Tweco 100XL Plus CE PAK Master - Manuel (Page 23)

Manual 0-2813 3-7 INSTALLATION
5. Make sure work cable and ground cables are properly con-
nected. The work cable must have a solid connection to the
cutting table. The work and ground connections must be
free from rust, dirt, grease, oil and paint. If necessary grind
or sand down to bare metal. Use lock washers to keep the
connections tight. Using electrical joint compound to pre-
vent corrosion is also recommended.
6. The plasma power supply chassis is connected to the power
distribution system ground as required by electrical codes.
If the plasma supply is close to the cutting table (see NOTE)
a second ground rod is not usually needed, in fact it could
be detrimental as it can set up ground loop currents that
cause interference.
When the plasma power supply is far away from the
ground rod and interference is experienced, it may
help to install a second earth ground rod next to the
plasma power supply. The plasma power supply
chassis would then be connected to this ground rod.
NOTE
It is recommended that the Plasma Power Supply
be within 20 - 30 ft (6.1 – 9.1 m) of the cutting
table, if possible.
7. The plasma control cable should be shielded with the
shield connected only at the cutting machine end.
Connecting the shield at both ends will allow ground
loop currents which may cause more interference than
with no shield at all.
C. Creating An Earth Ground
1. To create a solid, low resistance, earth ground, drive a
1/2 in (12 mm) or greater diameter copper clad ground
rod at least 6 - 8 ft (1.8 - 2.4 m) into the earth so that
the rod contacts moist soil over most of its length.
Depending on location, a greater depth may be re-
quired to obtain a low resistance ground (see NOTE).
Ground rods, typically 10 ft (3.0 m) long, may be
welded end to end for greater lengths. Locate the rod
as close as possible to the work table. Install a ground
wire, 1/0 AWG (European 50 mm
2 ) or greater, between the
ground rod and the star ground point on the cutting table.
NOTE
Ideally, a properly installed ground rod will have
a resistance of three ohms or less.
To test for a proper earth ground, refer to the follow-
ing diagram. Ideally, the reading on the multimeter
should be as follows:
• For 115VAC: 3.0 VAC
• For 230VAC: 1.5 VAC
A-02971
+
_
Meter set to
VAC setting
Machine
Earth Ground
Neutral
Line (Hot)
100W
Light Bulb
115 or 230VAC
WARNING
Use extreme caution. This
test uses live voltage.
115VAC: 3.0 VAC
230VAC: 1.5 VAC
V ~
V
~
VR COM A
Ground Testing
2. Increasing the ground rod length beyond 20 - 30 ft (6.1 – 9.1
m) does not generally increase the effectiveness of the
ground rod. A larger diameter rod which has more surface
area may help. Sometimes keeping the soil around the
ground rod moist by continuously running a small amount
of water into it will work. Adding salt to the soil by soaking
it in salt water may also reduce its resistance. When these
methods are used, periodic checking of the ground resis-
tance is required to make sure the ground is still good.
D. Routing Of Torch Leads
1. To minimize RF interference, position torch leads as
far as possible from any CNC components, drive mo-
tors, control cables, or primary power lines. If cables
have to pass over torch leads, do so at an angle. Do
not run the plasma control or other control cables in
parallel with the torch leads in power tracts.
2. Keep torch leads clean. Dirt and metal particles bleed off
energy, which causes difficult starting and increased chance
of RF interference.