Magnetic Thickness Research Articles

Magnetic Control of Vibrational Behavior of Smart FG Sandwich Plates with Honeycomb Core via a Quasi‐3D Plate Theory

Herein, vibrational behavior of functionally graded (FG) smart piezoelectric sandwich plates with honeycomb core resting on viscoelastic foundation under the effect of 2D magnetic field is presented. By varying the magnetic‐field magnitude and its direction, the vibrations can be controlled. The plate is composed of two FG piezoelectric layers bonded with honeycomb structure as a mid‐layer. Magnetic Lorentz force will be deduced via Maxwell's relations. A new quasi‐3D plate theory considering the shear and normal deformations is incorporated to evaluate the displacements. The governing equations of motion are introduced via Hamilton's principle. Galerkin technique is considered to solve the motion equations for different boundary conditions. Influences of the magnetic field, boundary conditions, electric voltage, and core thickness on the eigenfrequency of the FG sandwich piezoelectric plate are illustrated. It is found that considering the effect of the magnetic field on the smart devices increases their vibrations, which may lead to an increment in the energy harvested from them. Further, when the magnetic field is applied along the length of the rectangular plate, the vibrations are reduced and vice versa.

Performance analysis of various rotor topologies of surface PM synchronous motor

Abstract Surface mounted permanent magnet synchronous motors can be found in several designs regarding configuration of magnets on the rotor. Finding the most optimal design in terms of the high efficiency and power factor, small cogging torque and material consumption along with good overloading capability could be a challenging task. This paper analyzes three different rotor designs of surface permanent magnet motors regarding their magnet shapes. All three motors have the same outer dimensions, output power, torque and the material properties. The comparison of all three models is performed and advantages and drawbacks of each model are pointed out. Four design variables are selected to be varied within prescribed limits for each motor model in order the best combination of number of conductors per slot, magnet thickness, the magnet length and shape to be fond, which result with the highest efficiency, small cogging torque and good overloading capability of the motor. The impact of each varied parameter on motor efficiency and cogging torque is presented. All three optimized model are compared and the most optimal model in terms of the above-mentioned characteristics is analyzed by finite element method (FEM) and with the Simulink. The model in Simulink allows motor transient characteristics to be obtained. The performed analysis is useful for determining the most optimal and cost-effective solution among presented three types of surface mounted permanent magnet motors in terms of the high efficiency and power factor, small cogging torque and material consumption.

The development of a high-efficiency aquaculture water pump using self-adhesive electrical steel

Traditional water pump use AC motor combines with gearbox to achieve high torque and low speed to protect fish form injury by blades, which will shorten the life of waterwheel. Besides, the efficiency of the gearbox is about 40 ∼ 50%, resulting in low efficiency of whole system, and translated into poor reliability. The waterwheel in this study uses surface permanent magnet (SPM) motor instead of AC motor. However, the design of conventional waterwheel PM motor has the following drawbacks: (a) the slot fill factor cannot be too low; (b) the spacing between the rotor magnet grooves is too large, which affect the efficiency of the motor. To improve the motor efficiency without changing the shape of the stator core, this study developed an assembled stator core to improve the slot fill rate of motor winding. However, if the stack length of the stator core is too high, there will be a problem of core breakage. Therefore, this study introduced the self-adhesive steel to develop a self-adhesive assembled stator core to improve the breakage situation, and also to take advantage of the higher slot fill rate of the assembled core. Furthermore, in order to solve the problem of large spacing between the rotor magnet grooves, we optimize the magnetic circuit design by using simulation to improve the motor performance, such as magnet size, slot opening size, etc, to make the back electromotive force waveform as a sine wave. In addition, this design also reduces the thickness of magnets to reduce the cogging torque of the motor, and effectively reduces magnet usage to reduce the cost. As a result, this study developed a high-efficiency waterwheel SPM motor about 86.32% at 123 rpm, by using self-adhesive assembled stator core to increase the slot fill factor. The overall efficiency of system reaches about 78.72%.

