Search

The characteristic of wirelessly transmitting electrical energy without the need for electrical connections enables power transfer in a wireless energy transmission system. Monitoring devices in the power grid can directly draw power from the high-voltage side of the grid. The parameters of the coil′s inductance are closely related to the transmission efficiency, constant voltage gain, constant current gain, and transmission power of the wireless energy transmission system. Therefore, precise modeling of the coil′s inductance parameters is crucial. Firstly, the planar spiral coil is equivalently represented as concentric circles with the same number of turns and equal spacing. Then, starting from the definition of magnetic vector potential, analytical expressions for the mutual inductance and self-inductance of the planar spiral coil are derived and established. Verification of the self-inductance and mutual inductance of densely wound and loosely wound planar spiral coils is carried out using Agilent 4294A and Comsol Multphysics. The study indicates that the maximum errors in the self-inductance and mutual inductance models of the planar spiral coil are 4. 12% and 4. 90%,respectively. Therefore, the analytical calculation model for the inductance parameters of the planar spiral coil proposed in this paper exhibits high computational accuracy, simultaneously addressing both densely wound and loosely wound coils, with no applicable condition restrictions. [ABSTRACT FROM AUTHOR]

Wireless power transfer (WPT) system in seawater exhibits distinct transmission characteristics from those in air due to the unique properties of seawater medium and the complexity of the seawater environment. In this paper, transmission characteristics of a 2-transmitter (2TX) and 1-receiver (1RX) WPT system in the frequency band of 350 ~ 550 kHz in seawater are investigated. When the transfer distance is at midrange, the maximum load voltage point of the system is shifted from 460 to 430 kHz compared to that in air, and the maximum transfer efficiency is 7 times of that in air, which is very different from the traditional view that the transfer efficiency in water is always worse than in air. The system maintains a stable output voltage when the receiving coil is at different offsets. To grasp the influence mechanism of seawater on wireless power transfer, two new parameters, complex self-inductance and complex mutual inductance, are introduced into the circuit model to explain the shift of the optimal frequency and the increase of transfer efficiency, and the model is verified through experiments. [ABSTRACT FROM AUTHOR]

Research is focused on improving the dynamic accuracy of control surface positioning during the switching of hydraulic actuator modes and studying the processes and phenomena that cause control surface overshoot. Existing studies on the dynamic accuracy of hydraulic actuators have been analyzed. Transitional processes occurring in the “electromagnetic recirculation valve – electronic control unit” loop during changes in hydraulic actuator operating modes have been examined. The features of processes and physical phenomena leading to increased activation time of the hydraulic actuator have been identified. Solutions and electrical connection schemes for connecting the hydraulic actuator recirculation valve to the electronic control unit have been proposed to meet the accuracy positioning and activation time requirements. Experimental studies have been conducted to simulate the operational mode of hydraulic actuators, and failure situations modes under various load forces have been identified. Based on the results, principles for designing connection schemes for the electromagnetic recirculation valve of the hydraulic-mechanical actuator to the electronic control unit, which enhance system positioning accuracy at the structural level, have been formulated. Technical solutions aimed at achieving the specified accuracy and activation time for the hydraulic actuator have been developed and practically tested. The effectiveness and suitability of the proposed solutions for operational use, considering external factors, have been experimentally confirmed. [ABSTRACT FROM AUTHOR]

For designing high-field electromagnets, the Lorentz force on coils needs to be computed in order to design suitable support structures, and the inductance should be computed to evaluate the stored energy and dynamics. Also, the magnetic field and its variation inside the conductor is of interest for computing stress and strain, and due to superconducting quench limits. For these force, inductance, energy, and internal field calculations, the coils cannot be naively approximated as infinitesimally thin filaments due to divergences when the source and evaluation points coincide, so more computationally demanding calculations are usually required, resolving the finite cross-section of the conductors. Here, we present a new alternative method that enables the internal magnetic field vector, self-force, and self-inductance to be computed rapidly and accurately within a 1D filament model. The method is applicable to coils for which the curve center-line can have general noncircular shape, as long as the conductor width is small compared to the radius of curvature. This paper extends a previous calculation for circular-cross-section conductors (Hurwitz et al 2024 IEEE Trans. Magn. ) to consider the case of rectangular cross-section. The reduced model is derived by rigorous analysis of the singularity, regularizing the filament integrals such that they match the true high-dimensional integrals at high coil aspect ratio. The new filament model exactly recovers analytic results for a circular coil, and is shown to accurately reproduce full finite-cross-section calculations for a non-planar coil of a stellarator magnetic fusion device. Due to the efficiency of the model here, it is well suited for use inside design optimization.

