东风4型机车运行中由于发电机本身或其励磁系统故障而无励磁电流时，牵引发电机无电流电压输出（简称无压无流），造成机车无法牵引运行。仅1994年7月一1995年7月一年中，我段因此故障而造成的机破就有5件之多，给运输生产造成了严重的影响，也引起了我们的高度重视。从对这5件 When there is no excitation current in the operation of DF4 locomotive due to the generator itself or its excitation system failure, the traction generator has no current and voltage output (referred to as no-pressure and no-flow), which makes the locomotive unable to tow and run. In the period from July 1994 to July 1995 alone, there were as many as 5 mechanical breakdowns resulting from the failure of this section, which seriously affected transport production and attracted our great attention. From this 5 pieces