MACHINE GROUNDING AND HIGH FREQUENCY
INTERFERENCE PROTECTION
The welder must be grounded. See your local and national electrical
codes for proper grounding methods.
The high frequency generator, being similar to a radio transmitter, can
be blamed for radio, TV and electronic equipment interference problems.
These problems may be the result of radiated interference. Proper
grounding methods can reduce or eliminate radiated interference.
Radiated interference can develop in the following four ways:
1. Direct interference radiated from the welder.
2. Direct interference radiated from the welding 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.
1. Keep the welder 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.
2. Keep the work and electrode leads as short as possible and as close
together as possible.
Lengths should not exceed 25 ft (7.6m). Tape the leads together when
practical.
3. Be sure the torch and work cable rubber coverings are free of cuts
and cracks that allow high frequency leakage.
4. Keep the torch in good repair and all connections tight to reduce
high frequency leakage.
5. The work piece must be connected to an earth ground close to the
work
clamp, using one of the following methods:SQUARE WAVE TIG 175
A-4
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.
6. Keep cover and all screws securely in place.
7. Electrical conductors within 50 ft (15.2m) of the welder should be
enclosed in grounded rigid metallic conduit or equivalent shielding,
wherever possible.
Flexible metallic conduit is generally not suitable.
8. When the welder is enclosed in a metal building, the metal building
should be connected to several good earth driven electrical grounds (as
in 5 (b)
above) around the periphery of the building.
Failure to observe these recommended installation procedures can cause
radio or TV and electronic equipment interference problems and result
in
unsatisfactory welding performance resulting from lost high frequency
power."