Taking the mystery out of air plasma power supply specifications - part 3

By Hypertherm
Posted on 10/08/2014 in SPARK the blog, Plasma cutting

Guest post by Jim Colt, technology applications engineer

When it comes to air plasma power supply specifications, it’s important to fully understand the various ratings to get a clear picture of a system’s true capabilities. I’ve written about rated open circuit voltage, rated output current, rated output voltage, and duty cycle in past posts. Today, I’m going to cover the final specifications I think you should know about.

Operating temperature considers the minimum and maximum temperature a system’s internal components can handle. These are things like the PC board, transformers, switching devices, etc. While the systems certainly will operate at temperatures that are lower and higher than the ones listed (I have personally exceeded specs on both ends of the spectrum,) it is possible that power supply output accuracy in terms of amperage, voltage, starting/stopping power ramps, etc. may be affected. This in turn can impact cut quality and / or torch performance.

Storage temperature is hopefully self-explanatory. This is the temperature at which you store your system when not in use.

Power factor provides the efficiency of a particular power supply. It tells you how much of the power coming from your shop’s electrical circuit is actually getting to the torch. Higher is better. A well designed plasma cutter can have a 90 percent efficiency rating, compared with an industrial CO2 laser system which may have an efficiency rating of 15 to 20 percent.

Input voltage indicates the different available voltages that the units will operate at, and the current (amperage) draw on the shop power system. As with all electrical equipment, higher input voltages will use less amperage and cost you less.

Gas quality tells you the type of gas (in this case, air) needed to achieve the best cut quality. The spec sheet for this particular system calls for clean, dry, oil free air. In addition to air quality, you’ll want to consider the amount of air getting to your system. Often when someone is having cut quality problems it’s not because of bad air. Rather the problem is not enough air. There could be a leak in the air line, or more common, too many filters between the air compressor and plasma input causing a drop in air pressure.

Inlet gas flow and pressure helps you determine the size of the compressor needed for plasma cutting. The number shown on this specification sheet is the maximum rating using the largest (highest amperage, nozzle size) set of consumables. If you use a lower powered consumable set, you’ll use less air.

If you are looking for best performance in terms of cut quality, cut speed, and consumable life when plasma cutting it is important to have an understanding of these basic specifications. This is only the beginning though. I hope to talk about different aspects of plasma cutters in upcoming posts. Stay tuned for posts on torch design (Are they all the same?); consumable design (Why do some systems use one nozzle / tip for the whole cutting range where others have multiple choices?); and power supply DC output characteristics.