Accurate determination of permanent magnet motor parameters by digital torque angle measurement

This article presents a novel test method to determine the important load dependent reactance parameters Xd, Xq, and magnet‐excited voltage E0 of permanent magnet (PM) motors. The results bring forward a clear picture of the impact of the previous assumption of constant E0 on the value of Xd. As improved accuracy and fast data sampling are required for online control, the traditional method for measuring torque angle is deficient. To this end, a new microprocessor‐based digital torque angle measurement system was designed and built. At the same time, a scheme for accurately positioning the zero torque angle is proposed without referring to the interior structure of a motor. The proposed techniques have been successfully employed for a 1 hp laboratory permanent magnet motor.