Sensitivity analysis of high frequency signal injection based temperature estimation methods to machine, assembling tolerances

The injection of a high frequency signal in the stator via inverter has been proven to be a viable option to estimate the magnet temperature in permanent magnet synchronous machines (PMSMs). Injection of a pulsating d-axis current is especially appealing, as it is insensitive to the speed, L_d and L_q inductance variations. Furthermore, it is suitable both for interior PMSMs (IPMSMs) and surface PMSMs (SPMSMs). Regardless of its promising characteristics, there is a number of issues which can reduce its accuracy, including machine assembling tolerances and rotor lamination grain orientation, which might need to be considered. This paper analyzes the sensitivity of temperature estimation using pulsating d-axis high frequency current injection to rotor eccentricities, PM assembling tolerances and lamination grain orientation. Preliminary results indicate that these issues can have a non-negligible impact on the accuracy of the method¹.