Coil Voltage Research Articles

Combining Magnetostriction with Variable Reluctance for Energy Harvesting at Low Frequency Vibrations

In this paper, we explore the benefits of using a magnetostrictive component in a variable reluctance energy harvester. The intrinsic magnetic field bias and the possibility to utilize magnetic force to achieve pre-stress leads to a synergetic combination between this type of energy harvester and magnetostriction. The proposed energy harvester system, to evaluate the concept, consists of a magnetostrictive cantilever beam with a cubic magnet as proof mass. Galfenol, Fe81.6Ga18.4, is used to implement magnetostriction. Variable reluctance is achieved by fixing the beam parallel to an iron core, with some margin to create an air gap between the tip magnet and core. The mechanical forces of the beam and the magnetic forces lead to a displaced equilibrium position of the beam and thus a pre-stress. Two configurations of the energy harvester were evaluated and compared. The initial configuration uses a simple beam of aluminum substrate and a layer of galfenol with an additional magnet fixing the beam to the core. The modified design reduces the magnetic field bias in the galfenol by replacing approximately half of the length of galfenol with aluminum and adds a layer of soft magnetic material above the galfenol to further reduce the magnetic field bias. The initial system was found to magnetically saturate the galfenol at equilibrium. This provided the opportunity to compare two equivalent systems, with and without a significant magnetostrictive effect on the output voltage. The resonance frequency tuning capability, from modifying the initial distance of the air gap, is shown to be maintained for the modified configuration (140 Hz/mm), while achieving RMS open-circuit coil voltages larger by a factor of two (2.4 V compared to 1.1 V). For a theoretically optimal load, the RMS power was simulated to be 5.1 mW. Given the size of the energy harvester (18.5 cm3) and the excitation acceleration (0.5 g), this results in a performance metric of 1.1 mW/cm3g2.

Efficiency Optimization of LCL-Resonant Wireless Power Transfer Systems via Bidirectional Electromagnetic–Thermal Coupling Field Dynamics

This paper delved into the thermal dynamics and stability of Wireless Power Transfer (WPT) systems, with a focus on the temperature effects on the coil structure. Using the Finite Element Method (FEM), this study investigated both unidirectional and bidirectional coupling field simulations, assessing their impacts on the transmission efficiency of LCL-resonant WPT systems. The boundary conditions and processes of the electromagnetic–thermal coupling field related to coil loss were analyzed, as well as the dynamic thermal balance in the bidirectional coupling field model. It was found that there is a significant temperature variation across the coil, with the highest temperatures at the central position and the lowest at the edges. This temperature rise notably changed the electrical parameters of the system, leading to variations in its operating state and a reduction in transmission efficiency. A constant coil voltage control strategy was more effective in mitigating the temperature rise compared to a constant coil current strategy, providing valuable insight for enhancing the efficiency and stability of WPT systems.

The Effect of Field-Dependent $n$-Value on Screening Current, Voltage, and Magnetic Field of REBCO Coil

The Effect of Field-Dependent $n$-Value on Screening Current, Voltage, and Magnetic Field of REBCO Coil

Computational study of the effect of the number of splitter plates considering blow-out coil voltage in arc chamber of moulded case circuit breaker

To attain current limitation in low voltage circuit breaker (LVCB) apparatus, the approach involves elevating the arc voltage. This improvement is realised primarily in the arc chamber's splitter plates because of the higher drop voltages at the anode and cathode sheath areas. One of the most crucial ways to better describe arc behaviour in LVCB is to account for voltage in the vicinity of the electrodes. To reduce the current, LVCB works by raising the arc voltage. Voltage is raised in several ways, including increase in losses, elongating the arc, and multiplying the splitter plates. The aim of this research is to present readers with an additional technique for analysing electric arcs in moulded case circuit breaker (MCCB) which is one of the types of low voltage circuit breakers which is used to prevent overload and short circuit in electrical systems. 2-D model of MCCB with splitter plate has been developed and simulated using ANSYS software. Simulation results with the effect of increase in the number of Splitter plates considering blow-out coil voltage in arc chamber has been discussed. Modelling and simulation technologies provide the mechanism through which this understanding may be attained.

