Inductive Charging System Research Articles

Magnetic and Thermal Coupled Field Analysis of Wireless Charging Systems for Electric Vehicles

This paper analyzes the effect of the operation frequency of an inductive charging system on the heat generation and its impact on the overall system efficiency. This is done considering the change of the material properties due to both frequency and temperature changes. The analysis is achieved using FEA modeling software ANSYS workbench. For faster subsequent optimization, an order-reduced model is implemented in a system-level simulation. Various tests show the good agreement of the results between the reduced order model and those of dynamically coupled-field solvers. Our implementation allows for precise calculation of the losses of the different system parts. Furthermore, an experiment has been conducted to validate the simulation results.

Towards the inductive on-road charging system for electric buses: Inspection of the Hungarian electric mobility fleet

Abstract Rising earth temperature and increasing greenhouse gas emission is largely caused by burning fossil fuels. Next to personal vehicle use, public transportation is also having a significant role. Therefore, the electrification of the bus lines is on many countries’ and cities’ agenda. Today, electric buses and trolleys having several drawbacks what needs to be solved. Thanks to the technical development, new technologies are available to substitute the conventional practices with more effective solutions. This paper focuses on the on-the-road charging technologies what can help to reduce the size of the battery and allows to increase the travel range with the support of free mobility. The paper presents a case study for Szeged, Hungary, where self-propelled trolleybus technology is examined. Self-propelled technology allows the batteries to be charged until it is connected to the overhead line. The extra energy can be stored and used again on road section without charging opportunities. Since Budapest, the capital of Hungary, moved towards the usage of electric buses the study also analyze the potential and impact of the replacing a frequent bus line with electric buses with the support of inductive charging technology.

Performance analysis of series/parallel and dual side LCC compensation topologies of inductive power transfer for EV battery charging system

In an inductive battery charging system, for better power transfer capability and attaining required power level, compensation is necessary. This paper analyzes series/parallel (S/P) and dual side inductorcapacitor- capacitor (LCC) compensation topologies for inductive power transfer of electric vehicle (EV) battery charging system. The design and modeling steps of inductive power transfer for electric vehicle battery charging system are presented. Besides, the equivalent electrical circuits are used to describe the circuit compensation topologies. The results convey that the efficiency of dual side LCC compensation is higher than that of S/P compensation at variable mutual inductance (misalignment).

Analysis of the E-Bus Berlin project

The E-Bus project was launched in August 2015 in Berlin should contribute to reduction of harmful emissions, noise reduction and development of the electric bus market in the area of Berlin and Brandenburg. This article discusses the first electric bus line in the capital of Germany, which was based on the use of various technical solutions. Two basic groups of such solutions were taken into account – the use of the Solaris Urbino 12 electric bus and the Bombardier Primove inductive charging system. The advantages of using electric vehicles in public transport in Berlin were also discussed. The presented issues were based on the environmental balance of the E-Bus Berlin project.

Tripolar Pad for Inductive Power Transfer Systems for EV Charging

A recently proposed magnetic structure called Tripolar Pad (TPP) is investigated as a primary pad in an inductive power transfer battery charging system for electric vehicles. In this paper, a TPP primary is evaluated for 3.3 kW power transfer to both a circular pad and a bipolar pad as secondary pads. A mathematical model is presented to describe the power transfer from the TPP primary to the secondary pads then a control scheme is proposed which exploits the mutual decoupling between the TPP coils to find optimal primary currents. The optimization of the primary currents in the TPP improved the effective coupling factor over traditional topologies, particularly when the secondary was misaligned, and maintained leakage magnetic flux below International Commission on Non-Ionizing Radiation Protection guidelines. The result for the proposed TPP is validated with practical measurements.

