YD series variable-pole multi-speed three phase induction motor is one of the main derived series of Y series three phase induction motor, a national unified designed latest product in China and a replacement type for the JDO2 series. The speed of this series motor can be changed step by step according to the requirements of load characteristics, thereby reaching the aims of economizing on electricity and simplifying the system of speed variation. This series of motor has great starting torque and low noise and vibration, and its mounting dimensions are complied with the standard of IEC. It has a fairly good interchangeability as compared with the similar products of the same kind, so that it is easy to maintain and widely used in the industrial departments of machine tools, chemical industry, textile, metallurgy and mine, etc.