2. The size of an excavator is usually expressed in terms of
Correct : B. m 3
3. The range of ratings of electric motor used for rolling mills is of the order of
Correct : C. 85 to 400 kW
4. When an electric train is moving down a hill the DC motor operates as a DC
Correct : B. Series generator
5. Speed controlled by variation of field flux results in
Correct : A. Constant power Drive
6. The slip power recovery scheme is used in induction motor for speed control in the range
Correct : C. Both above and below synchronous speed
7. The pair used for frequency converter is
Correct : A. Squirrel cage induction motor and synchronous motor
8. The motor in close are used for collieries, chemical plant is
Correct : A. Flame proof type
9. The motor enclosure used in wood-working industry is
Correct : B. Totally enclosed fan cooled type
10. The motor enclosure used for industrial purposes is
Correct : A. Protected type
11. Ball-bearings are
Correct : D. All of the above
12. Sleeve bearings
Correct : D. All of the above
13. Hot bearings of a DC motor may be caused by
Correct : D. Lack of or dirty lubricant
14. The least expensive drive is
Correct : A. Belt drive
15. For very high speed ratio the indispensable drive is
Correct : B. Rope Drive
16. 15 minute rated motors are suitable for
Correct : A. Light duty cranes
17. For medium duty cranes the short time rating motor used is
Correct : C. 30 minutes
18. The cost of an induction motor will increase as
Correct : A. Horse power rating increases but rpm decreases
19. Which of the following motors has series characteristics?
Correct : B. Repulsion motor
20. Which of the following motors is preferred for boom host of a travelling crane?
Correct : C. AC slip ring motor
21. For crane travel which off the following motors is normally used?
Correct : D. AC slip ring motor
22. Which of the following happens when start Delta starter is used ?
Correct : D. Both A and B
23. The characteristics of drive for crane hoisting and lowering are which off the
following?
Correct : D. All of the above
24. In ........the speed can be varied by changing the position of brushes
Correct : B. Schrage motor
25. In which of the following applications variable speed operation is preferred?
Correct : B. Ceiling fan
26. The travelling speed of cranes varies from from
Correct : D. 1 to 2.5 m/s
27. Which of the following motors is preferred when quick speed reversal is the main
consideration?
Correct : D. DC motor
28. Which off the following motors is preferred when a smooth and resize speed control over a wide range is desired?
Correct : A. DC motor
29. Which of the following machines has heavy fluctuating of load ?
Correct : B. Punching machine
30. Which of the following motors is usually preferred for kiln drives?
Correct : D. Any of the above
31. In squirrel cage induction motors which of the following methods of starting
cannot be used ?
Correct : A. Resistance in rotor circuit
32. Electric drive is becoming more and more popular because
Correct : D. All of the above
33. The basic elements of an electric drive are
Correct : B. Electric motor, the transmission and control system
34. Introduction of automation in production process has become possible only
because of the use of
Correct : C. Individual and multi motor drives
35. DC motor are still preferred for use in
Correct : A. Electric excavators, steel mills and cranes
36. A typical active load is
Correct : A. Hoist
37. In jaw crushers, a motor has to often start against
Correct : D. heavy load.
38. Motor used for elevators is generally
Correct : B. induction motor
39. In synthetic fibre mills motor with
Correct : A. constant speeds are preferred
40. Which of the following motor is preferred for synthetic fibre mills ?
Correct : B. reluctance motor
41. Reluctance motor is a
Correct : A. self-starting type synchronous motors
42. A reluctance motor
Correct : A. is compact
43. Power factor in case of reluctance motor is
Correct : D. 0.3 to 0.4.
44. The efficiency of reluctance motor is around
Correct : D. 60 to 75%.
45. A reluctance motor on over-load runs as
Correct : B. induction motor
46. The size of a excavator is usually expressed in terms of
Correct : A. cubic meters
47. Ward-Leonard controlled dc drives are generally used for
Correct : C. heavy duty excavators
48. In case of contactors, the contacts are generally made of
Correct : D. any of the above.
49. Which electromagnet is preferred for noiseless operation
Correct : A. DC operated
50. For high frequency choppers the device that is preferred is
Correct : C. Transistor
51. The number of operations per hour in case of class IV contactor will be around
Correct : D. 1200.
