Guardian 4721, Руководство по ремонту

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INTRODUCTION
This section covers the major components of the AC
generator proper, i.e., those generator assemblies
that provide for the production of AC electrical power.
The single bearing rotor (revolving field) is driven by a
1.5 liter, liquid cooled gas engine. The rotor is cou-
pled to the engine flywheel, by means of a flexible
coupling and a fan and ring gear assembly, so the
engine crankshaft and rotor operate at the same
speed.
Major components of the AC generator are shown in
Figure 1 on the next page. These components are (a)
a flexible coupling, (b) fan and ring gear, (c) rotor, (d)
blower housing, (e) stator assembly, (f) rear bearing
carrier, and (g) a rear bearing carrier cover.
BLOWER HOUSING
The blower housing is bolted to the engine and sup-
ports the engine end of the AC generator. It houses
the fan and ring gear assembly. A cutout area on one
side of the housing allows a blower air outlet screen
to be mounted.
FLEXIBLE DISK
A flexible disk bolts to the engine flywheel and to the
fan and ring gear assembly. The disk maintains prop-
er alignment between the engine and generator parts.
FAN AND RING GEAR ASSEMBLY
The fan and ring gear assembly are retained to the
flexible disk which, in turn, is retained to the engine
flywheel. The fan draws cooling air into the generator
interior through slots in a rear bearing carrier cover,
then expels the heated air outward through a screen
on the blower housing. The ring gear teeth mate with
teeth on a starter motor pinion gear, when the engine
is cranked.
ROTOR ASSEMBLY
The rotor assembly on units rated 1800 rpm is a 4-
pole type, having two north magnetic poles and two
south magnetic poles.
The rear end of the rotor is bolted and keyed to the
fan and ring gear. A ball bearing has been pressed
onto the rotor’s front shaft, which is retained, in a
machined bore in the rear bearing carrier.
A positive (+) and a negative (-) slip ring is provided
on the rotor shaft that retains the ball bearing.
Brushes will ride on these slip rings.
The combination of slip rings and brushes allow rotor
excitation current to be transmitted from stationary
components into the rotating rotor windings. The posi-
tive (+) slip ring is the one nearest the rotor bearing.
REAR BEARING CARRIER
The rear bearing carrier supports the front of the gen-
erator. Mounting feet at the carrier bottom permit the
carrier to be bolted to the generator’s mounting base.
A machined bore, in the center of the carrier, accepts
the rotor bearing. Bosses allow for the retention of
brush holders. Long stator bolts pass through holes in
the carrier’s outer periphery, to sandwich and retain
the stator can between the carrier and the blower
housing. A rear bearing carrier gasket helps prevent
dust from entering the bearing area.
STATOR ASSEMBLY
The stator can is sandwiched between the blower
housing and the rear bearing carrier, and retained in
that position by four (4) stator bolts.
A notched cutout has been provided in the rear bear-
ing carrier end of the stator can. A rubber grommet
has been placed into that notch, for protection of the
stator leads that are brought out of the stator.
REAR BEARING CARRIER PLATE
This plate is retained to the rear bearing carrier by
four (4) capscrews, lockwashers and flatwashers. The
plate provides slotted air inlet openings for the pas-
sage of cooling and ventilating air into the generator.
BRUSH HOLDERS AND BRUSHES
Brushes are retained in a brush holder which is
retained to drilled and threaded bosses on the rear
bearing carrier. In most cases, two brush holders are
used having two brushes per holder. Brush holders
are precisely positioned so that one of the two brush-
es slides on a positive (+) slip ring, the other on a
negative (-) slip ring. The positive (+) brush and slip
ring are nearest the rotor bearing. The positive (+)
side of the DC excitation circuit (Wire No. 4, red) con-
nects to the positive (+) brush; the negative (-) or
grounded side (Wire No. 0) to the negative (-) brush.
Brushes and brush holders are illustrated in Figure 2,
on Page 22.
PART 2
Page 20
PREPACKAGED LIQUID
COOLED AC GENERATORS
SECTION 2.1
DESCRIPTION AND MAJOR COMPONENTS