Electronic – The \$I^2R\$ loss in transformer is eddy current loss or copper loss

transformer

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

Best Answer

'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.