Comparison of Series-Hybrid Variable-Flux Synchronous Motors Considering Two Types of Rare-Earth Magnets

This paper compares the performance and the magnet costs of a series-hybrid variable flux synchronous motor considering two types of rare-earth magnets. The motor employs two magnets in its topology, one AlNiCo magnet and one rare-earth magnet placed in series. The AlNiCo magnet grade selected is 9. The two rare-earth magnets are Neodymium Iron Boron (NdFeB) and Samarium Cobalt (SmCo). A previously designed, manufactured and tested prototype with the NdFeB magnet is compared against the same machine using SmCo instead. The comparison focuses on different temperatures in a wide range to highlight the reported advantages of SmCo over NdFeB at higher temperatures. The full-load torque, demagnetization, re-magnetization, as well as overload effects are investigated and compared using finite element analysis (FEA). Furthermore, a brief cost analysis based on the current market price of metals and rare-earth materials is presented. A general conclusion about the viability of using SmCo magnets as an alternative to NdFeB is given.