Patent•
Inductive power transfer
18 Dec 2008-
TL;DR: The paper looks at the background to IPT and how its development was based on sound engineering principles leading on to factory automation and growing to a $1 billion industry in the process.
Abstract: A detection method for use in a primary unit of an inductive power transfer system, the primary unit being operable to transmit power wirelessly by electromagnetic induction to at least one secondary unit of the system located in proximity to the primary unit and/or to a foreign object located in said proximity, the method comprising: driving the primary unit so that in a driven state the magnitude of an electrical drive signal supplied to one or more primary coils of the primary unit changes from a first value to a second value; assessing the effect of such driving on an electrical characteristic of the primary unit; and detecting in dependence upon the assessed effect the presence of a said secondary unit and/or a foreign object located in proximity to said primary unit.
Citations
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TL;DR: In this paper, a critical review outlines recent magneto-inductive research activities on wireless power transfer with the transmission distance greater than the transmitter coil dimension, and summarizes the operating principles of a range of wireless power research into the maximum power transfer and the maximum energy efficiency principles.
Abstract: Starting from Tesla's principles of wireless power transfer a century ago, this critical review outlines recent magneto-inductive research activities on wireless power transfer with the transmission distance greater than the transmitter coil dimension. It summarizes the operating principles of a range of wireless power research into 1) the maximum power transfer and 2) the maximum energy efficiency principles. The differences and the implications of these two approaches are explained in terms of their energy efficiency and transmission distance capabilities. The differences between the system energy efficiency and the transmission efficiency are also highlighted. The review covers the two-coil systems, the four-coil systems, the systems with relay resonators and the wireless domino-resonator systems. Related issues including human exposure issues and reduction of winding resistance are also addressed. The review suggests that the use of the maximum energy efficiency principle in the two-coil systems is suitable for short-range rather than mid-range applications, the use of the maximum power transfer principle in the four-coil systems is good for maximizing the transmission distance, but is under a restricted system energy efficiency (<;50%); the use of the maximum energy efficiency principle in relay or domino systems may offer a good compromise for good system energy efficiency and transmission distance on the condition that relay resonators can be placed between the power source and the load.
1,209 citations
Cites background from "Inductive power transfer"
...This idea was reported in 1998 in [32]....
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...Operating at 15 kHz for power applications, the use of intermediate or relay resonators without using impedance matching has been reported in [32]....
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TL;DR: In this article, the authors review the development of simple factory automation (FA) IPT systems for both today's complex applications and onward to a much more challenging application-IPT roadway.
Abstract: Inductive power transfer (IPT) has progressed to be a power distribution system offering significant benefits in modern automation systems and particularly so in stringent environments. Here, the same technology may be used in very dirty environments and in a clean room manufacture. This paper reviews the development of simple factory automation (FA) IPT systems for both today's complex applications and onward to a much more challenging application-IPT roadway. The underpinning of all IPT technology is two strongly coupled coils operating at resonance to transfer power efficiently. Over time the air-gap, efficiency, coupling factor, and power transfer capability have significantly improved. New magnetic concepts are introduced to allow misalignment, enabling IPT systems to migrate from overhead monorails to the floor. However, the demands of IPT roadway bring about significant challenges. Here, compared with the best FA practice, air-gaps need to be 100 times larger, power levels greater than ten times, system losses ten times lower to meet efficiency requirements, and systems from different manufacturers must be interoperable over the full range of operation. This paper describes how roadway challenges are being met and outlines the problems that still exist and the solutions designers are finding to them.
998 citations
Cites background from "Inductive power transfer"
...IPT systems, however, really found their application with clean factory automation (CFA) manufacturing flat panel displays and computer chips under stringently clean conditions and achieving higher yields than any competing technology [3]....
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...Other options include retuning the system using additional VAR correction mechanisms on either the primary or secondary side [3], however, these systems are often bulky and costly that is also undesirable....
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...was considered to be not viable for some time and against a background of disbelief it was not until the end of the twentieth century that real commercial IPT systems appeared [3]....
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...approach is secondary side control where the track current and frequency are held nominally constant, and each secondary independently regulated its power as required by its load [3], [7]....
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...There are a very large number of power supply circuits that may be used in an IPT system but all of them achieve the same outputs with different output frequency, efficiency, and reliability, however, modern IPT supplies generally favor current controlled supplies with unity power factor and with a controlled frequency [3]....
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TL;DR: This paper presents an overview of WPT techniques with emphasis on working mechanisms, technical challenges, metamaterials, and classical applications, and discusses about future development trends.
