Frequency converter that manages the regenerative energy of an alternative load and method used with the converter

Abstract

A variable frequency drive (VFD) includes a rectifier, a filter, an inverter, a capacitor bank, and a control circuit. The rectifier converts AC power from a power supply into DC power on a DC bus, which is then filtered. The inverter converts the DC power into three-phase AC power for output to the electric motor. The capacitor bank has one or more capacitors connected to the DC bus. This capacitor bank can store regenerative energy on the inverter's DC bus and supply the stored DC power to the DC bus for conversion back to three-phase AC power to drive the electric motor. The control circuit pre-charges the capacitor bank using AC power from the power supply. The control circuit monitors one or more parameters of the VFD and detects one or more fault conditions associated with the monitored parameters.