121. If armature current in a generating synchronous machine is in phase with the excitation emf, then armature mmf vector

1. 1. lags behind the field mmf vector by 90°.

   
   
   

   2. is in the same direction as the field mmf vector.

   
   
   

   3. is in a direction opposite to the field mmf vector.

   
   
   

   4. leads the field mmf vector by 90° as observed from the startor

   
   
   

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   NA

   Correct Option: A

   NA

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122. Mmf of a sinusoidally distributed current sheet is

1. 1. triangular shifted from the current by 90°

   
   
   

   2. triangular in phase with the current wave

   
   
   

   3. sinusoidal shifted from the current wave by 90°

   
   
   

   4. sinusoidal in phase with the current wave

   
   
   

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   NA

   Correct Option: C

   NA

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123. In a non-salient pole synchronous machine, distribution of field mmf around the air gap is a

1. 1. sinusoidal wave

   
   
   

   2. rectangular wave

   
   
   

   3. stepped triangular wave

   
   
   

   4. flat topped stepped wave

   
   
   

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   NA

   Correct Option: D

   NA

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124. In a salient pole synchronous machine, the airgap is

1. 1. uniform under the whole pole shoe

   
   
   

   2. least under the middle of the pole shoe and increases outwards

   
   
   

   3. largest under the middle of the pole shoe and decrease outwards

   
   
   

   4. least at one end of the pole shoe and increases to the maximum value at the other end.

   
   
   

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   NA

   Correct Option: B

   NA

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125. Two sinusoidally distributed rotating fields are created by the startor and rotor of a cylindrical magnetic structure. Two fields having same number of poles are rotating in the same direction at the same speed. The interaction of these fields will produce a torque proportional to the sine of the angle between

1. 1. either of the fields and the resultant field and acts in a direction to reduce this angle.

   
   
   

   2. either of the fields and the resultant field and acts in a direction to increase this angle.

   
   
   

   3. the rotor field (but not the startor field) and the resultant field and acts in a direction to reduce this angle.

   
   
   

   4. the rotor field (but not the startor field) and the resultant field and acts in a direction to increase this angle.

   
   
   

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   NA

   Correct Option: A

   NA

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