Question

A 6 pole machine is rotating at a speed of 1200rpm. This speed in mechanical rad/sec and electrical radians per second is respectively?

(a) 40π, 40π/3

(b) 120π, 40π

(c) 20π, 60π

(d) 40π, 120π

I have been asked this question in semester exam.

This interesting question is from Generated EMF in division Principles of Electro mechanical Energy Conversions of Electrical Machines

Answer 1

Correct answer is (d) 40π, 120π

For explanation: N = 1200rpm,P = 6 and f = PN/120 = 60 cycles per sec.

1cycle = 360° electrical degrees = 2π electrical radians

f in electrical radians per sec = 60∗2π electrical radians/sec = 120π elect radians/sec

speed in mechanical radians/sec = 2/P(speed in electrical rad/sec) = 2/P(120π)=40π mechanical rad/sec.