Thickness dependence of magnetic properties of Ir/FeV-based systems

Ir-buffered ${\mathrm{Fe}}_{0.7}{\mathrm{V}}_{0.3}$ (FeV) thin films of variable thickness ($1.4\phantom{\rule{0.28em}{0ex}}\mathrm{nm}\ensuremath{\le}{t}_{\mathrm{FeV}}\ensuremath{\le}10\phantom{\rule{0.28em}{0ex}}\mathrm{nm}$) were sputtered on thermally oxidized Si substrate and capped with Cu or MgO films. Vibrating sample magnetometery measurements allowed deducing their magnetization at saturation and the magnetic dead layer thickness, found to be capping layer independent. Microstrip line ferromagnetic resonance measurements under in-plane and perpendicular to the film plane applied magnetic fields are employed to investigate the perpendicular magnetic anisotropy (PMA) and damping. PMA is found to result from a uniaxial interfacial contribution which is slightly capping layer dependent. In contrast, the second-order PMA constant, which could result from the inhomogeneous distribution and the spatial fluctuations at the nanoscale of the uniaxial PMA at interface, is significantly stronger for Ir/FeV/Cu films. The damping dependence on the inverse of FeV effective thickness revealed a low Gilbert damping constant for FeV $({\ensuremath{\alpha}}_{\mathrm{FeV}}=1.7\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}3})$ and allowed concluding that damping enhancement is mainly induced by Ir/FeV. The zero frequency linewidth for in-plane configuration is attributed to two magnon scattering contribution, found to be higher for Cu capped FeV. The investigation of the FeV thickness dependence of interfacial Dzyaloshinskii-Moriya interaction (iDMI) of both systems via Brillouin light scattering allowed to conclude to the zero iDMI constant of FeV/Cu. It also led to deduce iDMI constants of Ir/FeV and FeV/MgO, estimated to be ${D}_{\mathrm{s}}^{\mathrm{Ir}/\mathrm{FeV}}=(0.13\ifmmode\pm\else\textpm\fi{}0.02)\phantom{\rule{0.28em}{0ex}}\mathrm{pJ}/\mathrm{m}$ et ${D}_{s}^{\mathrm{FeV}/\mathrm{MgO}}=(\ensuremath{-}0.07\ifmmode\pm\else\textpm\fi{}0.02)\phantom{\rule{0.28em}{0ex}}\mathrm{pJ}/\mathrm{m}$, respectively.

Magnetic-Solid Coupling Nonlinear Vibration of an Axially Moving Thin Plate Under Air-Gap Magnetic Field

The nonlinear inherent vibration of an axially moving ferromagnetic thin plate under the action of the armature air-gap magnetic field is investigated. Based on the nonlinear elasticity theory, the energy relationship equations of the thin plate are given. Based on the electromagnetic theory and the solution of Laplace’s magnetic potential equation, magnetic force on the ferromagnetic rectangular plate under air-gap magnetic field environment is deduced. The Hamilton variational principle is applied to derive the magneto-solid coupled nonlinear vibration equation of the axially moving ferromagnetic thin plate. The two-degree-of-freedom nonlinear vibration differential equations containing static load terms with boundary conditions of SSSS and SSCC are obtained by discretizing through the Galerkin method. The multi-scale method is applied to solve the second-order approximation for deriving the first two orders’ intrinsic frequency of the nonlinear system. The variation laws of first two orders’ nonlinear inherent vibration with axial velocity, magnetic potential, initial air-gap thickness, and initial value are given through numerical examples, and the comparative analysis is performed. The results show that the first-order and second-order inherent vibration frequencies decrease with the increase of axial velocity and magnetic potential and increase with the increase of initial air-gap magnetic field thickness. Different materials and different boundary conditions have greater influence on the first-order and second-order inherent frequencies, and show obvious nonlinear characteristics. The results can provide references for analyzing and controlling the vibration behavior of moving structures in electromagnetic environment.

