Patent ID: 8654494

Claim:
A voltage-limited auxiliary bus comprising: a DC auxiliary bus comprised of a positive conductor and a negative conductor; a chopper, wherein the chopper is normally in a non-conducting state; a resistor in series with the chopper, wherein the chopper and the resistor are connected between the positive conductor and the negative conductor of the DC auxiliary bus; an alternating current (AC) electrical source and a converter, the converter connected to the AC electrical source through an AC auxiliary bus, the converter connected to the DC auxiliary bus, the converter configured to convert AC electrical energy from the AC electrical source to DC electrical energy for the DC auxiliary bus; and a control device for controlling a conducting state of the chopper, wherein the control device causes the chopper to begin conducting when an overvoltage is detected on the DC auxiliary bus, wherein said conducting limits the voltage on the DC auxiliary bus and at least a portion of the AC auxiliary bus and dissipates energy from the overvoltage; wherein the converter is configured to clamp an AC voltage on at least a portion of the AC auxiliary bus to a DC voltage on the DC auxiliary bus when a current is flowing on an AC side of the converter during the conducting of the chopper.