The invention discloses a
DC bus pre-charging
system. The
DC bus pre-charging
system includes a first input, a first circuit
branch, a second circuit
branch, and a controller. The first circuit
branch includes a first
contactor between the first input and the AC-to-
DC converter; the second circuit branch has a disconnect switch coupled to the first input, a variable frequency driver (VFD) having 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 pre-charge VFD provides precise control of pre-charge operations such as charge time, current limitation,
short circuit, and ground fault protection, monitors
DC bus capacitance, and verifies the health of the shared DC
bus circuit by initiating diagnostics. In a first mode, the controller opens the first
contactor and closes the second contactor and the open switch to pre-charge the DC
bus circuit using the VFD, and in a second mode, the controller closes the first contactor and opens the second contactor and the open switch.