In general a wireless power system consists of a "transmitter" device connected to a source of power such as a mains power line, which converts the power to a time-varying electromagnetic field, and one or more "receiver" devices which receive the power and convert it back to DC or AC electric current which is used by an electrical load. The technologies, listed in the table below, differ in the distance over which they can transfer power efficiently, whether the transmitter must be aimed (directed) at the receiver, and in the type of electromagnetic energy they use: time varying electric fields, magnetic fields, radio waves, microwaves, infrared or visible light waves. Wireless power transfer is a generic term for a number of different technologies for transmitting energy by means of electromagnetic fields. Generic block diagram of a wireless power system Īn important issue associated with all wireless power systems is limiting the exposure of people and other living beings to potentially injurious electromagnetic fields. Proposed applications for this type include solar power satellites and wireless powered drone aircraft. These techniques can transport energy longer distances but must be aimed at the receiver. In far-field or radiative techniques, also called power beaming, power is transferred by beams of electromagnetic radiation, like microwaves or laser beams. Inductive coupling is the most widely used wireless technology its applications include charging handheld devices like phones and electric toothbrushes, RFID tags, induction cooking, and wirelessly charging or continuous wireless power transfer in implantable medical devices like artificial cardiac pacemakers, or electric vehicles. In near field or non-radiative techniques, power is transferred over short distances by magnetic fields using inductive coupling between coils of wire, or by electric fields using capacitive coupling between metal electrodes. Wireless power techniques mainly fall into two categories, near field and far-field. Wireless power transfer is useful to power electrical devices where interconnecting wires are inconvenient, hazardous, or are not possible. The technology of wireless power transmission can eliminate the use of the wires and batteries, thus increasing the mobility, convenience, and safety of an electronic device for all users. In a wireless power transmission system, a transmitter device, driven by electric power from a power source, generates a time-varying electromagnetic field, which transmits power across space to a receiver device, which extracts power from the field and supplies it to an electrical load. Wireless power transfer ( WPT), wireless power transmission, wireless energy transmission ( WET), or electromagnetic power transfer is the transmission of electrical energy without wires as a physical link. When the phone is set on the pad, a coil in the pad creates a magnetic field which induces a current in another coil, in the phone, charging its battery. Inductive charging pad for a smartphone as an example of near-field wireless transfer.
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