Transformer Questions & Answers-4

Ques-17: Can 4-Winding Single Phase Transformer be auto-connected? 
Ans: Yes. There are occasions where 480 volts single phase can be stepped down to 240 volts single phase by auto connecting a standard 4-winding isolating transformer as shown in Figure-1. If connected in this manner, the nameplate KVA is doubled. For example: A 10 KVA load can be applied to a 5 KVA 4-winding transformer if connected per Figure-1.

Ques-18: How is magnetic leakage reduced?

Ans: Magnetic leakage is reduced to a minimum by sectionalizing and interleaving the primary and secondary windings.

Ques-19: Why are iron cores in transformers made laminated?

Ans: Iron cores are made laminated to reduce eddy current loss.

Ques-20: What is meant by “impedance” in transformers? 

Ans: Impedance is the current limiting characteristic of a transformer and is expressed in percentage.

Ques-21: What is the power factor of a transformer?

Ans: At no load, the power factor of a transformer is very low and lagging, whereas the power factor on load is nearly equal to the power factor of the load, which it is carrying.

Ques-22: What are the advantages of using a transformer in an AC supply?

Ans: The transformer has the following advantages:

1. Voltage can be transformed from low voltage to high voltage for transmission and high voltage to low voltage for distribution without changing the frequency.
2. As the transformer has no rotating parts, there is no factional loss and wear and tear is minimum.
3. A high voltage or an extra high voltage can be transformed easily by providing good insulation.
4. Its maintenance cost is low.
5. Practically it requires very little attention for its operation.

Ques-23: What do you mean by power transformer?

Ans: Transformers that are used on transmission lines for the transmission and distribution of relatively large quantities of energy are called power transformers.

Ques-24: What do you mean by distribution transformers?

Ans: When transformers are used for distributing the energy from transmission lines as well as net-works for local consumption and the secondaries are directly connected to the consumer's load, they are called distribution transformers.

Ques-25: What do you mean by lighting transformer?

Ans: A transformer used to supply a distribution circuit having no motors connected to it is called lighting transformer.