In 1873, J.C. Maxwell derived relations for current density and current in a solitary long cylindrical conductor supplied with variable current. According to Maxwell, the current density in a conductor increases towards the conductor surface. This phenomenon is called the skin effect. The skin effect affects in particular the inductance of a line formed by one or several long parallel conductors. A number of papers have been published regarding the skin effect and its effect on inductance. Another phenomenon, closely related to the skin effect, is the proximity effect, which refers to the dependence of the current density in a conductor on the proximity of other conductors through which a time-variable current is flowing. Many published papers deal with the calculation of current density in two conductors, using the method for calculating current density in a solitary conductor. All the phenomena given above can be analysed and quantitatively described based on the knowledge of current density in conductors, and therefore the method for calculating current density in a group of conductors is of fundamental significance. It follows from the analysis performed that the skin effect is not a general characteristic of current density in long conductors, except for in the solitary conductor. This conclusion affects the knowledge of the phenomena associated with the skin effect. [ABSTRACT FROM AUTHOR]

Bridge cables are commonly used in bridge construction, and assessing their condition is crucial for ensuring bridge safety. However, current inspection methods often rely on large and heavy detection mechanical structures, which can be inconvenient during the inspection process. In light of these limitations, this paper proposes a portable non-destructive inspection method for bridge cables that detects the total magnetic flux variations utilizing an inductive search coil sensor. The occurrence of corrosion and cracks in bridge cables leads to changes in their original sectional area and permeability. These changes result in variations in the induced current that is excited by the coil, leading to distortions in both the magnetic field energy and the coil's self-inductance. Thus, cable damage can be detected inversely by monitoring coil self-inductance variation. To assess the feasibility of this method, a numerical analysis is conducted, and an experimental structure is designed using a mock-up cable specimen with parallel steel wires that have varying degrees of damage. The experimental results demonstrate the effectiveness of the proposed method, which utilizes an inductive search coil sensor, intuitively identifies and quantifies internal flaws on the cable in real-time while maintaining a lightweight structure. The width and amplitude of the coil inductive response show a positive correlation with the flaw's axial length and cross-sectional area, indicating that these parameters can be utilized to quantify the size of the flaw. [ABSTRACT FROM AUTHOR]

Self- and mutual inductances are major design parameters for wireless power transfer (WPT) systems. To optimize a WPT system and estimate its performance in terms of received power and efficiency, it is essential to obtain a simple, fast, and accurate calculation of these two parameters. The polarized double-D (DD) coils were selected due to their simplicity of structure, high efficiency, and low sensitivity to misalignment conditions. This paper presents analytical calculations of self- and mutual inductance using the Biot-Savart law for DD coils. The results of the analytical calculations of mutual inductance in different distances between coils were investigated, and the results of the calculations were verified using experimental and finite element method (FEM) simulation results. This paper also presents analytical and FEM-based optimization guidelines for the coupling coefficient of the transmitter coil.

In 1873, J.C. Maxwell derived relations for current density and current in a solitary long cylindrical conductor supplied with variable current. According to Maxwell, the current density in a conductor increases towards the conductor surface. This phenomenon is called the skin effect. The skin effect affects in particular the inductance of a line formed by one or several long parallel conductors. A number of papers have been published regarding the skin effect and its effect on inductance. Another phenomenon, closely related to the skin effect, is the proximity effect, which refers to the dependence of the current density in a conductor on the proximity of other conductors through which a time-variable current is flowing. Many published papers deal with the calculation of current density in two conductors, using the method for calculating current density in a solitary conductor. All the phenomena given above can be analysed and quantitatively described based on the knowledge of current density in conductors, and therefore the method for calculating current density in a group of conductors is of fundamental significance. It follows from the analysis performed that the skin effect is not a general characteristic of current density in long conductors, except for in the solitary conductor. This conclusion affects the knowledge of the phenomena associated with the skin effect.

