Duty cycle is the amount of time a welder will weld or a cutter will cut in a given time frame at given amperage.  Simple explanation is, 20% duty cycle means it can be used for 2 minutes out of 10 at a given amperage setting,  30% -3 minurtes etc.  These are just guidelines, each individual unit may weld or cut a little more or less in same time frame.  Most spec sheets have a scale to show duty cycle scale from high to low settings. Most equipment is rated at 2/3 to 3/4 of it's maximum output.  When you are using less amps the duty cycle goes up, more amperage it goes down.  Ambient temperature and humidity can have some affect on the duty cycle.  Machine will shut down when it exceeds it's duty cycle, and come back on line when cooled. To improve or maintain duty cycle, run at minimum amps required for the job, keep fan area clean and have inside cleaned by repair center or yourself with power cord unplugged occasionally.  There are thermal couples in the unit that sense when it is getting too hot that shut off the unit until cooled. I hope this simple explanation helps, there are more technical explanations available on the internet. Please specify yes or no below if you found this guide helpful.  

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