The 50 most-cited articles in IEEE Transactions on Magnetics, 2019

Magnetoresistive (MR) sensors have been identified as promising candidates for the development of high-performance magnetometers due to their high sensitivity, low cost, low power consumption, and small size. The rapid advance of MR sensor technology has opened up a variety of MR sensor applications. These applications are in different areas that require MR sensors with different properties. Future MR sensor development in each of these areas requires an overview and a strategic guide. An MR sensor roadmap (non-recording applications) was therefore developed and made public by the Technical Committee of the IEEE Magnetics Society with the aim to provide an research and development (R&D) guide for MR sensors intended to be used by industry, government, and academia. The roadmap was developed over a three-year period and coordinated by an international effort of 22 taskforce members from ten countries and 17 organizations, including universities, research institutes, and sensor companies. In this paper, the current status of MR sensors for non-recording applications was identified by…

Quantum particle swarm optimization (QPSO), inspired from the basic concept of PSO algorithm and quantum theory, is a stochastic searching algorithm. However, the algorithm may encounter a premature convergence when dealing with multimodal and complex inverse problems. Thus, some improvements are introduced. More especially, one will randomly select the best particle to take part in the current search domain. Also, a mutation strategy is added to the mean best position, and an enhancement factor (EF) is incorporated to enhance the global search capability to find the global optimum solution and to avoid premature convergence. Moreover, some parameter updating strategy is proposed to tradeoff the exploration and exploitation searches. Experiments have been conducted on well-known multimodal functions and an inverse problem. The numerical results showcase the merit and efficiency of the proposed modified quantum inspired particle swarm optimizer (MQPSO).

The growth of electric and hybrid electric vehicles has drawn more attention toward the development of high power density electrical machines. The materials used in the fabrication of electrical machines play a crucial role in enhancing their power density. In this paper, the significance of advanced magnetic materials for lamination, nano-material based conducting materials, and high energy product permanent magnets (PMs) is discussed in detail. Finally, a case study has been presented with a 5 kW PM synchronous machine in order to understand the advantages of the discussed materials.

The computational cost of topology optimization based on the stochastic algorithm is shown to be greatly reduced by deep learning. In the learning phase, the cross-sectional image of an interior permanent magnet motor, represented in RGB, is used to train a convolutional neural network (CNN) to infer the torque properties. In the optimization phase, all the individuals are approximately evaluated by the trained CNN, while finite element analysis for accurate evaluation is performed only for a limited number of individuals. It is numerically shown that the computational cost for the topology optimization can be reduced without the loss of optimization quality.

This paper investigates the feasibility of novel data-driven deep learning (DL) models to predict the solution of Maxwell's equations for low-frequency electromagnetic (EM) devices. With ground truth (empirical evidence) data being generated from a finite-element analysis solver, a deep convolutional neural network is trained in a supervised manner to learn a mapping for magnetic field distribution for topologies of different complexities of geometry, material, and excitation, including a simple coil, a transformer, and a permanent magnet motor. Preliminary experiments show DL model predictions in close agreement with the ground truth. A probabilistic model is introduced to improve the accuracy and to quantify the uncertainty in the prediction, based on Monte Carlo dropout. This paper establishes a basis for a fast and generalizable data-driven model used in the analysis, design, and optimization of EM devices.

Aiming at the problem of decrease in efficiency due to misalignment of wireless power transfer (WPT) coil, a novel coil with high misalignment tolerance was proposed. First, the factors that affect the efficiency and the method of improving the efficiency and misalignment tolerance of the coil are analyzed. Second, the novel coil was set up through COMSOL simulation, which was compared with double-D (DD) coil and circular coil in misalignment tolerance. Finally, in order to verify the authenticity of theory and simulation, experiment device is implemented and experimental results show that the coupling coefficient changes affect coil efficiency, and the flat and high magnetic flux density can better maintain coil efficiency when lateral misalignment happened. This means that the novel coil has better misalignment tolerance, which can meet the demands of WPT system.

