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Natural oil cooling is used for transformers up to a rating of 3000 kVA.

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Answer : Which of the following is used for thermoelectric cooling? A) Peltier effect B) Seebeck effect C) Both A and B D) None of these

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Answer : Power transformers are generally designed to have maximum efficiency around near full-load.

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Answer : Two transformers are connected in parallel. These transformers do not have equal percentage impedance. This is likely to result in loading of the transformers not in proportion to their kVA ratings.

Answer : Short circuit test on transformers is conducted to determine copper losses.

Description : If the percentage impedances of the two transformers working in parallel are different, then?

Answer : If the percentage impedances of the two transformers working in parallel are different, then parallel operation will still be possible, but the power factors at which the two transformers operate will be different from the power factor of the common load.

Description : Losses which occur in rotating electric machines and do not occur in transformers are?

Answer : Friction losses windage losses 

Description : The efficiency of two identical transformers under load conditions can be determined by?

Answer : The efficiency of two identical transformers under load conditions can be determined by back-to-back test.

Description : The efficiencies of transformers compared with that of electric motors of the same power are?

Answer : Transformers have high efficiency than the same ratted motors

Description : Draw and explain the function of cooling tower in TPS.

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Answer : In a transmission line if booster transformers are to be used, preferred location will be At the intermediate point

Description : An additional condition for parallel operation of three-phase transformers over single-phase transformers is that

Answer : An additional condition for parallel operation of three-phase transformers over single-phase transformers is that the transformers should belong to the same vector group

Description : Why circuit breaker connect b)w two transformer  (same rating

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Description : Classify the transformers based on the construction, frequency and power.

Answer : Classification of Transformer Based On: i) Construction: Shell type, Core type, Berry type ii) Change in voltage level: Step-Up, Step-Down, iii) Number of phases: Single phase, Three phase iv) ... Control vi) Cooling: Self-cooled, Air-cooled, Forced-air cooled, Oil-cooled, Forced-oil cooled. 

Description : Which of the following connection of transformers will give highest value of secondary voltage ? (A) Delta primary delta secondary (B) Delta primary star secondary (C) Star primary star secondary (D) Star primary delta secondary

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Answer : Ans:

Description : State any two conditions for parallel operation of 3-phase transformer.

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