Does the VDC require a back-up supply like other flywheels?
Unlike the VDC, other high speed flywheels that use a synchronous reluctance generator don’t have the capability to self generate an emergency back-up supply in the event of a power conversion (IGBT) failure. They will rely on the DC bus of the rectifier or need another uninterrupted source. This can be from the output of the UPS if batteries are paralleled with the flywheel on the DC bus, but if the flywheel is the only energy storage on the UPS, then the back-up must be fed from another battery based UPS. The scenario is as follows: A flywheel is used on the DC bus of a UPS. The magnetic bearing controls obtain power from three redundant sources, the DC bus from the rectifier of the UPS, the self-generated DC from the output of the IGBT converter (when flywheel is discharging) and the back-up power from the output AC of the UPS that the flywheel is being used. If the utility fails and then a failure occurs on the flywheel IGBT converter then the rectifier DC bus is not available due
