Coil Voltage Research Articles

Study on current discrepancy and redistribution of HTS non-insulation closed-loop coils during charging/discharging and subsequent transient process toward steady-state operation

It has been previously demonstrated that currents in HTS non-insulation (NI) coils exhibit a discrepant distribution during charging and discharging. However, for NI closed-loop coils, novel phenomena that arose from the current discrepancy have not been fully studied, especially during transient processes after charging and discharging, or more strictly speaking, after the persistent current switch returns to the superconducting state. For example, in our project of a prototype maglev system, a rapid decrease in the magnetic field was observed immediately after charging, which could be easily misinterpreted as a sign of local damage. However, the subsequent stability of the magnetic field with the expected decay rate of 1 d−1 illustrated that there was no such damage. To address this issue, in this study, a NI closed-loop coil was fabricated and simulated by an equivalent circuit model (per 46 turns as a L–R circuit element and 20 elements in total for 920 turns) coupled with a 3D finite-element-method model. Simulated results were in reasonable agreement with experimental measurements, demonstrating a significant discrepancy in azimuthal currents during charging and discharging; this is essentially due to variations in inductances across each turn of NI coils. In addition, azimuthal currents may initially flow in the direction opposite to the coil voltage in turns with lower resistivity relative to other turns. In correspondence with the observed novel phenomena, after charging or discharging, azimuthal currents undergo redistribution until converging to a stable value, which exhibits a transient process and leads to a rapid decrease or increase of magnetic field in specific positions. The following issues were also discussed: (1) the judgement of operational current could be disturbed by the discrepant current distribution, due to its impact on the spatial magnetic field, not only for NI closed-loop coils but also for open-loop ones; (2) the non-uniformity of currents in NI closed-loop coils is lower, compared to that in open-loop ones with the same joint resistance and turn-to-turn resistivity distribution; (3) a new strategy with multiple charging processes is necessary for precisely charging NI closed-loop coils to the target current.

Compact multi-coil inductive power transfer system with a passive peak detector circuit for wireless sensor nodes

Abstract In Inductive Power Transfer (IPT) the misalignment between sending and receiving coils is critical and significantly influences both transfer efficiency and charging time. It can be compensated by the use of multiple coils on the sender side. However, by increasing the number of sending coils, the supply circuit becomes big, complex and not easy to control. In this paper, we propose a compact and efficient supply circuit for multi-coil IPT systems, which activates only the coil under the receiving coil. The receiver detection is based on a compact passive peak voltage detector measuring the sending coil voltage variation. The receiver coil position determination is supported by measurements of the sending coil neighbours voltages, so that a stable power transfer to battery-free wireless sensor nodes can be realized. The investigation of the influence of the type, the shape, and the size of conductive materials between sender and receiver shows that the system can distinguish between the receiver coil and different metallic objects such as iron, coins, and copper.

Airgap Search Coil Based Identification of PM Synchronous Motor Defects

Online detection of rotor and load faults in permanent magnet synchronous motors (PMSM) based on spectrum analysis of current or vibration is not capable of identifying the root cause of the fault, since all faults produce identical fault signatures. The sensitivity of fault detection also depends on the motor and controller design making fault detection unreliable. In addition, operation under variable frequency and load limits the effectiveness of spectrum analysis based methods. In this article, airgap flux monitoring is investigated as an alternative for providing reliable identification of rotor and load faults in PMSMs. Based on the analysis of airgap flux under partial and uniform demagnetization, dynamic eccentricity, and load unbalance, an airgap search coil voltage based method for detection and classification of the faults is proposed. The claims made in the article are verified through experimental testing on an IPMSM under emulated fault conditions along with a comparison to vibration and current spectra-based detection. It is shown that the proposed method provides reliable online identification of the faults for cases where conventional spectrum analysis based methods fail.

Design Optimization of PCB-Based Rotary-Inductive Position Sensors.

