Question

The phasor addition of stator and rotor mmfs in a cylindrical rotor synchronous machine, is possible because __________

(a) mmfs are rotating in opposite direction

(b) mmfs are rotating in same direction at different speeds

(c) mmfs are stationary with respect to each other

(d) one mmf is stationary and the other mmf is rotating

I have been asked this question in a job interview.

The query is from Power Angle Characteristics of Synchronous Machines in division Synchronous Machines of Electrical Machines

Answer 1

Right answer is (c) mmfs are stationary with respect to each other

The explanation is: The phasor addition is possible due to the fact that the two mmfs are stationary with respect to each other.