Induction isn't just nice for ferrous

Discussion in 'General foundry chat' started by 3DTOPO, Mar 29, 2021.

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  1. Rudy

    Rudy Copper

    OK, my misunderstanding. I have thought about making a DIY induction inverter (I have an electronic design background) and that is why I took it that direction. As far as a VFD creating the three phase power, it would be possible but inefficient. And I doubt there are very high power VFDs that run on single phase power. For the same reason higher power induction supplies don't typically use single phase power sources.
     
    Rudy, May 7, 2025
    #21
  2. Mburtis

    Mburtis Silver

    Just checked automation direct and they top out at 25hp on a 230v single phase input, 230v 3 phase output. Says 75A on single phase input. Probably still not enough to run a larger furnace.
     
    Mburtis, May 7, 2025
    #22
  3. Al2O3

    Al2O3 Administrator Staff Member Banner Member

    Been a ways down that road too. Would I still want a melt-anything furnace?........sure but I think you'll find that task a bit more challenging than it appears on the surface. Of course, the degree of the challenge can greatly depend upon your desired power level. Like mentioned in the previously linked thread, if you stick with non-ferrous melting the control scheme becomes much simpler. If you only want to melt ounces, the cheap imports available for a couple hundred dollars can be adapted.

    More recently, more economical high power IGBTs have made the task more practical but you still need some big capacitors and power supply to feed the beast. The first order or priority me was ability to melt up to 60lbs of aluminum. To cut to the chase, for me it was going to be 25kw minimum, and preferably 50kw. At that power level, no matter how you slice it, the real issue is starting with low voltage residential single-phase power and the impact that has on downstream design and component cost. Sure you can step it up, but the price of that transformer is quite high and you still have single phase power. People have repurposed welders for a DC PS but at that power level and 100% duty, that's not a cheap welder.

    You really should have a cylindrical induction duty crucible for each alloy you want to melt, and in my desired sizes, that wasn't cheap either......it becomes a $ ball rolling down hill.

    In the end, for reasons above and a number of others stated in the linked thread, I built a 22kw resistive electric furnace for a couple hundred dollars and it was absolutely the right decision for my needs. I had more in the drop cord and high-power switch gear but that was going to be the same for any machine of that power level.....just the price of entry.

    Best,
    Kelly
     
    Al2O3, May 8, 2025
    #23
  4. Rudy

    Rudy Copper

    Maybe I understated my abilities s bit too much. Until my retirement three years ago I was the senior engineer for twenty five years at an electronics manufacturing company designing a variety of electronic products, mainly power electronics. Twelve years before that at another smaller electronics manufacturer.

    I totally agree with you that designing an induction unit would be very challenging, even with the lab I had. My desire was only to melt non-ferrous metals , at most about a liter. I already had suitable capacitors that we wrote off from a discontinued product. I had power semiconductors from a VFD project that got cancelled. (I warned them that we would not be cost effective, but they hire an engineer with VFD background to come up with the design anyway)

    Even with my background and resources I didn't think it was worth the effort to start that personal project. Years ago I built a small electric furnace. I have another two larger ones started (not large) and it is a more practical solution for me.
     
    Rudy, May 8, 2025
    #24
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