Iron loss evaluation of AC filter inductor core in a PWM inverter

Iron loss of an AC filter inductor used in a PWM inverter is discussed based on a dynamic minor loop method developed by the authors. A distinctive feature of the dynamic minor loop method is that the instantaneous iron loss of the AC filter inductor can be measured during every switching period of the inverter, and the instantaneous iron loss distribution during one cycle of the output frequency can be produced using this data. The shape of the distribution changes with both the modulation method of the inverter and the load conditions, so that this method is suitable for characterization of the iron loss. Iron loss of the AC filter inductor can be categorized as two types; one type is high frequency loss, which is caused by the switching ripple current, and the other is low frequency loss caused by the low frequency output current. High frequency loss is usually much higher than low frequency loss; therefore, mainly the high frequency loss was evaluated in this study. The instantaneous iron loss of an AC filter inductor and the total loss under various conditions of the PWM inverter are measured, and the relationships between the output current and the iron loss, the DC-bus voltage and the iron loss, and the power factor and the iron loss are discussed.