111. A synchronous generator is feeding power to infinite busbars at unity power factor. Its excitation is now increased. It will feed

1. 1. the same power but at a leading power factor.

   
   
   

   2. the same power but at a lagging power factor.

   
   
   

   3. more power at unity power factor.

   
   
   

   4. less power at unity power factor.

   
   
   

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   NA

   Correct Option: B

   NA

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112. If a 400 V, 50 Hz, star connected, 3 phase squirrel cage induction motor is operated from a 400 V, 75 Hz supply, the torque that the motor can now provide while drawing rated current from the supply

1. 1. reduces

   
   
   

   2. increases

   
   
   

   3. remains the same

   
   
   

   4. increases or reduces depending upon the rotor resistance

   
   
   

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   Given induction motor is designed for 400 V, 50 Hz.
   When it is connecetd to 400, 75 Hz supply, then speed for motor increases, as it’s clear from [n = 2ƒ/P] slip of the rotor increased
   

   Torque, Te =	3	. I2²	r2
   	ωs		s

   
   As the slip increases, T_e decreases.

   Correct Option: A

   Given induction motor is designed for 400 V, 50 Hz.
   When it is connecetd to 400, 75 Hz supply, then speed for motor increases, as it’s clear from [n = 2ƒ/P] slip of the rotor increased
   

   Torque, Te =	3	. I2²	r2
   	ωs		s

   
   As the slip increases, T_e decreases.

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113. Armature reaction at of a synchronous generator at rated voltage zero power factor lagging is

1. 1. magnetizing

   
   
   

   2. demagnetizing

   
   
   

   3. cross-magnetizing

   
   
   

   4. both magnetizing and cross-magnetizing

   
   
   

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   NA

   Correct Option: B

   NA

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114. Voltage regulation of a synchronous generator calculated by synchronous impedance method is

1. 1. higher than actual because of saturation of magnetic circuit

   
   
   

   2. lower than actual because of saturation of magnetic circuit

   
   
   

   3. nearly accurate because it takes account of magnetic circuit.

   
   
   

   4. nearly accurate because the generator is normally operated with an unsaturated magnetic circuit.

   
   
   

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   NA

   Correct Option: A

   NA

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115. A synchronous motor is floating on infinite mains at no load. If its excitation is now increased, it will draw

1. 1. unity power factor current

   
   
   

   2. zero power factor lagging current

   
   
   

   3. zero power factor loading current

   
   
   

   4. no current

   
   
   

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1. View Hint View Answer Discuss in Forum

   NA

   Correct Option: C

   NA

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