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When it is necessary to replace the contact of one of three phases, the contacts of all phases should be replaced
at the same time. Note that after replacement of contacts, the following items should be executed to check the
products.
(1) Measure the insulation resistance between phases, and between the terminals of power source and load to confirm
that the insulation resistance is more than 100MΩ.
(2) The closing voltage should be less than 85% of the rated voltage of coil.
6-2-3 Cautions in Handling
Items which should be avoided when handling the switch are as follows:
(1) The wire to be connected to the terminal should not be soldered.
The soldered wires becom e loosened with the passage of time and the contact will become imperfect, so that
they should be absolutely avoided.
(2) Do not close the window of the arc suppressing chamber.
The breaking performance may be deteriorated.
(3) Do not mount on an area which is less than the dimensions of the specified minimum mounting space.
There are possibilities that temperature rise may increase and grounding or short circuit may take place at the
time of breaking. (see page 37)
(4) Do not use the switch without an enclosure outdoors.
Mount the switch in a proper enclosure such as water-proof box, etc.
(5) Avoid mounting the switch at a place directly exposed to the rays of the sun, and at a hot place near a boiler,
furnace, etc. Mounting of the switch at such places may cause troubles such as malfunction of thermal overload
relay, burnt-out of operating coil and the like.
(6) The switch should be protected from direct splash of water drops or oil and dust. Place the switch in a water-
proof, drip-proof and dust-proof box during use.
(7) Do not use the switch without an enclosure at a place where there is a concentration of corrosive gas, combustible
gas, salt and the like.
(8) Do not mount the switch at a place subject to abnormal vibration or shock.
(9) Do not apply excessive tensile force to the lead wires or terminals of the operating circuit and the main circuit.
(10) With respect to the wire diameter and length of the operating circuit and the main circuit, their resistance values
should be kept below such resistance values as may impair the performance of t he operating coil. Imperfect
closing of electromagnet will cause troubles.
(11) Closing and releasing coils of latched contactor are rated for a short time, so they should be connected to the
protection circuit without fail, so that voltage is not continuously applied.
(12) Do not turn on and off the power source when the insulated cover is opened.
The insulated cover serves as a barrier between phases; therefore, if the power source is turned on or off while
the insulated cover is opened, there is a possibility that a short circuit between phases may take place.
(13) Do not use the starter for protection against short circuit current.
The contactor and thermal overload relay can only withstand over-current of about 10 times the rated current.
Usually, the short circuit current is 10 to 100 times the rated current, so that the contact is melted and the
heaters of the thermal overload relay are fused by Joule heat. For protection against short circuit, FFB or fuse
are used.
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