Design and Non-Linearity Optimization of a Vertical Brushless Electric Power Steering Angle Sensor.

This paper presents the design and the non-linearity optimization of a new vertical non-contact angle sensor based on the electromagnetic induction principle. The proposed sensor consists of a stator part (with one solenoidal excitation coil and three sinusoidal receiver coils) and a rotor part (with six rectangular metal sheets). The receiver coil was designed based on the differential principle, which eliminates the effect of the excitation coil on the induced voltage of the receiver coil, and essentially decouples the excitation field from the eddy current field. Moreover, the induced voltages in the three receiver coils are three-phase sinusoidal signals with a phase difference of 10°, which are linearized by CLARK transformation. To minimize the sensor non-linearity, the Plackett-Burman technique was used, which identified the stator radius and the rotor blade thickness as the key factors affecting the sensor linearity. Then, the particle swarm algorithm with decreasing inertia weights was utilized to optimize the sensor linearity. A sensor prototype was made and tested in the laboratory, where the experimental results showed that the sensor non-linearity was only 0.648% and 0.645% in the clockwise and counterclockwise directions, respectively. Notably, the non-linearity of the sensor was less than -0.696% at different speeds.

A Natural Position Observer With Vertical Detection Coil for FSCW Machines

This paper presents a sensorless control strategy using the novel detection coil for permanent magnet synchronous motor (PMSM) with fractional slot concentrated winding (FSCW). In order to eliminate the armature component in the coil voltage, the detection coil distribution is determined based on the analysis of synchronous inductance and leakage inductance for FSCW machines. Hence, the rotor position and angular velocity are estimated from the terminal voltage of detection coil, without any knowledge of motor parameters. Both finite element analysis (FEA) results and experiments are carried out to prove the effectiveness of the proposed method at steady and transient states.

Realization of a Three-Switch Leg/Phase Inverter for Nine-Phase Variable Pole– Phase Induction Machine With Phase Grouping Concepts

In this paper, a 3-switch leg/phase inverter topology is realized for 9-phase variable pole-phase induction motor (9Ph-VPIM) drives. The 3-switch legs (3SL) in the proposed inverter are controlled with two non-intersecting phase shifted references to achieve a 3-level voltage excitation for each phase winding. These two non-intersecting references per leg limit the possible modulation index (MI) and may require a higher DC link voltage. The split winding concept and the phase grouping solutions are used to enhance the MI. In the split winding concept, phase winding of the <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2n</i> pole machine is divided into <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">n</i> number of distinct windings and excited with the same voltage for attaining a uniform air gap flux. These coils are called cognate voltage coils (CVC). With these CVCs, different possible groupings are proposed to enhance the MI of a proposed 3SL/phase inverter. The symmetrical and efficient phase grouping solutions are analyzed and tested with an improved modulation index. Moreover, the proposed 9Ph-VPIM drive is controlled with carrier-based 3-φ SVPWM to further enhance the DC link voltage utilization. The proposed inverter will feed the effective phase by a 3-level voltage with suppressed harmonics resulting in a superior torque ripple. The proposed 3SL/phase inverter fed 5-hp 9Ph-VPIM drive is validated with the experimental prototype.

Design of a multi-modal sensor for the in-process measurement of material properties based on inductive spectroscopy

Ferromagnetic steel magnetic properties undergo isotropic and anisotropic changes during cold forming processes. Although their measurement provides an important basis for material property-controlled process control, it remains particularly challenging, as workpieces are subjected to several influencing effects, such as tilting and distance to the target. In this paper, we propose a robust contactless multi-modal sensor for the in-process measurement of material magnetic properties composed of a central excitation coil surrounded by eight receiving coils. The material magnetic permeability is measured based on a model-based evaluation of the central coil inductance spectrum compensating for the influence of the distance to the target. The sensor realizes a measurement of the magnetic anisotropy independently of the tilting effects based on an FFT-based analysis of the induced voltage in the peripheral coils. The sensor has been validated in a tensile test experiment on standard specimens. The measurement data of the tensile test reveal a systematic relation of permeability and magnetic anisotropy to the mechanical influences of stress and deformation. The measurements remained stable despite strong movements between the sensor and the target. A working distance increase of 80% resulted in variations of the magnetic permeability of only 3%. The observed changes in magnetic anisotropy are uncorrelated to tilting effects. Based on the investigation results a proposal for the design of an in-process measurement system is provided.

