Genny for a Mig, what size ?

[W.olly]

Hi all, ok some may have seen my problem with needing to weld a base plate on a Narrow Boat, plate is 6mm mild steel, no wall i have power wise is single phase 3 pin domestic socket, so not much good.

So i am thinking getting a genny to run a 3 phase mig, 250-300amp.

What size genny will i need to run one?

Asking as a chap has one for me thats a 250amp 3 phase. I could hire a genny instead of buying as i know it would cost a fortune to buy one.

cheers all

wolly

 

[CompoSimmonite]

Why not hire a portable welder ? The type like this -
http://www.hss.com/g/55726/200amp-Mobile-Petrol.html
Stick is probably going to be better than MIG for such thick metal anyway in such a situation

Paul H

 

[Jim Davey]

We hire out small 200 amp DC petrol welder/gennys that would be suitable for this work for between £37.00 and £50.00 per week depending on what you have. (I'm not trying to sell or promote my service, the OP is in Manchester, but to give him and idea, around these parts it costs around £100.00+ a week to hire a 8-10KVA genny, which will be what you want to power a 250amp mig)

 

[wheresmejumper]

it will have the power consumption on the data plate,on the back of the welder.
then double that to find what size genny you need

 

[W.olly]

I have just got these pics of the 3 phase i have been offered,not sure if its anygood but i will post pics in the other thread i started.


which part is the correct Kva

 

[octo0072000]

looks like 8.5 Kva on the mig so 16Kva genny not sure on the laws on 3 phase

 

[W.olly]

looks like 8.5 Kva on the mig so 16Kva genny not sure on the laws on 3 phase

Christ i need a mobile power station then lol

What do you mean about Laws? Dont tell me theres laws about using a genny?

 

[octo0072000]

Christ i need a mobile power station then lol

What do you mean about Laws? Dont tell me theres laws about using a genny?

No not laws
on single phase they reckon a mig will need double the Kva
for the start up inrush of currant on a jenny
not sure on three phase if the same law applies or not whether it needs less Kva or more Kva

 

[W.olly]

I have been looking at welder generator setups, i have been seeing they vary from £500-$800 for a old second hand one of the 200amp range but Arc not Mig, not that it matters now really, these are giving 5Kva.

So am i correct in thinking a 6-7Kva Genny would run the 250amp 3phase mig i am looking at? aslong as it was a 3phase genny that is.

To make it easier i would sell my welder i have and a bit towards to get a genset type thing.

 

[dannyp]

small gennys are crap.

you need plenty of spare KVA when running one welder of a genorator it not such a problem with meany welders.

10kva may do it, as your ater the big welder for duity cycel rather than output as you'll be working overhead

personal i allways err on the side of overkill, id be looking to buy a 20 -25 kw diesel, then id ether sell it after or find work for it. but there again i'm often called a nutter esp when it turn up with the powerstation


actualy scrap everything i say, seem all posts have been delited out the other thread anyway

 

[the snooper]

So am i correct in thinking a 6-7Kva Genny would run the 250amp 3phase mig i am looking at? aslong as it was a 3phase genny that is.

I don't think it would run it

a standard domestic socket supplies a little over 3000 watts which is your 13 amp however the mig draws much more on start up and lets say the mig is 150amp, run the welder flat out it will blow the fuse so the 13 amp is not enough, ive tried a 150amp mig on a 5kva genny low amps it welds ok turn it up and no good, the 5kva genny cant supply enough current on demand, a 13 amp socket will supply far more then the 5kva genny can.
add to the fact if the genny you get has an avr and you try to draw far to much power from it chances are the avr will just blow leaving no power output from the genny

 

[dannyp]

IMO AVR is a waste of time the magic smoke dosent stay in it very long. the older transformenr based kit is far less fussy about specifics of supply, as long as there is PLENTY OF POWER avalible the voltage and frequency can be somewhere near ish.

also bigger genorators are more stabel anyway

 

[the snooper]

also bigger genorators are more stabel anyway

yeah due to the mass of the engine and alternator spinning it takes more upset the rythem

 

[W.olly]

actualy scrap everything i say, seem all posts have been delited out the other thread anyway

which posts were they then mate?




I take it the mobile 200amp/220amp welder sets/Genset types are no good for this then.


So i need a big genny for the 3ph 250amp 8.5Kva mig i have found, without getting to technical please...AVR? Its all new to me this power consumption thing.

What size genny should i look for then so i dont blow the thing.

cheers guys

wolly

 

[the snooper]

Automatic Voltage Regulation, I would imagine that an engine driver welder would be the best option as you will know for sure its up to the job

 

[Jim Davey]

Like I said, you'll be fine on an 8-10 kva as long as you're not planning to run flat out for extended periods. The recommending double rule applies more to inverter powered welders as they are much more prone to damage from under/over voltage/current. Traditional transformer/rectifier welders are much more tolerant to use on generators (the generator is the part that's at risk though if you push your luck too far)
If you do give the generator a good 'workout' be sure to run it for 5-10 minutes at high speed with no load to allow the cooling fan to draw the heat out of the windings, last thing you want to do is give a genny a roasting then just switch it off the second you finish with it (same applies to welding sets, never switch one while its hot if the fan is still running)

 

[Robotstar5]

(same applies to welding sets, never switch one while its hot if the fan is still running)

The rate our production welders worked at, the sets never warmed up!

 

[Jim Davey]

The rate our production welders worked at, the sets never warmed up!

For production work I always try and get people to buy a set that won't be trying to hard. I learned that trick years ago, if you want to weld all day, get some serious extra capacity. I had a client doing vehicle body production, most of it was work below 3mm mild steel, but it was all day, 6 days a week. They had 30 or so ancient Fronius 350 migs and all I ever had to do was was blow them out and change a contactor once in a blue moon. There's a lot to be said for using hammers to crack walnuts.

 

[dannyp]

sledgehammers to crack wallnuts is the best way.

if you end up stuck i have a big genny here than can be borrowed, would have to ask for a deposit on it. it's an ex hospital standby unit, old and bomb proof but on the downside it's open frame so quite loud compared to the supersilents you get now.

the other issue is moveing well towing it, i recon it must weigh in at around 2000kg so needs a reasonable tow car/ truck

but there will be no shortage of power, 125 KVA cont i've had it running a lot of lights and 3 big migs spraying 1.2mm wire . just might be to much overkill tho

 

[W.olly]

sledgehammers to crack wallnuts is the best way.

if you end up stuck i have a big genny here than can be borrowed, would have to ask for a deposit on it. it's an ex hospital standby unit, old and bomb proof but on the downside it's open frame so quite loud compared to the supersilents you get now.

the other issue is moveing well towing it, i recon it must weigh in at around 2000kg so needs a reasonable tow car/ truck

but there will be no shortage of power, 125 KVA cont i've had it running a lot of lights and 3 big migs spraying 1.2mm wire . just might be to much overkill tho

Danny, that is some power, is it a back up for the town you live in lol.

I have the car and a trailer to move something that big, and its a very nice gesture mate, i mite take you up on it, what deposit would you be looking at, need to keep my options open here.

cheers kida

wolly