MIG Welding, CC Inductor, and bypass thereof

Ignoramus20083 · 2007-05-14T16:46:11+00:00

This is in regards to an old Hobart CyberTIG welder that I modified byputting in a new microcontroller that I programmed in BASIC. Basically because I have a separate SCR controller, and separatemodule for controlling it, I can program it to do anything I want, tosupply any voltage and any current, within my power limits, of course.So it is basicallly an arbitrary DC power supply, with a few extrarelays that control high frequency arc starting and gas valve. This thing works just fine in constant current mode, letting me stickweld as well as TIG weld. Note that it has a big inductor that helps with constant currentwelding.Now that I am done with CC mode welding, I started exploring MIGwelding, which requires constant voltage. Found a LN-25 wirefeed uniton Craigslist. The issue at hand is that the output of my welder goes through a largeinductor that is helpful in CC mode, but counterproductive for wirefeed welding. This inductor weighs perhaps 50 lbs. (?)So, for nice wire feed welding, I would need to bypass it. I see twoways of doing it: 1) Make a simple bypass circuit using a big contactor and big cable(to be turned on when MIG welding is being done).2) Instead of bypassing the inductor, install a capacitor that would"cancel out" the effect of the inductor. Can that be done at all, is this an insane idea or not? My hope isthat it would be done with a smaller "work envelope", utilizingsmaller wires and a smallish capacitor, instead of a bulky contactorand big wire, etc. Any thoughts on bypassing the inductor?thanksi

May 14, 2007 21 Replies

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Grant Erwin 18 years ago

If you add a capacitor, you are making an LC filter which may strongly affect your waveform. When you want a nice rising edge of current, you might get a sinusoidal pulse followed by ringing. I think the capacitor idea might be doable but it would require a ton of electrical engineering.

Grant

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Tim Williams 18 years ago

Short it out, or leave it. Choke input filters have great voltage regulation under load BTW.

What limits current upstream of the choke? That's your bigger problem.

Tim

-- Deep Fryer: A very philosophical monk. Website @

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microcontroller as a switch to

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