變極多速三相異步電動機是三相異步電動機的主要派生系列之一。該電機可隨時負載狀態有級地改變轉速，達到功率的合理匹配和簡化變速系統。它廣泛應用在機床、礦山、冶金、紡織、印染、化工、農機等部門。
YD系列電動機的功率等級與安裝尺寸的對應關系與國外同類型先進產品相當，便于單機或機床配套出口，也可作為引進設備中同類型電機的備品電動機。
YD series varible pole multi-speed three-phase asynchronous motore are one of the main serise products deriving from three-phase serise.This kind of motor can change rotational speed to meet the requirements of load state,so that they can properly match the demands of power and simplity adjustable speed system. they are widely used in such industrial and agricultural departments,as machine tools,mining metallurgy,spinning and weaving,printing and dyeing,chemical industry and agricultural machinery,etc.
For similar correspondent relationship between power rank and insullation dimensions,YD serise motors are equivalent to other foreign advanced machines, and therefore they are matchig with single-machine or machine tool for export as well as spare motors for similar types imported from abroad.