Magnetic Field Coupling Research Articles

Analysis of Power Transfer Characteristics of IPT System With Near Field Magnetic Coupling

This article investigates the working principle of the inductive power transfer (IPT) system from the perspectives of electromagnetic field distribution. According to the limitations of frequency and transmission distance, it is proved in this paper that the IPT system works in the near field, where the energy density of the magnetic field is much stronger than that of the electric field. Therefore, only the magnetic field in the IPT system needs to be considered in approximate power analysis. The mutual inductance model of the IPT system is an approximate and simplified form of the electromagnetic field model. The complex form of the Poynting vector of the IPT system is integrated over an intermediate infinite plane of the two coils to reveal the power transfer characteristics including the active and reactive power. When the system is in full resonance, only active power is transferred without reactive power, which is consistent with the results obtained from the circuit model. This article is useful to provide an insight into the power flow and energy distribution of the IPT system.

Higher-order magnetic skyrmions in nonuniform magnetic fields

For a two-dimensional Hubbard model with spin-orbit Rashba coupling in external magnetic field the structure of effective spin interactions is studied in the regime of strong electron correlations and at half-filling. It is shown that in the third order of perturbation theory, the scalar and vector chiral spin-spin interactions of the same order arise. The emergence of the latter is due to orbital effects of magnetic field. It is shown that for nonuniform fields, scalar chiral interaction can lead to stabilization of axially symmetric skyrmion states with arbitrary topological charges. Taking into account the hierarchy of effective spin interactions, an analytical theory on the optimal sizes of such states, the higher-order magnetic skyrmions, is developed for axially symmetric magnetic fields of the form $h(r)\ensuremath{\sim}{r}^{\ensuremath{\beta}}$ with $\ensuremath{\beta}\ensuremath{\in}\mathbb{R}$.

Modulational instability in vector exciton-polariton condensates with photonic spin-orbit coupling

The paper demonstrates the existence of modulational instability (MI) in nonlinear exciton-polariton condensates (EPCs). A set of coupled two-dimensional (2D) driven-dissipative Gross-Pitaevskii equations describing the spin-up and spin-down polaritons, containing the photonic spin-orbit (SO) coupling and the rate equations describing the density of incoherent excitonic reservoir density, is reduced to a system of two coupled 2D complex Ginzburg-Landau (2DCGL) equations, with saturable nonlinearities for complex polariton order parameters, thanks to the adiabatic approximation and small density fluctuations approximation. The analytical approach relies on the linear stability analysis of continuous waves (CWs) to derive an expression for the growth rate and conduct a parametric study of MI. The effect of different parameters on the growth rate spectrum is discussed with an emphasis on the photonic SO coupling and the pumping power. The predictions are verified against a direct simulation of the 2DCGL equations, and excellent agreement is found. The emergence of solitonic clusters manifests the evolution of MI. Phase diagrams on a MI spectrum for the CWs are presented against the magnetic field ($B$) and SO coupling strength ($\ensuremath{\sigma}$), based on which the dynamical behaviors of the emerging structures are debated, along with their response to changing $\ensuremath{\sigma}$ and $B$. The results suggest that the photonic SO coupling and the magnetic field constitute efficient tools for nonlinear mode selection and characterization via the MI process and are equally important in any eventual experimental realization of such a process in the studied EPC system.

Design of a Brushless Doubly Fed Generator With Simplified Three-Phase Wound Rotor

The brushless doubly fed generator (BDFG) shows great potential for the variable speed constant frequency ship shaft power generation applications due to its high reliability and low system costs. The rotor topology, which directly couples two stator magnetomotive forces (MMFs) with different pole pairs, is essential for the BDFG. However, existing rotor topologies cannot have both strong magnetic field coupling ability and simple structure. To address this problem, this paper proposes a simplified three-phase wound rotor that can produce two MMFs with different pole pairs simultaneously. Useless harmonics are also eliminated to achieve strong magnetic field coupling ability. The complete design method of a novel integral-slot single-layer winding acting as a basic unit of the compound wound rotor is presented. Two sets of basic winding units are merged into one according to the principle of Ampere-conductor wave, whose approaches are also thoroughly developed with the design example. The maximum number of winding layers and the coil types are reduced to simplify the winding layout. Steady-state performances of a prototype generator are analyzed by both finite element simulations and experimental tests, which verify proposed design methods and schemes.

