International Journal of Applied Electromagnetics and Mechanics

This paper presents a novel double-magnetic-source magnetic circuit (DMSMC) with pole shoes (PS) in order to achieve high and uniform air-gap magnetic field in an angular vibration exciter. First, the structure of the DMSMC with PS is proposed based on the demand of the angular displacement of 60 ∘ , in which the four pair of permanent magnets are adopted. After that, the DMSMC is modeled and analyzed theoretically by the equivalent circuit method, which has been verified that the magnetic circuit structure can realize high magnetic flux density (MFD) in the axial air-gap. To improve the uniformity of the MFD, the DMSMC with PS is proposed and the role of PS is analyzed by the principle of magnetic flux refraction. Then, the influence factors of the MFD in the air-gap, such as the permanent magnet with or without PS, the parameters of the magnet and the PS, are analyzed with the finite element method. The simulation results demonstrate that the optimized DMSMC with PS can obtain high and uniform MFD in the air-gap. Finally, the experimental results for the angular vibration exciter prototype prove to be well consistent with the simulation results, which further verify the validity of the proposed magnetic circuit structure.

Vibration based energy harvesting with piezoelectric material is considered as an alternative power source to run the low power devices, specially for remote area where power is unavailable and also increasing high power demand in the world. This paper presents prototype implementation of non-controlled rectifier circuit utilizing piezo-bending generator (PBG) to estimate output power. This study also investigates the output power of PBG by choosing different capacitances, resistive loads and diodes. In this study, a non-controlled full-wave rectifier is designed and implemented for energy harvesting circuit (EHC). The energy harvesting rectifier circuit is simulated using Matlab software and implemented into prototype board to verify the results. Finally, the study concludes that the output power of the rectifier circuit is high with low resistive loads and Schottky diodes, and the output voltage becomes smooth with suitable value of capacitance.

In the present formulation, we used a theoretical approach to observe the behavior of electromagnetic wave scattering from a time reversal symmetry protected/broken topological insulator cylinder of infinite length, when coated with isotropic plasma layer. By using constitutive relations of topological insulator in Maxwell’s equations, electromagnetic scattered and transmitted field equations were refined and expanded in terms of cylindrical wave vector functions. After applying boundary conditions at both interfaces, scattering coefficients were obtained. Scattering behavior was observed by varying isotopic plasma parameters, i.e., plasma density, collisional frequency and core radius. After analyzing the computational results, it was noticed that the scattering behavior of time reversal symmetry protected and symmetry broken topological insulator can be tuned by varying the plasma parameters.

Multiphysical optimization design of electrical machines is essential, in which the submodels, including electromagnetic, thermal and noise/vibration (NV) simulation models are required not only to be accurate to facilitate coupling analysis, but also of small computation to guarantee calculation speed. In this paper, a multiphysics design flow for salient electrical machines is proposed. The flow aims to maximize torque with temperature rise and acoustic guaranteed, in which each submodel of fast and accurate calculation is respectively studied. For electromagnetic analysis, an efficient finite element (FE) based program is proposed to model distribution of magnetic saturation on salient poles. For NV analysis, an analytical frequency estimation approach is proposed. For thermal analysis, a lumped parameter network model with compensation elements is studied. An 8/6 salient switched reluctance machine (SRM) of high power density for vehicular traction application is studied.

Light electric vehicles (LEVs) have attracted growing attention by the governments worldwide due to their advantages of zero emission, low noise and energy saving. Interior permanent magnet synchronous motor (IPMSM) is a popular choice for LEVs drive systems because of its high power density, excellent flux-weakening capability and high efficiency. The different rotor structures of IPMSMs can affect the performance of the LEV drive system. And their electromagnetic parameters play the decisive role on the control performance of the motor. In this paper, the conventional inset-type IPMSM and the V-shape IPMSM are designed and compared based on finite element method (FEM). Moreover, the field-weakening performances in these two topologies are studied. Besides, the prototypes with these two rotor structures are manufactured and tested to experimentally verify the correctness of the FEM analysis.

