Does hysteresis curve area include eddy current losses in transformer cores?

[jdstokes]

Hi all,

I'm having a problem with this subject and I was wondering if anyone could confirm/comment on my understanding.

As I understand it, in a typical transformer, an AC current is supplied to a primary coil which induces an oscillating flux within the core. If the core is made of a ferromagnetic material, then there is an energy loss due to the work required to reverse domain orientation in each cycle of the hysteresis curve. In non-ideal ferromagnets, eddy currents are also induced within the core, which, by Lenz's law, act to lower the applied magnetic field which created them. Hence if the oscillator frequency is increased, more eddy currents are induced in the core lowering the effect of the applied field and thus increasing the coercive force. The associated energy loss due to I^2 R heating is reflected in the widening of the hysteresis curve, the area of which corresponds to the energy loss per unit volume of the core in each cycle. This point I am particularly unsure on, does the area enclosed by the hysteresis curve correspond to the total energy loss (hysteresis loss + I^2 R dissipation) or just the energy required to flip the domains?

Thanks

James

 

[Meir Achuz]

The hysteresis curve depends on the iron in the core, and is unchanged.
The I^2R eddy current loss is just like I^2R loss iln the secondary circuit.