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Magnetically coupled resonance (MCR) wireless power transfer (WPT) system is a promising technology in electric energy transmission. But, if its system parameters are designed unreasonably, output power and transmission efficiency will be low. Therefore, optimized parameters design of MCR WPT has important research value. In the MCR WPT system with designated coil structure, the main parameters affecting output power and transmission efficiency are the distance between the coils, the resonance frequency and the resistance of the load. Based on the established mathematical model and the differential evolution algorithm, the change of output power and transmission efficiency with parameters can be simulated. From the simulation results, it can be seen that output power and transmission efficiency of the two-coil MCR WPT system and four-coil one with designated coil structure are improved. The simulation results confirm the validity of the optimization method for MCR WPT system with designated coil structure. [ABSTRACT FROM AUTHOR]

The vibration of reactors not only produces noise pollution, but also affects the safe operation of reactors. Giant magnetostrictive materials can generate huge expansion and shrinkage deformation in a magnetic field. With the principle of mutual offset between the giant magnetostrictive force produced by the giant magnetostrictive material and the original vibration force of the reactor, the vibration of the reactor can be reduced. In this paper, magnetization and magnetostriction characteristics in silicon steel and the giant magnetostrictive material are measured, respectively. According to the presented magneto-mechanical coupling model including the electromagnetic force and the magnetostrictive force, reactor vibration is calculated. By comparing the vibration of the reactor with different inserted materials in the air gaps between the reactor cores, the vibration reduction effectiveness of the giant magnetostrictive material is validated. [ABSTRACT FROM AUTHOR]

This paper studies the dynamic response performance of giant magnetostrictive acceleration sensors. A magneto-mechanical strongly coupled dynamic model is presented, which is calculated by means of the finite element method. According to the proposed model, the time characteristic of the induced voltage for the acceleration sensor built with rare earth giant magnetostrictive alloy is calculated. A comparison between the calculated results and measured ones has been carried out to examine the validity of the proposed dynamic model and the FE implementation. It is found that they are in an agreement. This indicates that the proposed FE model can reflect dynamic response performance of giant magnetostrictive acceleration sensors. [ABSTRACT FROM AUTHOR]

A numerical model of displacement for a giant magnetostrictive actuator was founded. According to the model and the measured magnetic characteristic of giant magnetostrictive material, the relation between input current and output displacement for the actuator was calculated by means of the finite element method. A comparison between the calculating result and experimental one for the actuator was carried out and it was found that they were in agreement well. This demonstrates that the numerical model can be used for the design of giant magnetostrictive actuators. [ABSTRACT FROM AUTHOR]

Inverter-fed induction motors generate large vibration and noise because of the Maxwell electromagnetic stress between stator and rotor, magnetostrictive stress of silicon steel and the harmonics in load current. On the vibration reduction study of motor cores, many researchers kept their eyes on control strategy. However, they did not compute stress of inverter-fed induction motor under sinusoidal and harmonic excitations. The nonoriented silicon steel in motor cores shows remarkably anisotropic magnetization and magnetostrictive properties under sinusoidal and harmonic excitations. Thus, in order to compute motor stress accurately, anisotropic magnetic properties must be considered. First, anisotropic property of silicon steel under sinusoidal and harmonic excitations is tested to support the stress computation. Then, an electromagneto-mechanical coupled model for motors considering anisotropic magnetization and magnetostrictive properties is proposed and stress distribution of motor cores is calculated. Finally, the frequency spectrum of the stress is analyzed to provide the theoretical basis for further research of inverter-fed induction motor vibration and noise reduction. [ABSTRACT FROM AUTHOR]

To provide technique references for vibration reduction of magnetically controlled reactors (MCRs), stress, which is the inherent reason of vibration and noise, should be investigated. Stresses in reactor cores are produced due to the magnetostriction deformation of silicon steel and electromagnetic force between the core discs. So far, stress analysis on reactor cores was based on one-way coupled numerical method, which did not consider the influence of the stress on magnetic properties of the core material. Thus, multi-group magnetization and magnetostriction characteristics curves of silicon steel under different tensile stresses are measured firstly to support the computation. From the experiment results, it can be seen that magnetic properties of silicon steel change with stress. Then an electromagneto-mechanical two-way coupled numerical model for MCRs considering magnetostrictive effect and electromagnetic force effect is proposed. Stress distribution of MCR cores under the combination excitation of the sinusoidal wave current and different direct currents are calculated. From the computed results, it can be seen that a larger direct current has greater influence on MCRs vibration, which provides a theory basis for further analysis of vibration and noise reduction. [ABSTRACT FROM AUTHOR]

