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9
2. Direct interference radiated from the plasma cutting leads.
3. Direct interference radiated from feedback into the power lines.
4. Interference from re-radiation of “pickup” by ungrounded metallic objects.
Keeping these contributing factors in mind, installing equipment per the following instructions should
minimize problems.
# Keep the plasma cutter power supply lines as short as possible and enclose as much of them as possible in
rigid metallic conduit or equivalent shielding for a distance of 50 feet (15.2m). There should be good
electrical contact between this conduit and the welder case ground. Both ends of the conduit should be
connected to a driven ground and the entire length should be continuous.
# Keep the work and electrode leads as short as possible and as close together as possible. Lengths should not
exceed 25 feet (7.6m). Tape the electrode and work leads together into one bundle when practical.
# Be sure the torch and work cable rubber coverings are free of cuts and cracks that allow high frequency
leakage.
# Keep the torch in good repair and all connections tight to reduce high frequency leakage.
# The work terminal must be connected to a ground within ten feet of the plasma cutter, using one of the
following methods.
a) A metal underground water pipe in direct contact with the earth for ten feet or more.
b) A 3/4” (19mm) galvanized pipe or a 5/8” (16mm) solid galvanized iron, steel or copper rod driven at
least eight feet into the ground.
# The ground should be securely made and the grounding cable should be as short as possible using cable of
the same size as the work cable, or larger. Grounding to the building frame electrical conduit or a long pipe
system can result in re-radiation, effectively making these members radiating antennas.
# Keep all panels securely in place.
# All electrical conductors within 50ft (15.2m) of the plasma cutter should be enclosed in grounded, rigid
metallic conduit or equivalent shielding. Flexible metallic conduit is generally not suitable.
# When the plasma cutter is enclosed in a metal building, several earth driven electrical grounds connected (as
in 5b above) around the periphery of the building are recommended.
Failure to observe these recommended installation procedures can cause radio or TV interference problems.
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