43
(b) Periodical inspection items
The periodical inspection should be carried out for the items given in Table 32.
Table 32. Periodical inspection items
Periodical inspection item Contents of inspection
1. Tightening of screws ･ Check the terminal clamping screw and conductor
connecting screw for loosening, and tighten them
further. Also check the terminals to which no wire
is connected; unless checked, there is a possibility
that they will fall out and cause troubles.
2. Removal of dropped foreign
substances, such as dust, chip,
wiring waste, screw washer,
etc.
･ Confirm that there are no conductive foreign
substances in the molded part between the ter-
minals or in other places.
･ Check for adherence of dust, oil, etc. If such
foreign matters are found, investigate the cause
of their presence.
･ Check whether the window of the arc suppressing
chamber of contactor is blocked by a foreign
substance .
3. Check of abnormal temperature
rise
･ Check whether there is discoloration of the con-
ductive part due to abnormal temperature rise,
or discoloration and crack of the molded part due
to overheating.
4. Check of thermal overload relay ･ Check the terminal screws for loosening.
･ Check the operating state by performing test
trip and resetting.
･ When the contact of the contactor is almost
melted due to short circuit, the thermal overload
relay must be considerably damaged, so that it
should be replaced. (Excluding those which are
protected by CT or saturation reactor.)
5. Check of manual operation, and
check of operational sound or
beat at time of automatic
operation
･ Turn off the power and move the moving part
by hand. Check whether the moving part moves
smoothly .
･ Check whether abnormal operational sound or
beat are generated by automatic operation. If the
operation is done by opening the insulated
cover, troubles such as short circuit, etc. may
occur, so absolutely avoid initiating the above
operation .
6. Check of contact and time of
replacement
･ Check whether the contact is abnormally worn.
When the contact is remarkably worn, replace the
contacts of all phases even if the contact of only
one phase is worn. If only the contact of one phase
is replaced, a failure will occur because the thick-
ness of the contact of one phase is difference from
that of the other phase.
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