Abstract: Due to limitations of low power density, high cost, heavy weight, etc., the development and application of battery-powered devices are facing with unprecedented technical challenges. As a novel pattern of energization, the wireless power transfer (WPT) offers a band new way to the energy acquisition for electric-driven devices, thus alleviating the over-dependence on the battery. This paper presents an overview of WPT techniques with emphasis on working mechanisms, technical challenges, metamaterials, and classical applications. Focusing on WPT systems, this paper elaborates on current major research topics and discusses about future development trends. This novel energy transmission mechanism shows significant meanings on the pervasive application of renewable energies in our daily life.
875 citations
Cites background from "Inductive power transfer"
...1(a) depicts the circuit model of IPT systems [4], [5],...
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TL;DR: In this paper, the authors present a comprehensive overview of wireless charging techniques, the developments in technical standards, and their recent advances in network applications, with regard to network applications and discuss open issues and challenges in implementing wireless charging technologies.
Abstract: Wireless charging is a technology of transmitting power through an air gap to electrical devices for the purpose of energy replenishment. The recent progress in wireless charging techniques and development of commercial products have provided a promising alternative way to address the energy bottleneck of conventionally portable battery-powered devices. However, the incorporation of wireless charging into the existing wireless communication systems also brings along a series of challenging issues with regard to implementation, scheduling, and power management. In this paper, we present a comprehensive overview of wireless charging techniques, the developments in technical standards, and their recent advances in network applications. In particular, with regard to network applications, we review the static charger scheduling strategies, mobile charger dispatch strategies and wireless charger deployment strategies. Additionally, we discuss open issues and challenges in implementing wireless charging technologies. Finally, we envision some practical future network applications of wireless charging.
718 citations
TL;DR: This paper provides a comprehensive review of existing compensation topologies for the loosely coupled transformer and discusses the compensation requirements for achieving the maximum efficiency according to different WPT application areas.
Abstract: Wireless power transfer (WPT) is an emerging technology that can realize electric power transmission over certain distances without physical contact, offering significant benefits to modern automation systems, medical applications, consumer electronics, etc. This paper provides a comprehensive review of existing compensation topologies for the loosely coupled transformer. Compensation topologies are reviewed and evaluated based on their basic and advanced functions. Individual passive resonant networks used to achieve constant (load-independent) voltage or current output are analyzed and summarized. Popular WPT compensation topologies are given as application examples, which can be regarded as the combination of multiple blocks of resonant networks. Analyses of the input zero phase angle and soft switching are conducted as well. This paper also discusses the compensation requirements for achieving the maximum efficiency according to different WPT application areas.
659 citations
Cites background from "Inductive power transfer"
...The number of loads may change during charging for a roadway vehicle inductive power transfer (IPT) system [5], [25], [29]....
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...Therefore, the track current is always preferred to be constant to guarantee constant power delivery to each pickup system [5], [29]....
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...Nowadays, WPT has grown to a $1 billion commercial industry around the world [5]....
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References
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Journal Article•
TL;DR: The International Commission on Non-Ionizing Radiation Protection (ICNIRP)—was established as a successor to the IRPA/INIRC, which developed a number of health criteria documents on NIR as part of WHO’s Environmental Health Criteria Programme, sponsored by the United Nations Environment Programme (UNEP).
Abstract: IN 1974, the International Radiation Protection Association (IRPA) formed a working group on non-ionizing radiation (NIR), which examined the problems arising in the field of protection against the various types of NIR. At the IRPA Congress in Paris in 1977, this working group became the International Non-Ionizing Radiation Committee (INIRC). In cooperation with the Environmental Health Division of the World Health Organization (WHO), the IRPA/INIRC developed a number of health criteria documents on NIR as part of WHO’s Environmental Health Criteria Programme, sponsored by the United Nations Environment Programme (UNEP). Each document includes an overview of the physical characteristics, measurement and instrumentation, sources, and applications of NIR, a thorough review of the literature on biological effects, and an evaluation of the health risks of exposure to NIR. These health criteria have provided the scientific database for the subsequent development of exposure limits and codes of practice relating to NIR. At the Eighth International Congress of the IRPA (Montreal, 18–22 May 1992), a new, independent scientific organization—the International Commission on Non-Ionizing Radiation Protection (ICNIRP)—was established as a successor to the IRPA/INIRC. The functions of the Commission are to investigate the hazards that may be associated with the different forms of NIR, develop international guidelines on NIR exposure limits, and deal with all aspects of NIR protection. Biological effects reported as resulting from exposure to static and extremely-low-frequency (ELF) electric and magnetic fields have been reviewed by UNEP/ WHO/IRPA (1984, 1987). Those publications and a number of others, including UNEP/WHO/IRPA (1993) and Allen et al. (1991), provided the scientific rationale for these guidelines. A glossary of terms appears in the Appendix.