52. In case of contactors, the duty in which the main contacts remain closed for a period bearing a definition relation to the no-load periods, is known as
Correct : B. Intermittent duty
53. In case of contactors the ratio of the in service period to the entire period, expressed as a percentage is known as
Correct : B. load factor
54. A class I contactor should be mechanically sound to withstand
Correct : B. 0.25 million times
55. Which of the following pair is used for frequency converters ?
Correct : A. Squirrel cage induction motor and synchronous motor
56. Belted wound rotor induction motors are preferred for
Correct : B. gyratory crushers
57. The cooling time constant is usually
Correct : B. more than heating time constant
58. A motor of less than full load power rating can be used if the load is
Correct : B. short time duty
59. Pole changing method of speed control is used in
Correct : D. squirrel cage induction motor.
60. To save the energy during braking
Correct : C. regenerative braking is used
61. To get speed higher than the base speed of the dc shunt motor
Correct : B. field resistance control is used
62. Rotor resistance speed control is used in
Correct : C. slip ring induction motor
63. Effect of friction torque is more pronounced
Correct : B. when the drive is being started
64. The equilibrium speed of a motor load system is obtained
Correct : A. when motor torque equals the load torque
65. Most commonly used ac motor is
Correct : C. Squirrel cage induction motor
66. The motor commonly used in computers and digital systems is
Correct : B. Induction motor
67. Regenerative braking mode can be achieved in which quadrant (V-I curve)?
Correct : B. Second
68. Fan type of loads exhibits which type of load torque characteristics?
Correct : C. Non-Linearly rising torque characteristics
69. Type-A chopper is used for obtaining which type of mode?
Correct : A. Motoring mode
70. Boost converter is used to _________
Correct : B. Step up the voltage
71. Reverse motoring mode is available in fourth quadrant.
Correct : A. True
72. Which one is an example of variable loss?
Correct : C. Armature copper loss
73. Load torques can be classified into how many types?
Correct : B. Two
74. Rolling mills exhibit what type of load torque characteristics?
Correct : D. Non-Linearly decreasing torque characteristics
75. What is the relationship between torque and speed in constant type loads?
Correct : A. Torque is independent of speed
76. Torque inversely varies with the speed in the windage load torque component.
Correct : B. False
77. What type of force handles for active torques?
Correct : C. Gravitational forces
78. Passive torques always oppose the motion of the driven machine.
Correct : A. True
79. Among the following which one exhibits linearly rising load torque characteristics?
Correct : D. Separately excited dc generator connected to the resistive load
80. What is the condition for the steady-state operation of the motor?
Correct : C. Load torque = Motor torque
81. Choose the correct one. (* stands for multiplication, J represents the moment of
inertia, w represents angular spee(D).
Correct : C. J*d(w)/dt = Motor torque – Load torque
82. In DC chopper, the waveform for input and output voltages is respectively __________
Correct : B. Continuous and Discontinuous
83. A chopper behaves as a __________
Correct : B. DC equivalent of AC transformer
84. A DC chopper feeds an RLE load. If the value of E is increased by 20%, the current ripple ________
Correct : D. remains the same
85. The conduction loss versus device current characteristic of a power MOSFET is
best approximated by a ________
Correct : C. Parabola
86. Which of the following device is NOT suitable for parallel operation?
Correct : B. BJT
87. SCR is uni-directional in nature.
Correct : A. True
88. Which of the following device should be used as a switch in a low power switched mode power supply (SMPS)?
Correct : C. MOSFET
89. Servo motors are an example of which type of load?
Correct : B. Short time loads
90. Load torque of the crane is independent of _________
Correct : A. Speed
91. The unit of angular velocity is rad/s .
Correct : B. False
92. R.M.S value of the sinusoidal waveform V=V sin(ωt+α).
Correct : A. V ÷2
93. Calculate the time period of the waveform x(t)=24sin(24πt+π÷4).
Correct : C. .083 sec
94. The turn-o times of the devices in increasing order is ___________
I. MOSFET
II. BJT
III. IGBT
IV. Thyristor
Correct : A. I, III, II, IV
95. Which of the following devices should be used as a switch for high power and high
voltage application?
Correct : D. Thyristor
96. Calculate the useful power developed by a motor using the given data: P = 3000 W,
I = 60 A, R = .4 Ω. Assume frictional losses are 200 W and windage losses are 400 W.
Correct : B. 960 W
97. The consideration involved in the selection of the type of electric drive for a particular application depends on
Correct : D. All of the above.
98. Which of the following is preferred for automatic drives ?
Correct : C. Ward Leonard controlled dc motors
99. Which type of drive can be used for hoisting machinery