Aging Condition Monitoring for Aluminum Electrolytic Capacitor in Variable Speed Drives

In this article, an aging condition monitoring method for the aluminum electrolytic capacitor (AEC) is presented. The target AEC is used in an ac-dc-ac variable speed drive (VSD), which usually contains an LCR network composed of a dc choke, an AEC, and a braking branch. The condition of the AEC is monitored through the capacitance value and the equivalent series resistor (ESR) value. The capacitance value and the ESR value are identified by the LCR network response, i.e., magnitude gain and phase shift of the network. The existing components of the VSD are fully utilized instead of adding additional current sensors and active devices. Some potential disturbances in field application, such as three-phase voltage unbalances, are also considered. Experiments are carried out in a 10-kW general-purpose VSD with different AECs. The maximum errors of capacitance value and ESR values identifications are 1.1% and 5.48%, respectively.