Miller Electric KC237900 HIGH-FREQUENCY Radiation, Location, General Installation Procedures

L. High Frequency

High frequency is radio frequency energy, either con- tinuous or pulsed, used to start or stabilize a welding arc.

M. High-Frequency Assisted Arc Welding

High-frequency assisted arc welding refers to any of the arc welding processes requiring high frequency.

N. Interference

Interference is the unwanted and problematic reception of high-frequency energy.

O. Radiation

Radiation is the transmission of high-frequency energy through space.

8-3. HIGH-FREQUENCY RADIATION

Installations using high frequency, either as an integral part of the power source or as an accessory unit, will produce some high-frequency radiation. Such radiation, if the signal strength is sufficient at the receiving device,

8-4. LOCATION

Locate the high-frequency power source as close to the welding process as possible. Also consider the near- ness of a suitable ground connection when selecting a site for the installation of the power source. Ideally, the high-frequency power source should be located in an area where there is a limited amount of miscellaneous wiring (lighting, power, telephone, communications, and other unshielded conductors) located within the welding zone. Ungrounded, metallic conductors in the welding zone can act as antennas which will pick up, conduct, or reradiate the high-frequency energy transmitted by the welding circuit. All miscellaneous wiring in the welding zone should be enclosed in grounded, rigid metallic con- duit, copper braid, or some other material having an equivalent shielding efficiency, and grounded at 50 ft. (15 m) intervals (see Figure 8-1).

Shielded Wire

Electrode

Holder

can cause an inconvenience or disruption of communi- cations or can cause malfunction in sensitive electronic controls and systems. The four major causes of high- frequency radiation are as follows:

A.Direct Radiation From The Power Source Or High-Frequency Accessory Unit

Direct radiation is that radiation emanating directly from the power source or accessory unit. Radiation from the power line and welding power source accessories is not considered to be direct radiation from the power source or accessory unit.

Ground At 50ft.

(15 m) Intervals

50 ft.

(15 m)

Work Clamp

High-FrequencyGround

Welding

Power Source

Keep all unshielded and ungrounded

wires out of the welding zone.

S-0017

B. Direct Radiation From The Welding Circuit

Any attachment to the output terminals of the high-fre- quency source is capable of acting as an antenna and radiating high-frequency energy. Attachments include weld cables, torches, worktables, etc. Since direct ra- diation from the welding circuit is the major source of ra- diation, it is important to keep attachments to a mini- mum.

C.Conduction And Radiation From The Power Line

Most power lines are capable of conducting high-fre- quency energy which may cause interference directly or by reradiation from these power lines. Normally such ra- diation is small when compared to that caused by radia- tion from the weld cables.

D. Reradiation

Radiation from the welding circuit can be picked up by ungrounded metal objects or unshielded wiring in the immediate vicinity, conducted some distance, and reradiated. This can be a troublesome source of inter- ference.

Figure 8-1. Requirements To Minimize Reradia- tion Pickup In The Vicinity Of The Welding Zone

8-5. GENERAL INSTALLATION PROCEDURES

A. Weld Cables

Keep the weld cables as short as possible and do not exceed 25 ft. (8 m) in length. Position the cables as close together and as close to the floor or ground plane as possible.

If the welding operation must be carried out at a point farther than 25 ft. (8 m) from the welding power source, use a portable high-frequency source and locate the portable unit within 25 ft. (8 m) of the welding electrode.

B.High-Frequency Assisted Arc Welding Power Sources

When the high-frequency assisted arc welding power source is in operation, all service doors and covers must be closed, securely fastened, and adequately bonded to ensure good contact around the entire perimeter of the opening. Except for changes and adjustments allowed by the manufacturer, the high-frequency assisted arc welding power source should not be modified.

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