Liquid Metal
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- Essex, UK
I was wrong about the weco discovery machines.
They don't have independent AC.
What they call extra fusion is an increase of DC- from 0%(DC+ and DC- is equal) to 80%(DC+ stays the same and DC- is 80% higher than at 0%).
Seems youre over-complicating it a bit. Asymmetric AC welding is exactly as @richard has said above.
For arguments sake youre welding 6mm fillets and want to get into it and off the mark nice and fast to try not to oversaturate the part with heat.
So you might set up as......
You set your frequency (ie 60hz)
Then set your AC balance (ie 60%DCEN and 40% DCEP)
Those settings would at highish amperages say 250amps would start to muller a tungsten after a while, so you change the EN and EP values of the current cycle so that you have 250amps on the EN side but drop to 100amps on the EP side.
That would still give great penetration, but would give better cleaning action than ising traditional setup, because the current spends a fraction longer in the EP side of the wave but at a lower apmerage which extends tungsten life and guves the torch an easier time too.
How it comes across to me....
Try and visualise the wave drawn onto a graph on paper.
Amps gives height of each wave, frquency governs how many cycles a second, balance gives the amount of time on each side of the wave. But the wave at its highest and lowest points are going to be the same height above and below the "median" point ,ie zero volts and amps.
What seperate EP and EN amperage controls do, in effect, is gove you the option to use exactly the same wave shape drawn on tbe graph, yet you are able to move the "median line" up and down on the graph.
I think also now, there have been a couple of manufacturers that have taken it one step further, so that the shape of each side of the AC cycle you can choose the shape of the wave between traditional sinewave, squarewave, triangular, or trapezoid (i think its called ie a triangle with a flattened top) waves. So you could have a square EN side giving maximum time at maximum amperage, and a sinewave EP side giving a softer cleaning action.