Method with reliable accuracy and fast speed for measuring operational current of HTS NI closed-loop coils in steady persistent-current-mode

This study proposes a method for measuring the operational current of high temperature superconducting (HTS) non-insulation (NI) closed-loop coils, which operate in the steady persistent-current-mode (PCM). HTS NI closed-loop coils are promising for many easily-quenching direct-current (DC) applications, where their performance is determined by magnetomotive forces, total number of turns, and dimensions. As the primary interface parameter in an application system, the operational current must be accurately and rapidly measured. Generally, this is achieved by dividing the measured magnetic field by the coil constant. However, even if the influence of the screening current induced field (SCIF) is not considered, existing methods for the coil constant may be disturbed by the performance and location of Hall sensors, or experience a long measuring period. Therefore, a relatively accurate and fast method is proposed in this study, which is based on adjusting the output current of the adjustable power supply and monitoring the coil voltage as an indicator. The proposed method was validated through experiments and simulations using an equivalent circuit model coupled with a finite element method (FEM) model, and its current accuracy can be equivalent to the resolution of the employed power supply. It was demonstrated that this method reduced the requirements for Hall sensor’s performance and location, and has a more reliable accuracy in contrast to the simulation method. Compared to the experimentally conventional method, the proposed method presents a significantly faster speed. The impact of the SCIF was considered and proven to be negligible for the tested pancake coils. Even for coils whose coil constant vibrates owing to the SCIF, this method can be adapted to directly measure various operational currents. Furthermore, it was demonstrated that the measurement error can be influenced by the current discrepancy among turns when the coil is not in the steady PCM, and a procedure for reducing this error was proposed.

Design of Track circuit parameter tester based on STM32 Microcontroller

To measure the electrical parameters of 25Hz phase-sensitive track circuit, a testing instrument with STM32 microcontroller as the control core is designed. It mainly uses the method of root mean square and fast Fourier transform to measure the effective value of the coil voltage of the track relay and the phase difference between the coil voltage of the track relay and the local coil voltage. The voltage waveform and calculation results are displayed on TFT-LCD, which has the advantages of simple structure, fast processing speed and high measurement accuracy. It is convenient for the daily detection and fault diagnosis of 25Hz phase-sensitive track circuit.

Frequency Tracking Method and Compensation Parameters Optimization to Improve Capacitor Deviation Tolerance of the Wireless Power Transfer System

Compensation capacitors are naturally susceptible to manufacturing defects and aging effects, leading to the degraded performance of a wireless power transfer (WPT) system. This paper focuses on the compensation parameters optimization during the design stage and control strategy during the operation phase to improve the inherent capacitor error tolerance of the WPT system. The Sobol sensitivity method is applied to rank the importance of deviations of three capacitors on the transfer characteristics, and then the method of tracking the secondary resonance frequency is proposed. The numerical method is applied to find the optimal compensation parameters, with the constraint that the output voltage change caused by the shift of the designed compensation condition is limited to be less than ±5%. Experimental results show that with the proposed frequency tracking method and compensation parameter optimization, the deviation tolerance index is decreased from 0.485 to 0.363, showing an improvement of 25.2%, and the minimum power factor is increased from 0.78 to 0.89. Besides, the characteristics of constant primary coil current and voltage gain are almost not affected.

Numerical simulation of magnetization induction coupled discharge plasma discharge process

Abstract First, this paper analyzes the plasma discharge and fluid model, and constructs the plasma discharge model by drift-diffusion approximation control equation, heavy particle component control equation, electric field distribution and volume force calculation, and plasma chemical kinetic model. Next, the coupling mechanism of inductively coupled RF plasma and its discharge characteristics are analyzed. Finally, the magnetized inductively coupled plasma discharge is simulated numerically. The results demonstrate that the current flowing on an inductor coil develops quicker at 0.045T and then calms down with an increase in the supplied constant dynamic magnetic field power, but the coil voltage exhibits the reverse effect.

