Synchronous Motors(Electrical Engineering ) Questions and Answers
Question 1. Due to which of the following reasons a synchronous motor fails to pull into synchronism after applying D.C. field current?
High field current
Low short circuit ratio
High core losses
Low field current
Explanation:-
Answer: Option D. -> Low field current
Question 2. The angle between the rotating stator flux and rotor poles is called _____ angle.
torque
obtuse
synchronizing
power factor
Explanation:-
Answer: Option A. -> torque
Question 3. A 3-phase synchronous motor is running clockwise. If the direction of its field current is reversed
the motor will stop
the motor continue to run in the same direction
the winding of the motor will burn
the motor will run in the reverse direction
Explanation:-
Answer: Option B. -> the motor continue to run in the same direction
Question 4. When the rotor speed, in a synchronous machine, becomes more than the synchronous speed during hunting, the damper bars develop
inductor motor torque
induction generator torque
synchronous motor torque
d.c. motor toque
Explanation:-
Answer: Option B. -> induction generator torque
Question 5. The working of a synchronous motor is similar to
gear train arrangement
transmission of mechancial power by shaft
distribution transformer
turbine
Explanation:-
Answer: Option B. -> transmission of mechancial power by shaft
Question 6. Which of the following methods is used to start a synchronous motor ?
Damper winding
Star-delta starter
Damper winding in conjunction with star-delta starter
Resistance starter in the armature circuit
Explanation:-
Answer: Option C. -> Damper winding in conjunction with star-delta starter
Question 7. Which of the following losses is not dissipated by the stator core surface in a synchronous motor ?
Eddy current losses in the conductors
Iron losses in the stator
Copper losses in the slot portion of the conductors
Windage losses
Explanation:-
Answer: Option D. -> Windage losses
Question 8. Which of the following resistances can be measured by conducting insulation resistance test on a synchronous motor ?
Phase to phase winding resistance
Stator winding to earthed frame
Rotor winding to earthed shaft
All of the above
Explanation:-
Answer: Option D. -> All of the above
Question 9. A synchronous motor working at leading power factor can be used as
voltage booster
phase advancer
noise generator
mechanical synchronizer
Explanation:-
Answer: Option B. -> phase advancer
Question 10. The mechanical displacement of the rotor with respect to the stator, in polyphase multipolar synchronous motors running at full load, is of the order of
