Tweco 6000GST Merlin Plasma Cutting CE Slave Power Supply - Manual (Page 23)

Manual 0-2653 3-5 INSTALLATION PROCEDURES
2. Grounding for components mounted on the cutting table
(CNC controllers, height controllers, plasma remote con-
trols, etc.) should follow the manufacturer’s recommenda-
tions for wire size, type, and connection point locations.
For Thermal Dynamics components it is recommended to
use a minimum of 10 AWG (6.00 mm
2 European) wire or flat
copper braid with cross section equal to or greater than 10
AWG connected to the cutting table frame. The connec-
tion point must be clean bare metal; rust and paint make
poor connections. For all components, wires larger than
the recommended minimum can be used and may improve
noise protection.
3. The cutting machine frame is then connected to the “Star”
point using 1/0 AWG (50.0 mm 2 European) or larger wire.
4. The plasma power supply work cable (see NOTE) is con-
nected to the cutting table at the single point “Star” ground.
NOTE
Do Not connect the work cable directly to the
ground rod.
5. Make sure work cable and ground cables are prop-
erly connected. 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 electri-
cal joint compound to prevent corrosion is also recom-
mended.
6. The plasma power supply chassis is connected to the
power distribution system ground as required by elec-
trical codes. If the plasma supply is close to the cut-
ting table (see NOTE) a second ground rod is not usu-
ally 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 (50.0 mm
2 European) or greater, be-
tween 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