Investigation of Surge Voltage Propagation in Inverter-Driven Electric Machine Windings

This paper investigates what parameters affect the voltage propagation pattern in inverter-driven electric machine windings and presents mathematical analysis of this pattern with experiment verification. This work provides a thorough understanding of the behavior of machine windings under surge voltage excitations. First, high-fidelity finite element (FE) models were constructed with various combinations of factors in random-wound stranded machine windings. These factors include various types of parasitic capacitances, parasitic inductances of parallel strands and different wire layouts in slots. The surge voltage distribution along the windings was simulated and compared among different cases to identify the key factors that affect this voltage propagation pattern. Subsequently, machine windings with both single-phase and three-phase structures were analyzed via equivalent circuits that were constructed with those key parameters. Then, the expressions of the coil voltage were derived in the Laplace domain. These expressions explicate the uneven surge voltage propagation pattern at various frequencies. Finally, for verification, both simulations and tests were conducted to analyze the surge voltage propagation in single-phase and three-phase windings.

Metal Object Detection With Detection Coils Perpendicular to Power Coils for Wireless Power Transfer Systems

In this paper, a metal object detection (MOD) method with detection coils perpendicular to power coils is proposed. Without a metal object, the induced voltage in the detection coils is ideally zero. When a metal object falls on the top of the Tx pad, An eddy current is induced and this eddy current in the metal object will induce a voltage in the detection coils. The proposed method can perform well with misalignments between the Tx and Rx pads. No adjustments are required for different winding positions. The concept is well verified with experimental results.

Axial Movement Effect on Voltage and Current Behaviors of Insert No-Insulation REBCO Pancake Coil

In 2017, an insert 12-stacked no-insulation (NI) rare-earth barium copper oxide (REBCO) magnet was used in the generation of a world-record DC magnetic field of 45.5 T. The experiment demonstrated its high thermal stability; however, NI REBCO pancake coils are facing mechanical problems. In such an ultra-high field, strong electromagnetic forces work on insert REBCO coils, in particular during sequential normal-state transitions. Strong forces may cause insert REBCO coils to deform and move. Some research revealed that some deformations and movements affected the coil voltages and the screening currents. Whereas, the coil movement in an ultra-high field has not been studied yet. Voltages and currents are induced by the movement of insert coils, and there is a possibility of degrading the coil stability. In this paper, we have investigated the electromagnetic behaviors during sequential normal-state transition, considering the coil movement due to strong axial forces. The electromagnetic behaviors are simulated using a radially-subdivided partial element equivalent circuit (PEEC) model coupled with mechanical movement analysis.

Sudden Discharging Tests and Overcurrent Tests of a 3T HTS Model Magnet for MRI Systems Equipped With Electrically Conductive Epoxy Resin

A 3 T HTS MRI model magnet equipped with conductive epoxy resin for quench protection was designed and fabricated in 2021 and the REBCO multicoil generated 3 T with 143 A stably with no abnormal voltages. In this coil, the electrically conductive epoxy resin is attached to the edge of the winding as a bypass circuit between turns so that the excessive current can flow across turns in the radial direction to suppress local heat generation automatically. However, when the voltage of the coil rises as a start point in a quench protection process, the DC power supply is shut down by a quench detector and the magnet is suddenly discharged. Then, part of the magnetic stored energy is consumed in the coil and the coil temperature increases, which suggests the load factor increases during the sudden discharging operation. In this study, the sudden discharging tests were performed, and the behavior of the coil voltages and temperatures was evaluated at 30 K and 40 K using the middle-scale REBCO coil that had large inductance and high stored energy (3 T, 91 H, 1 MJ). After that, the overcurrent tests were performed for the verification of the quench protection at 50 K. The coil temperature reached 72 K at maximum, however, thermal runaway was avoided and the REBCO coil was protected.

