What size generator do i need for the following

[Red-berry]

What size generator do i need to run a 100amp ark welder and what size generator do i need to run a 100amp mig welder please

[ChuckFickens]

about a 23KW one for both!

[ChuckFickens]

Ah..... is 100amp the mains current or the welding current?

Find out what the mains current is and multiply by 230 to get the watts.

[rojash]

Dunno much about them, but according to this site:

http://www.mig-welding.co.uk/buying.htm

You can run a mig welder of up to 150 amps from a 32 amp supply.
Which makes around 7.5 KVa

[ChuckFickens]

OK... about 10amps for a 100 amp welder... 2300 watts, about a 3KW generator.

[Red-berry]

For a 40 - 140 amp welder its open circuit volts is 48, av.input power kw is 3.5, does that mean i need at least a 4 kw generator to run the welder

[HowardKennitby]

That is a difficult question.
It is always best to have a little power in reserve. It depends on how quickly the generator can respond to the load. If it is a modern generator in good order you should be OK at 4kW.
I would try to test any that you intend buying and also make sure the shop knows it is for powering a welder.

[BRIGHT SPARK]

I would choose at least a 5kva if your input is 3.5kw.

[Red-berry]

Thanks everyone for your help, have gone for a 5kva