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Duty Cycle, what do the numbers mean

Thursday, 19th March 2020
Graham (Tech Advisor)
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If you prefer to watch video than read, the following link will take you to a video we’ve produced that explains Duty Cycle.

Understanding Duty Cycle

“Duty Cycle” is probably the least understood of the specification data published for any type of Mig Welder, Tig Welder or Plasma Cutter.  Essentially it’s a set of figures to indicate how long a welder will run for before it gets too hot and the thermal overload mechanism shuts the machine off for some cool off time.

However, as there are a number of variables (ambient temperature and power setting for example), Duty Cycle data is more for comparison of different welders.

Manufacturers establish the Duty Cycle figures by putting the machine in a controlled temperature environment and running it at a specific output until it overheats and shuts off.  The time this takes is recorded and presented as a percentage of a work period.

The European Union definition of a Work Period is 10 minutes.

A typical Duty Cycle will be shown as follows:

30% @ 200amps at 40°C

So what do the numbers mean?

30% is the percentage of the work period the machine operated for during the test.  In this example, the machine operated for 30% of the 10 Minute work period, which is 3 minutes.

200amps is the power output that the machine was set to for the test.

40°C was the ambient temperature the the machine was tested in.

As mentioned earlier, this data is notional because of the variables.

For example, in the UK you’re unlikely to ever be welding in a 40°C ambient temperature! (good luck if you are ? )  If its Winter it may be below 10°C in your workshop, so the machine will be cooled by air that is substantially below the test temperature of 40°C so the welder will clearly run for longer than 3 minutes!

If you were to set the machine to an output below 200amps it will weld for longer, set it higher than 200amps and it will overheat sooner.

So the Duty Cycle figure is a guide only.  But as I said earlier great for comparison and making sure you get the right machine for the job!

Hope this helps

Please let me know what you thought of this article by leaving a comment.  Don’t worry, your email address won’t be added to a database or shared and you won’t receive any unsolicited email.

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