Constructional Details of Salient Pole Alternator

     TYPES OF ROTORS:


The two types of rotors are used in alternators.

•  Salient pole type

•  Smooth cylindrical type.

SALIENT POLE TYPE:

  Digital-computer program for design-analysis of salient, wound pole alternators (NASA technical note)

• It is used in low and medium speed alternators.

•    It has a large number of projecting poles having their cores bolted or dovetailed onto a heavy magnetic wheel of cast iron (or) steel of good magnetic quality.

•     It has large diameters and short axial lengths.  

                  Ex: water turbine (or) Diesel engine.

•  The poles and pole –shoes are laminated to minimize heating due to currents.

•    In large machines, field windings consist of rectangular copper strip wound on edge.

•    They are built with vertical shaft.

•    The stator slots on pole shoes are skewed to reduce tooth ripples. the ventilation is increased by providing fan blades.

   

    

SMOOTH CYLINDRICAL TYPE:

•     It is used for steam turbine-driven alternators which run at very high speeds.

•     Hence turbo –generators are characteristics by small diameters and very long length.

•     The cylindrical construction of the rotor gives better balance and quiter operation and also less   windage losses.

DIFFERENCE BETWEEN SALIENT AND CYLINDRICAL TYPE OF ROTOR