4,549 citations
Journal Article•
TL;DR: This publication replaces the low-frequency part of the 1998 guidelines and some guidance in this document is extended to 10 MHz to cover the nervous system effects in this frequency range.
Abstract: IN THIS document, guidelines are established for the protection of humans exposed to electric and magnetic fields in the low-frequency range of the electromagnetic spectrum. The general principles for the development of ICNIRP guidelines are published elsewhere (ICNIRP 2002). For the purpose of this document, the low-frequency range extends from 1 Hz to 100 kHz. Above 100 kHz, effects such as heating need to be considered, which are covered by other ICNIRP guidelines. However, in the frequency range from 100 kHz up to approximately 10 MHz protection from both, low frequency effects on the nervous system as well as high frequency effects need to be considered depending on exposure conditions. Therefore, some guidance in this document is extended to 10 MHz to cover the nervous system effects in this frequency range. Guidelines for static magnetic fields have been issued in a separate document (ICNIRP 2009). Guidelines applicable to movement-induced electric fields or time-varying magnetic fields up to 1 Hz will be published separately. This publication replaces the low-frequency part of the 1998 guidelines (ICNIRP 1998). ICNIRP is currently revising the guidelines for the high-frequency portion of the spectrum (above 100 kHz).
1,620 citations
TL;DR: This paper overviews theoretical and practical design issues related to inductive power transfer systems and verifies the developed theory using a practical electric vehicle battery charger.
Abstract: This paper overviews theoretical and practical design issues related to inductive power transfer systems and verifies the developed theory using a practical electric vehicle battery charger. The design focuses on the necessary approaches to ensure power transfer over the complete operating range of the system. As such, a new approach to the design of the primary resonant circuit is proposed, whereby deviations from design expectations due to phase or frequency shift are minimized. Of particular interest are systems that are neither loosely nor tightly coupled. The developed solution depends on the selected primary and secondary resonant topologies, the magnetic coupling coefficient, and the secondary quality factor.
1,389 citations
Patent•
08 May 2008
TL;DR: In this paper, the authors present a system and method for variable power transfer in an inductive charging or power system. In accordance with an embodiment, the system comprises a pad or similar base unit that contains a primary, which creates an alternating magnetic field, and a receiver comprises a means for receiving the energy from the magnetic field from the pad and transferring it to a mobile device, battery, or other device.
Abstract: A system and method for variable power transfer in an inductive charging or power system. In accordance with an embodiment the system comprises a pad or similar base unit that contains a primary, which creates an alternating magnetic field. A receiver comprises a means for receiving the energy from the alternating magnetic field from the pad and transferring it to a mobile device, battery, or other device. In accordance with various embodiments, additional features can be incorporated into the system to provide greater power transfer efficiency, and to allow the system to be easily modified for applications that have different power requirements. These include variations in the material used to manufacture the primary and/or the receiver coils; modified circuit designs to be used on the primary and/or receiver side; and additional circuits and components that perform specialized tasks, such as mobile device or battery identification, and automatic voltage or power-setting for different devices or batteries.
1,317 citations
TL;DR: A general approach is presented to identify the power transfer capability and bifurcation phenomena for loosely coupled inductive power transfer systems using a high order mathematical model consisting of both primary and secondary resonant circuits.
Abstract: Loosely coupled inductive power transfer (LCIPT) systems are designed to deliver power efficiently from a stationary primary source to one or more movable secondary loads over relatively large air gaps via magnetic coupling. In this paper, a general approach is presented to identify the power transfer capability and bifurcation phenomena (multiple operating modes) for such systems. This is achieved using a high order mathematical model consisting of both primary and secondary resonant circuits. The primary compensation is deliberately designed to make the primary zero phase angle frequency equal the secondary resonant frequency to achieve maximum power with minimum VA rating of the supply. A contactless electric vehicle battery charger was used to validate the theory by comparing the measured and calculated operational frequency and power transfer. For bifurcation-free operation, the power transfer capability and controllability are assured by following the proposed bifurcation criteria. Where controllable operation within the bifurcation region is achievable, a significant increase in power is possible.
1,044 citations