Refrigerant compressor drives offering enhanced robustness, efficiency and rated voltage operability

A system comprising:

• a variable frequency drive configured to operate a motor to drive a refrigerant compressor using power from a power source electrically coupled with an input of the drive, the power source having a rated voltage range;
• and
• a controller configured to control operation of the drive and to receive an input signal indicating a drive voltage condition;
• wherein the controller is configured to:
• control operation of the drive to minimize d-axis current and maintain at least a desired motor speed over a first range of the drive voltage condition in the rated voltage range,
• control operation of the drive to increase d-axis current and maintain at least the desired motor speed over a second range of the drive voltage condition in the rated voltage range, the second range extending lower than the first range, and
• control operation of the drive to provide a motor speed less than the desired motor speed over a third range of the drive voltage condition, the third range extending lower than the second range.

An apparatus comprising:

• a variable frequency drive including an AC to DC converter configured to receive AC input power from a power supply and provide DC power to a DC link and an inverter configured to receive DC power from the DC link and provide a PWM output;
• a permanent magnet motor including a plurality of stator windings configured to receive the PWM output, a rotor including at least one permanent magnet, and an output shaft coupled with the rotor and coupled with a refrigerant compressor;
• and
• a controller configured to control the variable frequency drive to meet or exceed a predetermined motor speed with a first d-axis current if the drive is able to provide DC link voltage above a threshold in a rated voltage range, and control the variable frequency drive to meet or exceed the predetermined motor speed with a second d-axis current if the drive is not able to provide DC link voltage above the threshold, wherein the second d-axis current is greater than the first d-axis current.