Radio Frequency (Rf) And Electromagnetic Interference (Emi) - Lincoln Electric FineLine 12864 Operator's Manual

FineLine 300HD Plasma System

3.3 Radio Frequency (RF) and Electromagnetic Interference (EMI)

3.3.1 Overview
This section describes the proper grounding of the System components to minimize
Radio Frequency (RF) and Electromagnetic Interference (EMI).
The Arc Start Console (ASC), by nature of its function in the plasma system, is a
source of RF/EMI along with other system components such as drive amplifiers. If
proper grounding techniques are not employed during system installation, RF/EMI
can couple into other components causing system malfunction and/or component
failure. While this section outlines best practices for grounding, this does not
guarantee system immunity. These guidelines should be the basis for initial
installation and modifications made as necessary to achieve complete immunity.
3.3.2 Types of Grounds
There are three different types of grounds in a plasma system.
Service or Protective Earth (PE) ground. This is the ground associated with the
mains power supplied to the System. The purpose is to prevent a shock hazard
with respect to the plasma equipment and work table. It represents the Service
ground connected to the plasma and all other system components such as
drive amplifiers and CNC. The PE or Service ground must be connected to
each piece of equipment per local and national codes.
DC power ground. This is the work lead of the Power Supply and is connected
to the cutting table to complete the electrical path for the cutting current.
RF/EMI ground. This is the ground for limiting RF/EMI noise in the System. This
is the ground that this section addresses.
3.3.3 RF/EMI Grounding Rules
The cutting table is used as the common star grounding point. All RF/EMI grounds
should terminate at this point. The star ground connection to the table should have
welded studs to the table with a copper bus bar mounted to them. All hardware used
for ground connections should be copper or brass with exception of the studs
welded to the table.
A ground rod that meets all applicable local and national electrical codes must be
installed within 20 ft. (6.10m) of the star ground point. The ground rod should be
connected to the star ground with a minimum of a 6 AWG green/yellow cable.
The work, electrode and pilot arc leads from the Power Supply should be bundled
together for as long a distance as possible and segregated from control leads.
Ideally the power and control leads should run in separate cable tracks – if not, a
minimum separation of 6 in. (152.4mm) is recommended.
The braided shield on the torch leads must be electrically connected to the ASC and
to the torch handle. The length of the braid must be insulated from any metal contact
or contact with the floor. The braid can be insulated with a plastic or leather sheath
or run in a plastic track.
This information is subject to the controls of the Export Administration Regulations [EAR]. This information shall not be provided to
non-U.S. persons or transferred by any means to any location outside the United States contrary to the requirements of the EAR.
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