This paper presents a compound propulsion system with a high-speed permanent-magnet synchronous motor (PMSM) and two in-wheel motors for electric vehicles (EVs). In this paper, the longitudinal dynamic model of EVs is first presented. Then traction distribution ratio α is introduced to express the traction distribution between the front and the rear axles. Moreover, the function of power consumption concerned with the traction distribution ratio α is established. Therefore, the α that minimizes the power consumption function is selected as the optimal traction distribution ratio. To improve the performance of motor controllers, the model predictive torque control (MPTC) method is employed for high-speed and in-wheel motor drives. Experimental comparison with field-oriented control (FOC) shows the advantages of MPTC in dynamic response. Finally, experimental comparisons and hardware-in-loop (HiL) tests are presented to verify the MPTC method and the proposed energy allocation method, respectively.

This paper presents the fast topology optimization methods for rotating machines based on deep learning. The cross-sectional image of electric motors and their performances obtained during a multi-objective topology optimization based on the finite-element method and genetic algorithm (GA) is used for training of the convolutional neural network (CNN). Two different approaches are proposed: 1) CNN trained by preliminary optimization with a small population for GA is used for the main optimization with a large population and 2) CNN is used for screening of torque performances in the optimization with respect to the motor efficiency.

This paper proposes and implements a novel multi-frequency multi-power wireless power transfer (MFMP-WPT) system based on one single transmitter for simultaneously and compatibly energizing multi-standard receivers. Generally, implementing a multi-frequency WPT often requires a compromise in system complexity, control difficulty, switching frequency, or transmission efficiency. By using only a single transmitter with an artful inverter topology, the proposed MFMP-WPT system can effectively achieve multi-frequency multi-magnitude superposition and switching frequency reduction while maintaining the control fitness and convenience of square-wave generation with 50% duty cycle. Moreover, by switching at the fundamental frequency in a range of 80-130 kHz, the single transmitter becomes competent for one-to-many MFMP-WPT operation for diverse wireless power on-demands. Consequently, the fundamental and high-order harmonic wireless energies with multiple power levels can be, respectively, picked up by the multi-standard receivers, depending on their energy requirements. The experimental…

This paper proposes and implements a novel quasi-omnidirectional dynamic wireless power transfer (WPT) system using double 3-D coils for drone applications. In the traditional omnidirectional WPT system, the receiver direction is always facing the 3-D transmitter center to maximally pick up the magnetic flux. However, the on-drone receiver normally proceeds horizontal or vertical movements so that it is unable to fully utilize the magnetic flux and result in serious magnetic flux leakage. Thus, by newly proposing the 3-D intermediate coil and artfully aligning specific quadrant of double 3-D coils to the center of the flying area, the proposed WPT system can flexibly and efficiently power the drone in the specific space. Moreover, only one single power source is needed to drive the transmitter coil without using the sophisticated current phase control. Therefore, the proposed system can simultaneously achieve both quasi-omnidirectional WPT and dynamic WPT for the drone so that its flying time can be significantly extended. The theoretical, simulated, and experimental results are…

Smart living is a trending and connected lifestyle that envisions efficient and sustainable energy utilization, stable and reliable power supply, intelligent and coordinated transportation and mobility, and personalized and cost-effective healthcare. Its realization needs the Internet of Things (IoT). IoT is a compelling platform connecting trillions of sensors and collecting data for connectivity and analytics. It is more advanced than traditional monitoring systems where limited sensors and wired communication can merely collect fragmented data in the application domains. Spintronic sensors with the superb measuring ability and multiple unique advantages can be one of the critical sensing devices supporting the IoT and enabling smart living. In this paper, we review successful applications of individual spintronic sensors in electrical current sensing, transmission and distribution lines monitoring, vehicle detection, and biodetection that can help to fulfill the promises of smart living in energy management, power delivery, transport, and healthcare. The wireless spintronic…