Winding inductance is a crucial parameter of machines, which plays an essential role in flux-weakening capability, reluctance torque, power factor, etc. In this article, winding inductance characteristics of flux-switching permanent magnet (FSPM) machines are investigated from the perspective of air-gap modulation magnetic field. With the aid of the general air-gap field modulation theory, the air-gap magnetic field contributed by an arbitrary energized winding of FSPM machines is modeled and analyzed. Then, an analytical expression of winding inductance is derived based on winding function and single-phase magnetic field, through which the relationship between winding inductance and single-phase magnetic field harmonics is unveiled. It is found that the direct current (dc) and 2nd harmonic components of winding inductances in FSPM machines are caused by the dc and 2nd time-harmonic components of primitive harmonics, respectively, which are essentially different from that of traditional interior permanent magnet or reluctance machines. Finally, experiments on a prototype three-phase 12/10 FSPM machine are conducted to verify the theoretical analysis. [ABSTRACT FROM AUTHOR]

In the design and production of electrical and electronic devices and circuits, it is desirable to have a calculation formula for obtaining exact inductance values, which are generally fundamental for coils. In this paper, a formula that can be applied to the exact calculations of the self‐inductance of arbitrary‐shaped single‐layer coils is presented, and its application to the several types of coils that are technologically valuable is reported. Specifically, the formula employs a new coefficient corresponding to the Nagaoka coefficient and the shape function determined by the coil. Moreover, it realizes a versatile and convenient inductance calculation method. In addition, as the formula is derived via an analytical method, it has the advantage that it can be calculated with a short‐time numerical integration. As examples of the application of the formula, rhombic, race‐track, elliptic, and regular polygonal coils were discussed, and the process and result of deriving the shape function and new coefficient for each coil were presented. Furthermore, regarding the calculation formula for regular polygonal coils, we made a regular pentagonal coil and conducted an experiment, and the validity of the calculation formula was confirmed. © 2022 Institute of Electrical Engineers of Japan. Published by Wiley Periodicals LLC. [ABSTRACT FROM AUTHOR]

Bridge cables are commonly used in bridge construction, and assessing their condition is crucial for ensuring bridge safety. However, current inspection methods often rely on large and heavy detection mechanical structures, which can be inconvenient during the inspection process. In light of these limitations, this paper proposes a portable non-destructive inspection method for bridge cables that detects the total magnetic flux variations utilizing an inductive search coil sensor. The occurrence of corrosion and cracks in bridge cables leads to changes in their original sectional area and permeability. These changes result in variations in the induced current that is excited by the coil, leading to distortions in both the magnetic field energy and the coil’s self-inductance. Thus, cable damage can be detected inversely by monitoring coil self-inductance variation. To assess the feasibility of this method, a numerical analysis is conducted, and an experimental structure is designed using a mock-up cable specimen with parallel steel wires that have varying degrees of damage. The experimental results demonstrate the effectiveness of the proposed method, which utilizes an inductive search coil sensor, intuitively identifies and quantifies internal flaws on the cable in real-time while maintaining a lightweight structure. The width and amplitude of the coil inductive response show a positive correlation with the flaw’s axial length and cross-sectional area, indicating that these parameters can be utilized to quantify the size of the flaw.

With the emergence of electric vehicles and electric aircraft technologies, lightweight motors have become a requirement. Conventional motors are generally made up of coils, permanent magnets, heavy iron stators, and rotor cores. This article presents complete analytical modeling and design of a novel coreless multi-phase magnetic resonant motor (MMRM), conceptualized through the approach of magnetic resonance coupling. The removal of magnetic iron cores drastically reduces the weight of the resulting motor. The stator and rotor cores of the motor are made of reinforced plastic fibers and can be 3-D printed. Unrelated to the general operating principle of the existing conventional electric motors, resonant wireless power transfer (WPT) is the key feature of these motors. All the essential machine characteristics, such as self-inductance, mutual inductance, torque, and frequency domains, are fully developed. The mathematical modeling of the machine’s physical phenomena is linked to its operation by simulation. This article shows the design concept and discusses the simulation procedure used to verify the developed analytical model through a finite-element analysis (FEA) from the established modeling topology equivalent to the proposed configuration motor model. Although the design is straightforward, an accurate analytical modeling and analysis are significant challenges to consider. [ABSTRACT FROM AUTHOR]

