1. The purpose of a breather in a transformer is to ?

provide cooling to the winding

take insulting oil from the conservator

Provide insulation to the winding

extract moisture from the air

Answer: extract moisture from the air

Explanation:


2. In a transformer on no-load, the input voltage ?

is always at 60º to the magnetizing current

is in phase with magnetizing current

leads the magnetizing current by 90°

lags the magnetizing current by 90º

Answer: leads the magnetizing current by 90°

Explanation:


3. Current transformers for meters and relays usually have ?

1 : 2 ratio

5 : 1 ratio

5-A secondaries

15-A secondaries

Answer: 5-A secondaries

Explanation:


4. ln which of the following the highest rating transformer is likely to find application ?

Transmission

Substation

Generator

Distribution

Answer: Generator

Explanation:


5. ln a transformer minimum voltage regulation occurs when the power factor of the load is ?

leading

lagging

0.8

unity

Answer: leading

Explanation:


6. Cross-over windings are used for ?

high voltage winding of large rating transformers

high voltage winding of small rating transformers

low voltage winding of small rating transformers

none of these

Answer: high voltage winding of small rating transformers

Explanation:


7. Simple porcelain bushings are used for transformers upto ?

11 kV

132 kV

400 kV

none of the above

Answer: 11 kV

Explanation:


8. A transformer is working at its full load and its efficiency is also maximum. Its iron loss is 1 kW, its copper loss at half load will be ?

0.1 kW

0.2 kW

0.25 kW

0.5 kW

Answer: 0.25 kW

Explanation:


9. A transformer having a turn ratio 1: 5 and a resistance of 1000 ? is connected across the secondary terminals, the resistance offered to a current flowing in the primary will be ?

10 ?

20 ?

40 ?

60 ?

Answer: 40 ?

Explanation:


10. For minimum weight of a transformer, the weight of iron should be ?

equal to the weight of copper

less than weight of copper

greater than weight of copper

zero

Answer: equal to the weight of copper

Explanation: