A 45 A hand plasma cutter needs, as a rough guide, around 100 to 150 l/min at an inlet pressure of about 6 to 8 bar. Flow is not the hard part: what matters is dry air and a pressure that holds throughout the cut. For occasional use, a piston compressor such as the E 75 followed by a dryer does the job; for daily use, a 4-in-1 screw compressor such as the K 75 delivers dry air straight from the unit.
Read the cutter's data sheet
Two figures matter: the air flow, in l/min, and the required inlet pressure, often stated "while cutting". Some sheets give the flow in scfh or CFM: the flow and pressure converter turns it into l/min. The power source has its own regulator, so it needs a little more than its working pressure at the inlet.
Our page on the compressor for plasma cutting gives typical figures for every current rating. Here we deal with the most common case in a workshop: the 45 A hand cutter.
Step-by-step calculation
Example: a 45 A cutter whose data sheet says 140 l/min at 6 bar, in a metal fabrication shop that also uses a blow gun.
- The plasma: a hand cut lasts from a few seconds to a few minutes, but while cutting the power source takes its full flow. Count it at 100%: 140 l/min.
- The blow gun: about 150 l/min, used in bursts. The air receiver smooths those peaks, so count it at half: 75 l/min.
- Subtotal: 140 + 75 = 215 l/min.
- 25% margin for leaks and wear: 215 × 1.25 = 269 l/min, or about 0.27 m³/min.
If other tools run at the same time, such as a grinder or an impact wrench, add them the same way or use the configurator. Always compare the demand with the flow the compressor delivers at working pressure.
Piston or screw for a 45 A plasma?
| Usage | Recommended model | What it brings |
|---|---|---|
| A few cuts a day, ironwork, maintenance | E 75, 7.5 kW piston | 0.9 m³/min, 180 L receiver, 8 or 12.5 bar; add a dryer |
| Cutting every day, several workstations | K 75, 7.5 kW 4-in-1 screw | 1.1 m³/min at 8 bar, 420 L receiver, built-in dryer and filtration |
| Existing network with receiver and dryer | S 55, 5.5 kW standalone screw | 0.6 m³/min at 8 bar |
A piston compressor is designed for intermittent use: it suits a shop that cuts in short runs. Its air comes out hot and wet, so it needs a refrigerated dryer and filtration before the plasma. Once cutting becomes a daily job, or several tools run together, a screw compressor takes over: it handles continuous duty, and the K 75 dries the air on the same frame. See piston vs screw compressor.
The E 75 and the S 55 run on 380 V three-phase, the K 75 on 400 V three-phase. If your workshop only has single-phase power, check this first: see piston compressor, 230 V or 400 V.
Pitfalls specific to a 45 A plasma
- Pressure dropping during the cut. A long, narrow hose or undersized quick couplings are enough to pull the pressure down at the power source. The arc becomes unstable and the cut bevels. Read the power source gauge while cutting, not at rest.
- Water in the torch. The electrode and nozzle are the first victims of wet air. A filter bowl full of water on the power source is a sure sign. See water in compressed air.
- Oily air. No lubricator on the plasma line, and no hose that has already carried oiled air for tools.
- A receiver never drained. On a piston unit, water builds up quickly in the receiver. An automatic condensate drain saves you thinking about it every day.
Send us your cutter's data sheet and the list of your other tools with a quote request: we will check the flow and air treatment with you.
For your trade: Compressor for plasma cutting.