1.

A uniformly distributed winding on the stator has three full pitched coils, each coil having N turns and each turn carrying a current i. The MMF produced by the winding is?(a) sinusoidal in waveform with an amplitude 3Ni(b) sinusoidal in waveform with an amplitude 3Ni/2(c) trapezoidal in waveform with an amplitude of 3Ni(d) trapezoidal in waveform with an amplitude of 3Ni/2This question was addressed to me by my school teacher while I was bunking the class.My question comes from MMF Produced by Distributed Windings topic in portion Synchronous Machines of Electrical Machines

Answer»

The CORRECT choice is (d) trapezoidal in waveform with an AMPLITUDE of 3Ni/2

Best explanation: When the machine has more than 3 slots per POLE per phase, the steps in the MMF wave are neglected and MMF variation is taken as smooth over these slots and as a consequence, stepped MMf wave changes to trapezoidal MMF wave. The trapezoidal MMF wave amplitude = 3Ni/2.



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