Transformers

41. Spacers are provided between adjacent coils

to provide free passage to the cooling oil
to insulate the coils from each other
both (A) and (B)
none of the above

Detailed SolutionSpacers are provided between adjacent coils

42. During short circuit test iron losses are negligible because

the current on secondary side is negligible
the voltage on secondary side does not vary
the voltage applied on primary side is low
full-load current is not supplied to the transformer

Detailed SolutionDuring short circuit test iron losses are negligible because

43. Which of the following insulating materials can withstand the highest temperature safely?

Cellulose
Asbestos
Mica
Glass fibre

Detailed SolutionWhich of the following insulating materials can withstand the highest temperature safely?

44. If the supply frequency to the transformer is increased, the iron loss will

not change
decrease
increase
any of the above

Detailed SolutionIf the supply frequency to the transformer is increased, the iron loss will

45. In a power or distribution transformer about 10 per cent end turns are heavily insulated

to withstand the high voltage drop due to line surge produced by the shunting capacitance of the end turns
to absorb the line surge voltage and save the winding of transformer from damage
to reflect the line surge and save the winding of a transformer from damage
none of the above

Detailed SolutionIn a power or distribution transformer about 10 per cent end turns are heavily insulated

46. Iron loss of a transformer can be measured by

low power factor wattmeter
unity power factor wattmeter
frequency meter
any type of wattmeter

Detailed SolutionIron loss of a transformer can be measured by

47. Negative voltage regulation is indicative that the load is

capacitive only
inductive only
inductive or resistive
none of the above

Detailed SolutionNegative voltage regulation is indicative that the load is

48. Losses which occur in rotating electric machines and do not occur in trans formers are

friction and windage losses
magnetic losses
hysteresis and eddy current losses
copper losses

Detailed SolutionLosses which occur in rotating electric machines and do not occur in trans formers are

49. The no load current in a transformer lags behind the applied voltage by an angle of about

180°
120°
90°
75°

Detailed SolutionThe no load current in a transformer lags behind the applied voltage by an angle of about

50. During open circuit test of a transformer

primary is supplied rated voltage
primary is supplied full-load current
primary is supplied current at reduced voltage
primary is supplied rated kVA

Detailed SolutionDuring open circuit test of a transformer

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