Loss Minimization Control of a High-Speed Interior Permanent Magnet Machine

This paper proposes an improvement for the loss minimization control (LMC) of an interior permanent magnet synchronous machine (IPMSM). The LMC is also referred to as the maximum efficiency (ME) control because the maximum efficiency is obtained by minimizing both the core and copper losses. In conventional LMC methods, core loss is represented by a constant equivalent resistance. However, several recent studies showed that the core loss resistance can vary significantly with both load current and speed. If these variations are not included in the LMC, the true maximum efficiency of the motor cannot be achieved. The proposed method of this paper represents the equivalent core loss resistance as a function of load current and speed. It was observed that, by considering the derivative of core loss resistance with respect to current in the LMC trajectory calculation, the total electrical loss of the controlled IPMSM can be reduced. The proposed LMC was experimentally tested on a high-speed IPMSM and compared to the existing LMC and conventional maximum torque per ampere (MTPA) control. A detailed analysis was carried out to identify the operating conditions where the loss minimization control can outperform MTPA in high-speed IPMSMs.