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I want to build a wireless power transmitter that works over a very short distance. Can I use my line voltage(120V at 60Hz) through the primary coil to induce voltage into a secondary coil about 1/4" away.

Am I foolish to think this is possible, or does it have to be at a high frequency?

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    \$\begingroup\$ What you describe is an "Air Core" Transformer. Two coils with air between them. \$\endgroup\$ – Majenko Mar 10 '15 at 18:45
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    \$\begingroup\$ It works, but it doesn't work well without a lot of coils. If you only have 1/4" distance, why don't you just add in at least a partial core to make it more efficient with less wire? \$\endgroup\$ – horta Mar 10 '15 at 18:55
  • \$\begingroup\$ How much power do you need? Maybe you could consider using a light and a small pV panel instead. \$\endgroup\$ – mkeith Mar 10 '15 at 20:03
  • \$\begingroup\$ I want to have enough power for a cell phone charger. \$\endgroup\$ – mrmjp Mar 10 '15 at 22:09
  • \$\begingroup\$ May not be practical to do with light/solar panel. \$\endgroup\$ – mkeith Mar 10 '15 at 22:33
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It's certainly possible, but AFAIK it usually involves high inductances (beefy coils), high powers (multi-ton induction furnace) or both. I think most consumer-level induction power transfer devices (induction chargers, induction cookers etc) work in the high-kilohertz level, making semiconductor power switching an absolute neccessity, but at the same time many other aspects of the device simpler.

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Inductive power transfer is possible at 60 Hz in fact that's how transformers work BUT you are wanting to transfer over a quarter of an inch so at best you imagine a transformer that is of the double E type and then picture the primary on one E and the secondary on the other now if your imaginary E cores are butted together you have your double E transformer that will operate normally but from experience it will be a buzzy bee SO far so good but here is the problem when you gradually increase the gap the reactive magnetising current increases heating the copper wire So the transformer will have to be huge to support your distance I suspect in the kilowatt ballpark SO possible but at lowpowers not practical

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