Flux Reversal Research Articles

Investigation and Analysis of Force Production Mechanism for Partitioned Stator Flux Reversal Permanent Magnet Linear Machine

Investigation and Analysis of Force Production Mechanism for Partitioned Stator Flux Reversal Permanent Magnet Linear Machine

Capacity for instantaneous catabolism of preferred and non-preferred carbon sources in Escherichia coli and Bacillus subtilis

Making the right choice for nutrient consumption in an ever-changing environment is a key factor for evolutionary success of bacteria. Here we investigate the regulatory mechanisms that enable dynamic adaptation between non-preferred and preferred carbon sources for the model Gram-negative and -positive species Escherichia coli and Bacillus subtilis, respectively. We focus on the ability for instantaneous catabolism of a gluconeogenic carbon source upon growth on a glycolytic carbon source and vice versa. By following isotopic tracer dynamics on a 1–2 minute scale, we show that flux reversal from the preferred glucose to non-preferred pyruvate as the sole carbon source is primarily transcriptionally regulated. In the opposite direction, however, E. coli can reverse its flux instantaneously by means of allosteric regulation, whereas in B. subtilis this flux reversal is transcriptionally regulated. Upon removal of transcriptional regulation, B. subtilis assumes the ability of instantaneous glucose catabolism. Using an approach that combines quantitative metabolomics and kinetic modelling, we then identify the additionally necessary key metabolite-enzyme interactions that implement the instantaneous flux reversal in the transcriptionally deregulated B. subtilis, and validate the most relevant allosteric interactions.

Magnetic Gearing as a Functional Principle in Electric Drives

The partitioned stator flux reversal machine (PS-FRPM) is a novel stator PM machine topology, which exhibits a higher torque capability than its single stator counterpart and the conventional permanent magnet synchronous machine (PMSM). The PS-FRPM consists of two stators, one which carries the armature winding, and one which is equipped with surface mounted permanent magnets. The rotor is sandwiched between the two stators. The separation of the stator allows a better utilization of the machine volume which results in a higher torque density. Furthermore, because the magnets are placed on a stationary component, they can be cooled effectively. Consequently, critical rare-earth materials can be saved.The structure of the PS-FRPM is very similar to that of magnetic gears. In this paper the torque production of a PS-FRPM is described by means of the magnetic gearing effect. First the magnetic gearing effect is introduced and then the corresponding analytics is transferred to the PS-FRPM. Based on Maxwell's stress tensor, the torque contributions of the individual space harmonics are determined. In contrast to conventional machines, the torque in PS-FRPM is produced by several space harmonics in both air gaps.

Subduction flux modulates the geomagnetic polarity reversal rate

Ascertaining the cause of variations in the frequency of geomagnetic polarity reversals through the Phanerozoic has remained a primary research question straddling paleomagnetism and geodynamics for decades. Numerical models suggest the primary control on geomagnetic reversal rates on 10 to 100 Ma timescales is the changing heat flux across the core-mantle boundary and that this is itself expected to be strongly influenced by variations in the flux of lithosphere subducted into the mantle. A positive relationship between the time-dependent global subduction flux and magnetic reversal rate is expected, with a time delay to transmit the thermal imprint into the lowermost mantle. We perform the first test of this hypothesis using subduction flux estimates and geomagnetic reversal rate data back to the early Paleozoic. Subduction area flux estimates are derived from global, full-plate tectonic models, and are evaluated against independent subduction flux proxies based on the global age distribution of detrital zircons and strontium isotopes. A continuous Phanerozoic reversal rate model is built from pre-existing compilations back to ~320 Ma plus a new reversal rate model in the data-sparse mid-to-early Paleozoic. Cross-correlation of the time-dependent subduction flux and geomagnetic reversal rate series reveals a significant correlation with a time delay of ~120 Ma (with reversals trailing the subduction flux). This time delay represents a value intermediate between the seismologically constrained time expected for a subducted slab to transit from the surface to the core-mantle boundary (~150–300 Ma), and the much shorter lag time predicted by some numerical models of mantle flow (~30–60 Ma). While the reason for this large discrepancy remains unclear, it is encouraging that our novel estimate of lag time represents a compromise between them. Although important uncertainties in our proposed relationship remain, these results cast new light on the dynamic connections between the surface and deep Earth, and will help to constrain new models linking mantle convection, the thermal evolution of the lowermost mantle and the geodynamo.

