"Phil" bravely wrote to "All" (24 Sep 05 20:44:12)
--- on the heady topic of " AC Switch or contactor"

Ph From: "Phil"
Ph Xref: core-easynews sci.electronics.repair:343036

Ph Have been welding for about 30 years, have joined metal from .010 " to
Ph 2" thick , worked as certified Aircraft welder for several years,
Ph mostly TIG or GTAW and Electron Beam, typical aircraft tubular
Ph assembly would be either .035 or .049 wall thickness, electron beam of
Ph Titanium would be on the order of .25" thick, welding light gauge 4130
Ph or 308 Stainless would require very little D.C.to join, if one were to
Ph join two pieces of .75" ,6061-T6 Alum., you would need A.C. with the
Ph square wave skewed to nearly 70% negative with 75% Helium 25% Argon
Ph gas and approx. 400 amp. at the torch , this load will pop a 100 amp.
Ph breaker in a heartbeat, and no I have never done any ship building,
Ph thanks for your interest. Dr. Phil "quietguy"


Assuming the arc voltage is around 50 to 80 volts then 400 amps at the
electrodes could indeed have surges exceeding 100 amps from the 240
volt supply.

What immediately comes to mind is to use a bank of triacs in parallel
or a single BIG f***er. I know they make 400 amp and even 1,000 amp
triacs though these are industrial types not available at the corner
diode convenience store.

A*s*i*m*o*v

.... Of course it's grounded! ...watch, ...YEEEEEAAAAAAAAHHHHHHHH!!!!