1. Which of the following motors always starts on load ?

(a) Conveyor motor
(b) Floor mill motor
(c) Fan motor
(d) All of the above

2. ……….. is preferred for automatic drives.

(a) Squirrel cage induction motor
(b) Synchronous motors
(c) Ward-Leonard controlled D.C. motors
(d) Any of the above

3. When the load is above …………. a synchronous motor is found to be more economical.

(a) 2 kW
(b) 20 kW
(c) 50 kW
(d) 100 kW

4. While selecting an electric motor for a floor mill, which electrical characteristics will be of least significance?

(a) Running characteristics
(b) Starting characteristics
(c) Efficiency
(d) Braking

5. Which of the following motors are preferred for overhead travelling cranes?

(a) Slow speed motors
(b) Continuous duty motors
(c) Short time rated motors
(d) None of the above

6. Which of the following motors is used for elevators ?

(a) Induction motor
(b) Synchronous motor
(c) Capacitor start single phase motor
(d) Any of the above

7. Which part of a motor needs maximum attention for maintenance?

(a) Frame
(b) Bearing
(c) Stator winding
(d) Rotor winding

8. …………need frequent starting and stopping of electric motors.

(a) Paper mills
(b) Grinding mills
(c) Air-conditioners
(d) Lifts and hoists

9. Which feature, while selecting a motor for centrifugal pump, will be of least significance?

(a) Starting characteristic
(b) Operating speed
(c) Horse power
(d) Speed control

10. The starting torque in case of centrifugal pumps is generally

(a) less than running torque
(b) same as running torque
(c) slightly more than running torque
(d) double the running torque

Electrical Drives Questions and Answers

11. Which of the following motors are best for the rolling mills ?

(a) Single phase motors
(b) Squirrel cage induction motors
(c) Slip ring induction motors
(d) D.C. motors

12. The starting torque of a D.C. motor is independent of which of the following?

(a) Flux
(b) Armature current
(c) Flux and armature current
(d) Speed

13. Rotor of a motor is usually supported on …………bearings.

(a) ball or roller
(b) needle
(c) bush
(d) thrust

14. A reluctance motor ………….

(a) is provided with slip rings
(b) requires starting gear
(c) has high cost
(d) is compact

15. The size of an excavator is usually expressed in terms of

(a) ‘crowd’ motion
(b) angle of swing
(c) cubic metres
(d) travel in metres

16. For blowers which of the following motor is preferred ?

(a) D.C. series motor
(b) D.C. shunt motor
(c) Squirrel cage induction motor
(d) Wound rotor induction motor

17. Belted slip ring induction motor is almost invariably used for

(a) water pumps
(b) jaw crushers
(c) centrifugal blowers
(d) none of the above

18. Reluctance motor is a…………

(a) variable torque motor
(b) low torque variable speed motor
(c) self starting type synchronous motor
(d) low noise, slow speed motor

19. In jaw crushers motor has to often start against………… load.

(a) heavy
(b) medium
(c) normal
(d) low

20. For a motor-generator set which of the following motors will be preferred ?

(a) Synchronous motor
(b) Slip ring induction motor,
(c) Pole changing induction motor
(d) Squirrel cage induction motor

21. Which of the following motor is usually preferred for kiln drives?

(a) Cascade controlled A.C. motor
(b) Slip-ring induction motor
(c) Three phase shunt wound commutator motor
(d) Any of the above

22. Heat control switches are used in

(a) transformers
(b) cooling ranges
(c) three phase induction motors
(d) single phase

23. In which of the following applications the load on motor changes in cyclic order ?

(a) Electric shovels
(b) Cranes
(c) Rolling mills
(d) All of the above

24. Which of the following machines has heavy fluctuation of load ?

(a) Printing machine
(b) Punching machine
(c) Planer
(d) Lathe

25. In…………. the speed can be varied by changing the position of brushes.

(a) slip ring motor
(b) schrage motor
(c) induction motor
(d) repulsion motor

26. In which of the following applications variable speed operation is preferred ?

(a) Exhaust fan
(b) Ceiling fan
(c) Refrigerator
(d) Water pump

27. Heavy duty cranes are used in

(a) ore handling plants
(b) steel plants
(c) heavy engineering workshop
(d) all of the above

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