基于PWM逆变器供电轴电流问题的交流电机耦合电容的计算与测量

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摘要 PWM 变频供电驱动系统中在交流电机定、转子寄生电容耦合作用下轴上感应电压,继而产生轴电流,可使轴承失效。电机内部耦合电容参数的准确计算和测量对预测轴电压和轴电流有重要作用。本文根据电机几何尺寸,给出了耦合电容的解析计算公式,分析了电机容量对耦合电容和轴电压分压比的影响。采用有限元法对异步电机进行多导体系统耦合电容分析计算,提出了定子绕组电磁散线建模方法,大大减小了定子绕组和定子机壳之间电容C_wf的计算误差；三维有限元计算结果表明绕组端部对定子绕组与转子之间电容C_wr有较大影响。最后介绍了一种适用于中小容量电机的耦合电容测量方法。

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	刘瑞芳
	陈嘉垚
	马喜平
	程建全
	曹君慈

关键词 ：交流电动机, 轴电流, 共模模型, 耦合电容

Abstract：Through parasite capacitive coupling between the stator and rotor, damaging voltages are induced on the shafts of AC motors controlled by PWM variable frequency drives. Harmful bearing current will be produced and eventually cause bearing failure. The coupling capacitances of AC motors are key parameters in predicting shaft voltage and bearing current. The modeling and calculation of motor capacitance are investigated in this paper. Based on the structure of motors, the analytic calculation of capacitance is carried out. The influence of the motor capacity and size on the capacitance and bearing voltage ratio is analyzed. Finite element method is adopted to analyze the capacitances. A scattered motor winding model is proposed to acquire rational capacitance C_wf. 3D finite element analysis shows that the end of winding is an important factor should be considered in calculating capacitance C_wr. Finally a new measurement method of motor capacitance for small and medium motor is introduced.

Key words： AC motor bearing currents common-mode model coupling capacitance

收稿日期: 2013-01-18 出版日期: 2014-06-16

PACS:

TM34

基金资助:国家自然科学基金（51107004）,台达环境与教育基金会《电力电子科教发展计划》（DREG2012010）和铁道部科技研究开发计划重点（2012J005-F）资助项目

作者简介: 刘瑞芳女,1971年生,博士,副教授,研究方向为电磁场理论与数值计算。陈嘉垚男,1990年生,硕士研究生,研究方向为电磁场理论与数值计算。

引用本文:

刘瑞芳, 陈嘉垚, 马喜平, 程建全, 曹君慈. 基于PWM逆变器供电轴电流问题的交流电机耦合电容的计算与测量[J]. 电工技术学报, 2014, 29(1): 60-67. Liu Ruifang, Chen Jiayao, Ma Xiping, Cheng Jianquan, Cao Junci. Calculation and Measurement of Coupling Capacitances in AC Motors Based on Bearing Currents Problem Induced by PWM Inverters. Transactions of China Electrotechnical Society, 2014, 29(1): 60-67.

链接本文:

http://dgjsxb.ces-transaction.com/CN/Y2014/V29/I1/60

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