Related Questions

Which of the following materials is used in the manufacture of resistance grids to be used in the starters of largemotors ?
A Copper
B Aluminium
C Steel
D Cast-iron
The auto-starters (using three auto transformers) can be used to start cage induction motor of the following type
A Star connected only
B Delta connected only
C Both (A) and (B)
D None of the above
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 case of D.C. shunt motors the speed is dependent on back e.m.f. only because
A Back e.m.f. is equal to armature drop
B Armature drop is negligible
C Flux is proportional to armature current
D Flux is practically constant in D.C. shunt motors
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
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
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.
Blocked rotor test on induction motors is used to find out
A Leakage reactance
B Power factor on short circuit
C Short-circuit current under rated voltage
D All of the above
Which of the following motors is used in mixies ?
A Repulsion motor
B Reluctance motor
C Hysteresis motor
D Universal motor
D.C. shunt motors are used for driving
A Trains
B Cranes
C Hoists
D Machine tools

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