This paper proposes a novel high-speed axial flux permanent magnet synchronous motor (AFPMSM) using hybrid permanent magnets (PMs) to reduce the magnet cost and torque pulsation. Based on a previously reported model with sinusoidal NdFeB PMs, the proposed model is designed with an equal arrangement of ferrite and NdFeB PMs, wherein the hybrid PMs are parallel and vertical to the magnetization direction of the PM. Therefore, three kinds of hybrid PM configurations are adopted for the proposed model. The analysis by the magnetic circuits is firstly carried out. And then the optimal PM configuration for the proposed model is obtained by comparing the electromagnetic performance with the aid of the finite element method.
Magnetic manipulation is a method used for biomedical applications to remotely control micro-robots in a contactless manner. The electromagnet manipulator should control a magnetic field with 3 degrees of freedom inside a region of interest. In various case studies, this field is the result of the superposition of three decoupled uniform magnetic fields. Each of them is individually generated by a different pair of Helmholtz coils. Such arrangement requires the pairs to be nested within each other, inevitably reducing the size of the working area, degrading the performance and the integration of the whole system. The proposed work aims to design a novel electromagnetic manipulator with the help of computational design, to explore beyond the Helmholtz coils arrangement. A topology optimization framework is developed for this purpose. It investigates the distribution of coils that achieves the largest working area, while keeping the different degrees of freedom balanced.
In practice, due to the difficulty in obtaining the precise probability distributions of the uncertain variables, the stochastic reliability-based design optimization (RBDO) methods can hardly be effective in various cases. On contrary, the variation intervals of the uncertain parameter can be relatively easily achieved. In terms of this condition, an efficient sequential optimization and reliability assessment method of decoupled scheme is developed in this paper for the non-probabilistic RBDO (NRBDO) of electrical machines with interval uncertainty.
The rise of shape and topology optimization techniques has opened new possibilities to find innovative designs for electromagnetic devices such as actuators or rotating machines. This paper provides an analytical sensitivity analysis for the magnetic force and torque based on the virtual work principle and suitable for those kinds of optimization.
Energy-based (EB) hysteresis models are thermo-dynamically consistent formulations for the physical process of magnetic hysteresis and can efficiently be used in Finite Element (FE) implementations. However, a shortcoming of classical EB models is the correct modelling of vanishing rotational losses in the range of saturation. In this contribution, two adaptions of the EB model are presented, by which rotational losses can qualitatively be included into the model. The proposed adaptions are included in a FE simulation of a rotating magnetic field and compared to simulations of a classical EB model.
This paper proposes two novel methods for upscaling the macroscopic magnetic field from the local solutions in magneto dynamic multiscale problems. Unlike the volume average method classically used, these methods yield accurate values of the macroscale magnetic field for problems with strong locally-confined eddy currents which enables B-conforming multiscale formulations of eddy current problems at higher frequencies.
The eddy current (EC) sensor has been developed and, probe signals for arbitrary defect orientation are investigated. The focusing field probe is selected as an eddy current probe to achieve a high sensitivity for the crack detection. The weakness of focusing field probe is its narrow detection area, so we investigate the technique to extend the detection area by application of pre-magnetization. The permeability on the surface of a test piece varies around the defect, its change can make the eddy current perturbed, and give options for improving the sensitivity for the defect oblique angle and lateral misalignment. The calculated results show the sensitivity can be improved, which overcomes the major limit of conventional focusing field probe on the ferromagnetic material.
In this paper, a hybrid algorithm is proposed by combining the NSGA-II with MOPSO algorithm. The original NSGA-II is improved by adopting dynamical selection of crossover and mutation operators. The performance of the proposed hybrid algorithm is verified using standard test functions and it is applied to the multi-objective optimization benchmark problem TEAM 22. Numerical results demonstrate the effectiveness and superiority of the proposed hybrid algorithm.
Low-frequency magnetic fields emanated by wireless power transfer systems expose human beings in their vicinity and induce electric fields into the biological tissues. These potentially harmful induced body-internal electric fields should not exceed the ICNIRP recommended strength limits. The Scalar Potential Finite Difference scheme can be utilized to determine these induced electric fields and thus to assess the human exposure but requires the magnetic flux density distribution in the volume of the exposed body as input. The goal of this work is to determine this magnetic flux density distribution from a few in-situ free-space measurements using graphics processing unit (GPU) accelerated interpolation schemes in near real-time. A single NVIDIA Tesla A100 GPU allows a magnetic flux density distribution reconstruction with an ICNIRP recommended human voxel model resolution of 2 mm in less than 1 second based on 19 sampling points using radial basis functions.
This paper proposes a shape sensitivity analysis for the transient eddy current system. The continuum shape sensitivity of the transient eddy current system is derived by using the material derivative concept and the adjoint variable technique. In the continuum shape sensitivity analysis, the state variable equation is an initial-value problem to be solved forward in time. In contrast, the adjoint variable equation is a terminal-value problem, which is solved backward in time. With the state and adjoint variables, the design velocity of the shape sensitivity formula is evaluated and coupled with the level set equation to represent the deforming geometry. A numerical example having the known solution is tested to show the feasibility of the derived sensitivity formula.
