Coil Gap Research Articles

Multi-objective parametric optimization of driver-based electromagnetic sheet metal forming of SS304 using AA6061-T6 driver

This study uses statistical techniques to optimize the electromagnetic forming process for driver-based sheet metal forming with a flat coil. AA6061T6 sheet was used as a driver to form SS304 sheets. The optimization of maximum elongation, die fitting, maximum Lorentz force, and peak current was carried out. The results were verified through simulation which were in close agreement with the experimental results. The most influential factor was the voltage (C.R of 72.97%), followed by coil gap and SS304 sheet thickness (7.99 and 6.07%, respectively).

Investigation of rolling contact fatigue cracks using the transmitter-receiver eddy current testing under moving conditions

ABSTRACT Rolling contact fatigue (RCF) cracks online detection using eddy current testing (ECT) is in urgent demand. However, RCF cracks detection and evaluation in this way under moving conditions remains challenging due to the velocity effect in ECT. This paper aims to study the response of a transmitter-receiver eddy current probe to cracks under moving conditions and evaluate the depth and inclination angle of RCF cracks. In this paper, a high-speed eddy current testing system is developed to experimentally investigate the influence of coil gap, detection speed, and the lift-off on the eddy current probe’s response under moving conditions. In addition, the temporal and amplitude features of the eddy current signal are extracted to characterise the depth and inclination angle of the RCF cracks. The experimental results indicate the eddy current probe’s response can be improved by increasing the coil gap (coil centre distance) suitably, which can be done to compensate for the attenuation of the eddy current signal caused by detection speed and lift-off. The probe’s response hardly changes with an increase in detection speed when the driver and pick-up coils of the eddy current probe completely overlap. The crack depth and inclination angle can be evaluated under moving conditions.

Frequency selection for underwater wireless power transfer based on the analysis of eddy current loss

Wireless power transfer (WPT) technology is ideal for wireless charging of unmanned underwater vehicles (UUV). However, in underwater WPT systems, the eddy current loss (ECL) caused by the conductivity of seawater cannot be ignored. This paper obtains the expressions of the equivalent ECL resistance and mutual inductance by calculating the complex power generated by the current in the electric field. An intuitive circuit model is used to describe ECL and its superposition effect. Based on the system efficiency expressions, the influence of the medium conductivity, coil gap and operating frequency on the transmission efficiency is analyzed. Results show that there is an optimal frequency to achieve the maximum dc–dc efficiency in the seawater. Simulated and experimental results verify the validity of the method in calculating ECL and capturing the optimal transmission frequency.

走行中非接触給電システムのコイル搭載位置による走行時のギャップ変動影響の検証

走行中非接触給電システムのコイル搭載位置による走行時のギャップ変動影響の検証

Active Control Method Based on Equivalent Stiffness and Damping Coefficient for an Electromagnetic Isolation System

For improving the performance of an electromagnetic isolation system with reasonable parameters and avoid the parameter tuning problem of a PID controller, an active control method is put forward based on equivalent stiffness and damping coefficient. In this paper, the range of equivalent stiffness coefficient and damping coefficient of the electromagnetic force are calculated based on the required range of dynamic performance indexes. According to the nonlinear expression between electromagnetic force and coil current and gap, the relationships between the coil current and equivalent stiffness coefficient and damping coefficient are established. Then, the equivalent stiffness coefficient and damping coefficient can be satisfied by the controlled current in different gaps for meeting the required dynamic performance indexes. For reducing the maximum overshoot and the number of oscillations of the system, the active control method with the piecewise equivalent stiffness and damping coefficient is proposed based on the piecewise control strategy to realize the variable control parameters of the isolation system. Simulation and experimental results verify that the control method based on the equivalent stiffness and damping coefficient can obtain the desired dynamic performance indexes and the proposed control method with the piecewise strategy can not only reduce the setting time of the system, but also ensure the stability of the system.

