Modeling of PWM-Induced Iron Losses With Frequency-Domain Methods and Low-Frequency Parameters

The high-frequency iron losses caused by sinusoidal flux density variations with frequencies ranging from 2.5 to 40 kHz, amplitudes from 1 to 70 mT, and dc-biased magnetic inductions from 0 to 1.62 T are measured with the dual-transformer system. Then, in this article, a simple frequency-domain model is proposed based on the linear fitting and two-dimensional interpolation methods for engineering applications. In addition, another two frequency-domain models, respectively, considering and neglecting the excess losses are investigated and compared for the high-frequency iron-loss modeling, which only need low-frequency parameters and contain the physical interpretation to the variation of high-frequency iron-loss coefficients with the frequency, ac flux density amplitude, and dc-biased magnetic induction. The iron losses generated by the unipolar and bipolar pulsewidth modulation (PWM) voltages with different switching frequencies and modulation factors are measured to testify the three models. It is shown that the three models in this article are more accurate than the previously proposed one for calculating the PWM-induced iron loss by considering the variation of model parameters with the dc-biased magnetic induction and ac flux density amplitude, especially when silicon steel sheets reach the saturation.