Global optimization algorithms are widely used to effectively suppress the torque ripple in switched reluctance motors (SRMs). In this paper, an improved velocity-controllable particle swarm optimization algorithm (VCPSO) is proposed to optimize the turn-off angle of an SRM under the current chopping control (CCC) method. In addition, the performances of three global optimization algorithms are compared and analyzed. The specific steps are outlined as follows. First, the static non-linear inductance–current–position and torque–current–position curves of the SRM are obtained through finite-element calculations, and a non-linear model of the SRM is established on this basis. Second, the turn-off angle optimization method based on the VCPSO is proposed. Finally, the performances of the simulated annealing algorithm (SA), the genetic algorithm (GA), and the proposed algorithm are compared and analyzed in terms of torque ripple suppression. The obtained results show that the proposed VCPSO has the advantages of a low number of iterations, low torque ripple, and small peak current in the torque ripple reduction issue of the SRM. [ABSTRACT FROM AUTHOR]

The amorphous alloy used in a switched reluctance motor core can greatly improve the efficiency of the motor. However, its large magnetostrictive coefficient and strong stress sensitivity (i.e., inverse-magnetostriction effect) increase the core vibration and limit the precise control capability of the electrical signals. A vibration reduction method based on the inverse-magnetostriction effect is proposed to control the electromagnetic vibration of a switched reluctance motor with amorphous alloy cores (SRMA). First, a nonlinear magnetostriction and inverse-magnetostriction effect model (NMIE model) of an amorphous alloy and the compressive stress applied structure for the stator teeth are proposed. Then, considering the influence of static compressive stress and dynamic electromagnetic stress on the magnetic properties of the core material, a two-way dynamic electromagnetic force coupling model of the SRMA is constructed and solved. Finally, the vibration characteristics of the SRMA core are calculated. The obtained results show that the radial electromagnetic stress of the improved structure is reduced by 33.6%, which verifies the feasibility of the proposed vibration reduction method. [ABSTRACT FROM AUTHOR]

Magnetically controlled reactors (MCRs) are widely used as reactive power compensation equipment owing to their favorable properties of smoothly adjusting their inductance value through dc bias. However, the dc bias and the rotational magnetization at corner and T-joint areas make the cores of MCRs saturated, resulting in high magnetostriction and vibration. Thus, the electromagnetic vibration analysis of MCRs must consider the vector hysteretic magnetostriction effect. In this article, a vector hysteretic magnetostriction model of silicon steel is proposed by combining the quadratic domain rotation model with the vector inverse Jiles–Atherton model firstly. Then, based on the measured magnetization and magnetostrictive characteristics curves of silicon steel, the model’s parameters are optimized by velocity controllable particle swarm optimization (VCPSO). Finally, the vector hysteretic magnetostriction model is combined with the finite element method (FEM) to simulate the vector vibration characteristics of MCR under dc bias. The simulation results show that the vector property of electromagnetic vibration and magnetic field at the T-joint area is higher than that at other areas. And the MCR vibration test results are consistent with the simulation results, which verify the accuracy of the proposed model in simulating electromagnetic vibration. [ABSTRACT FROM AUTHOR]

The vibration of permanent magnet synchronous motor (PMSM) cores is related to the rotation speed. This paper presents a generalized magnetoelastic 3-D finite-element model, which can be used to calculate the magnetic field and structural vibration of laminated cores, including magnetostrictive effect. Magnetostriction (MS) is a property of electrical steel and causes the vibration of motor cores, the primary cause being electromagnetic forces. To implement the model, the vibration of a PMSM core was numerically analyzed under excitation with different frequencies. The speed and vibration were measured simultaneously by pulse and accelerometer sensors, and the variation of speed and vibration features was analyzed by Fast Fourier Transformation (FFT) versus Revolutions per minute (RPM). The numerically analyzed results showed that the vibration due to MS is important, and the magnitude of vibration is related to the operating speed. Vibration and speeds of the motor were tested and analyzed. The results showed that there is a vibration peak in the range of 600–2000 r/min (30–100 Hz), which is acceptable in calculation. [ABSTRACT FROM AUTHOR]