Torque analysis and stator windings influence research on negative-salient permanent magnet synchronous motor

Compared with the traditional motor, the negative-salient permanent magnet synchronous motor (NSPMSM) has the characteristics of wide-speed range, strong overload capacity and uneasily demagnetized permanent magnet. In this paper, a new rotor structure of NSPMSM is proposed by using magnetic bridge to increase the d-axis inductance (Ld) and W-type permanent magnet to decrease the q-axis inductance (Lq). Firstly, the electromagnetic torque performance of NSPMSM was analyzed from the parameters of permanent magnet (PM) thickness, magnetic bridge length, eccentricity distance and air-gap length using finite element method. At the same time, the electromagnetic torque ripple and cogging torque of the NSPMSM are further analyzed, which provides an effective basis for evaluating the optimal performance of the NSPMSM. Secondly, the effects of different stator slots and different winding layers on the air-gap magnetic flux density, electromagnetic torque, power and eddy current loss of PM of the NSPMSM were analyzed by finite element method under the condition of same rotor. The advantages and disadvantages of different windings are summarized, and the constant-power speed range of the NSPMSM is calculated, which provides the basis for the study of the flux weakening properties of the new motor. The results of theoretical analysis agree with those of simulation analysis, which verifies the effectiveness and feasibility of the new motor.

Structure Design of Multi-DOF Motor with Stator Permanent Magnet based on Flux Switching

This paper aims at the problems of no core in the stator coil of a compact multi-degree-of-freedom (M-DOF) motor, i.e., small output torque and low power density. In order to increase the output torque, a stator permanent magnet spherical motor based on flux switching is proposed. Firstly, the principle of flux switching is introduced. The basic structure of the new motor is preliminarily designed, and the motion mechanism is analysed for spin motion and tilt motion respectively. Then the minimum model of a novel motor is established in ANSYS by using the virtual displacement method. The key parameters such as the ratio of stator pole tooth to permanent magnet size, different stator pole tooth end structures, different pole tooth surface shapes, different pole sizes, permanent magnet thickness, different magnetisation methods and different ampere-turn numbers are optimised within a reasonable parameter range. The simulation results are analysed and discussed, and the optimal results for each key parameter are thus given. Finally, considering the arrangement of the stator and rotor poles, the rationality of the three-DOF motion was verified by means of two energising strategies, spin motion and tilt motion, verified the reasonableness of the above optimal parameters and thus determined the structural parameters of the new spherical motor to accomplish the three-DOF motion and the maximum torque range. The simulation results show that the electromagnetic torque varies approximately linearly over a range of ampere-turns for the same position of the rotor pole teeth. It provides an opportunity for the M-DOF motor design of a high torque output and power density.

Structural design and experimental study of multi-ring and multi-disc magnetorheological valve

In order to solve the problems of small pressure drop range and achieve lower response time and small power consumption of traditional control valves in automotive hydraulic lift, the magnetic circuit method was employed to design a new multi-ring and multi-disc magnetorheological valve based on magnetorheological fluid and its pressure drop mathematical model was established. Through the electromagnetic field simulation, the effect of current size, radial damping gap size, axial damping gap size and magnetic isolation thickness affect the performance of the multi-ring and multi-disc magnetorheological valve is studied. The pressure drop characteristics and response time of the multi-ring and multi-disc MR valve under different currents, different direction of loading current and different loads have been studied experimentally. The results show that the saturation pressure drop of the multi-ring and multi-disc MR valve is greater than 7 MPa, and the response time is 136 ms–178 ms, which proves the performance advantage of the multi-ring and multi-disc MR valve.

