稀土永磁无刷直流电机弱磁机理研究

Exploring Flux-Weakening Effect for a REPM Brushless DC Motor

针对稀土永磁无刷直流电机绕组导通角超前产生弱磁效果进行分析,提出一种等效气隙磁密分析方法,通过研究超前导通角的变化与导通相绕组下磁通的关系,推导出对应磁状态的导通相绕组下的磁通变化是稀土永磁无刷直流电机能够弱磁运行的关键。同时通过定转子空间磁势分析研究了电枢反应对弱磁效果的影响。研究表明,电枢反应对于表贴式径向励磁稀土永磁无刷直流电机磁场起一定削弱作用,但作用十分有限。实验结果给出了一种稀土永磁无刷直流电机弱磁效果的机械特性曲线,与理论分析较为吻合。

Aim. It is well known that armature reaction can achieve some flux-weakening. Our exploration shows that something else achieves far more flux-weakening. That something else is the magnetic flux variation of corresponding conduction phase windings as the conduction angle varies. In the full paper, we explain our exploration in some detail; in this abstract, we just add some pertinent remarks to listing the three topics of explanation. The first topic is： the equivalent air-gap magnetic flux density analysis method. In this topic, we analyze the relations between anticipated conduction angle and the operating speed or torque of a brushless DC motor （BLDCM）, as summarized in Figs. 2 through 5. The second topic is ： the space magnetic force analysis method. In this topic, we study the influence of armature reaction on the flux-weakening effect through analyzing the space magnetic force of BLDCM＇s stator and rotor. The third topic is： experimental results and their analysis. The theoretical analysis shows that, compared with magnetic flux variation, armature reaction has far smaller de-magnetizing effect during flux-weakening operation; the BLDCM＇s rotation speed has only 11.87 % rise, indicating that armature reaction is weak in demagnetization. Also in this topic, we did experiments with the 40W/27V REPM BLDCM, experimental results; as shown in Fig. 9, its flux weakening operating region achieves 2. 58. The experimental results are in good agreement with theoretical analysis.