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In permanent magnet motors, the stator resistance and magnetic flux of the magnet change as the temperature increases. These changes result in a change in the maximum torque point per unit ampere (MTPA) of the motor. Without adequate compensation, this leads to a decrease in output torque. For this reason, look-up table (LUTs) are prepared over the temperature range and used for interpolation. This paper proposes a method to compensate for the output torque reduction due to a temperature increase using only a single LUT prepared at a base temperature. First, an estimation of the magnetic flux linkage and the output torque using a single LUT is performed. Second, the problem is modeled as a limited optimization problem to minimize the loss due to the torque reduction. The magnetic flux linkage and output torque are calculated in real time through the fundamental active power. The compensation value is calculated using the Lagrange multiplier method, an optimization technique, using the estimated magnetic flux linkage and output torque. The proposed method is verified by comparing it with other algorithms through simulation and experiment.

This paper proposes hybrid mode control for an asymmetric dual three-phase synchronous motor (ADTP-SM) with separated neutral points in a single-phase open-fault situation. The fault-tolerant control is classified into the maximum torque mode and minimum loss mode. For an arbitrary phase with an open fault, the combination of phase currents for operation in each mode is derived by mathematical analysis. In maximum torque mode operation, a rotational coordinate transformation is proposed to minimize the performance variance according to the speed. In minimum loss mode operation, a stationary coordinate transformation is proposed to control the harmonics of the phase currents. This stationary coordinate transformation can be applied to arbitrary-phase open-fault situations. In addition, the performances with and without harmonic control are compared and analyzed, and the smoothness of the mode conversion is also analyzed. The validity of the proposed coordinate transformations is verified through experiments at various speeds.