This paper proposes a copper-loss optimizing control method for a wound field synchronous motors (WFSMs) considering rotor temperature. In a WFSMs, the rotor temperature rises because field flux is essential for torque generation. Therefore, this paper proposes a method to maintain the rotor temperature below the maximum allowable value. The rotor temperature is monitored in real-time based on a simplified thermal equivalent circuit (TEC) of the WFSMs, and optimal copper-loss control conditions are determined to ensure that the maximum temperature is not exceeded under the required torque command. In addition, the optimal copper-loss current combination is analytically derived by solving the quartic equation using the general solution of Ferrari’s method. To reduce computational load, the proposed method is implemented using a look-up table (LUT) in which the optimal copper-loss operating points for the required torque are pre-calculated. As a result, the available torque region in high-temperature and high-speed operation is expanded, and overall efficiency is improved. The validity of the proposed method is verified through simulation results.
