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Wireless Power Transfer | Electrical Engineering Books |VERIFIED|

is a professor and research associate with Kyoto University. Previously he was an IEEE MTT-S Distinguish Microwave Lecturer and an IEEE MTT-S Technical Committee 25 (Wireless Power Transfer and Conversion) Former Chair. Shinohara is also an IEEE MTT-S Kansai Chapter TPC member, the IEEE Wireless Power Transfer Conference founder, and an Advisory Committee Member, the URSI Commission D Vice Chair, the International Journal of Wireless Power Transfer (Cambridge Press) an Executive Editor, the First Chair, and a Technical Committee Member on IEICE Wireless Power Transfer, the Japan Society of Electromagnetic Wave Energy Applications Adviser, the Space Solar Power Systems Society Vice Chair, the Wireless Power Transfer Consortium for Practical Applications (WiPoT) Chair, and the Wireless Power Management Consortium (WPMc) Chair. He received his B.E. degree in electronic engineering, and the M.E. and Ph.D. (Eng.) degrees in electrical engineering from Kyoto University, Japan.

Wireless power transfer | Electrical Engineering Books


received a BSc degree in Radio Physics from Nanjing University, Nanjing, China and a Ph.D degree from University of Birmingham, Birmingham, U.K. His doctoral research concerned high-temperature superconductor microwave filters. He was with the National Satellite Meteorological Centre of China, Beijing, China. After completing his PhD, he was with the University of Birmingham, where his research concerned phased arrays for reflector observing systems. Then he moved tothe Department of Electronic and Electrical Engineering, University of Bristol, Bristol, U.K. His research in Bristol was mainly on the development of highly efficient and linear amplifiers. He is with the Department of Electrical Engineering and Electronics, University of Liverpool, Liverpool, UK since 2013. His past and current research interests include microwave power amplifiers, filters, electromagnetic compatibility, frequency selective surfaces, energy harvesting and wireless power transfer.

This book describes systematically wireless power transfer technology using magnetic resonant coupling and electric resonant coupling and presents the latest theoretical and phenomenological approaches to its practical implementation, operation and its applications. It also discusses the difference between electromagnetic induction and magnetic resonant coupling, the characteristics of various types of resonant circuit topologies and the unique features of magnetic resonant coupling methods. Designed to be self-contained, this richly illustrated book is a valuable resource for a broad readership, from researchers to engineers and anyone interested in cutting-edge technologies in wireless power transfer.

Takehiro Imura is an Associate Professor at the Faculty of Science and Technology, Department of Electrical Engineering at Tokyo University of Science. His research interests include wireless power transfer using magnetic resonant coupling and electric resonant coupling for stationary electric vehicles, in-motion electric vehicles, medical equipments, space equipments, IoT devices and sensors. His research interests also include fusion of dynamic wireless power transfer for electric vehicle and solar power to reduce CO2.

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. 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. 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.[2] Wireless power transfer is useful to power electrical devices where interconnecting wires are inconvenient, hazardous, or are not possible.

Wireless power techniques mainly fall into two categories, near field and far-field.[3] 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.[4][5][6][7] 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 far-field or radiative techniques, also called power beaming, power is transferred by beams of electromagnetic radiation, like microwaves[8] or laser beams. These techniques can transport energy longer distances but must be aimed at the receiver. Proposed applications for this type include solar power satellites and wireless powered drone aircraft.[9][10][11]

Wireless power transfer is a generic term for a number of different technologies for transmitting energy by means of electromagnetic fields.[14][15][16] 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.[17]

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.[14][17] At the transmitter the input power is converted to an oscillating electromagnetic field by some type of "antenna" device. The word "antenna" is used loosely here; it may be a coil of wire which generates a magnetic field, a metal plate which generates an electric field, an antenna which radiates radio waves, or a laser which generates light. A similar antenna or coupling device at the receiver converts the oscillating fields to an electric current. An important parameter that determines the type of waves is the frequency, which determines the wavelength.

Wireless power uses the same fields and waves as wireless communication devices like radio,[18][19] another familiar technology that involves electrical energy transmitted without wires by electromagnetic fields, used in cellphones, radio and television broadcasting, and WiFi. In radio communication the goal is the transmission of information, so the amount of power reaching the receiver is not so important, as long as it is sufficient that the information can be received intelligibly.[15][18][19] In wireless communication technologies only tiny amounts of power reach the receiver. In contrast, with wireless power transfer the amount of energy received is the important thing, so the efficiency (fraction of transmitted energy that is received) is the more significant parameter.[15] For this reason, wireless power technologies are likely to be more limited by distance than wireless communication technologies.

Wireless power transfer may be used to power up wireless information transmitters or receivers. This type of communication is known as wireless powered communication (WPC). When the harvested power is used to supply the power of wireless information transmitters, the network is known as Simultaneous Wireless Information and Power Transfer (SWIPT);[20] whereas when it is used to supply the power of wireless information receivers, it is known as a Wireless Powered Communication Network (WPCN).[21][22][23]

The oscillating electric and magnetic fields surrounding moving electric charges in an antenna device can be divided into two regions, depending on distance Drange from the antenna.[14][17][18][24][30][31][32] The boundary between the regions is somewhat vaguely defined.[17] The fields have different characteristics in these regions, and different technologies are used for transferring power:

In inductive coupling (electromagnetic induction[24][45] or inductive power transfer, IPT), power is transferred between coils of wire by a magnetic field.[18] The transmitter and receiver coils together form a transformer[18][24] (see diagram). An alternating current (AC) through the transmitter coil (L1) creates an oscillating magnetic field (B) by Ampere's law. The magnetic field passes through the receiving coil (L2), where it induces an alternating EMF (voltage) by Faraday's law of induction, which creates an alternating current in the receiver.[15][45] The induced alternating current may either drive the load directly, or be rectified to direct current (DC) by a rectifier in the receiver, which drives the load. A few systems, such as electric toothbrush charging stands, work at 50/60 Hz so AC mains current is applied directly to the transmitter coil, but in most systems an electronic oscillator generates a higher frequency AC current which drives the coil, because transmission efficiency improves with frequency.[45]

Inductive coupling is the oldest and most widely used wireless power technology, and virtually the only one so far which is used in commercial products. It is used in inductive charging stands for cordless appliances used in wet environments such as electric toothbrushes[24] and shavers, to reduce the risk of electric shock.[46] Another application area is "transcutaneous" recharging of biomedical prosthetic devices implanted in the human body, such as cardiac pacemakers and insulin pumps, to avoid having wires passing through the skin.[47][48] It is also used to charge electric vehicles such as cars and to either charge or power transit vehicles like buses and trains.[24]


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