中文摘要：

采用等效磁路的方法设计一台42V汽车用永磁发电机，并对各种参数下的电机效率进行了分析。在此基础上，分析研究单-变量、两变量以及多变量对电机效率的影响。选择的变量包括气隙长度、铁心有效长度、定子外径、永磁体径向长度等参数。合理选择各参数可以有效提高电机效率。对汽车用永磁发电机的参数计算和优化设计等提供了一定的理论参考。

英文摘要：

An equivalent magnetic circuit method was used to model and analysis a 42V permanent magnet alternator. The equivalent magnetic circuit for a pole pair of a PM alternator was given and the flow chart of the design of the alternator was shown. A 42V permanent magnet alternator was designed. On this basis, the performance of the alternator was analyzed in terms of various parameters including a single variable, two variables and multi-variables using the equivalent magnetic circuit method. A reasonable combination the variables of the air-gap length, the iron effective length, the stator outer diameter, permanent magnet radial length can effectively improve the efficiency of the alternator. Analysis results obtained by various methods can provide a basis and reference for the parameter computation and design optimization of the permanent magnet alternator.