Effect Of Magnetic Field Modulation Research Articles

A Magnetic-Geared Machine With Improved Magnetic Circuit Symmetry for Hybrid Electric Vehicle Applications

Magnetic-geared machine (MGM) has been widely investigated as the power split device for hybrid electric vehicles with the inherently high-integration of multi-mechanical ports. It is revealed that the magnetic circuits of armature winding in MGM are essentially asymmetrical for different phases under the magnetic field modulation effect. This inevitably results in unbalanced phase back electromotive force (EMF) waveforms, severe torque ripples, acoustic noise, and difficulty for precise control. To alleviate the asymmetry problem, a generic winding design model is presented for MGMs in this paper, which allows for consideration of all potential winding configurations. Firstly, a novel back EMF harmonic factor is proposed to account for both the harmonic content and asymmetric level in MGM. The genetic algorithm (GA) is further employed to optimize the winding in terms of minimizing the back EMF harmonic factor, armature magnetomotive force harmonic contents, and phase winding resistance. The proposed winding layout exhibits superior filtering capability for three-phase asymmetric magnetic field harmonics. As compared with the conventional integral-slot distributed winding, the MGM with the proposed winding exhibits improved back EMF waveform symmetry, suppressed torque ripple, and reduced core losses. Finally, an experimental prototype is manufactured to validate the effectiveness of asymmetric magnetic field suppression for MGMs. The results show the investigated winding design method is an effective solution to the asymmetric issue of MGMs, paving the way to research opportunities for further improvements.

Magnetic field modulation effect on photoelectric effect and its explanation in BiFe0.9Ni0.1O3/n-Si multiferroic heterojunction

This paper reports a heterojunction laminate consisting of Ni doped BiFeO3 thin film and n-type single crystal silicon semiconductor, in which the repeatable modulation effect on the photoelectric properties were achieved by applying external magnetic fields. More obviously, the response of photocurrent and photovoltage to the magnetic field is perfectly linear. This functional effect of sensing is mainly related to the guidance of the magnetic field to the photogenerated carrier transfer process in the heterojunction. The linear relationships between magnetic field and photocurrent, magnetic field and photovoltage have been proved through the derivation of the formulas. The heterojunction perfectly combines the functions of the sensor and the controller to reflect both the intensity of the magnetic field and the intensity of the light in the environment. This work provides an alternative and facile way to realize the multi-degree of freedom control for electrical signal and practicability of multifunctional devices.

High Torque Density and Lightweight Design of Permanent Magnet In-Wheel Motor Based on Magnetic Field Modulation Effect

High Torque Density and Lightweight Design of Permanent Magnet In-Wheel Motor Based on Magnetic Field Modulation Effect

Magnetic field modulation effect of photoelectric properties in dye-sensitized solar cells with La0.67(Ca,Ba)0.33MnO3 as counter electrodes.

In recent years, many semiconductor materials with unique band structures have been used as Pt counter electrode (CE) substitutes for dye-sensitized solar cells (DSSCs), which makes the photoelectric properties of DSSCs possible to be modulated by electric field, magnetic field, and light field. In this work, La0.67(Ca Ba)0.33MnO3 (LCBMO) thin film is employed to act as CE in DSSCs. The experimental results indicate that short-circuit current density and photoelectric conversion efficiency present better stability when applying an external magnetic field to the DSSCs. Furthermore, both the exchange current density (J0) and limit diffusion current density (Jlim) are largely enhanced by an external magnetic field. J0 increases from -0.51 mA•cm-2 to -0.65 mA•cm-2, and Jlim increases from 0.2 mA•cm-2 to 0.3 mA•cm-2 when applying a magnetic field of 0.25 T. The fitting results of the impedance test verify that the magnetic field reduces the value of Rct. Both magnetic-field enhancing catalytic activity and CMR effect jointly promote the increase of photocurrent and finally improve the photovoltaic effect in DSSCs.

Analysis of Split-Tooth Stator PM Vernier Machines With Zero-Sequence Current Excitation

This article proposes a series of split-tooth stator permanent magnet (PM) Vernier machines with zero-sequence current excitation, which integrates enhanced torque density and flux adjustment capability. The key is to design the split tooth to exert desired dual magnetic field modulation effect so as to efficiently utilize the hybrid magnetic fields by the PM and zero-sequence current. Meanwhile, with the split-tooth design, the paralleled flux paths are achieved to offer improved flux regulation capability and reduced PM demagnetization risk. In this article, the machine topologies and operation principle are introduced. Hybrid excitation magnetic field is analyzed with the consideration of dual magnetic field modulation of split-tooth structure. Influences of split tooth and PM on torque and flux regulation capability are analyzed. Electromagnetic performances of the proposed machine are analyzed and compared. A prototype is manufactured and tested to validate the theoretical analysis.

