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TU#1 Magnetism

The document contains a series of tutorial questions related to electric machines, focusing on calculations involving inductance, magnetic circuits, and magnetic flux. Each question provides specific parameters and asks for various electrical and magnetic properties, such as emf induced, amp-turns, and magnetic field strength. The answers to the questions are also provided in brackets for reference.

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anil.panjiyar
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51 views2 pages

TU#1 Magnetism

The document contains a series of tutorial questions related to electric machines, focusing on calculations involving inductance, magnetic circuits, and magnetic flux. Each question provides specific parameters and asks for various electrical and magnetic properties, such as emf induced, amp-turns, and magnetic field strength. The answers to the questions are also provided in brackets for reference.

Uploaded by

anil.panjiyar
Copyright
© © All Rights Reserved
We take content rights seriously. If you suspect this is your content, claim it here.
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Download as PDF, TXT or read online on Scribd
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Tutorial #1

(Electric Machine)

QN1 A 30 cm long circular iron rod is bent into circular ring and 600 turns of windings are
wound on it. The diameter of the rod is 20mm and relative permeability of the iron is 4000.
A time varying current i = 5 sin 314.16t is passed through the winding. Calculate the
inductance of the coil and average value of emf induced in the coil.
[1.89H, 1890V]

QN.2 For the Magnetic circuit shown below, calculate the Amp-turn (NI) required to establish a
flux of 0.75 wb in the central limb. Given that r = 4000 for iron core.
[40.4  103 Amp-turn]

44 cm

20 cm
I
N

4 cm

4 cm

4cm 15cm 6cm 15cm 4cm

QN.3 Calculate the net magnetic flux in the core of the following magnetic circuit and show the
direction of magnetic flux in the core. Given that cross sectional area of the core is 25 sq.cm
and r = 4000. [23.56 mwb, clockwise ]

30 cm

5 cm
I2 = 15A
I1 = 10A

20 cm
N1 = 200 N2 = 300

N3 = 100

I3 = 10A

QN4 A circular iron core has a cross sectional area of 5 sq. cm and mean length of 15 cm. It has
two coils A and B with 100 turns and 500 turns respectively. The current in the coil A is
changed from zero to 10amp in 0.1 sec. Calculate the emf induced in the coil B. Given that
the relative permeability of the core is 3000.
[62.5 V]

1
QN5 An iron ring of mean length of 1.2m and cross-sectional area of 0.005 m2 is wound
with a coil of 900 turns. If a current of 2 amp in the coil produces a flux density of 2T
in the iron ring, calculate:
i) The mmf
ii) Total flux in the core
iii) Magnetic field strength
iv) Relative permeability of the core. [ 1800AT, 6mwb, 15 AT/m, 637 ]

QN6. An iron ring has a mean length of 1.5m and cross-sectional area of 0.01 m2. It has a
radial air gap of 4mm. The ring is wound with 250 turns. What dc current would be
needed in the coil to produce a flux of 0.8 weber in the air gap? Assume that µr = 400
and leakage factor is 1.25. [2.46 Amp]

QN7 An uneven ring shaped core (as shown below) has µr = 100 and flux density in the
larger section is 0.75T. If the current through the coil is 500mA determine the number
of turns in the coil. [5669]

QN8 A magnetic circuit shown below has cast iron core whose dimensions are given
below:

Length (ab + cd) = 50 cm Cross sectional area of path (ab + cd) = 25 sq.cm
Length (ad) = 20 cm Cross sectional area of path (ad) = 12.5 sq.cm
Length (dea) = 50 cm Cross sectional area of path (dea) = 25 sq.cm

Determine the current ‘I’ required to produce a magnetic flux of 0.75 mWb in the central
limb.
Given that: Number turns in the coil = 500 and µr = 2000. [ 0.22 A ]

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