Rated Ouput vs. Current Range

[oldbab]

Can anyone fill me in on the differences here?

Also, am looking for good on-line welding guides - have a few now, but can't get enough!!!

thanks

[cope]

A given machine might weld from 20-210 amps, but it is rated at maybe 60% duty cycle @160 amps. At maximum output the duty cycle might drop to 20%. In this case the machine would put out an honest 210 amps, but only for 2 minutes out of q10 where as it will put out 160 amps for 6 minutes out of 10. Some machines have a 20% duty cycle at all ranges and some are as high as 100% at lower output.

[oldbab]

Thanks for the clarification, Cope.

[Mike W]

oldbab, there is some good info here;

http://www.esabna.com/EUWeb/MIG_handbook/592mig4_13.htm

[TRG-42]

Rated Output

This rating is done in accordance to NEMA standards to make any comparisons between machines / brands fair.

This rating is made up of 3 numbers ( more if you count ambient conditions like temp )

1. Rated output . This is generally the amps that a machine can provide into load bank ( kinda like a dyno for welders ) at a given VOLTAGE and DUTY CYCLE

2. Volts at rated output. This is the tricky one. A manufacturer could choose to do this test at a voltage of 26. Another would do it at 28 volts . All things equal ( rated output and duty cycle ) the machine whose rating was done at 28 volts has slightly more power

This is important depending on process being used. For example if you are burning a self shieled flat position wire such as E70T-4 ( Fabshield 4 or NS-3M ) these wires run at typically 30+ volts. So when you look at the rating of an engine drive such as a Traiblazer 302 where its 300 amps at 25 arc volts , chances are you won't be able to squeeze the 300 amps 100% duty cycle rating when using this particular wire

3. Duty Cycle. - much has been discussed on this. The key points to remember :
- If you are comparing machines, should try to use the same DC rating

- Duty cycle can be quoted for different outputs. For example, a Deltaweld 302 is rated at 300 amps 100%DC but about 380amps at 60% duty cycle. You can see this chart in their brochure

- Manufacturers generally use 100% DC rating in their brochures for industrial style machines. They tend to use 60 and / or 40 % for the light industrial and anywhere from 20 to 30% for their smaller MIGs

- Generally speaking because a machine has a *** amp rating at 40% duty cycle does NOT mean the machine is not capable of operating at higher than 40% duty cycle. It can, but obviously at a lower than *** amp rating

Conclusion : Rated output is the amp rating of a welder at a given volts and duty cycle . This is used for comparisons are choosing welders

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Output Range

Output range is the min to max amps a welder can output . This CANNOT be predicted from the rated output. Rated output has actually little to do with the max output of a welder

The things that determine max output

1. Design of the transformer / switching devices in the machine

2. Design criteria of the welder

Max output generally determined at design stage and limited by circuit boards

3. Software . Newer welders such as the inveters or choppers have their output limited by software

It is often incorrect to assume that a machine with a higher rated output has higher output range

For example, a Ranger 305 has a rating of 300 amps @100% DC . Max amps out of this machine is about 305 amps . A Classic 300D has a rating of 300 amps at 60% and 250 amps at 100% DC . One would assume the Ranger has more power.............BUT in reality the Classic 300 is capable of outputting over 400 amps ! and therefore has a higher output range
Go figure !

Where you see a large difference between rated output and max output are generator welders ( the "grey coloured " Lincolns such as the Classics or SAE's ) , inverter pulse MIG machines ( need very high peak currents for pulse GMAW ), or large transformer style industrial power supplies ( the big 600 amp and above machines ) that are used for carbon arc gouging

Hope this doens't confuse you more !

[oldbab]

I'll have to reread a bit, . Thanks for the info.