# Efficiency of Transformer & Maximum Efficiency Condition

It is important to calculate the efficiency of any device. The efficiency of a device determines the performance of how efficiently the device is operated i.e., the capability of a device to give any amount of output energy for given specific input energy. If both input and output values are the same then it can be said that the device is working at 100% (terms of %) efficiency.

## Efficiency of a Transformer :

The efficiency of a transformer is defined as the ratio of output in watt (or kW) to input in watt (or kW), and is represented by the letter 'Ƞ' (and is also known as commercial efficiency). The expression is given by,

A transformer is a highly efficient device and has very small losses. The different losses that occur in a transformer are iron or core losses, copper losses, and stray losses. The stray loss of a transformer is comparatively very small and can be neglected.

Since the remaining losses are not constant, they will be different at different loads, and thus efficiency also varies with the variation of load on the transformer.

## Condition for Maximum Efficiency of a Transformer :

#### To determine the condition of the load on the transformer at which the efficiency would be maximum. Let,Primary input = V1 I1 Cos Φ1Iron loss = PiCopper loss = I12 R01 or I22 R02 For efficiency to be maximum, the above equation should be differentiated with respect to I1 and equating it to zero. Hence the efficiency will be maximum when variable or copper loss (I12 R01 or I22 R02) are equal to constant or iron or core losses (Pi). The current I2 corresponding to the maximum is given by, Similarly, the kVA corresponding to maximum efficiency is given by, Do not enter any spam links and messages