what is duty cycle of welding machine?

By Stephan (***)

Date 02-25-2008 15:22

windson,

I'm sure your question will cause an avalanche of great replies.

Thus only for a very first view:

http://books.google.com/books?id=jNxCxwp2fHoC&pg=PA345&lpg=PA345&dq=duty+cycle+%2B+welding&source=web&ots=aEU0nH5NO_&sig=cFOqvdKjzcb_Jl7IbZRtIwaVoWM#PPA345,M1

Best regards,
Stephan

By js55

Date 02-25-2008 16:16

Duty cycle is a NEMA (National Electrical Manufacturers Association) measure of power source overheating resistance (or better, current carrying capacity-perhaps some of our more electrically inclined can put it better) based upon a 10 minute cycle. If your power source has a 60% duty cycle that means it will run 6 minutes at the rated current without overheating. If its 100% duty cycle it will run the full 10 minutes.
From this, duty cycle curves are generated that are available in most power source operators manuals.

By windson Date 02-26-2008 09:36 Edited 02-26-2008 09:52

Are there any equation to calculate duty cycle of a 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?

By Stephan (***)

Date 02-26-2008 10:28

windson,

although I am tempted to follow Shanes explanation :-), I have nonetheless quickly prepared a paper based on data coming from the AWS Welding Handbook "Welding Processes Part 1".

See also the attached pdf.

As for the: "...then it need 12 minutes and 35 seconds to cool down and can resume welding...", please note what js55 has posted. The entire cycle time for creating the data is always fixed at 10 minutes!

Best regards,
Stephan

Attachment: CalculationofDutyCycleotherthanratedoutputs.pdf (20k)

By DaveBoyer (*****)

Date 02-27-2008 06:13

Windson, You would be much further ahead using the duty cycle chart from the manufacturer if possible. The high temp protection built into a machine is a last resort safety feature, and it is not absolutly acurately tied in to the designed duty cycle of the machine.

By Shane Feder (****)

Date 02-26-2008 09:56

js55,
And I always thought the duty cycle was measured by the length of time a welder took to smoke a cigarette while waiting for his welder to cool down.LOL !!!
Regards,
Shane

By js55

Date 02-27-2008 14:45

Dave's right. I would recommend just using the graphs provided in the owners manuals.
If you wish to create calcs for acedemic purposes this is fine, and undoubtedly informative. But I think you'll find that getting this precise will have no value on the shop floor. There are too many variables. For example dust. Duty cycle graphs are created from new machines. Not to mentione generalized form new machines. As dust accumulates on the components of the power source the power source will have a tendency to overheat faster and there goes your low tolerance calcualtions.
How do you distinguish between dust overheating, or just plain individual machine variances, and running 10 minutes or 9 minutes 30 seconds?
The time and money you spend trying to dial in this application would be better spent on a bigger machine.