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How to not short circuiting an induction heating coil

  1. Oct 14, 2008 #1
    how to not short circuit an induction heating coil

    Just wondering about induction heating coils and how to not short circuit one.

    basically, if i hook up one end of the coil to the positive and one end to the negative (DC) i assume that i will be short circuiting the connection and also creating a crude resistance heater at the same time - which is not what i want to do.

    so, how do i avoid this and properly create a induction heating coil that doesn't really (itself) heat up but produces the desired magnetic field that heats the material in the center.

    just for the example let's say that i'm using 1/2" copper tubing for the coil and it has 4 turns of an approximately 4" inside diameter and i intend to heat iron scrap in a small ceramic crucible so that i can cast it into 'something'.

    thanks

    EDIT: I just read that induction coils are AC ... so then could I simply hook up each end of the coil to the bare wires from an extension cord and have it work? or am I gonna fry something / myself ??

    thanks
     
    Last edited: Oct 14, 2008
  2. jcsd
  3. Oct 14, 2008 #2

    Mech_Engineer

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    Induction heating is a very deep subject, and sinsce it's obvious you don't know anything about it you'd better not try making one.

    Basic background of inductive heating: http://en.wikipedia.org/wiki/Induction_heating

    Induction heaters use a large amount of power (5kw and up), typically paired with high current and high frequencies (hundreds of amps, thousands or even hundreds of thousands of hertz). Short circuiting an extension cord won't do anything excpet put you in danger and blow your circuit breaker.
     
  4. Oct 14, 2008 #3
    and blowing myself to kingdom come is, understandably, what i wish to avoid.
    i've gone through the wiki but i have not seen anything on it in terms of the required components to build one and / or how to determine components for larger / more powerful upscaling of a small one.
    so without a background in electronics i'm at a sort of stand still as to building one until i can find some reliable information that will provide me with a step-by-step of how to build even a simple (low powered) one.
    if perhaps someone has a link to a good tutorial that would help to explain the requirements (not just an 'overview' of the basic components) then it would be greatly appreciated.
    although, i see in my future a requirement to take a formal course(s) in electronics so that i can learn more so that i can build / do what i want to build / do
    thanks
     
  5. Oct 15, 2008 #4

    Mech_Engineer

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    I very seriously doubt you will be able to design and build your own induction heating system baesd on what I'm getting from your posts. Induction heating requires complex circuit design to carefully control frequency, voltage, and current. In addition you have to keep an eye on things like the temperature of the inductive coil, and temperature control of the system itself.
     
  6. Oct 15, 2008 #5
    Thanks for the feedback.
    Personally, I don't believe in boundaries. I think that I can achieve anything I put my mind to.
    Although you obviously have more experience in this field than I do (which is practically no experience at all) that doesn't mean that I am not capable of learning.
    My goal may be lofty but it is certainly not insurmountable.
    Again, the feedback is appreciated but I have to say that not knowing something right now won't stop me from learning new information in the future.
    Everyone starts with no knowledge and then progressively increases in knowledge and understanding - otherwise the world would still be flat.
    All the best
     
  7. Oct 15, 2008 #6

    Mech_Engineer

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    I have some practical experience in theory of operation of inductive heating systems, as well as first-hand operating experience of a 10kW inductive heating unit, so I at very least have a grasp of what it is you're proposing. Why not just purchase an off-the-shelf inductive heating system?

    Something like this little 3kW device:
    http://www.superiorinduction.com/HF induction machines/SI-3KWHF.pdf

    If you are really deadset on building your own, your best bet will be to get an Electrical Engineering degree with a few technical electives in heat transfer and thermodynamics. Induction heating is a heavy mixing of several engineering disciplines, so just reading a few simple books can't really get you the in-depth applied engineering knowledge that is required... You will at very least need to learn everything you can about control systems, power modulation, current and voltage control, heat transfer, electromagnetic fields and eddy currents, etc.
     
    Last edited: Oct 16, 2008
  8. Oct 15, 2008 #7
    well, that just takes all the fun out of it.
    building something myself forces me to learn something about it and especially how to fix it when it's broken / when I break it.
    I don't want to build stuff cuz I need it ... just cuz I find it interesting.
    Thanks
     
  9. Oct 15, 2008 #8
    hmm, maybe you could tinker with something small? maybe learn to build an oscillator, then drive a power transistor to pump a bit of high frequency current through some magnet wire and see if you can transfer heat to an empty soup can or something. but dude's got a point, you sound like you're very far away from even experimenting with a 100W circuit.
     
  10. Oct 15, 2008 #9
    You're correct

    which is exactly why I'm posting here ... to gather information that will help me to make 'informed' decisions ... to learn from others

    asking questions is one of the ways that I have chosen to begin learning.

    I am also reading a lot of online material as well as books from the library.

    I'm talking to friends I know that are actively involved in electronics.

    I'm also experimenting with batteries and small coils and magnets to 'help' create a basic understanding.

    Right now all I'm really after is some understanding of how it all works and what is required to make a simple 'soup can' heater function ... basic understanding that I can draw on later.

    As long as I have a 'working knowledge' of how it all goes together then I can apply that knowledge to something when I'm ready and have a suitable project - like taking over the world (unless pinky & the brain have already done that).

    Maybe I'll make a convection heater for my living room (heat a pipe (susceptor) which heats/warms the air),
    or melt scrap metal to make lawn ornaments,
    or make myself an induction stovetop,
    or make a high-powered passive thermocouple (haha),
    or, or, or ... hard to say right now.

    What I do know is that I want to know and understand the main fundamentals of it and what the basic components are and what they do and what colour they are so that I can sit back and think of 'stuff' that could benefit from it.

    I've found some great 'beginners' books on the subject so I'll keep readin' and I'll keep reading about basic fundamental beginners electronics so I know which end of a diode to point toward my flux capacitor when I plug it straight into my 240 main with my bare wet hands.

    All the best and thank you for the information and opinions.
     
  11. Oct 17, 2008 #10
    Thanks for the info.

    They offer their fuelless info for pay ... so I found 'someone' who already had it to 'borrow' it from and read over.

    Gonna start ripping apart an old tv, microwave, radios and what-not to scavenge 'stuff' off of to start playing with ... also got tons of 14gauge wire left over after re-wiring my house ... so no shortage of stuff to keep me saying 'ooh' and 'ahh'

    Will post results of crude experiments later when I start experimenting with involuntarily electrocuting myself ... lol

    All the best
     
  12. Oct 17, 2008 #11

    russ_watters

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    That was not-very-well-camoflauged spam....
     
  13. Oct 17, 2008 #12
    hmmm ... starting to see the correlation between light, electricity, magnetics and sound ... starting to get more interesting.

    just figured it out that the 'soup can heater' could be built with a rf generator ... wonder if i could mod an old metal detector to do the job?? - worth investigating me thinks

    gonna have to buy an osciliscope thing now i guess eh

    the fun begins!!
     
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