An Estimation Method of Rotational Direction and Speed for Free running AC Machines without Speed and Voltage Sensor

摘要

This paper presents an estimation method of rotational direction and speed for free running AC machines driven by an inverter without speed and voltage sensor. The method has four estimation modes, and the method utilized only the measured phase current of machines. The amplitude of current during the estimation is suppressed to lower levels such as the exciting current, which is smaller than the rated value. Good performance of this method is confirmed by the experiment.