Page 511 - Basic Electrical Engineering

Calculate the current, I which must flow through the coil so as to produce a
flux of 1.1 mWb in the central limb.

Solution:

The flux from the central limb will get equally divided in the two outer limbs.
So that flux in the outer limbs will be 0.55 mWbs.

The flux density will be the same throughout as flux density, B is

for central limb

for outer limbs

2
The magnetic field strength, H corresponding to B = 1.1 Wb/m is 650
AT/m.

We have to calculate the AT required to be provided for one of the parallel
paths, i.e., for the central limb, one outer limb, and one air gap.

length of central limb, l = diameter = 20 cm
c

length of the outer limbs, (including air gap)

length of air gap, l = 2 mm = 0.2 cm
g