摘要
脉宽调制 (PWM )变频器输出的陡上升沿且高重复的脉冲电压在长电缆的末端发生波反射而产生近似 2倍的尖峰过电压 ,从而导致变频调速系统中电动机绝缘的过早损坏。采用RC一阶阻尼滤波器来抑制PWM变频调速电动机端子上的尖峰过电压 ,首先研究了在不同电缆长度 (30m和75m)下 ,滤波器的电阻和电容对电动机端电压特性的影响 ,得到了电缆长度、滤波器的电阻和电容与电动机端过电压幅值及脉冲电压上升沿时间的关系 ,结果表明滤波器的电阻值越小 ,电容值越大 ,则电动机端子上过电压幅值就越小 ,且脉冲电压上升沿时间也越大。为了减小滤波器的功耗 ,其电容值应选择小于 0 .1μF。当滤波器的电阻参数小于电缆波阻抗的 1.5倍 ,且电容参数选择在 0 .0 2～ 0 .1μF之间时 ,电动机端子上的过电压倍率则不超过 1.2。最后应用传输线理论及信号的卷积分对试验结果进行了分析 。
Under the fast front impulse voltage of inverter output and long cable, the high repeatable sharp overvoltage occurred at the end of cable due to wave reflection was about 2 times that of inverter output level, which resulted in the premature fail of motor insulation. The RC damping filter was used for suppressing/reducing the sharp overvoltage at the terminal of PWM inverter fed motor in this paper. Under the different cable length, 30m and 75m respectively, the influences of filter resistance and capacitance parameters on the voltage waveform of motor terminal were investigated firstly. The relationships of the cable length, filter resistance and filter capacitance with the magnitude of overvoltage and impulse voltage risetime at motor terminal were studied also. The researched results showed that the lower resistance and higher capacitance, the lower overvoltage magnitude and shorter voltage rise time. In order to reduce the power dissipation of filter to as lower as possible, the capacitance of filter should be lower than 0.1(F. When the resistance of filter is 1.5 times surge impedance of cable, and the capacitance of filter is from 0.02μF to 0.1μF, the rate of overvoltage at motor terminal will not exceed 1.2. Finally the experiment results were analyzed by using the transmission line theory and Duhamel integral. The theory analysis indicated that the wave front of overvoltage at motor terminal was composed of fast region and slow region.
出处
《中国电机工程学报》
EI
CSCD
北大核心
2001年第8期84-88,共5页
Proceedings of the CSEE
