热限制下铁芯饱和对永磁无刷直流电机过载转矩的影响

Influence of Core Saturation on Overload Torque of Permanent Magnet Brushless DC Motor under Heat Restriction

合理的铁芯饱和点可提升高过载永磁无刷直流电机的转矩,转矩提升优化的热限制条件会对最佳铁芯饱和点产生影响。有必要探究热限制下铁芯饱和程度对转矩的影响规律,为提升转矩提供理论参考。为此构建了一种考虑铁芯饱和及电枢反应的等效磁路模型,基于该磁路模型,推导了转矩、损耗和热限制条件的表达式,建立了转矩与尺寸及热限制条件之间的解析关系,分析了不同热限制条件下铁芯饱和程度对转矩的影响,探讨了同时限制电流密度及铜耗密度条件下最大转矩与铁芯饱和程度的关系,对比了不同材料对转矩提升的效果。研究表明,在热限制下存在一个使转矩最大的磁密点,不同热限制条件将影响最优磁密点的大小。分别使用有限元仿真与实验测试对解析结果进行了验证,与解析值相比,仿真结果和实验结果的误差分别小于2%和小于10%。仿真和实验结果表明,所搭建考虑饱和的电磁模型以及分析计算过程均具有较高准确性。

The reasonable saturation point of the iron core can improve the torque of high overload permanent magnet brushless DC motor.The thermal limiting conditions in the optimization of torque rise will affect the optimal core saturation point.It is necessary to explore the influence of the degree of iron core saturation under thermal constraints on the torque in order to provide theoretical references for torque enhancement.Therefore,an equivalent magnetic circuit model considering iron core saturation and armature reaction was constructed.Based on this magnetic circuit model,expressions for torque,losses,and thermal constraints were derived,and an analytical relationship between torque and dimensions as well as thermal constraints was established.The influence of iron core saturation on torque under different thermal constraints was analyzed.The relationship between maximum torque and iron core saturation under conditions that simultaneously limit current density and copper loss density was discussed,and the effects of different materials on torque enhancement were compared.The research shows that there is a magnetic density point that maximizes torque under thermal constraints,and different thermal constraints will affect the size of the optimal magnetic density point.The analytical results are validated using finite element simulation and experimental testing.The errors of the simulation results and experimental results are less than 2%and less than 10%respectively compared to the analytical values.The simulation and experimental results indicate that the constructed electromagnetic model considering saturation and the analysis calculation process have high accuracy.