Miller Electric KC237900 Metal Buildings, Shielding Of Miscellaneous Wiring In The Weld- ing Zone

High-Frequency

Welding Power Source

Electrical

Input

Supply

Place leads on floor or on boards

and keep 3/4 in. (19 mm)

to 1 in. (25 mm) apart.

Electrode Holder

Work Clamp

GroundS-0018

Figure 8-3. Grounding And Bonding

Panels Of Metal Building

However, when the high-frequency power source is in- stalled within a metal building, precautions must be taken to be sure that the building is properly bonded and grounded (earthed). This can be accomplished by plac- ing several good electrical ground rods around the pe- riphery of the building. During the construction of a new building of any type having metal in the structure, be sure that all the reinforcing and structural steel is bonded together (as by welding each piece of metal to all other adjacent pieces). For metal buildings, adjacent metal panels should be bolted or welded together at fre-

Figure 8-2. General Rules For Welding Leads

C. Grounding (Earthing) The Weld Cables

Be sure that the enclosure of the high-frequency power source is firmly grounded to the WORK terminal. If the high-frequency power source is not labeled as being in- ternally high-frequency grounded, then this ground must be made by grounding the enclosure to the WORK terminal with No. 12 AWG gauge or smaller wire. Con- nect the ground wire to a driven ground rod or to a water pipe which enters the earth within 10 ft. (3 m) of the high- frequency power source.

D. Metal Buildings

Installation of a high-frequency power source within a suitably bonded and grounded (earthed) metal building can be an effective means of reducing high-frequency radiation. Wherever possible, install high-frequency power sources in such places.

Grounded Copper	Metal Building
Screens	Panels

Driven Ground Rod

quent intervals.All windows and doorways should be covered with grounded copper screen or galvanized hardware cloth of not more than 1/4 in. (6.4 mm) mesh.

E.Shielding Of Miscellaneous Wiring In The Weld- ing Zone

Ungrounded, metallic conductors in the welding zone can act as antennas which will pick up, conduct, and/or reradiate the high-frequency energy transmitted by the welding circuit located within or near the welding zone. This means that all ungrounded water pipes must be grounded, and that all lighting, power, telephone, com- munications, and other conductors within the welding zone must be enclosed in grounded, rigid metallic con- duit, copper braid, or some other material having an equivalent shielding capability (spirally wound, flexible, metallic conduit is not suitable). Shielding of the miscel- laneous wiring in the welding zone must be grounded at 50 ft. (15 m) intervals. Excellent low resistance electrical connections must be maintained between conduit sec- tions (see Figure 8-4).

Copper Strap

S-0020

Figure 8-4. Bonding Method For Poor Conductors

Grounding Wire

Metal

Panels

Metal

Panels

F.Power Service

The high-frequency power source should be connected to the line input power supply as instructed in this man- ual. If the unit is equipped with a power cord, the supply conductors serving the high-frequency power source should be completely enclosed in solid metallic conduit, or in equivalent shielding, up to the point of connection with the power cord. The solid, metallic conduit, or equivalent shielding, should extend the entire distance from the power entrance location in the building to the high-frequency power source. Shielding should be elec-

Bonding Of Metal Panels S-0019

trically continuous throughout its length and should be

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