A.2.5MΩ B.500MΩ C.100MΩ D.1000MΩ
A.5~10s B.0~10s C.30s D.10~20s
A.下軸承的質(zhì)量 B.永久磁鐵的壽命 C.電磁元件的變化 D.驅(qū)動元件的質(zhì)量