In this paper, analytical and semi-analytical formulas are presented for the self- and mutual inductance of thin ordinary disk coils and thin Bitter disk coils. The coils lie concentrically in a plane. The ordinary coils are coils with constant current density. The current density of a current carrying Bitter disc is not uniform across its cross-sectional area, but it is a function of the ratio of the inner diameter of the disk to an arbitrary radius within the disk. In this paper, we show the possibility to calculate the mutual and self-inductance of thin disk coils from the real coils of the cross-sections using some valuable conditions. The formulas for the mutual inductance and the self-inductance were obtained in the semi-analytic form as the combination of the elliptic integral of the second kind and a simple integral for the ordinary disk coils. The mutual inductance and self-inductance were obtained in the analytical form as the elliptic integral of the second kind for the Bitter disk coils. The formula for the self-inductance of the ordinary full disk was obtained in the close form. All formulas are given in remarkably simple form and give perfectly accurate results with a significantly small computational time. All cases of either regular or singular (disks in contact or overlapping) are covered. Many presented examples show the excellent numerical agreement with previously published methods.

Small loop transient electromagnetic method (TEM) is a widely used electromagnetic exploration method in mountainous areas, tunnels, underground coal mines and other areas with difficult construction arrangement. The self-inductance and mutual inductance of the coil are prominent because this method increases the number of turns of the loop and then increases the emitted magnetic dipole moment to increase the detection depth and improve the anti-interference ability. However, the self-inductance and mutual inductance between multi-turn loops often cause severe distortion of early signals measured by TEM, resulting in generally low apparent resistivity. The calculation formulas of self-inductance and mutual inductance for rectangular coils and circular coils are analyzed and summarized, and the corresponding self-inductance and mutual inductance values and their relative errors are calculated respectively when the coil side length or radius is 1 m to 5 m, and the applicability of various calculation formulas is analyzed, and an appropriate calculation formula of inductance for small loop is given.

In this paper, we give new formulas for calculating the self-inductance for circular coils of the rectangular cross-sections with the radial and the azimuthal current densities. These formulas are given by the single integration of the elementary functions which are integrable on the interval of the integration. From these new expressions, we can obtain the special cases for the self-inductance of the thin-disk pancake and the thin-wall solenoids that confirm the validity of this approach. For the asymptotic cases, the new formula for the self-inductance of the thin-wall solenoid is obtained for the first time in the literature. In this paper, we do not use special functions such as the elliptical integrals of the first, second and third kind, nor Struve and Bessel functions because that is very tedious work. The results of this work are compared with already different known methods and all results are in excellent agreement. We consider this approach novel because of its simplicity in the self-inductance calculation of the previously-mentioned configurations.

Self- and mutual inductances are major design parameters for wireless power transfer (WPT) systems. To optimize a WPT system and estimate its performance in terms of received power and efficiency, it is essential to obtain a simple, fast, and accurate calculation of these two parameters. The polarized double-D (DD) coils were selected due to their simplicity of structure, high efficiency, and low sensitivity to misalignment conditions. This paper presents analytical calculations of self- and mutual inductance using the Biot-Savart law for DD coils. The results of the analytical calculations of mutual inductance in different distances between coils were investigated, and the results of the calculations were verified using experimental and finite element method (FEM) simulation results. This paper also presents analytical and FEM-based optimization guidelines for the coupling coefficient of the transmitter coil. [ABSTRACT FROM AUTHOR]