Overview of novel magnetically geared machines with partitioned stators

This study overviews recent development of a new class of magnetically geared machine topologies, i.e. partitioned stator (PS) machines. They are developed from magnetic gears and magnetically geared machines, as well as stator permanent magnet (PM) machines (switched flux, flux reversal, and doubly saliency PM), wound field, or hybrid PM and field winding machines. Based on the operating principle, i.e. magnetic gearing effect/air-gap field modulation and flux switching by the salient rotor iron poles, various PS machine topologies are developed. All have features of two stators, two air-gaps, and one segmented ferromagnetic rotor identical to a magnetic gear's modulating rotor. Their inherent relationships are revealed, while their electromagnetic performance is compared. Both PM and wound field PS machines are discussed, together with hybrid excited PS-PM machines and Vernier machines. It shows that all of these PS machines share the same torque production principle and the differences are mainly in PM configurations and relative positions of two stators. All PS machines have higher torque density per copper loss compared with their counterparts of single-stator machines. PS switched flux PM machines can produce the highest torque density per copper loss.

Thermal Metamaterials for Heat Flow Control in Electronics

Rapid advancement of modern electronics has pushed the limits of traditional thermal management techniques. Novel approaches to the manipulation of the flow of heat in electronic systems have potential to open new design spaces. Here, the field of thermal metamaterials as it applies to electronics is briefly reviewed. Recent research and development of thermal metamaterial systems with anisotropic thermal conductivity for the manipulation of heat flow in ultra-thin composites is explained. An explanation of fundamental experimental studies on heat flow control using standard printed circuit board (PCB) technology follows. From this, basic building blocks for heat flux cloaking, focusing, and reversal are reviewed, and their extension to a variety of electronics applications is emphasized. While device temperature control, thermal energy harvesting, and electrothermal circuit design are the primary focus, some discussion on the extension of thermal guiding (TG) structures to device-scale applications is provided. In total, a holistic view is offered of the myriad of possible applications of thermal metamaterials to heat flow control in future electronics.

Vibration analysis including stator, rotor, housing and dynamic response analysis of Flux Reversal Generator

This paper attempts to present numerical solution for the vibration analysis of a Flux Reversal Generator (FRG). A three-dimensional finite-element modal analysis (3-D FEA) methodology has been used for this purpose. Vibrations induced due to mechanical and unbalanced reasons have been analyzed. The 3-D modal analysis undertaken identifies the vibrations caused in every part of FRG (stator, shaft, end shields, bearings, and housing), which has been systematically documented. Modal frequencies and the respective speeds which are to be skipped immediately in order to operate the machine always in a safer acoustic zone have been identified and tabulated. To fine tune this, a harmonic analysis has been performed. Up to 10,000Hz has been considered and frequencies (and proportional speeds) such as 1500Hz, 1488.62Hz and 1568.78 have identified as the speeds to be avoided. Apart from frequently reported modal analysis on electrical machines, this 3-D vibration analysis for FRG considering every part of the machine will be helpful to examine the vibration in the machine as a whole. This forms the claim of the paper.

Design and Analysis of a Flux Reversal Machine With Evenly Distributed Permanent Magnets

In this paper, a flux reversal machine (FRM), which has a larger torque density and a smoother torque waveform than the conventional FRM, is introduced. The FRM has the same combinations of stator and rotor slots, winding pole pair, and permanent magnet (PM) usage as the conventional FRM, but has different PM arrangements, i.e., in the conventional FRM, a pair of PMs is mounted on the surface of each stator teeth while the PMs of the FRM introduced in this paper are evenly distributed along the inner surface of the stator. First, the origination from the conventional FRM to the proposed FRM is introduced. Then, the effects of the rotor slot number, split ratio, stator/rotor slot opening ratio, PM thickness, and pole arc on the average torque and cogging torque are investigated and analyzed, which give a reasonable prediction for maximum achievable power density and minimum possible cogging torque of the proposed FRM. Moreover, the proposed FRM is compared with a conventional FRM in terms of back electromotive force, rated torque, pulsating torque, power factor, and overload capabilities. Finally, a 12-stator-slot/17-rotor-slot FRM prototype is built to verify the theoretical analyses.

