In a 3-phase, 4-pole, 50 Hz synchronous motor, the frequency, pole number and load torque all are halved. The motor speed will be____________?
Correct answer: B. 1500 r.p.m.
- A. 3000 r.p.m.
- B. 1500 r.p.m.
- C. 750 r.p.m.
- D. none of the aboveTry CAD Software
Explanation
Synchronous speed is Ns = 120f/P. Halving both frequency and pole number leaves their ratio unchanged, so the speed remains 1500 r.p.m.; load torque does not set synchronous speed.
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