Iron Core Coil Research Articles

Measurement of Knee Extensor Torque During Repetitive Peripheral Magnetic Stimulation: Comparison of the Forces Induced by Different Stimulators.

To investigate the factors that induce strong contractions during repetitive peripheral magnetic stimulation (rPMS) and compare the muscle torque induced by two stimulators (Stim A and Stim B) with different coil properties. rPMS was applied to the right vastus lateralis of 30 healthy young adults. Stim A contained a 10.1 cm2 rectangular iron core coil, while Stim B contained a 191 cm2 round coil. The knee extensor torque (KET) induced by rPMS at 30 Hz was measured isometrically and divided by the maximum voluntary contraction (MVC) to obtain a relative value of MVC (%MVC). KET at 100% intensity of Stim A (A100%, 1.08 T) was compared to those at 100% or 70% intensity of Stim B (B100%, 1.47 T vs. B70%, 1.07 T). Additionally, we conducted a comprehensive literature search for studies that measured the KET during rPMS. Both the mean values of %MVC using B100% and B70% were significantly greater than that using A100%. Furthermore, the KET induced by Stim B was found to be larger than that described in previous reports, unless booster units were used to directly stimulate the main trunk of the femoral nerve. Stim B induced a stronger muscle contraction force than Stim A did. This may be because the larger the coil area, the wider the area that can be stimulated. Additionally, a circular coil allows for deeper stimulation.

Insertion Performance Study of an Inductive Weft Insertion System for Wide Weaving Machines

Wide weaving machines traditionally enhance the weaving width by increasing the shuttle’s initial velocity. However, this approach introduces challenges like pronounced equipment vibration, elevated noise levels, heightened energy consumption, and a reduced lifespan. Moreover, its efficacy in significantly widening fabric is constrained. Addressing these concerns, this paper proposes a wide-width warp insertion solution that involves driving the high-temperature superconducting shuttle to achieve high-speed horizontal flight through a traveling magnetic field. The inductive weft insertion system structure of wide weaving machines comprises an insertion guideway with an iron core and wound electromagnetic coils. The shuttle consists of a high-temperature superconducting block and a conductive plate, serving as the driving element. By establishing the equivalent circuit of the weft insertion guideway and the suspended shuttle, the calculation formula for the dynamic driving performance of the weft insertion guideway is obtained. Utilizing a transient 3D magnetic field simulation model, the impact of parameters like the current frequency, shuttle conductive plate thickness, and suspension gap on weft insertion performance is explored. Successful wide-width weft insertion motion is achieved by controlling coil input current parameters. Finally, an experimental platform is constructed to validate the correctness of the weft insertion system structure and simulation model through practical experiments.

DISTRIBUTION TRANSFORMER LIFE LOSS ANALYSIS ON JTM 20 KV DUE TO AMBIENT TEMPERATURE AND LOADING

A continuously operating transformer will inevitably undergo a temperature rise, with the iron core and copper coil as the primary sources of heat generation. The maximum temperature occurring in these components, also known as the hottest spot temperature, is the hottest point. It is essential to maintain a regular flow of temperature within safe limits to prevent any damage. The objective of this study is to estimate the remaining life of the distribution transformer at Tanjungpura University by analyzing its life shrinkage under JTM 20 kV's ambient temperature and loading conditions. To achieve this, transformer loading and top oil temperature were measured for one week. The Montsinger equation was utilized for calculating the transformer aging rate, while a service life of 20 years was assumed as per IEC 60354. Based on findings from research conducted at 4 locations, it was observed that the transformer experiences varying loads with temperature increases exclusively on weekdays from Monday to Friday. The age shrinkage values for each transformer were as follows: 0.0728 p.u, 0.0493 p.u, 0.0044 p.u, and 0.0043 p.u. Considering these research outcomes, the estimated remaining lifespan of the Tanjungpura University distribution transformer is long, and the transformer is in good condition.

