Page 78 - Basic Electrical Engineering

Dot convention is used to determine the sign of induced voltage .

If we use dot convention, it will not be required to know the way the coils

have been actually wound.

Example 1.11 The total inductance of two coils connected in series
cumulatatively is 1.6 H and connected differentially is 0.0.4 H. The self

inductance of one coil is 0.6 H. Calculate (a) the mutual inductance and (b)
the coupling coefficient.

Solution:

We know,

L = L + L ± 2M
2
T
1
Substituting the given values

L + L + 2M = 1.6 (i)
1
2
and

L + L − 2M = 0.4 (ii)
1
2

From (i) and (ii)

4M = 1.2

or, M = 0.3 H
given, L = 0.6
1

Therefore, 0.6 + L + 2 × 0.3 = 1.6
2
or, L = 1.6 − 1.2 = 0.4 H
2
L = 0.6 H, L = 0.4 H, M = 0.3 H
2
1