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arc welders at home

Postby richie-elec » Tue Oct 21, 2008 12:12 pm

Can anyonye tell me what is maximum amps i can use for standard home electrics as i want to buy and arc welder and use it in garage. The options i have in arc welders are 30-110 amps or 40-150 amp arc welders both input voltage of 230/1 and open circuit volts are 48.
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Postby ericmark » Tue Oct 21, 2008 6:03 pm

What comes out must go in so start with voltage 25 volt plus 1 volt per 25 amp means at 150 amp 31 volt at run so around 5kw raise this to 200 amp and now 7kw and I am not including losses so 32 amp supply for a 200 amp machine. This would be on a D type MCB and would likely blow the incoming fuse from time to time.
Using inverters rather than transformers removes the need for D type MCB and removes the inrush problem and also the problems with blowing main incoming fuse. A 100A is max continuous with an inverter but for short runs up to 150 amp can be used on a 13A fuse. As a result the norm is a 150A inverter on a 16A plug although should be 125A on 16A plug one will normally get away with 150A and a 13A to 16A adaptor for where 16A is not available and again inverters will normally run on this. But transformers forget it about 75A on a transformer is Max which is too small for any rod able to do any use full welding on 13A.
Since inverters are also lighter to lug around they are really the only answer if you want to weld at home.
Anything over 150A you need a motor driven welding set.
In theory 500A = 100A input with no losses which is size of incoming fuse in practice no way would the fuse hold.
If nothing else was used in the house assuming 100A supply a 300A inverter is about the max you could use. This would draw around the 63A at 230V
Next is affect on the supply the spikes off a transformer could upset any computers on same supply and the waveform distortion caused by inverters may also affect TV, Hi-Fi’s etc not only for you but also every third house in the street.
To use a welder every so often may be accepted but not on a regular basis. You may also need some power factor correction.

Postby sparx » Tue Oct 21, 2008 7:41 pm

Not to detract in any way from Ericmarks excellent maths I can say that I have run my arc welder from my house supply to my workshop for the last 35 years without many problems.
It is rated for 130A continuous/160A short time.
For most jobs I have rarely needed to go much over 90A & only occasionally blown the 13A plug fuse.
I then installed a 16A blue industrial socket as used for caravans/generators etc. and the matching plug on welder.
The supply to workshop comes via a 2.5mm2 Pyro fed from a 30A type 2 MCB in my house consumer unit which has a 30mA rcd main switch which I have tripped on odd occasions when striking-up.
Only complaint from 'senior Management' is the lights flicker sometimes!
As Ericmark says the maths don't add up as conditions change during use,
eg 110A X 48V = 5,280 va / 230V = 22.96A on strike, but as soon as arc struck gives shorted output so secondary volts drop off rapidly to maybe as low as 24V , then 110A X 24v = 2640va / 230V = 11.5A!
So forgetting my dodgy maths(please), ask yourself do you really need to weld that thickness of metal?
I can weld heavy angle iron brackets etc. with less & what about a Mig/Tig ?
regards SPARX
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Postby ericmark » Wed Oct 22, 2008 3:31 pm

As sparx says a 150A inverter does seem to work well at home. But again I must point out huge difference between a welding inverter and welding transformer. And an inverter is well worth the extra money.

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