PMLSM推力波动抑制分段斜极方法研究

为了有效抑制推力波动,提高电机定位、出力及速度精度,分析了永磁直线同步电机(PMLSM)推力波动特点,指出采用分数槽及电枢长度调节之后,2、4、6次波为PMLSM推力谐波主要成分,与以12倍次为主的齿槽力波动不同;在对分段斜极方案优点分析、推力谐波斜极系数计算、电磁推力削弱系数计算的基础上,对斜极角选取策略进行了分析,结果表明:因推力波动的成因和表现不同,直线电机与旋转电机最佳斜极角选取公式有差异;阐述了利用二维有限元计算三维非对称斜极运动模型的方法,用该方法对斜极系数-分段数关系、斜极系数-斜极角关系进行了计算,验证了PMLSM次级永磁分段数及斜角选取的分析.结果表明:永磁体2分段并取30°斜角可使推力波动下降到61.3%且保持96.8%出力.

Step skewing method for thrust ripple reduction of PMLSM

The characteristics of thrust ripples of permanent magnet linear synchronous motor(PMLSM) were analyzed to effectively reduce thrust ripples,optimize positioning accuracy,thrust accuracy and speed accuracy.The results show that after fractional slot design and armature length optimization,the 2nd,4th and 6th harmonics,not the 12th harmonic of cogging force,become the main components of the thrust ripples.After the study of the advantage of step skewing,the skewing coefficients of harmonics and the weakening coefficients of electromagnetic thrusts were investigated.Then the best skewing angle was discussed.It is concluded that the skewing angle selection principles are different for rotary and linear motors because of different ripple origins and performances.At last the analysis method for asymmetric skewing model with a two-dimensional finite element method(FEM)was introduced,with which the skewing coefficients with different step numbers and skewing angles were computed.The resulting curves validate the theories for step selection and skewing angle optimization.It shows that PMLSM with 2-step magnets of 30 degree skew angle can reduce the thrust ripple to 61.3% while keeping the output thrust at 96.8%.