ENGG 410
(Fundamentals of Deformable Bodies)
Name: EDRA, CHIN CHIN D. Date: JULY 06 2021
SR Code: 18-06145 Course & Section: EE - 3306
EE 406 – ELECTRICAL MACHINES 2
PROBLEM SET NO. 1 – Part B
Solve the following problems completely. Box your final answer/s.
Rounding off should only be done on your final answers with four
decimal places only.
1. A 2500 kVA, 6600 V synchronous turbo alternator is operating at
full load and 0.8 pf lagging. This machine has a synchronous
reactance per phase is 10.4 ohms and a negligible resistance.
Calculate the percentage voltage regulation?
Ans. %VR = 43.96%
HE gives strength to the weary
And increase the power of the. Engr. Jonas S. De Castro, REE
I Lecturer
saiah 40:29
ENGG 410
(Fundamentals of Deformable Bodies)
HE gives strength to the weary
And increase the power of the. Engr. Jonas S. De Castro, REE
I Lecturer
saiah 40:29
ENGG 410
(Fundamentals of Deformable Bodies)
2. A 50 –kVA, 550 – volt single phase alternator draws a field current
10 A at rated load. With the same field current, the open circuit
emf and short – circuit current are 300 V and 150 A. The ohmic
resistance of the armature between terminals is 0.18 ohm. The ratio
of effective to ohmic resistance maybe taken as 1.5. Determine the
regulation at 0.8 power factor lagging.
Ans. %VR = 25.47%
HE gives strength to the weary
And increase the power of the. Engr. Jonas S. De Castro, REE
I Lecturer
saiah 40:29
ENGG 410
(Fundamentals of Deformable Bodies)
HE gives strength to the weary
And increase the power of the. Engr. Jonas S. De Castro, REE
I Lecturer
saiah 40:29
ENGG 410
(Fundamentals of Deformable Bodies)
3. To get the armature resistance of a 100 MW, 13.8 kV and 90%
power factor generator, two terminals are connected to a DC
source. The measured current and voltage are 87.6 amperes and 6
volts respectively. What is the DC resistance per phase ?
Ans. wye connected = 0.0342 Ω; delta connected = 0.1027 Ω
HE gives strength to the weary
And increase the power of the. Engr. Jonas S. De Castro, REE
I Lecturer
saiah 40:29
ENGG 410
(Fundamentals of Deformable Bodies)
HE gives strength to the weary
And increase the power of the. Engr. Jonas S. De Castro, REE
I Lecturer
saiah 40:29
ENGG 410
(Fundamentals of Deformable Bodies)
4. A 2 MVA, 2.3 – kV three – phase, Y – connected alternator
operates at rated kVA at a power factor of 80%. The dc armature
winding resistance between terminals is 0.08 Ω. The field takes 70
A at 125 V from an exciter equipment. Friction and windage loss is
20 kW, iron losses is 36 kW and stray load losses are 2.0 kW.
Calculate the efficiency of the alternator. Assume the effective
armature – winding resistance is 120% of the DC resistance.
Ans. 93.9494 %
HE gives strength to the weary
And increase the power of the. Engr. Jonas S. De Castro, REE
I Lecturer
saiah 40:29
ENGG 410
(Fundamentals of Deformable Bodies)
HE gives strength to the weary
And increase the power of the. Engr. Jonas S. De Castro, REE
I Lecturer
saiah 40:29
ENGG 410
(Fundamentals of Deformable Bodies)
5. A 2,500 kVA, three – phase, 60 Hz, 6.6 kV wye connected
alternator has a field resistance of 0.45 Ω and an armature
resistance of 0.05 Ω per phase. The field current at full load 0.85
pf, is 200 A. The stray power losses amount to 82 kW. Calculate
the efficiency of the alternator at full load, 0.85 pf lagging.
Ans. 95.1987 %
HE gives strength to the weary
And increase the power of the. Engr. Jonas S. De Castro, REE
I Lecturer
saiah 40:29
ENGG 410
(Fundamentals of Deformable Bodies)
HE gives strength to the weary
And increase the power of the. Engr. Jonas S. De Castro, REE
I Lecturer
saiah 40:29
