Rotor Magnet Temperature Estimation Using Magnet Flux and Energy Information

This paper proposes a rotor magnet temperature estimation method using both the magnetic flux and energy. Firstly, the flux and energy data with respect to the d- and q-axis currents at three rotor temperatures are gathered to construct the 2D tables of temperature coefficients at the base speed. Secondly, this paper suggests a mode transition logic to use the flux or the energy depending on both the current magnitude and the rate of change (ROC) of the energy over temperature. Because the d-axis magnetic flux signal is prone to the inverter nonlinearity when the current magnitude increases. On the other hand, the q-axis energy signal is not available as a temperature indicator when the current magnitude and energy gets smaller than the minimum required values. Thirdly, a method to compensate for the motor and inverter nonlinearity is introduced. The 2D tables of the d-axis flux and q-axis energy nonlinearities are built at high speed, so that the nonlinearity effect varying according to the speed can be addressed. An experimental setup was constructed using the telemetry device to measure the rotor magnet temperature for comparison. The experimental results are provided to show the effectiveness of the proposed method.