Methods for Determining the Magnetic State of Permanent Magnets on Rotors, in a Perspective of End of Life of Electric Machines

Abstract

Faced with the rising number of electric vehicles, the recycling of permanent magnet (PM) rotors of electrical machines is a pivotal concern since PM, for this, application are generally made with Critical Raw Materials, i.e. rare earth materials. Therefore, the development of effective End of Life strategies for PM is essential to mitigate the environmental impact associated with their production and meet the rising demand sustainably. This paper presents a method to reconstruct the magnetization state of the PM on site within the rotor based on external field measurements. This information will be really useful to evaluate the PM state of health in order to evaluate the possibility of reuse of the rotor or to recycle the PM. The process of reconstruction is based on an inverse method and it has been fully simulated using A Finite Element (FE) model for the rotor. It is shown on different rotor topologies (surface PM mounted rotor, PM buried rotor…) that it is possible to determine the magnetization state of the PM.