基于槽极比选择的切向永磁同步电机永磁体涡流损耗抑制措施

Measures to Suppress Eddy Current Loss in Permanent Magnets of Tangential Permanent Magnet Synchronous Motors Based on Slot-Pole Ratio Selection

为抑制切向永磁同步电机的永磁体涡流损耗,基于麦克斯韦方程和本构方程,对永磁体形状进行近似假设,构建了永磁体涡流损耗的估算模型。使用一种基于卡特系数概念的磁导函数来估算由于定子开槽引起的槽下磁感应强度变化。基于五台槽极比分别为1.05、1.20、1.30、2.40和3.60的电机设计方案对理论分析结论进行了验证。在负载电流和两倍负载电流下,分析永磁体损耗,得到了每台电机的径向气隙磁密曲线及其谐波含量。考虑到增加槽极比对定子铁耗和永磁体涡流损耗的削弱效果,给出了电机槽极比选择策略。研究结果表明,增加槽极比能减弱定子槽下磁感应强度变化,从而抑制气隙磁场中低次谐波含量,减小永磁体涡流损耗,使电机运行更加可靠,但也会引入更多高次谐波,从而增加定子铁耗。

To suppress the permanent magnet eddy current losses in tangential permanent magnet synchronous motors, an estimated model for permanent magnet eddy current losses is constructed based on Maxwell equation and constitutive equation with approximate assumptions on the shape of the permanent magnet. A magnetic conductance function based on Carter coefficient concept is employed to estimate the change in magnetic flux density under the slot due to stator slotting. The conclusions of the theoretical analysis are verified based on five motor designs with slot-pole ratios of 1.05, 1.20, 1.30, 2.40, and 3.60, respectively. The permanent magnet losses are analyzed at load current and double load current to obtain the radial air-gap magnetic flux density curve and its harmonic content for each motor. Considering the weakening effect of increasing the slot-pole ratio on stator iron losses and permanent magnet eddy current losses, a motor slot-pole ratio selection strategy is proposed. The results show that increasing the slot-pole ratio can decrease the variation in magnetic flux density stator slot, thus suppressing low-order harmonic content in the air-gap magnetic field and reducing permanent magnet eddy current losses, enhancing the motor's operational reliability, but it also introduces more high-order harmonics, which increases the stator iron consumption.