Contactless Power Transfer Research Articles

Magnetic Coupling Enhancement for Contactless Power Transfer With Superconductors

As diamagnetic materials, superconductors confine magnetic fields efficiently. Based on this property, we designed and fabricated a novel contactless power transfer (CPT) coupler consisting of a ferrite core wrapped with superconductor layers, which results in an obvious enhancement of the coupling coefficient. We analyzed the underlying causes of coupling enhancement with a magnetic circuit model. Additionally, we used finite-element simulations to investigate the performance of the structure as a function of applied frequency. The results predict that the coupler would be efficient up to 50 kHz. Thus, the modified coupler should be practical for CPT systems.

多関節アームロボットへの電界結合非接触給電

Both power feeding cable and control signal cable in the arm robot to the servo motor are easily cut due to too fast and frequent rotation of each joint. We propose an electrically coupling contactless power transfer system to an articulated arm robot for solve the problem.

可変インピーダンスを考慮した非接触給電システムの回路解析と特性評価

A contactless power transfer system using a repeater coil (Repeater Coil topology) has been proposed as a method of suppressing overcurrent without power control during misalignment or no-load. By installing a repeater coil between the primary and secondary coils, it is possible to increase the input impedance in the case of misalignment of the secondary coil or no-load condition. In addition, another a contactless power transfer system using primary parallel and secondary series resonance capacitors (PS Capacitor topology) has been proposed. In the PS Capacitor topology, the input impedance can be increased during misalignment of the secondary coil or no-load condition similar to the Repeater Coil topology. In this paper, we evaluated the characteristics of both these topologies. First, we conducted a circuit analysis of the Repeater Coil topology and proposed a design method. In addition, we theoretically clarified the characteristic difference of the two topologies and experimentally evaluated the characteristics.

Electromagnetic field patterns and energy flux of efficiency optimal inductive power transfer systems

The design of contactless power supplies with inductive power transfer (IPT) is still a challenge even though such systems have become more and more established for various applications. This article presents an intuitive, educational introduction to IPT system design for practicing engineers who are new to the field. While following the path of the energy through the IPT system, the contactless power transfer is explained with a circuit-oriented approach, extended by an analysis of the field patterns and the energy flux across the air gap. Finite element method simulation results for the Poynting vector are shown to illustrate the power transfer process. Finally, a minimization of the reactive power demand of the IPT coils is performed, from which the general requirements for an efficiency optimal design of the IPT system can be intuitively understood.

A Rotary-Type Contactless Power Transfer System Using HTS Primary

This paper investigates a new rotary-type contactless power transfer (CPT) system integrated with a high temperature superconducting (HTS) primary and a conventional copper secondary. The structural design, magnetic modeling, and equivalent circuit simulation of a pot-core rotating transformer using an HTS primary are presented to analyze the transfer power and efficiency characteristics of a 9-kW class CPT device. The corresponding superconducting ac loss properties of the HTS primary are also discussed to construct a circuit-field-superconductor-coupled analysis model and thus to clarify the functional relationships among the transfer power, the ac loss, and its equivalent resistance in the rotary-type CPT system.

Research on the Characteristic Change in an Inductive‐Coupling‐Type Contactless Power Transformer for a Railway According to the Core Shapes and Misalignment Utilizing a T‐Type Equivalent Circuit

SUMMARYAlthough an electric railway is an ecological transportation system, there are some obstacles when an electric railway is installed: the high cost for installation and the detrimental effect on the environment. A contactless power transfer system (CPT system) is a solid solution for these obstacles. However, a CPT system for a railway application needs to have a high capacity and a tolerance to the misalignment of the coils. In this paper, inductive power transfer theory, which is able to transfer a greater amount of energy than the electromagnetic resonance method is chosen, and its tolerance to the misalignment is our focus. The authors measure various core shapes, and their coupling coefficients, leakage inductances, and excitation inductances according to the misalignment are obtained with a finite element method (FEM) analysis. By using these parameters, the transmitted power and efficiency are calculated by two equivalent circuits: the S/S circuit and the S/P circuit. Finally, by comparing the parameters and transmitted power of each core shape and circuit, the authors show that the circular core can transfer 100 kW of energy for a misalignment of 300 mm.

