Hypertherm XPR300, Инструкция по эксплуатации

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Qualifications and Requirements
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XPR300 Instruction Manual 809480 61
Recommended grounding and shielding
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.
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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.