Brochure

5
Brushless exciter complete with rectier hub
Excitation
Brushless Excitation
System
The exciter is a three-phase AC
generator with a rotating three-
phase bridge rectier.
The exciter stator core is made
of laminated, hot rolled or cold
rolled steel, held together by steel
endplates.
The DC eld coils are wound in a
concentric pattern using formers
and mounted on the frame poles.
The whole assembly undergoes a
varnish treatment.The exciter rotor
armature consists of a three-phase
winding system. The core consists
of steel laminations that are stacked
and held with end plates and wound
with enamel covered round copper
wire. The whole assembly then
undergoes a varnish treatment.
The rectier hub includes liberally
rated diodes. The leads from the
armature are connected directly
to the hub, and the two DC output
leads from the hub are connected
to the main eld and clamped to
prevent movement.
The exciter armature and rectier hub
are assembled by interference onto
the shaft. The complete exciter and
rectier hub assembly is enclosed
in a steel sheet cover. For ease of
maintenance, a removable plate
gives access to the rectier hub.
As a protection for the diode bridge
under normal conditions, a varistor
is supplied in parallel with the
rectier hub.
Collector Ring with
Brushes
The brushes are electrographite
type, open terminal. The quantity of
brushes is determined taking into
account the current density required
for an ecient working of the
excitation system. The brush holders
are selected in order to provide the
required contact pressure between
the brushes and the collector rings.
The collector rings are low carbon
steel material, providing thermal
conductivity required to keep the
system at the temperature level
according to applicable standards.
There are two kinds of collector
rings: smooth (standard) and
grooved rings (for special cases).