中文摘要：

为了能够方便准确地预测无刷直流电动机的机械特性，对电动机的线电流进行了解析计算。根据电动机电路模型和电压平衡方程式，在不忽略电感和电阻的情况下对换相过程进行分析，指出了电磁时间常数和一个状态角换相周期的比值关系是影响相电流瞬时值变化的主要因素。结合相电流瞬时值变化特点将线电流的计算模型分为两种，在此基础上推导了不同情况下电流瞬时值解析表达式，最后借助Matlab软件得到了电动机线电流的解析解。与两台典型无刷直流电动机实测数据进行对比验证，该方法计算精度较高计算且简便、快速，可应用于工程实际。

英文摘要：

In order to easily and accurately predict mechanical characteristics of brushless DC motors, the analytical calculation of the line current was done. Firstly, the commutation process including the case of induction and resistance was analyzed based on the motor circuit model and voltage balance equation. It was analyzed that the ratio of electromagnetic time constant and a commutation cycle period at a state angle was the main reason of the three-phase transient current variations, which makes line current calculation model divided into two parts. Then, the analytical expressions of the phase transient current variations were derived. At last,line current analytical solutions were given by the means of Matlab. The calculating resuhs of two typical prototypes were compared and verified with experimental data. The error was less than 5% ,and the method was easy and fast and had a high precision. As a result, the method in this paper can provide a reference for the motor design and application.