Question

What is the value of Yf for a lap winding with a 4-pole, 12-slot armature with two coil sides/slot? (Assume single-turns coils – progressive winding)

(a) 3

(b) 5

(c) 7

(d) 9

I have been asked this question during an online interview.

My question is taken from Lap Winding topic in portion Armature Windings of DC Machines

Answer 1

The correct choice is (b) 5

Explanation: Coil span is defined as a ratio of number of slots in the armature winding which are also equal to the number of commutator segments to the number of poles. Here, Slots in the armature winding= 12, Number of poles= 4.

YCS= 12/4= 3.

Yb = 2YCS +1= 7

Yf =Yb – 2= 7-2= 5.