Gas or battery power is used in welding machines. Simple welds may only require very low electricity (a few amperes). A minimum of 80 amperes is used for high current welding jobs. Spot welding requires 12,000 amperes. Welding machines regulate electrical output as a constant current or constant voltage. Constant current welders change the electrical output to maintain a particular current. Constant voltage welders change the electrical output to maintain a particular voltage. Welders use various power sources, such as a simply car battery or a mechanical generator. The latter produces power to the welder by converting mechanical force into electrical energy. The mechanical force is generated by an internal combustion engine. Manufacturing welding machines are usually automated, and utilize a high frequency inverter welder (ten thousand hertz and above). All electrical output and transformation in an automated, high frequency inverter welder is controlled by computer software.
Current, Voltage and Frequency
Constant currents are used in shield metal arc welding to maintain a preset number of amps in the electrical output. However, gas metal arc welding will use a constant voltage output, since the arc length is not manually adjustable. Transformer welding machines transform high voltage/low current input to a high current/ low voltage output. A lift arc feature allows the operator to weld delicate metals (such as aluminum). By selecting the lift arc setting, the operator is able to lower the frequency output enough to ensure safe welding and repair work around sensitive electrical apparatus. Ensure the ground wire is clamped on to the surface of the work to be welded.
Welding machines generate an arc from either a ball end electrode or a fine point. Arcs tend to travel a bit off track with a ball end electrode. To reduce arc wandering, use only the products that include a fine end welding torch. In order to distinguish between a fine end and a ball end electrode, look for machines which have a wire that protrudes from the nozzle of the welding torch (fine end). Ensure the arc is held away from the work piece when arc welding (Some hobby welders require the nozzle to be carefully dragged across the work area like a match [igniting the welder tip]).
Spot welding machines utilize a pair of electrode clamps to permanently join two sheets of metal together. An electric current passes from one electrode to the other electrode. In the process of electrical energy moving between the electrodes, the metal becomes very hot, causing the molecules in the metal to become excited. When the metal cools, the molecules stop moving, resulting in a permanent bond between the two metal sheets.