Welder current draw

[RainbowsParticipant @rainbows]

Looking at getting a new fancy inverter welder to replace the big heavy transformer welder I have.

200A – £69

160A – £77

130A – £75

Heard I could probably get up to 180A with an inverter using just a 13A plug assuming I don't do it for too long at a time. Have done 130A my transformer welder so confident that would work.

If I buy the 200A model and don't turn it above 180A will it draw less current compared to if it were on 200A? My gut feeling is that it will draw less but when on my oil cooled welder not matter what setting it will pop 13A fuses within a few seconds. Probably due to the more primitive electronics.

[RainbowsParticipant @rainbows]

[Joseph Noci 1Participant @josephnoci1]

Hi there,

Generally, inverter power supplies are more efficient than the cheap 50Hz transformer welders, so, yes, you should be able to get more weld amps for the same mains current, BUT, only a little more..maybe 10% to 15%..

The losses in the 'poor' quality laminations in the transformer core of the 50Hz welder are not that high and neither are the coil winding losses, even if the windings are aluminium, as many seem to be these days.

Ignoring the efficiency difference, and even assuming a 100% efficient inverter supply, lets look at what the 220v mains would have to provide. The welder has a high open-circuit voltage ( 50 to 70 volts), to enable the initial start of the arc. This then drops to a level required to maintain that arc, at that amperage, and that voltage varies according to the required weld current, a constant current source. Typically:

@ 60A weld current, 1.6mm welding rod ,ARC volts approx = 21volts = approx 6amps from 220V mains

@ 100A weld current, 2mm welding rod ,ARC volts approx = 26volts = approx 11amps from 220V mains

@ 150A weld current, 3mm welding rod ,ARC volts approx = 30volts = approx 20amps from 220V mains

@ 250A weld current, 4mm welding rod ,ARC volts approx = 39volts = approx 55amps from 220V mains

No free lunch, even with an inverter supply…

But you do get nice control of the arc and amps! And the machine is so small and light.

regards

Joe

[Mark RandParticipant @markrand96270]

It should be ok. However today I was doing some TIG welding, in the shed, with my 200A multi-process set at 100A. Somehow, I not only managed to weld its own power switch on, but I also welded the mains switch on when using that instead of the built-in one. Oddly enough, the 13A fuse in the plug is perfectly ok. I intend to fit a Commando plug and suitable 20A circuit for the welders, but it's a round-tuit job.

The 32A circuit I had in the garage for my oil-cooled welder is now in use for SWMBO's pottery kiln.

[Nicholas FarrParticipant @nicholasfarr14254]

Hi, you will not get much over 3kw continuously through a 13A fuse, therefore you will get less than 3kw of power output from your welder continuously, whatever welder you have. Inverters are quite a bit more efficient than transformers, but they will still sink a portion of the power coming in, they cannot generate any extra power. The answer to your question is, yes it will draw less from the mains the lower the amps are that you are welding with, but the inrush when striking the arc, maybe almost the same. A lot depends upon the actual type and make of electrodes you are welding with as the dropping characteristics can vary from one make to another and also the minimum OCV needed to strike the arc may be different. The actual type of joint and thickness of the material can have different affects also. The best option would be to hook it up to a 16A or better still a 32A supply using those blue plugs and sockets.

Regards Nick.

P.S. One thing about some inverters is, if you don't have enough available power for them to boot-up so to speak, then you won't get a very controllable arc to weld with.

Edited By Nicholas Farr on 14/08/2017 23:07:05

[RainbowsParticipant @rainbows]

Ended up with a 250A one. Time to buy a very big plug. 9.5KVA, if voltage is 230V then thats 41A. Never sure if 230 vs 240v these days.

Going to upgrade wiring to 32A. 63A is the next step up but then plug and socket costs goes from £6 to £60. Might just not go past 200A.

[Brian WoodParticipant @brianwood45127]

Rainbows,

You should also be sure your cabling is up to the demand you are going to be putting through it. Ideally you should be supplying the welder through 6 mm twin and earth and use an appropriate circuit breaker at the consumer unit.

Regards

Brian

[MuzzerParticipant @muzzer]

One key feature to look for in an inverter welder if you are bothered about efficiency is a Power Factor Corrector (PFC) front end. This ensures that the input load presented to the mains network is resistive. So if you genuinely have a sinusoidal waveform, the current will be too. The result is that the RMS (resistive heating) current is minimised for a given input power.

Many of the cheapie inverters just run from rectified mains, giving a very lumpy mains current – this results in a high RMS value, which is what plugs and fuses and wiring are bothered about. There seem to be a few low end products fitted with PFCs, such as these.

However, if you are expecting to pay under £100, you probably just need to spend a few quid on wiring in a larger plug and socket. I have a 300A TIG welder that has no PFC and is pretty low on electrical efficiency. The input current exceeds 60A on full whack but so what – as long as the wiring and MCB are correctly rated, no harm is done.

Murray

PS – for reference my mains typically measures 240-245V these days.

Edited By Muzzer on 15/08/2017 11:18:15

[RainbowsParticipant @rainbows]

So my shiny welder came today. On it is a 16A euro plug. Be fun to see how well that would cope with 40A.

It happily laid 2 rods at 160A while on a 13A fuse. Was going to see how high I could get before the fuse went but 4mm was the largest electrode on hand.

[Andrew TinsleyParticipant @andrewtinsley63637]

I have an Oxford oil cooled welder and it seems to work pretty well. I assume Inverters are an electronic form of arc welder, what advantage do they have over such ancient technology as an Oxford oil cooled welder?

Andrew.

[Joseph Noci 1Participant @josephnoci1]

Andrew, simply put, they are much lighter and most are able to give reasonably stepless welding current control. Also some offer higher frequency weld in AC mode ( higher than your transformer type @ 50Hz) which helps concentrate the weld heat more finely.

Today a 100amp inverter welder might weigh around 2kg…

Joe

[Nicholas FarrParticipant @nicholasfarr14254]

Hi Andrew, this **LINK** has a simple explanation, there is a nice block diagram half way down, which helps understand the explanation.

Regards Nick.

[RainbowsParticipant @rainbows]

The new welder I can pick up one handed without any effort. My oil cooled one in the garage needs a sack truck to move about, can barely lift it at all.

Also this new one makes a DC arc where I think all the oil ones are AC. Allows simple TIG welding and I think it can make some electrodes work better? As mentioned you can also fine tune to the amp how much current you use.

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