Self-Tuning Variable Frequency Controller for Inductive Electric Vehicle Charging With Multiple Power Levels

A self-tuning controller for contactless electric vehicle (EV) charging systems based on inductive power transfer (IPT) with multiple power levels is proposed. The multiple charging levels (consisting of ten charging levels) are achieved by controlling the energy injection frequency of the transmitter coil of the IPT system. The proposed controller is capable of self-tuning the switching operations to the natural resonance frequency of the IPT system, and it benefits from soft-switching operations (zero-current switching), which ensures the maximum performance of the IPT system. The proposed controller has such a simple design, which can be implemented based on a simplified control circuit. The simulation of the proposed controller for an inductive charging system at different charging levels is carried out in MATLAB/Simulink. Also the proposed controller with an ac/dc/ac converter is implemented experimentally on an IPT charging system to verify the effectiveness of the controller at different charging levels. The experimental test results conform with the simulation results and verify that the proposed controller effectively enables self-tuning capability and soft-switching operations at different charging levels for IPT-based contactless EV charging systems.

Fatigue damage assessment of electric roads based on probabilistic load models

The electro-mobility is becoming an increasingly present reality in recent years. The most important drawback of this technology is known to be limited battery autonomy. In an attempt to overcome this problem, for specific studies and testing, a number of roads have been implemented with coil systems in order to transfer power to electric vehicles, as described in this article. While on the one hand this could solve the problem of charging, on the other hand the introduction of a technology within an existing infrastructure could result in further structural issues. Since little or no information on the possible structural effect of the introduction of a charging system in the road is currently available, this study has focused on the long-term fatigue analysis of an electric road infrastructure in which an inductive wireless charging system has been introduced into the road structure. To perform the fatigue analysis, a recursive procedure defined within a probabilistic framework was developed and applied to a benchmark case study. The results obtained from the analysis represent an initial database for the definition of strategies and protocols for the monitoring, maintenance and operations of future electric roads infrastructures.

Design of a parallel-LC-compensated on-board charger for universal inductive charging in electric vehicles

This paper proposes an on-board charger with a parallel-connected LC circuit which works in coordination with the previously-proposed universal charger to achieve “real” universal inductive charging. For accurately tracking the optimal frequency and achieving soft switching of the primary charger, an additional inductor is connected in series with the P-connected resonant tank to form an “LCL” topology. Based on the voltage gain of the proposed resonant topology, a step-down DC-DC converter is used to generate standard charging voltage and current to EV batteries. The detailed design method of the LCL circuit and DC-DC converter is provided. Theoretical analysis demonstrates that the proposed LCL-compensated secondary resonant circuit has a stable output voltage vs varied magnetic coupling and load. Compared with series-compensated LC circuits, the proposed topology has two main advantages: a smaller range of the varied optimal AC frequency vs magnetic couplings and a much lower voltage stress on the resonant capacitance. Experiments based on a prototype of inductive charging system prove that the proposed on-board charger has high DC-DC efficiency, a smaller range of AC frequency, and a universally-achieved stable output.

An Inductive Charging and Real-Time Communications System for Profiling Moorings

AbstractThis paper describes a system for providing power and communications to moored profiling vehicles. A McLane Moored Profiler (MP) was equipped with a rechargeable battery pack and an inductive charging system to allow it to move periodically to a charging dock at the top of a subsurface mooring. Power was provided from a large bank of alkaline batteries housed in two 0.94-m steel spheres. Data were transferred inductively from the profiler to a mooring controller, and from there back to shore via radio and Iridium satellite modems housed in a small surface communications float on an “L” tether. An acoustic modem provided backup communications to a nearby ship in the event of loss or damage to the surface float. The system was tested in a 180-m-deep fjord (Puget Sound, Washington) and at Station ALOHA (A Long-Term Oligotrophic Habitat Assessment), a 4748-m-deep open-ocean location north of Hawaii. Basic functionality of the system was demonstrated, with the profiler repeatedly recharging at about 225 W (with an overall efficiency of about 70%). Data were relayed back to shore via Iridium and to a nearby ship via the radio and acoustic modems. The system profiled flawlessly for the entire 6-week test in Puget Sound, but charging at the deep site stopped after only 9 days in the deep-ocean deployment owing to damage to the charging station, possibly by surface wave action.

