Tweco SC-3000 - Manual (Page 72)

SC-3000
APPENDIX A-2 Manual 0-5100
APPENDIX 2: GROUNDING A CUTTING MACHINE
This information and recommendations which are described here should help to understand the importance of
correct machine grounding
Furthermore, all manufacturer installation instructions for cutting machines and plasma sources must be complied
with.
The accurate grounding of plasma cutting machines is one of the most important parts to ensure proper function-
ing. This prevents electromagnetic interference (EMI) problems which can disturb electrical devices and causes a
malfunction.
The aim is to achieve low electrical impedance from machine ground to earth ground.
This is described below.
NOTE
It implicates an improper use if no sufficient grounding is provided !
All components of the machine which need grounding must be connected to a single star point. Preferably this star
point is affixed at the cutting table and is connected to a ground rod by a suitable cable.
The distance to the star point should be less than 10' (3 meters). The resistance to ground should be less than 1
Ohms.
All metallic parts of the machine (servos, control console and height control components) must be connected to the
star point.
The four corners of the cutting table must be connected to the rail.
Example of a Cutting machine with a cutting current up to 150 A. The same cables used for welding can be used
as grounding cables.
Figure1: View from above (top view)
Star Point
Rail
Gantry
Torch
Lifter
Plasma source
Positive Plasma Voltage Output (Work Lead)
width of cable 1/0 AWG equivalent 50 qmm
Torch
width of cable 2/0 AWG
equivalent 70 qmm
on all 4 corners
Cutting Table
stranded wire 2/0 AWG
equivalent 70 qmm
Chassis of Machine Control
Ground Rod
width of cable 2/0 AWG
equivalen t 70 qmm
Rail
Art # A-08942_AB
NOTE
For a higher cutting current (more than 150 A) the width of cables should be increased to 4/0 AWG, equivalent
95 qmm.