Hobart 120CU20, Operation And Maintenance Manual With Illustrated Parts List

Page: 125 / 246

OM-2228 / Operation and Maintenance Manual
120CU20 / Series 500120 / 400 Hz. Generator Set
October15, 2013
Chapter 3-1
Page 3
The exciter armature is mounted on the main generator armature shaft with a 3/8-inch square machine
key that is held in place by a key retainer, and an M12-1.75 hex head cap screw in the center of the diode
mounting plate.
3) Exciter Armature Replacement.
a) General.
Exciter armature removal is often required for rear bearing replacement rather than for replacement of
the exciter armature itself. Other reasons for exciter armature removal are generator armature
replacement, general overhaul, etc.
b) Tools needed for Exciter Armature Removal and Installation.
In addition to the standard mechanic’s hand tools such as wrenches, etc., you will need only the
following items for removing the exciter armature:
•
A small, lightweight, sling-hammer puller
•
Two M10-1.5 x 127 mm long fully-threaded hex-head bolts
A small, lightweight, sling-hammer puller is shown in Figure 3. This tool is necessary for removing
the threaded machine key, which keeps the exciter armature from spinning on the generator armature
shaft. You may have such a puller in your equipment inventory. If not, Figure 3 also illustrates
components and dimensions for fabricating such a tool. Sling-hammer pullers are also commercially
available. Instructions for using tool are provided in this manual.
Once the threaded machine key is removed, No other special tools are required for removing the
exciter from the generator shaft. This can be done using the two M10-1.5 fully-threaded hex-head
bolts. Instructions for doing this are provided in this manual( see section e).
c) Conditions for Exciter Removal.
The mechanics performing the work must decide upon the best and most convenient method of
removing the exciter armature. If the exciter armature is being replaced, then the work may be
performed without removing the generator from the machine. In a great majority of cases, exciter
removal will be for the replacement of the rear bearing. This operation can also be accomplished
without removing the generator. Replacement of the front bearing requires removal of the generator
from the unit.
d) Preparation for Exciter Armature Removal.
(1) Remove exciter cover from end canopy and the exciter armature cover from the end of the
generator.
(2) Place a block bar (pry bar) into the generator fan assembly to keep the generator armature from
rotating.
WARNING
To prevent personal injury, keep fingers and hands clear of generator assembly until
the armature is block into place to prevent rotation.
(3) Remove exciter housing cover as required. Remove the M12-1.75 cap screw, which holds the
exciter armature and key retainer on the generator shaft.