bulding a meg welder

[turkeybradley]

i plan to buld a mag welder 400 watts . i am using a mosfet to control my wattage . 1 am using 3 , 300 amp 600volt d c mosfets. i plan to put a choke in the out put to the hand control. i am afrade the striking of the arc will cause an inverse current that will damage the mosfets .will the choke prevent the inverce causing damage?

 

[Memmeddu]

i plan to buld a mag welder 400 watts . i am using a mosfet to control my wattage . 1 am using 3 , 300 amp 600volt d c mosfets. i plan to put a choke in the out put to the hand control. i am afrade the striking of the arc will cause an inverse current that will damage the mosfets .will the choke prevent the inverce causing damage?

You need capacitors to prevent that.
Unfortunately I'm not an electronic expert and I can't remember which type you need to use

 

[skotl]

i plan to buld a mag welder 400 watts . i am using a mosfet to control my wattage . 1 am using 3 , 300 amp 600volt d c mosfets. i plan to put a choke in the out put to the hand control. i am afrade the striking of the arc will cause an inverse current that will damage the mosfets .will the choke prevent the inverce causing damage?

Welcome to the forum

There's a few discrepancies in your post which are confusing me: Title says "MEG", post says "MAG" so I don't know whether you mean MIG (presumably with gas) or MMA (arc, with rods)?
The mechanics of MMA are way simpler than with MIG, not needing wire feeders, gas switches etc,

Next, you say 400W - is this output rating? If so, that feels like only somewhere around 80A (which is normally how we describe welder ratings) which doesn't seem very much.

Finally, although it's not a reason not to do it (most of us are tinkerers), why...? With a decent 80A welder available from Amazon at around $75 it seems a lot of effort.
That said, best of luck!

 

[voipio]

Is the indended use of the FETs going to be in linear mode, or switched mode? What sort of power supply is envisaged for the supply to the FETs?