Magnetic Rotation Research Articles

Electromagnetic field coupled circuits and open‐loop control of fast starting processes in induction motors

AbstractTo solve the problems of difficulty in speed measurement and low accuracy of speed measurement of induction motor (IM) during fast starting, the electromagnetic field coupling circuit (EFCC) and open‐loop control of IM considering rapid speed change are proposed. First, the EFCC of IM is established through the stator circuit, air gap magnetic field circuit and rotor circuit, and the stator voltage and electromagnetic torque of the fast starting process are deduced from the air gap magnetic density on the basis of constant slip angular velocity, and then the open‐loop control method based on the EFCC is given. Finally, compared with the open‐loop control based on the TEC, the results of simulation and experiment show that the open‐loop control based on the EFCC can follow the acceleration starting more quickly and the starting current is smaller, which is conducive to reducing the cost of the drive.

A piezoelectric and electromagnetic hybrid energy harvester based on two-stage magnetic coupling

Traditional piezoelectric energy harvesters cannot adapt to environmental energy with low frequency, wideband, and randomness because of the narrow working bandwidth. The introduction of magnetic coupling can improve the narrow-band characteristics of piezoelectric energy harvesting structures. To explore more efficient broadband methods, this paper designs a piezoelectric and electromagnetic hybrid energy harvester (PEEH) based on two-stage magnetic coupling to realize the expansion of piezoelectric energy harvesting bandwidth. In this paper, the magnetic pole alternating frequency is changed and the output of the structure is tested, and the operating frequency bands under different alternating frequencies are compared according to the test results. It can be seen from the experimental results that the output performance of the structure is obviously improved by increasing the AC frequency of the magnetic pole while reducing the optimal frequency point of the structure. When the number of magnets in the rotor magnet array is 6, increasing the pole alternating frequency can effectively improve the output performance of the electromagnetic unit when the rotor speed is low, and can also increase the maximum output voltage and energy harvest bandwidth of the piezoelectric unit by 189% and 150%, respectively. Therefore, by increasing the alternating frequency of magnetic poles, the output voltage of the structure can be improved, and the bandwidth of the structure can be broadened.

Kinetic‐Scale Current Sheets in the Solar Wind at 5 AU

AbstractWe present statistical analysis of 16,903 current sheets (CSs) observed over 641 days aboard Ulysses spacecraft at 5 AU. We show that the magnetic field rotates across CSs through some shear angle, while only weakly varies in magnitude. The CSs are typically asymmetric with statistically different, though only by a few percent, magnetic field magnitudes at the CS boundaries. The data set is classified into about 90.6% non‐bifurcated and 9.4% bifurcated CSs. Most of the CSs are proton kinetic‐scale structures with the half‐thickness of non‐bifurcated and bifurcated CSs within respectively 200–2,000 km and 500–5,000 km or 0.5–5λp and 0.7–15λp in units of local proton inertial length. The amplitude of the current density, mostly parallel to magnetic field, is typically within 0.05–0.5 nA/m2 or 0.04–0.4JA in units of local Alfvén current density. The CSs demonstrate approximate scale‐invariance with the shear angle and current density amplitude scaling with the half‐thickness, and . The matching of the magnetic field rotation and compressibility observed within the CSs against those in ambient solar wind indicate that the CSs are produced by turbulence, inheriting its scale‐invariance and compressibility. The estimated asymmetry in plasma beta between the CS boundaries is shown to be insufficient to suppress magnetic reconnection through the diamagnetic drift of X‐line. The presented results will be of value for future comparative analysis of CSs observed at different distances from the Sun.

Analysis of hyperbolic magneto-hydrodynamic [HMHD] wave propagation through neutrino-coupled plasma

By using the Hyperbolic Magneto Hydrodynamic model, we investigated the propagation dynamics of a neutrino-coupled plasma system, with the influence of Hall current, rotation, viscosity and finite electrical resistivity. The general dispersion relation is obtained from the perturbed equations for both the Jean’s and neutrino beam instability. The effect of different parameters has been discussed in both parallel and perpendicular modes of wave propagation. The Jean’s instability condition is modified due to the presence of Hall current, Magnetic field and neutrino in both modes of propagation. The growth rate of the neutrino beam is affected by Hall current, viscosity magnetic field and rotation in both propagating modes. We also show the effect of different parameters on the growth rate of a neutrino-coupled plasma system through a graphical presentation.

