The duty cycle of a welder is the percentage of time that a machine can operate safely within a certain period of time and at a given amperage.
The Weldforce WF-205MST multi-function welder, for instance, has a duty cycle of 200 amps at 30%. Simply put, this means the machine will operate at 200 amps for 3 minutes within a 3-minute time frame.
For the 7 remaining minutes, the machine will change to thermal overload so it can cool down.