Turbo alternator

Turbo alternator

  • The alternator which coupled directly to the steam turbines are called turbo-alternator .
  • The turbine converts heat energy in the steam into mechanical work and the alternator converts mechanical energy into electrical energy .
  • The bulk power is generated by three phase turbo alternators at frequency 50 Hz.
  • Turbo alternators are cylindrical pole machines having synchronous speeds 3000 rpm (tow pole machines) or 1500 rpm (for four pole machines ).
  • Large centrifugal force produced at these speeds, restrict the diameter of the turbo alternators and are
  • characterized by small diameters compared to their length.
  • The generated voltage is either 6.6kV or kV.
  • A separated DC generator¬† is mounted on the same shaft of the turbine and alternator and supplies the exciting current for the field winding of alternator .
  • Air cooling is used upto a capacity of 100MW generating units .
  • Hydrogen cooling can be used for 500MW generating sets.

Following are the special features of a turbo alternators used in thermal power station :

  • The turbo alternator have high rated speed.
  • The capacity of turbo alternators is upto 500MW.
  • Small turbo-alternators may be air cooled, but for large size units hydrogen cooling is used.
  • The turbo alternators have horizontal configuration.
  • The rotor of turbo-alternators are of small diameter as compared to its length.
Turbo alternator

Turbo alternator

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