pole dc generator with duplex lap winding has 48 slots and
60 a a) lap winding – ( for low voltage, high current generator ). The four element per slot. The flux per pole is 2.5 x 106 maxwells and
finish of each coil is connected to the start of it runs at 1,500 rpm. What is the output voltage ?
the next coil so the winding pitch or a) 60 volts * b) 360 volts
Comparison of emf formula: commutator pitch is unity or one. c) 225 volts d) 120 volts
3. A 4-pole wave wound dc generator has 50 slots and 24 conductors
yb  y f  2m
E2 N  per slot. The flux per pole is 10 mWb. Determine the induced emf in
= 2 2
E1 N1 1 the armature, it it is rotating at a speed of 600 rpm.
a) 240 V* b) 230 V c) 220 V d) 210 V
yb = back pitch ( should be an odd. no. )
yf = front pitch ( should be an odd. no. ) 4. A 4-pole, simplex lap wound, direct current armature has 48 slots
Where : E = generated or induced emf per parallel path + = if the winding is progressive containing 48 coils, each of 10 turns. The flux per pole in the field
E  K N  ( if P , Z and a is considered constants ) - = if the winding is retrogressive structure for this armature, is 500,000 lines. Calculate the speed for
this machine in order that its generated emf be 220 V.
P = Number of Poles a) 2,750 rpm* b) 2,550 rpm c) 2,250 rpm d) 2,000 rpm
Nb = P ( lap winding ) hint: z = 48 (10) (2) = 960 conductors multiply by two kay a = mP =
 = Flux per pole in Weber 8 so in every pole 2 parallel paths or two conductors per element
–8
( 1 Maxwell = 1 x 10 Wb ) Nb = Number of brushes 5. When a generator is being driven at 1,200 rpm, the generated emf
P = No. of poles is 125 volts. What will be the generated emf if the field flux is
Z = Total number of conductors
decreased by 12% with the speed increased to 1,800 rpm?
= Number of slots x no. of conductors per slot b) wave winding – ( for high voltage, low current generator ). a) 135 V b) 145 V c) 155 V d) 165 V*
The finish of the coil is connected to the hint: φ2 = ( 1 – 0.2 ) φ1
N = Rotational or armature speed in rpm start of another coil away from the first coil.
FRANCISCAN ENGINEERING REVIEW PROGRAM ELECTRICAL
ELECTRICAL ENGINEERING
ENGINEERING - DC (MACHINES
- DC MACHINES GENERATOR / MOTOR) SEPTEMBER
SUMMER 2019 2020

a = Number of parallel paths in the armature

GENERATOR a = m P ( if simplex lap winding ) Z  2m y  yf
- A machine that converts the inter – action of mechanical energy a = 2 m ( if simplex wave winding ) y y b
and magnetic energy into electrical energy. P 2
- A dynmo is an example of simple generator . m = multiplicity
m = 1 ( if simplex ) , m = 2 ( if duplex )
y = Average pitch
Mech’l Elect’l
Magnetism PARTS OF A DC MACHINE ( GENERATOR ) Z = no. of winding elements on the surface
Input Output of armature core
1. Stationary part - Produces magnetic flux
Generator Nb = 2 ( wave winding )
2. Rotating part
FARADAY’S LAW OF ELECTROMAGNETIC INDUCTION - Armature responsible of converting mechanical energy into
electrical energy
“ Whenever a conductor cuts magnetic flux, dynamically it induces Sample Problems
an emf “ according to the formula TYPES OF ARMATURE WINDINGS
- Armature windings usually uses closed coil type than the open 1. A 4 pole, lap – wound dc armature, the back pitch is 17, if the
coil type. There are two types of closed coil type namely : winding is progressive what is the front pitch ?
a) 32 b) 15 *
1. Ring winding c) 17 d) 13
PNZ
E  =kN 2. Drum winding 2. A 4 pole dc generator with duplex lap winding has 48 slots and
60 a a) lap winding – ( for low voltage, high current generator ). The four element per slot. The flux per pole is 2.5 x 106 maxwells and
finish of each coil is connected to the start of it runs at 1,500 rpm. What is the output voltage ?
the next coil so the winding pitch or a) 60 volts * b) 360 volts
Comparison of emf formula: commutator pitch is unity or one. c) 225 volts d) 120 volts
3. A 4-pole wave wound dc generator has 50 slots and 24 conductors
yb  y f  2m
E2 N  per slot. The flux per pole is 10 mWb. Determine the induced emf in
= 2 2
E1 N1 1 the armature, it it is rotating at a speed of 600 rpm.
a) 240 V* b) 230 V c) 220 V d) 210 V
yb = back pitch ( should be an odd. no. )
yf = front pitch ( should be an odd. no. ) 4. A 4-pole, simplex lap wound, direct current armature has 48 slots
Where : E = generated or induced emf per parallel path + = if the winding is progressive containing 48 coils, each of 10 turns. The flux per pole in the field
E  K N  ( if P , Z and a is considered constants ) - = if the winding is retrogressive structure for this armature, is 500,000 lines. Calculate the speed for
this machine in order that its generated emf be 220 V.
P = Number of Poles a) 2,750 rpm* b) 2,550 rpm c) 2,250 rpm d) 2,000 rpm
Nb = P ( lap winding ) hint: z = 48 (10) (2) = 960 conductors multiply by two kay a = mP =
 = Flux per pole in Weber 8 so in every pole 2 parallel paths or two conductors per element
–8
( 1 Maxwell = 1 x 10 Wb ) Nb = Number of brushes 5. When a generator is being driven at 1,200 rpm, the generated emf
P = No. of poles is 125 volts. What will be the generated emf if the field flux is
Z = Total number of conductors
decreased by 12% with the speed increased to 1,800 rpm?
= Number of slots x no. of conductors per slot b) wave winding – ( for high voltage, low current generator ). a) 135 V b) 145 V c) 155 V d) 165 V*
The finish of the coil is connected to the hint: φ2 = ( 1 – 0.2 ) φ1
N = Rotational or armature speed in rpm start of another coil away from the first coil.