Effect of magnetic field on electroconvection in a thin layer of magnetic nanofluid

It is shown that the external magnetic field (of the strength < 10 kA/m) parallel to the electric field (DC and AC) reduces the electroconvection development threshold voltage and the time of electroconvection development (up to 50 %), and creates a more branched pattern of electroconvective flows in a layer of magnetic nanofluid. The magnetic field perpendicular to the electric field increases the electroconvection development threshold (up to 15 %) and leads to electroconvective pattern degeneracy into a system of strips parallel to the magnetic field. It is demonstrated that the critical voltage increases with increasing magnetic nanofluid layer thickness and voltage frequency.

Multi-objective optimization of the hollow shaft direct drive motor

Surface permanent magnet synchronous motor (SPMSM) is widely used in low-speed and high torque permanent magnet synchronous motor. A multi-objective optimization method of hollow shaft direct drive motor (HSDDM) for double direct drive feed system (DDFS) is proposed in this paper. Several dimensions of HSDDM are considered in the proposed design procedure including pole embrace, thickness of magnet, eccentric distance, and air gap length. A multi-objective optimization model is established to minimize cogging torque, maximize efficiency, and minimize the magnet weight. The Optimized Latin hypercube sampling (OLHS) is used to design the experimental samples, and the sampling results are calculated by the finite element method (FEM). The Kring approximate model is established according to the sampling results. Based on the established approximate model, NSGA II multi-objective genetic algorithm is used to optimize the HSDDM. Compared with that before optimization, the efficiency after optimization is increased by 4.08%, the cogging torque is reduced by 86.78%, and the magnet weight is reduced by 20.24%. Eventually, the integration of NSGA-II and FEM provides an effective approach to obtain the optimal design of HSDDM.

On the determination and interpretation of the lithospheric induced magnetisation

We present a new technique for reducing the uncertainties inherent in the interpretation of lithospheric magnetic field observations over the Earth. This technique, without involving iterations, provides an improved estimate of the depth-integrated magnetic susceptibility of the crust as compared to previous approaches. Departing from the normal practice of using observations at specific locations, we model directly Gauss coefficients of the lithospheric magnetic field and use an a-priori initial lithospheric thickness model to circumvent magnetic annihilators (i.e. magnetisation distributions that cannot be determined from magnetic data since they have no impact on the lithospheric magnetic field). Of the several initial magnetic layer models tested, we prefer the model where magnetic thickness is based on the Moho or the regional estimate of the Curie depth when it is shallower than the Moho because it is physically reasonable and produces the fewest artefacts. The method is applied to a recent high-degree lithospheric magnetic field model called LCS-1 derived from CHAMP and Swarm magnetic satellite data. The technique is appropriate for regions where induced magnetisation dominates over remanent magnetisation. We show that high degrees of the final depth-integrated magnetic susceptibility variation are dependent only on the corresponding high degrees of the LCS-1 magnetic field model. Thus, the depth-integrated magnetic susceptibility variation is an important quantity derived in the study which enables readily qualitative interpretation of regional geology.

The investigation of linear relationship between domain wall creep parameters in Co/Pt multilayers

In this work, we investigate the linear relationship between domain wall creep parameters, and evaluate the effect of material parameters on magnetic domain wall creep in a series of Pt/Co/Pt multilayers with perpendicular magnetic anisotropy. The results for the samples with different magnetic layer thicknesses verify the linear relationship between the domain wall creep parameters, which is because in these samples both domain wall creep parameters are mainly affected by Co layer thickness and both of the domain wall creep parameters are proportional to the Co layer thickness. With the assistance of surface acoustic waves, the domain wall creep parameters also follow the linear relationship. This suggests a relationship between the anisotropy density K and local pinning strength The above linear relationship does not exist in annealed samples because annealing breaks the relationship between the local pinning strength and material parameters.

