大功率直线感应电动机推力脉动研究

摘要

直线电机边端效应是由定子铁心、次级开断所致的固有效应,该效应会引起电机电磁推力的不同频率的脉动。本文首先基于电磁推力公式对边端效应所致的推力脉动频率进行了理论分析。然后利用一维磁路法对动态纵向边端效应引起的次级感应涡流沿轴向的分布规律进行了理论分析和解析计算,根据次级感应涡流进而计算得到了动态纵向边端效应引起的转差频率两倍频推力脉动幅值的解析表达式,并得到了推力脉动幅值和不考虑边端效应时的电磁推力值的比例关系,最后通过峰值功率20 MW,最大出力900 kN的大功率直线感应电动机实验系统对分析结论进行了试验验证。理论分析和试验结果表明：计及边端效应时直线电机电磁推力存在供电频率两倍频和转差频率两倍频的脉动,其中转差频率两倍频的脉动由动态纵向边端效应导致,主要和次级极数以及转差频率有关。%End effect, which results in the thrust ripple of different frequencies, is the inherent character-istic of linear induction motor ( LIM) . A study of thrust ripple on LIM was conducted. First, thrust ripple frequencies was obtained according to electromagnetic thrust calculation formula. Secondly, theory analy-sis and analytic calculation for distribution of inductive eddy current on secondary with a view to dynamic longitudinal end effect was presented based on magnetic circuit. Then, according to inductive eddy cur-rent on secondary, the expression of thrust ripple value at the frequency of twice of the slip frequency was obtained. Lastly, theory analysis and calculation results were validated by test data from the long primary DLIM system capable of producing 900kN of force, operating at the 20MW peak power level. The result indicates that there exists thrust ripple at twice the slip frequency and work frequency. Thrust ripple scale of twice the slip frequency, which results from dynamic longitudinal end effect, is related to slip frequen-cy and secondary poles.