Copyright of Electric Drive is the property of Electric Drive Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The electrical-magnetic characteristics of a Switched Reluctance Motor (SRM) exhibit highly nonlinear relationship with respect to the rotor position and excitation current, which poses challenges for both precise static measurements and exact calculation of these properties in real-time control. To guarantee that an in-lab test result can be used in the application, firstly a measurement method is proposed to characterize the SRM's electromagnetic properties such as the flux linkage, magnetic co-energy, phase inductance and electromagnetic torque on the basis of an installed SRM control circuitry and half-bridge power converter. By this means the characterization process is equivalent to the online observation in its results. Secondly, a theoretical model is built to discriminate the physical meaning between the incremental inductance and the phase inductance, which is the origin of other relevant parameters. This helps to guide the correct utilization of the characterization result. Thirdly an in-situ cross-validation experimentation according to the magnetizing and demagnetizing status measurement verifies the feasibilities and accuracy of the proposed inductance measuring method, which avoid a dubious FEM-based comparison between the numerical calculation and experimental results. Cross-validation experiment shows that the proposed in-situ characterization scheme obtains an accurate full-range electromagnetic properties. The proposed methodology breaks the barrier between the in-lab measurement and on-line utilization of the SRM parameters, highlighting the merits that it completely includes the in-situ factors and replicates the operational scenario without the need of specifically designed instrumentation, which is especially suitable for rapid field characterization for high power motors.

This article is devoted to development of a method for calculating the parameters of an asynchronous motor of an electric locomotive with asymmetrical windings of stator and rotor. A method for determining self and mutual inductances of the stator and rotor phases of an asynchronous motor with asymmetric windings and their relations to mechanical variables is proposed. It is based on comparing two equations of stored magnetic energy, one equation calculated through induction, magnetic field strength and geometrical dimensions and another equation calculated through the parameters of the motor circuits. It is shown that the obtained solutions correspond to the previously existing methods, but they give the additional possibilities in mathematical modeling. The proposed technical solution allows higher accuracy developing of a mathematical model of a drive with an asynchronous motor having asymmetrical stator and rotor windings for studying dynamic processes during the operation of the specified drive, in particular, the drive of auxiliary machines for electric locomotive, where an asynchronous motor with asymmetrical stator windings is used as a phase release.

This paper presents inductance characteristics analysis of the consequent-pole permanent magnet in-wheel motor (CPM). Considering the specialty of consequent-pole structure, this paper analyzes the change rule of the winding self-inductance via equivalent magnetic circuit method (EMCM). The corresponding equivalent resistance is directly given when the rotor is in different positions. Based on this, equivalent magnetic circuit (EMC) that reflects the inductance of the CPM is summarized in this paper. In order to analyze the difference and connection of the inductance among the CPM, two models with 36 slots 32 poles and 48 slots 40 poles are established and compared. Moreover, the Fourier analysis expression of winding self-inductance is deduced to prove the different periodicities of winding self-inductance between two motors. The experimental result is consistent with the theoretical analysis, and the conclusion effectively proves the close relationship between the inductance characteristics and its internal structure of the motor.

This work presents a class of micro-electro-mechanical system (MEMS)-driven radio frequency filters in the X-band. The X-band center frequencies are achieved by resorting to the third-order antisymmetric Lamb wave mode (A3) in a 650-nm-thick Z-cut lithium niobate thin film. A novel bandwidth (BW) widening technique based on using the self-inductance of the top interdigital transducers and bus lines is proposed to overcome the limitations set by the electromechanical coupling (${k} _{t}^{2}$) and satisfy the demands in miniaturization and wide BW. Four different designs of the filters are designed and fabricated to show the trade-off among BW, insertions loss (IL), out-of-band rejections, and footprint. Due to the spurious-free and high- ${Q}$ performance of the A3 lithium niobate resonators, the fabricated A3 lithium niobate filters have demonstrated small in-band ripples and sharp roll-offs. One of these fabricated has demonstrated a 3-dB BW of 190 MHz, an IL of 1.5 dB, and a compact footprint of 0.56 mm2. Another design is fabricated to demonstrate a 3-dB BW of 170 MHz, an IL of 2.5 dB, an out-of-band rejection of 28 dB, and a compact footprint of 1 mm2. [ABSTRACT FROM AUTHOR]

