136. If a squirrel-cage induction motor having a rated slip of 2% on full-load has a starting torque of 0.5 full-load torque, then starting current is

1. 1. equal to full-load current

   
   
   

   2. twice full-load current

   
   
   

   3. four times full-load current

   
   
   

   4. five times full-load current

   
   
   

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   NA

   Correct Option: D

   NA

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137. If an induction motor when started on load does not accelerate up to full speed but runs at 1/7th of the rated speed, then it is called

1. 1. locking

   
   
   

   2. plugging

   
   
   

   3. crawling

   
   
   

   4. clogging

   
   
   

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   NA

   Correct Option: C

   NA

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138. An induction motor is fed from a balanced threephase supply at rated voltage and frequency through a bank of three single phase transformers connected in delta-delta. If one unit of the bank develops fault and is removed, then

1. 1. single phasing will occur and the machine fails to start

   
   
   

   2. single phasing will not occur but the motor terminal voltages will become unbalanced and machine can be loaded to the extent of 57.7% of its rating

   
   
   

   3. machine can be loaded to the extent of 57.7% of its rating with balanced supply at its terminals.

   
   
   

   4. machine can be loaded to the extent of 66.66% with balanced supply at its terminals.

   
   
   

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   NA

   Correct Option: D

   NA

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139. If rotor of an induction motor is assumed to be purely resistive, then angle between resultant flux density wave and rotor mmf wave is

1. 1. dependent upon the load

   
   
   

   2. 180°

   
   
   

   3. 90°

   
   
   

   4. 45°

   
   
   

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   NA

   Correct Option: C

   NA

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140. Unbalanced supply voltage given to a 3-phase, delta-connected induction motor will cause

1. 1. zero sequence currents

   
   
   

   2. less heating of the motor

   
   
   

   3. negative sequence components current

   
   
   

   4. all of these

   
   
   

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   NA

   Correct Option: C

   NA

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