Automation of flexible surgical instruments requires the development of robotic technologies capable of small-scale power transmission. Magnetic actuation has successfully been used for that purpose. Nevertheless, current systems for magnetic actuation suffer from small workspaces or poor bandwidth of magnetic field control. In this work, we design, develop, and test a novel magnetic actuation system called Advanced Robotics for Magnetic Manipulation (ARMM). The ARMM system employs a 6 DoF mobile electromagnetic coil capable of generating prescribed magnetic fields and gradients. The mobile coil approach allows for easy scaling of the actuation workspace, which depends on the range of robotic arm, and in our case spans up to 1.3 m. Due to limited end-effector payload of the robotic arm used in the ARMM system, the mobile coil has been designed using an optimization routine. For a given mass and heat dissipation constraints, this routine provides the coil geometry that maximizes the average magnetic field generated in the target region. Since the Vacoflux core of the fabricated coil…

Accurate calculation of short-circuit (SC) dynamic characteristics of power transformer windings is of great significance to the safety of transformers. A 110 kV power transformer model is established, and SC electromagnetic characteristics and dynamic characteristics of the transformer windings are obtained through magnetic-structural coupling analysis by the finite-element method, considering the nonlinear mechanical characteristics of spacers. The distribution of leakage magnetic field and electromagnetic force (EF) and dynamic stress and displacement of windings are calculated due to SC fault. The SC EF of windings decreases exponentially with time. The axial EF of the disks at both ends of the winding is larger, while the radial EF is smaller, compared with that of central disks. The variation law of winding stress and displacement is similar to dynamic EF. The stress and displacement at both ends of the winding are larger while that in the middle part is smaller. The maximum stress and displacement of the end of windings are nearly 60% and 90% higher than that of the middle…

Two types of surface-mounted permanent magnet synchronous machines (PMSMs) with the same physical dimensions but different stator core materials are comparatively analyzed, prototyped, and tested in this paper. In order to quantify the magnetization and loss characteristics of the stacked amorphous metal (AM) stator core, an experiment is conducted under different supply frequencies. Based on the data, the no-load iron losses, harmonic losses generated by the inverter-induced non-sinusoidal current harmonics, and the d-axis and q-axis inductances of two types of motors are comparatively analyzed by the finite-element method under different conditions and verified by experiments carried out on the two types of PMSM prototypes. The results illustrate that the AM PMSM has a characteristic of extremely low no-load iron losses, relative to the conventional silicon steel PMSM.

This paper presents an analytical model of magnetic field of a permanent magnet synchronous motor (PMSM) with a trapezoidal Halbach permanent magnet array (THPMA). Compared with conventional Halbach array, the shape of each magnet in THPMA is transformed from rectangle to trapezium in polar coordinates. The THPMA is delaminated indefinitely radially and each layer is approximately considered to be a conventional Halbach array. The air-gap magnetic field of each layer is analyzed with the scalar magnetic potential. Then, the air-gap magnetic field of the THPMA is obtained by superposing magnetic fields of all layers. The validity of the analytical model is verified by a finite-element model (FEM). The air-gap flux density is optimized by adjusting the center angle coefficients of the THPMA, and a no-load phase back electromotive force (EMF) with the harmonic distortion rate (THD) of 0.75% is obtained by FEM. The back EMF is basically consistent with the measured result of a prototype motor.

There is always uncertainty in industrial manufacturing. These uncertainties have an undesirable impact on the products if deterministic optimization approaches are employed. In order to have products as desired, uncertainties must be quantified in the design process. This paper presents a robust design optimization of an outer rotor surface mounted permanent magnet motor with particular application in the hybrid vehicle using the design for six-sigma methodology. Due to very long computational time of robust optimization, a ten high-dimensional surrogate model of the system using the Box-Behnken response surface methodology (RSM) is integrated with the particle swarm optimization (PSO). This causes a significant improvement in the effectiveness and efficiency of optimization. The results acquired from RSM are verified by their simulation using the finite-element method, and the accuracy of RSM is proved. Finally, the deterministic and robust optimized motors are simulated in mass production using Monte Carlo analysis, and six-sigma quality achievements are demonstrated.

