How To Choose Welding Power Sources
The primary function of a welding power source is to convert electrical power into a current type that is suitable for the welding application being performed.
But with such a wide selection of power sources on the market, how do welders select the right one for them? To make the best choice, you need to pair your material type with the welding process and the best method of supplying power to the arc.
Whether you’re new to welding and looking to invest in new manual welding machines or ready to upgrade an outdated welder to a more modern piece of automatic welding equipment, we’re here to explore a few of the key factors in selecting a right welding power source.
Choose the welding process
Gas Metal Arc Welding (GMAW) and Flux-Cored Arc Welding (FCAW)
MIG or Flux-Core Welding uses a spool of wire that is either housed inside the power source or fed from an external wire feeder. This wire or filler material is fed through a welding gun. The power source is used to start and maintain the arc between the wire and the base metal.
GMAW requires the least operator skill, because the machine feeds the wire. The welding operator holds the gun in one hand, squeezes the trigger, and welds.
The speed, simplicity, and ease of GMAW welding combined with the flexible tolerance on electrode positioning and manipulation has led this form of welding to be a very popular process. MIG WELDER
Shielded Metal Arc Welding or Stick Welding (SMAW)
Most DIYers use mostly shielded metal arc welding, also known as stick welding.
This is the most common form or ARC Welding. A stick or electrode is placed at the end of a holder and an arc is struck between the tip of the electrode and the metal welding surface.
SMAW is one of the easiest and most versatile ways to weld, since filler material can be easily changed to match different metals just by switching stick electrodes. Whether it is steel, stainless steel, cast iron or high alloy metals
When compared to other types of power sources, SMAW welders are generally the least expensive. As a result, they are utilized most often by novice welders, small shops, and shops welding a variety of jobs for a large project. Stick Welder
Gas Tungsten Arc Welding (GTAW)
In GTAW—or TIG welding—an arc is established between a non-consumable tungsten electrode and the base metal. The arc zone is filled with an inert gas, typically argon, which protects the tungsten and molten metal from oxidation and provides an easily ionized path for the arc current.
GTAW produces high quality welds on almost all metals and alloys. Because it can be controlled down to very low amperages making it ideal for thinner materials.
Its biggest disadvantage is speed—GTAW is by far the slowest welding process, requires precise movements, and more involved setup.
Submerged Arc Welding (SAW)
SAW uses a continuously fed wire with a granular material called flux to cover the weld area. This type of welding is used primarily on heavier plate applications such as structural steel and on specialized high speed welding of light sections.
The flux plays a central role in achieving high speed and a quality weld. Very little welding fume is produced, leaving the shop air much cleaner. Since the flux covers the whole arc, a welding helmet is not required, leading to a higher operating factor.
On long, large welds, multipass and overlay applications, the process can approach a 100 percent operating factor. Productivity can be very high with welding currents over 1000 amps common on automatic applications.
Disadvantages include limited welding positions, because flux comes in granular form. Operators must weld on flat surfaces to assure the flux covers the weld puddle. Another disadvantage is that hot flux can burn shoes and cause handling problems that must be addressed.
Select the Proper Power Supply
Welding power source types are defined by how they modulate electrical currents and what arc welding process is best supported by this modulation:
Direct Current (DC)
A DC power source is a flow of electrons in a single direction through a circuit. In welding, it creates a steadier arc and smoother output. It can be used to weld with a negative ground, or the flow of electrons can be reversed to flow toward a positive ground in reverse polarity.
Alternating Current (AC)
The AC power source is the bidirectional flow of electrons in which the polarity shifts a hundred or more times per second from a negative to a positive ground. Arcs tend to be less stable and welding is harder to control. However, AC welding can break apart oxide formation and allow for purer welding in some processes.
Pulsed Current
This is a form of DC welding in which the current goes from a high peak current to a lower background current at a frequency determined by the operator. This narrows the arc, allowing greater penetration while reducing the effect on surrounding materials. As a result, pulsed current welding is an excellent choice for welding thin metal or performing deep welds on thicker materials.
Pulsed Voltage and Heat
Pulsing GMAW power supplies focus on controlling pulsed voltage and heat applied to the consumable electrode. Controlling the pulsed voltage (heat) and wire feed speed allows greater control over how the wire melts and the rate of deposition. Adaptive pulse GMAW carefully monitors feedback and automatically compensates to keep the arc consistent despite variation by the welder and differences in height and joint location.
Additional Items to Consider
Once you have your welding process and the type of power source selected you should consider a few more key items to determine the size including:
Your power source needs to match the type of input power available. The amount of electricity your welding system needs will ultimately depend on the type of power supply you select.
- Single-phase: 115, 200 or 230 VAC
- Three-phase: 230, 460 or 575 VAC
Material Thickness
Simply put, the thicker the material the more power required.
Duty Cycle
Another way of classifying a welding power source’s size (and matching it to your work demands) is by how much amperage it can generate at a given duty cycle. Duty cycle is the percentage of arc on-time a welding power source can operate in a given period.
For example, certain TIG welding power sources can deliver 300 amps of welding output at a 60 percent duty cycle. It can weld continuously at 300 amps for six minutes, and then must cool down during the remaining four minutes to prevent overheating.
One of the most common mistakes welders make is under-sizing their power source. It’s important to understand how much amperage your power source can generate at any given duty cycle and ensure it’s MORE than enough to meet your demands.
