Losses In Synchronous Generator

Losses In synchronous generator and its efficiency.

 The Losses in generator  are:-

Electrical losses:-

That is include field loss , armature winding loss and brush contact loss. The copper loss of the field     rheostat or, more simply, by multiplying the excitation voltage by the field winding and the electrical loss of the field rheostat or, more simply, by multiplying the excitation voltage by the field current. This loss is constant for any given voltage and power and factor, but varies with these two, the maintenance of rated voltage at low lagging power factor needs comparatively large field current and gives the maximum field loss.

The armature copper losses in the stater winding are determined on the basis of the armature resistance. Whether the ohmic or effective resistance should be used , depends upon the treatment of the stray load losses

                                                                                                         

Core losses:-

It is due to eddy current and hysteresis cause by the flux resulting from the combined rotor and stator fields such losses occur in poles faces and armature teeth and core. This loss is assumed to be independent of load.

It is equal to the difference of power required to drive the alternator with and without the field excited.

 Friction and winding loses:-

Its includes ventilation loss (ventilation lose is required to circulated the cooling air)

and due to bearing and brush friction.

Since the speed is constant of generator, so the loss for a particular machine remains constant.

 It’s equal to the mechanical power required to drive the alternator at rated speed with no excitation.

 Load Or Stay power losses::-

It is due to armature leakage flux which cause eddy current and hysteresis in the iron surrounding the armature c conductors in addition to the additional core losses caused by distortion of the magnetic field under load condition.

PERCENTAGE EFFICIENCY = [ 1-   Kw losses/kva output*pf*kw losses]*100

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