Synchronous Motors objective type Questions - Set 01 - ObjectiveBooks

Synchronous Motors objective type Questions - Set 01

Practice Test: Question Set - 01

1. As the load is applied to a synchronous motor, the motor takes more armature current because
    (A) The increased load has to take more current
    (B) The rotor by shifting its phase backward causes motor to take more current
    (C) The back e.m.f. decreases causing an increase in motor current
    (D) The rotor strengthens the rotating field causing more motor current

2. A synchronous motor can be made self starting by providing
    (A) Damper winding on rotor poles
    (B) Damper winding on stator
    (C) Damper winding on stator as well as rotor poles
    (D) None of the above

3. Riunting in a synchronous motor takes place
    (A) When supply voltage fluctuates
    (B) When load varies
    (C) When power factor is unity
    (D) Motor is under loaded

4. Synchronous motors are
    (A) Not-self starting
    (B) Self-starting
    (C) Essentially self-starting
    (D) None of the above

5. An over excited synchronous motor is used for
    (A) Fluctuating loads
    (B) Variable speed loads
    (C) Low torque loads
    (D) Power factor corrections

6. In a synchronous motor running with fixed excitation, when the load is increased three times, its torque angle becomes approximately
    (A) One-third
    (B) Twice
    (C) Thrice
    (D) Six times

7. Change of D.C. excitation of a synchronous motor changes
    (A) Applied voltage of the motor
    (B) Motor speed
    (C) Power factor of power drawn by the motor
    (D) Any of the above

8. Armature of a synchronous machine is
    (A) Of reducing number of slip rings on the rotor
    (B) Armature is associated with large power as compared to the field circuits
    (C) Of difficulty of providing high voltage insulation on rotor
    (D) All of the above reasons

9. A synchronous motor is running with normal excitation. When the load is increased, the armature current drawn by it increases because
    (A) Speed of the motor is reduced
    (B) Power factor is decreased
    (C) Eb (back e.m.f.) becomes less than V (applied voltage)
    (D) Er (net resultant voltage) in armature is increased

10. 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

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