Miller Electric KC237900 Owner's Manual page 35

High-Frequency
Welding Power Source
Electrical
Input
Supply
Figure 8-2. General Rules For Welding Leads
C. Grounding (Earthing) The Weld Cables
Be sure that the enclosure of the high-frequency power
source is firmly grounded to the WORK terminal. If the
high-frequency power source is not labeled as being in-
ternally high-frequency grounded, then this ground
must be made by grounding the enclosure to the WORK
terminal with No. 12 AWG gauge or smaller wire. Con-
nect the ground wire to a driven ground rod or to a water
pipe which enters the earth within 10 ft. (3 m) of the high-
frequency power source.
D. Metal Buildings
Installation of a high-frequency power source within a
suitably bonded and grounded (earthed) metal building
can be an effective means of reducing high-frequency
radiation. Wherever possible, install high-frequency
power sources in such places.
Grounded Copper
Screens
Grounding
Wire
Place leads on floor or on boards
and keep 3/4 in. (19 mm)
to 1 in. (25 mm) apart.
Electrode Holder
Work Clamp
Ground
Metal Building
Panels
Driven Ground Rod
Metal
Panels
Metal
Panels
Bonding Of Metal Panels
Figure 8-3. Grounding And Bonding
Panels Of Metal Building
However, when the high-frequency power source is in-
stalled within a metal building, precautions must be
taken to be sure that the building is properly bonded and
grounded (earthed). This can be accomplished by plac-
ing several good electrical ground rods around the pe-
riphery of the building. During the construction of a new
building of any type having metal in the structure, be
sure that all the reinforcing and structural steel is
bonded together (as by welding each piece of metal to
S-0018
all other adjacent pieces). For metal buildings, adjacent
metal panels should be bolted or welded together at fre-
quent intervals.All windows and doorways should be
covered with grounded copper screen or galvanized
hardware cloth of not more than 1/4 in. (6.4 mm) mesh.
E. Shielding Of Miscellaneous Wiring In The Weld-
ing Zone
Ungrounded, metallic conductors in the welding zone
can act as antennas which will pick up, conduct, and/or
reradiate the high-frequency energy transmitted by the
welding circuit located within or near the welding zone.
This means that all ungrounded water pipes must be
grounded, and that all lighting, power, telephone, com-
munications, and other conductors within the welding
zone must be enclosed in grounded, rigid metallic con-
duit, copper braid, or some other material having an
equivalent shielding capability (spirally wound, flexible,
metallic conduit is not suitable). Shielding of the miscel-
laneous wiring in the welding zone must be grounded at
50 ft. (15 m) intervals. Excellent low resistance electrical
connections must be maintained between conduit sec-
tions (see Figure 8-4).
Copper Strap
Figure 8-4. Bonding Method For Poor Conductors
F. Power Service
The high-frequency power source should be connected
to the line input power supply as instructed in this man-
ual. If the unit is equipped with a power cord, the supply
conductors serving the high-frequency power source
should be completely enclosed in solid metallic conduit,
or in equivalent shielding, up to the point of connection
with the power cord. The solid, metallic conduit, or
equivalent shielding, should extend the entire distance
from the power entrance location in the building to the
high-frequency power source. Shielding should be elec-
S-0019
trically continuous throughout its length and should be
S-0020
OM-530 Page 31