Bidirectional DC–DC Wireless Power Transfer Based on LCC-C Resonant Compensation

A bidirectional dc-dc wireless power transfer (WPT) based on LCC-C resonance compensation is proposed in this article. For the power flowing from the primary side to the secondary side (P2S), the voltage source is converted to a current source (V-C) on the primary side and the current source is converted to a voltage source (C-V) on the secondary side. For the power flowing from the secondary side to the primary side (S2P), the V-C conversion occurs on the secondary side and the C-V conversion occurs on the primary side. The proposed bidirectional dc-dc WPT using LCC-C resonance compensation exhibits several advantages: 1) it operates in bidirectional power flow; 2) it prevents burn out of the coil when there is an open circuit on the load side or the coils are misaligned; and 3) it outputs a constant current (CC) or a constant voltage (CV). A hardware prototype is designed using the specification SAE-J2954, the operating frequency is 85 kHz, the maximum output power is 3.7 kW and the vertical distance for the coil gap is 15 cm. The experimental results verify that the proposed bidirectional dc-dc WPT performs as expected.

Vibration Control Method of an Electromagnetic Isolation System Based on LQR and Coevolutionary NGA

An electromagnetic isolation system can dynamically adjust the output characteristic parameters of the system in real time through the active control strategy, which has strong adaptability to the external environment. In order to control the electromagnetic vibration isolation system effectively, an active control method is presented based on the linear quadratic regulator (LQR) approach and the coevolutionary niche genetic algorithm (NGA). In this paper, the dynamical equation and state equation of the electromagnetic isolation system are built, which include the nonlinear relationship between electromagnetic force and coil current and gap. The LQR approach is employed to maintain a steady state of an isolated object on the vibration isolation system. Meanwhile, a coevolutionary niche genetic algorithm is put forward to optimize the parameters in Q and R matrices. Simulation and experimental results demonstrate that the electromagnetic isolation system with the LQR approach and coevolutionary NGA can effectively isolate the vibration and maintain a steady state for an isolated object in comparison with the passive isolation system.

Experimental investigation on structure parameters of E-shaped coil in magnetic pulse welding

ABSTRACTWelding coils conduct current and establish a magnetic field during the welding process, and its structure heavily affects the magnetic field and impact force distribution. The existing literature on coil development for sheet connection is extremely limited. This paper analyzes the effect of the E-shaped coil current return path and the corresponding simulation is carried out. The results reveal that the optimal coil gap is about three times that of the middle arm, and the welding effect of the optimized coil is better than the ordinary coil. And, the optimized coil can reduce the required energy and improve the efficiency. Furthermore, the coil height is not a significant factor.

Simulation study of an inductively coupled plasma discharge with different copper coil designs and gas compositions

The physical characteristics for the study of two-dimensional inductively coupled plasma (ICP) discharge with different designs of copper coil and gas composition are presented in this paper. And this numerical model is a typical inductively coupled plasma discharge. Compared with former publications studying in ICP discharge, our simulation results indicate some new discoveries. First, the inductive coil gaps are arranged at different distances and their physical properties are studied in argon environment. The maximum electron density, electron temperature and macroscopic gas temperature are obtained at the best coil gap distance for discharge. Then, the inductive coils on the quartz tube without changing the coil gaps between the coils are placed in different positions and the discharge properties are also studied in argon environment. The maximum electron density, electron temperature and macroscopic gas temperature are obtained in the best position for discharge respectively. Finally, the physical characteristics of the ICP discharge in different gas compositions (other physical parameters were unchanged) are studied and the related important chemical reactions are also been described. It is concluded that the best discharge effect of argon gas is obtained under the same discharge conditions.

Design and optimisation of mutual inductance based pulsed eddy current probe

High lift-off inspection arising from thick insulation and requirement to protect probe from weld zones are challenges to pulsed eddy current (PEC) testing. In traditional PEC probe with fixed coil gap, weakening interaction between probe and test sample as lift-off increases reduces sensitivity. To analyse this influence, numerical simulation and experiments on design and optimisation of driver-pickup PEC probes are carried out. Results validate that both coil gap and lift-off have significant effects on resultant mutual inductance of driver-pickup PEC probes above test samples. In addition, the probe sensitivity is enhanced at a higher lift-off when coil gap exceeds a certain value. The increase in detection lift-off with coil gap could be optimised.