Improvement of Faraday Rotation and Its Application in Preconditioned Single-Wire Z-Pinch Plasma

Magnetic field measurement in Z-pinch plasma has drawn considerable interest because it is a key problem in the research of dynamic behaviors and the coupling of magnetic field and plasma. In this study, the measurement sensitivity of the rotation angle in Z-pinch plasma was improved by considering the second polarization effect caused by optical elements. The magnetic field distribution of preconditioned single-wire Z-pinch plasma was determined by this method. The Faraday rotation of the 1064-nm probe laser was measured by the beam-splitting polarization method when the plasma acted as a Faraday medium. A second polarization effect on the rotation angle was realized by taking the different transmittances and reflectivities of the <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$p$</tex-math> </inline-formula> and <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$s$</tex-math> </inline-formula> components of the beam splitters into account. This configuration doubled the sensitivity of the Faraday rotation measurement. The diagnostic errors produced by the techniques and data processing were quantified. The early stage of the preconditioned imploding plasma was monitored, and the distributions of areal electron density, Faraday rotation, and magnetic field were measured. The experimental results demonstrated that the current distribution can be divided into three parts by two dense shells. The majority of the current was distributed outside the dense shell which existed inside the coronal plasma. In addition, only a small amount of current was distributed in the wire core.

Features of flow and heat transport of MoS2+GO hybrid nanofluid with nonlinear chemical reaction, radiation and energy source around a whirling sphere

The current investigation employs a numerical simulation to demonstrate the impact of hall current on unsteady free convective flow caused by hybrid-nanofluid over a revolving sphere approaching the stagnation point. The prominent characteristics of Lorentz force as a result of magnetic field coupling with hybrid nanofluid is also explored. The process of energy and mass transmission is inspected with nonlinear thermal radiations, non-uniform energy supply, dissipation and nonlinear chemical reaction. In current flow model, a unique class of nanofluid known as the hybrid nanofluid is being used, which contain GO (graphene oxide) and MoS2 (molybdenum disulfide) with water. The angular speed of both the sphere and free stream changes frequently with time. Employing adequate dimensionless variables, the partial-differential patterns strongly non-linear that represent the situational analysis are morphed into non-linear ordinary differential patterns. The analytical outcomes of ordinary differential pattern have been developed via OHAM technique. Utilizing tables and graphs, various aspects of such controllable physical characteristics have been highlighted and explored in depth. For varying values of M,φ,δ,Sc and Kn,the variations in Cfx, Cfz,Nu and Sh in MoS2-GO/H2O are the greatest as contrasted to MoS2/H2O. The results are also compared to those reported existing literature and they are noticed to be in very close agreement.

Experimental Study of Transmission Coil Configuration for Omnidirectional Power Transfer in Magnetic Field Coupling Type Contactless Power Transfer

In magnetic field coupling type contactless power transfer, there is a problem that stable power transfer is not possible to changes in the position, angle, and distance of the transmission and receiving coils. In the case of mobile devices charging the battery using the contactless power transfer, the angle between the power transmission and receiving coils is not constant. Therefore, the power transmission efficiency is influenced by changing the position between the power transmission and receiving coils. In this study, the shape of the power transmission coils was investigated with stably supply power in all directions to mobile devices. We studied three coils consisting of cubic coil with 4 squares connected in parallel(4 squares cubic coil), cubic coil with 4 L-shapes connected in parallel(L4 cubic coil) and octagonal star prism coil with 8 square coils connected in parallel(octagonal star prism coil) . The S-parameters between the transmission and receiving coils were measured using a Vector Network Analyzer and after converting S-Parameters to Z-parameters. The theoretical maximum efficiency was obtained from the kQ product and compared with different coil shapes.

