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Air core xformer -- max power xfer?

Discussion in 'Electronic Design' started by D Yuniskis, Mar 25, 2010.

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  1. D Yuniskis

    D Yuniskis Guest


    How much power can one expect to *reasonably* (i.e., in
    a *small* appliance) transfer using small-ish coils
    separated by a good fraction of an inch?

    E.g., how do these "wireless charger" gizmos work?
    Or, how *well* do they work? (recognizing that
    they tend to operate over closer distances).

  2. Not much. A bit more than not much at higher cycle rates.

  3. The wireless charger gizmos have cores.

  4. More reinforcement of my knowledge of how dumb you are.
  5. As long as it doesn't take 20 watts to push that half watt.

    Otherwise, I think we have enough RF immersion in life. And yes, that
    is the word I want.
  6. D Yuniskis

    D Yuniskis Guest

    Hi Paul,
    Well, I'm looking at a *good* fraction of an inch (e.g., closer
    to an inch than not!). And, power levels a fair bit higher.
    A cursory run through the math says I should be able to get
    a few watts (3-5) at reasonably high efficiency (60-70%). Of
    course, depends on coil sizes, quality of components, etc.

    I haven't yet looked into what the consequences re: emissions
    might be :<

    And, I'll have to recheck my math with firmer parameters.

    Maybe I'll poke around tomorrow and see if I can find any
    products "on a shelf" that I can examine...

    I'll also have to make some time to see what google turns
    up. Always a bit of a game trying to figure out what search
    terms to use! :)
  7. Fred Abse

    Fred Abse Guest

    More spectrum pollution...
  8. The wireless chargers use resonant coils. It works well enough when
    there's almost direct contact but efficiency drops off quickly with

    How much power can be transferred depends on safety issues. Resonant
    coils are also used to make inductively heated crucibles and high
    efficiency electric stovetops.
  9. Joerg

    Joerg Guest

    That depends on the circular area you are allowed to occupy. IOW, a
    large diameter and a long distance is favorable, small diameter and long
    distance is not so good.

    Check out "series resonant converter" and you'll see papers with lots of
    valuable information in there such as this one:
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