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Now this question is out of my own ignorance of the product specifics & my drive to keep the number of equipments streamlined & to a minimum.

See, I want a TIG welder for a long time now & at the back of my head, I've also always wanted an induction heater for forging/heat treating steel. So, in hopes of said minimalism, are TIG welders conducive to being adapted to induction heaters? By that, I take it as given, some need more additional components than others, but is still nonetheless efficient & cheaper than buying a separate welder & induction heater.

I think that the 2 are conducive because TIG welders are current sources & in induction coils, current is what matters. Specifying current, with an upper limit to the voltage as it is in induction heaters is exactly how you do too with TIG welders. I'm not sure about the waveform needed by induction heaters, but mid-range TIG welders can output in sinusoidal, triangle & square. Perhaps one will suit for being an induction heater.

So, am I in the ballpark here?

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    \$\begingroup\$ ”I'm not sure about the waveform needed by induction heaters” Here lies the issue. Your average AC TIG welder is 2-3 orders of magnitude too low in output frequency to make an induction heater. \$\endgroup\$
    – winny
    Commented Nov 13, 2022 at 7:01
  • \$\begingroup\$ Damn it........ \$\endgroup\$ Commented Nov 13, 2022 at 7:04

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I mean...

It's possible, in the same sense that it's possible to run a tractor's PTO into a combine or an electrical generator. You just unhook one and hook up the other, how hard could it be?

But it's not going to be so straightforward unless designed that way -- as a tractor is. Getting there from scratch, is not going to be just tossing parts together and praying that they work. Not at these power levels (a few kW for the welder, perhaps 10s of kW for the heater).

The common aspects of both are the AC input filter, rectifier, PFC (if applicable), inverter*, and some aspects of the controller (for simplicity's sake, let's say it's a PWM VCO like TL494).

*Most likely applicable, but not necessarily. A full-wave forward converter will use a bridge type inverter, but a half-wave will not, along with several other types. General-purpose induction rarely uses anything other than bridge.

After that, the welder requires a DC output, so, a step-down transformer, rectifier, filter, feedback network (for PWM control), and optionally a pulse controller, polarity switch, etc. (to implement pulsed and AC waveform modes).

Whereas the induction heater requires an AC output, so, a matching transformer, optional matching inductor, resonant capacitor, feedback network (for frequency control, optionally PWM as well), and optionally a timer, or a heat profile controller, thermostat, etc.

Both will likely use water cooling, but the induction heater needs it more, due to the higher currents involved.

It is possible to design a system with a modular output network, with attached control, so that one could use the same input stage for induction or welding, as the case may be.

Perhaps with the right output network, they could be chained instead of swapped: the induction heater could operate in a special low-Q mode, feeding an inductor into a rectifier, and all the welder controls stack on top of that. The exact hierarchy is neither here nor there; there is some output hardware, and a lot of control tech, that's used in one mode only.

This is not your average amateur project -- I personally spent many years designing one myself (from scratch), and several years designing another (professionally). (In fact I'm one of the earlier people on the internet to have done so; though that was a long time ago by now, so this is neither here nor there.) And that was with an already extensive background (before formal schooling) in electronics.

These are voltages, and power levels, that can result in real injury, and death. Safe practices can be followed -- as we do in industry -- but it takes experience to understand what to look for in assessing the safety of a situation.

It will be a challenging project. It is certainly not insurmountable, as I and a handful of others (that I know/knew of) can attest. But it is a deep dive into the heart of power electronics and control theory, with a large price of failure if you misstep in the slightest (i.e., at least blowing up a few IGBTs, or worse). The best advice I can give you is to realize that all these issues can be studied at any power level. Learn how to control the system, to safely (non-destructively) handle fault conditions, and design the power switching circuits; then scale up incrementally, in voltage and current respectively, and watch closely for any new behavior (peak voltages or currents, common mode interference, etc.).

Good luck, and enjoy the metalwork in any case -- don't worry, there are plenty of other tools there you will need to make, hehe.

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  • \$\begingroup\$ Are there add-on sub-units/components that you would recommend I acquire first to play with along with the welder? Sort of get the feel of the challenge, without diving deep into power electronics theory territory? \$\endgroup\$ Commented Nov 14, 2022 at 4:26
  • \$\begingroup\$ @TempusNomen Like commercial add-ons? As far as I'm aware there is no such thing. The closest I can think of is, Miller (and maybe a couple others) make mostly welders but also some IHs, but I'm not aware that any are convertible as such. Not without heroic (read: the above) effort I mean. \$\endgroup\$ Commented Nov 14, 2022 at 8:07
  • \$\begingroup\$ At the start, I was hoping it would be closer to simply making resistors & capacitors variable & swapping out for higher frequency transistors & opamps. Seems like I just won't have the time to get knee deep into this. \$\endgroup\$ Commented Nov 14, 2022 at 18:51

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