The Parallel Transmission of Power and Data With the Shared Channel for an Inductive Power Transfer System

A shared physical communications channel is designed and implemented in this paper for inductive (contactless) power transfer (IPT) applications, wherein data are transferred without interfering power transfer, and, thus, maintained the efficiency of the IPT system. The channel is made of coupling coils, which are used to control the system and to transfer data bidirectionally at the rate of 19.2 Kb/s. To make the system work in two relatively independent modes, the wave trappers (passive bandpass and band-reject filters) are added into the system, and an integrated mathematical model is established based on separate models of data and power transfer. The proposed method was tested on a laboratory scale prototype, and was proved to be reliable for the parallel transmission of power and data. Therefore, the proposed method can be used to improve performance of the IPT system by precise control due to communication between the primary side and the pickup side.

Examination of a Split Transformer Arrangement for the Inductive Link of Contactless Power Transfer Systems

In this work, a split transformer topology is proposed for use in a wireless electric vehicle charger. The topology presents desirable characteristics concerning minimization of the air gap, easiness of alignment, weight and cost. Comparison is performed with spiral topologies presented in relevant literature. The coupling coefficient of the system for various air gaps and misalignment conditions is extracted by 3D finite element simulations and experimentally validated by a 3 kW prototype inductive power transfer system. The magnetic field at nominal power of operation is also simulated for evaluation of the compliance to the human exposure limits.

Modeling Analysis of Contactless Power Transfer System for Rotary Ultrasonic Machining

In rotary ultrasonic machining (RUM), the traditional power transfer method was achieved by slip ring that cannot cope with high-speed rotary of the tool, which limits the machine potential of RUM. Based on the principle of electromagnetic mutual inductance and the technology of loosely coupled inductively power transfer (LCIPT), a contactless power transfer system (rotary transformer) is built for RUM to achieve its power transfer goal. Resonant Compensation technology is used to enhance the efficiency of the rotary transformer. And the performance of the rotary transformer is validated on Maxwell platform.

High-Order Resonant Converter Topology With Extremely Low-Coupling Contactless Transformers

Although a large number of typical resonant converter topologies have been developed for use in contactless power transfer applications, these topologies need to be precisely optimized to obtain maximum efficiency and maximum power transferring capacity. High-order resonant power converters with flexible designs are invariably required to develop energy-efficient and cost-effective converter systems. An ideal converter topology can contribute toward realizing efficient converter systems if it is capable of providing an optimized output that is insensitive to load variations, coupling coefficient, type of the wireless transformer used, and other operating conditions. This paper presents a new contactless power converter topology for a low-coupling (0.14) ferrite-core transformer that has low cost, small size, high efficiency, and a wide gap (20 mm). In addition, the merits and demerits of conventional converter topologies are studied herein, and results for these topologies are compared with those for the proposed converter topology.

Contactless Power Charger for Light Electric Vehicles Featuring Active Load Matching

Contactless power transfer technology is gaining increasing attention in city transportation applications because of its high mobility and flexibility in charging and its commensurate power level with conductive power transfer method. In this study, an inductively coupled contactless charging system for a 48 V light electric vehicle is proposed. Although this study does not focus on system efficiency, the generic problems in an inductively coupled contactless power transfer system without ferromagnetic structure are discussed. An active load matching method is also proposed to control the power transfer on the receiving side through a load matching converter. Small signal modeling and linear control technology are applied to the load matching converter for port voltage regulation, which effectively controls the power flow into the load. A prototype is built, and experiments are conducted to reveal the intrinsic characteristics of a series–series resonant inductive power charger in terms of frequency, air gap length, power flow control, coil misalignment, and efficiency issues.

Evaluation of Inductive Contactless Power Transfer Outlet with Coaxial Coreless Transformer

SUMMARYA contactless outlet for dc distribution systems is proposed. It uses an inductive contactless power transfer circuit with a series/parallel compensation circuit to prevent voltage fluctuation. However, the output voltage of the circuit rises in light load conditions. In this paper, the main circuit and control method for reducing the rise in output voltage and a method of estimating the output voltage are presented. The proposed circuit and methods were verified and evaluated experimentally using feedback control.

