Factors that Influence Transformer No-Load Current Harmonics

The harmonic components of the no-load current are influenced by many factors. These factors are the flux density, the degree of saturation and the core stacking technique. This paper tested many transformers for the no-load current and its harmonic components. A slight over-excitation results in a substantial increase of the THD level. The increase in the THD is not linear with the flux density. Also this work has demonstrated that having a lower no-load current should not be an indication of lower harmonics. The simulation of the transformer through the use of nonlinear inductors and resistors provided reasonable accuracy