This paper introduces a novel methodology to optimize the design of a ratiometric rotary inductive position sensor (IPS) fabricated in printed circuit board (PCB) technology. The optimization aims at reducing the linearity error of the sensor and amplitude mismatch between the voltages on the two receiving (RX) coils. Distinct from other optimization techniques proposed in the literature, the sensor footprint and the target geometry are considered as a non-modifiable input. This is motivated by the fact that, for sensor replacement purposes, the target has to fit a predefined space. For this reason, the original optimization technique proposed in this paper modifies the shape of the RX coils to reproduce theoretical coil voltages as much as possible. The optimized RX shape was obtained by means of a non-linear least-square solver, whereas the electromagnetic simulation of the sensor is performed with an original surface integral method, which are orders of magnitude faster than commercial software based on finite elements. Comparisons between simulations and measurements performed on different prototypes of an absolute rotary sensor show the effectiveness of the optimization tool. The optimized sensors exhibit a linearity error below 0.1% of the full scale (FS) without any signal calibration or post-processing manipulation.

Research on Nondestructive Testing Signal Processing Method for Intermittent Fault of Circuit Structure

In the process of nondestructive testing of circuit structural units, considering that the eddy current intensity and distribution formed under the action of electromagnetic coupling will inevitably cause the change of voltage or impedance of electromagnetic induction testing coil, this kind of phenomenon reflects the signal change information caused by defects such as insulation wear, corrosion, cavitation and so on. In order to fully avoid the sudden faults such as short circuit, open circuit or arc discharge caused by hidden dangers, which force the equipment to stop for maintenance, this paper studies the principle of intermittent fault detection system of circuit structure, designs the circuit structure of typical modules, and establishes the defect prediction model based on Smoothing Technology. It provides a theoretical basis for effectively detecting intermittent fault signals, analyzing the propagation trend of intermittent faults and identifying defect modes, and can be extended to the acquisition and processing of intermittent fault signals of electronic equipment.

X-ray emission from tin (Sn) using the AECS PF-2 plasma focus device

The low energy (2.8 kJ, 25 μF, 15 kV, 120 kA) AECS PF-2 Mather-type plasma focus device operated with nitrogen filling gas is used to study of the high energetic electrons beams effect on the pure tin material inserted on the copper anode tip. The operational gas pressure ranges from 0.2 mbar to 1.2 mbar. For each plasma focus discharge, the current and voltage waveforms are recorded using Rogowski coil and Ohm voltage divider, respectively. Two five channel BPX65 PIN photodiodes X-ray spectrometers (DXS) with appropriate filters are managed to estimate the X-ray yield emitted from the tin (Sn) insert (tin L-series X-ray 3.04–4.474 keV window) at the axial and radial directions. The signals of current, voltage and the temporal evolution of X-rays generated in the AECS PF-2 plasma focus device are simultaneously recorded and then analyzed for different experimental conditions. As the X-ray emission from plasma focus has a shot-to-shot variation, so for each value of gas pressure 3–10 successful shots are performed. The obtained results show that the X-ray yield decreases with increasing pressure from 0.2 to 1.2 mbar. The peak X-ray yield is found to be 0.4 J at the pressure of 0.2 mbar with efficiency ∼0.014% and the lowest values are at the highest pressure of 1.2 mbar. It can be concluded that the X-ray emission from AECS PF-2 plasma focus device depends on the pinch plasma parameters, the generated electron beam properties and the tin insert.

