Synchronous Machines
  • Armature winding of synchronous machine either delivers 3 phase a.c source or its supplied by 3 phase a.c source and the field winding is energized from dc source.
  • As in other rotating machine the emf induced in synchronous machine is motional emf so there must be relative motion between the conductors and magnetic field.
  • Emf is induced in armature conductors but they are kept on stator so they cannot rotate and hence in order to have relative motion between magnetic field and conductor the magnetic field must rotate.

What are the advantages of having armature winding on stator?

  • More Economical
  • More efficiency :- By the use of two slip rings instead of three slip rings we can minimize the losses and hence we can improve efficiency.
  • Better Insulation :- High Voltage winding should be stationary in order to provide effective insulation.
  • Efficient cooling :- Stationary armature winding can be cooled more efficiently.
  • More Output :- By keeping low power field on rotor the weight of field winding is reduced and hence it can rotate at higher speed.
  • Convenient Construction :- The winding can be braced in a better way against electromagnetic force if it is accommodated in stator slots. Because of all these reasons DC generators cannot handle as much power as an ac generator.

Concept of Synchronous Speed

Synchronous speed is basically the conversion of electrical frequency “f” in mechanical speed in terms of rpm.

What is the difference between Synchronous generator and asynchronous generator?

Synchronous Generator

Asynchronous generator

(Induction generator)

  • Rotor rotates at synchronous speed.
  • Used in Conventional Energy Sources (Eg:-Thermal power plant, Nuclear Power plant, Hydro power plant).
  • 2/3rd of the power generation is derived from steam power plant.

Rotor rotates at speed higher then synchronous speed.

Used in non conventional energy sources (Eg:- Wind, Tidal)

 Non conventional (Speed not constant)



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