Electrical Drives Multiple Choice Questions and Answers for Practice

16. The basic elements of a electric drive are

1. electrical motor and control system
2. electric motor
3. control system
4. None of these

17. The concept of V/f control of inverters driving induction motors resuls in

1. reduced magnetic loss
2. constant torque operation
3. speed reversal
4. hormonic elimination

18. The heating time constant of an electrical machine gives an induction of its

1. overload capacity
2. rating
3. cooling
4. short time rating

19. The power input to a 3 - F induction motor is 60 kW and stator loss is 1 kW the rotor cu loss per phase is

1. slip × 69 / 3
2. slip × 50 / 3
3. slip × 59 / 3
4. 1

20. The slip of an induction motor during DC rheostatic braking is

1. 2 + s
2. 2 - s
3. 1 - s
4. s

21. What are the constituents in speed time curve of train?

1. Constant speed
2. Coasting
3. Initial acceleration
4. All of the above

22. What type electric drive is used in cranes?

1. Individual
2. Multimotor
3. Group
4. Both A and C

23. Which braking is not possible in series motor?

1. Counter current braking
2. Regenerative braking
3. Dynamic braking
4. Rheostat braking

24. Which of the following are electrical braking methods ?

1. regenerative
2. plugging
3. dynamic
4. All of the above

25. Which speed control method preferred for constant torque drive?

1. Mechanical loading system
2. Field control
3. Armature voltage control
4. None of these

26. While operating on variable frequency supplies, the AC motor requires variable voltage in order to

1. improve the capabilities of the inverter
2. protect the insulation
3. avoid effect of saturation
4. protect thyristor from dV / dt