44
Periodical inspection item Contents of inspection
･ When the contact is blackened:
Even if somewhat blackened, no trouble occurs;
however, if the blackening is abnormal, there may
be a problem about the atmosphere, so that
investigation and countermeasures should be
carried out.
･ Foreign matters adhered to the contact, such
as dust, etc. should be wiped off with a cloth
dipped in alcohol. Use of an organic solvent such
as trichloroethylene may cause contact failure.
･ Check contact over travel. When over travel is
little, replace the contacts.
7. Check of contacting face of
electromagnet (When there is an
abnormality referring to para. 5.)
･ Check when there is an abnormality such as
beat, etc.
･ Check whether a foreign substance such as dust,
etc. is adhered to the contacting face. When a
foreign substance is adhered to the face, wipe
it off with a cloth.
･ Check whether there is any rust. If it is found,
remove it by rubbing with dry cloth. Use of
sandpaper or file will result in producing beats.
8. Check of voltage applied to coil ･ Check whether the voltage is too high or too low.
The voltage should be adjusted so that it attains
the rated voltage after operation. Take care that
the voltage when closing does not become less
than 85% of the rated voltage. Unsuitable voltage
of the operating coil will cause various troubles,
so that special care should be taken to ensure
suitable voltage .
9. Measurement of insulation
resistance
･ Measure insulation resistance with the 500V
insulation resistance meter, and if its measured
value is less than 1MΩ, immediately replace
with new one. If the insulation resistance is less
than 5MΩ but more than 1MΩ, it can be
temporarily used; however, replace as soon as
possible.
6-2-2 Replacement of Contacts of Contactor
The electrical endurance of the contactor depends mainly upon the wear of the contacts and deteriorated insulation
of arc suppressing chamber. Contacts wear is classified into the modes given in Table 33, according to which the
conditions requiring contacts replacement are determined.
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