Hysteresis Torque Estimation Method Based on Iron-Loss Analysis for Permanent Magnet Synchronous Motor

In the design process of permanent magnet synchronous motors (PMSMs), the hysteresis torque has so far been ignored under the understanding that it is already small enough. However, for some delicate applications, such as an exoskeleton wearable robot, the hysteresis torque, whose proportion increases under no-load or low-load conditions, needs to be further minimized even though the hysteresis torque has low magnitude. Conventional methods using hysteresis models to calculate the hysteresis torque require a lot of computation resources. Therefore, this paper proposes a simpler method in order to estimate the hysteresis torque using iron-loss experimental data. In the proposed method, the hysteresis torque is derived from the hysteresis loss, which is separated from the iron-loss experimental data by using the modified Steinmetz equation. Finally, the hysteresis torque of the proposed surface-mounted PMSM is measured via experiments to verify the validity of the proposed method. The hysteresis torque is obtained by subtracting the mechanical friction torque from the no-load offset torque. The experimental result is compared with the results obtained from the proposed method.