Induction heater - Aluminium

Discussion in 'General Electronics Chat' started by gpugelni, Feb 13, 2008.

  1. gpugelni

    Thread Starter New Member

    Sep 6, 2007
    4
    0
    Hi all,

    I was build 200khz half bridge inverter (cca 1kW), which have variable matching inductance, tank capacitor and work coil (10mm Cu) + lot of snubbers.So for iron(magnetic) stuff it works ok, (it heat iron very well at resonance), but I have problem with aluminium. It wont heat it (it become only worm 50°C), and inverter have big problems with "ringing" and self destruction :).
    I suppose that 1kW power is enough for melt some small piece of material but there is happening somethnig and I can't findout what...

    I know that aluminium is highly conductiv, and it do not have magnetic characteristics like iron (probabbly is problem there).

    Thus someone know which frequency to use for melting aluminium with inductive heater?

    Thanks in advance,
    gpugelni
     
  2. Dave

    Retired Moderator

    Nov 17, 2003
    6,960
    144
    The iron heats up better than the aluminium because the alternating magnetic field creates hysteresis-losses as the ferro-magnetic crystals in the iron are magnetised and demagnetised. This is added to the eddy-current losses typical of induction heating having a compounding heating effect.

    I am no expert on induction heating (I have only briefly come across the technology), but given for aluminium melting you are looking at maximising eddy-current losses, you are pretty much constrained to one of the ISM bands below 30kHz.

    Dave
     
  3. thingmaker3

    Retired Moderator

    May 16, 2005
    5,072
    6
    Aluminum is also a better conductor than iron, so will heat up less.

    Try getting your work coil wrapped as closely as possible around your piece to be heated. Insulate (thermally) as well.
     
  4. gpugelni

    Thread Starter New Member

    Sep 6, 2007
    4
    0
    Thanks for tips Dave and thingmaker3.
    Do you maybe know for some good book about induction heating?

    Regards
     
  5. Dave

    Retired Moderator

    Nov 17, 2003
    6,960
    144
    Yes, "Conduction and Induction Heating" by E.J. Davies. It is the academic and industry standard text on this subject.

    You may also want to look at Metaxas and Meredith's 1983 book "Industrial Microwave Heating" as a supplement to some of the theory (although I must warn you it doesn't deal directly with induction heating and I certainly wouldn't recommend buying it for your purposes, but it might help if you can get access to it).

    Dave
     
  6. abdullahshawky

    New Member

    Mar 26, 2008
    1
    0
    dear Sir,

    You said that you have done a working heater for magnetic materials like iron and so on

    please post the schematic as soon as you can because i need to do one and i cant

    please add all the details on circuit and coil design because i am in egypt and finding books and data are really hard

    yours
    abdullah
     
  7. Dave

    Retired Moderator

    Nov 17, 2003
    6,960
    144
    Given the work that goes into designing an induction heater, I very much doubt you will get someone handing you their IP. The above suggested book should give you a starting point for learning about the technology. There are also quite a few home-made induction heaters on the Internet - have a look at them.

    Dave
     
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