低压大电流车载发电机改善换向研究

Improved Commutation for Low-Voltage High-Current Vehicle Generators

为了解决低压大电流车载发电机换向困难和火花等级高的问题,采用非均布和非对称磁极结构、加装非均匀换向极、嵌下具有均压作用的单波绕组和倾斜电刷等措施,以降低换向区磁场和换向电势.应用电磁场有限元方法对车载发电机进行空载和负载内部磁场分析与计算,研究电机内磁力线的分布和气隙磁场波形,结果表明:尽管主磁极极靴和主磁极在空间是不等距分布的,但是主磁极所建立的气隙磁场仍然是对称和均布的,可确保提供适合机电能量转换的媒介空间;通过对比有换向极作用和没有换向极作用时电机内磁场分布和气隙磁场波形,换向极起到了降低换向区磁感应强度的作用,特别是对换向区磁场的细化分析和展示,发现有换向极作用时,换向电势平均降低了42.3%,即有明显改善换向的效果,火花实验也说明换向得到了改善.设计方案可以改善发电机换向条件,降低火花等级,抑制电磁干扰,有利于提高车载电气系统运行稳定性、可靠性和安全性;研究结果为低压大电流车载发电机研制提供技术支持.

To find a way to improve commutation and decrease the level of spark for low-voltage high-current vehicle generators, non-uniformly distributed and asymmetrically constructed magnetic poles, non-uniform commutating magnetic poles, single wave windings with voltage averaged and oblique brush, are adopted. The distribution of the flux line, the wave of the air gap magnetic field, and analysis inner magnetic field under loaded and unloaded conditions are analyzed respectively with finite element method. The results reveal that the magnetic field induced by the main poles is still symmetric and uniform in spite of the asymmetric structure, so it ensures the provision of suitable medium space for mechanical and electrical energy conversion. The commutating poles are able to decrease the magnetic flux density contrast with the generator without commutating poles according to analysis the curve of the gap magnetic field and the distribution of the inner magnetic field in them. The EMF drops by 42. 3% on the average due to the functions of commutating poles, and the spark experiment also shows the improved commutation. This design scheme facilitates commutation, and decreases the spark level and inhibits the electromagnetic interference to heighten the stability, reliability and security of generators.