Transformer Efficiency

\[\eta=\frac{P_{out}}{P_{out}+P_{core}+P_{cu}}\times100\]

Variables

eta[η]transformer efficiency (%)

Poutoutput power (W)

Pcorecore loss or iron loss (W)

Pcucopper loss or winding loss (W)

Description

What is this formula?

Transformer efficiency measures how much of the input power is delivered as useful output power after subtracting core losses and copper losses.

When to use it

Use this formula when evaluating transformer performance, estimating energy losses, comparing transformer designs, or checking efficiency under a given load condition.

Example

A transformer delivers:

Output power = 50,000 W

Core loss = 400 W

Copper loss = 600 W

Formula:

η = Pout / (Pout + Pcore + Pcu) × 100

Substitution:

η = 50000 / (50000 + 400 + 600) × 100

Result:

η = 98.04%

Applications

Transformer performance analysis

Power distribution systems

Energy efficiency studies

Transformer loss estimation

Electrical machine testing

Note

This formula assumes that the main transformer losses are represented by core loss and copper loss. In real transformers, losses vary with voltage, frequency, load current, temperature, and harmonic distortion, so measured efficiency may differ slightly from this simplified calculation.