A neural network inverse problem solution for a MIMO magnetic levitation actuator

A multiple-input and multiple-output planar actuator is proposed, which utilizes mechanically driven stator magnet arrays to levitate a permanent magnet mover. A state of levitation and actuation is obtained by mechanically altering the orientation of the stator magnets to control the forces and torques on the mover. A challenge for the design and control of the actuator is inverting the relationship between the force and stator magnet rotation angles, as there is no closed-form analytical solution. In this study, a feed-forward neural network is applied to model the forward relation between stator magnet angle input and a force and torque output to reduce the forward computation time for the design process and for error estimation in real-time applications. Additionally, the neural network is considered for inverting the solution for a motion profile sampled at 1000 Hz. The developed forward model is able to calculate the forces and torques on the mover a factor 10 faster than the equivalent charge or Fourier model with an absolute error of 3 mN and 0.1 mNm for the forces and torques, respectively, and a feed-forward neural network is able to accurately learn an inverse solution for small motion profiles.

Design and optimization of a radial-axial hybrid excited machine with spoke-type permanent magnet rotor

To further enhance the speed regulation range of the hybrid excited machine (HEM), the structure of a magnetic ring is optimized using a combination of the magnetic circuit method (MCM) and numerical analysis method in this paper, and a disc magnetic ring (DMR) is proposed. The magnetic density distribution of the proposed disc magnetic ring hybrid excited machine (DMRHEM) is compared to the radial-axial hybrid excited machine (RAHEM), and the superiority of alleviating a saturation problem in the proposed DMRHEM is determined. To improve the power density, the spoke-type permanent magnet (PM) rotor is applied. The influence of the proposed DMR on the HEM is analyzed, and the field adjustment capability of the proposed DMRHEM is better. Based on this, by combining the bypass principle, the analytical expressions for the relations between the rotor pole-pair number and the motor axial length/stator inner diameter (MAL/SID) as well as flux regulation capability are derived to further explore the superiority of the proposed DMRHEM. The influence mechanism of the rotor pole-pair number and the MAL/SID on the proposed DRMHEM is determined. The optimal MAL/SID and pole-pair number are obtained.

Selecting the Best Permanent Magnet Synchronous Machine Design for Use in a Small Wind Turbine

The article describes the selection of a permanent magnet synchronous machine design that could be implemented in a small wind turbine designed by the GUST student organization together with researchers working at the Technical University of Lodz. Based on measurements of the characteristics of available machines, eight initial designs of machines with different rotor designs were proposed. The size of the stator, the number of pairs of poles, and the dimensions of the magnets were used as initial parameters of the designed machines. The analysis was carried out about the K-index, the so-called index of benefits. The idea was to make the selected design as efficient as possible while keeping production costs and manufacturing time low. This paper describes how to select the best design of a permanent magnet synchronous generator intended to work with a small wind turbine. All generator parameters were selected keeping in mind the competition requirements, as the designed generator will be used in the author’s wind turbine. Based on the determined characteristics of the generator variants and the value of the K-index, a generator with a latent magnet rotor was selected as the best solution. The aforementioned K-index is a proprietary concept developed for the selection of the most suitable generator design. This paper did not use optimization methods; the analysis was only supported by the K-index.

