Question

A 3-phase machine has integral slot winding with fundamental distribution factor kd1, the distribution factor for n^th harmonic kdn is ____________

(a) less than kd1

(b) more than kd1

(c) equal to kd1

(d) depends upon the number of slots and poles

The question was posed to me during an interview.

This intriguing question originated from EMF Polygon in section Synchronous Machines of Electrical Machines

Answer 1

Right choice is (a) less than kd1

The explanation is: kdn=(sinqnγ/2)/(qsinnγ/2) and examples will show that kdn is less than kd1. This has the effect of reducing the n^th harmonic EMF in comparision with fundamental EMF. This is certainly an advantage of distributing the winding in slots.