AWOA: An Advanced Whale Optimization Algorithm for Signal Detection in Underwater Magnetic Induction Multi-Input–Multi-Output Systems

With the increasing exploitation and use of marine resources, the limitations of acoustic, optical, and radio frequency technologies for underwater communications have become increasingly apparent. Magnetic induction (MI) is a new communication technology that enables wireless data transmission via magnetic field coupling between transmitting and receiving coils. MI offers advantages such as channel stability, small antenna size, and no multi-path loss. Multi-input–multi-output (MIMO) is a multi-antenna technology that significantly increases system capacity and spectrum utilization without increasing bandwidth. The whale optimization algorithm (WOA) is a well-known bio-inspired algorithm that mimics the hunting behavior of whales to optimize swarm intelligence. This paper proposes a model for an underwater MIMO communication system based on magnetic induction. We then construct a signal detection algorithm for MI-MIMO systems using the advanced whale optimization algorithm (AWOA) and conduct simulation experiments to compare the performance and complexity of three standard signal detection algorithms: zero-forcing (ZF), minimum mean square error (MMSE), and maximum likelihood (ML). The experimental results show that AWOA achieves suboptimal results, as its bit error rate (BER) is close to that of the ML algorithm. Furthermore, the complexity of AWOA is comparable to that of the MMSE strategy. This work supports the development of a high-performance MI-based underwater communication system.

Phase transition of three-dimensional finite-sized charged dust clusters in a plasma environment.

The dynamics of a harmonically trapped three-dimensional Yukawa ball of charged dust particles immersed in plasma is investigated as function of external magnetic field and Coulomb coupling parameter using molecular dynamics simulation. It is shown that the harmonically trapped dust particles organize themselves into nested spherical shells. The particles start rotating in a coherent order as the magnetic field reaches a critical value corresponding to the coupling parameter of the system of dust particles. The magnetically controlled charged dust cluster of finite size undergoes a first-order phase transition from disordered to ordered phase. At sufficiently high coupling and strong magnetic field, the vibrational mode of this finite-sized charged dust cluster freezes, and the system retains only rotational motion.

Non-Contact Measurement Method of Phase Current Based on Magnetic Field Decoupling Calculation for Three-Phase Four-Core Cable

As one of the important parameters characterizing the cable’s operation status, an accurate measurement of the current is particularly important for the cable’s reliable operation and status monitoring. Aiming at the problem that the sum of the current phasors of multiphase cables is 0 when running in a steady state, and that the traditional mutual inductance current measurement method cannot be used for the phase current measurement of such cables, or that the insulation layer needs to be damaged, this paper proposes a non-contact measurement method of three-phase cable current, based on the magnetic field decoupling calculation. When combined with the actual parameters of the three-phase cable, the analytical calculation model of the magnetic field distribution of the three-phase cable is established. The relationship between the output ratio of the sensor and the deflection angle is obtained through theoretical derivation, the magnetic field coupling coefficient matrix is determined, and the transfer relationship between the output of the magnetic sensor and the current of each phase is clarified; an array magnetic field sensor is designed, which can sense the information of the adjacent magnetic field independently and is used for the reconstruction of three-phase currents. The effectiveness of the proposed method was tested on the built three-phase four-core cable current measurement test platform. The experimental results show that under the three-phase current balance, the measurement error of phase A, phase B and phase C is less than 2.8%, and the waveform and phase angle of the three-phase current can be well restored, which verifies the three-phase current measurement method proposed in this paper.

On the non-minimal coupling of magnetic fields with gravity in Schwarzschild spacetime

In this work we study the effects of non-minimal coupling between electromagnetism and gravity, which are motivated by quantum effects such as vacuum polarization. We investigate the modification of both asymptotically dipole and uniform magnetic fields around a Schwarzschild black hole that come as the result of non-minimal coupling. While in both cases the magnetic field gets enhanced or suppressed with respect to the case of minimal coupling, depending on the sign of non-minimal coupling parameter, in the case of a background uniform magnetic field the direction of the magnetic field also alters in the vicinity of the black hole horizon. We have discussed the possible astrophysical and cosmological sources for which the vacuum polarization may be at play, while also discussing the observational effects, in particular the possibility of synchrotron radiation from the vicinity of a black hole. We conclude that such observations could be used to constrain the value of the non-minimal coupling parameter.