Modeling and analysis of eddy-current loss of underwater contact-less power transmission system based on magnetic coupled resonance

In this paper, we investigate the transmission mechanism and eddy-current loss of the contact-less power transmission (CPT) system in seawater environment. Contact-less power transfer could be achieved in the three following ways: magnetic coupling, magnetic resonance coupling, and microwave radiation. When the primary and secondary coils are in resonance, a channel of low resistance in the magnetic resonance coupling system is formed. Therefore, it is used for medium-distance power transmission and it has less restrictions on orientation, which means that it has wide applications in many scenarios. Moreover, contact-less power transfer is safer and more concealed than traditional plug power supply, especially in underwater vehicles. Firstly, the mathematical model based on the mutual inductance model is proposed for the CPT system in the air, then the frequency analysis of the CPT model as well as theoretical explanation of the splitting phenomenon is conducted, after that we consider the seawater effect on the mutual inductance coefficient. Secondly, we build a mathematical model of the eddy-current loss in seawater circumstance according to the Maxwell's equations, where we introduce an average magnetic induction in cross section, then derive an approximate formula through Taylor expansion, and analyze the relations between eddy-current loss and the physical parameters including coil radius, resonance frequency, transmission distance, and magnetic induction. According to the theoretical results, we optimize these physical parameters and then design a 754 kHz CPT system, thereafter we validate the CPT system both in the air and in seawater and find the difference between these two circumstances, and verify the relations between eddy-current loss and the physical parameters which are proposed in our theory. It can be learned from the experiment that when transmission distance is 50 mm and transmission power is 100 W in the air, the transmission efficiency is over 80%, and when transmission distance is 50 mm and transmission power is 100 W in seawater, the transmission efficiency is over 67%. Apparently, our magnetic-resonance-coupling-based CPT system has potentials serving as an underwater vehicle.

Broadband Material Characterization Method Using a CPW With a Novel Calibration Technique

When combining contactless power and data transfer, antennas are often placed near magnetic materials with unknown RF properties. While permittivity measurement methods for dielectric materials at RF frequencies are well established, methods for permeability measurement are relatively scarce and often cumbersome. We propose a versatile and easy-to-use method that is applicable to both dielectric and magnetic materials, which uses a coplanar waveguide structure to measure the complex permittivity and permeability in the 1–16 GHz range. We combine the Nicolson–Ross–Weir algorithm with a robust root selection and a conformal mapping method to extract the permittivity and permeability from the measurement data. Moreover, we propose a novel calibration method that uses a single reference dielectric to increase the accuracy of the measured permittivity significantly, even when measuring magnetic materials.

円形及びソレノイド型磁界結合方式非接触給電トランスと共用可能なHc型トランスの回路解析と性能評価

There are two types of the transformers in a contactless power transfer system: solenoid type (H-shaped) and circular type transformers. These two types of transformers are not compatible because their magnetic field structures are different. An Hc type transformer that is compatible with both transformer types has been proposed. The Hc type receiver adds a central magnetic pole by dividing the winding coil of the H-shaped receiver. The Hc type receiver can change the magnetic field structure by changing the connections of the divided windings and can receive power from both types of transmitters. In this study, we conducted a circuit analysis and evaluated the performance of the Hc type transformer.

Simulation and Optimization of Contactless Power Transfer System for Rotary Ultrasonic Machining

In today’s rotary ultrasonic machining (RUM), the power transfer system is based on a contactless power system (rotary transformer) rather than the slip ring that cannot cope with high-speed rotary of the tool. The efficiency of the rotary transformer is vital to the whole rotary ultrasonic machine. This paper focused on simulation of the rotary transformer and enhancing the efficiency of the rotary transformer by optimizing three main factors that influence its efficiency, including the gap between the two ferrite cores, the ratio of length and width of the ferrite core and the thickness of ferrite. The finite element model of rotary transformer was built on Maxwell platform. Simulation and optimization work was based on the finite element model. The optimization results compared with the initial simulation result showed an approximate 18% enhancement in terms of efficiency, from 77.69% to 95.2%.

