Transformer. part - 2

11. Scott connection are used for

A. 1 phase to 3-ф transformation

B. Three phase to 1-ф transformation

C. Three phase to two phase transformation

D. None of the above

12. Buchholz relay is used for

A. Air cooled transformer

B. Instrument transformer

C. Distribution transformer

D. Oil immersed power transformer capacity up to above 500kva

13. The two windings of a transformer are

A. Conductively linked

B. Inductively linked

C. Not linked at all

D. Electrically linked

14. Power transformers are designed to have maximum efficiency around _____full load

A. Nearly                   

B. 70% of

C. 50% of

D. 2% of

15. The burden of current transformers is expressed in

A. Volt-ampere rating (VA)

B. Current rating of secondary winding

C. Current and voltage of secondary

D. Watt rating

16. The efficiency of a transformer at full load 0.8 pf lagging is 90%. Its efficiency at full load 0.8 pf leading will be

A. Less than 90%

B. More than 90%

C. 90%

D. None of these

17. Which of the following does not change in a transformer?

A. Current

B. Voltage

C. Frequency

D. All of the above

18. A common method of cooling a power transformer is

A. Natural air cooling

B. Air blast cooling

C. Oil cooling

D. Any of the above

19. A transformer transforms

A. Voltage

B. Current

C. Power

D. Frequency

20. Transformer oil must be free from

A. Sludges

B. Sulphur

C. Gases

D. Moisture