Electromagnetic fields in body by wireless inductive system

Purpose– The purpose of this paper is to calculate the induced electromagnetic fields in human body exposed to the wireless inductive charging system of electric vehicles has been conducted based on the numerical simulation.Design/methodology/approach– A homogeneous human body model is built and a representative wireless inductive charging system is used for the exposure assessment. The numerical simulation relies on finite element method with formulations in terms of the magnetic vector potential. The electromagnetic fields in terms of magnetic flux density and electric field are computed in the human body and compared with the electromagnetic exposure limits.Findings– It has been found that the induced EMFs in the near-field exposure configuration greatly comply with the safety guidelines.Originality/value– This study could help the development of the wireless inductive charging system with meeting the safety standard of radiation protection.

Loss Analysis of Circular Wireless EV Charging Coupler

With the demand for mass-produced commercial electric vehicles (EVs) growing over the last few years, the requirement for EV charging will increase, with continued growth as the number of on-road EVs increases. The EV wireless charging technology offers more flexibility than traditional plug-in charging technology for the following reasons: 1) full automation; 2) fast response; 3) high-power capacity; and 4) safety. The charging coupler is the key component in an inductive wireless charging system. This is a medium to high-frequency transformer (20 kHz), the core loss and the copper loss have to be considered carefully since these will affect the efficiency of the coupler. This paper presents the analysis of a circular coupler with ferrite bar cores and includes the analysis of the core loss considers the sizing of the device. The device is circular on a vertical axis and the air gap is large since there has to be a gap between the charger and vehicle. Therefore, the variation of the transformer coupler diameter is considered in terms of primary/secondary linkage for a fixed air gap. Resonance is used to improve the power factor and boost the transformer output voltage. The core loss is analyzed using finite element analysis in ANSYS Maxwell and the copper loss assumed the use of Litz wire.

Design and implementation of weaving‐type pad for contactless EV inductive charging system

The purpose of this study is to develop a new weaving-type pad for electric vehicles (EV) contactless inductive charging system. This proposed charging pad which consists of a weaving-type coil is fabricated to obtain a uniform mutual inductance profile over the charging surface and to solve the problem of present inductive coupled structure in which the EV has to be placed exactly on a specific place. Apart from weaving-type pad, type E core and two overlapping coils are utilised as a secondary pickup to guide and to pick more magnetic flux. The analysis and simulation of magnetic characteristic for comparing the proposed weaving-type pad to simple shape pad are performed by finite-element-analysis (FEA) software. Phase locked loop circuit is utilised to match the operating frequency and resonant frequency in order to solve the loading effect problem caused by impedance variation during the battery charging procedure. To validate the concept and system design, a laboratory scale test system with weaving-type pad for EV contactless inductive charging is built and tested. The coupling efficiency is found to be 66% for an air gap of 9 cm between the weaving-type charging pad and pickup when a 2 Ah lithium iron phosphate battery is charged.

Test Results of the PLUGLESS™ Inductive Charging System from Evatran Group, Inc.

Laboratory testing is conducted on a wireless charging system by the Idaho National Laboratory in support of the U.S. Department of Energy's Advanced Vehicle Testing Activity. System efficiency and magnetic and electric field strength are measured during wireless charger operation over a wide range of conditions, including coil gap, offset alignment, and power transfer rate. Component surface temperatures are monitored at a full-power charge rate. The PLUGLESSTM inductive charging system from the Evatran Group, Inc. is tested in a laboratory setting and results are detailed. CITATION: Carlson, R. and Normann, B., Test Results of the PLUGLESSTM Inductive Charging System from Evatran Group, Inc., SAE Int. J. Alt. Power. 3(1):2014, doi:10.4271/2014-01-1824. 2014-01-1824 Published 04/01/2014 doi:10.4271/2014-01-1824 saealtpow.saejournals.org

Evaluation of Electromagnetic Fields in Human Body Exposed to Wireless Inductive Charging System

This paper presents an evaluation of the EMFs in the human body exposed to the wireless inductive charging system of electric vehicles such that the compliance of this charging system with respect to human EM exposure limits can be examined. A magnetic resonance imaging-derived and high-resolution model of the human body is used. An exposure assessment of a representative wireless inductive charging system, under a limited set of operating conditions, is provided to estimate the induced EMFs. The numerical analysis is performed with the finite element method. Numerical modeling of the system next to a standing human model shows that the EM exposure limits can be absolutely satisfied even when the transmitter coil is very close to the body. Furthermore, the worst configuration for the exposure evaluation of the wireless charging system is taken into consideration. This paper provides a useful guideline for the industry to develop inductive charging systems following the safety standards of radiation protection.

