An Evaluation Circuit for DC-Link Capacitors Used in a High-Power Three-Phase Inverter with Condition Monitoring

This paper presents a condition monitoring method of dc-link capacitors used in a high-power three-phase PWM inverter intended for load life testing with an evaluation circuit consisting a low-voltage inverter. The evaluation circuit provides the equivalent ripple current waveform and dc-bias voltage to those of the high-power inverter. Hence, the monitoring method allows the load life testing with the equivalent condition to the high-power inverter at low cost. Experimental results verify that the monitoring method extracts both the ESR and capacitance changes of a capacitor under test.