Magnet temperature estimation of permanent magnet synchronous motor using search coils

Magnet temperature estimation in permanent magnet synchronous machines (PMSMs) is of great importance for high performance control and to avoid PM demagnetization. However, PM temperature sensing is difficult because of its installation in the rotor and is not normally implemented in standard machines. Alternatively, PM temperature could be estimated by some means. Among the others, using search coils (SCs) is a way to easily measure the motor back electromotive force (BEMF) and furthermore to get the estimated magnet temperature according to the flux and temperature linear relationship. In this paper, two methods of PM temperature estimation are proposed. The simulation results show that these two methods have very high accuracy, thus PM temperature can be estimated accurately.