A novel method for fabricating of high-performance multi-seeding GdBCO bulk superconductors

A novel multi-seeding (NMS) method is proposed for improving the performances of GdBCO samples by optimizing the shapes and the space configurations of the single-domain GdBCO grains. Three multi-seeding GdBCO bulk superconductors with dimensions of 60 × 20 × 14 mm3 were fabricated by a Gd + 011 infiltration growth method with different seeding techniques: samples S1 and S2 by the traditional multi-seeding method (TMS) with two and three seeds, respectively; and sample S3 by the NMS method with three seeds. The results show that among the three, sample S3 has both of the largest levitation force, 111 N, and the largest magnetic field coupling ratio, 68.57%, which are clearly higher than the levitation force of 100 N and 90 N, and the magnetic field coupling ratios of 34.25% and 11.33% for the samples S1 and S2, respectively. These results indicate that the NSM method is a useful way to improve the mechanical strength, homogeneity, and performances of multi-seeding GdBCO samples.

Study on the surface integrity in ultrasonic vibration and magnetic field complex assisted low speed WEDM under different magnetic field coupling

In this paper, a complex process of ultrasonic vibration (USV) and magnetic field (MF) complex assisted WEDM-LS is proposed, which provides a new method to solve the problems of low machining efficiency and poor machining surface integrity of traditional WEDM-LS. The self-generated MF of wire electrode is taken as the medium, and the influence mechanism of USV and additional MF on the intensity of self-generated MF is explored. Firstly, combined with the Galvanomagnetic effect and Biot-Safar Law, the mathematical models of self-generated MF under USV assisted WEDM-LS and USV-MF assisted WEDM-LS were deduced respectively. And then the MF coupling law between inter electrode was revealed; Secondly, the distribution of self-generated MF of wire electrode under different working conditions was simulated and analyzed. The results showed that compared with traditional WEDM-LS, the self-generated magnetic density under USV assisted WEDM-LS and USV-MF assisted WEDM-LS was increased by 12.1 % and 17.5 % respectively. As a result, the volume of single discharge crater was increased by 12.3 %; Finally, Taguchi orthogonal method was used to complete the USV-MF assisted WEDM-LS orthogonal experiment and the MF coupling verification experiment. The results showed that the Ra was reduced by 23.8 % and the MRR was increased by 25.1 % compared with the traditional working condition. The number of microcracks and micropores on the workpiece surface was significantly reduced, and the degree of workpiece surface burn was effectively reduced, which showed that the surface integrity of the workpiece had been greatly improved. The verification experiment results showed that compared with the opposite coupling of the self-generated MF and the additional MF, when the self-generated MF and the additional MF were coupled in the same direction, the Ra of the workpiece surface was reduced by 18.21 % and the feed speed was increased by 16.68 %. In addition, the removed particles were more evenly adsorbed on the surface of the wire electrode, which increased the normal discharge probability, indicating that the inter electrode MF coupling was the main effect model of ultrasonic vibration and MF recombination.

Modular Electromagnetic Transducer for Optimized Energy Transfer via Electric and/or Magnetic Fields.

In this paper, a modular electromagnetic transducer that achieves the optimal transfer of energy from the electric and/or magnetic fields is proposed. Both the magnetic field resonance coupling and the influence of the electric field near the copper transducers of the printed circuit board and inside the FR4-type epoxy material are considered. In our printed arrays of flat transducers, we consider face-to-face capacitances for the study of resonance coupling. Because the space between coil turns is almost double the plate thickness, the coplanar capacitance can be ignored for frequencies under 2 MHz. A radio frequency (RF) transmitter and transducer were built to demonstrate the increased energy transfer efficiency when using both electric and magnetic fields in the near-field region. The transversal leakage flux coupling of a long RF coil was more efficient than a simple axial magnetic field coupling when using pancake transceiver coils. The optimal configuration having one long coil at the base and two or more flat coils as capacitor plates near coil ends generated the highest tandem of magnetic and electrical fields. A power regression tool was used to convert and simplify the transducer current and voltage variation with distance. In this regard, the current change corresponded to magnetic field variation and the voltage change to the electric field variation. New formulas for estimating the near-field region and the self-capacitance of the RF transformer coil are proposed; the optimal function in the frequency domain for a given transducer distance was defined by simulation.

