Question

The effect of poly phase currents in poly phase winding can be compared to _______________

(a) Mechanical rotation of permanent magnets at synchronous speed

(b) Mechanical rotation of DC excited field poles at synchronous speed

(c) Mechanical rotation of either permanent magnets or DC excited field poles, at synchronous speed

(d) None of the mentioned

This question was posed to me in examination.

My question is taken from Rotating Magnetic Field in portion Basic Concepts in Rotating Machines of Electrical Machines

Answer 1

Right option is (c) Mechanical rotation of either permanent magnets or DC excited field poles, at synchronous speed

Easiest explanation: The speed at which rotating magnetic field revolves is called the synchronous speed and this effect is equivalent to mechanical rotation of permanent magnets or DC excited field poles.