Inductive charging

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Magne Charge wall, handheld, and floor mount
Magne Charge wall, handheld, and floor mount

Inductive charging charges electrical batteries using electromagnetic induction. A charging station sends energy through inductive coupling to an electrical device, which stores the energy in the batteries.

The other kind of charging, direct wired contact, also known as conductive charging or direct coupling, requires direct electrical contact between the batteries and the charger. Conductive charging is normally achieved by moving batteries from a device to charger, or connecting a device to a power source with plug-in wires.

The major advantage of the inductive approach over conductive charging is that there is no possibility of electrocution as there are no exposed conductors.

Induction chargers typically use an induction coil to create an alternating electromagnetic field from within a charging base station, and a second induction coil in the portable device takes power from the electromagnetic field and converts it back into electrical current to charge the battery. The two induction coils in close proximity combine to form an electrical transformer.[1][2]

Inductive charging generally charges too slowly and generates too much heat for most portable electronics,[citation needed] though it is used in some electric toothbrushes and wet/dry electric shavers, partly for the advantage that the battery contacts can be completely sealed to prevent exposure to water.[1][2]

General Motors' (GM) discontinued EV-1 electric car was charged with an inductive charging paddle, which was inserted into a receptacle on the vehicle. GM and Toyota agreed on a standard inductive charging interface, called Magne Charge, but abandoned its support in 2002 when the California Air Resources Board settled on a conductive charging interface for electric vehicles in California.[3]

In 2006, researchers at the Massachusetts Institute of Technology reported that they had discovered an efficient way to transfer power between coils separated by a few meters. The team, led by Marin Soljačić, theorized that they could extend the distance between the coils by adding resonance to the equation. The MIT wireless power project, called WiTricity, uses a curved coil and capacitive plates.[4][5]

Because there is a small gap between the two coils, inductive charging is one kind of short-distance wireless energy transfer.

MIT has developed a way of wireless charging, called WiTricity by use of inductive coupling and resonance, that is said to be effective at ranges up to about 7 feet.

The electric toothbrush charger is another example of how this principle can be used. The main drawback to induction, however, is the short range. The receiver must be in very close proximity to the transmitter or induction unit in order to inductively couple with it.

  • Transcutaneous energy transfer (TET) systems in artificial hearts and other surgically implanted devices.
  • Devices using induction to charge portable consumer electronics such as cell phones.[6][7]

[edit] References

  1. ^ a b "How can an electric toothbrush recharge its batteries when there are no metal contacts between the toothbrush and the base?" (Commercial website). HowStuffWorks, Inc., via howstuffworks.com. Retrieved on 2007-08-23.
  2. ^ a b US patent 6972543 "Series resonant inductive charging circuit"
  3. ^ "GM Pulls the Plug on Inductive Charging: Letter from General Motors Advanced Technology Vehicles." (Website). EV1 Club. (Letter dated) 2002-03-15. Retrieved on 2007-08-23.
  4. ^ Hadley, Franklin. [http://web.mit.edu/newsoffice/2007/wireless-0607.html "Goodbye wires…: MIT team experimentally demonstrates wireless power transfer, potentially useful for powering laptops, cell phones without cords."] MIT News, Massachusetts Institute of Technology, via mit.edu, 2007-06-07. Retrieved on 2007-08-23.
  5. ^ Castelvecchi, Davide. "Wireless energy may power electronics: Dead cell phone inspired research innovation." TechTalk, Massachusetts Institute of Technology, via mit.edu, Vol. 51, No. 9, 2006-11-15. Retrieved on 2007-08-23.
  6. ^ SplashPower; Battery powered devices can be charged by placing them on an induction mat.
  7. ^ eCoupled unveiled their own take on inductive coupling, which will soon be used on [http://www.hermanmiller.com "Herman Miller" desks to recharge devices wirelessly]

[edit] External links


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