236. A 220/440 V, 50 Hz, 5 kVA single phase transformer operates on 220 V, 40 Hz supply with secondary winding. Then

1. 1. the eddy current loss and hysteresis loss of the transformer decrease

   
   
   

   2. the eddy current loss and hysteresis loss of the transformer increase

   
   
   

   3. the hysteresis loss of the transformer increases while eddy current loss remains the same

   
   
   

   4. the hysteresis loss remains the same whereas eddy current loss decreases

   
   
   

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   NA

   Correct Option: A

   NA

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237. Supply to one terminal of a delta-wye connection three-phase core type transformer which is on no-load, fails. Assuming magnetic circuit symmetry, voltages on the secondary side will be

1. 1. 230, 230, 115

   
   
   

   2. 230, 115, 115

   
   
   

   3. 345, 115, 115

   
   
   

   4. 345, 0, 345

   
   
   

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   NA

   Correct Option: A

   NA

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238. Keeping in view the requirement of parallel operation, which of the 3-phase connections given below are possible?

1. 1. delta-delta to delta-star

   
   
   

   2. delta-delta to star-delta

   
   
   

   3. star-star to delta-delta

   
   
   

   4. delta-star to star-delta

   
   
   

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   NA

   Correct Option: C

   NA

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239. Auto-transformer is used in transmission and distribution

1. 1. when operator is not available

   
   
   

   2. when iron losses are to be reduced

   
   
   

   3. when efficiency considerations can be ignored

   
   
   

   4. when the transformation ratio is small

   
   
   

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   NA

   Correct Option: D

   NA

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240. A voltage v = 400 sin 314.16 t is applied to a 1– phase transformer on no-load. If the no load current of the transformer is 2 sin (314.16 t ∠– 85°),

1. 1. 141 ∠90°

   
   
   

   2. 200 ∠– 85°

   
   
   

   3. 200 ∠85°

   
   
   

   4. 282 ∠– 80°

   
   
   

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   NA

   Correct Option: C

   NA

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