### DC Motors Objectives Part 02

21 . Which of the following curves represents speed torque characteristics of a dc series motor A

22 . The type of dc motor control preferred for applications where unusually wide and very sensitive speed control is required will be ward- Leonard control.

23 . Which curve represents the efficiency of dc motor (D)

24 . When two dc motors operate in series torque is four time that produced by motors when in parallel.

25 . If the flux of dc motor approaches zero the motor will tend to run at

infinite speed.

26 . The duty cycle of a motor is

20KW 120SEC

10KW 120SEC STOPPED 280SEC

The continuous rating of motor suitable for above application would be 14.14KW.

28 . If the applied voltage of dc shunt motor is halved with load torque doubled, the armature current will be doubled.

29 . Change in speed of motor, under ward-Leonard control occurs due to change in armature voltage of dc motor.

30 . Speed control by ward-Leonard method is available in one direction only.

30. For which application a dc motor is preferred over a ac motor Variable speed operation.

31 . In a dc shunt motor if the supply voltage is reduced by 10% which of the following will increase Full Load speed.

32 . Which curve represents the characteristics for a series motor? E

33 . Which curve represents the characteristics for a shunt motor? D

34 . Which curve represents the characteristics of a differentially compound motor? C

35 . Which curve represents the characteristics of a cumulatively compound motor? B

36 . The maximum speed ratio obtainable in a ward-Leonard control, the dc motor is 25:1

37 . In ward-Leonard control, the dc motor is separately excited motor.

38 . In ward-Leonard control, the lower limit of speed is imposed by the residual magnetism of the generator .

39 . The starting resistance of a dc motor is usually low

40 . A dc shunt motor is running at light load. What will happen if the field windings get opened motor will pick up high speed.