Article

Safety and efficiency of the wireless charging of electric vehicles

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Abstract

Wireless power transfer is a promising method to address the concerns over charging an electric vehicle. Since wireless charging stations operate without large cables or above-ground stations, they can be conveniently installed in public locations without the risk of vandalism or weather-inflicted damage, improving the lifespan of the electric vehicle charging station. In order for wireless charging stations to become widespread, possible health effects regarding exposure to the strong electromagnetic fields present during wireless power transfer must be investigated. This work examines, first, the potential human safety hazards, second, the electronic device interference, and, third, the thermal heating effects of wireless charging systems. A 3.3 kW wireless power transfer prototype was built in order to examine these effects. Changes in the wireless power transfer efficiency due to the coil misalignment were also investigated using an automated three-axis platform. Design considerations for electric vehicle wireless charging systems and safety recommendations are presented.

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... The attention to the electric transportation system is aimed at improving the safe and convenient wireless charging of the electric vehicles (EV) [1][2][3]. In the last decade the magnetic resonance technique is recognized to be the most appropriate for the contactless EV battery charging [2,4,5]. It does not necessitate to accurately park the vehicle, being not so sensitive as the generic, non-resonant inductive coupling [4,5]. ...
... In the last decade the magnetic resonance technique is recognized to be the most appropriate for the contactless EV battery charging [2,4,5]. It does not necessitate to accurately park the vehicle, being not so sensitive as the generic, non-resonant inductive coupling [4,5]. ...
... This EMF has high intensity and so may influence the operation of the communication channel by which the transmitter and the receiver exchange the information [4,6]. Moreover, the electromagnetic field produced by the WET system may induce high voltages and currents in the living organisms [4][5][6][7][8]. Thus, one of the main concerns for the WET development is the compliance with EMF safety standards and regulations [9][10]. ...
... EMFs are an issue of current concern in approaches for charging EVs. One limitation of EVs is the mileage per battery charge, which is substantially less than fuel-efficient ICEVs (Gao et al., 2015). Charging stations for batterypowered vehicles are becoming common in many cities, and more convenient modes of charging, like wireless power transfer (WPT), are being researched to address concerns regarding mileage (Bi et al., 2016). ...
... In addition, the size of the battery could be reduced, mitigating some of the weightrelated, non-exhaust air pollution problems posed by EVs (Bi et al., 2016). However, concern exists about how the EMF from WPT will affect humans, electronic and implanted medical devices, and the environment (Gao et al., 2015). Several studies have suggested that charging stations built in accordance with the International Commission on Non-Ionizing Radiation Protection standards should ensure human safety (Watanabe and Ishida, 2016;Ding et al., 2014b;Wen and Huang, 2017;Bi et al., 2016). ...
... Several studies have suggested that charging stations built in accordance with the International Commission on Non-Ionizing Radiation Protection standards should ensure human safety (Watanabe and Ishida, 2016;Ding et al., 2014b;Wen and Huang, 2017;Bi et al., 2016). However, other studies have noted precautions about proximity to WPT stations that are in use (Christ et al., 2013;Gao et al., 2015), as well as the potential risks of EMFs produced by dynamic charging in open traffic environments (Bi et al., 2016). Further research is needed to understand the health implications of wireless charging stations and the resulting EMFs, even when the magnetic or electric fields do not exceed practiced standards. ...
Technical Report
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Transportation has been linked to several adverse health impacts, with a large, but modifiable, burden of disease. In this work, researchers conceptualized and documented the linkages between transportation and health. Following that, the researchers quantified the impacts of transportation on health in a case study in Houston, Texas, that focused on premature mortality attributable to three pathways: air pollution, noise, and motor vehicle crashes. Researchers found that the pathways linking transportation to health include some that are beneficial, such as when transportation serves as means for social connectivity, independence, physical activity, and access. Some pathways link transportation to detrimental health outcomes from air pollution, road travel injuries, noise, stress, urban heat islands, contamination, climate change, community severance, and restricted green space, blue space, and aesthetics. Researchers defined each pathway and summarized its health outcomes as they occur in the literature and showed that transportation-related exposures and associated health outcomes, and their severity, can be influenced by inequity and intrinsic and extrinsic effect modifiers. In Houston, the researchers estimated 302 (95 percent confidence interval [CI]: 185–427) premature deaths were attributable to transportation-related noise, compared to 330 fatalities from motor vehicles, 631 (95 percent CI: 366–809) from PM2.5, and 159 (95 percent CI: 0–609) from NO2. Transportation-related noise and motor vehicle crashes were responsible for 1.7 percent and 1.9 percent of all-cause premature deaths in Houston, respectively. The estimated premature death rate attributable to transportation-related noise was comparable to the death rate caused by suicide, influenza, or pneumonia in the United States. PM2.5 was responsible for 7.3 percent of all-cause premature deaths, which is higher than the death rate associated with diabetes mellitus, Alzheimer’s disease, or motor vehicle crashes in the United States. Households with lower median income had a higher risk of adverse exposure and premature deaths. Researchers also showed a positive relationship between health impacts attributable to air pollution and road traffic passing through census tracts, which was more prominent for NO2. Although some of the pathways linking transportation and health are widely discussed in the literature, others are new or under-researched. This conceptual model can form the basis for future studies looking to explore the transportation-health nexus.
