Answer / solanki

STATOR-
stator is the main construction part of ac & dc
machine.normally it consist of field winding and this part
is stationary but if talk abt generator then some times
stator consist of armature winding...
rotor-
as its name suggest it is the rotating part of ac machine
.it made up of silicon steel & consist of armature winding.
exciter-
Generators require direct current to energize its magnetic
field. The DC field current is obtained from a separate
source called an exciter. Either rotating or static-type
exciters are used for AC power generation systems. There are
two types of rotating exciters: brush and brushless. The
primary difference between brush and brushless exciters is
the method used to transfer the DC excditing current to the
generator fields. Static excitation for the generator fields
is provided in several forms including field-flash voltage
from storage batteries and voltage from a system of
solid-state components. DC generators are either separately
excited or self-excited.

Excitation systems in current use include direct-connected
or gear-connected shaft-driven DC generators, belt-driven or
separate prime mover or motor-driven DC generators, and DC
supplied through static rectifiers.

The brush-type exciter can be mounted on the same shaft as
the AC generator armature or can be housed separately from,
but adjacent to, the generator. When it is housed
separately, the exciter is rotated by the AC generator
through a drive belt.

The distinguishing feature of the brush-type generator is
that stationary brushes are used to transfer the DC exciting
current to the rotating generator field. Current transfer is
made via rotating slip rings (collector rings) that are in
contact with the brushes.

Each collector ring is a hardened-steel forging that is
mounted on the exciter shaft. Two collector rings are used
on each exciter, each ring is fully insulated from the shaft
and each other. The inner ring is usually wired for negative
polarity, the outer ring for positive polarity.

A rotating-rectifier exciter is one example of brushless
field excitation. In rotating-rectifier exciters, the
brushes and slip rings are replaced by a rotating,
solid-state rectifier assembly. The exciter armature,
generator rotating assembly, and rectifier assembly are
mounted on a common shaft. The rectifier assembly rotates
with, but is insulated from, the generator shaft as well as
from each winding.

Static exciters contain no moving parts. A portion of the AC
from each phase of generator output is fed back to the field
windings, as DC excitations, through a system of
transformers, rectifiers, and reactors. An external source
of DC is necessary for initial excitation of the field
windings. On engine driven generators, the initial
excitation may be obtained from the storage batteries used
to start the engine or from control voltage at the switchgear.



rotating rectifier-
commutator of a dc machine is known as rotating rectifier
switch. which reverse the connection of external load ckt as
each reversal of current in armature.

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