71. An ac servomotor exhibits
    

1. 1. two time constants which depend upon rotor inertia and mechanical friction

   
   
   

   2. two time constants which depend upon rotor inertia, the slope of its torque speed characteristic and mechanical friction.

   
   
   

   3. a dominant time constant which depends upon rotor inertia and mechanical friction

   
   
   

   4. a dominant time constant which depends upon rotor inertia, the slope of its torque-speed characteristic and mechanical friction.

   
   
   

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1. View Hint View Answer Discuss in Forum

   NA

   Correct Option: D

   NA

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72. If an a.c. servomotor has one of its winding excited by a.c., t hen voltage measured at the other winding with rotor running will be
    

1. 1. zero

   
   
   

   2. proportional to rotor speed

   
   
   

   3. proportional to the square of the rotor speed

   
   
   

   4. constant independent of speed.

   
   
   

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   NA

   Correct Option: B

   NA

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73. A two-phase servomotor develops maximum torque at
    

1. 1. forward speed of one-half of the synchronous speed

   
   
   

   2. backward speed of one-half of the synchronous speed

   
   
   

   3. synchronous speed

   
   
   

   4. a speed of twice the synchronous speed
      

   
   
   

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1. View Hint View Answer Discuss in Forum

   NA

   Correct Option: A

   NA

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74. Driving power from the prime mover driving the alternator is lost but the alternator remains connected to the supply network and the field supply also remains on. The alternator will
    

1. 1. get burnt

   
   
   

   2. behave as an induction motor but will rotate in the opposite direction

   
   
   

   3. behave as a synchronous motor and will rotate in the same direction

   
   
   

   4. behave as a synchronous motor but will rotate in a reverse direction to that corresponding to generator action.

   
   
   

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1. View Hint View Answer Discuss in Forum

   NA

   Correct Option: C

   NA

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75. In a phase of synchronous converter the position of minimum copper loss
    

1. 1. is the tapping point whatever may be the power factor.

   
   
   

   2. varies with the power factor and this position is displaced from the taping point by the power factor angle.

   
   
   

   3. is middle of the phase whatever may be the power factor.

   
   
   

   4. varies with the power factor and this position is displaced from the middle of the phase by the power factor angle.

   
   
   

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1. View Hint View Answer Discuss in Forum

   NA

   Correct Option: D

   NA

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