A novel hysteresis loss calculation method of filter inductor in PWM inverters

In this paper, a novel hysteresis loss calculation approach named the double-envelope method is proposed. The method can clearly separate the low-frequency loss and the high-frequency loss. By recording the points where the inductor current reaches minimum or maximum in every switching period, the envelopes of magnetic field H and flux density B in the time domain are acquired, and then the double envelopes on the B-H plane can be obtained. A dynamic minor loop of amorphous core is modeled to calculate the high-frequency loss. With this method hysteresis loss of the AC filter inductor in PWM inverters can be calculated accurately and rapidly. Moreover only the width of the minor loop is needed to measure in experiments, while other parameters can be acquired at the design stage. In order to verify the proposed method, the total loss of an AC filter inductor in a three-level NPC inverter is measured in different switching frequencies and load conditions. The changing trends of the low-frequency loss and the high-frequency loss with currents and switching frequencies are discussed.