An economical drive for multi-speed applications.
  Power savings at reduced loads.

Electricly speed changing. Efficiency up 20% in typical application.
Lower initial investment costs. Lighter, smaller and more efficient
  than a two-winding motor.
Inrush currents during starting are greatly reduced when
  low-speed starting is used.
Low speed to start high inertia loads reduces rotor heating up to
  40% and contributes to extended motor life.
Reduced wear and erosion on the driven equipment (and less noise)
  during operation at low speed.

Speeds such as 720/600, 900/720, 900/600, 600/514, 900/514, 277/180, 450/360,1200/900 or 1800/1200 rpm, to name a few of the many possible combinations.