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# Thread: what is duty cycle of welding machine?

1. Junior Member
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## what is duty cycle of welding machine?

where can i study detail about duty cycle of welding machine? (exp: book, magazine....)

are there any equation to calculate duty cycle of welding machine?

for example... a machine can welding for 5 minutes and 45 seconds (power supply cut off by thermostat at this time), then it need 12 minutes and 35 seconds to cool down and can resume welding. how to calculate duty cycle of this welding machine?

2. duty cycle is based on a 10 minuit cycle. so if its at 40% duty cycle at 260 amps, then you can weld for 4 minuets strait then cool for 6 .keep in mind thats full on trigger pulled for 4 minuets, not start, stop move and start again in the 4 minuets. so take into account setup and moving from one weld to another as cooling time. it tends to stretch out the duty cycle.
is that what you are looking for ??

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## Simplify those numbers just a bit

From your example, we'll call it 6 on and 12 off. 18 total. 6 divided by 18 is .33, or 33% duty cycle. But, that's not a 10 minute period. I'm no expert, but, I don't think the 10 minute period is strictly required when discussing duty cycle. I think I've seen it expressed for an hour, for example.

Originally Posted by windson
for example... a machine can welding for 5 minutes and 45 seconds (power supply cut off by thermostat at this time), then it need 12 minutes and 35 seconds to cool down and can resume welding. how to calculate duty cycle of this welding machine?

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Originally Posted by EdZep
From your example, we'll call it 6 on and 12 off. 18 total. 6 divided by 18 is .33, or 33% duty cycle. But, that's not a 10 minute period. I'm no expert, but, I don't think the 10 minute period is strictly required when discussing duty cycle. I think I've seen it expressed for an hour, for example.
yes, i agree too..10 minute period was not strictly required...
do u have any prove how to calculate the duty cycle?
exp: equation from handbook , journal or others source...

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fun4now already covered the meaning of duty cycle, including the normal reference to 10 minute period. All I did was basic math.

And, regarding that 10 minute period, I think it's just an easy device for expressing several minutes on/off out of 10 as a percent. So, I think that my calculated 33% is just as meaningful, even though it's based on a longer period.

Oh, alright. Here it is out of a welding textbook, "Welding Technology Fundamentals," by William Bowditch et. al:

The duty cycle is a rating that indicates how long a welding machine can be used at its maximum output current without damaging it. Duty cycle is based on a ten-minute time period. A welding machine with a 60% duty cycle can be used at its maximum rated output current for six out of every ten minutes. The welding machine may overheat if the duty cycle is exceeded. At lower current settings, the duty cycle may be increased and the power source used for a longer period of time.
By that definition, though, Miller should have provided a duty cycle rating for my MM180, at an output of 180 Amps. Instead, the duty cycle is stated as 30% at 135 Amps.

Originally Posted by windson
yes, i agree too..10 minute period was not strictly required...
do u have any prove how to calculate the duty cycle?
exp: equation from handbook , journal or others source...

6. all the manufacturers post a mid range duty cycle, suppose it makes the welder look better. or it could have some other reason, i don't know ??but if you look in your owners manual it should show you what it is at 180amp's but i suspect it will be low. keep in mind 2 minuets of solid weld time is a long bead.

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Oh, yeah, the manual! Says MM180 duty cycle is 15% at 180 Amps. Gets to 100% at 60 Amps.

Originally Posted by fun4now
all the manufacturers post a mid range duty cycle, suppose it makes the welder look better. or it could have some other reason, i don't know ??but if you look in your owners manual it should show you what it is at 180amp's but i suspect it will be low. keep in mind 2 minuets of solid weld time is a long bead.

8. The only problem with calculating a duty cycle over a different period, especially a longer one is it is no longer accurate. For instance, if duty cylce is calculated over an hour, the 50% @ 200 amps would mean that a welder could put out 200 amps for 30 minutes straight. This is a lot different than the same machine running for 5 minutes straight before having a chance to cool. Duty cycles can't be added together, that is you can's run the afformentioned machine for 15 minutes, then let it cool for another 15.

9. Senior Member
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You're making sense. I've been thinking about this, as well. But, what are we to say about windson's 6 on, 12 off scenario? Machine can weld for 6 minutes, but requires much more than 4 minutes to cool. Such a machine can't exist? Or, more likely, the run time is artificially adjusted downward to such point that it can cool in the remainder of 10 minutes? 3 on, 6 off (keeping to whole numbers, making nearly 10) would still be 33%, but indicates the machine can only run 3 minutes straight. But, possibly 40% would be more accurate, since the machine hasn't been pushed to it's limit, and could still cool enough in 6 minutes.

So, this business of calculating duty cycle down to a 10-minute period is really the heart of windson's question. How DO manufacturers do that?

As a practical complication, I noted that the MM180 manual says that if the thermal overload gets thrown due to exceeding duty cycle, you're supposed to wait 15 minutes before further welding. Which would mess up the usable concept of duty cycle. And/or, points out that you're much better off grazing the duty cycle limit, than exceeding it.

Originally Posted by shorerider16
The only problem with calculating a duty cycle over a different period, especially a longer one is it is no longer accurate. For instance, if duty cylce is calculated over an hour, the 50% @ 200 amps would mean that a welder could put out 200 amps for 30 minutes straight. This is a lot different than the same machine running for 5 minutes straight before having a chance to cool. Duty cycles can't be added together, that is you can's run the afformentioned machine for 15 minutes, then let it cool for another 15.

10. Once you screw up bad enuff to make the machine kick off the whole duty cycle time counting thing is thrown out the window!!
Then you better take a little more than 15 minutes to decide what the heck yer gonna do different, like get a bigger machine or weld less time but one thing is for sure you just crossed a line there you don't want to go back over.
I don't think duty cycle is something you can interput very loosely...you got some leeway but you can't change the general meaning.

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