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
Load Duration
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.