A novel evaluation method of the equivalent permeability of soft magnetic composites (SMC) is proposed, referring to the pressing mechanism. Firstly, the microstructure of the SMC is analyzed, and the region between ferromagnetic particles is divided into gaps and pores. An analytical calculation method for two permeability boundaries is derived when the non-ferromagnetic region is completely occupied by gaps or pores. Finally, the accurate homogenized permeability can be determined in terms of composites density and the ratio of gaps and pores which is affected by the manufacturing process parameters during preparation. The proposed method can tentatively predict the magnetic properties of composites, thereby helping select appropriate processing parameters.
In this paper, coupled problems including structural analysis are studied with respect to permanent magnet assistant-synchronous reluctance motor (PMa-SynRM) for railway traction. The PMa-SynRM is one of alternative motor types considering coasting operation in high speed with back electromotive force induced excessively. The mechanical stress variations are investigated according to material of barrier considering each physical properties including mass density, Young's modulus and Poisson's ratio, and the variation tendency according to properties is presented. The effect of stress in electromagnetic performance and rotor iron loss are also analyzed at each operating point and speed. Finally, the proper option for PMa-SynRM is proposed as a solution of coupled problem.
This paper proposes a method combining random forest technique (RF) and genetic algorithm (GA) for optimal design of traction motors for electric vehicles (EVs). The target motor is the permanent magnet assistant synchronous re-luctance Motor (PMa-SynRM) and the design goal is increasing the average torque and efficiency and reducing torque ripple and the total harmonic distortion of line-to-line back elec-tromotive force. The prediction accuracy of the RF was im-proved through hyperparameter tuning and verified through several test functions. The applicability of the proposed method is verified by deriving the optimal design of PMa-SynRM for EVs and improving the target motor performance.
This work presents a numerical model describing the effect of mechanical stress on the impedance signal of an eddy current sensor for an application in non-destructive testing. The anisotropy of the magneto-elastic behaviour of the material (API-5L X52) is taken into account through a simplified multi-scale approach. The constitutive behaviour is implemented into a finite element model to solve the magneto-dynamic problem. The modelling results are compared with measurements performed on samples extracted along two orthogonal directions of a pipeline.
Most existing methods for topology optimization update the material distribution iteratively based on the derivative information. However, the calculation of gradient is of low accuracy and even unavailable in some cases. To this end, this paper proposes a novel derivative free methodology for TO based on affine transformations and Boolean operations. Specifically, the proposed method selects the basic structures to constitute a new topology. Affine transformations and Boolean operations are employed to represent the evolvement and the way of combinations of the basic structures. The numerical result has validated the proposed method.
This paper investigates the influence of stator flux barriers on the short-circuit current (SCC) and braking torque of a dual three-phase permanent magnet (PM) synchronous machine. By optimizing the position and width of stator flux barriers, the machine has a lower amplitude of short-circuit current and brake torque when the short-circuit fault occurs. First, the SCC and braking torque are analytically derived. The amplitude of SCC is proportional to the PM flux linkage and inversely proportional to the inductance. The braking torque is proportional to the square of the PM flux linkage and inversely proportional to inductance. Then, the equivalent magnetic circuit model of flux barriers is established. Its influence on flux linkage and inductance is analyzed, and the improvement mechanism of output torque and fault tolerance is revealed. Furthermore, the flux barriers’ width is optimized by finite element analysis and the theoretical analysis is verified. Finally, experiments on the prototype machine are carried out for the validation.
This study proposes a new analysis method based on lumped magnetic-circuit for surface permanent-magnet machine (SPM) with overhang and step-skewed rotor. In SPM machine, the step-skew lowers the torque pulsation and makes the electromotive force sinusoidal, and the overhang structure increases the torque density. A time-consuming three dimensional (3-D) finite element method (FEM) is required to analyze axial components such as step-skew leakage flux and overhang flux. To deal with this problem, a new equivalent lumped magnetic-circuit model for each rotor step considering the axial leakage flux between the steps and the linkage flux by the overhang is introduced. The validity of the proposed method is verified by comparing a two-dimensional and 3-D FEM of skewed, non-skewed, overhang, and non- overhang SPMs.
This work proposes a circuit model to calculate the current along printed coils used in resonant wireless power transmission systems. The proposed formulation is based on the Neumann formula for calculating the mutual inductance between coils, and due to the generality of this approach, it can be applied to more complex structures such as metasurfaces. Finally, this formulation is used to calculate the scattering parameters of the entire system, making it possible to evaluate its wireless power transfer efficiency. The results obtained agree with the general behavior obtained from electromagnetic simulations in commercial software, with a low error and a reduction in computational time of almost three orders of magnitude.
