1. ELE101 / 102 Dept of E & E Engg, MIT Manipal 1
Series Magnetic Circuit
( )
gg332211
rg0
gg
3r0
33
2r0
22
1r0
11
gg332211
lHlHlHlHfTotal mm
μμ
lB
μμ
lB
μμ
lB
μμ
lB
SφSφSφSφmmf
+++=








+++=+++=
grg
g
g
r
r
r
g
aμμ
l
S
aμμ
l
S
aμμ
l
S
aμμ
l
SWhere
SSSSce SlucTotal
0
330
3
3
220
2
2
110
1
1
321tanRe
=
=
=
=
+++=

2. ELE 101 / 102 Dept of E & E Engg, MIT Manipal 2
Exercise
Fig. 1
The iron ring shown in Fig. 1, is made up of a material having a relative
permeability of 1000 and has a flux density of 2 T in the air gap. For the
given dimensions of l1 = 0.15 m, l2 = 0.1 m, l3 = 0.2 m, lag = 1 cm, A1
= A3 = Aag = 2*10-4 m2, A2 = 3*10-4 m2, if the current through the
coil is 1.5 A, compute the number of turns required. Neglect leakage
flux and fringe effect.
11029 turns

3. ELE 101 / 102 Dept of E&E MIT Manipal 1
Parallel magnetic circuit without air gap
+-
R A
R B R
V
Analogous electrical circuit
21 φ+φ=φ=== ;
aμμ
l
S;
aμμ
l
S;
aμμ
l
S
3r30
1
AFEB
2r20
2
ADCB
r0
AB
1
A
B C
D
E
F
Φ
Φ1
N
Φ2
ADCB2AFEB1
ADCB2AFEB1ABTotal
SSWhere
),SorS(SMMF
mmf)B or ADCB(Path AFEmfPath AB mrequiredTotal mmf
φ=φ
φφ+φ=
+=

4. ELE 101 / 102 Dept of E&E MIT Manipal 1
Parallel magnetic circuit with air gap
Φ1 Φ2
A
B
C
DE
F
Φ
+-
R A
R B V
R a
R bAnalogous electrical circuit

5. ELE 101 / 102 Dept of E&E MIT Manipal 1
Exercise
The core shown has a relative permeability of 4000. Find the current
required for the exciting coil to produce a flux of 10 milli Wb in the central
limb. Take total number of turns of the coil as 500 turns.
ANS: 2.387 A

6. ELE 101 / 102 Dept of E&E MIT Manipal 1
Exercise
The core shown has a relative permeability of 4000. Find the current
required for the exciting coil to produce a flux of 10 milli Wb in the central
limb. Take total number of turns of the coil as 500 turns.
ANS: 2.387 A