Induced Voltage Estimation From Class EF Switching Harmonics in HF-IPT Systems

One of the advantages of high-frequency inductive power transfer systems is the high tolerance to misalignment and large air-gaps. However, the inherently large magnetic field volumes can lead to coupling of additional foreign objects with the primary, causing possible detuning of the system and heating of the objects. These foreign objects and the conditions of the local environment can load the transmitter, which changes the induced voltage on the primary side. Unfortunately, the induced voltage is not directly measurable in an operating transmitter and the most straightforward way of calculating this variable, through a measurement of primary coil current and voltage, can cause a significant decrease in quality factor which reduces system performance. An integrated solution capable of estimating the induced voltage through other less invasive measurements in the primary is needed to ensure safety of operation through foreign object detection. Knowledge of the induced voltage can also be used to correct tuning mismatches where both sides of the link are active (i.e., in synchronous rectification and bidirectional systems). In this article, multiple candidate variables for estimating the induced voltage are assessed based on factors such as measurement practicality and estimation accuracy. It is demonstrated for the first time that a solution which is based on the measurement of only two variables, the amplitude of the fundamental frequency of the switching waveform and input current, can achieve state-of-the-art induced voltage estimation accuracy. These two variables, which can be obtained using simple cost-effective analogue circuitry, are used in a Gaussian process to generate a regression model. This is used to estimate induced voltages at any angle in an approximate magnitude range of 0–20 V with a normalized root-mean-square error of 1% for the real part and 1.5% for the imaginary part. This corresponds to detecting a plastic container with 1 kg of saline solution (0.4% concentration, to emulate the electromagnetic profile of muscle) at a distance of 15 cm (1.5 coil radii). The results presented in this article were obtained with a bidirectional Class EF transceiver operating at 13.56 MHz delivering up to 32 W with coupling factors ranging from 1.1% to 4%. This article is accompanied by a video file demonstrating the experiments.

Modular multilevel TMS device with wide output range and ultrabrief pulse capability for sound reduction

Objective. This article presents a novel transcranial magnetic stimulation (TMS) pulse generator with a wide range of pulse shape, amplitude, and width. Approach. Based on a modular multilevel TMS (MM-TMS) topology we had proposed previously, we realized the first such device operating at full TMS energy levels. It consists of ten cascaded H-bridge modules, each implemented with insulated-gate bipolar transistors, enabling both novel high-amplitude ultrabrief pulses as well as pulses with conventional amplitude and duration. The MM-TMS device can output pulses including up to 21 voltage levels with a step size of up to 1100 V, allowing relatively flexible generation of various pulse waveforms and sequences. The circuit further allows charging the energy storage capacitor on each of the ten cascaded modules with a conventional TMS power supply. Main results. The MM-TMS device can output peak coil voltages and currents of 11 kV and 10 kA, respectively, enabling suprathreshold ultrabrief pulses (>8.25 μs active electric field phase). Further, the MM-TMS device can generate a wide range of near-rectangular monophasic and biphasic pulses, as well as more complex staircase-approximated sinusoidal, polyphasic, and amplitude-modulated pulses. At matched estimated stimulation strength, briefer pulses emit less sound, which could enable quieter TMS. Finally, the MM-TMS device can instantaneously increase or decrease the amplitude from one pulse to the next in discrete steps by adding or removing modules in series, which enables rapid pulse sequences and paired-pulse protocols with variable pulse shapes and amplitudes. Significance. The MM-TMS device allows unprecedented control of the pulse characteristics which could enable novel protocols and quieter pulses.

Structure and Operating Performance of a Double Electrical Excitation Synchronous Generator With Embedded Brushless Synchronous Exciter Utilizing DC-Field Excitation

A double electrical excitation synchronous generator (DEESG) with an embedded brushless exciter is proposed to achieve brushless excitation for a brush excitation electrical excitation synchronous generator (EESG). A set of extra stator excitation windings is placed in the stator slots with armature coils to generate a static magnetic field. There are two sets of windings on the rotor: pulsating excitation winding (W <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">p</sub> ) and main excitation winding (W <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">F</sub> ). The winding direction of the coils of W <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">p</sub> and W <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">F</sub> on the same rotor-pole-body is the same. The AC voltage of W <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">p</sub> which is induced by static magnetic field provides dc excitation current for W <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">F</sub> by diodes. Both currents in the coils of the W <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">p</sub> and W <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">F</sub> generate the rotor excitation flux which induces voltage in the armature coils. In this study, the operating principle is analyzed theoretically. The no-load and load characteristics are studied using Maxwell. The influence of the novel winding structure on the output voltage when the load varies is also analyzed. The voltage regulation rate of DEESG is reduced because the rotor excitation currents can be increased with armature current. A 1.5 kVA prototype is fabricated for experiment. The measured results agree well with the theoretical and FE-predicted results.

