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3.07 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.
3.08 Duty Cycle
The duty cycle of a welding power source is the percentage of a ten (10) minute period that it can be operated at
a given output without causing overheating and damage to the unit. If the welding amperes decrease, the duty
cycle increases. If the welding amperes are increased beyond the rated output, the duty cycle will decrease.
WARNING
Exceeding the duty cycle ratings will cause the thermal overload protection circuit to become
energized and shut down the output until the unit has cooled to normal operating temperature.
CAUTION
Continually exceeding the duty cycle ratings can cause damage to the welding power source and
will void the manufactures warranty.
NOTE
Due to variations that can occur in manufactured products, claimed performance, voltages, ratings,
all capacities, measurements, dimensions and weights quoted are approximate only. Achievable
capacities and ratings in use and operation will depend upon correct installation, use, applications,
maintenance and service.
