Cutler-Hammer D320 PLC, User Manual

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D320 PLC User's Manual
Troubleshooting
• Noise from magnetic fields induced by other electrical/electronic equipment onto the PLC can
be avoided by relocating the PLC during the design process, installing the PLC in a grounded
steel enclosure, or attaching a filtering or suppression shield/circuit to the device which is
generating the magnetic field.
• Noise from power cables can be corrected by using a different ground for the PLC, an
isolation transformer, attaching a line/ground filter, or changing the power wire connection of
the PLC so that it is closer to the source of the power, therefore lowering the power source
impedance.
•
Noise from lightning should be suppressed by use of surge suppressors that are specifically
designed to protect electronic equipment from lightning.
•
Whenever welding near an electronic device, care must be used to avoid connecting the
ground cable of the welder to a ground of the electronic device. One method of protecting the
PLC is to disconnect the PLC from power and lifting all power and ground connection. An
alternate method is to establish two separate grounds, one for electronic equipment and one
for welding. Test the ground separation carefully before having electronic equipment up and
running while welding.
•
The quickest way to avoid noise from shared cable trays is to have two cable tray runs. One
for power and power control cabling and the other for electronic equipment and low level
control wiring. Proper cable selection with good shielding properties in some instances will
allow both types of cabling/wiring to co-exist in the same tray system.
•
“Grandfather’d” plant wiring has to be analyzed on a case by case basis. The best approach is
to always install new cabling, conduit, and cable tray runs. Though this may not always be
practical, it removes the surprise of high noise and system problems during system startup.
•
Static electricity suppression requires good grounding practices throughout the plant. Static
electricity is a potential difference developed on a material surface due to the loss of protons
or electrons. Since rubbing action can cause the build up of static electricity, the best
protection is to have the electronic equipment enclosed in a grounded housing that requires
the user to first make contact with a safe discharge path. In high static environments like
styrofoam manufacturing or glass manufacturing, electronic equipment should always be
protected from static electricity.