Abstract: A precharge system for precharging a DC bus circuit includes a first input, first and second circuit branches, and a controller, where the first circuit branch includes a first contactor between the first input and an AC to DC converter, the second circuit branch has: a disconnect switch coupled to the first input; a variable frequency drive (VFD) with an AC input coupled to the disconnect switch; an inductor coupled to an AC output of the VFD; and a second contactor coupled to the inductor. The precharge VFD provides precise control of the precharge operation such as charging time, current limiting, short-circuit and ground fault protection, monitoring DC Bus capacitance and verifies the health of the shared DC bus circuit through startup diagnostic.

Abstract: A precharge system for precharging a DC bus circuit includes a first input, first and second circuit branches, and a controller, where the first circuit branch includes a first contactor between the first input and an AC to DC converter, the second circuit branch has: a disconnect switch coupled to the first input; a variable frequency drive (VFD) with an AC input coupled to the disconnect switch; an inductor coupled to an AC output of the VFD; and a second contactor coupled to the inductor. The precharge VFD provides precise control of the precharge operation such as charging time, current limiting, short-circuit and ground fault protection, monitoring DC Bus capacitance and verifies the health of the shared DC bus circuit through startup diagnostic.

Abstract: A method and apparatus for identifying a ground fault in a motor drive system that includes at least one three phase power conditioner that is linked to three phase supply lines and to positive and negative DC buses, the method comprising the steps of controlling the power conditioner at an operating frequency to convert power, while controlling the power conditioner to convert power, controlling the power conditioner to apply a common mode signal on each of the three phase supply lines where the common mode signal has a frequency that is different than the operating frequency, sensing the common mode signal on at least one of the three phase supply lines and when the common mode signal on the at least one of the three phase supply lines is greater than a threshold level, indicating that a ground fault has occurred.

Abstract: A method and apparatus for identifying a ground fault in a motor drive system that includes at least one three phase power conditioner that is linked to three phase supply lines and to positive and negative DC buses, the method comprising the steps of controlling the power conditioner at an operating frequency to convert power, while controlling the power conditioner to convert power, controlling the power conditioner to apply a common mode signal on each of the three phase supply lines where the common mode signal has a frequency that is different than the operating frequency, sensing the common mode signal on at least one of the three phase supply lines and when the common mode signal on the at least one of the three phase supply lines is greater than a threshold level, indicating that a ground fault has occurred.