Whistler‐Mode Wave Generation During Interplanetary Shock Events in the Earth's Lunar Plasma Environment

AbstractWhistler‐mode waves are commonly observed within the lunar environment, while their variations during Interplanetary (IP) shocks are not fully understood yet. In this paper, we analyze two IP shock events observed by Acceleration, Reconnection, Turbulence and Electrodynamics of the Moons Interaction with the Sun (ARTEMIS) satellites while the Moon was exposed to the solar wind. In the first event, ARTEMIS detected whistler‐mode wave intensification, accompanied by sharply increased hot electron flux and anisotropy across the shock ramp. The potential reflection or backscattering of electrons by the lunar crustal magnetic field is found to be favorable for whistler‐mode wave intensification. In the second event, a magnetic field line rotation around the shock region was observed and correlated with whistler‐mode wave intensification. The wave growth rates calculated using linear theory agree well with the observed wave spectra. Our study highlights the significance of magnetic field variations and anisotropic hot electron distributions in generating whistler‐mode waves in the lunar plasma environment following IP shock arrivals.

Piezo‐Turned Magnet Rotation for ELF/SLF Cross‐Medium Communication in Omni‐Direction

AbstractExtremely/super low frequency (ELF/SLF) electromagnetic (EM) waves offer efficient propagation in challenging cross‐medium environments. However, conventional coil antennas, when emitting ELF/SLF EM waves, face constraints related to size, radiation efficiency, and high power consumption. To overcome these limitations, a disc‐rod structured piezoelectric rotating resonator is proposed, which can turn a NdFeB permanent magnet disc into rotation with an impressive high‐speed up to 10 000 r min−1 via wobbling motion of the rod tip, effectively generating ELF/SLF magnetic field radiation via rotational oscillation other than common linear and swinging oscillation of the magnetic dipole moments. The piezo‐turned magnetic rotation (PTMR) method leads to a two to five‐fold enhancement in magnetic field emission compared to existing piezo‐actuated acoustic resonant antennas, and a 370 times higher emitting efficiency compared to the traditional coil antenna with a comparable size. In contrast to unidirectional EM wave radiation at their solely resonant frequencies, the PTMR antenna showcases omnidirectional B‐field radiation with continuous tunability in a dual frequency band spanning from 10 to 100 Hz. Moreover, an air–seawater cross‐medium magnetic field communication is successfully demonstrated. With outstanding performance metrics, the PTMR antenna emerges as a promising solution for efficient long‐distance ELF/SLF cross‐medium communication.

Diagnostics of Interior PM Machine Rotor Faults Based on EMF Harmonics

This article presents a detailed study on the diagnosis of rotor faults in an Interior Permanent Magnet Machine based on a mathematical model. The authors provided a wide literature review, mentioning the fault diagnosis methods used for Permanent Magnet Machines. The research emphasizes the necessity of precise assumptions regarding winding construction to accurately analyze the additional harmonics appearing in rotor faults caused by electromotive force (EMF), i.e., rotor eccentricity and magnet damage. The article also discusses specific features appearing in the spectrum of air gap permeance functions and the impact of rotor eccentricity and magnet damage on PM flux density distribution and as a consequence on EMF stator windings. The novelty of the presented content is the analysis of induced EMFs for cases of the simultaneous occurrence of rotor eccentricity and PM damage. The findings of this study provide valuable insights for the diagnosis and understanding of internal asymmetries in Interior PM Machines.

Quantum Sensing Can Already Make a Difference. But Where?

Quantum sensing technology is already providing value and potential use cases can shape multiple industries. There are four core technologies with promising applications - solid state spins, neutral atoms, superconducting circuits, and trapped ions - which have sensing capabilities across a broad range of physical properties, including magnetic fields, electric fields, rotation, temperature, gravity, time, and pressure. Which quantum sensing technology and implementation type to use depends on the use case, as they measure different properties and are best suited to specific environments. This paper discusses the potential and current applications of the abovementioned quantum sensing technologies through varied use-case studies. They are presented around four specific industries and along different time horizons, emphasizing the need for further development and enhancement that can be achieved over the conventional counterparts. The full power of quantum sensors is not yet known, but they have the potential to create an entire new ecosystem if researchers, start-ups, and industry leaders work together to explore their applications and get them out of the lab. Here, the paper outlines necessary actions and possible avenues for the stakeholders to realize this potential across academia and industry.

