Bonded Nd-PM Claw-Pole Synchronous Motor Drive for Traction Applications: Benefits and Challenges

The demand for high-energy sintered Permanent Magnets (PMs) is experiencing rapid growth in the electric transportation and high-power wind generation. Furthermore, due to the limited supply of rare earth PMs, there is a global exploration of alternative propulsion systems that rely on reduced or no PM usage. This paper presents a solution using a less expensive bonded NdFeB (B r =0.8T) magnets in a PM claw-pole synchronous motor. The cost/kg for bonded Nd magnet is about 50% of that of conventional sintered NdFeB (B r =1.15T) magnets. Additionally, because of the lower mass density of bonded magnets, the cost is reduced up to 50% for the same airgap flux density at higher volume of magnet using standard fabrication technology. This paper introduces a preliminary electromagnetic design of a 60-kW motor and a case study, augmented by comparison of the torque-speed and power-speed characteristics. In addition, using a 3-D finite element analysis (3D-FEA), flux density distributions under no load and at base speed, average torque, and EMF have been computed. Moreover, other metrics such as efficiency, torque and power densities, drive efficiency, structural response, and active cost of both bonded and sintered PM claw pole motors have been compared.