Synchronous Motor mcq objective questions and answers part2

Q1. The speed regulation of a synchronous motor is always
(A) 0.01
(B) 0.5
(C) positive
(D) zero

Q2. The rotor copper losses, in a synchronous motor, are met by
(A) DC source
(B) armature input
(C) motor input
(D) supply lines

Q3. In synchronous motor, which one of the following losses will have the highest proportion?
(A) Stator copper losses
(B) Friction and windage losses
(C) Eddy current losses
(D) Iron losses

Q4. The type of motor in which the stator and rotor magnetic field rotate at the same speed?
(A) Universal motor
(B) Synchronous motor
(C) Induction motor
(D) Reluctance motor

Q5. Synchronous motors are
(A) self-starting
(B) not-self starting
(C) essentially self-starting
(D) none of the above

Q6. A synchronous motor has better power factor as compared to that of an equivalent induction motor. This is mainly because
(A) synchronous motor has no slip
(B) stator supply is not required to produce magnetic field
(C) mechanical load on the rotor remains constant
(D) synchronous motor has large air gap

Q7. To limit the operating temperature an electrical machine should have proper
(A) voltage rating
(B) current rating
(C) power factor
(D) All of these

Q8. The armature current of the synchronous motor has higher values for
(A) high excitation only
(B) low excitation only
(C) Both A and B
(D) none of these

Q9. Power factor of a synchronous motor is unity when the armature current is
(A) maximum
(B) minimum
(C) zero
(D) none of these

Q10. The back emf in the stator of a synchronous motor depends on
(A) speed of rotor
(B) rotor excitation
(C) number of poles
(D) flux density

Q11. In a synchronous motor, the torque angle is the angle between
(A) the rotating stator flux and rotor poles
(B) magnetizing current and back emf
(C) the supply voltage and the back emf
(D) none of the above.

Q12. The hunting in a synchronous motor takes place when
(A) friction in bearings is more
(B) air gap is less
(C) load is variable
(D) load is constant.

Q13. Which synchronous motor will be smallest in size ?
(A) 5 HP, 600 rpm
(B) 5 HP, 375 rpm
(C) 10 HP, 600 rpm
(D) 10 HP, 375 rpm.

Q14. If the field of a synchronous motor is under-excited, the power factor will be
(A) unity
(B) lagging
(C) leading
(D) more than unity

Q15. In a synchronous motor which loss does not vary with load ?
(A) Copper losses
(B) Hysteresis losses
(C) Windage losses
(D) None of the above

Q16. A high starting torque synchronous motor has
(A) simplex rotor
(B) phase wound damper
(C) five slip rings
(D) all of the above

Q17. A 3 phase, 400 V, 50 Hz salient pole synchronous motor is running on no load. What would happen if there is break in the excitation winding of the motor
(A) the motor will stop
(B) the winding will get overheated
(C) the motor will run as reluctance motor at the rated rpm
(D) the motor will run as reluctance motor at lower rpm.

Q18. The size of a synchronous motor decreases with the increase in
(A) speed
(B) horse power rating
(C) flux density
(D) all of the above.

Q19. In a three phase synchronous motor, the magnitude of field flux
(A) varies with speed
(B) varies with load
(C) remains constant at all loads
(D) varies with power factor

Q20. The speed of a synchronous motor
(A) reduces as load increases
(B) increases as load increases
(C) adjusts itself to new equilibrium speed whenever load changes
(D) always remains constant