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New Induction Heater circuit with no center tap.

Discussion in 'Electronic Projects Design/Ideas/Reviews' started by gary350, Nov 1, 2016.

  1. shortbus=

    shortbus= Well-Known Member

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    Doesn't seem that way to me. Seems to be fighting to not adapt what you and tcm have been saying. Look how much it took to change from mosfets to IGBT's. Don't think it's sunk in yet that those are high side switches.
     
  2. spec

    spec Well-Known Member Most Helpful Member

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    Useful information about the coil parameters. As said before I agree that increasing the voltage would increase the power, but I think it is wise to start with an isolated +-24V system first and get that working before moving on to anything grander. That would then provide a test bed for further development... gently gently.:cool:

    spec
     
  3. spec

    spec Well-Known Member Most Helpful Member

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    Don't worry, we will get an induction heater working which hopefully will be the basis for future development.:)

    I didn't see anything wrong, in general that is, with Gary's PSU approach- quite neat I thought.:cool:

    spec
     
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  4. dave

    Dave New Member

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  5. tcmtech

    tcmtech Well-Known Member Most Helpful Member

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    That's largely where I am at as well. A practical base circuit running off +- 24 volt rails just comes off as being the simplest to work with given common parts. Also with the adjustable frequency and duty cycle driver circuit tuning it to work best with any coil even remotely close to being right shouldn't be much of a problem.

    Tuning and adjusting the user to function 'sort of well enough to work with' is the biggest challenge and already has me largely played out on the issue. :facepalm:
     
  6. shortbus=

    shortbus= Well-Known Member

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    Just a thinking out loud comment here. I've seen it suggested in this thread to use a switching power supply to power this, isn't that a bad idea? Many things like stepper motors, that switch at frequent and high speeds recommend against the use of switching power supplies and say a linear supply is better, wouldn't that also apply here?
     
  7. spec

    spec Well-Known Member Most Helpful Member

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    I can't think of a problem with SMPs in this application, but it is worth checking this.

    spec
     
  8. tcmtech

    tcmtech Well-Known Member Most Helpful Member

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    Rube Goldberg said he's fine with the concept. :rolleyes:
     
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  9. gary350

    gary350 Well-Known Member

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    I have these diodes. I can not find data on these anywhere. I am guessing they are at least 50 volts or higher and probably 100 or 200 amps. I also have a box of industrial SCRs that I think are 600 amps. I also have about 50 capacitors 47,000. uf 200 vdc i have been saving for a rail gun project.

    [​IMG]

    [​IMG]
     
  10. tcmtech

    tcmtech Well-Known Member Most Helpful Member

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    Those were common in old Linde welders and related power supplies and typically had at minimum 400 volt 300 amp capacity.

    They were made and labeled as a 'proprietary design' which basically meant they could charge 4 - 5 times what their generic standard labeled version sold for.

    I have a bunch of them too. Never have managed to kill one either.

    Yours were made during the 25th week of 1974.
     
  11. spec

    spec Well-Known Member Most Helpful Member

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    They sound like real man's devices.:cool:

    spec
     
  12. tcmtech

    tcmtech Well-Known Member Most Helpful Member

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    Meh. I have a collection of 'Hockey Puck' rectifier diodes and SCR's that make these look like wall wart power supply level components. :cool:

    I think the biggest salvage units I have are well over 2400 amp @ ~2100 volts or something like that. At least 2000+ on both amp and volt ratings anyway. :p
     
  13. spec

    spec Well-Known Member Most Helpful Member

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    Wow:cool:

    The big thing with high power diodes, IGBJs, SCRs, etc is, not only do they increase reliability, but they also give high efficiency because of their low voltage drop, which in itself increases reliability.

    spec
     
  14. tcmtech

    tcmtech Well-Known Member Most Helpful Member

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    I've always been a fan of using them in experimental projects just because they are so dang hard to destroy when you do screw something up! :D

    A 600 volt 50 amp SCR in a TO-247 package will take a line short hit for aobut 1/10th of second before it explodes even if it on a heatsink . Whereas even a basic stud type or mini puck 1600 volt multi hundred amp device without any heatsinks will take out a 240 VAC 100 amp circuit several times back to back without issue. :cool:
     
  15. spec

    spec Well-Known Member Most Helpful Member

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    Now that is what I call real electronic engineering.:p

    As a matter of interest, with 170V DC reverse voltage, what sort of leakage current would you get with those monsters, if the rectifier junction were up at 100 Deg C? If you bought a new one what would the cost be?

    Some 50A automobile alternator diodes I checked years ago leaked around 20mA, or thereabouts, with 20V reverse. I thought the diodes were dud at first.

    spec
     
  16. gary350

    gary350 Well-Known Member

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    I did have 16 hockey puck diodes I salvaged the aluminum heat sinks weigh 15 lbs each. I sold all but 2 they are lost some where in my work shop. I don't know the value someone once told me 800v 800a.

    I found a transformer I can use instead of a MOT EI laminates are too small for more than 100 turns on the primary plus the secondary. The properly designed transformer needs 200 turns on the primary and I have plenty of room for 3 secondary windings. The original transformer is rated 1500w continuous and is large enough for 3500w peak.
     
    Last edited: Nov 24, 2016
  17. tcmtech

    tcmtech Well-Known Member Most Helpful Member

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    I've always been fascinated by the high power electrical and electronics. Anything under a few hundred amps at a few hundred volts just doesn't thrill me any more. :p

    Nearest size SCR's I can find are these at Digikey. http://www.digikey.com/product-deta...ion/VS-ST1230C16K0/VS-ST1230C16K0GI-ND/359264
    1600 volt 1745 amp ~$300 a piece so I have to guess the bigger ones I have would be in the $400 range.

    The ones I got came from a huge DC motor drive that ran a ~1000 - 1200 HP 600 VDC motor for who knows what and I have pulled dozens of other sizes of SCRs, diodes, transistor and IGBT power bricks from other huge devices like VFD's, power conditioners and massive UPS units. A buddy of mine runs a salvage yard so I get to pick through the odd electrical and electronics salvage items they get in when I go and visit so that's where most of it comes from.

    Depending on the alternator diode design some are pretty crappy and others or outstanding. I have bunch of salvaged 24 volt 100+amp Leece Neville commercial alternators and I have done megger tests on them to see what their PIV breakdown voltage was before reconfiguring the windings on one for higher voltage output and they tested at greater than 2 gigaohms on a live 1000 volt megger test. :cool:
    I like using the big Leece Neville alternators for that sort of experimenting being they are typically wound as 2 - 4 parallel windings per phase and configured in a Delta output so reconfiguring one to run at any output voltage up to around 200 VDC unit is pretty easy.
     
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  18. spec

    spec Well-Known Member Most Helpful Member

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    Sounds good. The first move will be to get the PSU sorted.

    spec
     

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