Magnetic field simulations of the GOLEM tokamak via the NICE code

In this paper, the direct and inverse equilibrium computation mode of the NICE code is put into operation for the case of the GOLEM tokamak. This enables, for the first time, simulations of GOLEM's magnetic field. The computation mode put into operation simulates the magnetohydrodynamic equilibrium of a tokamak plasma based on a given plasma position or given currents in poloidal magnetic field coils. In order to set up NICE, a virtual model of GOLEM is introduced that includes axially symmetrical approximations of GOLEM's iron core and primary transformer coils. The results of NICE simulations are compared with experimental measurements, and it is shown that NICE simulations produce plasma equilibrium configurations typical for GOLEM. Nevertheless, a more detailed validation of GOLEM's virtual model and of the results of NICE simulations is to be performed in the future.

Research on Motion Characteristics of Circuit Breaker Electromagnet in Different Conditions

The electromagnet is an important component of the circuit breaker operating mechanism. The stable work of the circuit breaker depends on the normal work of the electromagnet. In order to study the operation characteristics of the circuit breaker electromagnet, an electromagnet simulation model is established to analyze the action of the moving iron core and the coil current under the normal operation of the electromagnet. On this basis, the change of the moving iron core and the coil current under typical faults, such as the moving iron core jamming and coil voltage reduction, has also been studied. What’s more, the changes in the coil current under normal and fault conditions have been analyzed.

Design and Analytical Magnetic Modeling of a Spherical Motion Generator With Multi-DOF Electromagnetic Actuation

This article proposes a novel spherical motion generator with integration of multi-degree-of-freedom actuation which brings out a more compact and flexible structure. The actuation is implemented by electromagnetic driving principle, and the spherical rotation is generated by the interaction between the iron-core coils and skewed stator permanent magnets, which helps increase the torque output. The magnetic field model is formulated analytically and validated using finite-element analysis. Finally, the cogging torque is modeled and the skewing of permanent magnets is discussed.

Sliding-mode control design of a slotless self-bearing motor

Scientists have explored and are studying a slotless self-bearing motor, an electric motor with a magnetically integrated bearing function. As a single actuator, it can provide both levitation and rotation. This article will show a slotless self-bearing motor with a stator that does not have an iron core but six-phase coils. A permanent magnet and an enclosed iron yoke make up the rotor. To regulate the rotational speed and radial location of the rotor, magnetic forces created by the interaction between stator currents and the magnetic field of permanent interest are investigated. This research also includes a slotless-bearing motor mathematical model and control approach. This motor is investigated by combining an AC motor with a magnetic drive to achieve the essential design criterion and low cost. The magnetic force and moment characteristics are theoretically analyzed, and a control technique is proposed. Sliding-mode control (SMC) is a control method that is simple, effective and utilized to serve the control system for approaching the reference value, as stated in this study. It's also commonly used to manage the motor's position and speed. The findings were built and evaluated using MATLAB/Simulink confirmed analytical results to prove the recommended control approach.

Optimal design of transcranial magnetic stimulation coil with iron core

Objective. Iron core coils offer a passive way to increase the induced electric field intensity during transcranial magnetic stimulation (TMS), but the influences of core position and dimensions on coil performance have not been elaborately discussed before. Approach. In this study, with the basic figure-of-eight (Fo8) and slinky coil structures, iron core coil optimization is performed with the finite element method considering core position and dimensions. A performance factor combining performance parameters, including the maximum induced electric field, stimulation depth, focus, and heat loss, is utilized to evaluate the comprehensive coil performance. Main results. According to the performance factor, both iron core coils obtain the best overall performance with a fill factor 0.4 and the two legs of the iron core close to the inner sides of the coil. Finally, three prototypes are constructed—the basic, optimized, and full-size slinky iron core coil—and magnetic field detection demonstrates a good agreement with the simulation results. Significance. The proposed systematic optimization approach for iron core coil based on Fo8 and slinky basic structure can be applied to improve TMS coil performance, reduce power requirements, and guide the design of other iron core TMS coils.

