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 TM 5-683/NAVFAC MO-116/AFJMAN 32-1083
proper gap, wipe and contact alignment. Contact
sign. That is, if the contact is a line type, keep the
gap is the distance between the stationary and mov-
area of contact linear, and if ball type, keep the ball
able contacts with the circuit breaker in the fully
shaped out. Discoloration of silver-plated surfaces is
open position. If the arcing contact gap is too small,
not usually harmful unless caused by insulating
a circuit breaker may not be able to interrupt a
deposits. These deposits should be removed with
fault. If the main contact gap is too small, the main
alcohol or a silver cleaner. Whether cleaned or not,
contacts will interrupt the fault along with the arc-
lubricate the main contacts by applying a thin film
ing contacts and possibly burn the main contacts.
of slow aging, heat resistant grease. All excess lubri-
Contact wipe is the amount of over travel between
cant should be removed with a clean cloth to avoid
the stationary and movable contacts from the time
accumulation of dirt and dust. Under no circum-
when the contacts are just touching to the time
stances should the arcing contacts be lubricated.
when the circuit breaker is fully closed (figs 24,
Where serious overheating is indicated by discolora-
25, and 26). Check that all contacts make and
tion of metal and surrounding insulation, the con-
tact and spring assemblies should be replaced in
break at approximately the same time. Make ad-
justments in accordance with the manufacturer's
accordance with manufacturer's instructions. While
recommendations. Laminated copper or brush style
carefully closing the circuit breaker, check for
I
CONTACT WIPE
Figure 2-4. Arcing contact gap and wipe.
2-7
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