Inverter control during overload and following power interruption

A frequency control method is presented that interacts with a voltage-controlled current-regulated pulse-width modulation (CRPWM) inverter to provide operation during and after a momentary overload and reconnection to a de-energized rotating motor under load. This is accomplished without overcurrent trips, knowledge of motor parameters, or velocity feedback. In addition, a stability study of the synchronous voltage-controlled CRPWM inverter is performed that determines the effects of controller, motor, and load variations on the region of instability. Results reveal that the synchronous voltage-controlled CRPWM inverter and traditional open velocity loop PWM inverter have similar unstable regions with respect to operating frequency.<>