Two Marks Questions with Answers

 Two Marks Questions with Answers

Q. 1 List out the various applications of an autotransformer. [Refer section 7.1.8] AU: May-05, 06, 09, 15, Dec.-13

Q. 2 Why is the auto-transformer not used as distribution transformer ? AU: May-07

Ans. : The transformers used to step down the transmission voltage to the distribution voltage or distribution voltage to standard service voltage are called distribution transformers. Hence the voltage ratio of such transformers is very high. Similarly the isolation between primary and secondary is necessary.

But the autotransformers are economical only when the voltage ratio is less than 2. Similarly the autotransformers cannot provide isolation between primary and secondary. Hence autotransformers cannot be used for distribution purpose.

Q. 3 What are the advantages of autotransformer over two winding transformer? [Refer section 7.1.6] AU: May-08, Dec.-08,12,13

Q. 4 Compare two winding transformer and autotransformer.

Ans. :

Q. 5  State the different connections of three phase transformer. AU: Dec.-02, 06, May-13

Ans. : The different connections of three phase transformer are, i) Star-Star, ii) Star-Delta, iii) Delta-Star, iv) Delta-Delta, v) Open Delta or V connection and  vi) Scott connection or T-T connection.

Q. 6 State the advantages of three phase transformers. [Refer section 7.2.1]

Q. 7 State the advantages of bank of single phase transformers used as a three phase transformer.

Ans. : 1. It may be possible to have transformer in a bank with higher kVA rating than the other so that unbalanced load can be supplied.

2. When one of the transformers is out of service then also system operation is possible with remaining two transformers using V-V connection at reduced capacity.

3. In a bank of 3 single phase transformers, only one single phase transformer is to be kept as spare rather than to keep a whole 3 phase unit which is expensive. Thus requirement of standby is less in case of bank of three single phase transformers.

4. It is more convenient to transport single phase transformers than three phase transformer.

Q. 8 State the advantages and disadvantages of star-star connection. [Refer section 7.3.1]

Q. 9 State the advantages and disadvantages of delta-delta connection. [Refer section 7.3.2]

Q. 10 State the advantages and disadvantages of star-delta connection. [Refer section 7.3.3]

Q. 11 State the advantages and disadvantages of delta-star connection. [Refer section 7.3.4]

Q. 12 State the choices of three phase transformer connections. [Refer section 7.5.1]