This document contains 5 problems related to calculating magnetic properties such as flux and magnetizing current in magnetic circuits. Problem 1 asks to calculate the current required to produce a flux of 0.8mWb in an iron ring with given dimensions. Problem 2 calculates the total reluctance of a steel ring with an air gap wound with 500 turns of wire. Problem 3 calculates various reluctances and flux in a magnetic frame with two limbs and air gaps. Problem 4 calculates the current required to produce a flux of 1mWb in a magnetic circuit with a central limb and side limbs. Problem 5 calculates the current required to produce a flux of 1.8mWb in a symmetrical cast steel frame with an air gap and given magnetization

1. ELE101 / 102 Dept of E & E Engg, MIT Manipal 1
Tutorial
[1] A circular iron ring has a mean circumference of 1.5m and a cross
sectional area of 0.01m2
. A saw cut of 4mm wide is made in the
ring Calculate the magnetizing current required to produce a flux of
0.8mWb in the air gap if a ring is wound with a coil of 175 turns.
Assume μr = 400, λ = 1.25
What is the current required if the leakage flux is neglected?
Ans: 3.156 A, 2.816 A

2. ELE 101 / 102 Dept of E & E Engg, MIT Manipal 2
[2] A steel ring 10 cm mean radius and of circular cross-section 1 cm in
radius has an air gap of 1 mm length. It is wound uniformly with 500
turns of wire carrying current of 3 A. The air gap takes 60 % of the
total MMF. Neglecting magnetic leakage find the total reluctance
4.22178 × 106
AT / Wb
Tutorial

3. ELE 101 / 102 Dept of E & E Engg, MIT Manipal 3
[3] The magnetic frame shown in figure is built up of iron of square cross section of
3 cm side and each air gap is 2 mm wide. Each of the coil has 1000 turns and
the exciting current is 1 A. The µr of part A and part B may be taken as 1000
and 1200 respectively. Calculate (i) Reluctance of part A (ii) Reluctance of part
B (iii) Reluctance of air gaps (iv) Total Reluctance of complete magnetic circuit
(v) MMF produced and (vi) Flux set up in the circuit
PART A
PART B
3 cm
10 cm
2 mm
3 cm
20 cm
Tutorial
0.17684 × 106
AT / Wb, 0.2505 × 106
AT / Wb,
3.537 × 106
AT / Wb, 3.9643 × 106
AT / Wb, 2000 AT, 0.5045 mWb

4. ELE 101 / 102 Dept of E&E MIT Manipal 1
Tutorial
[4] A magnetic circuit made of silicon steel is as shown. The central limb
has a cross sectional area of 800 mm2
and a coil of 500 turns. Each of
the side limbs has an area of 500 mm2
. Calculate the magnetizing
current required to produce a flux of 1 mWb in the 1 mm air gap if
μr=1000, length BE = 150 mm; length BAGIDE = length BCHJFE =
250 mm. Assume a leakage factor of 1.2
1mm
5mm
A B C
D E F
G
H
I
J
ANS: 4.58 A

5. ELE 101 / 102 Dept of E & E Engg, MIT Manipal 5
Tutorial
Φ
1
Φ2 Φ3
A
B
C
DE
F
[5] A 710 turns coil is wound on the central limb of the cast steel symmetrical
frame of uniform cross section 16 cm2
is as shown. Calculate the current
required to produce a flux of 1.8 mWb in an air gap of 0.2 cm length.
Given lAFEB = lACDB = 25 cm, lAB = 12.5 cm. The magnetization details is as
follows
H 300 500 600 700 900 1092
B 0.1 0.45 0.562 0.775 1 1.125
Ans: I = 2.92 A

6. ELE 101 / 102 Dept of E & E Engg, MIT Manipal 5
Tutorial
Φ
1
Φ2 Φ3
A
B
C
DE
F
[5] A 710 turns coil is wound on the central limb of the cast steel symmetrical
frame of uniform cross section 16 cm2
is as shown. Calculate the current
required to produce a flux of 1.8 mWb in an air gap of 0.2 cm length.
Given lAFEB = lACDB = 25 cm, lAB = 12.5 cm. The magnetization details is as
follows
H 300 500 600 700 900 1092
B 0.1 0.45 0.562 0.775 1 1.125
Ans: I = 2.92 A