Auto Transformer MCQ

16. What is the power transferred conductively from primary to secondary of an auto-transformer having transformation ratio of 0.8 supplying a load of 3 kW?

1. 2.4 kW
2. 0.6 kW
3. 0.27 kW
4. 1.5 kW

17. What is the power transmitted inductively in an auto-transformer which supplies a load at 161 Volts with an applied primary voltage of 230 volts?

1. 35% of the input
2. 70% of the input
3. 15% of the input
4. 30% of the input

18. A two-winding transformer is converted into an auto-transformer. If we apply additive polarity and subtractive polarity for the connections, then the secondary voltage is 2640 V and 2160 V respectively. What is the ratio of primary to secondary voltage of the original transformer?

1. 54 : 66
2. 66 : 54
3. 1 : 10
4. 10 : 1

19. What is the efficiency of an auto-transformer in comparison to that of a two-winding transformer of the same rating?

1. Slightly less than that of a two-winding transformer
2. Same as that of a two-winding transformer
3. More than that of a two-winding transformer
4. As low as 1/5th of the efficiency of a two-winding transformer

20. A two-winding transformer is used as an auto-transformer. The kVA rating of the auto-transformer compared to the two-winding transformer will be

1. 2 times
2. 3 times
3. same
4. 1.5 times

21. In case of auto-transformers, which of the following statements are correct?

1. An auto-transformer requires less copper as compared to a conventional, 2-winding transformer of the same capacity.
2. An auto-transformer provides isolation between the primary and secondary windings
3. An auto-transformer has less leakage reactance as compared to the conventional, 2-winding transformer of the same capacity.

Select the correct answer using the codes given below:

1. 1 and 2
2. 1, 2 and 3
3. 2 and 3
4. 1 and 3

22. The machine in which energy transfer happens both through induction and conduction,is called

1. Two winding transformer
2. Auto transformer
3. Three-phase induction motor
4. Single-phase induction motor

23. The essential feature of an auto-transformer is that it

1. is more suited for single-phase supply
2. is completely automatic in its operation
3. uses only one winding
4. is particularly suited for situations where voltage transformation ratio exceeds unity

232. The kVA rating of an ordinary 2-winding transformer is increased when connected as an autotransformer is due to

1. Transformation ratio is increased
2. Secondary voltage is increased
3. Energy is transferred both inductively and conductively
4. Energy is transferred inductively