Patent ID: 8937796
Filing Date: 2015-01-20
Classification: G01R,H02M

Abstract:
1. A variable frequency drive, comprising: a rectifier providing rectified DC electrical power at a DC output; an intermediate DC circuit coupled with the DC output of the rectifier; an inverter coupled with the intermediate DC circuit and operative to provide variable frequency AC electrical power to a load; at least one filter circuit comprising a plurality of filter capacitors coupled to a neutral node; a feedback circuit coupled with the neutral node and providing at least one neutral feedback signal or value based on a sensed condition of the neutral node; and a capacitor fault detection circuit receiving the at least one neutral feedback signal or value from the feedback circuit and operative to extract a measured frequency component from the at least one neutral feedback signal or value, and to determine whether a fault condition is suspected in at least one of the filter capacitors based at least partially on the measured frequency component.