Losses per Unit in Transformers

The interest on the operation of transformers, under conditions of non-linear loads, is to define the additional loss by parasitic currents, mainly in the windings, since this loss will be contributing to the overheating of these transformers.

Transformers feeding non-linear loads generate additional dispersed streams that produce parasitic currents in windings, core and structural parts. Depending on this type of load, one can have a predominance of harmonics of odd order, even or even a combination of them.

Charges that prevail harmonics of the odd-order current of three and the dc component of the load current can generate in some Y-connected transformers an increase in the excitation current, thus increasing the losses in the core.

Harmonic current may happen to be accompanied by a DC component of the load current. This dc component of the load current will increase losses in the transformer core. Depending on this level of the dc component, there may be an increase in the magnetizing current and, consequently, an increase in the audible sound level.

It is expected that the dc component of the load current does not affect the power transfer capability of the transformer.