Indirect estimation of the magnet temperature in a permanent magnet synchronous machine

Abstract

To prevent damage of permanent magnet synchronous machines which are operated close to their (thermal) limits, online monitoring of the permanent magnet temperature is inevitable. Because a direct measurement of this temperature is normally impossible, an indirect estimation method is presented. Based on an electrical model of the machine, a nonlinear observer for the flux linkage and, thus, the permanent magnet temperature is developed. To reduce the sensitivity to deviations from the nominal permanent magnet flux linkage, an online calibration method is proposed. The tractability of the method and the improvement in comparison to the state of the art are demonstrated based on simulation studies and experimental results.