Practice Test: Question Set - 09
1. Which of the following resistances can be measured by conducting insulation resistance test on a synchronous motor?
- (A) Phase to phase winding resistance
- (B) Stator winding to earthed frame
- (C) Rotor winding to earthed shaft
- (D) All of the above
2. 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
3. Exciters of synchronous machines are
- (A) D.C. shunt machines
- (B) D.C. series machines
- (C) D.C. compound machines
- (D) Any of the above
4. A synchronous motor is running on a load with normal excitation. Now if the load on the motor is increased
- (A) Power factor as well as armature current
will decrease
- (B) Power factor as well as armature current
will increase
- (C) Power factor will increase but armature
current will decrease
- (D) Power factor will decrease and armature current
will increase
5. The speed regulation of a synchronous motor is always
- (A) 1 %
- (B) 0.5 %
- (C) Positive
- (D) Zero
6. The efficiency of a properly designed synchronous motor will usually fall in range
- (A) 60 to 70%
- (B) 75 to 80%
- (C) 85 to 95%
- (D) 99 to 99.5%
7. The power factor of a synchronous motor is better than that of induction motor because
- (A) Stator supply is relieved of responsibility of
producing magnetic field
- (B) Mechanical load on the motor can be adjusted
- (C) Synchronous motor runs at synchronous speed
- (D) Synchronous motor has large air gap
8. In a synchronous motor, damper windings are provided on
- (A) Stator frame
- (B) Rotor shaft
- (C) Pole faces
- (D) None of the above
9. In a synchronous motor it the back e.m.f. generated in the armature at no-load is approximately equal to the applied voltage, then
- (A) The motor is said to be fully loaded
- (B) The torque generated is maximum
- (C) The excitation is said to be zero percent
- (D) The excitation is said to be hundred percent
10. The construction of a synchronous motor resembles
- (A) A series motor
- (B) An induction motor
- (C) An alternator
- (D) A rotary converter
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