How it works
Arcuracy mathDuty cycle needed = minutes of welding in each 10 × 10, as a percentage. A machine is listed when one of its maker-stated duty cycle points is at least that percentage at your amps or higher. Minutes of 10 = duty cycle ÷ 10 (Miller).
What it meansDuty cycle is expressed over a 10-minute period: a 30% rating means about 3 minutes of welding, then 7 to cool. Running past it trips the machine's thermal overload or, on machines without one, risks damage.
LimitsOnly the maker's own rating points are used. A machine usually runs longer at lower amps than its rated point, but we don't estimate figures a maker hasn't published; the manual or rating plate may list more points. A hot shop lowers real duty cycle.
Questions welders ask
What does 30% duty cycle at 90 amps mean?
About 3 minutes of welding at 90 A in every 10 minutes, then 7 minutes for the machine to cool.
Is a higher duty cycle better?
Only if you weld long beads. For short beads and tacking, a lower rating at your amps can be enough.
Why do makers give duty cycle at different amps?
Because it changes with output: the same machine runs a larger share of time at lower amps.
What happens if I exceed the duty cycle?
Most machines stop on thermal overload until they cool. Repeatedly running past the rating can shorten the machine's life.