Difference between salient pole & cylindrical pole rotors:
We can define a synchronous generator or alternator as a machine which converts mechanical energy into alternating type electrical energy. It consists of a stator and a rotor. Stator consists of stationary armature windings and rotor consists of fielding winding. The rotor is two types
1.Salient Pole type
2.Cylindrical pole type
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Depending on the type of rotor Synchronous Generator[Alternator] has been classified into two types:
1.Salient Pole Alternator:
- Poles are projecting out from the surface.
- The air gap is non-uniform.
- Diameter is high and the axial length is small.
- Mechanically weak.
- Preffered for low-speed alternators.
- Prime mover used are water, I.C. engines.
- For the same size, the rating is smaller than the cylindrical type.
- This rotor is also called as Projected pole type.
- This is preferred for low-speed alternators ranging from 125 r.p.m to 500 RPM
- Separate damper winding is provided.
2.Cylindrical Pole Alternator:
- Unslotted portion of the cylinder acts as poles hence poles are non-projecting.
- The air gap is uniform due to the smooth cylindrical periphery.
- Small diameter and the large axial length is the feature.
- Mechanically strong.
- Preferred for high-speed alternators
- Prime movers used are steam turbines, electric motors.
- For the same size, the rating is higher than Salient pole type.
- This rotor is also called as non-salient or non-projected pole type.
- This is preferred for high-speed alternators ranging from 1500 r.p. m to 3000 RPM.
- Separate damper winding is not provided.