The performance of Permanent Magnet Synchronous Machines (PMSMs) is significantly influenced by the temperature of the Permanent Magnets (PMs). Therefore, accurate knowledge of PM temperature is necessary for control and monitoring purposes. As temperature rises, the magnetic flux strength of PMs, and consequently the torque production capability of PMSMs, diminishes. Moreover, there is a risk of irreversible demagnetization of the PMs. In the case of Variable Leakage Flux PMSMs (VLF-PMSMs), the temperature impacts the machine’s variable leakage property, potentially compromising the accuracy of torque control. The current state-of-the-art PM temperature estimation methods are unsuitable for VLF-PMSMs due to their variable leakage PM flux characteristics. This paper addresses the limitations of existing PM temperature estimation methods by incorporating the variable leakage PM flux property of VLF-PMSMs. The proposed method utilizes PM flux linkage derived from the machine’s response to a small-amplitude, low-frequency, quasi-square-wave current signal. This signal is superimposed onto the fundamental excitation, enabling online temperature estimation without altering the machine’s operation.
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