D.C. Motors

Following motor is used where high starting torque and wide speed range control is required?

A. Single phase capacitor start
B. Induction motor
C. Synchronous motor
D. D.C. motor
E. None of the above

Flywheel is used with D.C. compound motor to reduce the peak demand by the motor, compound motor will have to be_____________?

A. level compounded
B. under compounded
C. cumulatively compounded
D. differentially compounded

Speed control by Ward Leonard method gives uniform speed variation_____________?

A. in one direction
B. in both directions
C. below normal speed only
D. above normal speed only

Sparking, is discouraged in a D.C. motor because_____________?

A. it increases the input power con-sumption
B. commutator gets damaged
C. both A. and B.
D. none of the above

Three point starter can be used for______________?

A. series motor only
B. shunt motor only
C. compound motor only
D. both shunt and compound motor

Which D.C. motor is generally preferred for cranes and hoists ?

A. Series motor
B. Shunt motor
C. Cumulatively compounded motor
D. Differentially compounded motor

In D.C. machines the residual magnetism is of the order of_________________?

A. 2 to 3 per cent
B. 10 to 15 per cent
C. 20 to 25 per cent
D. 50 to 75 per cent

For which of the following applications a D.C. motor is preferred over an A.C. motor ?

A. Low speed operation
B. High speed operation
C. Variable speed operation
D. Fixed speed operation

The condition for maximum power in case of D.C. motor is______________?

A. back e.m.f. = 2 x supply voltage
B. back e.m.f. = | x supply voltage
C. supply voltage = | x back e.m.f
D. supply voltage = back e.m.f

A. 4.0
B. 2.0
C. 1.0
D. 0.5