Predicting and Preventing Demagnetisation in Permanent Magnet Motor Drives

This paper presents a case study. An existing PMSM design was moved to a new application with higher operating temperatures and higher peak currents. Substantial rotor demagnetisation was observed in the new application where no problem had been observed previously. The causes of the demagnetisation are presented, along with analysis of the magnetic circuit. The analysis is correlated with experimental results. The effects of machine design are considered. A solution to the problem is proposed and tested and again the analysis is correlated with the results. Finally some guidelines are proposed for the design of robust PM machines and the associated drive electronics.