synchronous machine can be characterized by the type of rotor used. Rotors used in Synchronous alternators can be classified into:
1)Salient and
2)Non-Salient Pole Rotors or cylindrical rotors
Salient pole rotors are used in application with speeds from 100 to 1500rpm. They are alternative known as "projected
pole" type of rotors. The poles mounted on the rotor are made of
lamination's made of steel. The poles are connected to the rotor shaft
by means of dovetail joints. Each pole has a pole shoe around which
the winding is wound. The salient pole rotor is generally used in
applications where the prime mover
is a hydel turbine or a combustion engine which have low or medium
speeds. Salient pole rotors usually contain damper windings to prevent
rotor oscillations during operation. Due to low speed, they are
constructed with higher no. of pole (ranging from 8-24 or higher) to
achieve system frequency so they can be said as higher pole machine.
Almost all hydro power uses salient pole rotor synchronous generator.
Non-salient pole rotors are generally used in application which operate at higher speeds, 1500rpm and above. The prime movers
in these applications are generally gas or steam turbines. These are
sometimes known as "drum rotors". The rotor is a cylinder made of
solid forged steel. The slots
on which the windings are fixed are milled on the rotor. The number of
poles is usually 2 or 4 in number. Since these rotors are
cylindrical, the windage loss is reduced. The noise produced is also
less. These rotors have higher axial length. These rotors do not need
damper windings. Due to high speed, they are used with gas turbine and
high speed steam turbine in nuclear power plant and thermal power plant.
No comments:
Post a Comment