Research on Inductive Power Charging Device of Unmanned Ground Vehicle

It is important to charge accumulator automatically on unmanned ground vehicles. A kind of inductive power charging system, with rotary type coupler and series-resonant power converter of full bridge, is designed. The working progress of resonant circuit and main circuit is simulated. The result of experiments shows that the simulation model of main circuit agrees well with practice and can instruct design of power converter in the future. The efficiency of power transferring decreases with coupler air gap increasing. The designed inductive charging device can charge accumulator with constant current while the air gap is 1.2 mm.

Implementing the functional requirements for determining the optimal arrangement of a distributed charging infrastructure

The optimized and reliable operation of future traffic by intelligent control systems will need to take into account boundary conditions that arise from alternative drive concepts. New challenges will need to be mastered when it comes to corresponding energy systems, control of operations, and communication interfaces, such as needed for the sufficient energy supply of traffic participants. However, they will need to be conformed to existing systems, technologies, and infrastructure to allow the common operation and positioning of charging elements with minimum interference between different modes of transport. Funded by the German Federal Ministry of Transport, Building and Urban Development (Bundesministerium für Verkehr, Bau und Stadtentwicklung) the project emil (Elektromobilität mittels induktiver Ladung – electric mobility via inductive charging) will integrate an inductive vehicle charging system and a compatible prototype bus fleet into Braunschweig's traffic infrastructure. This paper describes the methodic approach and the implementation of functional requirements in a traffic simulation tool that are required for an evaluation of future urban road traffic with an increased rate of electric vehicles. The modifications can subsequently be used to determine the optimal placement of the corresponding charging infrastructure with consideration of conventional traffic demand.

A High Efficiency 5 kW Inductive Charger for EVs Using Dual Side Control

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.

Operation of the Levitated Dipole Experiment Floating Coil

The Levitated Dipole Experiment (LDX) is an innovative facility to study plasma confinement in a dipole magnetic field, created by a superconducting solenoid (floating coil), which is magnetically levitated in the center of a 5 m diameter by 3 m tall vacuum chamber. This persistent mode, floating coil (F-coil) consists of a Nb3Sn magnet installed inside a high-pressure vessel filled with 12.5 MPa helium gas at room temperature. It is surrounded by a high heat capacity fiberglass-lead composite radiation shield and by a toroidal vacuum shell. The built-in tube heat exchanger serves to cool the magnet, the helium vessel, and the thermal shield. When positioned at the lower part of the vacuum chamber the F-coil is cooled by retractable cryogenic transfer lines to about 4.5 K and it is charged inductively by the charging coil installed outside of the vacuum chamber. Then the helium flow is interrupted, the heat exchanger is pumped out, retractable lines are disengaged from F-coil ports, the ports are plugged, and the F-coil is lifted to the middle of the chamber to initiate and study plasmas. After several hours and just before the F-coil warms up to about 10 K it is lowered down for the next re-cooling or for discharging. This paper describes the F-coil cooling system and inductive charging system operation and performance

The Daresbury tandem. A review 1970-92

A review of the technical developments which were made for the design of the Daresbury 20 MV tandem with particular emphasis on those ideas which were new and innovative is presented. The topics discussed include the high current inductive charging system or laddertron, the shielding of insulators and resistors from voltage surges, the hard vacuum ceramic/titanium accelerator tube, screening of sensitive electronics and the control system. The developments made to these systems over the years of full time operation from 1983 to 1992 are described and the most recent additions to the accelerator to improve the ion bunch stability and to improve the operational beam transmission efficiency using specially developed computer software are also described.

A study of the NSF laddertron

A detailed study has been made of the high voltage behaviour of the inductive charging system for the NSF tandem. This has shown how improvements can be made to its ultimate performance.