... EMFs are an issue of current concern in approaches for charging EVs. One limitation of EVs is the mileage per battery charge, which is substantially less than fuel-efficient ICEVs (Gao et al., 2015). Charging stations for battery-powered vehicles are becoming common in many cities and more convenient modes of charging, like wireless power transfer (WPT), are being researched to address concerns regarding mileage (Bi et al., 2016). ...
... Additionally, the size of the battery could be reduced, mitigating some of the weight-related non-exhaust air pollution problems posed by EVs (Bi et al., 2016). However, there is concern about how the EMF from WPT will affect humans, electronic and implanted medical devices, and the environment (Gao et al., 2015). Several studies have suggested that charging stations built in accordance with the International Commission on Non-Ionizing Radiation Protection standards should ensure human safety (Bi et al., 2016;Ding et al., 2014b;Watanabe and Ishida, 2016;Wen and Huang, 2017). ...
... Several studies have suggested that charging stations built in accordance with the International Commission on Non-Ionizing Radiation Protection standards should ensure human safety (Bi et al., 2016;Ding et al., 2014b;Watanabe and Ishida, 2016;Wen and Huang, 2017). However, other studies have noted precautions about proximity to WPT stations that are in use (Christ et al., 2013;Gao et al., 2015), as well as the potential risks of EMF produced by dynamic charging in open traffic environments (Bi et al., 2016). Further research is needed to understand the health implications of wireless charging stations and the resulting EMFs, even when the magnetic or electric fields do not exceed practiced standards. ...
Article
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Introduction Transportation is an integral part of our daily lives, giving us access to people, education, jobs, services, and goods. Our transportation choices and patterns are influenced by four interrelated factors: the land use and built environment, infrastructure, available modes, and emerging technologies/disruptors. These factors influence how we can or choose to move ourselves and goods. In turn, these factors impact various exposures, lifestyles and health outcomes. Aim and methods We developed a conceptual model to clarify the connections between transportation and health. We conducted a literature review focusing on publications from the past seven years. We complemented this with expert knowledge and synthesized information to summarize the health outcomes of transportation, along 14 identified pathways. Results The pathways linking transportation to health include those that are beneficial, such as when transportation serves as means for social connectivity, independence, physical activity, and access. Some pathways link transportation to detrimental health outcomes from air pollution, road travel injuries, noise, stress, urban heat islands, contamination, climate change, community severance, and restricted green space, blue space, and aesthetics. Other possible effects may come from electromagnetic fields, but this is not definitive. We define each pathway and summarize its health outcomes. We show that transportation-related exposures and associated health outcomes, and their severity, can be influenced by inequity and intrinsic and extrinsic effect modifiers. Conclusions While some pathways are widely discussed in the literature, others are new or under-researched. Our conceptual model can form the basis for future studies looking to explore the transportation-health nexus. We also propose the model as a tool to holistically assess the impact of transportation decisions on public health.
... Figure 4 shows the ranking of alternatives with respect to the environmental rion. The most sustainable alternative in environmental terms was the plug-in electr hicle, which was practically the same as the electric induction vehicle in the sense t did not emit nitrogen oxides or particulate matter, in accordance with [18][19][20][21][22][23]. The of environmental benefit between the plug-in electric vehicle and the electric indu vehicle was very close. ...
... Figure 4 shows the ranking of alternatives with respect to the environmental criterion. The most sustainable alternative in environmental terms was the plug-in electric vehicle, which was practically the same as the electric induction vehicle in the sense that it did not emit nitrogen oxides or particulate matter, in accordance with [18][19][20][21][22][23]. The level of environmental benefit between the plug-in electric vehicle and the electric induction vehicle was very close. ...
... The final results of the AHP multicriteria decision model indicate that, in economic and environmental terms, the plug-in electric vehicle is the most sustainable alternative for urban public road transport services, which is in accordance with [18][19][20][21][22][23][24][25][26]. The zero emissions of local pollutants and the low indirect emissions of carbon dioxide make the plug-in electric vehicle the cleanest alternative. ...
