A torque measuring method based on encoder for permanent magnet synchronous machine

Direct measuring of mechanical torque is important for permanent magnet synchronous machine (PMSM) testing system. However, mechanical torque is usually measured by torque meters under steady state, which increase the system cost and reduce the system reliability. In this paper, a torque measuring method for PMSM in the back-to-back testing system is introduced based on the encoder signals and the shaft torsional stiffness of the coupling and shaft. Finally, experiments are performed to verity the correctness of the proposed method. The comparison results show that the proposed method is an effective way to measure the torque value in the testing system.