Design and Fabrication of a Magnetic Actuator for Torque and Force Control Estimated by the ANN/SA Algorithm.

Magnetic manipulation has the potential to recast the medical field both from an operational and drug delivery point of view as it can provide wireless controlled navigation over surgical devices and drug containers inside a human body. The presented system in this research implements a unique eight-coil configuration, where each coil is designed based on the characterization of the working space, generated force on a milliscale robot, and Fabry factor. A cylindrical iron-core coil with inner and outer diameters and length of 20.5, 66, and 124 mm is the optimized coil. Traditionally, FEM results are adopted from simulation and implemented into the motion logic; however, simulated values are associated with errors; 17% in this study. Instead of regularizing FEM results, for the first time, artificial intelligence has been used to approximate the actual values for manipulation purposes. Regression models for Artificial Neural Network (ANN) and a hybrid method called Artificial Neural Network with Simulated Annealing (ANN/SA) have been created. ANN/SA has shown outstanding performance with an average R2, and a root mean square error of 0.9871 and 0.0153, respectively. Implementation of the regression model into the manipulation logic has provided a motion with 13 μm of accuracy.

A Radial-flux Permanent Magnet Micromotor with 3D Solenoid Iron-core MEMS In-chip Coils of High Aspect Ratio

Because of the difficulty in fabricating iron-core solenoid coils by micro electro-mechanical system (MEMS) processes, existing micromotors typically have an axial-flux structure with planar spiral coils or air-core solenoid coils. However, solenoid iron-core microcoils have a higher inductance and a lower magnetic resistivity than spiral coils and air-core solenoid coils. In this study, a radial-flux permanent magnet (PM) micromotor with 3D iron-core MEMS in-chip coils of high aspect ratio was designed and fabricated. The three-phase PM brushless direct current (BLDC) micromotor has four Nd-Fe-B magnet poles on a steel rotor and six solenoid Cu coils of high aspect ratio (coil height/line width = 14) in the silicon stator fabricated using MEMS processes. Iron cores were inserted into the coils, and a low-resistivity magnetic circuit was established. At 100 Hz, the inductance of a 15-turn coil was 13.2μH. The coils were embedded tightly in the silicon substrate, resulting in a good heat dissipation performance and thus a high current-carrying capacity. The hexagonal sheet-type micromotor weighed 2.25 g with a volume of 586.5 mm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> before bearing packaging. The modeling results showed that at 10000 rpm, the torque was 676μN·m and the power density was 314 W/kg. This micromotor incorporates a conventional large-scale BLDC motor structure and the proposed design will help improve the power density and efficiency of micromotors, thereby broadening their application prospects.

AC Losses in HTS Coils of Superferric Dipole and Combined-Function Magnets

A three-dimensional electromagnetic field analysis model was developed to estimate ac losses in high-temperature superconductor (HTS) coils composing superferric magnets for rapid-cycling synchrotrons. The influence of magnetized iron yokes in the superferric magnets on distributions of magnetic flux density in HTS coils was considered as externally applied magnetic flux density to HTS coils in the analysis model. We carried out the ac loss calculations using the models for two superferric magnets having different iron core and HTS coil geometries. The ac loss density distribution in the HTS coils and overall ac losses of the superferric magnets were compared.

