A couple of months ago I asked if anyone knew why a Lincoln buzz box arc welder was rated at 20% duty cycle at every setting. I got the best kind of reassurance that it wasn't anything to worry about (everybody who answered knew what they were talking about and had first hand experience to back it up---you can't ask for more than that.)Still, it left me curious about a few things related to how welders work. I also have a Hobart 235/160 AC/DC with infinite range. The drawing in the manual shows a shunt moving through the winding as you turn the handle to set the amperage. The manual also shows a graph of the duty cycle for both kinds of current. At full capacity AC or DC the duty cycle is 20%. But the 100% duty cycle point is 100A AC and 65A DC. Here are my questions. How do welders with settings instead of infinite range work? I've seen old Lincoln and Forney welders that had outlets (I've heard them called taps) for each setting---holes where the cable, or cables, plugged in. Isn't duty cycle a function of heat buildup? Doesn't a welder that has a 15% duty cycle at full capacity necessarily have a greater duty cycle at half that capacity, whether the manufacturer says so or not? Why do the cheapest arc welders always have low duty cycles; what is it about their construction that makes this so? Why is the DC of an AC/DC SMAW welder always about 70% of the AC, and why do you have to use more AC amps than DC amps for the same rod? These aren't the questions that keep me awake nights, just ones that probably have reasonable answers. Thanks, Stan
| 