Research on the fiber intensity modulation model of superconducting magnetic levitation rotor.

The measurement of the pole axis deviation angle of superconducting magnetic levitation rotors plays a crucial role in the field of high-precision navigation. This article conducts theoretical analysis and experimental research on the diffuse reflection intensity modulation principle of optical fiber sensors and the ideal diffuse reflection modulation model under ideal conditions. First, the structural distribution of optical fiber sensors is presented, and the principle of measuring the polar deviation angle of superconducting magnetic levitation rotors is analyzed. Then, based on the diffuse reflection intensity modulation principle, an optical fiber intensity modulation model for ideal superconducting magnetic levitation rotors is established. The correctness of this model was verified through simulation and calibration experiments, and the error between the simulation and experimental results was less than 8%.

Evolution of the magnetic field rotation distributions in the inner heliosphere

The nature and evolution of the solar wind magnetic field rotations is studied in data from the Parker Solar Probe We investigated the magnetic field deflections in the inner heliosphere below 0.5 au in a distance- and scale-dependent manner to shed some light on the mechanism behind their evolution. We used the magnetic field data from the FIELDS instrument suite to study the evolution of the magnetic field vector increment and rotation distributions that contain switchbacks. We find that the rotation distributions evolve in a scale-dependent fashion. They have the same shape at small scales regardless of the radial distance, in contrast to larger scales, where the shape evolves with distance. The increments are shown to evolve towards a log-normal shape with increasing radial distance, even though the log-normal fit works quite well at all distances, especially at small scales. The rotation distributions are shown to evolve towards a previously developed rotation model moving away from the Sun. Our results suggest a scenario in which the evolution of the rotation distributions is primarily the result of the expansion-driven growth of the fluctuations, which are reshaped into a log-normal distribution by the solar wind turbulence.

Search of effective interaction in dipole bands of an odd–odd trans-lead Nucleus: the case of 204At

Role of effective interaction potential in shears band structure in [Formula: see text]At has been investigated in more detail than in previous studies. A semi-classical geometric model is used to obtain the interaction strengths between valence protons and neutron holes constituting the shears blades. The value produces overall good agreement with this region’s nuclei. Band crossing is observed in the spin-parity range [Formula: see text] – [Formula: see text]. Configurations of the Magnetic Rotational (MR) band are assigned in the light of the Shears mechanism with the Principal Axis Cranking (SPAC) model. Experimental rotational frequencies and the deduced ratio of [Formula: see text] are well reproduced by SPAC calculations, suggesting the dipole band in [Formula: see text]At can undoubtedly be interpreted as the MR band resulting from the effective interaction of repulsive potential.

Self-Calibration Method of Displacement Sensor in AMB-Rotor System Based on Magnetic Bearing Current Control

Displacement sensors are the key components of the active magnetic bearing rotor (AMB-rotor) system to realize the closed-loop control of the rotor displacement. The aging and failure of the displacement sensor components will lead to the changes of sensor sensitivity and zero point, which can directly affect the suspension performance of the rotor and even cause the instability of the AMB-rotor system. Therefore, it is significant to calibrate the sensor regularly. This paper proposes a self calibration method based on the detection and control of the magnetic bearing current without additional calibration equipment and hardware circuits. In addition, a new control structure of the AMB-rotor system is proposed to achieve efficient calibration, which can control the rotor displacement based on current following control method. Finally, experimental results verify the effectiveness of the proposed method on the displacement sensor calibration.

Sliding model control of active magnetic bearing rotor system based on state observer

This paper addresses a novel sliding mode control based on state observer for active magnetic bearing rotor system. Firstly, the state-space model of a radial AMB rotor system is established with considering unbalance disturbance and gyro effect for a vertical flywheel energy storage system. Then a sliding mode function and switching surface are constructed based on an observer. Meanwhile, a separation and decoupling strategy based on Finsler’s lemma is proposed. Through this method, the constraint relationship between the controller gain, active magnetic bearing matrices and the Lyapunov variables is eliminated. After that a method for chattering reduction in the sliding-mode controller is raised. Relied on these techniques, new sufficient conditions for the stability of AMB rotor system are given in the framework of linear matrix inequalities. Finally, the effectiveness of the proposed sliding mode controller is validated on the experimental platform of the flywheel energy storage system.

