Welder Puzzle

[gumboot]

Hi all

My son recently bought a Powercraft electric arc welder made by Woolf Tools.

The machine has a rating of 40 to 160 amps and the instruction booklet mentions that the welder cannot be exceed a current of 65 amps when connected to a standard domestic mains supply via a standard 3-pin plug. Higher currents require a direct connection with the supply presumably directly into the ring-main. This is probably the reason why the machine came without a fitted plug.

What I'd like to know is how they calculate this 65 amp figure. There's no indication of the welding voltage on the rating plate of the appliance. I'd like to know how many amps the machine uses when set to 65 amps. For example, if it used 8 odd amps at this amperage as long as the machine didn't draw more than 13amps from the mains via the plugtop and fuse, this 65 amp might rise by a few more amps. How do i work this out?

Thanks

[Disco Fever]

Plug it in and see how long it lasts on a standard 13 amp fuse while the welder is set at 100 amps or use a 16 amp ceeform type plug and socket but it musted be backed up by a 16 amp fuse or a 16 amp type C MCB....

[buildersmate]

Presumably you appreciate that there is a transformer in there that is shifting the mains 240v down to a few volts (say 6v for arguments sake), with a corresponding rise in current available (a multiplier of about 40 using my figure).
So 65A at the output is likely to draw say a couple of amps from the mains supply.