will bow the bar and leave the center arc-quencher
d. With breaker withdrawn and closing springs
restrained see that all nuts and bolts are in place and
tight. See that no pins or cotter pins have worked out of
g. Examine the contacts (it is necessary to remove
place and that all cotter pins have sufficient spread to
the arc quenchers to properly inspect contacts) they
hold them in place. All mechanism rods and moving
should be clean and bright, free from dust and dirt
parts should be free from binds and the mechanisms
Check the condition of the arcing
should be in good working order.
contacts which open after and close before the main
current-carrying contacts. If they are badly pitted or
e. Operate the breaker several times to check the
burned, it may be necessary to dress or to replace them.
proper functioning of all parts. In general circuit-
Laminated contacts so badly dam aged or burned and
breaker mechanisms require little lubrication. It is
pitted that satisfactory operation can not be obtained
recommended to use a few drops of good grade light
should be replaced.
machine oil at bearing points, and to wipe off any
excess oil with a clean rag. This should be done at
On feeder breakers (AK-2-50) the series
regular inspection intervals.
overcurrent tripping device EC-I is enclosed in a molded
case. It is mounted by three screws and a bracket to the
f. Inspect the arc quenchers, if the barriers are
lower part of the pole unit base.
cracked or eroded to one-half their original thickness
of 3/16 inch, they should be replaced. Removal or
(1) Check trip latch engagement. The gap
replacement of arc-quenchers procedure is:
between trip latch (5, fig. 3-12) and roller (6) of the
reset latch should be 1/64 to 1/32 inch. This adjustment
is made with adjusting screw (7).
Be sure the breaker is open and closing
(2) Turn the adjusting screw (1, fig 3-12) on the
springs are restrained.
trip arm (21. The screw should not touch the trip paddle
(3) when breaker is open and the latch is reset but
should have a clearance not exceeding 1 / 32 inch.
(1) Remove the channel-shaped retaining bar
(view B fig. 3-10) by removing two screws and two nuts,
one on each end.
Component parts of the overcurrent tripping
(2) Lift the quenchers clear of the movable
devices are not replaceable. Install a new
device when parts are worn or damaged. To
replace an EC-I overcurrent device the front
Replacement is the reverse of (1), (2)
During replacement be careful not to
and rear frames should be separated 'he
overtighten the screws which secure the channel-
breaker must be removed from the drawout
shaped retaining bar. Overtightening the screws
mechanism and put on a work bench
KEY to figure 3-12:
1. Trip paddle adjusting screw
2. Trip arm
3. Trip paddle
4. Trip shaft
5. Trip latch
6. Roller of reset latch
7 Adjusting screw