Core Loss Calculation of Symmetric Trapezoidal Magnetic Flux Density Waveform

Existing empirical core loss models for symmetric trapezoidal flux waveform (TzFW) still suffer some issues such as the inaccuracy and the complexity. These issues are mainly due to the lack of an accurate model of the relaxation loss generated during the off-time. This paper aims to understand the relaxation loss and develop an accurate model using the superposition technique. The developed model gives an accurate prediction of the on-time loss and the relaxation loss and shows the dependency of each on the duty cycle. The research shows that the core loss at low duty cycle is several times the core loss at full duty cycle. The developed model is verified with experimental results and compared to the Improved Steinmetz equation (ISE). The model error is reduced to lower than 15% compared to 50% of the ISE. Finally, an easy method using multiplication factors with the ISE model is given to simplify the developed model.