中文摘要：

电机内电磁力密度的精确计算对电机的结构设计及故障诊断具有重要意义，然而目前尚缺乏简便实用的电磁力密度数值计算方法。为此，在有限元分析方法（finite element method，FEM）和局部虚位移法的基础上，按虚功等效的原则建立由等效节点力进一步计算介质内部电磁力密度和不同介质交界面处电磁应力的数学模型，进而推导了二维平行平面场条件下的具体计算公式。实例计算表明，与其它算法相比，该方法在相同剖分下具有较高的计算精度，且计算结果受剖分的影响较小。

英文摘要：

Precise calculation of magnetic force density in electric machine is significant to structure design and fault diagnosis, while there is no simple and convenient numerical method of computing magnetic force density. Therefore, on the basis of finite element method （FEM） and local virtual work method, a mathematical model was built according to the principle of virtual work equivalent, so as to calculate the magnetic force density inside medium or magnetic stress on the interface of different mediums after the equivalent node forces were solved. A concrete formula for 2D problems was deduced. Application shows that the method has higher calculation accuracy and its performance is hardly influenced by different meshes.