What Duty Cycle Is and Why It Matters When Buying a Machine

Every welder's spec plate has a number many buyers ignore: the duty cycle. Understanding it keeps you from buying a machine that shuts off in the middle of your work.

What the percentage means

Duty cycle is measured over a 10-minute period and tells you how long you can weld continuously before the machine needs to cool down. For example:

• 60% at 200A: you can weld 6 straight minutes, then it needs 4 minutes of rest.
• 30% at 200A: only 3 minutes of welding per 7 of rest.
• 100% at 150A: you can weld non-stop at that amperage.

Note: the percentage is always tied to an amperage. A machine can be 60% at 200A but 100% at 130A.

What happens if you exceed it

The machine overheats and its thermal protection kicks in: it shuts itself off until it cools down. Doing this often shortens the life of internal components. It's not that the machine "fails" — you're running it outside its design.

How much you need, by use

• Hobby and occasional repairs: 20–30% at your working amperage is plenty. You weld in short bursts.
• Shop and frequent projects: look for 40–60%. It gives you room for long beads without interruptions.
• Heavy or production work: 60% or more, or a bigger machine run below its maximum.

A useful trick: if you buy a higher-amperage machine than you need and run it at medium amperage, its effective duty cycle goes way up. A 250A machine run at 150A will almost never overheat.

Always check the spec plate before buying — not just the max amperage in the ad.

Not sure what duty cycle your project needs? At RGV Welding Supply we'll help you pick the right machine — visit us in Pharr or Weslaco.