The total noise level of transformers is mainly influenced by harmonics in load current. The reasons are the interaction of harmonics with large load current at power frequency and the rising sound radiation efficiency with frequency. It is noted that the dynamic vibration behaviors under load harmonics operation are important to decrease the equipment noise. This paper mainly studies the vibration noise effects of three-phase three-leg transformer with the load of wireless power transfer (WPT) system, which would bring harmonics in the load current. Accelerometer sensors were arranged on the surface of the cores and windings of the transformer. Then, the vibration was measured in different positions of a transformer under the power of WPT system from 0 to 20 kW. The spectral distribution of vibration was obtained through the fast-Fourier transform analysis of the acquisition signals. The experimental results with and without PWT load imply that the harmonics in load-current have great effect on the vibration noise. It is to conclude that the main several harmonics of load current should be eliminated to reduce the vibration noise level. [ABSTRACT FROM AUTHOR]

A kind of magnetic fluid acceleration sensor (MFAS) is presented in the paper, which is using the magnetic and fluid characteristic of magnetic fluid. First, the output characteristics of MFAS and its static sensitivity are analyzed based on minimum potential energy principle, the result indicates the linear relationship between output voltage and acceleration. Then, the experimental research is carried out and compared with piezoelectric acceleration sensor simultaneity based on ZJY-601A experiment platform. The output signal of MFAS is sampled and processed by the signal processing system, the output waveform demonstrate that the experimental results are both in agreement with theoretical analysis and output of piezoelectric acceleration sensor. Finally, system errors and influencing factors on measurement sensitivity are analyzed qualitative. [ABSTRACT FROM AUTHOR]

To obtain the deformation characteristic of silicon steel with yoke clamping applied under an alternating magnetic field, a stress-dependent magnetostriction model of silicon steel must be constructed. Due to the magnetic domain's rotation and the magnetic domain wall movement with stress applied, the material's magnetostrictive deformation will reverse and saturate in both magnitude and direction. Therefore, the saturated magnetic domain wall movement effect must be considered in the stress-dependent magnetostriction model. Firstly, a hysteresis stress-dependent magnetostriction model based on the Jiles-Atherton (J-A) model and Zheng-Liu (Z-L) model is proposed. Then, the magnetostrictive deformation curves of the non-oriented silicon steel with external stresses are measured. The magnetic field and deformation parameters that control the saturated magnetic domain wall movement are extracted and applied to the model. Finally, the magnetostrictive loops with the magnetic field under varying stress are obtained based on the proposed model. The proposed model's effectiveness and accuracy are verified by comparing the measurement results with the simulation results. [ABSTRACT FROM AUTHOR]

Magnetostriction (MS) caused by the global magnetization of limbs and yokes and magnetic forces are the undisputed causes of the vibration and noise in power transformer cores. This paper presents a novel way to reduce the vibration and noise, in which nanocrystalline soft magnetic composite (NSMC) material with high permeability is used to fill the step-lap joint gaps of the power transformer magnetic cores. In order to numerically predict the effectiveness of the proposed method, a 3-D magneto-mechanical strong coupled model including MS and magnetic anisotropy of steel sheet was founded. Then, the numerical model was applied to analyze the step-lap joint region of the corner of magnetic cores. The analysis results illustrated that the deformation and noise of core with NSMC are lower than with the traditional epoxy damping material. Moreover, the validity of the proposed new way was verified by the simplified step-lap joint cores, which were achieved based on Epstein Frames. [ABSTRACT FROM AUTHOR]

The precise 3-D magnetic property measurement of the silicon steel is important to improve the efficiency and performance in electrical equipment, such as electrical machines and power transformers. An improved 3-D magnetic property measurement method of the silicon steel laminations is proposed by using a novel sensing structure with interconnecting multiple sensing coils covered on the surface of the cubic specimen. Based on the new coil structure with high precise coefficients from comprehensive calibration, the accurate relationship between B and H vectors is obtained and analyzed under alternating and 3-D rotating excitations with the feedback control method, especially when the laminated direction is considered. Consequently, the experimental data of magnetic properties with high precision can be obtained, which can provide important reference in designing and optimizing electrical equipment. [ABSTRACT FROM AUTHOR]

