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  1. #1
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    Safety Issue - Ferromagnetic metal under induction cooker

    Recently I noticed an accident that somebody put a stainless steel plate under a portable induction cooker. As a result the plate get heated and the heat melted the enclosure of the induction cooker severely.

    I would like to ask is there any precaution on the product/electronics design on common induction cooker to prevent this case? A thermal fuse under the coil?

    If not, is it possible to put a grounded metal wire mesh at the bottom of the cooker, to shield the magnetic field and prevent it heat up another metal underneath? (Using wire mesh because it will not build up an eddy current to heat up itself)

    Thank you.

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    Re: Safety Issue - Ferromagnetic metal under induction cooker

    This shouldn't happen with properly designed induction cookers. A thin mesh can't shield the magnetic field, only a copper or aluminium plate of sufficient thickness.



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    Re: Safety Issue - Ferromagnetic metal under induction cooker

    I have a similar idea, but I am not sure if the shielding is “strong” enough to shield the magnetic field from the induction cooker.

    I have checked some induction cookers in the market, all of them did not included such kind of preventive safety measure. Therefore I have doubt that is it really so difficult to prevent such case happen?



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    Re: Safety Issue - Ferromagnetic metal under induction cooker

    I have no induction cooker available for inspection, reviewing user manuals it seems to me that at least international manufacturers like Philips provide appropriate shielding. This can be either a ferrite plate below the induction coil or a massive conductive shield at the appliance bottom.

    The problem is however that these shielding means 1. cause extra manufacturing costs and 2. involve some unwanted losses. So if you can be sure that there's sufficient space free of conductive or magnetic material below the induction coil, using no shielding at all is the cheaper and more efficient alternative.



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    Re: Safety Issue - Ferromagnetic metal under induction cooker

    Quote Originally Posted by FvM View Post
    I have no induction cooker available for inspection, reviewing user manuals it seems to me that at least international manufacturers like Philips provide appropriate shielding. This can be either a ferrite plate below the induction coil or a massive conductive shield at the appliance bottom.

    The problem is however that these shielding means 1. cause extra manufacturing costs and 2. involve some unwanted losses. So if you can be sure that there's sufficient space free of conductive or magnetic material below the induction coil, using no shielding at all is the cheaper and more efficient alternative.
    I see that some induction cooktops have pan detecting circuits. I wonder if this could be implemented in reverse. Basically detect if there was a magnetic metal and unsafe distance to under side of the cooktop. The main problem I foresee is how the detector would differentiate between the needed pot on top and the unwanted metal underneath.



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    Re: Safety Issue - Ferromagnetic metal under induction cooker

    Quote Originally Posted by FvM View Post
    I have no induction cooker available for inspection, reviewing user manuals it seems to me that at least international manufacturers like Philips provide appropriate shielding. This can be either a ferrite plate below the induction coil or a massive conductive shield at the appliance bottom.

    The problem is however that these shielding means 1. cause extra manufacturing costs and 2. involve some unwanted losses. So if you can be sure that there's sufficient space free of conductive or magnetic material below the induction coil, using no shielding at all is the cheaper and more efficient alternative.
    Which part of the manual lead you to think that they have sheilding?



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