Single phase Transformer:

 Introduction

Transformers are one of the most important components of any power system. It basically

changes the level of voltages from one value to the other at constant frequency. Being a

static machine the efficiency of a transformer could be as high as 99%.

Big generating stations are located at hundreds or more km away from the load centre

(where the power will be actually consumed). Long transmission lines carry the power to the

load centre from the generating stations. Generator is a rotating machine and the level of

voltage at which it generates power is limited to several kilo volts only –a typical value is 11

kV. To transmit large amount of power (several thousands of mega watts) at this voltage

level means large amount of current has to flow through the transmission lines. The cross

sectional area of the conductor of the lines accordingly should be large. Hence cost involved

in transmitting a given amount of power raises many folds. Not only that, the transmission

lines has their own resistances. This huge amount of current will cause tremendous amount

of power loss or I

2

r loss in the lines. This loss will simply heat the lines and becomes a

wasteful energy. In other words, efficiency of transmission becomes poor and cost involved

is high.

The above problems may address if we could transmit power at a very high voltage say, at

220 kV or 400 kV or even higher at 800 kV. But as pointed out earlier, a generator is

incapable of generating voltage at these levels due to its own practical limitation. The

solution to this problem is to use an appropriate step-up transformer at the generating

station to bring the transmission voltage level at the desired value. Obviously when power

reaches the load centre, one has to step down the voltage to suitable and safe values by

using transformers. Thus transformers are an integral part in any modern power system.

Transformers are located in places called substations. In cities or towns you must have

noticed transformers are installed on poles – these are called pole mounted distribution

transformers. These type of transformers change voltage level typically from 3-phase, 11KV

or 6.6 kV to 3-phase 415 V line to line.

Types of Transformers

There are two basic Types of Transformers

1. Single Phase Transformer

2. Three Phase Transformer