Bubbling of Ferrofluid Droplets via Coupled Magnetic and Sound Fields

AbstractBubbles play essential roles in many natural and industrial processes because of the unique effects of their films on heat–mass transfer and their soft confined geometry for interfacial assembly or phase transitions. Here, a technique for noncontact bubbling via coupling of sound and magnetic fields in acoustic levitation is reported. An acoustically levitated ferrofluid droplet can be transformed into a closed bubble in a controlled manner. It has been found that the magnetic field pulls the flattened ferrofluid film downward, and making it deviate from its initial levitation position determined by the balance between acoustic radiation force and gravity. This results in variation in acoustic radiation pressure on the film surface and generates an upwards torque on the levitated film, leading to buckling and subsequent bubble transition via acoustic resonance. Moreover, the levitated ferrofluid bubble can remain unburst in the sound field for minutes to enable its complete evaporation; thus, solid hollow shells form. This work provides insight for understanding the coupled effect of sound and magnetic fields on ferrofluid drops and sheds light on evaporation‐driven self‐assembly of ferrofluid particles into shell structures

The effects of spin-orbit coupling on optical properties of monolayer text {MoS}_{2} due to mechanical strains

We have studied the optical conductivity of a quasi two-dimensional text {MoS}_{2} in the presence of external magnetic field and spin-orbit coupling. Specially, we address the frequency dependence of optical conductivity due to spin-orbit interaction. Using linear response theory the behavior of optical conductivity has been obtained within Green’s function method. We have also considered the effects of uniaxial and biaxial in-plane strain on the optical absorption of text {MoS}_{2} layer. In the absence of external magnetic field with negative uniaxial strain parameter, optical conductivity includes Drude weight at zero frequency limit while Drude weight vanishes for text {MoS}_{2} layer under positive uniaxial strain. Our results show that the increase of uniaxial positive strain parameter causes to move the position peak to the higher frequencies. In contrast to uniaxial strain case, the Drude weight in optical conductivity appears at positive biaxial strain value 0.15. Also we have studied the effects of magnetic field, electron doping, hole doping in the presence of spin-orbit coupling on frequency dependence of optical conductivity of text {MoS}_{2} in details. The magnetic field dependence of optical absorption shows a monotonic decreasing behavior for each value of temperature in the absence of strain parameter.

Partial-inductance retarded partial coefficients: Their exact computation based on the Cagniard–DeHoop technique

The Partial Element Equivalent Circuit (PEEC) method is a well recognized integral-equation (IE) technique to solve Maxwell’s equations. Similarly to the method of moments (MoM), the electromagnetic (EM) interactions between currents and between charges are described in terms of integrals. In contrast to the standard MoM, the PEEC method keeps the electric and magnetic coupling phenomena separate, which leads to different interaction integrals to be computed. These integrals admit simplified solutions for the case of the static free-space Green’s function and orthogonal geometries but their applicability is limited to electrically small problems only. When the full-wave free-space Green’s function is considered, the integrals are typically computed in the frequency domain (FD) by resorting to Gaussian quadrature schemes. The accuracy and efficiency of such schemes is a delicate issue. Therefore, recent works have investigated the possibility of applying the Cagniard–DeHoop (CdH) technique to calculate the interaction integrals for zero-thickness elementary domains. In this paper, we close the loop and shall apply the CdH technique to calculate the partial-inductance between two elementary bricks as prescribed by the PEEC technique exactly in the time domain (TD). The analytical approach is demonstrated on the interaction between two bricks as it occurs in the modeling of the magnetic field coupling between volumetric currents. The accuracy of the proposed approach is (successfully) tested for two representative cases.

