Optimisation of an Automotive Permanent Magnet Motor with Low Coercivity Recycled Magnets Considering Demagnetisation

Abstract

Permanent Magnets (PM) containing Rare Earth Elements (REE) are widely used in the automotive industry to achieve power-dense and efficient motor designs. However, their supply chain is highly vulnerable and subject to significant price fluctuations. Consequently, recycling PMs with REEs presents a sustainable alternative to mitigate these issues, but the recycling process can weaken the magnetic properties of these magnets. The higher risk of demagnetisation, lower temperature tolerance, and reduced flux density make it challenging to achieve power-dense and efficient motor designs. Therefore, this article introduces an optimisation methodology for permanent magnet motors accounting for demagnetisation. Optimisations of five rotor topologies were carried out first, and considering magnet mass, power capability, and the resistance to demagnetisation, the V-Blockshaped rotor topology was identified as the best candidate. The selected candidate accomplished all the requirements, with a high power capability and no demagnetisation.