单项选择题
A.闸瓦紧抱车轮而缓解B.闸瓦离开车轮而缓解C.闸瓦离开车轮而制动D.闸瓦紧抱车轮而制动
A.380VDC/1minB.500VDC/1minC.1500VDC/1minD.2500VDC/1min
A.110VB.220VC.500VD.1000V