Electromagnetic Force Research Articles

Electromagnetic Vibration and Noise Analysis of Linear Phase-Shifting Transformer

The advantages of adjustable angle phase-shifting and great expansibility make the linear phase-shifting transformer a novel type of power conversion device with a wide range of potential applications. However, during the procedure, there is a lot of noise. For the purposes of transformer design and vibration and noise reduction, it is crucial to investigate its electromagnetic vibration and noise. In this paper, the radial electromagnetic force wave considering the influence of the end effect as the source of the noise of the linear phase-shifting transformer was deduced and calculated. Based on this, the spectrum and space–time properties of the radial electromagnetic force waves were simulated and verified. Additionally, a finite element model was created using the Ansys Workbench 2022R1 platform to study the electromagnetic vibration and noise of the linear phase-shifting transformer. A joint simulation of the electromagnetic, structural, and sound fields was then performed. First, the transformer’s natural frequency was determined by modal analysis. After that, the transformer’s structure and the results of the transient electromagnetic field computation were combined and a harmonic response analysis was conducted to determine the vibration acceleration spectrum. Finally, in order to solve the sound pressure field, the transformer’s boundary vibration acceleration was coupled to the air domain. Furthermore, an analysis was conducted to determine the noise distribution surrounding the linear phase-shifting transformer. The joint simulation findings demonstrate that the linear phase-shifting transformer’s resonance, which produces larger electromagnetic vibration and noise, is indeed caused by the radial electromagnetic force. Simultaneously, the impact of the LPST core’s fixed components on the electromagnetic vibration and noise of the core was examined.

Enhancing the Precision of Proportional Electromagnetic Actuators used in Automatic Processes Control

In this study, an electromagnetic actuator is presented, that features precise proportional action and wide displacement capabilities. This actuator operates in two distinct modes. In the proportional mode, the actuator positions its mobile equipment within a 0 to 14 mm range, governed by the balance between electromagnetic force and spring elastic force. By employing the pulse width modulation (PWM) principle, the electronic control section finely tunes the duty cycle factor and the coil current, thus achieving precise displacement control. The displacement control was further enhanced through the integration of a magnetic sensor that correlates movement with the Hall Voltage. This additional feature augments the actuator's precision by providing real-time feedback on the position of the mobile equipment, thereby refining the overall control mechanism. In the modulated mode, the actuator's oscillation frequency spans from 1Hz to 10 Hz, requiring control from the arbitrary signal generator. The PWM waveform controller DRV101 and the related electronic circuits are powered by two stabilized encapsulated continuous voltage sources that are compact enough to fit inside the actuator housing. The final power stage was represented by two power IGBT transistors that are powered by an external continuous voltage source. Experiments were also realized for heat management and to measure the plunger force at different distances between 0 and 14 mm. These analyses aim to optimize performance across both operational modes, advancing the efficiency and reliability of precision control systems in automated processes.

Structural Deformation and Displacement of a Disc Winding Due to Standard Switching Impulse Voltage via Finite Element Method

Switching operations in a power system network can lead to transient overvoltage in the high voltage (HV) winding of distribution transformers that causes high-stress build-up. This paper presents the relationship between electromagnetic force due to a standard switching impulse (SSI) and mechanical deformation/displacement behaviours for a disc-type transformer. The analysis was carried out based on a three-dimensional (3D) modelling of a continuous HV disc winding configuration whereby it is subjected to the switching transient voltage and force excitations through the finite element method (FEM). The electric transient solver analysed the static and dynamic aspects of the electromagnetic forces associated with the variation of forces versus time. The transient structural solver evaluated the structural behaviours of the disc winding related to the axial height and radial width of the winding under electromagnetic forces. It is found that the positively dominant axial force generated in the winding with a magnitude of 8.7 N causes the top and bottom layers of disc winding to tilt and displace. In addition, the positive average radial force of 1.4 N causes the circumference of the winding to experience hoop tension and outwardly stretch.

