DESCRIPTION
GENERAL
An
Onan
~IB
Series electric generating set consists.of
a two-cylinder, in-line gas
or
gasoline engine and a
7.5
KW(6.0
KW
for
50
Hertz) alternating current
generator with standard
or
optional equipment
as
ordered.
ENGINE
The JB engine has 60 cubic,inch (983.4 cm
3
)
piston
displacement, 6.5:1 (9.2:1
for
gas) compression ratio,
and is air-cooled. Basic measurements and other.
details are listed under SPEC/FICA TlONS.
AC GENERATOR
The
YO
generators beginning with Spec
AA(Figure
1)
are four-pole, revolving field, brushless exciter
models
of
drip-proof
construction. Generatordesign
includes both single and three-phase, 60 and
50
hertz
type generators. The generator rotor connects d irect-
Iy to the engine crankshaft with a tapered shaft and
key. The generator
is
fastened to the engine by the
rotor-through,;,stud which passes through the rotor
shaft; it has a nut on the outside
of
the end bell: A
centrifugal
blowerjon
the front end
of
the
rotor
shaft,
circulates
the
generator cooling air which is drawn in
through the end bell cover, over the rotor, and
discharged through an outlet at the blower end.
A ball bearing in the end bell supports the outer end
of
the rotor shaft. The end bell and generator stator
housing, are attached byfour-through":studs which
'pass
through the stator assembly to the engine-
generator adapter. The brush less exciter stator
mounts in the end bell while the excher rotor and its
rotating rectifier assemblies mount on the generator
rotor shaft.
The basic operation
of
the generator and voltage
regulator involves the stator, voltage regulator, ex-
citer field and armature, a full wave bridge rectifier,
and the generator rotor. Residual magnetism in the
generator r.otor and a permanent magnet embedded
in one exciter field pole begin the voltage build-up
process
as
the generator set starts running. Single-
phase AC voltage, taken from one
of
the stator
OVERALL
LENGTH
BLOWER
TORQUE
TO
130-150
FT.
LBS.
(176-203
N.
~)
TORQUE
TO
55-60
FT.
LBS
•.
(75-8
I
Ne
m)
IIIH!..---;.--
ROTOR-
THROUGH-STUD
.
O-RING
,
SEAL
ENGINE-
GENERATOR
ADAPTER.
ROTATING
RECTIFIER
ASSEMBLIES
ER
(HOUSED)
I$;~;;;;;;;;~~-;;;;Jf--
COVE
R
LESS
R
STATOR
ROTOR
TO
35-38
FT.
LBS.
(47-52
N.
m)
FIGURE 1
•.
GENERATOR (CUTAWAY VIEW)
:',
-.-~.
4
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