Dynamics and power generation of wave energy converters mimicking biaxial hula-hoop motion for mooring-less buoys

In this study, a two-degree-of-freedom (2-DOF) wave energy converter (WEC) composed of an eccentric dual-axis ring and power generators using circular Halbach array magnetic disks and iron-core coils was developed. The 2-DOF WEC was designed to convert kinetic energy from the pitching, rolling, and heaving motions of a mooring-less buoy. The eccentric dual-axis ring with appropriate weighting conditions enhanced power generation by revolving in biaxial hula-hoop motion, because it exhibited a higher angular velocity than when in swing motion. Kinetic equations for the biaxial eccentric dual-axis ring mounted on the buoy were derived using the Lagrange–Euler equation. Furthermore, weighting conditions of the eccentric dual-axis ring for biaxial hula-hoop motion were determined in accordance with frequency and amplitude of regular buoy motion. The magnetic flux density, cogging torque, and electromagnetic damping of the magnetic disk were evaluated using magnetic field strength simulations and Faraday's law of induction. The 2-DOF WEC prototype was implemented, and biaxial hula-hoop motion was observed in a wave flume test. An output power of 0.56 W was generated for the primary frequency of buoy motion from 0.7 to 1.0 Hz. Results indicate the WEC is feasible as a sustainable power source for sensors on buoys.

Inductance calculations for coaxial iron‐core coils shielded by cylindrical screens of high permeability

Coaxial iron-core coil system shielded by a magnetic screen is a complex model for analytical calculation, because a complicated boundary value problem must be tackled for obtaining inductances of the coils in this situation. Truncated region eigenfunction expansion method is a suitable way to work out such a problem containing complex boundary conditions. Three different models are taken into consideration in this study. Starting with coil system shielded by two infinitely large plates, the basic steps of the proposed method are introduced carefully. Then the relevant techniques and conclusions are applied to the iron-core coils shielded by a fully enclosed cylindrical screen of high permeability and a lidless one. The effectiveness of the proposed method is verified by comparing with finite element method software and experiments. From relevant data, it is evident that the proposed method is much faster and can be easily used for forecast and evaluation of new schemes in device design process.

Mass reduction of superconducting power generators for large wind turbines

High temperature superconductors (HTS) enable very compact electric machines with high power density. Here, an HTS power generator based on authors’ previous double claw pole design is studied and improved. The original design of the double claw pole machine features a stationary field core to provide support and access to the superconducting field winding and its cryostat. It does not serve any other purpose. However, a homopolar field passes through it. The improvement was made to replace the field core by iron-cored copper coils, creating an inner stator within the generator to increase the electric loading. Through this step, the power output of the generator was increased from 10 to 11.6 MW, increasing the power density from 54.28 to 63.54 W/kg while maintaining the same outer diameter.

Diagnostic approach in assessment of a ferroresonant circuit

This paper presents possibilities offered by a diagnostic system called FeD. The system is completely original; it has been developed by the authors on the basis of Arduino platform. The system has been designed to perform and record measurements and to carry out different numerical operations. The real-time function for several operations is incorporated in this system. The necessary input data for the system consist of the electrical voltage waveforms only. Rescaled voltage quantities can be displayed, measured, recorded or computed in any chosen way. The system has been developed particularly for measurements and computations in the ferroresonant circuits. The strongest part of the system is its versatility. It works with a standard PC and supports a universal connection (USB standard). This is undeniably a cost-wise solution. Driving and control of the system functions are carried out using the authors’ original software implemented in SciLab environment. This is free software, similar to and compatible with other existing CAD programs such as Octave and MATLAB. The obtained data, scripts and results can be freely transferred between them. The program is equipped with a transparent GUI. The need of constructing a special system to diagnose the ferroresonant circuit has emerged during earlier ferroresonance analyses and computations. Every ferroresonant circuit requires specific kind of diagnostics to estimate and display its base features in order to determine the best scientific approach to the problem. The ferroresonance phenomenon belongs to the domain of nonlinear problems. Its analysis requires excellent skills in mathematics and physics as well as computer science. Moreover, this subject also requires specialized engineering knowledge, particularly in the field of power engineering and power system equipment. Modern mathematical models and analyses used in ferroresonant computations are quite accurate; however, in case of a common user, they are often difficult to understand or implement. This paper provides full description of construction, features and test results of the developed hardware/software system designed for diagnostics of ferroresonant circuits. The test circuit case study has been performed in the entire power supply range. Results of measurements and computations as well as screenshots captured from authors’ original software are shown in different figures. The developed software and recorded data have been finally used in modeling and further simulations. During this, the application of the fractional derivative iron core coil model to ferroresonance analysis has been shown. The waveforms obtained from computer simulations have been compared with those obtained from measurements performed in the test circuit.