Maglev for dark matter: Dark-photon and axion dark matter sensing with levitated superconductors

Ultraprecise mechanical sensors offer an exciting avenue for testing new physics. While many of these sensors are tailored to detect inertial forces, magnetically levitated (Maglev) systems are particularly interesting, in that they are also sensitive to electromagnetic forces. In this work, we propose the use of magnetically levitated superconductors to detect dark-photon and axion dark matter through their couplings to electromagnetism. Several existing laboratory experiments search for these dark-matter candidates at high frequencies, but few are sensitive to frequencies below 1 kHz (corresponding to dark-matter masses mDM≲10−12 eV). As a mechanical resonator, magnetically levitated superconductors are sensitive to lower frequencies, and so can probe parameter space currently unexplored by laboratory experiments. Dark-photon and axion dark matter can source an oscillating magnetic field that drives the motion of a magnetically levitated superconductor. This motion is resonantly enhanced when the dark matter Compton frequency matches the levitated superconductor’s trapping frequency. We outline the necessary modifications to make magnetically levitated superconductors sensitive to dark matter, including specifications for both broadband and resonant schemes. We show that in the Hz≲fDM≲kHz frequency range our technique can achieve the leading sensitivity among laboratory probes of both dark-photon and axion dark matter. Published by the American Physical Society 2024

Numerical and experimental analysis of magneto-convective flows around pipes

Liquid metal flows exposed to intense magnetic fields play a fundamental role in the development of blankets for nuclear fusion reactors, where they serve to produce the plasma-fuel component tritium and transport the generated heat. When the liquid metal circulates in the blanket, it interacts with the plasma-confining magnetic field leading to the induction of electric currents. Electromagnetic forces and thermal buoyancy affect significantly velocity and pressure distributions. The resulting magneto-convective flow has peculiar features that have to be taken into account in order to evaluate heat transfer properties in the liquid metal. In the breeding zone of the water-cooled lead lithium blanket concept, the volumetric heat released in the liquid metal is removed by water-cooled circular pipes that represent obstacles for the liquid metal flow. In order to improve the understanding of the underlying physical phenomena and obtain a database for code validation, model experiments have been performed to investigate magneto-convective flow and heat transfer at two differentially heated parallel horizontal tubes immersed in a box filled with liquid metal. Among other properties, electric potential has been recorded on the surface of the test-section and compared with 3D numerical simulations. Computational results provide the basis for interpretation of the measured data, since they allow differentiating between flow-induced electric potential and thermoelectric effects.

The effect of excitation current on radial electromagnetic force wave of tangential magnetizing parallel structure hybrid excitation synchronous motor

To study the influence of the magnitude of the excitation current on the radial electromagnetic force wave of the tangential magnetizing parallel structure hybrid excitation synchronous motor (TMPS-HESM) under different working conditions. Firstly, the basic structure of the motor and the rotor magnetic circuit model is introduced. Secondly, considering the influence of excitation current, the Maxwell stress tensor method is used to analyze the radial electromagnetic force wave of the motor and the source, frequency and order of the radial electromagnetic force wave that has a great influence on the electromagnetic vibration of the motor are qualitatively obtained. Then, the three-dimensional finite element method is used to calculate the variation law of the radial electromagnetic force wave when different excitation currents are applied under no-load and load conditions, revealing that the DC excitation will increase the amplitude of the radial electromagnetic force wave of a specific order. Meanwhile, the influence of load torque variation on the radial electromagnetic force wave is discussed, and it is found that the (2f, 8) and (6f, 24) order electromagnetic force waves are greatly affected by the armature reaction. The work provides a theoretical basis for further suppressing the electromagnetic vibration of this type of hybrid excitation motor.

Coupled translation and attitude tracking control for multi-satellite electromagnetic formation flight based on dual quaternion

Electromagnetic formation flight technology utilizes electromagnetic force and torque between satellites to control satellites’ relative position and attitude without consuming propellant, thus having broad application prospects. However, the dynamics of electromagnetic formation flying are nonlinear and strongly coupled, posing challenges to the 6-DOF control of electromagnetic formation and the magnetic dipole allocation of satellites. The frequency division multiplexing method can approximate decoupling formation dynamics by loading multi-frequency AC carriers onto satellite magnetic dipoles and is likely to achieve more control functions. A design method for AC carriers based on frequency division multiplexing is proposed to decouple formation dynamics while controlling electromagnetic force and torque. This paper further provides an analytical solution for the magnetic dipoles of the electromagnetic force/torque equations. In addition, in response to external disturbances, model uncertainty, and the inability to obtain relative velocity and angular velocity information of the formation system, this paper establishes a 6-DOF coupling model based on dual quaternion and implements tracking control using the active disturbance rejection control method. Based on the internal force characteristics of the electromagnetic formation, an expression for the equilibrium distribution of reaction wheel torque is derived to avoid some reaction wheels’ rapid accumulation of angular momentum. Numerical simulation results show the effectiveness of the proposed control method.

