# The $I^2R$ loss in transformer is eddy current loss or copper loss?

As the title say, this is what my text book say. I use Hughes Electrical Electronic Technology 10th edition

The varying flux in the core induces e.m.f.s and hence currents in the core material. These give rise to $I^2R$ losses. These losses are called eddy-current losses

However then when I search through the internet

I found this and it says

Copper loss is I2R loss, in primary side it is $I_1^2R_1$ and in secondary side it is $I_2^2R_2$ loss, where $I_1$ & $I_2$ are primary & secondary current of transformer and $R_1$ & $R_2$ are resistances of primary & secondary winding. As the both primary & secondary currents depend upon load of transformer, copper loss in transformer vary with load.

and

Hysteresis loss and eddy current loss, both depend upon magnetic properties of the materials used to construct the core of transformer and its design. So these losses in transformer are fixed and do not depend upon the load current

They are kinda contradict each other. So, what's the right definition for copper loss and eddy-current loss

• Try to model the real transformer, find the component value of resistances and reactances in place, then measure and solve the relevant equations to find the total losses. May be you can use a common analysis s/w, but it is not so hard to do this by yourself. – GR Tech Jul 29 '15 at 6:07

'Copper loss' is I2R power loss in the windings due to current flowing through them. As this current increases with higher loading, so copper loss also increases as loading increases.

Eddy current loss is power loss in the magnetic core due to current induced into it (each lamination in the core is effectively a shorted turn, but the silicon steel has relatively high resistance which keeps the current down). The induced voltage - and thus current and power loss - doesn't change with loading because the magnetic flux in the core doesn't change. This is also I2R loss, but it is not copper loss.

To summarize, there are two places in the transformer where I2R losses occur - in the magnetic core and in the windings. However, only the windings have a power loss proportional to load current. That loss can rightly be called 'copper loss' because only the windings are made of copper.

• I couldn't have said it better myself +1 – Andy aka Jul 29 '15 at 7:11

According to Hughes Electrical Electronic Technology 10th edition, when the magnetic flux changes in the core, it generates the current in the core material. And, it gives the power loss (I2R). These losses is called eddy current losses. Form internet, it is given that loss in (I2R) means loss in power loss. And power loss depends upon the load. Thus, this definition is similar to your book.

For further detail you can visit here: - http://www.mytech-info.com/2014/08/hysteresis-losses-eddy-current-losses.html

• You are confusing copper losses and eddy current losses. Generally, in transformers, I2R loss is copper loss. – Andy aka Jul 29 '15 at 7:25