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MAIN CONTACT INSPECTION AND REPLACEMENT
All main contacts are made from a material specially
suited for making and breaking high electrical currents
while resisting welding and erosion due to arcing. The
contacts are brazed to a copper alloy base material which
serves to support them,
C8rr)'
electrical current and conduct
heat away. This base material is subject to erosion and
welding if exposed to arcing; therefore contacts must be
replaced when the contact material is worn nearly to the
point of exposing the base material. As a guide, the contacts
should be replaced when approximately
3/32
inch of contact
material has been eroded away.
CAUTION: Contacts must be replaced before any part of
one contact makes contact with the base material of its
mating contact.
The interval between inspections will vary with the na-
ture ofthe load being switched. It is recommended that the
contacts be inspected after the first 1,000 operations. If only
minor pitting is observed, then the inspection interval can
be increased. Evidence of heavy pitting and erosion of con-
tact material means the contacts should be checked more
frequently to detennine if the wear allowance
of3/32
inch is
being approached.
Refer to Figure 9
When contacts require replacement, replace contacts (3)
and (35) and springs (32) on all three phases at the same
time. To gain access to all contacts, remove two phase
barriers and all three arc chutes (14). Then swing back
hinged blowout coil assemblies. All main contacts are now
accessible for replacement.
Remove hex lock nuts (80) allowing cap screws (74) to slip
out of pushrod (28) Movable contact (35) is now accessible
for replacement.
First remove movable contact assembly. Remove hex
head nut with lockwasher (85) (84). Stationary contact (3)
may now
be
removed for replacement.
MAGNET COIL REPLACEMENT
Refer to Figure 9
Remove wire oonnections from coil. Loosen hex head
machine screw (89). Slide magnet assembly from the base
of the yoke (16). Machine screw (89) along with magnet core
(17) can then be lifted from coil along with washers (18) (19)
(20) (21) (94). Replace coil and reassemble following the
reverse procedure.
AUXILIARY CONTACT ADJUSTMENT
Refer to Figure 9
Tighten auxiliary drive link (39) to coupling angle (46)
just enough to remove excessive free play. Do not over-
tighten.
ARC CHUTE INSPECTION AND MAINTENANCE
The arc chutes should be inspected as part of routine
maintenance each time the contacts are inspected. In ser-
vice, the arc chute ceramic will become discolored slightly
due to nonnal arcing as the contactor operates. Dust and
dirt will also tend to accumulate after a period of time. The
following procedure should be used to clean the arc chutes
after they have been removed from the contactor:
1. Blowout dust and dirt by directing dry compressed air
from the bottom of the arc chute up through the spaces
between the ceramic arc splitters. The air should also be
directed over the surfaces of the ceramic flash plates
located in
th~
lower ponion of the chute <refer to Figure
5).
•
2.' Using a cloth or by light sanding, remove any additional
loose residue (carbon, etc.) from the flash plates.
Pay
particular attention to the areas which have vertical
grooves on the ceramic surface. Do not use abrasives
which might embed conducting particles in the ceramic
(emery cloth. wire brush. etc.).
CERAMIC ARC
SPLITTERS
CERAMIC
FLASH PLATES
)
Fig. 5
In addition to periodic cleaning, the arc chutes should be
inspected for any obvious physical damage such as cracked
or missing ceramic pieces. Small chips or slight cracks in
the ceramic should not cause concern as long as no large
pieces are missing or are in danger of falling out of the
assembly. If any components require replacement, the
complete arc chute assembly must be replaced.
CAUTION: When replacing arc chutes, refer to important
ordering information at the end of this manual.
After prolonged periods of operation at medium-ta-heavy
currents or after the contactor has been required to inter-
rupt at or near its full 50MV A rating, heavy electrically
conductive deposits may accumulate on the flash plates
which would interfere with proper contactor operation. In
the event of this, it is recommended that a dielectric or
Megger test be perfonned as follows to verify dielectric
strength of the flash plate sufaces. If a Megger is used, the
recommended test voltage is 1000 volts.
WARNING: Dielectric test voltages are hazardous. Refer
to test device instructions for safety precautions.
1.
Clip Megger or dielectric tester leads onto the flash
plates at the points shown in Figure 6 using alligator
clips or the equivalent.
2. The area between the clips should withstand 9KV
AC(13KV DC) for one minute or should indicate a resis-
tance of at least 100 Megohms. Be sure to test both left
and right sides of the arc chute. If either side fails to
meet the dielectric requirement. then disassembly and
cleaning is necessary before placing the arc chute back
into service. If one arc chute fails the test, then disas-
sembly and cleaning of all three arc chutes is
recom~
mended.
PERIODIC CLEANING
Accumulation of dust and foreign material such as coal
dust, cement dust or lamp black must be blown ofT the
contactor, all surfaces must be wiped clean at regular in-
tervals. Dust can collect moisture, causing voltage break-
down.
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