Duty Cycle
Why your machine needs breaks — the 10-minute cycle on the nameplate
AI generated The duty cycle tells you how long a welding machine can run at a given current before it needs to cool down. It's shown as a percentage on the nameplate — and if you ignore it, you'll run your machine into thermal protection or destroy it.
On the nameplate of every welding machine there's a percentage that many overlook — the duty cycle. It's the most important number when you're deciding whether a machine can handle your work or not.
The duty cycle is based on a 10-minute cycle at 40 °C ambient temperature. If the nameplate says, for example, “60% at 200 A,” that means the machine can run 6 minutes at 200 A under load and then must cool down for 4 minutes before the cycle starts over.
Here's why: every power source generates heat — especially in the transformer, the power semiconductors, and the heat sinks. The more current flows, the more heat is produced. If the machine runs too long at the limit, the electronics overheat: the thermal protection kicks in (the “over-temperature” light comes on), and in the worst case, the machine takes permanent damage.
The relationship is important: Higher current means lower duty cycle. A machine that has 100% duty cycle at 150 A might only manage 30% at 250 A. The percentage always applies only to the specific current stated.
What that means for you:
• Thin sheet, short welds: You're taking breaks anyway — the duty cycle is almost always enough.
• Thick plate, long welds, fill passes: Here the machine runs continuously. Check whether the duty cycle at your working current is enough for continuous operation.
• Continuous load in production: If the machine is under load all day, choose one that's generously oversized or water-cooled — then it stays in the safe zone.
The golden rule: Better to get a machine one size bigger than one that's constantly at the thermal limit. An overloaded machine not only annoys you with shutdowns — it dies sooner.
Why modern machines are so powerful yet compact is covered in the article .