Calorimetric Power-Loss Measurement of a High-Power Film Capacitor with Actual Ripple Current Generated by a PWM Inverter

This paper proposes a calorimetric power-loss measurement method suitable for a high-power film capacitor used in the dc link of a high-power three-phase PWM inverter. The measurement method is characterized by using a thermally-insulated container and an evaluation circuit for dc-link capacitors. Introduction of the thermally-insulated container achieves an accurate power loss measurement that is of the order of 1 W. The evaluation circuit provides the equivalent ripple current waveform and dc-bias voltage to those of the high-power three-phase PWM inverter although its power rating is 1/24 of the high-power inverter. This combination makes it possible to measure the power loss of the capacitor under actual voltage/current condition at low cost. Experimental results obtained from a 1200-V 210-kVA system verify the viability and effectiveness of the proposed method.