Key Parameters Design of Robot Joint Motor Based on Frozen Permeability

Robot joint motors have the characteristics of high torque density, low torque fluctuation, short-term high-overload, and light weight. Conventional design methods only focus on the overload capacity, without precisely analyzing the stator-rotor parameters and the effect of magnetic saturation on load torque fluctuation. Combining with the frozen permeability technology, the effects of structural parameters such as tooth width, slot opening, permanent magnet thickness and pole arc coefficient on the fluctuating component of load torque and ultimate torque are studied. Then, based on the performance requirements of joint motors for quadruped robots, a compact design joint motor for robots was designed to achieve a maximum torque overload capacity of 7.33 times and low torque fluctuation. A design method for a high-overload, low torque fluctuation robot joint motor was obtained, and finally the effectiveness of the proposed method was verified by prototype experiments.

Magnetic properties of (Ni0.81Fe0.19/SiO2)n multilayers for high frequency on-wafer inductor applications

We investigated the magnetic properties of multilayer stacks of Ni81Fe19 thin films separated with SiO2 intended for use in inductors operating at sub-GHz frequencies. We measured saturation magnetization, anisotropy field, coercivity, and complex permeability of sputtered multilayer structures consisting of thin film stacks of 5, 10, 15, 20, and 25 layers, ranging from 160 to 1455 nm in total magnetic material thickness. Our analysis indicates that multilayer stacks composed of repeated layers thinner than 115 nm generally maintained the desired magnetic properties found in individual thin films, such as high permeability, low anisotropy, and low coercive field. Moreover, the multilayer stacks did not exhibit unwanted characteristics such as stripe domain formation and decreased value of real permeability, which commonly occurred in single thicker films. These properties make them suitable for on-wafer inductor applications.

Simulation and Experiment of Electromagnet for High-Speed On-off Valve for Vehicle Shifting System

The high-speed on-off valve is the core component for adjusting the oil pressure of the pressure reducing valve in the clutch shifting system of engineering vehicles, and its response speed is one of the important indicators to measure its performance. In order to improve the dynamic performance of high-speed on-off valve, the electromagnet with solid magnetic isolation structure was designed and simulated by considering the eddy current loss factor. A high-speed on-off valve electromagnetic actuator with high response speed was obtained. Firstly, the theoretical calculation and verification of the theory were carried out by using the electromagnet design theory, and the theoretical model of the electromagnet was built. Secondly, the electromagnet parameter model was brought into the finite element simulation software ANSYS Electronics to simulate and optimize the static magnetic field and the transient magnetic field respectively. The different structural parameters (guide bush thickness, outer magnetic pole thickness, magnetic isolation structure, armature length) were analyzed. And the effect of the coil parameters (number of strands) on the steady-state electromagnetic force and the dynamic displacement of the armature was analyzed. The values of the structural parameters of the electromagnet were subsequently determined. Finally, the static and dynamic characteristics experiment of the magnetically separated solid electromagnet is designed and processed. The experiment and simulation results are in good agreement. The feasibility of the high-resistance electromagnet structure design and the correctness of the simulation are verified. Reasonable optimization of structural parameters and coil parameters has obvious significance for improving the dynamic characteristics of high-speed on-off valve electromagnets.

Finite Element Simulation Calculation and Optimal Design of Permanent Magnet Synchronous Motor

In order to promote the development of green energy applications, this paper selects a 4-pole 24-slot surface-mounted permanent magnet synchronous motor and performs finite element simulation and optimization design on it. Firstly, finite element analysis is carried out, and the performance of the motor is verified by finite element simulation. Then, the parameterized simulation and sensitivity analysis of cogging torque and three-phase current are performed by selecting the variables of permanent magnet thickness, stator inner diameter, slot width, and air gap. Finally, simulation experiments provide optimization for each variable for the motor.

