Inductive charging
Encyclopedia
Electromagnetic field
An electromagnetic field is a physical field produced by moving electrically charged objects. It affects the behavior of charged objects in the vicinity of the field. The electromagnetic field extends indefinitely throughout space and describes the electromagnetic interaction...
to transfer energy between two objects. This is usually done with a charging station. Energy is sent through inductive coupling
Inductive coupling
In electrical engineering, two conductors are referred to as mutual-inductively coupled or magnetically coupled when they are configured such that change in current flow through one wire induces a voltage across the ends of the other wire through electromagnetic induction...
to an electrical device, which then can use that energy to charge batteries.
Because there is a small gap between the two coils employed in each of the sender and receiver of the energy within the respective devices, inductive charging is considered a short-distance "wireless" energy transfer
Wireless energy transfer
Wireless energy transfer or wireless power is the transmission of electrical energy from a power source to an electrical load without artificial interconnecting conductors. Wireless transmission is useful in cases where interconnecting wires are inconvenient, hazardous, or impossible...
, despite the fact that there are typically more wires used with inductive charging than direct-contact charging, because it frees the user from having to deal with wires between the two devices. This is advantageous for many reasons.
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 proximity combine to form an electrical transformer
Transformer
A transformer is a device that transfers electrical energy from one circuit to another through inductively coupled conductors—the transformer's coils. A varying current in the first or primary winding creates a varying magnetic flux in the transformer's core and thus a varying magnetic field...
.
Greater distances can be achieved when the inductive charging system uses resonant inductive coupling
Resonant inductive coupling
Resonant inductive coupling or electrodynamic induction is the near field wireless transmission of electrical energy between two coils that are highly resonant at the same frequency. The equipment to do this is sometimes called a resonant or resonance transformer. While many...
.
Advantages
Inductive charging carries a far lower risk of electrical shock, when compared with conductive charging, because there are no exposed conductors. The ability to fully enclose the charging connection also makes the approach attractive where water impermeability is required; for instance, inductive charging is used for implanted medical devices that require periodic or even constant external power, and for electric hygiene devices, such as toothbrushes and shavers, that are frequently used near or even in water. Inductive charging makes charging mobile devices and electric vehicleElectric vehicle
An electric vehicle , also referred to as an electric drive vehicle, uses one or more electric motors or traction motors for propulsion...
s more convenient; rather than having to connect a power cable, the unit can be placed on or close to a charge plate.
Disadvantages
The main disadvantages of inductive charging are its lower efficiency and increased resistive heating in comparison to direct contact. Implementations using lower frequencies or older drive technologies charge more slowly and generate heat within most portable electronics. Inductive charging also requires drive electronics and coils, increasing the complexity and cost of manufacturing.Newer approaches reduce transfer losses through the use of ultra thin coils, higher frequencies, and optimized drive electronics. This results in more efficient and compact chargers and receivers, facilitating their integration into mobile devices or batteries with minimal changes required. These technologies provide charging times comparable to wired approaches, and they are rapidly finding their way into mobile devices. For example, the Magne Charge
Magne Charge
Magne Charge is a largely obsolete inductive charging system, also known as J1773, used to charge battery electric vehicles formerly made by General Motors, for vehicles such as the EV1, Chevy S10 EV, and other electric vehicles. It was produced by the General Motors subsidiary Delco Electronics....
system employed high-frequency induction to deliver high power at an efficiency of 86% (6.6 kW power delivery from a 7.68 kW power draw).
Examples
- Transcutaneous energy transfer (TET) systems in artificial heartArtificial heartAn artificial heart is a mechanical device that replaces the heart. Artificial hearts are typically used in order to bridge the time to heart transplantation, or to permanently replace the heart in case transplantation is impossible...
s and other surgically implanted devices.