Modellation and simulation of shunt active power filters type for variable nonlinear load

The paper is dealing with modelling and simulation of running principle of shunt type active power filter. It is possible to highlight the running of the active filter as a result of correlation of power supply voltage, the power outage on filter coil and converter input voltage. The mathematical equations for filter running were implemented into the PSIM software, both with instantaneous variables without DC voltage control and Vdc voltage control in the (dq) coordinate system. The numerical simulations performed without DC voltage control have shown a Vdc voltage overgrown. Vdc voltage control is taking off this inconvenience and allows harmonics balance putting in a filter current in phase opposition with the harmonic current of nonlinear load. By numerical simulation of varable voltage power supply of the nonlinear customer it was highlighted existence of an optimal area of THDi thanks to correlation between grid voltage, coil and converter input voltage. Choosing and dimensioning of three phase coil of power circuit of SAPF has a decisive influence on the voltage range of adjustment of nonlinear customer and implicit on THDi grid current.

Mathematical modeling of impulse island controller to safely store the energy from high‐voltage lightning impulse

AbstractExtricating the energy from lightning impulse is very difficult for researchers due to the uncontrollability of hazardous and intermittent parameters. This paper proposed a mathematical method to island the lightning impulse to provide safety for the impulse storage system. The proposed model also can intelligently force the impulse to be extricated for the conversion system of the lightning energy storage device. This islanding controller is designed to increase the efficiency and safety of the storage system. Six essential parameters, that is, breakdown voltage, current dependency, spark channel radius, spark channel conductivity, coil inductance, and coil voltage, are considered to design the mathematical model. These parameters are formulated to record the responses of the proposed controller. All the equations are validated by using state of the art experiments and prototype hardware setup. The proposed method, mathematical model, and analyzed responses may assist lightning researchers in advancing lightning energy harvesting.

Development of Triaxis Electromagnetic Tactile Sensor With Adjustable Sensitivity and Measurement Range for Robot Manipulation

Tactile sensor is one of the most important sensations for human to perceive the external world. This article proposed a novel triaxis soft electromagnetic (EM) tactile sensor based on the principle of a transformer, where the sensitivity or measurement range of the designed tactile sensor can be adjusted by changing the excitation voltage (frequency or amplitude) of the primary coil. It mainly contains a primary coil, four secondary coils, and a PDMS elastomer containing a magnet, where the coils are planar coils and the four secondary coils are a four-quadrant structure. Therefore, the displacement of the magnet in the 3-D space can be obtained by decoupling the output voltages of the four secondary coils, which is equivalent to being capable of detecting the triaxis force. Theoretical analysis and model simulation were first used to study the influence of the excitation voltage of the primary coil on the output voltage of the secondary coil, which provides a theoretical basis for the adjustable sensitivity of the sensor. Then, the designed tactile sensor was prepared, and the typical performances of the adjustable sensitivity were evaluated by a commercial six-axis force/torque sensor. The results have shown the relationship between the sensitivity of the sensor and the excitation voltage of the primary coil and verified its ability to measure the triaxis force. Finally, the adjustable ability of the designed tactile sensor to measure normal force and shear force was verified by a commercial robotic arm with an electric gripper.