FEA Based Design of Outer Rotor BLDC Motor for Battery Electric Vehicle

Due to enormous advantages, BLDC motors have been identified for the design in various applications. With its good power density, this motor is being used by the automobile industry. The paper aims to design the motor for the battery electric vehicle. The major challenge of the BLDC motor is to reduce torque ripples which appear because of high cogging torque. Torque ripple results in acoustic noise and vibrations in the battery electric vehicle which badly affects the performance of the vehicle. The cogging torque and efficiency are characterized by a parametric technique with varying pole embrace factor and magnetic thickness. The selection of optimum values of rotor pole embrace factor and magnetic thickness has a significant role in the reduction of cogging torque. The Ansys Maxwell tool helps in the optimum designing of the motor by mitigating the torque ripples and thus increasing the average torque. The proposed model has 5.7% better efficiency in comparison to the base model and has a small number of torque ripples.

Multi Objective Optimization of Permanent Magnet Synchronous Motor Based on Taguchi Method and PSO Algorithm

To solve the optimization issues of interior permanent magnet synchronous motors (IPMSMs) and ensure a large output torque while minimizing torque ripple and core loss, the multi-objective optimization strategy should be employed. In this study, we took an 8-pole, 48-slot IPMSM as a specimen. First, the width and thickness of the permanent magnet (PM) and the rotor bridge structures were pre-selected as optimization parameters, while torque ripple and core loss were taken as optimization targets. Then, the Taguchi method to perform orthogonal experiments was employed to select the multi-parameter combinations that make the experimental results stable and with little fluctuation. To ensure the optimal results, the function equations were obtained by multivariate nonlinear fitting, while the parameters were optimized by particle swarm optimization (PSO). Finally, the optimal results were verified by the Finite Element Method (FEM). The results show that our proposed hybrid method can provide an optimal design strategy with better performance such as smaller torque ripple and core loss while maintaining a larger output torque.

Vibration control of flexible rotors using a passive magnetic device working on the principle of electromagnetic shunt damping

Excessive rotor vibration can propagate the micro-cracks and hence the premature failure of the rotor system. A passive magnetic device working on the principle of electromagnetic shunt damping (EMSD) is proposed to passively control the rotor vibrations. Although, these EMSD-based damping systems are quite common in the literature, however, there is not even a single article available in the literature, showing the application of such a device passively controlling the rotor vibrations from a distance. Due to the flow of flux between the rotor, stator, and air gap, the modeling procedure for such an EMSD-based system changes completely and is not available in the literature. Due to rotor movement, there is a variation in the magnetic flux provided by the permanent magnets placed in the device. Due to electromagnetic interactions, electric currents are induced in the windings provided in the device. When these currents are allowed to pass through electrical resistance, damping forces are generated. In this way, vibration energy is converted into heat energy. In this research, it is observed that the damping effect is maximum for an optimal value of electrical resistance. The effect of several turns in the windings and permanent magnet thickness is also investigated in terms of the production of damping forces. The efficiency of the device is mathematically proved through simulations. Further, experimental results verify the effectiveness of the proposed device.

The Absorption Properties of One‐Dimensional Spherical Photonic Crystals Based on Magnetized Ferrite Materials

AbstractBased on a spherical coordinate system and Maxwell's set of equations, the calculation formulas of one‐dimensional (1‐D) magnetized ferrite spherical photonic crystals (MFSPCs) are obtained and treated with the solution method of the spherical Bessel equations. Combined with the conventional transmission matrix method, expressions for the absorptance, reflectance, and transmittance of the 1‐D MFSPCs are given. 1‐D MFSPCs consisting of the general dielectric and Yttrium iron garnet (YIG) are also designed to verify the correctness of the conclusions. Variables such as external magnetic field, incidence angle, initial radius, and YIG thickness effects on the features of such 1‐D MFSPCs are also discussed. The transformation of the external magnetic field has a linear relationship with the position of the absorption band (AB). The three variables of incidence angle, initial radius, and YIG thickness have a substantial influence on the width and position of the AB, which can be adjusted according to the actual demand and are of high application significance. The results of this study can be helpful for the design of multifunctional absorbers and radome.