The Lowdown on Welding Power Sources

There is no welding power source solution that fits all needs. Having an understanding of your application, your future needs and your environment will help you pick the right power source.

There is not a “one-size-fits-all” solution when it comes to selecting a welding power source. There are a number of considerations a company should understand before investing in a fleet of welding equipment pertaining to processes, capabilities, power, size, space and future plans for growth.

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New technologies are also being added to welding power sources that help simplify the training process and shorten the learning curve – a major help as companies still struggle to find skilled/trained welding operators.

Working with your local welding distributor and manufacturer representatives can help determine the right power source for your operation.

In this article we will examine a few of the key factors in selecting a welding power source and what you should know when you start looking.

BASE MATERIALS DETERMINE PROCESSES
Though this may seem basic for some (if so, please feel free to skip ahead), it is still a good foundation: the type of welding power source is going to be determined largely by the type and thickness of the materials you are welding.

There are many types of power sources to choose from, including those dedicated to MIG, TIG and Stick, as well as multiprocess units capable of performing all three processes and more.

Engine-driven welder/generators may provide the greatest flexibility for outdoor and/or mobile work (although this article focuses on power sources plugged into primary input power in industrial environments).

The base metal you work with is the first strong indicator to the capabilities you will need, because some materials and welding processes are not compatible.

Steel and stainless steel are capable of being welded with numerous processes, while titanium is typically welded best with only the DC TIG process. Aluminum works best with MIG and AC TIG. See Figure 1 for a breakdown of common material types and processes.

UNDERSTANDING OUTPUTS AND CAPABILITIES
There are two primary factors that determine output power: material thickness and the diameter of the wire or electrode you are welding with. As a general rule of thumb, one amp of power is required for every .001 inch of mild steel.

For example, to weld 1/8 in (.125 in) mild steel, you would need approximately 125 amps. Stainless steel needs about 10 percent less power, while aluminum requires about 25 percent more power.

Wire/electrode diameter further determines output requirements as each has a specific operating range. Smaller electrodes carry less current while larger electrodes carry more current. The chart depicted in Figure 2 suggests operating ranges for common Stick, TIG and MIG/Flux-Cored wires/electrodes.

UNDERSTANDING 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 10-minute 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.

Power sources designed for light industrial or home/hobby use typically feature a 20 percent duty cycle with rated outputs of 230 amps or lower.

Industrial products more commonly found in production environments typically have a 40 to 60 percent duty cycle with rated outputs up to 300 amps. Heavy-duty industrial products typically have a 60 to 100 percent duty cycle and a rated output of at least 300 amps.

One of the most common mistakes people make is under-sizing their power source by not understanding duty cycle. It’s not simply enough that a power source can provide 300 amps of output. If you’re in a production environment and it can only provide 300 amps for four minutes out of every 10, that is not optimal arc-on time.

UNDERSTANDING INPUT POWER REQUIREMENTS AND ENERGY EFFICIENCY
Welding power sources need to be matched to the type of primary power available: single-phase (home, garage, barn), typically 115, 200, or 230 VAC; or three-phase (industrial), typically 230, 460 or 575 VAC.

Linking/input power management technologies are available that automatically accept single- or three-phase power, as well as multiple voltages without any manual re-linking.

The amount of electricity a welding system pulls will ultimately depend on the type of system you select.