Onan MJA Series Service Manual page 95

93 4. REVOLVING FIELD GENERATOR
MODELS 705MJB AND MJC
These generating plants use a 4-pole revolving field generator with static
exciter (Magneciter) to excite the field and regulate the plant's ac out ­
put.
The generator is mounted to the engine crankcase through the engine ­
to generator adapter. The rotor is directly connected - a tapered fit
with key - to the engine crankshaft.
A ball bearing, housed in the genera ­
tor endbell, supports the outboard
(collector ring) end of the rotor.
.~
The endbell is in turn, supported
by studs through the stator assembly
to the adapter. Because of its con ­
struction, the generator can't be re­
moved from the engine as a complete
unit.
The generator's ac output is drawn
from the stator windings which also
supply 120 volts to the static exciter.
AC
~STATOR 1<::::::::::
OUTPUT
~
,
"­
...... _ _ RESIDUAL MAGNETISM
IN ROTOR STARTS
PROCESS Y
I .... ,.. ......................
This 120 volts is from either a 120 ALTERNATOR AND EXCITER
volt winding or a special 120 volt tap on high voltage generators i. e.
480 volt.
An
additional stator winding supplies power for the plant's
battery charging system.
KEYS
'!...
BEARING
HOUSING
STATOR
WINDINGS
MAGNECITER
~~
_ ASSEMBLY
~\?'::jC···::L.::"'"
MAGNEC,.,.r-ol
COVER
COLLECTOR RI NGS
FIG 4.B - REVOLVING FIELD GENERATOR CROSS SECTION
i