Prediktivna kontrola adaptivnog modela za sistem magnetnog vešanja pod disperzijama početne pozicije i poremećajima napona

A nonlinear magnetic suspension system consisting of a mechanical motion and electromagnetic circuit is considered in this paper. An online algorithm that is used to stabilize the suspended mass targeting the desired ball position, ball velocity and coil current is presented. A steady-state condition, in which the ball position, the ball velocity, and the coil current were assumed constant, was used as a reference trajectory for the closed-loop simulations. An adaptive model predictive control method was employed to control the coil voltage while the discrete plant model and operating conditions were changed at each time step. The effectiveness of the proposed control law was validated in the presence of disturbances in initial ball position, steady-state ball position, suspended mass, and voltage using the Monte-Carlo simulation method. The sinusoidal, step, and impulse voltage disturbances were applied consequently to the system while imposing random dispersions of the initial ball position. Numerical results with five hundred trials illustrated that the designed algorithm can stabilize the system and track the desired reference without exceeding the state and input constraints despite the wide range of dispersions in initial ball position, steady-state ball position, suspended mass, and input voltage disturbances.

Upgrade of the APEC code: Implementation of halo currents and multi-turn coils analyses

The APEC code, implemented for the simulation of the plasma equilibrium and its evolution in presence of 3D passive structures [1][2], has been upgraded to simulate the effect of the eddy currents in the coils and the halo current in the plasma. The effect of the eddy currents in the coils is implemented considering each coil voltage driven and characterized by its number of turns with its corresponding resistivity. An additional degree of freedom in the finite element regions of the coils is in this case needed corresponding to the electrical current in each turn. The effect of the halo current is instead taken into account by applying both toroidal and poloidal plasma current also outside the last closed surface. The halo width is proportional to a fraction of the plasma core flux. The part of the plasma poloidal halo current intersecting the first wall is injected to the passive structures. Simulation with the upgraded version of APEC have been run for the ITER machine to show the soundness of the new APEC features.

An analytical solution for vertical coils near a multi-layered metallic pipe in Pulsed Eddy Current Testing

Analytical model for Pulsed Eddy Current Testing (PECT) of a multi-layered metallic pipe has not been solved, which limits the development of PECT technology. In this paper, the analytical model for vertical coils near a multi-layered metallic pipe is proposed. However, the analytical solution is hard to solve due to the large number of undetermined coefficients. Combined with the global matrix method, an improved transfer matrix across a conductor is established, which overcomes unsolvable problem in the traditional transfer matrix method. The induced voltage of pickup coil calculated based on the analytical model is verified by Finite Element Method (FEM) and experiments. Furthermore, the influence of several working conditions of pipelines on the PECT signal is studied based on the analytical model, providing guidance for engineering applications.

Experimental Analysis of Flux-Coupling-Type Superconducting Fault Current Limiter Prototypes

The development of power system has increased the level of short-circuit fault current, and flux-coupling-type superconducting fault current limiter can effectively limit short-circuit current by the increased impedance after decoupling of windings. In this paper, two prototypes of pancake-winding and layer-winding were manufactured and experiments were conducted. The results show that the current-limiting ratio of two prototypes reached more than 40%. Analysis of the control strategy indicates that two breakers of the limiter could operate at the same time or at different times, and when two breakers operated asynchronously, there would be a damping direct current in the windings. When decoupled, two prototypes had coil voltage distributions of increase and then fall off, and pancake-winding had a intercoil voltage distribution of sawtooth.

Detection of fiber waviness in carbon fiber prepreg using Eddy current method

In order to control the quality of carbon fiber reinforced polymer in the production process, a method of detecting fiber waviness in carbon fiber prepreg using eddy current (EC) probe is proposed. The EC probe includes orthogonal rectangular coils. The excitation coil is parallel to the designed fiber direction, so that the output voltage of the reception coil is only related to the bending of EC caused by fiber waviness. The phase of the output voltage is used for characterizing fiber direction. The results show that the probe is able to distinguish fiber direction as small as 0.5° and fiber waviness in prepreg can be detected. Moreover, algorithm of reconstructing fiber distribution is proposed and fiber waviness is visualized.