A Novel Hybrid Excitation Flux Reversal Machine for Electric Vehicle Propulsion

A novel hybrid excitation flux reversal machine (HEFRM) is developed for application in electric vehicle propulsion. The proposed machine has a simple reluctance rotor and a stator with conventional ac armature windings and concentrated dc field windings. Besides, there are also permanent magnets (PMs) on the stator teeth. The PMs on each tooth have the same polarity, and the PMs on the adjacent two teeth have different polarities. In this paper, the feasible slot–pole combinations and equivalent circuits of the HEFRM are introduced, and the influences of several key design parameters such as rotor slot number, ratio of field winding to total winding, ferromagnetic pole arc, stator slot opening ratio, and rotor slot opening ratio on torque density and power factor are investigated by finite-element algorithm. Moreover, to verity the advantages of the hybrid excitation, the torque–speed envelop and power factor–speed envelop of the proposed HEFRM are compared to that of its solely PM excited counterpart. Finally, an HEFRM prototype is built and tested to validate the theoretical analysis.

What Confines the Rings of Saturn?

Abstract The viscous spreading of planetary rings is believed to be counteracted by satellite torques, through either an individual resonance or overlapping resonances. For the A ring of Saturn, it has been commonly believed that the satellite Janus alone can prevent the ring from spreading, via its 7:6 Lindblad resonance. We discuss this common misconception and show that, in reality, the A ring is confined by the contributions from the group of satellites Pan, Atlas, Prometheus, Pandora, Janus, Epimetheus, and Mimas, whose cumulative torques from various resonances gradually decrease the angular momentum flux transported outward through the ring via density and bending waves. We further argue that this decrease in angular momentum flux occurs through “flux reversal.” Furthermore, we use the magnitude of the satellites’ resonance torques to estimate the effective viscosity profile across the A ring, showing that it decreases with radius from ∼50 cm2 s−1 to less than ∼10 cm2 s−1. The gradual estimated decrease of the angular momentum flux and effective viscosity are roughly consistent with results obtained by balancing the shepherding torques from Pan and Daphnis with the viscous torque at the edges of the Encke and Keeler gaps, as well as the edge of the A ring. On the other hand, the Mimas 2:1 Lindblad resonance alone seems to be capable of confining the edge of the B ring, and contrary to the situation in the A ring, we show that the effective viscosity across the B ring is relatively constant at ∼24–30 cm2 s−1.

Design Procedure of Flux Reversal Permanent Magnet Machines

Flux reversal permanent magnet machines (FRPMMs) exhibit many advantages such as simple rotor configuration, high torque density, fast transient response, etc. However, the general analytical design procedure of FRPMMs has not been established. Thus, this paper mainly focuses on developing an analytical design methodology of three-phase FRPMMs. First, the sizing equations are derived based on a magneto motive force-permeance model. Then, the influences of several key parameters in the sizing equation, including slot-pole combination, airgap radius, electric loading, and equivalent magnetic loading on the torque density, are analyzed. Moreover, the feasible slot-pole combinations are summarized and the corresponding winding type of each combination is recommended in order to maximize the output torque. Additionaly, the detailed geometric design of stator and rotor is presented. Finally, the proposed analytical design procedure is verified by finite element analysis and experiments on a 12-stator-slot/17-rotor-slot FRPMM prototype.