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The current combination of sustainable social awareness and the improved decision support systems, including multiple criteria decision models for sustainable development, creates the need for more efficient and accurate public policy decisions based on available technology. The continuous growth of urban public road transport in large cities, and therefore the worsening of air quality, along with recent economic crisis derived from the COVID-19 pandemic, is forcing public administrations to analyze the viability of current models, taking into consideration sustainable alternative energies. This study proposes a novel and consistent analytic hierarchy process (AHP) multicriteria decision-making (MCDM) model that combines both economic and environmental criteria, to evaluate public road transportation vehicles according to their alternative engine technologies and combustion characteristics. The proposed model has been applied to evaluate Madrid’s urban public road transport, based on 2020 data published by the Madrid City Council, compiled by authors, and assessed by a panel of 20 experts to identify criteria and factors included in the AHP-MCDM model. The findings illustrate the economic and environmental impact of alternative vehicles, show that the most sustainable alternative is the plug-in electric vehicle in economic and environmental terms, and assist policymakers and firms in future strategic decisions regarding sustainable urban transport policies.
... For example, static wireless charging requires the vehicle to be stopped at the same location for some time. A precise alignment between transmission and receiver pads is needed for the charge to be efficient [70,71]. This is made more challenging by the fact that natural parking positions vary remarkably [72]. ...
... Wireless charging technology has promising potential, but some open questions need addressing, for example health assurances [64,89]. The electromagnetic fields generated during wireless power transfer can be harmful between the charging pads and cause foreign objects to heat up quickly [71]. Future projects should make sure the technology is proven safe prior to large-scale deployments. ...
Article
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The shift to electric vehicles has brought about the potential to reduce the environmental damage caused by road transport. However, several challenges prevent wider adoption of electric vehicles, such as: a lack of charging facilities, long charging times, limited range, and the inconvenience of cable charging. These barriers are more pronounced for taxis, which generally cover longer distances than regular cars and have fewer opportunities for recharging. This research aims to evaluate wireless charging for range extended electric taxis, as a strategy to minimise these challenges and facilitate the electrification of fleets. A mixed methods approach, combining quantitative vehicle tracking with qualitative interviews and focus groups with drivers and local authority representatives, provided an understanding of 'facilitators' and 'barriers' to the introduction of wireless chargers in London and Nottingham, UK. Results indicated that current wired charging infrastructure does not facilitate recharging opportunities during taxi working hours, causing longer shifts or lower earnings. Drivers reported running on a range extender petrol engine once the battery is depleted, limiting the environmental benefits of electric taxis. We conclude that wireless chargers could facilitate the increased driving range of existing electric taxis if installed where drivers stop more often. The results support the implementation of opportunistic, short but frequent charging boosts (known as choko-choko) as part of policies to alleviate the barriers to the introduction of wireless charging of electric taxis, and foster more sustainable means of road transportation.
... Res. Public Health 2017, 14, 157 2 of 15 vehicles [7][8][9][10][11][12], and bio-implanted applications [13][14][15][16][17][18][19][20]. Human models of adults, children, and pregnant woman [21][22][23][24][25][26][27][28][29] have also been built to estimate possible biological threats. ...
... The number of turns in the driving coil (Tx loop) and pick-up coil (Rx loop) is 1 and in the transmission coil (Tx coil) and receiving coil (Rx coil) this value is 5. The distance between the loop and the coil for both Tx and Rx is 1 cm, the distance between the Tx and Rx coil (d TR ) is 30 cm. been carried out by researchers in different scenarios such as housing environments [5,6], electrical vehicles [7][8][9][10][11][12], and bio-implanted applications [13][14][15][16][17][18][19][20]. Human models of adults, children, and pregnant woman [21][22][23][24][25][26][27][28][29] have also been built to estimate possible biological threats. ...
