Mixed-Grade Pole Design for permanent magnet synchronous machines

This paper introduces a design idea of a new kind of pole structure with different magnet grades used in one pole: "the mixed-grade pole design". This structure offers improved demagnetization protection and also brings potential cost savings by optimizing the use of dysprosium in Nd-Fe-B- permanent magnet material. A new demagnetization model with an exponential function is also introduced. The new design idea is compared with a traditional one-grade design by using finite element method electromagnetic simulations combined with the demagnetization model. Finally, the benefits of the new pole structure are discussed.