Duty cycle?

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What is a duty cycle on a machine? like what does it mean if it has a 40 percent duty cycle, ect?
Reply:The standard meaning is that it can be used that percentage of Ten Minutes and must idle the rest of the time to cool. Here it could be used 4 minutes and would need 6 minutes to cool. The duty cycle does usually change with changing output.
Reply:Another thing, duty cycle is based on maximum output of the machine and will typically increase as the output is reduced.  So a machine that has a duty cycle of 60% at 350 amps may have a 100% duty cycle at say 275 amps.
Reply:I have seen a formula for determining duty cycles at different outputs, given a machines known duty cycle at a certain output, dont remember it though.  Would this be fairly reliable or just a guestamation?A few of my toys !LinuxMintManjaroMiller Roughneck 2E Lincoln WeldPak 100HTP MTS 160 Chicago Electric 80amp Inverter   Victor O/A
Reply:For these purposes duty cycle is merely how many minutes out of a continuous ten minute period that a machine may operate at any stated load without any risk of damage. That is safe operating times at various loads before a cool down period should be allowed.
Reply:Originally Posted by EyesolatorAnother thing, duty cycle is based on maximum output of the machine and will typically increase as the output is reduced.  So a machine that has a duty cycle of 60% at 350 amps may have a 100% duty cycle at say 275 amps.
Reply:This sounds like a google question.  A lot of my own questions were well answered by searching them in google.  http://en.wikipedia.org/wiki/Duty_cycleMiller 330 a/bp water cooledI believe in gun control, I hold my gun with two hands.  If you want to know why, click here.Buy American or bye America.
Reply:Found it!!!Ta=To(Io/Ia)2Io=rated ampsIa=desired ampsTo=rated duty cycleTa-desired duty cycleEx: 60%@200amps60%(200/125)2=15460%(200/180)2=74A few of my toys !LinuxMintManjaroMiller Roughneck 2E Lincoln WeldPak 100HTP MTS 160 Chicago Electric 80amp Inverter   Victor O/A
Reply:If you ever hit the duty cycle on your machine, don't shut it off.Let it stay on, so that the fans can cool it down.Instead of shutting it off... so the fans don't run
Reply:Originally Posted by smawgmaw  Found it!!!Ta=To(Io/Ia)2Io=rated ampsIa=desired ampsTo=rated duty cycleTa-desired duty cycleEx: 60%@200amps60%(200/125)2=15460%(200/180)2=74
Reply:Originally Posted by nctoxCan you tell me where you got, or show a link to that formula?  It didn't seem to work when I tried it.  Thanks..........
Reply:Originally Posted by BoostinjdmBetter do some more research...  Duty cycle is stated for a given output, not always maximum.
Reply:And now a duty cycle story!  We had a Hyertherm 1250 plasma power source on our cutting machine which had a 60% at it's maximum output of 80 amps with three phase power.  We used it primarily to cut weld coupons.  At the very least it would run for 30 seconds stop and move to another pierce for about three seconds and repeat the process. Hour after hour yet it never shut down or melted down and ran fine for years.  If you do the math it ran way more the six minutes in a ten minute period with a very short cool down period.  Or would it have had to run for six + minutes straight to exceed the duty cycle?  Interesting or maybe a no brainer?
Reply:Another tidbit.....Duty cycles are not set in stone.  Some companies underate thier equipment, and others overate thier equipment.  The better brands are usually underated to ensure a long life and a customer will always be happy if the machine performs better than advertised.  Cheaper brands over rate thier equipment so they can compete on paper with the big boys.My name's not Jim....
Reply:Originally Posted by BoostinjdmAnother tidbit.....Duty cycles are not set in stone.  Some companies underate thier equipment, and others overate thier equipment.  The better brands are usually underated to ensure a long life and a customer will always be happy if the machine performs better than advertised.  Cheaper brands over rate thier equipment so they can compete on paper with the big boys.
Reply:Originally Posted by EyesolatorAnd now a duty cycle story!  We had a Hyertherm 1250 plasma power source on our cutting machine which had a 60% at it's maximum output of 80 amps with three phase power.  We used it primarily to cut weld coupons.  At the very least it would run for 30 seconds stop and move to another pierce for about three seconds and repeat the process. Hour after hour yet it never shut down or melted down and ran fine for years.  If you do the math it ran way more the six minutes in a ten minute period with a very short cool down period.  Or would it have had to run for six + minutes straight to exceed the duty cycle?  Interesting or maybe a no brainer?
Reply:The temp that the welder/duty cycle was tested in also makes a difference.  I think the norm is 40.deg CThats how some cheaper machines can set their duty cycles higher ( test in a lower room temp  20.deg C )My Kemppi 4200 has a rated duty cycle of 400amps/100% -  420amps/70% at 40.deg CLast edited by LarryO; 10-17-2009 at 02:48 AM.
Reply:There are a lot of variables to determine duty cycle in a plasma cutter. First....you must cut in an environment with the ambient air temp (Hypertherm units are rated at 104 degrees F) until the core temperature of the IGBT switching device and the inductors is achieved....then increase the arc voltage by cutting thicler material or creating a longer arc.A plasma system that has been sitting in a 70 degree room will appear to have a higher duty cycle than one that has been operating. A plasma system cutting thin gauge material at full output amperage will have a higher duty cycle than one that is cutting thicker material at the same amperage.I know that the Hypertherm units are all conservatively rated...and that the test criteria used at the Hyperther R&D labs is extremely demanding...I have observed this kind of torture testing for years.Hypertherm also tests competitive systems to see how they stack up. We have yet to find a low cost import unit that even comes close to its manufacturers duty cycle ratings...in fact most of them have component failures (FET's or IGBT's) before they reach their advertised duty cycle. These units are probably acceptable for occasional use...but will not stand up to high duty cycle use.A properly designed plasma power supply will not self destruct when duty cycle is exceeded...rather, it will shut off output power while keeping the cooling fan active...until a lower , safe core temp is achieved.Jim
Reply:Originally Posted by smawgmawTo be honest, I remember getting it from a welding manual years ago but dont remember which one.  I posted it from a sheet of printer paper I had written it on that was saved away with other things.  If I find the manual from which it came I will post the info.  I retried the formular and it worked for me.  When you multiply the squared result by the rated duty cycle, dont use percent, just whole number, I think.