A.一塊電流表接于a相 B.一塊電流表接于c相 C.三塊電流表接于a、c、n三相 D.一塊電流表接于b相
A.15~25s B.15~30s C.10~25s D.10~30s
A.500 B.1000 C.2500 D.任意等級