Answer / sachin_pawaskar2001

loss of excitation

Answer / nimish

there are so many reasons there may not be a residual
magnetism in d.c. generator then if critical resistance is
more than field resistance

Answer / j.kesavan

some times diodes failur in exciters,thats why voltage not
built in gen set

Answer / swayanjit

if voltage build up is not possible then there may be open
circuit in the field or armature, may be due to dirty
commutator, may be the speed less than the critical spped,
may be the field resistance greater than the critical
resistance.

Answer / shakir

there are so many reasons:
1.the exciter might have problem
2.the ac produced in exciter is converted into dc before
supplying it to the rotor.the diodes used for this purpose
might have problem.
3.when u start the generator there should be a residual
magnetism to induse the voltage.if u will not use the
generator for long time, it will loose that residual
magnetism.for that purpose u have to give flash over
voltage.
4. the exciter winding might be grounded.
5. the input (D.C.from voltage regulator)voltage to the
exciter is not enough to create flux in the exciter.
6.faulty stator winding

Answer / har

avr damaged

Answer / sirisha

it is because the polarities of the field windings are
reversed.

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