- Inductive charging is used in Oral-BOral-BOral-B is a popular brand of oral hygiene products, including toothbrushes, toothpastes, mouthwashes and dental floss.It all started with a dentist, back in 1950, who created the first Oral-B toothbrush and its soft, end-rounded nylon bristles. Dr. Robert Hutson, a California periodontist, designed...
rechargeable toothbrushToothbrushThe toothbrush is an oral hygiene instrument used to clean the teeth and gums that consists of a head of tightly clustered bristles mounted on a handle, which facilitates the cleansing of hard-to-reach areas of the mouth. Toothpaste, which often contains fluoride, is commonly used in conjunction...
es by the Braun (company)Braun (company)' , formerly Braun AG, is a German consumer products company based in Kronberg, Germany.From 1984 until 2005, Braun was a wholly owned subsidiary of The Gillette Company, which had purchased a controlling interest in the company in 1967...
since the early 1990s1990sFile:1990s decade montage.png|From left, clockwise: The Hubble Space Telescope floats in space after it was taken up in 1990; American F-16s and F-15s fly over burning oil fields and the USA Lexie in Operation Desert Storm, also known as the 1991 Gulf War; The signing of the Oslo Accords on...
.
- Hughes Electronics developed the Magne ChargeMagne ChargeMagne Charge is a largely obsolete inductive charging system, also known as J1773, used to charge battery electric vehicles formerly made by General Motors, for vehicles such as the EV1, Chevy S10 EV, and other electric vehicles. It was produced by the General Motors subsidiary Delco Electronics....
interface for General MotorsGeneral MotorsGeneral Motors Company , commonly known as GM, formerly incorporated as General Motors Corporation, is an American multinational automotive corporation headquartered in Detroit, Michigan and the world's second-largest automaker in 2010...
. The General Motors EV1General Motors EV1The General Motors EV1 was an electric car produced and leased by the General Motors Corporation from 1996 to 1999. It was the first mass-produced and purpose-designed electric vehicle of the modern era from a major automaker, and the first GM car designed to be an electric vehicle from the...
electric carElectric carAn electric car is an automobile which is propelled by electric motor, using electrical energy stored in batteries or another energy storage device. Electric cars were popular in the late-19th century and early 20th century, until advances in internal combustion engine technology and mass...
was charged by inserting an inductive charging paddle into a receptacle on the vehicle. General Motors and Toyota agreed on this interface and it was also used in the Chevrolet S-10 EV and Toyota RAV4 EVToyota RAV4 EVThe RAV4 EV was an all-electric version of the popular RAV4 SUV produced by Toyota. It was leased from 1997 to 2003, and at the lessees request, many units were sold after the vehicle was discontinued. A total of 1,485 were leased and/or sold in California to meet the state’s mandate for...
vehicles.
- In 2006, researchers at the Massachusetts Institute of TechnologyMassachusetts Institute of TechnologyThe Massachusetts Institute of Technology is a private research university located in Cambridge, Massachusetts. MIT has five schools and one college, containing a total of 32 academic departments, with a strong emphasis on scientific and technological education and research.Founded in 1861 in...
reported that they had discovered an efficient way to transfer power between coils separated by a few meters. The team, led by Marin SoljačićMarin SoljacicMarin Soljačić is a Croatian physicist and electrical engineer known for wireless non-radiative energy transfer.-Biography:...
, theorized that they could extend the distance between the coils by adding resonance to the equation. The MIT wireless power project, called WiTricityWiTricityWiTricity, a portmanteau for "wireless electricity", is a trademark of WiTricity corporation referring to their devices and processes which use a form of wireless energy transfer including resonant energy transfer etc., the ability to provide electrical energy to remote objects without wires using...
, uses a curved coil and capacitive plates.
- April 28, 2009: An Energizer inductive charging station for the Wii remote is reported on IGN.
- At CESConsumer Electronics ShowThe International Consumer Electronics Show is a major technology-related trade show held each January in the Las Vegas Convention Center, Las Vegas, Nevada, United States. Not open to the public, the Consumer Electronics Association-sponsored show typically hosts previews of products and new...
in January 2009, Palm, Inc.Palm, Inc.Palm, Inc., was a smartphone manufacturer headquartered in Sunnyvale, California, that was responsible for products such as the Pre and Pixi as well as the Treo and Centro smartphones. Previous product lines include the PalmPilot, Palm III, Palm V, Palm VII, Zire and Tungsten. While their older...
announced their new PrePalm PreThe Palm Pre is a multimedia smartphone designed and marketed by Palm with a multi-touch screen and a sliding keyboard. The smartphone was the first to use Palm's Linux based mobile operating system, webOS...
smartphone would be available with an optional inductive charger accessory, the "Touchstone". The charger came with a required special backplate that became standard on the subsequent Pre Plus model announced at CESConsumer Electronics ShowThe International Consumer Electronics Show is a major technology-related trade show held each January in the Las Vegas Convention Center, Las Vegas, Nevada, United States. Not open to the public, the Consumer Electronics Association-sponsored show typically hosts previews of products and new...