Misfire Detection Technology with Deep Neural Network Based on Ignition Coil Signals

&lt;div&gt;For achieving high efficiency and low exhaust emissions, engines need to be operated near the limits of stable combustion, such as lean or exhaust gas recirculation (EGR) conditions. Sensing technologies of the combustion state by existing engine components are of high interest. And the utilization of voltage and current signals from ignition coils is discussed in this article. The discharge channel of an ignition spark is strongly affected by flow variation and spark plug surface conditions, and the behavior of discharge channel stretching and restrike event can vary greatly from cycle to cycle. As a result, the effects of flow velocity, temperature, pressure, and electrode surface resistance are compounded in the voltage-current response, making it difficult to accurately detect the combustion state for each cycle by a threshold judgment process using a single feature value.&lt;/div&gt; &lt;div&gt;In this article, a method for inductively detecting misfires from voltage and current signals of ignition coils by applying deep learning image recognition is introduced. First, post-ignition for misfire detection is performed on the engine bench during the expansion stroke in an engine cycle, when the cylinder pressure is expected to differ between the combustion cycle and the ignition cycle, and the ignition coil voltage and current are measured. Next, a two-dimensional frequency distribution of voltage and current (discharge histogram) is created as an input image for deep learning, and the AlexNet model, which has been trained with more than one million images, is trained with images of the ignition and combustion cycles as a supervised learning. The accuracy of classification is then verified using a validation dataset. In addition, to making the deep learning model more explainable, the activation score distribution on the discharge histogram was visualized when the trained model judges the images, and the discharge characteristics that provided the basis for deep learning classifications were analyzed.&lt;/div&gt;

To the method for calculation of an electromagnetic vibrator

The paper considers the issues of calculating an electromagnetic vibrator designed to drive working bodies with reciprocating motion. The purpose of this work is to refine the mathematical model of electromagnetic vibrators and, on this basis, to propose the most rational parameters of their design and modes of use. Based on the initial parameters of the magnetic system of an alternating current electromagnet, the inductance and inductive resistance of the electromagnet winding are determined as a function of the air gap, as well as the current flowing through the winding under the action of the applied voltage and the magnetic flux excited by it. As a result, the force of attraction of the armature and the yoke of the electromagnet was determined, which is the perturbing force, the restoring force of the spring opposing it, and the resistance force of the medium, which is proportional to the speed of the armature. This made it possible to form a second-order differential equation, the solution of which was carried out using the Given-Odesolve computing unit of the Mathcad mathematical system. As a result, the dependence of the armature deviation from the neutral state on time and the influence on this dependence of both geometric and electrical, and operating parameters of the electromagnetic vibrator were obtained in graphical form. As a result, the analysis carried out in the work and the developed method for determining the output parameters of an electromagnetic vibrator allow, for specific initial geometric and physical parameters of the vibrator, to determine the shockless trajectory of the electromagnet armature, the frequency and range of oscillations, as well as the optimal frequency and supply voltage of the electromagnet coil. If necessary, make adjustments to the requirements specified by the technological object for the output parameters of the vibrator.

A numerical method to calculate screening current-dependent self and mutual inductances of REBCO coils

The screening current and its relaxation cause the variation of the self- and mutual inductances of REBCO coils—REBCO is one of the high-temperature superconductors. However, most studies of coil voltage analysis on a REBCO magnet, a stack of coils, have reported simulation results assuming invariant self- and mutual inductances so far. Although the conventional assumption of invariant inductances is still acceptable for fundamental coil voltage analyses, it can cause misleading conclusions due to inductive voltage errors when a precise coil voltage analysis is demanded. Hence, here we report a numerical method to calculate screening-current-dependent self- and mutual inductances of REBCO coils for advanced studies based on a lumped-circuit analysis model. In this work, we aim to investigate the inductance variation due to the screening current with a case study and discuss its effects on the coil voltage. We assume that there is a stack of 12 REBCO single-pancake coils. No transverse current in each coil is considered for simplicity. A numerical simulation of the current density in the magnet is performed, and then the inductances are calculated by considering the spatially non-uniform current density due to the screening current. From this case study, we confirm that the self- and mutual inductances are changed by up to 110% and 30% each. It is also confirmed that the discrepancy is notable at the beginning of the charge while marginal at the end. Finally, we discuss the effect of inductance variation on the quench voltage analysis.

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.