welding machines interact with the electrical supply in one of three ways, and these different power sources produce different types of arc that are useful in specific welding situations. Each different electrical characteristic produces an arc that matches certain welding needs, so pick your power source carefully depending on the type of welding you are likely to do most.
Although the subject is a detailed one that relies on a technical understanding of the different types of arc and current delivery, you can get a good grasp of the basics quickly and should do so in order to make the most of your welding equipment. Using the wrong kind of current to power your welding arc could result in substandard welds that will not last as long as a properly created weld, or which will fail to “take” entirely when you first attempt to make them.
Constant Current power sources (CC)
Constant current power supplies give you a steady amperage while voltage can vary. With fixed amperage, the volume of electricity remains unchanging, while the speed with which it’s delivered can change as the voltage changes. You need to be careful not to use such a machine with excessively low voltage, since this will cause extra resistance in the circuit, beyond what is needed to create the welding heat, and too much heat may build up as a result.
CC power sources are used in a wide range of ways, depending on how the specific welding machine was built. Some machines furnish alternating current (AC) or direct current (DC), while a third type can be changed back and forth between the two current varieties. It is considered that mastery of a CC welding machine is essential to a career in welding, and many welding operations use a CC welding test to determine if new candidates should be hired.
In practical terms, amperage controls the penetration of the weld bead into the metal, while voltage controls the width of the weld bead. A constant current (CC) power source will reliably produce a certain depth of weld. Voltage varies, however putting the welding torch close to the workpiece and creating a short arc will lower voltage, thus narrowing the bead, while “pulling a long arc” moving the welding torch away from the workpiece will increase voltage and make a wide bead.
Constant Voltage power sources (CV)
Constant voltage (CV) power sources are the opposite of CC power sources, and allow you to set a voltage which will then remain constant, automatically adjusting the voltage as you vary the arc length by moving your welding gun closer to or farther from the workpiece. Thus, the width of the bead is fixed throughout the process, with high voltage making a wide bead and low voltage making a narrow bead.
Amperage, however, is variable. Since amperage controls the depth (penetration) of the weld, working with a short arc will produce deep penetration, while a long arc will create shallow penetration. All wirefeed welding is carried out using a CV power source.
CC/CV power sources
Some welding machines can provide either CC or CV, and can be used with every kind of arc welding. They are more costly, of course often, much more costly but if you are planning a varied welding career, they are an excellent investment.