Patent ID: 8704481

Claim:
A motor drive system, comprising: converter circuitry configured to receive input three-phase alternating current (AC) power from an AC power source and convert the three-phase AC power into direct current (DC) power: a DC bus configured to receive the DC power from the converter circuitry; inverter circuitry configured to receive the DC power from the DC bus and convert it into controlled frequency output AC power for use by a three-phase motor; a common mode choke having a plurality of sets of primary windings and a set of secondary windings separate from the plurality of sets of primary windings, each set of primary windings directly connected to a phase of AC power, wherein the set of secondary windings are not directly connected to a phase of AC power, and wherein the set of secondary windings terminate with a burden resistor; and a controller configured to detect ground faults by monitoring a voltage across the burden resistor.