Hypertherm THC ArcGlide - Manual (Page 55)

ArcGlide THC Instruction Manual 806450 55
2 – Installation
Recommended grounding and shielding practices
Introduction
This section describes practices for grounding and shielding to protect a plasma cutting system against radio frequency
interference (RFI) and electromagnetic interference (EMI) (also called
noise). It also describes the DC power ground and
the service ground. The diagram at the end of this section shows these types of grounds in a plasma cutting system.
 The grounding practices in this section have been used on many installations with excellent results, and Hypertherm
recommends that these practices be a routine part of the installation process. The actual methods used to implement
these practices may vary from system to system, but should remain as consistent as possible. However, due to the
variation in equipment and installations, these grounding practices may not succeed in every case to eliminate RFI/EMI
noise issues.
Types of grounding
Service ground (also called safety ground or potential earth (PE) ground) is the grounding system that applies to the
incoming line voltage. It prevents a shock hazard to any personnel from any of the equipment or the cutting table. It
includes the service ground coming into the plasma system and other systems such as the CNC and the motor drives, as
well as the supplemental ground rod connected to the cutting table. In the plasma circuits, the ground is carried from the
plasma system chassis to the chassis of each separate console through the interconnecting cables.
DC power ground (also called cutting current ground) is the grounding system that completes the path of the cutting
current from the torch back to the plasma system. It requires that the positive lead from the plasma system be firmly
connected to the cutting table ground bus with a properly sized cable. It also requires that the slats, on which the
workpiece rests, make firm contact with the table and the workpiece.
RFI and EMI grounding and shielding is the grounding system that limits the amount of electrical noise emitted by
the plasma and motor drive systems. It also limits the amount of noise that is received by the CNC and other control and
measurement circuits. The grounding practices described in this section mainly target RFI and EMI grounding and
shielding.
Grounding practices
1. Unless noted, use only 16 mm 2 (6 AWG) welding cables (047040) for the EMI ground cables shown on the diagram
at the end of this section.
2. The cutting table is used for the common, or star, EMI ground point and should have threaded studs welded to the
table with a copper bus bar mounted on them. A separate bus bar should be mounted on the gantry as close to
WARNING!
ELECTRIC SHOCK CAN KILL
Disconnect electrical power before performing any maintenance.
All work requiring the removal of the plasma system cover must be performed
by a qualified technician.
See the Safety section of your manual for more safety precautions.