# Inverter power consumption question

• posted
I know that inverters are much more efficient with power from
the mains than transformer-based machines.
What does the power curve look like?
A TA185TSW draws 1.6A @ no load and 38A @ rated load (160A @ 26V).
Does the power pulled from the mains go up in a linear fashion
between no load and rated load conditions?
I ask because I am trying to get an idea of how many welding amps
I can pull before triping a 20A breaker.
I've been practicing on ~ 0.070" mild steel with the machine set
at 90 amps. My guess would be that I can probably do this all day
without tripping the breaker.
I've got a 30A extension cord, but SWMBO sometimes gets miffed
when I monopolize the dryer outlet...
Thoughts?
Jeff Dantzler
• posted
The switching losses should be somewhat fixed and the only linier loss would be IR (copper loss) in the magnetics, which in high freq inverters, arn't that much, so I would think you can assume farily linier power consumption (minus the fixed 1.6 Amps for control electronics etc).
When you say "30 Amp extension cord", what exactally do you mean? - a 10 gauge cord ?
Also remember, that residential breakers are time and heat rated. So for a 20 Amp breaker, you can draw 25 Amps for some period of time, and 30 Amps for even a shorter time etc. (This is the design theory with the Lincoln SP-135's)
So 1/2 of 160Amps (@38 Amps) is 80 Amps which puts you at 19 Amps input, so at 90 Amps output, you'd be slightly over 20 Amps, which, will "probably" be ok, but it would depend on the breaker itself, how it heats up, its age, etc. I had an air compressor with this situation where I was right on the edge, and it used to trip every now and then, but simply replacing the breaker with the identical size (just new) at Home Depot for like \$6 solved the problem). However, I'm not recommending that being on the edge like this is "ok", just saying that sometimes its unavoidable. Which leads me to my next logical question - just what kind of 220 outlet do you have (for a dryer) that has a 20 Amp breaker ?? Most all dryers are 30-Amp breakers on 10 gauge wire. (could your dryer run be 12 gague wire?) If you find that the dryer run is actually 10 gauge, thats simple - drive to Home Depot, spend \$6 and up the breaker to 30 Amps. But please make sure that it is indeed 10 gauge wire from breaker to recepticle, and this included crawing thru the attic if need be - (it should be a home run)
Hope this helps! - waiting for a T/A 185STW myself (They tell me next Tuesday).
• posted
Thanks. That's what I had suspected.
I built a cord around 30' of 10 gauge SJ flexible cable with a NEMA 6-50 receptacle on one end and a dryer plug on the other. It was originally for my 175 amp MIG box.
My dryer has appropriately sized wire for the 30 amp receptacle. That's not the problem though...
If I hog the dryer outlet, SWMBO sometimes gets upset that she can't dry a load. And I have to deal with a cord running out the laundry room over to my detached garage.
I have a 240V / 20A receptacle in the garage. I made up an adaptor that allows me to plug the inverter in there, with the knowledge that I will not be able to run the machine hard. I don't plan to weld anything thicker than about 3/32".
When I get a chance, I plan to run a proper 100 amp feeder to the garage.
Got any good resources on running an overhead feeder? I've got code books, but need specifics on what parts to buy (type of conduit, masthead, cable securing devices, strain reliefs, etc.)
You'll like the 185TSW a lot, I suspect. It's a great machine at a great price--especially with the kit.
Jeff Dantzler
• posted
So this 240V / 20A circuit/recepticle is wired to the breaker box with 12-gauge wire then ?
Just search Google - some local power company's have very detailed and helpfull info on their websites on how a new/additional service feeder should look.
I hope so, I just wonder what kind of torch head they will be giving me. Looking at the on-line manual, I also see that it only has a max of 160 Amps on stick. (which is fine, its just not the full 185 at any duty cycle). I raely weld over 110-120 Amps anyhow.
• posted
Yes. 12 gauge is fine for 20 amps. If I pull too much current, the breaker will trip, but nothing will catch on fire.
I'll look harder.
Mine shipped with a CK17. Came with std collets/bodies for 0.040", 1/16", & 3/32" along with one thoriated tungsten of each size. I picked up gas lenses in these sizes as well as a box of lanthanated tungstens of each size. Also a selection of steel, stainless, aluminum, and hastelloy filler rods and a leather cover for the torch since gas and power are separate lines.
I look forward to your report on the reliability of the 185TSW from the service guy you spoke with. FYI, the guys at B&R said they have not had any problems with machines they have sold.
Cheers,
JLD
• posted
It is a bit more complicated than that. The power more or less goes up in a linear fashion (or the machine would get very hot at some settings...), but the cos phi may not. Some inverters add cos phi correction to allow to use less A for the same output, but I doubt that the correction is always active (it is only needed for high A).
Yes: measure. You can get a clamp to measure 200 A for about 20\$ today. Ask your SWMBO to help you (she should be motivated) and have her read the current for different settings of the welding machine.
Note that if the breaker does not trip after, say, half a minute, it simply means that you draw less current than its rating.
OTOH, decent power cables are always a good idea.
• posted
What is cos phi?
I agree. I spent about \$100 on my cord for the 30A receptacle and another \$20 on the adaptor. Once I get more power out to my shop, this will all be moot. For now I am working on some foundation repairs and need to get them finished first.
Thanks,
Jeff
• posted
Cos phi is cosine of the angle phi where the angle phi is normally used to represent the phase angle between the real (consumed) power/current and the the total power/current. This is also called the power factor. The part of the total power that is not real is returned to the grid and in a residential or small industrial setting doesn't cost you anything since your power meter takes into account the phase angle as well. However, your breaker and wires have to be able to handle the total power/current not just the real component. So if you have a real component of 18A and a total of 25A your breaker and wire has to be sized for the 25A which usually is more money. The power grid supplying you have to be sized similarly as well and that's why large factories spend money to correct their power factor, usually with capacitors, since they will get charged a penalty for a poor power factor.
By applying capacitors you can adjust the power factor so the real and total are close to the same. Unfortunately the capacitor size at low welding currents is not the same as high welding currents so the manufacturers use a compromise size.
Billh
• posted
Thanks for the explanation, Bill.
Cheers-Jeff

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