Exploring mechanical assonance for impact energy harvesting using acoustic metamaterials

Acoustic metamaterials are engineered to possess unique dynamic properties that are not commonly found in nature. It has been demonstrated that customizing the characteristics of their local features can help optimize their dynamic performance under specific loading conditions. Drawing inspiration from the literary device called “assonance,” the term “mechanical assonance” may be ascribed to the dynamic phenomenon realized by sequencing oscillators with tuned responses within a waveguide to engineer a prescribed wave transformation across it. In this context, assonance provides a framework to utilize resonant local features within a host structure or material and interactive mechanisms thereof as building blocks to create enriched functionalities for acoustic metamaterials. Using a discrete element representation for an acoustic metamaterial barrier (AMB), a numerical study is conducted to ascertain parametric dependence for assonant mechanisms related to resonator frequencies, their sequencing, and host material stiffness. Normalized metrics are extracted to estimate transmitted pulse mitigation under impact-type loading. It is found that resonator sets with octave spacing having the number of resonators of a specific frequency proportional to that frequency’s amplitude in the input spectrum is desirable for lower transmissibility. Further, sequencing the lowest frequency resonator set closest to the incident-side gives better performance. Engineering a high degree of impedance mismatch between host material sections is also preferable. The energy sequestered by the local resonators can be harvested utilizing the resonator’s mass as the multifunctional kernel for a linear electromagnetic generator. A multiphysical model is developed to predict the harvested electric voltage and power from the AMB and validated using proof-of-concept experiments. Finally, various coil placement and voltage rectification schemes are also studied using simulations to ascertain preferable design configurations.

Load Characterization in High-Frequency IPT Systems Using Class EF Switching Waveforms

Large magnetic field volumes associated with core-less high-frequency inductive power transfer (HF-IPT) systems allow multiple receivers to be powered from one transmitter, but also provide greater probability for foreign objects to couple to the system. Knowledge of the types of objects (legitimate receivers or otherwise) that are coupled to the transmitter is critical. Such knowledge on the transmit side would allow the system to be deactivated in the presence of foreign objects, and to determine the exact state of tuning of the receivers so that it may adjust itself accordingly to optimize system performance. This article introduces a technique to calculate the induced voltage generated by coupled receivers and foreign objects on the transmit coil in real time. Changes in the position or electrical quantities of the receivers, and foreign objects, alter the induced voltage on the transmit coil, and with it the trajectory of the switching waveforms of the inverter driving the transmit coil. From the shape of these waveforms, information on the phase and amplitude of the induced voltage can be extracted, thus enabling the induced voltage on the primary to be estimated with a single, easy to access, voltage measurement, which is easier than estimating the induced voltage from measurements of coil current and total coil voltage. We used a support-vector-machine (SVM) to perform regression analysis on the drain voltage data. The experimental setup uses a 100 W, 13.56 MHz Class EF inverter, and the model was generated from a large number of samples of the drain voltage waveforms operating at different known loads. These were generated from our in-house HF-IPT test load, which uses a Class EF synchronous rectifier. The results allow the induced voltage on the transmit coil to be estimated in real time from the drain voltage waveform alone, with a normalized root mean square error of 1.1% for the real part (reflected resistance) and 1.2% for the imaginary part (reflected reactance). This article is accompanied by a video file demonstrating the experiments.

Dielectric barrier discharge analysis from the point of view of supply voltage and reactor topology

This paper aims to provide a comprehensive analysis of the output of DBD reactors considering 2 different power supplies that provide rectangular command voltage with variable duty cycle and frequency. The experiments presented were performed with these power supplies considering four geometries of DBD reactor. At this stage the input parameters of the power supplies are: frequency of control pulses, duty cycle and high voltage level applied on the DBD reactors by choosing a certain number of turns for the primary windings of the high voltage coil. The parameters considered as outputs from the reactor-power supply assembly were: the high voltage output and the electric current from the primary induction coil.