welding advice please....tech electrical info.

[oberonspacefruit]

OK.

Got this genny.

On the plate it says 7.7KW

Ive got this crappy arc welder.

Now, today, ive welded a couple of dots, but the genny has really laboured when arcing up. I know you get a power surge when first turning on an appliance, which is creating the massive power draw.

I want to buy a mig, but dont want to get one too powerful for the genny.
I have no option of mains electrics.

Ive been told that you need 4kw genny- minimum for a welder.

the genny, as i said is 7.7 so should be ok.

So, the question is, how much is this arc welder drawing (it will weld on the genny, its just that it makes it really work hard), so i can work out what amp mig set to get.

Any technical dudes got a clue?

 

[Wedg1e]

It does say 'I1 Max 21A' which, bearing in mind it also depicts a 10A fuse, would suggest that its nominal rating is somewhere under 2.4kW but that instantaneous peaks could go as high as 5kW!
The 7.7kW you mention would appear to be the power of the engine (about 5.6HP?), not the electrical capability. I'd deduce from the 5500 model number that it may be a 5.5kW, but can't be certain.

 

[oberonspacefruit]

Ah, I see. Having said that, even if it is 5.5kw output, it should be able to easily handle the 2.4 welder, even if it peaked at 5kw?

perhaps its not operating at its full output?

 

[rich74310]

Also depends on how old the genny is could be the electrical side of the generator braking down alittle over time.similiar to an alternator going on a car.

Rich

 

[TBC]

A standalone generator that will run a stick welder even a small one, would be physically at least twice the size as the one you have there.
Same is true of mig welder, the better of the range would be an inverter welder (more efficient power conversions means less pull on the powersupply) or genset which is not confined to the 50hz so smaller engines with bigger welding amps less power conversions. Or choose a petrol motor welder, they tend to whistle as you weld due to the hi~z, but are often only the size of a mains fed 200amp welder .

If your set on a generator you need a high duty cycle 60%+ and at least 10KVA.

10KVA = 8KW output (will run .8 and .6 wire but you can still tell it lacks power over 4mm material!
5.5KVA = 4.4KW output (ok to boil a kettle but won't weld more than a tack!)

go here hxxp://www.dieselserviceandsupply.com/Power_Calculator.aspx to do your generator power conversions. (substitute the xx in the link before pasting to your browser)

hope this helps.

 

[oberonspacefruit]

Can you recommend an invertor that would work with this genny? Its only going to be used for car bodywork.

 

[oberonspacefruit]

Oh, forgot to add to the above post, Ive done arc welding, mig welding and tig welding, but the tig was a big industrial set. I really dont like using the arcwelder with car body work.
Just had a quick look at the tig/arc inverter sets on youtube, and apart from how it starts up, it seems similar to the welding method ive used before.

I dont want to waste money buying somthing that wont work, Ive already shelled out 250 for two generators, and rather that spend another 200 on a mig set, or an inverter welder, Id like to have half an idea of what may work with this genny. otherwise, its a case of sell the lot, and farm the work out to somone else, which I am loathe to do as every welding job ive had done so far has been an absolute waste of time, and has made the car worse, rather than better.

 

[GeorgeB]

Ive got this crappy arc welder.

You said it! Personally, I don't agree. I'd take the view that if the arc welder is working as designed it should be fully fit for purpose.

But is it working properly? There's another recent thread where an arc welder is tripping the power supply. I suggest you need to try out the welder on a normal mains power supply and compare the performance with what you get when using the generator. If you've already tried that, does the arc welder normally work OK (on the mains)?

 

[oberonspacefruit]

yep. the arc welder normally works fine on mains supply.

With the genny, it seems to suck all the power out of it.

I dont like arc welding though, it seems messy in comparison to mig, for body stuff, although perhaps thats my technique.

Thing is i was told in another thread that I would need at least 4kva, to weld with, which is why I bought this genny in the first place, on the strength of that advice.

http://www.mig-welding.co.uk/forum/showthread.php?t=9544

True, i thought it would be 7kva according to the plate, but even still, 5.5 is more that I was told I'd need.

Plus I was told that someone had run a 130 mig from a 5kva with no problems.

Its just a pain when I'm spending money that I could do with not wasting, as Im on a limited budget to get the car sorted, If the set up was never going to work in the first place.

I think im just going to hire the smallest mig I can find, an see how it performs with the genny.

 

[darrylp]

what exactly are you welding on this car ?

chassis ? panels ?

i've used my 90amp mig on a 2.4kw genny. startup was slow, but was fine once the arc formed. th genny didnt like it too much, as its speed was allover the place, but it did an hours worth of welding,and the genny and welder are both in use still.

 

[malcolm]

Those that know about generators tend to say get one that can output more than twice what the welder needs.

Why are you thinking about an ARC welder for bodywork? Way to hot for the job - if you aren't fussy about the strength or sealing it may be possible to do the job with an arc welder with multiple splodges, grind down and splodge again but it's not nice.

A MIG with shielding gas for that. But get yourself one that costs more than £100. Really cheap eBay efforts just don't work and I've seen owners resorting to their arc welders instead and completely missing the point. Clarke 90 is the cheapest we recommend on the forum (not the 85) and you will need to use it with shielding gas for a nice experience welding bodywork.

The nasty cheapo arc welders have a big current draw. Half reasonable MIG on a low setting (even a high setting) won't have anything near the current requirements.