Hypertherm HPR260 Manual Gas Preventive Maintenance Program Rev.5 - Manual (Page 55)

INSTALLATION
3-6 HPR260 Auto Gas Instruction Manual
5
Recommended grounding and shielding practices
Introduction
This document describes the grounding and shielding necessary to protect a plasma cutting system installation against
radio frequency interference (RFI) and electromagnetic interference (EMI) noise. It addresses the 3 grounding systems
described below. There is diagram on page 5 for reference.
Note: These procedures and practices are not known to succeed in every case to eliminate RFI/EMI noise
issues. The practices listed here have been used on many installations with excellent results, and we
recommend 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 across the product line.
Types of grounding
A. The safety (PE) or service ground. This 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 work table. It includes the service ground coming
into the plasma power supply and other systems such as the CNC controller and the motor drivers, as well as the
supplemental ground rod connected to the work table. In the plasma circuits, the ground is carried from the plasma
power supply chassis to the chassis of each separate console through the interconnecting cables.
B. The DC power or cutting current ground. This is the grounding system that completes the path of the cutting current
from the torch back to the power supply. It requires that the positive lead from the power supply be firmly connected
to the work table ground bus with a properly sized cable. It also requires that the slats, on which the workpiece rests,
make good contact with the table and the workpiece.
C. RFI and EMI grounding and shielding. This 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. This grounding/shielding process is the main target of this document.
DANGER
ELECTRIC SHOCK CAN KILL
Disconnect electrical power before performing any maintenance. All work
requiring the removal of the power supply cover must be performed by a
qualified technician.
See Section 1 of the plasma system instruction manual for more safety
precautions.