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 using a simplified thermal equivalent circuit (TEC) of the WFSMs. Based on the TEC of the WFSMs, an optimization problem is formulated with rotor temperature as the objective function and torque as the constraint. By applying a Lagrangian-function-based optimization process, the optimal current vector that minimizes rotor temperature under a given torque command is analytically derived. To reduce the online computational burden, the optimal operating points are pre-computed and implemented as a look-up table (LUT). As a result, the proposed method expands the available torque region in high-temperature and high-speed operation while ensuring thermal safety of the rotor. The validity of the proposed method is verified through simulation results.
