一、前言大中型发电机组的灭磁及转子过电压保护问题,一直是围绕着解决提高灭磁速度与避免灭磁过程中转子回路过电压的矛盾进行。理想的灭磁过程是:灭磁开始至结束,,转子绕组端电压始终持一恒定数值,其值低于转子回路绝缘允许值,又可获得令人满意的灭磁速度。目前国内几乎所有大中型水电站发电机组灭磁系统, I. Introduction Large and medium-sized generator demagnetization and rotor over-voltage protection, has been around the solution to improve the speed of de-excitation and avoid demagnetization rotor circuit over-voltage conflict. The ideal demagnetization process is: from the beginning to the end of demagnetization, the voltage of the rotor winding always maintains a constant value, which is lower than the allowable value of the insulation of the rotor circuit, and a satisfactory demagnetization speed can be obtained. At present, almost all large and medium hydropower station generator demagnetization system,