Due to their advantages of high efficiency, high power density, short end turns and high slot fill factor, the fractional-slot concentrated-winding interior permanent-magnet (FSCW-IPM) machines have been gaining interest over the last few years. This paper investigates the reluctance torque of FSCW-IPM machines with different slot-pole (S/P) configurations. Firstly, the calculations of the inductances of d -axis and q -axis are analyzed and derived, showing that the reluctance torque of the FSCW-IPM machines is closely related to the S/P configuration. Then, the reluctance torque of eight FSCW-IPM machines is comparatively investigated by using the finite-element analysis. For a fair comparison, these machines are designed based on the same size. Their electromagnetic performances, such as speed range, field-weakening capacity, are analyzed and compared. Finally, the results reveal that low pole-number and high slot-number FSCW-IPM machines have the potential to offer high reluctance torque and good field-weakening capacity.

Lumped parameter method based on Motor_CAD is a conventional and convenient method to analyze temperature characteristics of electric machines. It can directly display the temperature distribution and temperature variation in different nodes of the machine. However, it is only appropriate for eight kinds of traditional rotary motors, not suitable for linear motors. In this paper, a tubular linear oscillating motor (TLOM) is proposed to directly drive hydraulic servo pump in electro-hydrostatic actuator (EHA). A node thermal modeling method based on sectionalized equivalent thermal circuit is presented to analyze steady and transient thermal status of this linear motor, which reflects the spatial thermal characteristic in details and systematically. A research prototype of the motor has been developed, and thermal experiments under different current inputs are conducted. The temperature behaviors with/without forced airflow are studied and compared. Both finite element methods (FEM) and experimental results validate the analytical thermal models under different working situations. This study provides a simple method for design optimization and it is also greatly useful for control implementation of the TLOM.

In terms of the generation of the over-voltage, caused by the coupling between overhead transmission lines and lightning electromagnetic fields, an experimental model was built to simulate the coupling, based on the theoretical analyses. It is concluded that when the overhead transmission lines couple with the lightning electromagnetic fields, there is less low frequency component but more high frequency one in its spectrum than the source, thus the coupled waveform is steeper, and the time is shorter than the excitation waveform, about 2 μ s; Meanwhile, the coupled voltage linearly increases with the addition of the electric resistance while the resistance of overhead transmission lines is below 510 Ω , however, if the resistance is above 300 k Ω , the circuit approximates an open one; The peak value of the coupled voltage has a positive correlation with the increase of the height and the length, while the height ranging in 1–3 m and the length in 10–30 m. There is an accordance between the experiments and the theoretical analyses, which is significant to the lightning protection on transmission lines.

To investigate the light flash intensity and spectral characteristics produced by high-velocity impact on solar array at the same projectile incidence angles and the different impact velocities, the experimental measurements of light flash and the spectral radiant intensity, for 2A12 aluminum projectile high-velocity impact on solar array, have been conducted through an measurement system of optical transient pyrometer, spectral acquirement system and ultra-high speed camera system by using two-stage light gas gun loading system at the different impact velocities and 45 ∘ incidence angle of the projectile. Experimental results show that the peak values of the light flash intensity is the biggest at the wavelength of 600 nm among the wavelengths of 550 nm, 600 nm, 650 nm and 700 nm during 2A12 aluminum projectile high-velocity impact on solar array at the given experimental conditions. And variations of light flash from the optical transient pyrometer and the photographs acquired by the ultra-high speed camera are synchronous. Meanwhile, the relationships of spectral radiant intensity were given about material’s elemental compositions of the projectile and target with impact velocities in the paper. Spectral signatures created by high-velocity impact can be utilized as the basis for deep space exploration, which can characterize the material’s elemental compositions of the projectile and target.

Permanent magnet synchronous motors (PMSM) are now the focus of application in electric vehicle. Unbalanced magnetic pull (UMP) have been identified as the main cause of noise and vibration in PMSM, rather than torque ripple and cogging torque. In this paper, analytical model of unbalanced magnetic pull from non-uniform magnetic field is investigated theoretically based on Maxwell stress tensor approach. Then, a procedure for calculating magnetic forces based on the 2-D finite element method (FEM) is presented. The FEM results validate the magnet distribution and UMP of analytical results. Also, experimental measurement of electrical quantities and forces with static eccentricity were carried out with one special test fixtures. The analytical model is validated by comparing their results with finite-element and experimental under statistic and dynamic eccentric. Relying on the unique assumption of one-dimensionality, the present analytical model appears as a useful tool for parameters design and behavior understanding.

