A. He is told that it is a good zipper. B. He is told that it is a good sipper.
A. 弱磁升速 B. 电枢回路串电阻调速 C. 降压调速 D. 改变定子磁极对数
A. 主磁通较弱 B. 反电动势为零 C. 瞬间高压 D. 提高电磁转矩