EMC INSTALLATION GUIDELINES
This unit complies with the ElectoMagnetic Compatibility (EMC) standard
listed in the specifications. Although the unit is designed with a high degree of
immunity to ElectroMagnetic Interference (EMI), proper installation and wiring
methods must be followed to ensure compatibility in each application. The type
of the electrical noise, source or coupling method into the unit may be different
for various installations. Listed below are some EMC guidelines for successful
installation in an industrial environment.
1. The unit should be mounted in a metal enclosure, which is properly connected
to protective earth.
a. If the bezel is exposed to high Electro-Static Discharge (ESD) levels,
above 4 Kv, it should be connected to protective earth. This can be done
by making sure the metal bezel makes proper contact to the panel cut-out
or connecting the bezel screw with a spade terminal and wire to
protective earth.
2. Use of shielded (screened) cables for all Signal and Control inputs is
recommended. The shield (screen) pigtail connection should be made as short
as possible. The connection point for the shield depends somewhat upon the
application. Listed below are the recommended methods of connecting the
shield, in order of their effectiveness.
a. Connect the shield only at the panel where the unit is mounted to earth
ground (protective earth).
b. Connect the shield to earth ground at both ends of the cable, usually
when the noise source frequency is above 1 MHz.
c. Connect the shield to common of the unit and leave the other end of the
shield unconnected and insulated from earth ground.
3. Never run Signal or Control cables in the same conduit or raceway with AC
power lines, conductors feeding motors, solenoids, SCR controls, an heaters,
etc. The cables should be run in metal conduit that is properly grounded. This
is especially useful in applications where cable runs are long and portable
two-way radios are used in close proximity or if the installation is near a
commercial broadcaster.
4. Signal or Control cables within an enclosure should be routed as far away as
possible from contactors, control relays, transformers, and other noisy
components.
5. In extremely high EMI environments, the use of external EMI suppression
devices, such as ferrite suppression cores, is effective. Install them on Signal
and Control cables as close to the unit as possible. Loop the cable through the
core several times or use multiple cores on each cable for additional
protection. Install line filters on the power input cable to the unit to suppress
power line interference. Install them near the power entry point of the
enclosure. The following types of EMI suppression devices (or equivalent) are
recommended:
Ferrite Suppression Cores for signal and control cables:
Fair-Rite # 0443167251 (RLC #FCOR0000)
TDK # ZCAT3035-1330A
Steward #28B2029-0A0
Line Filters for input power cables:
Schaffner #FN610-1/07 (RLC #LFIL0000)
Schaffner #FN670-1.8/07
Corcom #1VR3
Note: Reference manufacturer’s instructions when installing a line
filter.
6. Long cable runs are more susceptible to EMI pickup than short cable runs.
Therefore, keep cable runs as short as possible.
7. Switching of inductive loads produces high EMI. Use of snubbers across
inductive loads suppresses EMI.
Snubber: RLC #SNUB0000.
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