A compact dual-sense circularly polarized SIW textile antenna for body-centric wireless communication

In this communication, a dual-sense circularly polarized textile antenna that operates at the centre frequency of 5.8 GHz is presented for body-centric wireless communication. The proposed textile antenna is realized using a substrate integrated waveguide (SIW) cavity. Circular polarization is achieved by exciting two orthogonal quarter mode apertures in 900 phase differences. A metallic via is employed to control the magnetic field coupling between the two orthogonal quarter mode apertures. The feed point and dimensions of two-quarter mode apertures can be changed to realize both left-hand and right-hand circular polarization. The proposed textile antenna has a 4.8 % impedance bandwidth covering from 5.62 to 5.90 GHz. Moreover, the textile antenna has a 2.9 % 3 dB axial ratio bandwidth covering from 5.725 to 5.875 GHz frequency bandwidth. The textile antenna has exhibited good reflection characteristics when bent on the surface of a cylindrical structure. The textile antenna has a lesser than 1.27 W/Kg SAR value in the proximity of the human phantom model for a 1 W source and also has exhibited a minimum peak gain of 5 dBi, making it conducive for integration with body-centric wireless communication.

Research on comprehensive optimization strategy of transformer thermal life in digital substation

With the national advocacy and vigorous promotion of new digital infrastructure, digital assessment of transformer operation state based on digital twin technology has become one of the hot issues in the power field. In this paper, taking an oil immersed transformer as an example, the magnetic, current and thermal multi field coupling numerical analysis method is used to simulate and analyze the operation state of the transformer, monitor the multi state characteristic parameters of the transformer through sensors, integrate the numerical simulation analysis results with the state monitoring results, and build a transformer thermal life loss evaluation system. This method can evaluate and analyze the operation status of transformers in real time, which is of great significance for power companies to formulate governance measures. It can effectively support the national new digital infrastructure strategy and contribute to the national strategy while satisfying the normal operation of power grid enterprises.

Analysis on magnetic coupling characteristics and carrying capacity of superconducting rotor magnetic levitation structure

The high-speed rotating superconducting rotor can be used as a sensor to measure angular speed or angular position. Mass unbalance and oblateness of superconducting rotor are the main error sources to measure angular speed or angular position. General Electric company has developed an superconducting rotor magnetic suspension device with an accuracy of 0.005&lt;sup&gt;° &lt;/sup&gt;per hour, but its rotor structure is very complex. So it is difficult to process and assemble with extremely small mass-unbalance and small oblateness, which limits the further improvement of its accuracy. According to this, in this paper we introduce a magnetic support structure with a simple superconducting rotor compared with rotor made by General Electric company. The rotor sphere is a closed structure with no theoretical mass eccentricity. Its electromagnetic structure is simpler than General Electric company’s, and the stator coil is the torquer coil at the same time. The stator coil is used to accelerate the rotor, while the torquer is used to make the rotor erect. Based on the theory of superconducting electrodynamics and the finite element method, the characteristics of the magnetic suspension structure are analyzed. The magnetic field coupling effect of the stator and the suspension coils on the surface of the superconducting rotor are studied, and their influence on magnetic supporting force is also analyzed. The current direction of the two suspension coils should be opposite, otherwise the rotor will produce forced vibration, which will make it difficult to accelerate the superconducting rotor. Then the magnetic circuit theory and the finite element method are used to model the magnetic circuit of the magnetic levitation structure, and the critical carrying capacity of the magnetic suspension structure is calculated and the optimal suspension conditions are given. Finally, a method to optimize its carrying capacity is designed. Therefore, the currents of the suspension coils are controlled by the acceleration of superconducting cavity. Through this method, the maximum bearing capacity of the magnetic levitation structure can be increased by 78% compared with that of fixed optimal suspension current support. The analysis results provide a reference for the structural design and optimization of the superconducting rotor magnetic levitation system.