Proposed Dynamic Contactless Power Transfer System

Since EV has the subject that a vehicles price with the long charging time with short mileage is high, it has not resulted in full-scale spread. The dynamic contactless power transfer system which performs an electric power supply on the vehicles under drive is expected as a means to solve the subject of EV. There are some problems resulting from the loop coil being used for the dynamic contactless power transfer system. The first problem is that it is incompatible with the stationary contactless power transfer system. In the stationary contactless power transfer system, since the ground coil of a different type from a loop coil is adopted, the vehicles must install two coils, under parking and driving. The space reservation for installing a coil by passenger car is difficult, and is not practical. The second problem is that the leakage flux and the radiation noise become large. The third problem is that a construction period and a repair period become long. In this paper, the dynamic contactless power transfer system which has the following features is proposed and a simulation and an experimental result show the validity. The feature of the system to propose is as follows. The ground coil of a proposal system is the same as that of the stationary contactless power transfer system, and electric supply becomes possible also while parking also driving. The proposal system consists of same ground side coil as the stationary contactless power transfer system, and a vehicles side coil, and leakage flux and a radiation noise are small. Since a proposal system vacates an interval and installs a ground coil, construction period shortening and price reduction of a system of it are attained.

Enhancement of Plasma-Driven System With Piezoelectric Transformer-Based Feedback Control Approaches and a Contactless Power Source

This paper proposes a plasma-driven system with piezoelectric transformer-based feedback control approaches along with a contactless power source. The research is motivated because many plasma-driven circuits employed the bulky components as resonant circuit and current feedback sensors. Hence, this study proposes to utilize one piezoelectric ceramic transformer to serve for both resonance tank and feedback devices in order to achieve low cost and design simplification. Moreover, since the plasma discharge often suffers the problem of high humidity and particle-polluted environment, a contactless power transfer circuit integrated with a high-frequency coil is developed as the power source, by which the electrode damage can be better prevented. To reach a better discharge quality and own a higher flexibility of regulating power, the study also completes a constant-power control mechanism and a phase-locked loop control. Both software simulations and hardware realization have been accomplished. Analysis results and experimental outcome help validate the practicality of the proposed approach.

LCL Resonant Compensation of Movable ICPT Systems with a Multi-load

Compared to LC resonance, LCL resonance has distinct advantages such as a large resonant capability, low voltage and current stresses of the power device, constant voltage or current output characteristics, and fault-tolerance capability. Thus, LCL resonant compensation is employed for a movable Inductive Contactless Power Transfer (ICPT) system with a multi-load in this paper, which achieves constant current output characteristics. Peculiarly, the primary side adopts a much larger compensation inductor than the primary leakage inductor to lower the reactive power, reduce the input current ripple, generate a large current in the primary side, and realize soft-switching. Furthermore, this paper proposes an approximate resonant point for large inductor-ratio LCL resonant compensation through fundamental wave analysis. In addition, the PWM control strategy is used for this system to achieve constant current output characteristics. Finally, an experimental platform is built, whose secondary E-Type coils can ride and move on a primary rail. Simulations and experiments are conducted to verify the effectiveness and accuracy of both the theory and the design method.

Output voltage control of inductive power transfer system based on extremum seeking control

Inductive power transfer (IPT) system facilitates contactless power transfer across an air-gap through weak magnetic coupling. The controller design for IPT system is very difficult owing to load and system parameter variations, very high operation frequency, strong non-linearity and discreteness. In this study, an extremum seeking control (ESC) strategy is proposed for the output voltage control of LCL-type IPT system. The design of ESC strategy is regarded as a numeral optimisation problem; therefore, a parallel chaos optimisation algorithm will be applied to solve this numeral optimisation problem. In every iterative step of the ESC, the optimal target state is derived from extremum seeking sequence, which drives the operating conditions of system approaching to the target state with good performance. Several simulations and experiments are used to test the performance and the robustness of the proposed ESC strategy for IPT application.