To achieve the radial displacement self-sensing detection of a bearingless induction motor, a prediction model or estimation method of radial displacement based on least squares support vector machine (LS-SVM) is presented. Firstly, the nonlinear relationship between the radial displacement of bearingless rotor and the currents of two sets of stator windings is analyzed. Then, the stator current components of torque windings and suspension windings, and the rotor flux-linkage of torque system are taken as input variables, the acceleration of α and β radial displacement components are taken as output variables, and based on the regression principle of LS-SVM, the predication model or estimation method of radial displacement based on LS-SVM is designed. Based on this, the radial displacement sensorless control system of a bearingless induction motor is constructed. Simulation results have shown that when the presented displacement estimation method is adopted, quicker tracking speed and higher tracking accuracy of radial displacement can be obtained; meanwhile the control system of bearingless induction motor has stronger ability of anti load torque disturbance.

In this paper, we proposed an approach to suppress the lightning electromagnetic pulse for receiver by utilizing lightning protection device. The equivalent circuit model of the antenna in receiving state together with the lightning protection device is established for both theoretical and numerical analysis. The combination wave generator (CWG) was used to generate 8/20 μ s current injected into the return stroke channel, and the induced overvoltage and energy distribution the lightning electromagnetic wave coupled by receivers have been analyzed. Results illustrate that the induced lightning overvoltage can be well suppressed by using the proposed circuit, and the additional circuit has little effect on the performance of the antenna. The experimental results have good agreement with that of the theory of equivalent circuit.

The mathematical description of 3D magnetic surfaces is of paramount importance in several applications, but the solution can be hard in terms of the computing effort or unsatisfactory in terms of accuracy.

The paper proposes an effective methodology based on the tracking of a limited portion of the magnetic field line and on the fitting of the line onto a 3D surface described in a suitable set of 3D shape functions.

In this way, the field line plays the role of a non-uniform sampling of the magnetic surface and the minimization of a suitable error allows the determination of the expansion coefficients. The computational cost of the line tracking can be limited according to the actual precision needs.

The proposed approach allows the introduction of a number of indexes suited to estimate the accuracy and, if the case, to indicate how to upgrade the fitting parameters to meet the actual requirements.

In this paper, we demonstrate the coordinated application of voltage switching type surge protective device (SPD) and voltage limiting type SPD utilizing the theory of the wave propagation and circuit. And the connection between the two devices are 3 m, 5 m, 7 m and 10 m length wire, equivalent hollow or magnetic core inductance, respectively. Based on the experimental data, results indicate that as decoupling devices, the wire, the hollow inductance and the magnetic core inductance with the same inductance value are equivalent. Moreover, the inductance between the gas discharged tube (GDT) and the ZnO varistor should be larger properly, because of the magnetic saturation of the magnetic core inductance.

This paper focuses on the electromagnetic properties of new cylinder type twelve-pole permanent magnet eddy current coupling. By combining conventional equivalent magnetic charge method and superposition principle, the analytical calculation model of air gap magnetic field distribution for the cylinder type permanent magnet eddy current coupling is established; by considering the skin effect, the analytical model of eddy current density is set; the analytical model of electromagnetic-transfer torque is given with the demagnetization effect taken into consideration. Based on the established analytical calculation model, the variation law of air-gap magnetic induction intensity, eddy current density distribution and magnetic torque characteristic curve are analyzed and plotted in detail. At the same time, finite element simulations of the air gap magnetic field, eddy current density and electromagnetic-transfer torque are carried out based on multi-physics, and the results are compared with analytical calculations. Moreover, the paper analyzed the thickness of magnet conductive plate impacts on eddy current and explored relations between torque and coupling distance under different pole pairs. Finally, in order to verify the simulations, the prototype test of torque transfer characteristics is carried out. This paper compares the experimental results with the theoretical analysis and simulation results, and finds out the error is within the allowable range.

Compared with the traditional vacuum turbo-molecular pumps (TMPs) with oil-lubricated bearings, magnetically suspended TMPs can obtain an ultra-clean and ultra-high vacuum environment. Considering the poor heat dissipation condition of rotor and miniaturization of industrial applications, this paper focuses on loss optimization and thermal analysis of a heteropolar magnetic bearing (HeMB) for a vacuum TMP. Loss and mass of HeMB were minimized with multi-objective genetic algorithm optimization. Thermal performance predictive calculation is conducted by analytical model and by finite element method (FEM), respectively. To verify the optimization design and anylysis, the relative tests were implemented on a prototype. For the mechanical and electrical products applied in vacuum, loss optimization and thermal analysis at design stage are very important to the implementation of the system performance.