Hello guys I could use some input on a device I'm building.
I'm building a plasma cutter powered by an alternator I have 120 v three phase coming from the alternator.
I need to step up the voltage to start the arc like 400 volts
I could use a transformer but I was thinking I would like to build a circuit to do it.
Any help would be nice thanks.

 

My guess is your transformer is operating on 60 Hz and is capable of some pretty high amperage output.

In all honesty I'd rectify one phase of the source down to 12V or so then use something separate to create the starting arc. Actually, pulsing the ignition coil off a car wouldn't be a bad place to start, my guess is they'd generate a hot enough spark to get the plasma going.

 

I think we're going to need a Moderator or two to look at this before proceeding.

Plasma cutters by their very nature are pretty dangerous. Building one is not something that an inexperienced hobbyist should attempt, as death is a very possible outcome.

 

Hello,

As SgtWookie already said: plasma cutters can be really dangerous.
There are high voltages and currents involved.
It is not so easy for an amateur to make it real safe.

Bertus