Torque Compensation Strategy in Interior Permanent Magnet Synchronous Machines With Considering Magnet Temperature

Abstract

Interior permanent magnet synchronous machines (IPMSMs) are increasingly used in various applications, such as electric vehicles and robot applications because of their wide operating region and high torque density. However, this type of motor's performance is influenced by the magnet temperature variation. In particular, the variation of the permanent magnet's residual flux density with the permanent magnet's temperature can affect the IPMSM's torque. Hence, the torque variation with the magnet temperature should be monitored and compensated. This article proposes a new method to compensate for the torque variation with the temperature variation. The proposed method estimates the torque based on the reactive energy, which uses the proposed control algorithms to compensate for the torque variation. The developed method has been demonstrated with experimental results in a special rig, where torque and magnet temperature can be measured. Experimental results showed that torque error at rated torque decreased by 60% by applying the proposed method even in magnet temperature variation from 25.5 to 77.7 degrees C. Additionally, the compensation performance under overload conditions was also validated, and the effectiveness of the proposed method was demonstrated through comparison with conventional method.