A 2-kW, 95% Efficiency Inductive Power Transfer System Using Gallium Nitride Gate Injection Transistors

This paper presents an inductive power transfer (IPT) system targeting at electric vehicles (EVs) and hybrid EVs. IPT systems provide significant benefits over the conventional plug-in chargers. However, in order for IPT to be adopted for EV charging, efficiency is a key figure of merit, which needs to be achieved. This paper presents a high-frequency inverter using gallium nitride (GaN) power transistors that have the benefit of low on-resistance and gate charge to reduce the switching and conduction loss. The switching characteristics of the GaN GIT are studied, and the inverter is designed to ensure low switching losses while keeping overshoot and slew rates under control. An efficiency centric mode of operation is proposed to improve the efficiency of the system while ensuring sufficient power transfer. The system efficiency peaks at 95% at 100-kHz operation and 92% at 250-kHz operation for a coil gap of 80 mm at 2-kW output power. At a coil gap of 150 mm, the system obtains above 90% efficiency at 1.3 kW. The IPT system is compared with a similar system using SiC power transistors and outperforms it by 1% at 2 kW.

Coupled Analysis and Protection of the HTS DC Magnet for DC Induction Heater in Dynamic Disturbance

Designing a high temperature superconducting (HTS) DC induction heater requires the HTS magnet to be equipped with an HTS coil, iron core and air gap. A large amount of magnetic energy is stored in the iron core and must be transferred outside the magnet during system collapses. The nature of the operating conditions and dynamic heating processes make the magnet coil a substantial nonlinear inductive load for the power supply which can result in system collapse and potentially damage the peripheral circuit of the magnet. Therefore, a protection system is recommended for this magnet. This paper proposes an active protection system for a DC HTS induction heater composed of a magnet with an iron core and YBCO coated conductor (CC) tape. A Matlab/Simulink-based simulation model was coupled with a Comsol-based finite element method model to combine the electrical and electromagnetic characteristics to optimize the design configuration of the protection circuit. Experiments with different magnet operating currents and dump resistors were carried out to verify the feasibility of this proposed protection system for magnets with and without an iron core. The results show that the proposed scheme performs within desired specifications and that the dissipation efficiency and velocity vary depending upon different values of the dump resistor.

Quartz force sensor and facing spiral coils for noncontact detection

A noncontact detectable force sensor is a promising technique for monitoring the defects of a structural object, such as buildings and bridges, and medical surgery devices. In this study, the noncontact detectable force sensor with an AT-cut quartz crystal resonator and a pair of spiral coils is proposed. The thickness-shear mode is excited with energy trapping excitation. The resonant frequency of this vibration mode is a function of the applied external force because of the nonlinear elastic module. Then, from the resonant frequency change of the quartz crystal, the input force can be measured. Admittance characteristics of this sensor contained series and parallel resonance. We confirmed that noncontact detection of the resonant frequency change is possible by using two facing spiral coils. The coil gap effect could be eliminated by calculating the difference between the series and parallel resonant frequencies.

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

Sensitivity Study of Temperature Profile of 4340 Spur Gear Heated by Induction Process Using 3D Model

This paper presentsa sensitivity study using a Comsol3D model simulation for spur gear heated by induction process. Based on an adequate formulation and taking into account the material properties, a multi-physics 3D model is built to calculate the final temperature distribution determinate according the machine parameters and some geometrical factors (coil width and gap between coil and gear). Since the hardness profile is affected by thermal historic during heating, the surface temperatures are deeply analyzed versus the initial current density and the heating time using medium (MF) and high frequencies (HF). Finally, the sensitivity of hardness profile with the machine parameters variation isinvestigated using various statistical tools applied to the obtained results. The obtained results exhibits the main machine parameters and theirs effects on the hardness profile.

