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What are the mains supply requirements for arc welding?


Power sources will require either a single or three phase supply at the voltage of the country in which it is intended to be used. Most equipment is provided with a series of voltage tappings and these may need to be adjusted to match the supply voltage. In the UK and the rest of Europe the supply voltages are now 230V AC single phase and 400V AC three phase. In other parts of the world, different supply voltages occur and may vary between regions. In some countries, 220V AC three phase may be encountered. Three phase supplies may be limited to 30A, but higher power welding equipment may require a 45A or even a 60A supply.

From 1999, equipment started to appear with an effective current rating on the rating plate. This value should be used to determine the cable size and fusing requirements. However, national wiring regulations should always be followed.

Particular attention should be paid to the supply requirements for single phase equipment. In many parts of Europe the 230V supply is 16A, but in the UK the standard plug is only 13A. Therefore, the relatively low power output of this type of equipment is further reduced if a 13A plug is fitted, so a dedicated circuit may be required. In some parts of the world the single phase mains supply may be further limited in current, but generally in these countries, three phase supplies will be readily available. Another problem to be wary of is imbalance in the supply, if high powered equipment is connected between two phases of a three phase supply. If more than one power source is installed they should be connected between different phases.

Apart from the obvious hazards of overloading a supply, e.g. overheating and blowing fuses, problems with other equipment may be caused. If the supply has a high impedance (commonly known as soft) as may be the case in overhead cables, a high current draw may cause the voltage of the supply to fall below levels which may cause problems with other equipment.

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