[Shop-talk] Yet another TIG Welder question

[Douglas Braun]

Yes,  I googled "homemade tig welder" or something like that, and I
saw a description of
somebody's project to build an inverter module.  It looked more
complex and expensive than
the rest of the welder's circuitry.

Doug

On Fri, Jan 7, 2011 at 10:37 PM, David Scheidt <dmscheidt at gmail.com> wrote:
> On Fri, Jan 7, 2011 at 9:04 PM, Douglas Braun <doug at dougbraun.com> wrote:
>> There seem to be some Chinese AC-DC welders starting at about $1000, but
>> that's not much less than the price of a Miller Diversion 165.
>>
>> I don't understand why AC-DC welders are so much more expensive (and
heavier)
>> than Dc-only machines.  I was looking at the Diversion schematic, and the
>> AC capability is supplied by an electronic inverter switch between
>> the Dc power supply and the gun.  The inverter is basically 4 big
transistors
>> that alternately connect the positive and negative output to the gun
>> and work connections.
>
> Those are four big, high-power IGBTs.  Last time I looked, they cost
> about 200 bucks a pop.  That's low volume pricing; nobody making
> welders is paying anything like that, but it's still a big chunck of
> the price.
>
> --
> David Scheidt
> dmscheidt at gmail.com