Online MCQs on Synchronous Motors - Set 07 - ObjectiveBooks

# Practice Test: Question Set - 07

1. A synchronous motor will always stop when
(A) Supply voltage fluctuates
(C) Excitation winding gets disconnected
(D) Supply voltage frequency changes

2. To limit the operating temperature an electrical machine should have proper
(A) Voltage rating
(B) Current rating
(C) Power factor
(D) Speed

3. While starting a synchronous motor by induction motor action, field winding is usually
(A) Connected to D.C. supply
(B) Short-circuited by low resistance
(C) Kept open-circuited
(D) None of the above

4. The speed of a synchronous motor
(A) Increases as the load increases
(B) Decreases as the load decreases
(C) Always remains constant
(D) None of the above

5. The magnitude of field flux in a 3 phase synchronous motor
(A) Remains constant at all loads
(B) Varies with speed
(D) Varies with power factor

6. The maximum value of torque that a synchronous motor can develop without losing its synchronism, is known as
(A) Slip torque
(B) Pullout torque
(C) Breaking torque
(D) Synchronizing torque

7. The armature current of the synchronous motor
(A) Has large values for low excitation only
(B) Has large values for high excitation only
(C) Has large values for low and high excitation
(D) Any of the above

8. A synchronous motor can develop synchronous torque
(B) While overexcited
(C) Only at synchronous speed
(D) Below or above synchronous speed

9. In a synchronous motor, the magnitude of stator back e.m.f. depends on
(A) D.C. excitation only
(B) Speed of the motor
(D) Both the speed and rotor flux

10. When the stator windings are connected in such a fashion that the number of poles are made half, the speed of the rotor of a synchronous motor
(A) Remains same as the original value
(B) Decreases to half the original value
(C) Tends to becomes zero
(D) Increases to two times the original value

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