Large-eddy simulations of dense-gas dispersion within a high-Reynolds number turbulent boundary layer

Large-eddy simulations of flows over a backward-facing step with release of four different gases with increasing densities have been performed. The results have been analysed with particular emphasis on the part of the flow field sufficiently far downstream where the local effect of the source dynamics is no longer dominating the flow field. The dense gas plumes maintain high concentrations close to the ground and become approximately twice as shallow in comparison with a neutrally buoyant plume. The vertical mixing is significantly reduced close to the ground, and both momentum and scalar flux reversal are found in the two densest cases, indicating negative shear and buoyancy production of turbulence kinetic energy. Examination of the gradient Richardson number indicates that all dense gases are significantly affected by buoyancy. Interestingly, a narrow layer within the plumes is identified where the impact of stratification is expected to be reduced. It is found that relaminarization is most likely occurring and that fluctuations found might originate from interfacial wave modes rather than from turbulence. The large-scale structures are seen to resemble those found in the plane channel flow close to the wall and further away from it. In the middle layer, significant differences are found due to buoyancy effects. The large-scale structures become more pancake-shaped with large-scale vorticity almost exclusively about the spanwise direction in the dense gas cases.

Comparative Analysis of Partitioned Stator Flux Reversal PM Machine and Magnetically Geared Machine Operating in Stator-PM and Rotor-PM Modes

In this paper, the partitioned stator flux reversal permanent magnet (PM) (PS-FRPM) machine and the conventional magnetically geared (MG) machine operating in both stator-PM (SPM) and rotor-PM (RPM) modes are comparatively analyzed in terms of electromagnetic performance to provide design guides for an MG machine regarding an SPM- or RPM-type machine and a higher or lower gear ratio machine. It is found that an SPM-type machine is recommended since both PS-FRPM and MG machines operating in SPM modes have a higher phase back-EMF and hence torque than their RPM counterparts, respectively, as a result of a similar phase flux linkage but a higher electric frequency since the iron piece number is larger than the PM pole-pair number. Moreover, a smaller gear ratio machine is preferred from the perspective of a higher power factor and hence a lower inverter power rating, as the conventional MG machines with higher gear ratios suffer from larger flux-leakage, higher synchronous reactance and hence lower power factors, as well as higher iron losses, than the PS-FRPM machines. However, higher gear ratio machines feature lower cogging torques and torque ripples due to the smaller difference between the PM pole-pair number and iron piece number. Both prototypes of PS-FRPM machine operating in SPM mode and MG machine operating in RPM mode are built and tested to verify the finite element predicted results.

Introductory assessment of a novel high‐torque density axial flux switched reluctance machine

A novel structure of switched reluctance machines (SRMs) is proposed in this study. The proposed structure uses the advantages of the axial flux path, short flux path, segmental rotor, and flux reversal free stator machines all together to improve the torque density of the SRMs. The main geometrical, electrical and physical specifications are presented. In addition, some features of the proposed structure are compared with those of a state-of-the-art radial flux SRM, considered as a reference machine. Achieved results reveal that, compared with the reference machine, the proposed machine delivers about the same torque, albeit employing considerably lower volume and active material mass. These make the proposed structures a potentially proper candidate for traction and propulsion applications demanding high-torque density machines.

3-D Analytical Analysis of Magnetic Field of Flux Reversal Linear-Rotary Permanent-Magnet Actuator

This paper develops a 3-D analytical model to compute the no-load magnetic-field distribution in a flux reversal linear-rotary permanent-magnet actuator (FR-LRPMA) with two permanent-magnet (PM) poles (PM_pole) and two ferromagnetic poles (Fe_pole) on each stator tooth. Laplace's and Poisson's equations are built assuming that the stator and the rotor are slotless and both the permeances of Fe_pole and PM_pole are the same. The tubular mover is transferred into a planar one using a curvature factor. Then a 2-D model and 3-D model for calculating the air-gap relative permeances are proposed considering the effect of slot and the permeance difference of Fe_pole and PM_pole, respectively. The expressions of 3-D magnetic flux density, cogging force, and cogging torque of the FR-LRPMA are subsequently derived and verified using the finite-element method.