Load‐independent constant current (CC) output with high‐system efficiency is required in many cases of Wireless power transfer (WPT) applications. However, the existing topologies with CC output are hard to achieve both simple structure and enough design freedom. In this study, the series/parallel–series (S/PS) topology, which has three compensation capacitors, is presented to achieve CC output. The constant output current of the proposed S/PS topology is free from the constraint of the coils' self‐inductance of the loosely coupled transformer (LCT). A thorough analysis of the proposed S/PS topology that implements CC and ZPA is provided. Besides, ZVS can also be obtained by reasonably setting the value of compensation capacitors. An experimental prototype with 50 V input voltage and 3 A output current is fabricated to validate the practicability and rationality of the proposed topology, and 92.18% power transfer efficiency is achieved. Furthermore, a design example with 2 A output current and the corresponding experimental results are provided to verify that the CC output of the proposed S/PS topology is free from the constraint of the LCT parameters. Finally, a comprehensive comparison with several existing topologies for CC output is conducted to reveal the advantages of the proposed S/PS topology. [ABSTRACT FROM AUTHOR]

Today, many applications requiring mass manufacturing are shifting to robotic applications through automation systems. The actuators used in these robotic systems should be designed according to needs. In this study, an air core spherical motor which has rotor and stator winding arrangement is described. The spherical motor's windings are optimally positioned on the stator made of delrin. Mutual inductance and self-inductance change were examined according to r=4, 20, 40 and 60 mm radius and the change in the number of stator winding for the spherical motor. Changes in inductance were found through curve fitting method with the coefficients of cubic equations. Equivalent circuit with winding inductance model is also given. Torque change according to magnet change was also investigated. Magnetic flux density change of N52 M magnet 3 winding 2-pole model was examined and the effect of the increase in overall size on torque was evaluated. [ABSTRACT FROM AUTHOR]

The numerical technique for parameters estimation is applicable for the induction machine (IM) with arbitrary number of stator phases and arbitrary number of rotor bars. The self‐inductance and mutual inductance matrices for the stator side and rotor side are constructed through the magnetic vector potential method. The Clarke transformation is implemented to separate the magnetising inductance and slot leakage inductance of each sequence plane, where the orthogonality theory of trigonometric function is used. The harmonic leakage inductance of each plane is calculated based on the ratios of the harmonic components among air‐gap flux density. The 2D eddy current field solver is conducted to obtain the rotor resistance based on the IM equivalent circuit. A classical mathematical model is established using the acquired parameters under Simulink environment to accomplish the comparisons between the simulated and experimental performance. The non‐sinusoidal power supply based on the rotor field‐orientated control, which is highly dependent on the precision of parameters, is carried out under no‐load and heavy load conditions to indirectly verify the accuracy of parameters. [ABSTRACT FROM AUTHOR]

Multiphase interleaving buck DC/DC converters (BCs) with magnetically coupled inductors (CIs) have been researched to improve the performance of voltage regulator module (VRM) and point‐of‐load (POL). Commercial three or more phase CIs are asymmetric CIs (ACIs) offering unequal phase self‐inductance and unequal coupling between phases. By analysing the steady‐state current ripple and transient current response speed of three‐phase interleaving BCs with three‐phase ACIs, the design criterion and design guidelines for three‐phase ACIs are presented to simultaneously improve the steady‐state performance and transient performance of three‐phase interleaving BC with three‐phase ACIs. A three‐phase interleaving BC prototype with three‐phase ACIs is constructed. The experimental results show that three‐phase interleaving BC's steady‐state phase current ripple can reduce 45%, and its transient output current response speed can increase 63.9% simultaneously by using three‐phase ACIs instead of three‐phase discrete inductors, and with a smaller total core volume and higher efficiency. The results of this study can be used to design VRM in data centres and POL with smaller steady‐state phase current ripple, faster transient output current response speed, and higher efficiency. [ABSTRACT FROM AUTHOR]

This article proposes an analytical model that provides accurate self-inductance and mutual inductance calculations for two mutually coupled rectangular, planar, and spiral coils with an air core, which are equal and parallel, including the possibility of a lateral misalignment. Both single- and double-layered coil geometries were modeled by considering an arbitrary number of turns with a circular cross section per layer. The model equations, which can be readily implemented in software, are the results of a systematic approach that starts from the equations for the self-inductance of a wire and the mutual inductance of two parallel and misaligned wires that lie on the same plane. Accuracy is guaranteed by considering all the magnetic interactions among the individual turns in the two coils, while the simplifications involve only the calculations made at the corners of the coils. The model was validated by taking as reference experimental measurements carried out on a rectangular and a square magnetic coupler. A second analytical model, based on equivalent single-turn coils, was also tested for comparison purposes. The validation was extended with finite-element analysis tools by considering a wide range of coil side lengths, air gaps, number of turns, and lateral misalignments. The proposed model can, therefore, be regarded as a reliable tool to aid in the design of rectangular-shaped air-core magnetic couplers with applications in the contactless transfer power that are not necessarily limited to vehicle electrification. [ABSTRACT FROM AUTHOR]

