Harmonic content as the indicator of transformer core saturation

The paper proposes a measurement method for obtaining the parameters needed to calculate a reliable indicator of the state of transformer core saturation. The major nonlinear effects in transformer core are saturation, eddy current and hysteresis. Saturation is the predominant effect in power transformers, followed by eddy current and hysteresis effects. In saturation, a transformer core act as a source of current generating harmonics, some of which will flow directly toward the primary and secondary windings. The method is based on harmonic content evaluated of the transformer no-load current with high magnetic flux density subjected. The investigation is done on single phase model core type transformer. The transformer is connected to variable voltage variable frequency (VVVF) source and the investigation is done on the same flux density. The result has been compared with normal frequency supply (50 Hz). The results show that the harmonic content increase significantly when high magnetic flux densities are injected.