Towards a comprehensive characterization of spatio-temporal dependence of light-induced electromagnetic forces in dielectric liquids

The interaction of localized light with matter generates optical electrostriction within dielectric fluids, leading to a discernible change in the refractive index of the medium according to the excitation’s light profile. This optical force holds critical significance in optical manipulation and plays a fundamental role in numerous photonic applications. In this study, we demonstrate the applicability of the pump-probe, photo-induced lensing (PIL) method to investigate optical electrostriction in various dielectric liquids. Notably, the thermal and nonlinear effects are observed to be temporally decoupled from the electrostriction effects, facilitating isolated observation of the latter. Our findings provide a comprehensive explanation of optical forces in the context of the recently introduced microscopic Ampère electromagnetic formalism, which is grounded in the dipolar approximation of electromagnetic sources within matter and characterizes electrostriction as an electromagnetic-induced stress within the medium. Here, the optical force density is re-obtained through a new Lagrangian approach.

Thermal–Elastic–Magnetic Coupling-Induced Rubbing Behaviors of a Bladed Thin-Walled Rotor with Distributed Magnetic Actuators

A bladed thin-walled rotor with magnetic bearings in gas turbines has minimal wear to improve the service life. Especially, the rotor system can actively suppress vibrations. Yet, thermal–elastic–magnetic coupling-induced rubbing features of a bladed thin-walled rotor with magnetic bearings are not clear, and blade rubbing behaviors induced by high temperatures always occur in this kind of rotor. This paper establishes a new bladed thin-walled rotor model with distributed electromagnetic actuators to reduce thermoelastic vibrations and develops a solution approach for obtaining the thermal–elastic–magnetic coupling-induced rubbing characteristics of the rotor. The solution approach is verified, and the effectiveness of the distributed electromagnetic actuator model is demonstrated. The magnetic supports require two differential-control actuators at each position to generate the electromagnetic force, due to irregular concave–convex deformations of the rotor. Thereafter blade rub behaviors for the thin-walled rotor system are revealed. Uniform and smaller thermal deformations of the rotor system with the present actuator model avoid tip rub due to preventing thermal energy concentration. With the proper bearing capacity of a single actuator, an adequate number of actuators are required to ensure stability. The proposed theoretical prototype of the bladed thin-walled rotor with distributed electromagnetic actuators prevents blade rubbing caused by high temperatures. The provided solution approach can evaluate the vibration characteristics of a rotating thin-walled rotor with magnetic supports in the high-temperature environment.

Non-extensive (Tsallis) q-statistics and auroral glow

It is well-known that the auroral region of the magnetosphere–ionosphere interaction is an open, nonlinear dissipative system far from the equilibrium state. It is in this region that auroras are regularly observed, demonstrating not only a wide variety of dynamic forms but also a wide range of temporal and spatial scales. Due to the memory effects and fractal properties of auroral plasma, as well as strong correlations between its individual parts, the dynamics of the high-latitude system are primarily determined by long-range electromagnetic forces. Therefore, it is expected that non-additive and non-extensive thermodynamic principles may characterize their macroscopic behavior. In the presented study, it is shown that pulsating auroras exhibit non-extensive properties and can be described by q-statistics. The correlation of the parameter q with traditional indicators of nonlinear dynamics, such as the flatness coefficient, standard deviation, and scaling index, has been investigated. Small-scale changes are superimposed on large-scale processes characterized by a low correlation dimension, and this leads to an increase in the correlation dimension during geomagnetic activity, which approximately coincides with increased values of q. It is concluded that the q-statistics (Tsallis distribution) can be used to analyze optical phenomena in the auroral region.

