Self generative PWM voltage source inverter induction motor drive

An induction motor drive which comprises:

• a PWM voltage source inverter fed by a fixed d.c. voltage;
• stator winding current control means including means for sensing the current flowing in the motor stator windings, means for generating current error signals proportional to the difference between the sensed stator winding currents and a set of alternating current command wave forms and means for effecting the voltage source inverter in response to said current error signals to provide control of the motor stator winding currents;
• voltage sensing means coupled to the motor stator windings and being operable to generate a set of cyclic feedback signals related in both frequency and phase to the fundamental of the motor stator winding voltages;
• power factor control means connected to receive said cyclic feedback signals and being operable in response thereto to generate the alternating current command wave forms to said stator winding current control means, the power factor control means being operable to control the phase of the alternating current command wave forms relative to the motor stator winding voltages to thereby maintain the power factor of the electric power applied to the induction motor at a commanded level and including inverter control means which is operable in response to a stator current amplitude command to control the amplitude of the alternating current command wave forms;
• means coupled to the induction motor for generating a power factor command to the power factor control means which reflects the magnetic flux error from which the induction motor is to operate;
• and
• input means coupled to the inverter control means for generating a stator current amplitude command.