A hybrid method to determine the average permanent magnet temperature in an interior permanent magnet synchronous machine

In this paper, a hybrid method to study the permanent magnet temperature in an interior permanent magnet machine (IPMSM) is introduced. The flux-observer based method is applicable for operating points at medium and high speeds and is highly sensitive to the accuracy of the involved machine parameters. The temperature estimation using thermal models requires knowledge of the machine assembly and the heat transfer parameters, for which optimizations and validations of the model are necessary. Consequently, the flux observer and the thermal model are used together to allow a continuous estimation of the temperature development also at zero and low speeds. Cross validations with measurements on a test bench show a high precision of the magnet temperature estimation with a maximum error of 6K for the studied load profile. This work presents a practical approach with low assembly effort to acquire the thermal state of the rotor in IPMSMs.