Theoretically Motivated Dark Electromagnetism as the Origin of Relativistic Modified Newtonian Dynamics

The present paper is a modest attempt to initiate the research program outlined in this abstract. We propose that general relativity and relativistic MOND (RelMOND) are analogues of broken electroweak symmetry. That is, SU(2)R×U(1)YDEM→U(1)DEM (DEM stands for dark electromagnetism), and GR is assumed to arise from the broken SU(2)R symmetry and is analogous to the weak force. RelMOND is identified with dark electromagnetism U(1)DEM, which is the remaining unbroken symmetry after the spontaneous symmetry breaking of the dark electro-grav sector SU(2)R×U(1)YDEM. This sector, as well as the electroweak sector, arises from the breaking of an E8×E8 symmetry in a recently proposed model of unification of the standard model with pre-gravitation, with the latter based on an SU(2)R gauge theory. The source charge for the dark electromagnetic force is the square root of mass, motivated by the experimental fact that the ratio of the square roots of the masses of the electron, up-quark, and down-quark is 1:2:3, which is the opposite of the ratio of their electric charges at 3:2:1. The introduction of the dark electromagnetic force helps us understand the peculiar mass ratios of the second and third generations of charged fermions. We also note that in the deep MOND regime, acceleration is proportional to the square root of mass, which motivates us to propose the relativistic U(1)DEM gauge symmetry as the origin of MOND. We explain why the dark electromagnetic force falls inversely with distance, as in MOND, rather than following the inverse square of distance. We conclude that dark electromagnetism effectively mimics cold dark matter, and the two are essentially indistinguishable in cosmological situations where CDM successfully explains observations, such as CMB anisotropies and gravitational lensing.

Electromagnetic forming of AA1060 sheet based on mixed forces generated by a three-coil dual-power system

The electromagnetic force used in electromagnetic forming is mainly divided into attraction and repulsion. Dual-coil attractive electromagnetic forming can be used in the field of sheet pit repair. However, the magnetic field and eddy current generated by the two coils compete with each other, and the energy utilization rate is low. Therefore, a compensation coil is introduced, and an electromagnetic forming scheme of a three-coil dual-power sheet based on mixed force is proposed and verified by simulation. It is found that the three-coil mixed force can effectively improve the competition between the magnetic field and eddy current. The loading of the mixing force is not a simple superposition of attraction and repulsion, but the mutual promotion of the two. The forming displacement of the three-coil mixed force forming scheme is 582% higher than that of the dual-coil attraction forming scheme, and 89% higher than that of the attract first and then repel forming scheme. The forming effect of the three-coil mixing force is related to the number of turns of the compensation coil. The research results can improve the energy utilization rate of electromagnetic forming and provide a new idea for the loading scheme of electromagnetic forming force field.

Nonlinear motion characteristics of the high-temperature superconducting levitation system with boundary crack

High-temperature superconducting levitation systems have nonlinear behaviors, such as the period-doubling bifurcation and chaotic vibration under external excitation, in connection with the nonlinear hysteresis interaction between the high-temperature superconductors (HTSC) and permanent magnet. The HTSC is a non-ideal type II superconductor in which the fracture is generated internally during manufacturing, and the material properties are brittle. The HTSC tends to crack under a strong magnetic field and electromagnetic force, and its internal defects are likely to cause structural damage with the variable Lorentz force. The fracture performance of the superconducting magnetic levitation system will affect the temperature variation of HTSC, in which the temperature is coupled with the internal electromagnetic force. In this paper, we analyze the fracture characteristics of the HTSC in nonlinear vibration with thermal effect. A superconducting magnetic levitation system model with boundary cracks is applied to study the coupling of multiple physical fields in dynamic processes. The Maxwell equation and superconducting electromagnetic constitutive equation are used to obtain the superconductor’s current density, and the temperature is calculated through the heat conduction equation. The superconducting magnetic flux flow and creep model is applied to analyze the magnetic flux motion inside the superconductors. We compare the superconducting levitation system’s electromagnetic force, temperature, and current density with four critical current densities. The numerical results show that the critical current density of superconductors significantly impacts bifurcation motion, and the temperature of the crack tip of the superconductors varies greatly during vibration, causing the superconductor to lose its superconductivity.

