A、<span style=";font-family:宋体;font-size:16px">提高灵敏度</span>
B、<span style=";font-family:宋体;font-size:16px">防止正向出口短路动作</span>
C、<span style=";font-family:宋体;font-size:16px">防止反向出口短路动作</span>
D、<span style=";font-family:宋体;font-size:16px">消除正向出口三相短路的死区</span>