wireless electricity or witricity

[MANU KM]

could it be possible that, two resonant coils 5m apart can transfer electricity wirelessly by magnetic induction coupling?
witricity invented group give this explanation to their technology.whether it is true or they didn't want to leak their technology ideas?

 

[betwixt]

Yes, it works and it is called a "Transformer".
Don't expect it to be efficient and don't forget that any conductive object in the vicinity will also pick up some of the energy.
My electric toothbrush recharges its battery using the same principle, 1.6MHz is pulsed through a coil in the charger base and standing the brush on top of it causes an induced voltage in a coil inside it to charge a Li Ion cell.

Brian.

 

[albbg]

No, witricity doesn't work on the same principle of a transformer, but it is based on an idea of the scientist Nikolas Tesla (XIX century). The transmission of energy exploit the principle of reciprocal resonance, so any object in the vicinity, that doesn't resonate on the same frequency of the coupled solenoids, doesn't pick up any energy. You may be interested in:
https://www.mit.edu/~soljacic/wireless-power_AoP.pdf

 

[MANU KM]

its resonant mag coupling, not the traditional magnetic induction which is in transformer.transformer doesn't work if the coils separated 5m apart. but witricity works across the room. electric toothbrush are also like transformer

 

[FvM]

so any object in the vicinity, that doesn't resonate on the same frequency of the coupled solenoids, doesn't pick up any energy.

You get statements like above only by simplifying the matter in an inappropriate way. Actually, any conductor in the vincinity will pick up some energy, if it spans an area perpendicular to the magnetic field, also without a resonant circuit. Some energy is also lost by radiation. Existing RF regulations limit the usage of wireless energy transfer to a few selected frequency bands, safety rules restrict the applicable power level considerably.

A transformer has leak and main inductance. Obviously, the relation between both parameters is very different for a conventional transformer with ferromagnetic core versus an "air" transformer, but the technical principle is the same. So you can, of course, consider the said energy transfer technique as a kind of transformer.

 

[ferdinnand]

I have to bump the thread as something is bothering me about this so-called near field concept. Physically speaking, one inserts let's say about 10 kW (70dBm) of RF power at 7 MHz into the transmitting coil. Then I have to say I'm somewhat concerned about the far-field effects of such a system. To my sense it should be unambiguous that at a distance of around 85 metres (2λ) away from the driven coil, anyone standing in the direction (again, standing around 80 metres away from it) would be exerted to 40dBm of equivalent EIRP just as if it was intended to work as a loop antenna in the first place (Friis calculation refers to 0dBi antenna gain). Obviously it's still far away from being as dangerous as putting your body in front of a microwave oven magnetron waveguide, but I'm just curious as I've never seen any article discussing about the far-field effects.

 

[FvM]

I think it's pretty unlikely that we'll face kW wireless power in the near future. What's developped presently are wireless mobile phone chargers and similar stuff as presented here https://www.wirelesspowerconsortium.com/

 

[ferdinnand]

I was just wondering as I've seen this public demonstration done by Eric Giler, where a TV set was powered by those coils. I personally wouldn't be so comfortable with sitting through the backs of that auditorium where the radiating zone could kick in.

 

[FvM]

I was just wondering as I've seen this public demonstration done by Eric Giler, where a TV set was powered by those coils. I personally wouldn't be so comfortable with sitting through the backs of that auditorium where the radiating zone could kick in.

I haven't seen the demonstrations, but I agree basically. In the wireless power consortium papers, you find calculations about maximum power levels related to RF exposure limits. Bit I don't think that these limit values are meant as an allowance for ubiquitous RF pollution. Fortunately, EMC limits are aigainst it, and i'm sure, public opinion will be, too.

 

[ferdinnand]

I do hope so. Thanks for clarifying.