Article
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The scenario of multiple wireless power transfer (WPT) systems working closely, synchronously or asynchronously with phase difference often occurs in power supply for household appliances and electric vehicles in parking lots. Magnetic field leakage from the WPT systems is also varied due to unpredictable asynchronous working conditions. In this study, the magnetic field leakage from parallel WPT systems working with phase difference is predicted, and the induced electric field and specific absorption rate (SAR) in a human body standing in the vicinity are also evaluated. Computational results are compared with the restrictions prescribed in the regulations established to limit human exposure to time-varying electromagnetic fields (EMFs). The results show that the middle region between the two WPT coils is safer for the two WPT systems working in-phase, and the peripheral regions are safer around the WPT systems working anti-phase. Thin metallic plates larger than the WPT coils can shield the magnetic field leakage well, while smaller ones may worsen the situation. The orientation of the human body will influence the maximum magnitude of induced electric field and its distribution within the human body. The induced electric field centralizes in the trunk, groin, and genitals with only one exception: when the human body is standing right at the middle of the two WPT coils working in-phase, the induced electric field focuses on lower limbs. The SAR value in the lungs always seems to be greater than in other organs, while the value in the liver is minimal. Human exposure to EMFs meets the guidelines of the International Committee on Non-Ionizing Radiation Protection (ICNIRP), specifically reference levels with respect to magnetic field and basic restrictions on induced electric fields and SAR, as the charging power is lower than 3.1 kW and 55.5 kW, respectively. These results are positive with respect to the safe applications of parallel WPT systems working simultaneously.
... 1-2005 [84] and ICNIRP guidelines were introduced. Other standardizations including UL 2750, SAE J2954, and ISO/IEC PT61980 follow the guidelines introduced by IC-NIRP [85]. ...
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The environmental concerns and reduction in fossil fuels have become a major concern due to which a large number of electric and hybrid vehicles are being built to minimize the contribution of greenhouse gas emissions from the transportation sector and to increase the efficiency of the overall vehicles. Electric vehicles (EVs) play an important role in today’s development of smarter cities and hence, there is a rapid growth of EVs all around the globe. Although they are found to be environmentally friendly and energy-efficient in comparison with internal combustion engine vehicles but lack of availability of a large number of charging stations at present time limits the use of EVs in the wider perspective. The broader use of EVs would require a huge amount of power from the existing power grids that may hit the prevailing distribution system. Further, charging such EVs equipped with huge battery packs, high power charging stations are essential to charge them at a speed comparable to the conventional oil/gas refueling system. The EVs considered in this study restricts to electric ships and electric cars being two major contributors towards greenhouse gas emissions. In order to address the aforementioned concerns, this study, therefore, presents state-of-the-art based on conventional and current technologies relating to EVs and their charging infrastructure. Further, possible configurations based on the integration of renewable energy sources and stationary energy storage systems are presented to aid the existing power grids. Lastly, challenges along with possible solutions and the future perspective are part of this study.
... For wirelessly charged EVs, two parameters have great effects on the charging: one is the existence of foreign objects over the primary station, and the other is the relative position between the primary and the secondary coils. Metal debris between the two charging pads could reach high temperatures and lower the WPT efficiency [30]. Moreover, living things should not be subjected to the strong magnetic fields. ...
Article
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Wireless power transfer (WPT) via magnetic resonance coupling is considered a promising outlet for electric vehicle (EV) charging due to the non-contact method. Unlike a traditional transformer, with WPT the relative spacing and lateral distance between the primary and secondary coils is highly variable, which can affect the wireless power delivery and lower the efficiency. A magnetic positioning approach that shares the wireless charging structure is proposed to solve the misalignment issue associated with wireless EV charging. The proposed alignment sensing system employs multiple auxiliary minor coils on the secondary side to position the charging pad. The positioning principle and equivalent circuit were analyzed. 108 samples were tested and they were distributed throughout the detection range of 70cm. The experimental results demonstrate that >92% of those samples have positioning errors of <2cm and 98% of them have positioning errors of <3cm.
... Market penetration scenarios for CS and EV (Foley & Gallach oir, 2015;Nemry & Brons, 2010;Pl€ otz, Gnann, K€ uhn, & Wietschel, 2013) are investigated issues in the EV sector as well, but are also discarded due to the specific review focus without a CS locating approach. Articles about safety aspects (Chung et al., 2013;Gao, Farley, Ginart, & Tse, 2016), authentication and privacy at the charging points (H€ ofer, Petit, Schmidt, & Kargl, 2013;Li, D an, & Nahrstedt, 2015;Saini, 2015), social aspects of EV adoption (Elbanhawy, 2015(Elbanhawy, , 2016Halbey, Kowalewski, & Ziefle, 2015), driver barriers (Haddadian, 2015), and user preferences (Philipsen, Schmidt, & Ziefle, 2015) are also excluded. ...
