How do you calculate Copper Loss?

Copper loss, or I²R loss, refers to the power loss caused by the resistance of copper windings in the electrical equipment such as


Motors, and


Copper Loss Formula

It is calculated using the following formula:

Copper loss = I2 x R


I - Current flowing through conductor (A), and

R - Conductor’s Resistance (in ohms).

Steps for Calculating Copper Loss

Step-1: Measure or get the current that flows through the copper winding.

Step-2: Measure the resistance (R) of the copper winding. This can be measured using an ohmmeter or estimated using copper’s length, cross-sectional area, and resistivity.

Step-3: To calculate copper loss, use the following formula and substitute current and resistance values.

Solved Example

Consider a transformer winding with resistance of 0.5Ω & a current of 10 amps flowing through it.

Current (I): 10A.

Resistance (R): 0.5 Ω.

Copper loss = 10 x 10 x 0.5

Copper loss = 100 x 0.5.

Copper loss = 50 watts.

Thus, the copper loss is 50W

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