A DC Voltage Swell Compensator Based on SMES Emulator and Lead-Acid Battery

The fast-response feature from a superconducting magnetic energy storage (SMES) device is favored for suppressing instantaneous voltage and power fluctuations, while the low-cost feature from a conventional battery energy storage (BES) device suits to achieve long-time voltage and power compensations in the power distribution and utilization systems. This paper investigates a new dc voltage swell compensating scheme by using an SMES-BES-based hybrid energy storage technology. In the preliminary tests, an iron-core copper coil is used to imitate high-temperature superconducting inductor, and this SMES emulator is, then, combined with a lead-acid battery to form a dc voltage swell compensator device. The experimental results demonstrate the feasibility of this SMES-BES-based dc voltage swell compensator to avoid the initial impulse charging current for the lead-acid battery and to extend the steady compensating time duration for the SMES simultaneously.

Inductance calculations for coils with an iron core of arbitrary axial position

ABSTRACTA semi-analytical method is proposed to calculate the magnetic field and inductances of axisymmetric iron-core coils. A group of source functions are introduced to simplify the formulas and accelerate calculation. Compared to previous researches, with the help of the source functions, the relative locations of the coil and the core in axial direction can be arbitrary, which extend the application range of the method. The results evaluated by the proposed method are compared with those given by finite element method (FEM), from which it is confirmed that the proposed method is effective and much faster than FEM simulations under the same calculation accuracy.

Development of a Coil Driver for Magnetic Manipulation Systems

Pulsewidth modulation (PWM) is the most commonly used technique to drive electromagnetic coils in magnetic manipulation systems. Relatively low PWM frequencies generate high-magnitude current ripple and magnetic field fluctuation. In this letter, coils are powered by a driver at PWM frequencies close to their self-resonant frequencies to generate high-frequency magnetic fields and minimize current ripple and magnetic field fluctuation. In order to protect the driver against the penetration of stray electromagnetic and magnetic fields, a multilayer shielding enclosure is employed. The coil driver is used to study the effect of varying PWM frequencies on current, magnetic field, and ohmic loss using Helmholtz, air, and iron core coils. The current ripple magnitude is significantly minimized when the coils are driven at PWM frequencies close to their self-resonant frequencies. This results in reduction of magnetic field fluctuation and provides more accurate measurement of magnetic field magnitude. Our experiments show that increasing the PWM frequency from 100 Hz to 25 kHz decreases the current ripple and magnetic fluctuation by two orders of magnitude, with a negligible effect on the ohmic loss.

Impedance of iron-core electric coils

It can readily be demonstrated that when a low frequency alternating voltage is applied to an iron-core coil the impedance is much higher than the direct current resistance of the coil. To understand how the high level of impedance arises it is necessary to explain how magnetic and electrical induction give rise to a current in the coil that opposes (i.e. is out of phase with) the current generated by the applied voltage. This paper shows how the high impedance can be explained by sequential processes of magnetic and electrical induction, and presents a mathematical derivation of the equation for the current in a coil based on Maxwell’s equations. The paper introduces the concept of inductive resistance which, together with inductive reactance, gives rise to the high impedance.The paper also considers the phase angle by which the current in an iron-core coil lags the applied voltage, and concludes that, in the absence of factors causing energy losses and waveform distortions, the lag angle must be less than 45°. It is shown that hysteresis increases the lag angle.

Performance Improvement of a Magnetized Coaxial Plasma Gun by Adopting Iron-Core Bias Coil and Pre-Ionization Systems

Performance Improvement of a Magnetized Coaxial Plasma Gun by Adopting Iron-Core Bias Coil and Pre-Ionization Systems