適用于：要求隨負載的性質逐級調速的各種傳動機械如機床、礦山、冶金、紡織、印染、化工等行業。
特點：采用改變繞組的接法來變換電機的轉速和輸出功率，使其與機械設備的負載特性相匹配,簡化了變速系統，高效、節能。
變速方案：雙速、三速、四速

Applications: widely used in such industry which have step changes of rotational speed to meet the requirements of load character, as m-achine tools, mining, metallurgy, textile, printing and dyeing, chemical industry and agricultural machinery, etc.

Features: simplify speed-changing systems by changing the connection to obtain diferent output and speed.Pole-changing mode: double, three or four speed.