Related Questions

For three-phase induction motors which of the following is the least efficient method of speed control?
A Cascade control
B Pole changing
C Rheostat control
D Combination of cascade and pole changing
In three-phase squirrel-cage induction motors
A Rotor conductor ends are short-circuited through slip rings
B Rotor conductors are short-circuited through end rings
C Rotor conductors are kept open
D Rotor conductors are connected to insulation
In three-phase induction motors sometimes copper bars are placed deep in the rotor to
A Improve starting torque
B Reduce copper losses
C Improve efficiency
D Improve power factor
DOL starting of induction motors is usually restricted to
A Low horsepower motors
B Variable speed motors
C High horsepower motors
D High speed motors
In squirrel cage induction motors which of the following methods of starting cannot be used?
A Resistance in rotor circuit
B Resistance in stator circuit
C Autotransformer starting
D Star-delta starting
__________ method of starting a three phase induction motor needs six terminals.
A Star-delta
B Resistance starting
C Autotransformer
D None of the above
Which of the following single-phase induction motors is generally used in time phonographs?
A Resistance start
B Capacitor start capacitor run
C Shaded pole
D Universal
Which one of the following is not necessarily the advantage of D.C. motors over A.C. motors?
A Low cost
B Wide speed range
C Stability
D High starting torque
The starting torque of a three phase induction motor can be increased by
A Increasing slip
B Increasing current
C Both (A) and (B)
D None of the above
Which of the following single-phase motors has relatively poor starting torque ?
A Universal motor
B Repulsion motor
C Capacitor motor
D All single phase motors have zero starting torque

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