Reconstruction methods for super-resolution imaging with PSF modulation

Recently, a super-resolution imaging method called the PSF (point spread function) modulation method was developed (Lu, IEEE TUFFC 2024). In this method, the amplitude, phase, or both of the PSF of a linear shift-invariant (LSI) imaging system is modulated so that the modulated PSF has a higher spatial frequency than that of the original PSF to reconstruct super-resolution images. The modulator can be produced and manipulated remotely by methods such as radiation force or it can be a physical particle such as micro- or nano-particle manipulated by an external force such as electrical and electromagnetic force. In principle, the super-resolution imaging method can be applied to any LSI imaging system, such as ultrasound, optical, photoacoustic, electromagnetic, underwater, nondestructive evaluation (NDE), and magnetic resonance imaging (MRI) system. These include pulse-echo ultrasound imaging, transmission imaging, wave source/field imaging, acoustical camera, and optical bright-field microscope. To optimize the quality of the images, methods for the reconstruction of pulse-echo and wave source/field super-resolution images are studied and the results will be presented. These methods include the uses of an analytic envelope of radio-frequency (RF) signals with and without windowing, “I” (in-phase) and “Q” (quadrature) signals, and the DC (direct current) component removal.

Comparative study on heteropolar/homopolar magnetic bearings for high-speed rotating applications

Bearing technology must be supported to attain high-speed and high-efficiency rotating applications. Previous research focused on performance enhancement and optimization, rather than comparative studies among magnetic bearings. This study presents the design and comparison of five magnetic bearing types for high-speed rotating applications: an 8-pole conventional heteropolar, fork-type heteropolar, hybrid fork-type homopolar, and hybrid homopolar magnetic bearings. For quantitative evaluation, mechanical parameters were selected to ensure a uniform coil volume and current supply. The heteropolar magnetic bearings employed 35PN440 steel, whereas the homopolar magnetic bearings utilized pure solid iron. The bias currents were determined based on the respective material properties. The driving circuits were compared by comparing models with and without permanent magnets. The magnetic flux density was assessed at equilibrium and maximum control current, and the loss characteristics were evaluated at 30 000 rpm. Linear control regions were identified by analyzing the relationships between the electromagnetic force, current, and displacement. As a result, the most suitable magnetic bearing for high-speed rotating applications is proposed.

Permanent Magnet Electrodynamic Suspension System Integrated With a Car: Design, Implementation, and Test

In this paper, a permanent magnet electrodynamic suspension (PMEDS) system integrated with a car has been developed by our group, along with a 100-m-long test track made of copper. The entire vehicle weighs 2.8 ton and is freely suspended in air over 35 mm without a lateral constraint on guideway. The car uses its own wheels and engine to provide a take-off speed for the PMEDS system, eliminating the excessive costs of the motor, with a maximum speed of 70 km/h. Firstly, a new topology structure equipped with the damping magnets is presented. Afterward, the onboard magnets and guideway are designed via the simulation method verified by the high-speed rotary experiment platform with a diameter of 2500 mm, clarifying the mapping between the electromagnetic forces and structure parameters. The suspension frame and gap adjustment mechanism are developed, and a complete test system is built to monitor the levitation gap, accelerations and deflection angle. Lastly, the integrated PMEDS system is implemented and tested. In-house experiment and line test results not only reveal that the PMEDS has a significant weak guidance capability, but also confirm the effectiveness of the proposed damping magnets. Through the damping magnets, the maximum lateral deflection is limited to less than 11°. The tested levitation-drag-ratio is in general agreement with the simulation results. The great suspension capacity of the PMEDS system can be visually demonstrated. This paper conducts the free suspension test of the PMEDS system for the first time in China, which can open up prospects for further engineering applications.