In this paper, a new method to calculate the self-inductance of the Archimedean spiral coil is presented. The proposed method is derived by solving Neumann’s integral formula, and the numerical tool is used to calculate the inductance value. The calculation results are verified with several conventional formulas derived from the Wheeler formula or its modified form and 3D finite element analyses. The comparison with simulation results shows that the conventional formula has an error of above 40% compared to the proposed method, which has below 7% when the wire diameter is reduced. To further check the validity, different sizes of the spiral coil are fabricated by changing the geometrical parameters such as the number of turns, turn spacing, inner radius, outer radius, and wire diameter. Litz wire is chosen for making the spiral coil, and bobbins are made using a 3D printer. Finally, the calculation results are compared with the experimental result. The error between them is less than 2%. The comparison with the conventional formulas, simulation, and measurement results shows the accuracy of the proposed method. This method can be used to calculate the self-inductance of wireless power coils, inductors and antenna design.

The torque profile of a double-stator permanent magnet (PM) synchronous machine of 90 mm stator diameter having different rotor pole numbers as well as dual excitation is investigated in this paper. The analysis includes a comparative study of the machine’s torque and power-speed curves, static torque and inductance characteristics, losses and unbalanced magnetic force. The most promising flux-weakening potential is revealed in 13- and 7-rotor pole machines. Moreover, the machines having different rotor/stator (Nr/Ns) pole combinations of the form Nr = Ns ± 1 have balanced and symmetric static torque waveforms variation with the rotor position in contrast to the machines having Nr = Ns ± 2. Further, the inductance results of the analyzed machines reveal that the machines with odd rotor pole numbers have better fault-tolerant capability than their even rotor pole equivalents. A prototype of the developed double-stator machine having a 13-pole rotor is manufactured and tested for verification.

Here, the authors present a magnetic circuit design with a multilayer air gap winding. This design provides a new degree of freedom in the design process. The approach is based on a single layer air gap winding, which demonstrates the ability to scale, permitting application in small and large electric machines. A meandering structure with coils arranged parallel to the rotation axis are mounted in several layers on a slotless magnetic core. The authors consider a fixed ohmic power loss boundary condition to compare this approach with an existing validated machine design. Machine current is reduced with each winding layer, while self-inductance and induced voltage are increased. Since the air gap height is increased with every additional layer, the useable magnetic flux density decreases. Accordingly, an utilisable range in which optimal torque output is obtained can be described analytically. The authors provide comparison between a single-layer winding design, which achieves the global optimum torque, and a four-layer winding design, which gives a 16-fold increase in the phase self-inductance. Additional thermal simulations prove that the multilayer design give the same ohmic power losses as the single layer design, without having any thermal issues and hot spots.

An accurate computational model of transformer winding for potential distribution analysis under impulse voltage is very important for the design of transformer inter-turn insulation, especially for large capacity transformers such as ultrahigh-voltage DC (UHVDC) converter transformer. Quite a lot of equivalent circuit models for transformer winding have been proposed assuming that the influence of magnetic core is negligible at frequencies >10 kHz, which is not always valid in practice. Lightning impulse or very fast transient overvoltage waveforms usually contain abundant frequency components >10 kHz. To obtain a more accurate model, here, a new equivalent circuit representation of UHVDC converter transformer winding is given taking into consideration of comprehensive frequency characteristic of core lamination stack. Taking account of the skin effect, the equivalent relative permeability of lamination stack are investigated and implemented in the calculation of frequency-dependent parameters such as resistance, self-inductance, and mutual inductance. The equivalent circuit model is realised in ATP and the surge propagation process in the winding; the winding potential distribution under transient overvoltage is studied carefully. The representation of the iron core loss in the equivalent circuit is discussed. The new proposed model may provide more accurate winding potential distribution prediction for transformer inter-turn insulation design.

