The amount or the intensity of Power loss in a transformer, determines the efficiency of the transformer. The efficiency can be understood in terms of power loss between primary and secondary of a transformer.
Hence, the ratio of power output of secondary winding to the power input of primary winding can be stated as the Efficiency of the transformer. This can be written as
Efficiency=PoweroutputPowerinput×100%Efficiency=PoweroutputPowerinput×100%
Efficiency is generally denoted by η. The above given equation is valid for an ideal transformer where there will be no losses and the whole energy in the input gets transferred to the output.
Hence, if losses are considered and if the efficiency is calculated in practical conditions, the below equation is to be considered.
Efficiency=PoweroutputPoweroutput+Copperlosses+Corelosses×100%Efficiency=PoweroutputPoweroutput+Copperlosses+Corelosses×100%
Otherwise, it can also be written as
Efficiency=Powerinput−LossesPowerinput×100Efficiency=Powerinput−LossesPowerinput×100
1−LossesInputPower×1001−LossesInputPower×100
It is to be noted that the input, output and losses are all expressed in terms of power, i.e., in Watts.
Example
Consider a transformer having input power of 12KW which is rated at 62.5 amps current having equivalent resistance of 0.425ohms. Calculate the efficiency of the transformer.
Solution −
Given data
- Input power = 12KW
- Rated current = 62.5 Amps
- Equivalent resistance = 0.425 ohms
Calculating the loss −
The copper loss at rated current is I2R = (62.5)2 (0.425) = 1660W
We have
Efficiency=Powerinput−LossesPowerinput×100Efficiency=Powerinput−LossesPowerinput×100
Hence,
η=12000−166012000×100η=12000−166012000×100
η=1034012000×100η=1034012000×100
η=0.861×100=86%η=0.861×100=86%
Hence the efficiency of the transformer is 86%.
