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Appendix A. EMC Standard Installation GuideEB3000
The reflection loss depends on the source of the electromagnetic wave and the distance from that source.
For a rod or straight wire antenna, the wave impedance increases as it moves closer to the source and
decreases as it moves away from the source until it reaches the plane wave impedance (377) and shows
no change. If the wave source is a small wire loop, the magnetic field is dominant and the wave
impedance decreases as it moves closer to the source and increases as it moves away from the source;
but it levels out at 377 when the distance exceeds one-sixth of the wavelength.
Electrical Cabinet Design
In a high frequency electric field, shielding can be achieved by painting a thin layer of conductive metal
on the enclosure or on the internal lining material. However, the coating must be thorough and all parts
should be properly covered without any seams or gaps (just like a Faraday cage). That is only the
ideal. Making a seamless shielding shell is practically impossible since the cage is composed of metal
parts. In some conditions, it is necessary to drill holes in the shielding enclosure for installation of
accessories (like optional cards and other devices).
1. If the metallic components are properly welded using sophisticated welding technology to form an
electrical cabinet, deformation during usage is unlikely to occur. But if the electrical cabinet is
assembled with screws, the protective insulating layer under the screw must be properly removed
before assembly to achieve the greatest conductivity and best shielding.
2. Drilling holes for the installation of wires in the electrical cabinet lowers the shielding effectiveness
and increases the chance of electric waves leaking through the openings and emitting interference.
We recommend that the drilled holes are as narrow as possible. When the wiring holes are not
used, properly cover the holes with metal plates or metal covers. The paint or the coating of the
metal plate and metal cover should be thoroughly removed to ensure a metal-to-metal contact or a
conductive gasket should be installed.
3. Install industrial conductive gaskets to completely seal the electrical cabinet and the cabinet door
without gaps. If conductive gaskets are too costly, please screw the cabinet door to the electrical
cabinet with a short distance between the screws.
4. Reserve a grounding terminal on the electrical cabinet door. This grounding terminal shall not be
painted. If the paint already exists, please remove the paint before grounding.
Electrical Wires and Cables
Shielded Twisted Pair (STP) is a type of cable where two insulated copper wires are twisted together
with a metal mesh surrounding the twisted pair that forms the electromagnetic shielding and can also
be used for grounding.
The individual electrical wires and complete cable are surrounded by (synthetic) rubber that provides
insulation and also protects against damage.
There are two types of electrical cables: high voltage and low voltage. The high voltage cable differs
from the low voltage cable in that it has an additional insulation layer called the dielectric insulator
within the plastic sleeve. The dielectric insulator is the most important component in insulation. The
low voltage cable is usually only filled with a soft polymer material for keeping the internal copper wire
in place.
A-16
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