The stability of a generator depends on the field strength
of the magnetic field establishing in the air gap by the
rotor ampere turn. if the field is weakened the stability
margin is reduced.
Leading power factor causes field mmf (fm) to reduce and
rotor angle to increase towards 90 degree, the theoretical
operation of stable generation operation. Therefore a
machine operates well within its stability limit factor
with lagging power factor.
Transformer operation does not depend on power factor. For
that reason it is rated in KVA.
Leading power factor makes the current leading the voltage
it does not affect the transofmer but it affects the
D.G./Power generation unit. As for the power generation we
need to excite the excitor field which take the sensing
reference voltage from the output line of the generator.In
case of leading power factor the voltage will not dip on
increasing the load and hence the AVR will not be able to
excite the system properly.
The transformer opration does not depends on the pf. The
major problem in leading pf is related to generation.
Stator end region heating depends on the pf. In leading pf
the altenator run at underexited operation and there is the
scope for flux to increase even over the saturation limit
of core. That causes the core heating on end region.
Leading power factor does affect the power Xmer within its
VA rating but it affects the D.G./a Generator unit.Due to
leading power factor the source excitation system runs in
under excited state and the deficit in excitation has to be
supplied by stator.Owing to this stator end core heating