两级式无刷混合励磁同步电机的电磁设计及分析

Electromagnetic design and analysis of two-stage hybrid excitation synchronous generator

为利用永磁电机的高功率密度、高效率以及电励磁电机电压易于调节的特性,提出一种混合励磁同步电机.主电机采用混合励磁同步电机,为主电机提供励磁的励磁机采用旋转电枢式交流电机.介绍电机的结构和工作原理,并采用有限元法对电机的磁场分布特征及调磁能力等进行计算和分析.根据理论分析试制样机,测试主电机的调压特性、励磁机的励磁特性以及两级式运行时的空载特性.有限元计算结果以及针对样机的实验数据表明:主电机和励磁机能够可靠地匹配运行;可以在永磁磁场的基础上,通过电励磁有效地调节气隙磁场,满足调压的需求.采用有限元法,研究主电机转子外形以及励磁机的定子齿宽对气隙磁场的影响规律.结果表明:对于主电机,设计适当的转子外缘形状能够有效地降低气隙磁密的总的谐波畸变率(THD),同时应兼顾气隙磁密基波的变化;对于励磁机,选择合理的定子齿宽系数有助于励磁能力的提高.

A hybrid excitation synchronous machine（HESM）was introduced to make use of the high power density and efficiency of permanent machine,and the voltage adjusting ability of electrically excited machine.The HESM adopts two-stage brushless excitation structure design,consisting of a hybrid-excitation main machine and a revolving-armature type exciter.Above all,the machine＇s structure and operating principle were presented.In order to investigate the machine further,the magnetic field distribution,flux regulation ability,and induced electromotive force（EMF）were calculated by finite element method（FEM）.According to the theoretic analysis,aprototype was developed and some experiments were conducted,such as the current amplification capability of the exciter,the voltage adjustment performance of the main machine,and the no-load characteristic of the generator operating two-stage mode.Both FEM calculation results and experimental data show that the air-gap magnetic field,based on the existing permanent magnetic field,can be effectively adjusted by electric excitation for stabilizing voltage.In the end,the influence of some key structure parameters,such as the main machine＇s rotor shape and the exciter＇s stator teeth width,on the air-gap magnetic field was studied with the FEM.The solution results show that,for the main machine,the proper outer edge shape design of rotor can effectively reduce the total harmonic distortion（THD）of air-gap flux density,but the accompanying influence on the fundamental component of the air-gap flux density should be considered at the same time.For the exciter,the reasonable choice of thestator teeth width coefficient contributes to the enhancement of excitation ability.