Effect of magnetic field modulation on Bénard–Taylor ferroconvection

Effect of magnetic field modulation on Bénard–Taylor ferroconvection

Modulated Vibration Reduction Design for Integral-Slot Interior Permanent Magnet Synchronous Machines

In this article, a targeted step skewing of rotor segments scheme is proposed to reveal the modulated vibration reduction mechanism in integral-slot interior permanent magnet synchronous machines (IPMSMs). First, the vibration characteristics of a 72-slot/12-pole integral-slot IPMSM are investigated. The dominant vibration at specific frequency band is introduced. Then, in order to analyze the main source of vibration, the magnetic field modulation effect and radial force modulation effect are investigated in detail. The results show that the high-order radial force can excite large vibration by radial force modulation effect. This kind of vibration is defined as modulated vibration. Afterwards, the optimal shift angle and number of rotor segments are determined by comparison. Finally, the conventional and proposed 72-slot/12-pole integral-slot IPMSMs are manufactured to validate the theoretical analysis. The experimental results verify that the proposed method can effectively reduce the modulated vibration of the 72-slot/12-pole integral-slot IPMSM.

Dynamic Analysis of Surface-Mounted Permanent Magnet Type Coaxial Magnetic Gear With Damper Bar Considering Magnetic Field Modulation Effect

Coaxial Magnetic Gear (CMG) has unstable dynamic characteristics by hunting or pull-out action of the output rotor when the load or speed are changed, unlike traditional mechanical gears. These dynamic characteristics need to be improved in order to secure the reliability of mechanical power transmission system by fast and accurate response. In this paper, the damper bar used in synchronous machines is considered as a method to improve the dynamic characteristics of CMG. The Surface-mounted Permanent Magnet (SPM) type CMG is selected as the analysis model. The space harmonics of the magnetic flux density of stationary and rotary members of CMG namely, modulating pieces, inner and outer rotor, are analyzed and characterized the influence of them on the improvement of dynamic characteristics as well as torque reduction. Also, the magnetic flux density characteristics and the damping effect are compared according to the position of the damper bars on two rotors and the modulating pieces. In conclusion, the considerations about the perspective for design and application are presented when using the damper bar for SPM type CMG.

Magnetic field analysis of Primary Permanent Magnet Linear Motor Based on Halbach Distribution

The rail transit system driven by linear motor has outstanding advantages in climbing ability, traction performance, vibration and noise. However, with the increase of traffic travel and other situations, how to ensure that the linear motor still has a large thrust and stability in the air gap condition is the key technical problem. In order to solve this problem, three Halbach permanent magnet array structures are proposed and applied to the magnetic barrier coupled primary permanent magnet unilateral excitation linear motor (MBCPPMUELM). The finite element software is used for simulation and analysis. By comparing the harmonic distribution of air gap magnetic field of the three Halbach permanent magnet array motors, a topology structure with high magnetic field modulation effect is obtained It provides a useful reference for the further design and analysis of this kind of motor.

A Generalized Equivalent Magnetic Network Modeling Method for Vehicular Dual-Permanent-Magnet Vernier Machines

This paper proposes a new equivalent magnetic network (EMN) model for vehicular dual-permanent-magnet vernier (DPMV) machines by applying a generalized modeling method. First, the magnetic circuit method and the meshing method are combined together to improve the modeling efficiency of the DPMV machine. The magnetic circuit method is used to generate conventional lumped parameter permeances to shorten time consumption, whereas the mesh method is utilized in disordered magnetic fields to obtain high precision. Second, a meshing solution for oblique region is proposed to enhance modeling flexibility. Moreover, the flux distributions in meshes are represented without magnetic field pre-delineation, which enables its utilization as a self-adaptive reluctance network model in design optimization. Finally, the proposed EMN model is used to predict the performance of the DPMV machine, considering leakage magnetic flux, local iron saturation, and magnetic field modulation effect simultaneously. Meanwhile, the effectiveness of the proposed EMN model is verified by comparison with finite-element analysis and experimental tests.

Magnetic gear with intersecting axes and straight stationary pole-pieces

Based on the magnetic field modulation effect, this article presents a magnetic gear with intersecting axes and straight stationary pole-pieces. Except for a higher utilization of permanent magnets and a greater output torque, the magnetic gear with intersecting axes and straight stationary pole-pieces provides several advantages, such as a smaller volume, higher torque density, and lower processing cost. The magnetic gear with intersecting axes and straight stationary pole-piece topology is herein introduced and the deduced constraints of the structural design are outlined. The transmission mechanism is demonstrated by analyzing the output torque in the middle of the air gaps. The effects of the main design parameters on the maximum static torque are evaluated using the finite element method. Based on the orthogonal experimental design and the response surface method, the optimum design results are provided. Prototype of the magnetic gear with intersecting axes and straight stationary pole-pieces has been realized and the static torque has been verified experimentally.

