变极多速三相异步电动机是三相异步电动机的主要派生系列之一。该电机可随时负载状态有级地改变转速，达到功率的合理匹配和简化变速系统。它广泛应用在机床、矿山、冶金、纺织、印染、化工、农机等部门。
YD系列电动机的功率等级与安装尺寸的对应关系与国外同类型先进产品相当，便于单机或机床配套出口，也可作为引进设备中同类型电机的备品电动机。
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.