Investigation and Suppression of Cogging Torque of Permanent Magnet Homopolar Inductor Machine

Cogging torque (CT) would cause the vibration and noise of the permanent magnet homopolar inductor machine (PMHIM), which should be suppressed. However, the unipolar air-gap flux density and the dual-segment stator and rotor cores of PMHIM make the characteristics of CT unclear, which leads to a lack of theoretical basis for suppressing the CT. Addressing this issue, the CT of PMHIM is investigated and suppressed. Firstly, the model of CT of PMHIM with integer and fractional slot configurations is developed, and the factors affecting the CT are revealed. Then, the methods for suppressing the CT are proposed based on changing rotor parameters. The influences of different rotor parameters on electromagnetic performance, including back electromagnetic force (EMF), output torque, current and efficiency are fully analyzed. In addition, the characteristics of the proposed method are highlighted by comparing the performance of the method proposed in this paper with the global optimization method in terms of CT suppression. Finally, the theoretical analyses are validated by experiments. The results show that the CT of PMHIM can be effectively suppressed by the proposed method in this work.

Analysis of guidance and levitation forces between HTS magnets and conductive tubes for Hyperloop

High-temperature superconducting (HTS) magnets combined with linear synchronous motors and electrodynamic suspension (EDS) are considered as one of the most suitable technologies for Hyperloop. However, HTS magnets on pods generate strong magnetic fields, inducing eddy currents on conductive tubes when pods undergo movement through conductive tubes. The induced eddy currents affect HTS magnets, leading to electromagnetic (EM) drag, guidance, and levitation forces on the pods, thus reducing the propulsion efficiency and dynamic stability of pods. This study continues the existing research on EM drag forces between HTS magnet and tube for Hyperloop by comprehensively analyzing the EM guidance and levitation forces between HTS magnets and conductive tubes. Importantly, the full-scale 3D finite element analysis (FEA) simulations show that different steel tubes, such as AISI 1010 and high-manganese (Hi-Mn) steels, should be adopted, depending on the operating velocities, v, to avoid attractive forces in the guidance direction decreasing horizontal stiffnesses, For example, Hi-Mn tubes generating repulsive guidance forces are adopted when v is below 300 km/h while AISI 1010 tubes are used when v is over 300 km/h to minimize the construction cost of vacuum tubes to guarantee the increase in kx. For the proposed concept, the effect of the different tube connections on guidance and levitation forces is confirmed by the full-scale 3D FEA simulation. Moreover, levitation forces generated between HTS magnets and conductive tubes are nearly 0.5% of the EDS forces of pods, i.e., 200 kN over v of 150 km/h in the levitation direction. Therefore, the effect on vertical stiffnesses, ky, might be limited. In the end, to validate the proposed tube connections, the effect of the two different tube connections on guidance and levitation forces is confirmed by the full-scale 3D FEA simulation, and it was found that the sudden change in the guidance and levitation forces could be low enough to be neglected in the acceleration (from Hi-Mn to AISI 1010 steel tubes) and deceleration (from AISI 1010 to Hi-Mn steel tubes) regions.

Neoclassical Theory of Atoms

The "Neoclassical Theory of Atoms" challenges the dominance of quantum mechanics in explaining certain atomic phenomena. This work argues that a classical approach, utilizing electromagnetic Coulomb forces and Newtonian mechanics, can potentially account for discrete energy levels and spectral lines observed in hydrogen and helium atoms. It questions the necessity of invoking the seemingly counterintuitive aspects of quantum mechanics for these specific phenomena. By demonstrating the potential of a classical framework, this research aims to stimulate debate and exploration of alternative explanations within physics. This could potentially lead to a deeper understanding of the nature of reality and the limitations (or potential for expansion) of current physical theories.

Analysis of Vibration and Noise in Electric Drive System Under Resolver and Motor Rotor Coupling Eccentricity

Eccentricity in a permanent magnet synchronous motor (PMSM) can cause additional electromagnetic forces and resolver error, which in turn can lead to an aggravation of vibration and noise in the electric drive system. In this paper, the additional electromagnetic forces and the resulting vibration and noise under the conditions of the three-dimensional (3-D) static and dynamic motor eccentricities, the resolve error, and the coupling between these faults, are analytically derived and analyzed, with special emphasis on the coupling effect of the motor eccentricity and resolver error. The results of the present theoretical analyses agree well with those from the finite element simulations and the experimental measurements. It can be concluded from the results that the coupling between the 3-D motor eccentricity and the resolver error will induce additional electromagnetic forces with much more diverse spatial orders and frequencies.