Cumulative Data of 1H and 13C NMR Signals and Specific Rotations of Eremophilane Sesquiterpenoids. 4. 10H-3-O-Furanoeremophilanes

1H and 13C nuclear magnetic resonance (NMR) data and specific rotations of eremophilane sesquiterpenoids are cumulated as a series of review articles. This fourth chapter focuses on furanoeremophilanes bearing 10H with C-3 oxygen functionality, and 175 10H-furanoeremophilanes with 3-O functionality are listed in 38 tables. Those with 15,6-lactones and 6,15-ethers are included in this chapter. Dihydrofurans, lactols, dimers, nor- and seco-compounds, and other related compounds, are not included in this chapter. These data may help chemists working in the area of natural products chemistry and synthetic scientists as well as computational chemists.

Torque Calculation and Dynamical Response in Halbach Array Coaxial Magnetic Gears through a Novel Analytical 2D Model

Coaxial magnetic gears have piqued the interest of researchers due to their numerous benefits over mechanical gears. These include reduced noise and vibration, enhanced efficiency, lower maintenance costs, and improved backdrivability. However, their adoption in industry has been limited by drawbacks like lower torque density and slippage at high torque levels. This work presents an analytical 2D model to compute the magnetic potential in Halbach array coaxial magnetic gears for every rotational angle, geometry configuration, and magnet specifications. This model calculates the induced torques and torque ripple in both rotors using the Maxwell Stress Tensor. The results were confirmed through Finite Element Analysis (FEA). Unlike FEA, this analytical model directly produces harmonics values, leading to faster computational times as it avoids torque calculations at each time step. In a case study, a standard coaxial magnetic gear was compared to one with a Halbach array, revealing a 14.3% improvement in torque density and a minor reduction in harmonics that cause torque ripple. Additionally, a case study was conducted to examine slippage in both standard and Halbach array gears during transient operations. The Halbach array coaxial magnetic gear demonstrated a 13.5% lower transmission error than its standard counterpart.

Impact of magnet shape and material on the magnet stress

AbstractMagnet cracking is a common issue in external rotor motors. To investigate the causes of magnet cracking and propose solutions, the authors consider the effects of magnet shape, magnet and yoke material fit on the motor rotor magnets, perform a static analysis of the motor rotor. The simulation and test results show that the stress distribution of tile‐shaped magnets is better than that of rectangular magnets. The highest safety margin of 56.41% is achieved for the magnet and yoke material fit of DT4/N35(EH). The maximum force of the permanent magnet (PM) exceeds 22.38% of the stress limit when the material fit is DT4/SmCo28, which can lead to cracks in the PM. The results of this paper have important reference significance for the structural design of the external rotor motor and their safe and reliable operation.

Systematic study of magnetic and antimagnetic rotational bands

The magnetic and antimagnetic rotational bands are systematically investigated in the present work. Up to now, 253 magnetic rotational bands and 40 antimagnetic rotational bands have been reported in 123 nuclei and 29 nuclei, respectively. The experimental data for these bands are collected and collated, including the level energy, γ-ray energies, spin I, magnetic dipole reduced transition probability B(M1), electric quadrupole reduced transition probability B(E2), B(M1)/B(E2), and J (2)/B(E2), etc. In addition, following the presentation of the kinematic moment-of-inertia J (1), dynamic moment-of-inertia J (2), and I versus rotational frequency ω, as well as energy staggering parameter S(I), B(M1), B(E2), B(M1)/B(E2), and J (2)/B(E2) versus I in A ∼ 60, 80, 110, 140, and 190 mass regions, a discussion is provided in detail. Based on the systematic studies, the main features of magnetic and antimagnetic rotational bands are summarized. Furthermore, some nuclei are also predicted to be candidates for magnetic or antimagnetic rotation.