2010.
- In August 2009 A consortium of interested companies called the Wireless Power ConsortiumWireless Power ConsortiumThe Wireless Power Consortium is a business alliance of more than 60 firms to develop open standards for inductive charging.-History:The organization was started in 2008 to create a universal wireless power charging standard so that electronic products and charging stations using the same standard...
announced they were nearing completion for a new industry standard for low-power Inductive charging
Electric vehicles
As mentioned above, Magne ChargeMagne Charge
Magne Charge is a largely obsolete inductive charging system, also known as J1773, used to charge battery electric vehicles formerly made by General Motors, for vehicles such as the EV1, Chevy S10 EV, and other electric vehicles. It was produced by the General Motors subsidiary Delco Electronics....
inductive charging was employed by several types of electric vehicles around 1998, but was discontinued
after the California Air Resources Board
California Air Resources Board
The California Air Resources Board, also known as CARB or ARB, is the "clean air agency" in the government of California. Established in 1967 in the Mulford-Carrell Act, combining the Bureau of Air Sanitation and the Motor Vehicle Pollution Control Board, CARB is a department within the...
selected the SAE J1772
SAE J1772
SAE J1772 is a North American standard for electrical connectors for electric vehicles maintained by the Society of Automotive Engineers and has the formal title "SAE Surface Vehicle Recommended Practice J1772, SAE Electric VehicleConductive Charge Coupler”...
-2001, or "Avcon
Avcon
Avcon is a company that manufactures charging interfaces for battery electric vehicles . The lettering convention is Avcon for the company and AVCON for the EV charging head....
", conductive
Conductive coupling
Conductive coupling is the transfer of electrical energy by means of physical contact via a conductive medium, in contrast to inductive coupling and capacitive coupling...
charging interface
for electric vehicles in California in June 2001.
In 2009, Evatran, a subsidiary of MTC Transformers, formally began development of Plugless Power
Plugless Power
Plugless Power is a type of Electric Vehicle Supply Equipment based on inductive charging. Plugless Power, a charging system for the electric vehicle , connects the on-board EV battery charger inductively to the electrical power source, without physical connection...
, an inductive charging system they claim is the world’s first hands-free, plugless, proximity charging system for Electric Vehicle
Electric Vehicle
The Electric Vehicle was an American automobile manufactured only in 1899. An electric cab, it was widely used in New York City; the company pioneered the use of pressed steel for wheels, and its cars featured front-wheel drive and brakes and rear wheel steering.-See also:* Battery electric...
s. With the participation of the local municipality and several businesses, field trials were begun in March, 2010, on the system scheduled to be available in fourth quarter 2010.
Researchers at the Korea Advanced Institute of Science and Technology (KAIST) have developed an electric transport system (called Online Electric Vehicle
Online Electric Vehicle
Online Electric Vehicle is an electric vehicle using electromagnetic induction. On Tuesday, 9 March 2010 researchers from The Korea Advanced Institute of Science and Technology launched a public transport system using a "recharging road". Electric power strips have been buried 30 cm deep...
, OLEV) where the vehicles get their power needs from cables underneath the surface of the road via non-contact magnetic charging, (where a power source is placed underneath the road surface and power is wirelessly picked up on the vehicle itself. As a possible solution to traffic congestion and to improve overall efficiency by minimizing air resistance and so reduce energy consumption, the test vehicles followed the power track in a convoy
Convoy
A convoy is a group of vehicles, typically motor vehicles or ships, traveling together for mutual support and protection. Often, a convoy is organized with armed defensive support, though it may also be used in a non-military sense, for example when driving through remote areas.-Age of Sail:Naval...
formation. In July 2009 the researchers successfully supplied up to 60% power to a bus over a gap of 12 cm.
