BCIT ELECTRICAL - AC MACHINES YEAR 3 -
REVIEW TEST QUESTIONS AND ANSWERS
Question 1
How would you reverse the direction of rotation of a capacitor-start induction-run
motor?
Correct Answer
A. Reverse the connections of either the start winding (including capacitor circuit) or
the run winding, but not both.
Question 2
Why are synchronous motors not considered self-starting?
Correct Answer
A. The rotor field cannot immediately develop continuous unidirectional torque
from the rotating stator field when stationary.
Question 3
What constitutes the "power losses" for induction motors?
Correct Answer
A. Stator losses, rotor losses, and mechanical losses
Question 4
What is meant by "cogging" in a heavily loaded synchronous motor?
Correct Answer
A. A condition where the rotor slips poles and momentarily loses synchronism.
Page 1 of 27
,Question 5
For a fixed field current, what determines the angular displacement between the
stator rotating field and the rotor poles in a synchronous motor?
Correct Answer
C. The mechanical load carried by the motor shaft.
Question 6
Which motor has the best speed regulation?
Correct Answer
D. Synchronous motor
Question 7
What are the three fundamental factors that govern the magnitude of induced
voltage in an alternator?
Correct Answer
B. Flux per pole, armature turns, rotor speed
Question 8
How are synchronous motors most commonly started?
Correct Answer
B. By using damper windings so the motor starts as an induction motor and then
pulls into synchronism when field excitation is applied.
Question 9
What is meant by the term "synchronous speed
Correct Answer
C. Speed at which the rotating magnetic field revolves around the stator
Page 2 of 27
, Question 10
How may cogging be overcome in a synchronous motor?
Correct Answer
A. Reduce the mechanical load, increase the field excitation, or restart the motor if
synchronism cannot be restored.
Question 11
What is starting torque?
Correct Answer
B. Torque produced at standstill when the motor is first energized
Question 12
Which of the following is a type of repulsion single-phase motor?
Correct Answer
C. Repulsion induction motor
Question 13
Why will a synchronous motor not operate properly if the field circuit is energized
before the rotor speed approaches near synchronous value?
Correct Answer
A. The rotor poles alternately lock and repel the stator field, causing vibration and
possible damage.
Question 14
What factors determine the rotor speed of a synchronous motor?
Correct Answer
B. Supply frequency and the number of poles determine the synchronous speed of
the motor.
Page 3 of 27
REVIEW TEST QUESTIONS AND ANSWERS
Question 1
How would you reverse the direction of rotation of a capacitor-start induction-run
motor?
Correct Answer
A. Reverse the connections of either the start winding (including capacitor circuit) or
the run winding, but not both.
Question 2
Why are synchronous motors not considered self-starting?
Correct Answer
A. The rotor field cannot immediately develop continuous unidirectional torque
from the rotating stator field when stationary.
Question 3
What constitutes the "power losses" for induction motors?
Correct Answer
A. Stator losses, rotor losses, and mechanical losses
Question 4
What is meant by "cogging" in a heavily loaded synchronous motor?
Correct Answer
A. A condition where the rotor slips poles and momentarily loses synchronism.
Page 1 of 27
,Question 5
For a fixed field current, what determines the angular displacement between the
stator rotating field and the rotor poles in a synchronous motor?
Correct Answer
C. The mechanical load carried by the motor shaft.
Question 6
Which motor has the best speed regulation?
Correct Answer
D. Synchronous motor
Question 7
What are the three fundamental factors that govern the magnitude of induced
voltage in an alternator?
Correct Answer
B. Flux per pole, armature turns, rotor speed
Question 8
How are synchronous motors most commonly started?
Correct Answer
B. By using damper windings so the motor starts as an induction motor and then
pulls into synchronism when field excitation is applied.
Question 9
What is meant by the term "synchronous speed
Correct Answer
C. Speed at which the rotating magnetic field revolves around the stator
Page 2 of 27
, Question 10
How may cogging be overcome in a synchronous motor?
Correct Answer
A. Reduce the mechanical load, increase the field excitation, or restart the motor if
synchronism cannot be restored.
Question 11
What is starting torque?
Correct Answer
B. Torque produced at standstill when the motor is first energized
Question 12
Which of the following is a type of repulsion single-phase motor?
Correct Answer
C. Repulsion induction motor
Question 13
Why will a synchronous motor not operate properly if the field circuit is energized
before the rotor speed approaches near synchronous value?
Correct Answer
A. The rotor poles alternately lock and repel the stator field, causing vibration and
possible damage.
Question 14
What factors determine the rotor speed of a synchronous motor?
Correct Answer
B. Supply frequency and the number of poles determine the synchronous speed of
the motor.
Page 3 of 27
