A.90° B.120° C.180° D.360°
A.恒定磁場(chǎng) B.脈動(dòng)磁場(chǎng) C.合成磁場(chǎng)為零 D.旋轉(zhuǎn)磁場(chǎng)
A.試驗(yàn)電壓持續(xù)時(shí)間過(guò)短 B.試驗(yàn)電壓偏低 C.絕緣老化 D.變壓器分接開關(guān)未置于額定分接頭