A New Magnetic Field Modulation Type of Brushless Double-Fed Machine

In this paper, a new magnetic field modulation type of brushless double-fed (MFM-BDF) machine is proposed, in which a split-pole structure inner stator with three modulating poles on each stator tooth and an outer rotor with surface-mounted permanent magnets are adopted. By employing a set of 3-phase armature winding and a set of 3-phase field winding wound around stator teeth and modulating poles, respectively, the hybrid excitation operation can be achieved. The proposed machine can achieve not only a high torque density due to the magnetic field modulation effect, but also an wide operation region and an almost unchanged cogging torque peak-to-peak value by feeding flux-weakening and flux-enhancing currents into the field windings, respectively. The configuration of proposed machine and the basic principle are introduced first. Then by using 2-dimension finite element analysis, the basic characteristics, such as no-load flux linkage, cogging torque and no-load EMF are analyzed.

A New Method to Estimate the Magnetic Field Modulation Effect of Brushless Doubly-Fed Machine with Cage Rotor

Brushless doubly-fed machine (BDFM) doesn't use brush and slip ring, and has advantages such as high system reliability, small capacity of its frequency converter, low system cost, adjustable power factor and speed, etc. At the same time, it has good applicable potentials on the variable frequency motors and the variable speed constant frequency generators. However, due to the complicacy and particularity of BDFM in the structure and operating mechanism, the effect of magnetic field modulation directly influences the operating efficiency of BDFM. To study the effect of different cage rotor structures on the magnetic field modulation of BDFM, the rotor magnetomotive force (MMF) of BDFM with cage rotor is studied by the analytical method. The components and features of rotor harmonic MMFs are discussed. At the same time, the method to weaken the higher harmonics is analyzed by the theoretic formulae. Furthermore, the magnetic field modulation mechanism is expounded on in detail and the relationship between the magnetic field modulation effect and the operating efficiency of BDFM is established. And then, a new method for estimating the magnetic field modulation effect is proposed. At last, the magnetic field modulation effects of four BDFM prototypes with different cage rotor structures are compared by the MMF analysis and the efficiency data of electromagnetic design. The results verify the effectiveness of the new method for estimating the magnetic field modulation effect of BDFM with cage rotor.

Magnetic-modulation spectroscopy of an atomic Fermi gas in the BCS-BEC crossover: Dissociation spectra in the Bose-Einstein condensate regime

The effect of magnetic-field modulation on a Fermi gas of atoms in the BCS-BEC crossover is studied analytically. Recent experimental findings on the system response to a sinusoidal variation of the field are explained. Specifically, the dissociation processes induced by the modulation in the Bose-Einstein condensate regime are described. The role played by the frequency, amplitude, and application time of the perturbation in the emergence of the observed behavior is clarified. The results uncover also the relevance of the detuning from the Feshbach resonance to the appearance of particular spectral features. The applicability of the field modulation as a spectroscopic tool for probing the crossover is discussed.

The effect of magnetic field modulation on the microwave response in high-Tc superconductors

The origin of the strong enhancements of microwave response at the onset of the superconductivity has been investigated. Since the effect is only detectable when the measurements are made by making use of a ESR spectrometer, the effect of modulation is investigated. The origin of the enhancement is considered to be due to strong dependence of the microwave dissipation on the magnetic field.

Detection of weak link superconductivity by magnetically modulated electrical resistance

Abstract A new technique, based on observing the effect of magnetic field modulation on the DC resistance of superconductors, sensitively detects the presence of weak links in granular high temperature superconductors. The phase detected response to the magnetic modulation shows a peak at T c for both metallic and ceramic superconductors, analogous to that observed in magnetically modulated microwave absorption. A second peak, attributed to weak links, is observed below T c in the ceramic oxide superconductors when tailing is present in the resistance vs. temperature curve.

DETECTION OF SUPERCONDUCTING TRANSITIONS BY MAGNETICALLY MODULATED ELECTRICAL RESISTANCE

A new technique for detecting superconductivity, based on observing the effect of magnetic field modulation on the dc resistance of superconductors, is presented. The phase detected response to the magnetic modulation shows a peak at Tc for both metallic and ceramic superconductors, analogous to that observed in magnetically modulated microwave absorption. The results further demonstrate that the magnetically modulated microwave absorption peak at Tc is not equivalent to the non-resonant low field microwave absorption observed in the ceramic superconductors.

Modulation Effects in Nuclear Magnetic Resonance

The perturbing effect of magnetic field modulation in nuclear magnetic resonance under conditions of high resolution is discussed. When the modulation frequency is greater than the resonance line width, sideband resonances separated in frequency by the modulation frequency are observed, having line shapes of either absorptive or dispersive form or a mixture of the two depending on the phasing of the lock-in detector. The form and distribution of these sidebands is satisfactorily accounted for using Bloch's equations.