In order to study and analyze the rotating magnetic properties for nanocrystalline material, an improved 2-D high-frequency magnetic properties tester with step-shaped excitation windings and composite sensing structure is designed and modeled. Magnetic concentration and core poles optimization are performed in 2-D tester construction, which can generate relatively uniform and strong magnetic field in the testing area. By using the composite sensing structure of sensing coil combined with needle probe method, $B$ and $H$ signals can accurately be detected. Meanwhile, feedback control algorithm and harmonic compensation are established to obtain the desired magnetization curves and improve the measurement precision. [ABSTRACT FROM AUTHOR]

A new closed-loop magnetic current sensor is presented in this paper. The sensor consists of two toroidal magnetic cores. One core works in fluxgate principle for the measurement of dc and low-frequency ac, and the other one is used as a current transformer for higher frequency application. Based on the simulation results, a prototype was designed, and the test results have a good agreement with the simulation results. The closed-loop configuration with a magnetic core and a feedback winding in the sensor improved the sensitivity of the sensor, eliminated the offset and drift related to temperature, and greatly reduced the error caused by magnetic hysteresis phenomenon. It can measure currents up to 20 A, with an accuracy of 0.5%, and a 50 kHz small signal bandwidth. [ABSTRACT FROM PUBLISHER]

Based on the Armstrong model and the established electromechanical model of a Galfenol cantilever energy harvester, a nonlinear dynamic model is proposed to describe the mechanical-magneto-electro coupled characteristics of the device. Comparisons between the experimental and calculated results show that the proposed model can provide a reasonable qualitative indication of data trends, and can predict the effects of the acceleration excitation, the load resistance, and the bias magnetic field on the output performance of the device, thus has very strong practicability. [ABSTRACT FROM PUBLISHER]

A meshless method called the element-free Galerkin method (EFGM) is introduced into the calculation of magnetostrictive thin film. With the finite element method (FEM), the distortion of the elements will decrease the precision, so EFGM is used to solve this problem. Two different magnetomechanical coupling models are proposed and a thin film cantilever is simulated with these two modeling methods. At last, the results are compared with the experiment data to illustrate the performance of EFGM and the correctness of the models. [ABSTRACT FROM AUTHOR]

Background: Spermatogenesis is a cellular differentiation process that includes three major events: mitosis of spermatogonia, meiosis of spermatocytes and spermiogenesis. Steady-state spermatogenesis relies on functions of spermatogonial stem cells (SSCs). Establishing and maintaining a foundational SSC pool is essential for continued spermatogenesis in mammals. Currently, our knowledge about SSC and spermatogenesis is severely limited in domestic animals. Results: In the present study, we examined transcriptomes of testes from domestic yaks at four different stages (3, 5, 8 and 24 months of age) and attempted to identify genes that are associated with key developmental events of spermatogenesis. Histological analyses showed that the most advanced germ cells within seminiferous tubules of testes from 3, 5, 8 and 24 months old yaks were gonocytes, spermatogonia, spermatocytes and elongated spermatids, respectively. RNA-sequencing (RNA-seq) analyses revealed that 11904, 4381 and 2459 genes were differentially expressed during the gonocyte to spermatogonia transition, the mitosis to meiosis transition and the meiosis to post-meiosis transition. Further analyses identified a list of candidate genes than may regulate these important cellular processes. CXCR4, a previously identified SSC niche factor in mouse, was one of the up-regulated genes in the 5 months old yak testis. Results of immunohistochemical staining confirmed that CXCR4 was exclusively expressed in gonocytes and a subpopulation of spermatogonia in the yak testis. Conclusions: Together, these findings demonstrated histological changes of postnatal testis development in the domestic yak. During development of spermatogonial lineage, meiotic and haploid germ cells are supported by dynamic transcriptional regulation of gene expression. Our transcriptomic analyses provided a list of candidate genes that potentially play crucial roles in directing the establishment of SSC and spermatogenesis in yak. [ABSTRACT FROM AUTHOR]