In one inductive charging system, one winding is attached to the underside of the car, and the other stays on the floor of the garage.
The major advantage of the inductive approach for vehicle charging is that there is no possibility of electric shock
Electric shock
Electric Shock of a body with any source of electricity that causes a sufficient current through the skin, muscles or hair. Typically, the expression is used to denote an unwanted exposure to electricity, hence the effects are considered undesirable....
as there are no exposed conductors, although interlocks, special connectors and RCD
Residual-current device
A Residual Current Device is a generic term covering both RCCBs and RCBOs.A Residual-Current Circuit Breaker is an electrical wiring device that disconnects a circuit whenever it detects that the electric current is not balanced between the energized conductor and the return neutral conductor...
s (ground fault detectors) can make conductive coupling nearly as safe. An inductive charging proponent from Toyota contended in 1998 that overall cost differences were minimal, while a conductive charging proponent from Ford contended that conductive charging was more cost efficient.
In 2010 onwards, car makers are signaling their interest in wireless charging as another piece of the digital cockpit
Cockpit
A cockpit or flight deck is the area, usually near the front of an aircraft, from which a pilot controls the aircraft. Most modern cockpits are enclosed, except on some small aircraft, and cockpits on large airliners are also physically separated from the cabin...
. A group was launched in May 2010 by the Consumer Electronics Association
Consumer Electronics Association
The Consumer Electronics Association is a standards and trade organization for the consumer electronics industry in the United States. The Consumer Electronics Association is the preeminent trade association promoting growth in the $173 billion U.S...
to set a baseline for interoperability for chargers. In one sign of the road ahead a General Motors executive is chairing the standards effort group. Toyota and Ford managers said they also are interested in the technology and the standards effort.
Daimler’s Head of Future Mobility, Professor Herbert Kohler, however have expressed caution and said the inductive charging for EVs is at least 15 years away and the safety aspects of inductive charging for EVs have yet to be looked into in greater detail. For example, what would happen if someone with a pacemaker is inside the vehicle? Another downside is that the technology requires a precise alignment between the battery and the charging facility.
In November 2011, the Mayor of London
Mayor of London
The Mayor of London is an elected politician who, along with the London Assembly of 25 members, is accountable for the strategic government of Greater London. Conservative Boris Johnson has held the position since 4 May 2008...
, Boris Johnson
Boris Johnson
Alexander Boris de Pfeffel Johnson is a British journalist and Conservative Party politician, who has been the elected Mayor of London since 2008...
, and Qualcomm
Qualcomm
Qualcomm is an American global telecommunication corporation that designs, manufactures and markets digital wireless telecommunications products and services based on its code division multiple access technology and other technologies. Headquartered in San Diego, CA, USA...
announced a trial of 13 wireless charging points and 50 EVs in the Shoreditch
Shoreditch
Shoreditch is an area of London within the London Borough of Hackney in England. It is a built-up part of the inner city immediately to the north of the City of London, located east-northeast of Charing Cross.-Etymology:...
area of London
London
London is the capital city of :England and the :United Kingdom, the largest metropolitan area in the United Kingdom, and the largest urban zone in the European Union by most measures. Located on the River Thames, London has been a major settlement for two millennia, its history going back to its...
's Tech City
East London Tech City
East London Tech City is a technology hub located in London, United Kingdom. Tech City broadly occupies the part of London's East End between Old Street and the Queen Elizabeth Olympic Park in Stratford. Cisco Systems, Facebook, Google, Intel Corporation, McKinsey & Company and Vodafone are among...
, due to be rolled out in early 2012.
See also
- Charging stationCharging stationAn electric vehicle charging station, also called EV charging station, electric recharging point, charging point and EVSE , is an element in an infrastructure that supplies electric energy for the recharging of electric vehicles, plug-in hybrid electric-gasoline vehicles) or semi-static and mobile...
- In-road electric vehicle charger
- Resonant energy transferResonant energy transferResonant energy transfer may refer to:*Förster resonance energy transfer*Resonant inductive coupling...