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With view to the high share of the transport sector in total energy consumption, e-mobility should play an important role within the transition of the energy systems. Policymakers in several countries consider electric vehicles (EV) as an alternative to fossil-fueled vehicles. In order to allow for the development of EV, the charging infrastructure has to be set up at locations with high charging potential, identified by means of various criteria such as demand density or trip length. Many methodologies for locating charging stations (CS) have been developed in the last few years. First, this paper presents a broad overview of publications in the domain of CS localization. A classification scheme is proposed regarding modeling theory and empirical application; further on, models are analyzed, distinguishing between users, route or destination centricity of the approaches and outcomes. In a second step, studies in the field of explicit spatial location planning are reviewed in more detail, that is, in terms of their target criteria and the specialization of underlying analytical processes. One divergence of these approaches lies in the varying level of spatial planning, which could be crucial depending on the planning requirements. It is striking that almost all CS locating concepts are proposed for urban areas. Other constraints, such as the lack of extensive empirical EV traffic data for a better understanding of the driving behavior, are identified. This paper provides an overview of the CS models, a classification approach especially considering the problem’s spatial dimension, and derives perspectives for further research.
... In relation to autonomous [30] and electric vehicles [31], the real implementation problems are associated with their limited range [32][33][34] and the limited charging network infrastructure [35,36]. ...
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Urban public transport systems must be economically efficient and additionally environmentally sustainable. Available decision support systems, including multiple criteria decision models, allow identifying which urban public transport vehicles are acceptable and those that should no longer be used in efficient and environmentally friendly cities. Previous research has ranked urban public transport vehicles by applying analytic hierarchy process multi-criteria decision-making models, from economic and non-polluting perspectives. However, until now, the types of vehicles acceptable for fleet renewal have not been identified. This study proposes a consistent combination of the ELECTRE TRI multiple criteria decision sorting method and the DELPHI procedure, the objective of which is to identify which urban public transport vehicles are acceptable, taking into consideration a suggested sustainable threshold, which includes economic and environmental strict requirements. The proposed model is based on 2020 Madrid urban public road transport data, published by Madrid City Council, which were compiled by the authors, and assessed by a panel of 20 experts to identify criteria and factors included in the model. Findings help local administrations to identify which urban public transport vehicles should be progressively replaced by those classified as economically efficient and additionally environmentally sustainable.
... Ev is still in an early technology adoption stage; it has not yet taken the role of main stream of major daily transportation option [51]. We cannot confidently approve the preposition of "WPC adds flexibility to work day and shall double the daily range" [9]. ...
... In the design of DC transformer, it needs to reduce the leakage inductance between the primary and secondary windings [21], while in the design of LLC resonant converter, the leakage inductance between the primary and secondary can be used as resonant inductance [22]. Therefore, in the design of LLC-DC transformer, the values of the leakage inductance should be taken into account. ...
Article
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... Over the past decade, pure electric vehicles (EVs) and plug-in hybrid electric vehicles (PHEVs) have increased in popularity due to environmental awareness and fossil fuel price fluctuations [1][2][3][4][5][6][7]. Wireless charging is a competitive option to overcome the inconvenience of plug-in EV charging and the relatively low energy density stored in batteries by opportunity charging [2]. ...
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This paper discussed the high-power and the miniaturization technology of capacitor charging power supply. The design and implementation of parallel operating high power density CCPS prototype with 'peak current shifting control' was described. The single CCPS prototype output power is 35kW and the whole output power of parallel operating CCPS is 70kW. Based on high switching frequency of 50 kHz and optimized transient thermal design technology the power density of 28.8 W/in3 is achieved with 60s operating times.
Chapter
100 year old gasoline engine technology vehicles have now become one of the major contributors of greenhouse gases. Plug-in Electric Vehicles (PEVs) have been proposed to achieve environmental friendly transportation. Even though the PEV usage is currently increasing, a technology breakthrough would be required to overcome battery related drawbacks. Although battery technology is evolving, drawbacks inherited with batteries such as; cost, size, weight, slower charging characteristic and low energy density would still be dominating constrains for development of EVs. Furthermore, PEVs have not been accepted as preferred choice by many consumers due to charging related issues. To address battery related limitations, the concept of dynamic Wireless Power Transfer (WPT) enabled EVs have been proposed in which EV is being charged while it is in motion. WPT enabled infrastructure has to be employed to achieve dynamic EV charging concept. The weight of the battery pack can be reduced as the required energy storage is lower if the vehicle can be powered wirelessly while driving. Stationary WPT charging where EV is charged wirelessly when it is stopped, is simpler than dynamic WPT in terms of design complexity. However, stationary WPT does not increase vehicle range compared to wired-PEVs. State-of-art WPT technology for future transportation is discussed in this chapter. Analysis of the WPT system and its performance indices are introduced. Modelling the WPT system using different methods such as equivalent circuit theory, two port network theory and coupled mode theory is described illustrating their own merits in Sect. 2.3. Both stationary and dynamic WPT for EV applications are illustrated in Sect. 2.4. Design challenges and optimization directions are analysed in Sect. 2.5. Adaptive tuning techniques such as adaptive impedance matching and frequency tuning are also discussed. A case study for optimizing resonator design is presented in Sect. 2.6. Achievements by the research community is introduced highlighting directions for future research.
