YVF2 series three-phase frequency controlled asynchronous motor possesses a wide range of speed regulation. It can match with a variety of converters to comprise an A.C. stepless adjustable frequency driving system. At low speed (5-50Hz), this motor can run smoothly under constant torque oscillation, and has a larger starting torque and a smaller starting current, delivering constant output power at high speed (50-100Hz). Its mounting arrangements and dimensions are all according to standard three-phase asynchronous motor series. Built-in cooling fans ensure excellent cooling effects under different speeds.