Effect of atomic flux reversal in a fluctuating moving optical lattice

The dynamics of an ensemble of noninteracting cold atoms is considered in the field of a moving optical lattice subjected to random amplitude and phase fluctuations. The effect of the reversal of an atomic ensemble under the action of lattice fluctuations is demonstrated, in which the atoms begin to move in the direction opposite to that of the lattice motion. A kinetic model is constructed that reproduces this effect and makes it possible to relate its emergence to the asymmetry of the amplitudes of the interlevel transitions in a momentum space.

Torque Performance Analysis of Three-Phase Flux Reversal Machines

Flux reversal machines (FRMs) have received extensive attentions in recent years due to their high torque densities, robust structures, fast transient responses, etc. This paper focuses on the analysis of the torque performances including average torque, cogging torque, and ripple torque of three-phase FRMs. First, the general expressions of instantaneous torque under no-load and rated-load conditions are analytically derived. Then, based on the analytical equations, the effects of rotor slot number, split ratio, permanent magnet thickness, and stator and rotor slot opening ratio on the torque performances are investigated and analyzed, which can be used for optimizing the structural parameters for maximum torque density and minimum pulsating torque. Finally, the theoretical analyses are validated by experiments on a 12-stator-slot/17-rotor-slot FRM prototype. Good agreements have been achieved between the simulated and experimental results.

Electromagnetic evaluation of an in-wheel double rotor axial-flux switched reluctance motor for electric traction

In this paper, a novel in-wheel double rotor axialflux switched reluctance motor for electric traction is presented. The proposed double rotor axial-flux switched reluctance motor has a particular disposition of the stator and rotor poles that provides short flux path without flux reversal. The ferromagnetic pieces of the stator and the rotor are built using soft magnetic composites. Electromagnetic analysis is performed using three dimensional finite element analyses, 3D FEA. Matlab-Simulink simulation coupled with the results of finite element analysis proves that the proposed motor drive is suitable for the propulsion of a given E-scooter.

Small Scale Wind Generation System: Part II – A Novel Quasi-Z-Source Inverter and FRG-QZSI-Micro Grid Interface

<p>This paper proposes modelling, analysis and control of a small scale wind energy conversion system employing a direct driven Flux Reversal Generator (FRG) connected to the micro grid through a quasi-Z-source inverter (QZSI). This entire research is made up of two major parts viz., FRG and QZSI. In the part I report of this research work, the role of FRG has been thoroughly modelled and verified. In this part II, the modelling and analysis of QZSI for this purpose is presented. In addition, the modified space vector PWM (SVPWM) technique is proposed in this paper to satisfy the shoot-through characteristic of QZSI, which is a novel. The interface of FRG and QZSI to inject power in to micro grid has been finally presented. The simulation results are validated with the analytical results. Section I discusses the open loop control of QZSI. The mathematical modelling of QZSI for this purpose is given and analytically validated. This flowed by section II in which the proposed SVPWM is presented. The procedure to obtain triggering pulses using this proposed modulation technique is discussed. Section III presents closed loop control strategies for QZSI. Section IV presents the micro grid<br />inte face and power injection.</p>

Small Scale Wind Generation System: Part I – Experimental Verification Of Flux Reversal Generator Block

<p>This research work, titled Small Scale Wind Generation System, reported in part I and part II, proposes modeling, analysis and control of a small scale wind energy conversion system employing a direct driven Flux Reversal Generator (FRG) connected to the micro grid through a Quasi-Z-Source Inverter (QZSI). The application of QZSI using FRG to feed micro grid is proposed for the first time in this research work. The QZSI can realize buck/boost, inversion and power conditioning in a single stage with improved reliability. Also it features a wide range of voltage gain which is suitable for applications in wind systems, due to the fact that the wind generator output varies widely with wind velocity. In addition, the modified Space Vector PWM (SVPWM) technique is proposed in this paper to satisfy the shoot-through characteristic of QZSI. This also adds to the contribution of this research work. In this part I of this full research, modelling of the small scale FRG for wind system using Finite Element Analysis (FEA) is presented. The major parameter of FRG viz, voltage, current, torque and power are analyzed, validated and then represented in d-q model. The simulation results are validated with the analytical results. An experimental set-up to run the full procedure reported in this paper. These results form the basis for part II of this research work.</p>