Abstract: A system and method for precharging a harmonic filter connected to a power supply line to receive AC power and deliver the AC power to the motor drive unit includes a control circuit. The control circuit is configured to monitor an operational state of the motor drive unit or the power supply line, and generate a first control signal upon a predetermined change in the operational state and a second control signal delayed from the first control signal. The system also includes a charging circuit having a first switch configured to actuate in response to the first control signal to provide a reduced power to at least a portion of the harmonic filter and a second switch configured to actuate in response to the second control signal to provide a non-reduced power to the at least a portion of the harmonic filter.

Abstract: An apparatus for the thermal regulation of an AC drive for providing power to a motor includes a temperature sensor producing a signal indicative of temperature, a heater resistor connectable across a DC link of the AC drive, and a first switch. A controller is operable to monitor the temperature signal and control the first switch to provide power via the DC link to the heater resistor if the sensed temperature is below a predetermined setpoint.

Abstract: A method and apparatus for automatically selecting and employing different DC link pre-charge levels dependent upon different sources providing power to a power conditioning system wherein the different sources are characterized by different source inductances, the apparatus including a source control that selects a first pre-charge level when a utility supply provides power to the system and selects a relatively lower pre-charge level when a generator supply provides power to the system thereby reducing the possibility of inverter disablement due to DC link voltage dips.