## What is Transformer?

A transformer is an Electrical static device. it consists of two or more stationary coil which is interlinked by a common magnetic circuit for the purpose of transferring electrical energy from one coil to another. The transfer of electrical energy from one coil to another coil takes place without a change in frequency. The transformer is one of the most efficient machines in the world.

### What is Efficiency?

Efficiency is a machine parameter that is used to represent the workability of the machine. it is defined as the ratio of the output of the machine to the input of the machine.it is a unitless and dimensionless quantity.it is represented by a symbol

**(η)**Etta. The efficiency of any machine is always represented in percentage.### efficiency of the transformer

The efficiency of the transformer is defined as the ratio of Electrical Output power to Electrical Input power.

For a given transformer Input Power = Output Power + Loss

There are two types of loss occur in the transformer (a) Copper Loss (b) Iron Loss

i.e Loss = Copper Loss + Iron Loss

Then Input Power for Transformer =Output Power + Copper loss + Iron Loss

For a given transformer of power factor CosƟ_{2} and
I_{2} load Current and V_{2} Transformer Terminal Voltage

Output Power of Transformer will be given as

Output Power = V_{2}
I_{2} CosƟ_{2}

Copper loss for a transformer is variable and it totally depend on load current and is Given as

I_{2}^{2}R_{2} , Here R_{2}
is Total Equivalent Resistance of Transformer.

Iron loss for a given transformer is almost Constant and it
will not vary with load current.Let Iron loss for a given Transformer is P_{i}

Then Input Power for a given Transformer is

Input power = V_{2} I_{2} CosƟ_{2 }+
I_{2}^{2}R_{2} +P_{i}