Smooth cylindrical type or Non-Salient Pole Alternator Rotor is use for Steam driven alternator i.e. turbo alternator which Runs at very high speed. Since Steam turbine Run at very high speed, therefore, they Required less Number of Pole hence the diameter(D)of the Rotor can be small and axial or Rotor length (L) is large. [KυA∝D2L]