Article
Electric vehicles (EVs) are becoming more popular due to concerns about the environment and rising gasoline prices. However, the charging infrastructure is lacking, and most people can only charge their EVs at home if they remember to plug in their cars. Using the principles of magnetic inductance and magnetic resonance, wireless charging (WC) could help significantly with these infrastructure problems by making charging secure and convenient. WC systems also have the potential to provide dynamic charging, making long road trips with EVs feasible and eliminating range anxiety. In this paper, we review the companies available in the literature that have developed electric vehicle wireless charging systems, automobile manufacturers interested in such technology, and research from universities and laboratories on the topic. While the field is still very young, there are many promising technologies available today. Some systems have already been in use for years, recharging public transit buses at bus stops. Safety and regulations are also discussed.
Conference Paper
This paper presents the feasibility study of bipolar pads for extremely high efficiency wireless battery chargers used in electric vehicle (EV) and plug-in hybrid electric vehicle (PHEV) applications. Due to the unconventional flux distribution in this system, a 3D finite element method was employed for its design and analysis. The importance of misalignment tolerance in this system is analyzed and discussed. The distinct features of rectangular bipolar topology have been exploited to develop the pads for wireless battery chargers for EV applications. An 8kW wireless charger prototype with 200mm gap and ±300mm horizontal misalignment tolerance has been fabricated and tested. From optimal to critical points of horizontal misalignments, the coupling coefficient of this system can maintain from 18.8% to 31.1%. With a 200mm gap, the charger efficiently transfers energy with an efficiency of 95.66% (overall DC to DC) at the desired position while still maintains at 95.39% efficiency with a ±300mm horizontal misalignment.
Conference Paper
Wireless power transmission is a promising technology which attracts attention in many fields and products. With mobile electronic products being prevalent, such as cellphones and PDAs, removing the power cord becomes a natural progression of achieving the ultimate mobility of the product. Wireless chargers for Electric Vehicles (EVs) would also be a convenient feature, avoiding any need to remember to plug in a power cord after parking the vehicle. Additional safety advantages may also be achieved due to eliminating exposed contacts. Nevertheless, wireless charging for EV is an application requiring high electrical power (up to hundreds of kilowatts) and larger area of wireless power transmission which increases electromagnetic field exposure. Thus, application of wireless charging to an EV requires a comprehensive analysis to ensure consumer safety. This paper focuses on the safety considerations of wireless charging for EVs, including potential electrical shock hazards, magnetic field exposure hazards, fire hazards, etc. It provides a historical background of wireless charging, particularly for EVs. It also reviews two potential technologies applicable to wireless charging of EVs. The concept of Hazard Based Safety Engineering (HBSE) is applied to the problem and UL's training's program is introduced.
Conference Paper
The recent development in simulation speed and capacity of magnetic field, and the power electronics, the field of wireless power transfer has been developed significantly. In the future transport area, electric vehicles are considered as replacement of oil-powered internal combustion engine driven vehicles, especially for the CO2 reduction and alternative energy perspective. However, electric vehicle requires several key issues resolved in view of the heavy weight, bulky volume, and limited driving distance. In this paper, the innovative on-road dynamic wireless charging technology for electric vehicle, called OLEV, is introduced. The electric vehicle charging technology can be classified as conductive or wireless, stationary or dynamic, and slow or fast. The fast charging in the range of 100 kW of power capacity and wireless dynamic charging concept are described. Also the design concept, system architecture and development process of optimizing the magnetic flux field for the higher power transfer efficiency are described in this paper. The dynamic charging technology is also compared with the stationary conductive charging for electric vehicles, in view of its development concept and status, and practical feasibility of the innovative technology.
Conference Paper
Inductive charging for Electric Vehicles (EVs) applies high frequency alternating currents in the transmitter pad or coil to inductively transfer power through loosely coupled induction to the receiving coil in EVs. The emerging of multiple EVs calls for a universal charging system that can charge most EVs efficiently and safely in variable external environments. This paper presents a comprehensive summary of considerations for designing a universal inductive charger, including that in hardware design such as topology, charging pads and batteries, and transient information such as voltage/current, status, weather, faults. Different options are provided and compared, and the suggested solution is reached after the analysis.
