Effects of harmonics on converter transformer load losses

Losses were measured during short-circuit tests on a 262.5 MVA, three-phase, five limb converter transformer at various frequencies from 50 Hz to 1 KHz. Using these and the calculated values of the harmonic currents produced by the AC/DC converter, load losses were determined. Variations of these losses with the converter firing angle, with the transformer reactance and with the load were studied. A simple method of loss calculation which has the potential for application at the design stage was developed.<>