Drive circuit for a variable speed fan motor

A method of operating a variable speed fan motor, said method comprising:

• detecting, by a variable speed fan drive circuit, an amplitude of one of a current or a power of a line input signal at a power input stage of an compressor motor;
• selecting, by the variable speed fan drive circuit, a frequency corresponding to the amplitude, at which to operate the variable speed fan motor;
• and
• supplying, by the variable speed fan drive circuit, a fan current signal to stator windings of the variable speed fan motor, the fan current signal having the selected frequency.

A cooling system comprising:

• a compressor motor;
• a variable speed fan motor including fan stator windings;
• and
• a variable speed fan drive circuit coupled to said variable speed fan motor, said variable speed fan drive circuit comprising:
• a fan inverter configured to supply a current signal to said fan stator windings;
• a sensor coupled to a power input stage of said compressor motor and configured to detect an amplitude of one of a current or a power at the power input stage;
• a digital signal processor (DSP) coupled to said fan inverter and said sensor, the DSP configured to:
• receive a sensor signal corresponding to the amplitude from said sensor;
• select a frequency corresponding to the amplitude or at which to operate said variable speed fan motor;
• and
• transmit control signals to said fan inverter to control said fan inverter to supply current to said fan stator windings at the selected frequency.