Design of bridgeless IPMSM to reduce mass of applied permanent magnets

Interior permanent magnet synchronous motors (IPMSMs) are frequently used in industrial applications because their efficiency and power density are both very high. The IPMSM also makes a very good choice for an electric vehicle or hybrid electric vehicle, because the range of operating speeds is wide enough for use in traction applications. Recently, however, as a result of concerns about there being insufficient supplies of rare earth permanent magnets as well as atmospheric pollution caused by the exhaust gases of automobiles, a need has arisen for motor technologies that require fewer magnets and which can offer a higher level of efficiency. In this paper, we propose a bridgeless IPMSM as a means of reducing the number of permanent magnets used in a motor while simultaneously increasing the power density. The bridge structure, which supports the centrifugal forces generated in a motor's permanent magnets as the rotor core rotates, was eliminated. To provide support for the separated pole-pieces and permanent magnets, new supporting structures are proposed. As a result, although the air gap torque of the bridgeless IPMSM is almost the same as that of the conventional design, the mass of the permanent magnets can be reduced by 10%.