Article
This paper presents the design of a 5 kW inductive charging system for electric vehicles (EVs). Over 90% efficiency is maintained from grid to battery across a wide range of coupling conditions at full load. Experimental measurements show that the magnetic field strength meets the stringent International Commission on Non-Ionizing Radiation Protection (ICNIRP) guidelines for human safety. In addition, a new dual side control scheme is proposed to optimize system level efficiency. Experimental validation showed that a 7% efficiency increase and 25% loss reduction under light load conditions is achievable. The authors believe this paper is the first to show such high measured efficiencies for a level 2 inductive charging system. Performance of this order would indicate that inductive charging systems are reasonably energy efficient when compared to the efficiency of plug-in charging systems.
Article
A solution that enables safe, efficient, and convenient overnight recharging of electric vehicles is needed. Inductive power transfer (IPT) is capable of meeting these needs, however, the main limiting factor is the performance of the magnetic structures (termed power pads) that help transfer power efficiently. These should transfer 2-5 kW with a large air gap and have good tolerance to misalignment. Durability, low weight, and cost efficiency are also critical. 3-D finite-element analysis modeling is used to optimize circular power pads. This technique is viable, since measured and simulated results differ by 10% at most. A sample of power pads was considered in this work, and key design parameters were investigated to determine their influence on coupled power and operation. A final 2 kW 700-mm-diameter pad was constructed and tested having a horizontal radial tolerance of 130 mm (equivalent to a circular charging zone of diameter 260 mm) with a 200 mm air gap. The leakage magnetic flux of a charging system was investigated via simulation and measurement. The proposed pads meet human exposure regulations with measurement techniques specific by the Australian Radiation Protection and Nuclear Safety Agency (ARPANSA) which uses the International Commission on Non-Ionizing Radiation Protection (ICNIRP) guidelines as a foundation.
Article
A novel foreign-metal detection-system for wireless power transfer (WPT) is described. Foreign metal was heated only when placed between the primary coil and the secondary coil. By having the metal in that position, the quality factor of the secondary coil (Q2) decreased rather than other parameters, so Q2 was a suitable parameter for detecting the metal. We developed s Q2 measurement circuit that works without any battery in the secondary device, and also developed a prototype WPT system with the Q2 measurement circuit. Using this system, foreign metal that might be heated could be detected before heating.
Article
As future electric vehicles (EVs) emerge, achievable driving range by these vehicles remains a major bottleneck. A battery electric vehicle (BEV) has a fairly limited driving range per charging and takes long time to charge. Moreover, the existing technology only enables stationary charging which means that an EV has to be stationary during the duration of its charge replenishment. The use of contactless power transfer systems presents the opportunity of on-road charge replenishment of EVs. This paper presents case studies which illustrate the effect of on-road charge replenishment on the driving range of an EV for varying levels of power transfer by CPT system. On-road charge replenishment of idle EV at traffic signal is considered for urban driving scenario whereas on-road charge replenishment of an EV in motion is considered for highway driving scenario.
Article
Inductive power transfer is a practical method for recharging electric vehicles because it is safe, convenient, and reliable. The performance of the magnetic couplers that transfer power determines the overall feasibility of a complete system. Circular couplers are the most common topology in the literature; however, they have fundamentally limited coupling. Their flux patterns necessarily limit the operational air gap as well as tolerance to horizontal misalignment. A new polarized coupler topology [referred to as a double D (DD)] is presented, which overcomes these difficulties. DDs provide a charge zone five times larger than that possible with circular pads for a similar material cost and are smaller. A 0.31-m2 DD enables 2 kW of power transfer over an oval area measuring 540 mm × 800 mm with a 200-mm air gap. Leakage magnetic fields have been investigated and show that circular and DD couplers operating under similar power transfer conditions produce similar levels. Both topologies can be designed and operated to ensure compliance with international guidelines.
Conference Paper
It is mentioned that one million plug-in hybrid and electric vehicles will be on the road by 2015 in United States to reduce emission. If one million electric vehicles (EVs) are connected to the existing electric grid randomly, peak load will be very high. Electrified transportation based on a traditional thermal power system will be costly economically and environmentally though it has a great value for electric power and transportation sectors. EVs cannot alone solve the emission problem completely since they need electric power, which is one of the main sources of emission. Therefore, significant emission reduction greatly depends on the maximum utilization of renewable energy. Two models are investigated to show the effect of one million EVs on electric power and transportation sectors. Linear and non-linear systems are used in modeling the emissions generated from the transportation and electric energy sectors respectively.
