Tweco 300 MST Arcmaster - Manual (Page 22)

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2.05.03 High Frequency Introduction
The importance of correct installation of high frequency welding equipment cannot be over-emphasized.
Interference due to high frequency initiated or stabilized arc is almost invariably traced to improper
installation. The following information is intended as a guide for personnel installing high frequency
welding machines.
Warning
Explosives
The high frequency section of this machine has an output similar to a radio transmitter. The machine
should NOT be used in the vicinity of blasting operations due to the danger of premature firing.
Computers
It is also possible that operation close to computer installations may cause computer malfunction.
2.05.04 High Frequency Interference
Interference may be transmitted by a high frequency initiated or stabilized arc-welding machine in the
following ways:
Direct Radiation
Radiation from the machine can occur if the case is metal and is not properly grounded. It can occur
through apertures such as open access panels. The shielding of the high frequency unit in the Power
Source will prevent direct radiation if the equipment is properly grounded.
Transmission via the Supply Lead
Without adequate shielding and filtering, high frequency energy may be fed to the wiring within the
installation (mains) by direct coupling. The energy is then transmitted by both radiation and conduction.
Adequate shielding and filtering is provided in the Power Source.
Radiation from Welding Leads
Radiated interference from welding leads, although pronounced in the vicinity of the leads, diminishes
rapidly with distance. Keeping leads as short as possible will minimize this type of interference.
Looping and suspending of leads should be avoided where possible.
Re-radiation from Unearthed Metallic Objects
A major factor contributing to interference is re-radiation from unearthed metallic objects close to the
welding leads. Effective grounding of such objects will prevent re-radiation in most cases.