Electrically commutated, variable speed compressor control system

An electrically commutated motor (ECM) controller arrangement for controlling the operational speed of a variable speed motor compressor driven by an electrically commutated motor comprising an ECM controller for controlling the speed of the motor, said controller receiving back EMF signals from the electrically commutated motor and producing feedback signals representative of said back EMF, compressor speed logic means for generating a desired motor speed setpont signal, compressor speed calculation means for calculating actual compresor speed signals from said EMF feedback signals produced by said electrically commutated motor controller, error means for monitoring the error between said desired motor speed setpoint and said calculated actual compressor speed signal, said error means producing an error signal indicative of said error, and duty cycle generator means for producing a speed control signal representative of said error signal, said speed control signal being transmitted to the ECM controller for adjusting the speed of the electrically commutated motor driven compressor.