Article
Resonance-based wireless power delivery is an efficient technique to transfer power over a relatively long distance. This technique typically uses four coils as opposed to two coils used in conventional inductive links. In the four-coil system, the adverse effects of a low coupling coefficient between primary and secondary coils are compensated by using high-quality (Q) factor coils, and the efficiency of the system is improved. Unlike its two-coil counterpart, the efficiency profile of the power transfer is not a monotonically decreasing function of the operating distance and is less sensitive to changes in the distance between the primary and secondary coils. A four-coil energy transfer system can be optimized to provide maximum efficiency at a given operating distance. We have analyzed the four-coil energy transfer systems and outlined the effect of design parameters on power-transfer efficiency. Design steps to obtain the efficient power-transfer system are presented and a design example is provided. A proof-of-concept prototype system is implemented and confirms the validity of the proposed analysis and design techniques. In the prototype system, for a power-link frequency of 700 kHz and a coil distance range of 10 to 20 mm, using a 22-mm diameter implantable coil resonance-based system shows a power-transfer efficiency of more than 80% with an enhanced operating range compared to ~40% efficiency achieved by a conventional two-coil system.
Conference Paper
Future electric vehicles (EVs) will be linked to the electric power system infrastructure; the vehicles will operate through frequent electric charging, as is the case with electric trains. Conventional batteries require a long recharging time; therefore, supercapacitors, rather than batteries, will play an important role in the future for charging of EVs. Recently, we manufactured small EVs powered only by supercapacitors. Supercapacitors have a long operating life, large current density, and environmentally friendly composition. Further, their energy level can be estimated from their terminal voltage. Because EVs powered by supercapacitors can operate for more than 20 min after being charged for only 30 s, the requirement for constant recharging of EVs is reduced substantially, thereby increasing the efficiency of these EVs. Wireless power transfer based on magnetic resonance is an extremely important technique that needs to be considered for enhancing the efficiency of EVs. In a laboratory experiment, this technique enabled approximately 50 W power transfer with more than 95% efficiency at a distance of more than 50 cm. In order to improve energy efficiency and safety of future EVs, the implementation of novel motion control techniques for EVs is required. Since EVs are powered by electric motors, they have three major advantages: motor torque generation is quick and accurate, a motor can be attached to each wheel, and motor torque can be estimated precisely. These advantages enable the realization of highperformance antilock braking and traction control systems, control of two-dimensional chassis motion, and estimation of road surface condition. In summary, we can achieve a large-scale development of future vehicles that employ three techniques: Electric Motors, Supercapacitors, and Wireless Power Transfer. This eliminates the requirement for engines, high performance Li-ion batteries, and large charging stations.
Article
RF energy harvesting holds a promise able future for generating a small amount of electrical power to drive partial circuits in wirelessly communicating electronics devices. This paper presents the overview and progress achieved in RF energy harvesting field. A modified form of existing CMOS based voltage doubler circuit is presented to achieve 160% increase in output power over traditional circuits at 0 dBm input power. A schottky diode based RF energy harvesting circuit performance is also studied with practical and simulations results.
Conference Paper
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, however this becomes more difficult as the complexity of the system grows. A general analysis of such LCIPT systems is essential for optimal system design. This analysis is undertaken for LCIPT systems that attempt to operate with zero phase angles between the primary input voltage and current in order to achieve minimum cost and maximum performance. The paper develops general boundary conditions that if followed ensures only one operating condition exists for any practical load thereby assuring stable operation and power transfer capability. This is verified by measuring a contact-less electric vehicle battery charging system
Inductively coupled power transmission (ICPT) is becoming an accepted technique for transferring power from an extended loop (track) to a number of galvanically isolated movable pickup coils. Operation of ICPT systems is discussed and limiting factors in their operation are investigated. In particular, the control of multiple pick-up coils and the number of such pick-ups that may be used before the system becomes unstable is investigated. These theoretical developments are compared with practical measurements from a prototype ICPT system
Article
An empirical relation for calculating approximate values of the average specific absorption rate (SAR) over a broad-frequency range for any prolate spheroidal model is derived for E-polarized incident plane waves. This formula provides a simple and inexpensive method for calculating the SAR for human and animal models, which otherwise requires complicated and expensive methods of calculation. The formula satisfies the f<sup>2</sup> SAR behavior at lower frequencies, the resonance characteristic at intermediate frequencies, the 1/f behavior past resonance, and the dependence on the dielectric constant at the geometrical optics limits. An expression for the resonance. frequency f<sub>0</sub> in terms of the dimensions of the model is also derived. The unknowm expansion coefficients were determined by curve-fitting all the data available in the second edition of the Radiofrequency Radiation Dosimetry Handbook. Numerical results obtained from the empirical relations are generally in good agreement with those calculated by other methods. Limitations of the formula and suggestions for its improvement are also discussed.
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