Related Questions

The synchronous motor is not inherently self-starting because
A the force required to accelerate the rotor to the synchronous speed in an instant is absent
B the starting device to accelerate the rotor to near synchronous speed is absent
C a rotating magnetic field does not have enough poles
D the rotating magnetic field is produced by only 50 Hz frequency currents
Which of the following motors is non-self starting ?
A D.C. series motor
B synchronous motor
C Squirrel cage induction motor
D Wound round induction motor
Synchronous motors are generally not self-starting because
A the direction of rotation is not fixed
B the direction of instantaneous torque reverses after half cycle
C startes cannot be used on these machines
D starting winding is not provided on the machines
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
In self cooled motors the cooling time constant is about ______ than the heating time constant because cooling conditions are worse at standstill.
A 2 to 3 times greater
B 3 to 4 times greater
C 4 to 5 times greater
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
Which of the following motors has highest starting torque ?
A Repulsion motor
B Shaped pole motor
C Capacitor-start motor
D Split-phase motor
A pony motor is used for the starting which of the following motors?
A Squirrel cage induction motor
B Schrage motor
C Synchronous motor
D None of the above
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
A direct on line starter is used: for starting motors
A Up to 5 H.P.
B Up to 10 H.P.
C Up to 15 H.P.
D Up to 20 H.P.

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