Industrial Drivers

61. Which of the following motors is preferred for boom hoist of a travelling crane?

1. Single phase motor
2. Synchronous motor
3. A.C. slip ring motor
4. Ward-Leonard controlled D.C. shunt motor

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62. Which of the following motors is preferred when quick speed reversal is the main consideration?

1. Squirrel cage induction motor
2. Wound rotor induction motor
3. Synchronous motor
4. D.C. motor

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

1. Induction motor
2. Synchronous motor
3. Capacitor start single phase motor
4. Any of the above

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64. Which of the following motors is usually preferred for kiln drives?

1. Cascade controlled A.C. motor
2. Slip ring induction motor
3. Three phase shunt wound com-mutator motor
4. Any of the above

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65. Which of the following types of motor enclosure is safest?

1. Totally enclosed
2. Totally enclosed fan cooled
3. Open type
4. Semi closed

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66. Which ofthefollowing motors is preferred when smooth and precise speed control over a wide range is desired?

1. D.C. motor
2. Squirrel cage induction motor
3. Wound rotor induction motor
4. Synchronous motor

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

1. Frame
2. Rearing
3. Stator winding
4. Rotor winding

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

1. Running characteristics
2. Starting characteristics
3. Efficiency
4. Braking

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69. While selecting motor for an air conditioner which of the following characteristics is of great importance?

1. Type of bearings
2. Type of enclosure
3. Noise
4. Arrangement for power transmis¬sion

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