A.降低電源電壓B.電樞回路串電阻C.減小磁通D.改變轉(zhuǎn)差率
A.無(wú)級(jí)調(diào)速B.有級(jí)調(diào)速C.有極調(diào)速D.無(wú)極調(diào)速