OPTIMIZED DESIGN PARAMETERS OF EDDY CURRENT BOBBIN PROBE FOR STEAM GENERATOR TUBE IN NPPS

The bobbin probe is now widely accepted as a basic and important ECT technique among various ECT techniques for steam generator tube integrity assessment that is practiced during each plant outage. The bobbin probe is also one of the essential components which consist of the whole ECT examination system, and provides us with decisive data for the evaluation of tube integrity in accordance with acceptance criteria described in specific procedures. Accordingly, the design of ECT probe is especially important to examination results because the quality of acquired ECT data is determined by the optimized probe design characteristics, such as coil geometry, electrical properties, operation frequency, and so on. In this study, the relationship between electric characteristic changes and differential coil gap variation for the optimization of the ECT probe signal was investigated. As a result, for the examination of volumetric flaws fabricated on the O.D. side of ASME type calibration standard, we propose that the best Lissajous signal for the examination will be obtained when the coil gap of differential bobbin probe is approximately 1.2 ~ 1.6 mm .

The Inductance Computation for the Passive Compulsator

In order to decrease the internal impedance of the passively compensated pulsed generator (or passive compulsator) and enhance its power density, air gap windings are generally selected as the armature winding of the passive compulsator, for its inductance is much lower than that of the general embedded windings in the machine slot. Due to that the peak power of an electromagnetic launcher system driven by a compulsator is simply determined by system impedance and the output voltage of the compulsator, it becomes necessary to gauge the total inductance of the air gap windings accurately with straight forward calculation, while neglecting the easily obtained resistance parameters, particularly in its design period for electromagnetic launchers. By taking into account the flux compression effects generated by the eddy current of the continuous conductive shield in the compulsator, the magnetic field of the armature coils in the air gap of generator is analyzed by Ampere's law. The analytical solution to the inductance of armature air gap coil is deduced. This one equation solution is used for re-designing a 25 MW compulsator with the final calculation result: 4.04 muH. The measurement on the compulsator (4.05 muH) verified the accuracy of the analysis equation.

Vapor Phase Growth of Carbon Microcoils / Nanocoils

The carbon microcoils and carbon nanocoils were prepared by the catalytic pyrolysis of acetylene under the Ni and/or Fe-containing catalysts, and the growth pattern, morphology and growth mechanism of the carbon coils were examined in detail. The inner coil diameter of carbon microcoils are of several µm and coil gap from zero to several µm. The inner coil diameter of carbon nanocoils are from zero to several ten nm and coil gap from zero to several nm. The carbon microcoils are generally of double helix coils such as DNA while carbon nanocoils were single helix coils such as α-helix proteins, with spring-like or twisted forms. A catalyst grain was usually observed on the tip of carbon coil. The carbon nanocoils are almost amorphous and can be graphitized by the high temperature heat-treatment.

変形D型超電導コイルの電磁力変形と機械損失の検討

It is important to understand the mechanical behaviors of large-scale SMES (Superconducting Magnetic Energy Storage) when attempting to develop a practical device with high reliability and efficiency. A FEM (Finite Element Method) simulation model developed for determining the nonlinear mechanical deformation of a modified D-shaped elemental coil with a Rutherford-type conductor for a 1kWh/1MW SMES was studied. The model uses nonlinear mechanical characteristics of the conductor measured by a bending test. The nonlinear characteristics of the conductor are roughly explained by the frictional slip between two layers in the conductor. In this paper, a certain coil gap between the conductor and support structure was taken into account for the FEM simulation model in order to examine the mechanical behaviors of the coil in detail. The FEM analysis results for the nonlinear deformation and mechanical loss of the coil were compared to those actually measured in a 1kWh SMES test. The results show a high correlation, which supports the validity of the analysis model.

Compact high performance speaker

A speaker has first and second annular magnets (1, 2) arranged concentrically with each other and connected by a shunt (3) at one end and a pole-defining structure (4, 5) at the other end to concentrate magnetic flux in a cylindrical voice coil gap (G). The shunt and pole structure are stacked such that the combined magnetic assembly has an opening (C) extending centrally therethrough. A voice coil (VC) rides in the cylindrical magnetic flux gap and its leads are brought out through the opening (C) to the other side of the magnet. When used with an enclosure, the diaphragm (D) of the speaker may communicate through the central opening with the volume of a tuned enclosure extending behind the speaker, or the opening may serve as a port of the enclosure, allowing further degrees of control over total acoustics. Shaped pole pieces each lying against one of the magnets together define a shallow voice coil gap of high flux density in which the field is efficiently focused.