Patent ID: 8779711

Claim:
A method for controlling the speed of an induction motor including a rotor, said method comprising the steps of: selecting a desired rotor speed; determining motor rotor speed; comparing said motor rotor speed to said desired rotor speed, to thereby generate a speed error signal; applying said speed error signal to a proportional-integral controller, to thereby generate a torque command signal; normalizing said torque command signal to maximum specified torque to thereby generate normalized signals; determining a magnetizing current of said motor; generating a stator current amplitude command signal from said torque command signal; determining ideal volts/Hz value for the motor; subtracting an actual volts/Hz value from the ideal volts/Hz value for the motor, to thereby generate volts/Hz error; multiplying said volts/Hz error by at least a constant and an integral to thereby generate a phase correction signal; generating a current phase precursor signal from said torque command signal; adding said current phase precursor signal to said phase correction signal to thereby generate a signal representing the phase of the stator current; and controlling the switching of current to and from a central capacitor in response to said amplitude command signal and said signal representing the phase of said stator current.