An open-source tool that allows for a fast and precise analytical calculation of multi-layer planar coils self-inductance, without any geometry limitation is proposed here. The process of designing and simulating planar coils to achieve reliable results is commonly limited on accuracy and or geometry, or are too time-consuming and expensive, thus a tool to speed up this design process is desired. The model is based on Grover equations, valid for any geometry. The validation of the tool was performed through the comparison with experimental measurements, Finite Element Model (FEM) simulations, and the main analytical methods usually used in literature, with errors registered to be below 2.5%, when compared to standard FEM simulations, and when compared to experimental measurements they are below 10% in the case of the 1-layer coils, and below 5% in the 2-layer coils (without taking into consideration the coil connectors). The proposed model offers a new approach to the calculation of the self-inductance of planar coils of several layers that combines precision, speed, independence of geometry, easy interaction, and no need for extra resources.

Hazard identification in the construction industry is subject to a larger number of variables and unknowns than in other manufacturing industries making the hazard identification process more difficult and resulting in many injuries and fatalities. Moreover, previous research identified a research gap with regards to a universal hazard identification method. The results presented in this paper are a prerequisite for the development of such a method. Specifically, this paper proposes a novel classification of hazards in order to enable a more accurate hazard identification process which can take all possible hazards into consideration. Based on the theoretical framework, three hazard types are proposed in the research: self-induced hazards, peer-induced hazards, and global hazards. This classification is based on who is the source (who causes) the hazards in relation to who is affected by the hazards. Such classification was not identified in previous literature. This research also has practical implications. Such classification of hazards may influence safety experts to more actively focus on peer-induced hazards which are the hardest to identify. Finally, the outputs of the entire research should enable a more accurate and comprehensive hazard identification resulting in reduced injury and fatality rates in the construction industry. [ABSTRACT FROM AUTHOR]

This paper presents a novel initial rotor position estimation method for a surface-mounted permanent magnet synchronous motor (SPMSM) using its inherent magnetic features. Here, the initial rotor position has been estimated utilising the variation in phase inductances arising out of the unavoidable but very small saliency occurring either out of magnetic saturation of the machine or the magnet shape. Detailed investigations have been carried out to enumerate the actual magnitude of the inductances of the SPMSM with distributed armature winding and the dynamic saturation status with armature current variation. Here, 3-phase balanced voltage of higher frequency (150 Hz) is applied to the motor terminals for a short period of time (for 300 ms) and the corresponding phase currents are indirectly used to determine the rotor position. Innovative signal processing steps have been used to distinguish small differences in the 3-phase currents caused by the small differences in the phase inductances. The position is determined from the relative values of different phase currents using a novel approach. This still leads to two diametrically opposite (electrical phase) solutions for the instantaneous rotor position. To eliminate this ambiguity, two alternative methods (for pole identification) have been proposed. Extensive co-simulations of finite-element method (FEM)-based electromagnetic simulation and system simulation (for logic implementation) have been conducted. The estimation methods have been validated experimentally on a laboratory-developed prototype SPMSM that was designed and fabricated by the authors. The experimental results are found to be in excellent agreement with the FEM-based simulation results. The complete initial position estimation method takes less than 1 s of real time, which is typically less than the pre-charging time of standard commercial inverters. [ABSTRACT FROM AUTHOR]

The rise of choral singing as public performance in Shanghai during the mid-1930s was the result of overlapping historical developments and conditions. This study considers how new sound technologies, the introduction of new singing subjects as well as subject matter, and an acute sense of the nation in crisis converged to turn "community singing" into a fresh musical practice and generate a new sonic culture. Sound cinema in particular made new heroes visible as well as audible. Liu Liangmo, a secretary of the Young Men's Christian Association (YMCA) in Shanghai, was instrumental in initiating and promoting the community singing movement. His efforts, along with contributions by Lü Ji, a composer and music theorist of the cultural left, propelled the emergence of China as a "singing nation" by the outbreak of the War of Resistance against Japan in 1937. This process was an integral part of the cultural as well as political history of producing an articulate and audible subject against the soundscape of modernity. [ABSTRACT FROM AUTHOR]