An evaluation of model-based stator resistance estimation for induction motor stator winding temperature monitoring

In this paper, the feasibility of using an estimate of the stator resistance (R _s) as an indicator of stator winding temperature (T _s) is evaluated. The advantages of resistance-based temperature monitoring over conventional thermal model-based methods are presented. Since obtaining an accurate estimate of R _s is critical for this approach, an investigation of existing R _s estimation schemes, and an analysis showing the sensitivity of model-based R _s estimation due to the uncertainties in motor parameters and variables, are given. It is shown that R _s estimation is difficult during high-speed operation, because estimated R _s becomes sensitive to errors in motor electrical parameters and variables, as the input excitation frequency (speed) increases. A new R _s estimation scheme for the purpose of monitoring the temperature in steady state is proposed. Experimental results on a line-connected induction machine verify the validity of the proposed method and the analysis.