Most Synchronous Motors

91. The oscillations in a synchronous motor can be damped out by

1. maintaining constant excitation
2. running the motor on leading power factors
3. providing damper bars in the rotor pole faces
4. oscillations cannot be damped

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92. The percentage slip in case of a synchronous motor is

1. 1%
2. 100%
3. 0.5%
4. zero

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93. The power developed by a synchronous motor will be maximum when the load angle is

1. zero
2. 45°
3. 90°
4. 120°

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94. The power factor of a synchronous motor is better than that of induction motor because

1. stator supply is relieved of responsibility of producing magnetic field
2. mechanical load on the motor can be adjusted
3. synchronous motor runs at synchronous speed
4. synchronous motor has large air gap

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95. The ratio of starting torque to running torque in a synchronous motor is

1. zero
2. one
3. two
4. infinity

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96. The rotor copper losses, in a synchronous motor, are met by

1. d.c. source
2. armature input
3. motor input
4. supply lines

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97. The shaft of synchronous motor is made of

1. mild steel
2. chrome steel
3. alnico
4. stainless steel

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98. The size of a synchronous motor decreases with the increase in

1. flux density
2. horse power rating
3. speed
4. all of the above

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99. The speed of a synchronous motor

1. increases as the load increases
2. decreases as the load decreases
3. always remains constant
4. none of the above

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100. The speed regulation of a synchronous motor is always

1. 1%
2. 0.5%
3. positive
4. zero

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