SSC JE Electrical Engineering 2015 Paper

Question : 106 of 199

Marks: +1, -0

A 10 pole 25 Hz alternator is directly coupled to and is driven by 60 Hz synchronous motor then the number of poles in a synchronous motor are?

Solution:

If alternator is directly coupled to synchronous Motor then speed will same of both alternator and Motor

N = {120\f}/P

, f(alternator) = 25 Hz
P(alternator) = 10

{120×\f_a}/P_a={120×\f_M}/P_M

P(Motor)

={\f_M×P_a}/\f_a={60×10}/25=24

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