Abstract: A converter includes a converter circuit that converts the AC voltages supplied from the ?-connection and the Y-connection, which are two systems of a 12-phase rectifier transformer, to a DC voltage; a current detector that detects the current in a DC bus output from the converter circuit; and an imbalance detection unit that detects the occurrence of an imbalance between the current output from the ?-connection and the current output from the Y-connection, the currents being detected by the current detector. The converter can detect an imbalance that occurs between the current flowing in the diode bridge on the ?-connection side and the current flowing in the diode bridge on the Y-connection side.

Abstract: A testing system for a ground fault detection system of an electrical system of a machine is disclosed. The testing system has a low voltage power source, the low voltage power source capable of operation that is independent from a high voltage power source of the machine. The testing system also has a variable current source that is permanently connected to a positive voltage bus or to a negative voltage bus of the electrical system of the machine, where the machine operates self-sufficiently. The testing system also has a controller connected to the variable current source. The testing system also has an input device, where the input device is connected to the controller.