Square Wave

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I've heard a lot about square wave in the past.  I got to use a Miller equiped with it while at school years ago.  But, I really couldn't tell any difference.  Anybody weld with one a lot that can really explain it to me?
Reply:When doing AC TIG, the modern technnologies (square wave, and a pile of other trademarked similar features) change polarity fast enough the arc doesn't extinguish, so the need for continuous AC goes away. Also, most of the 'square wave' machines have more features and adjustments and more desirable arc quality than older machines, like better balance control, better control of current on each polarity (giving better control over  total energy put into the weld) than oldr rectified machines, and better AC frequency control than older machines.You won't see any benefits of 'square wave' welding DC, though some of the features that come with the machine may be nice
Reply:My TA 185 has NO hi freq to start the arc.  On AC It uses High energy sparks like the coil on your car.  Once the arc is established, it needs no further assistance to keep going.  The new square wave inverters have lots of adjustments that do help in a small way.DavidReal world weldin.  When I grow up I want to be a tig weldor.
Reply:Enlpck gave a good quick explanantion, though he did mean to say the need for continuous high-frequency (HF) goes away.When a sine wave crosses the zero, it does so relatively slowly, so the arc has time to go out and must be reestablished as it slowly climbs again.  But a square wave is practically full positive and full negative, without the gentle crossing.  The arc doesn't have time to go out between polarities.Also, this means that for the same peak amperage, there is a much greater area under the square "curve" so you get more heat input overall.
Reply:a sine wave output smoothly transitions between -ve and +ve. during transition the amperage is lower and around the cross over (-ve to +ve) virtually zero (hence the reason for continous HF- keep the arc going).the time spent at the peak of each 'cycle' is pretty short making it (relativly) inefficientsquare wave gives more time at the peak of each cycle and less time between peaks. because the switch between -ve and +ve is so fast HF is only needed to initiate the arc. basically it's more efficient.now consider the +ve cycle used to remove aluminium oxide. because more time is spent at peak with square wave, less +ve balance is needed for a given amount of cleaning. less time spent +ve means more time spent -ve. result is you can weld faster for a given amperagewith square wave the frequency of the arc can also be altered. switching from +ve to -ve more quickly tightens the arc- great for fillet welds
Reply:Interesting, thanks guys.  That brings back a lot of E & M memories from school that I haven't dusted off in a while.  I can't tell if my machine is squarewave or not.  It's a 1997 model Miller Syncrowave 351.
Reply:It's Squarewave.
Reply:Whoops. thanks for the correction. Originally Posted by MAC702Enlpck gave a good quick explanantion, though he did mean to say the need for continuous high-frequency (HF) goes away.