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Synchronous Motors

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____________?

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____________?

A. 3000 r.p.m.
B. 1500 r.p.m.
C. 750 r.p.m.
D. none of the above

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____________? Read More »

Synchronous Motors

By which of the following methods the constant speed of a synchronous motor can be changed to new fixed value ?

By which of the following methods the constant speed of a synchronous motor can be changed to new fixed value ?

A. By changing the supply frequency
B. By interchanging any two phases
C. By changing the applied voltage
D. By changing the load

By which of the following methods the constant speed of a synchronous motor can be changed to new fixed value ? Read More »

Synchronous Motors

A 3-phase synchronous motor is running clockwise. If the direction of its field current is reversed

A 3-phase synchronous motor is running clockwise. If the direction of its field current is reversed

A. the motor will stop
B. the motor continue to run in the same direction
C. the winding of the motor will burn
D. the motor will run in the reverse direction
E. none of the above

A 3-phase synchronous motor is running clockwise. If the direction of its field current is reversed Read More »

Synchronous Motors

Due to which of the following reasons a synchronous motor fails to pull into synchronism after applying D.C. field current?

Due to which of the following reasons a synchronous motor fails to pull into synchronism after applying D.C. field current?

A. High field current
B. Low short circuit ratio
C. High core losses
D. Low field current

Due to which of the following reasons a synchronous motor fails to pull into synchronism after applying D.C. field current? Read More »

Synchronous Motors