Magnetic dipole localization methods have a wide application range. Resolving equations of magnetic gradient tensor is a classical method to obtain the direction of the relative position vector, but the real solution hides in four possible solutions. The Scalar Triangulation and Ranging (STAR) method is also effective but is less accurate than the real solution of tensor equations. To solve the two problems, we proposed a novel direction determination approach by combining the advantages of the two methods. Based on the cube tensor measurement array from the STAR method, a novel way to calculate the distance between the dipole and the sensor array is proposed. Then, a novel real-time magnetic dipole localization method is obtained. Results of simulation experiments indicate that our method raises the successful localization area by 43% compared with the traditional method, and the baseline length of the sensor array dominates the performance of our method.

A new axial flux permanent magnet machine (AFPM) with soft magnetic composited (SMC) cores is proposed for electric vehicle (EV) application in this paper. As its windings are wound on the stator ring core, it can be regarded as a toroidally wound internal stator (TORUS) machine. With the adopted SMC material for stator core, this machine has the benefits of 3-D magnetic flux properties. The windings and SMC cores can be designed to form a very compact structure, and thus, the torque density can be improved greatly. To obtain the a good flux concentrating ability, two TORUS machines are designed and analyzed, one is with NdFeB magnet for high-performance EV application and the other is with the cheap ferrite magnet for low-cost application. The 3-D finite-element method is used to analyze the electromagnetic parameter and performance. For performance comparison, a commercial AFPM with yokeless and segmented armature P400 is used.

This paper presents a theoretical and experimental study on high-frequency (>5000 Hz) output characteristics of the giant magnetostrictive transducer (GMT) at varied operating conditions. Based on the Jiles-Atherton model, Maxwell's equations, Newton's law, and Fourier's heat transfer equation, a nonlinear electromagnetic-mechanical-thermal multi-field coupled finite element model for GMT is established. The output displacement amplitude of the magnetostrictive rod and the acceleration of vibrating horn at the GMT device are measured and analyzed at varied exciting amplitude of ac magnetic field and frequencies (from 5600 to 7000 Hz). The frequency dependences of permeability and magnetoelastic coupling coefficient obtained from the experimental results are used in revising the model parameters. These output characteristics analysis results can provide theoretical and experimental guidance in the optimization of structural design and precise controlling for high-frequency GMT system.

This paper investigates the no-load iron loss, on-load loss, and thermal performance of a high-speed surface-mounted permanent-magnet synchronous machine with an amorphous metal stator core (AMSC) and a titanium alloy retaining sleeve by numerical methods. The electromagnetic properties of the AMSC are tested by an experimental platform. The distributions of no-load iron loss, rated-load loss, and the thermal behavior of the motor are investigated under converter supply conditions. Finally, the loss and thermal performances of the prototype are tested and compared with the corresponding simulation results to verify the accuracy of the calculation results and the superiority of the prototype.

Analytical models show weakness in dealing with saturation in surface-mounted permanent-magnet machines. A hybrid field model (HFM) integrating complex permeance method (CPM) and lumped parameter magnetic circuit model (LPMCM) is proposed in this paper for predicting the on-load magnetic field considering nonlinearity effect of stator lamination. In the proposed model, the CPM calculates the field in the air gap and magnet regions, while LPMCM calculates the magnetic potential distribution inside the iron reflecting nonlinearity effect. The equivalent current sheet is obtained to replace such distribution on the stator bore. Moreover, local magnetic saturation of tooth tip is also transformed into equivalent current on the tooth surface. A solving procedure is proposed to calculate the equivalent current and guarantee the convergence. Compared with CPM, the proposed model considering the saturation effect significantly improves the prediction accuracy of the on-load performance. The HFM predictions are compared with finite element and experimental results. The excellent agreement…

In the interior permanent magnet synchronous motor (IPMSM) design for the traction motor of fuel cell electric vehicles (FCEVs), it is necessary to analyze the nonlinear characteristics including saturation due to the requirement of a high torque density. The finite element method (FEM) is the most widely used technique for electric machine designs because complicated computations can be taken into account. However, a large amount of analysis over the entire design is a computationally large burden. To address this problem, this paper proposes a fast and accurate analysis method, sequential-stage magnetic equivalent circuit (SSMEC). The proposed method consists of no-load, q-axis circuit analysis, d-axis circuit analysis, and motor characteristic calculation. Because the proposed method can quickly and accurately analyze the complex shapes of an IPMSM, it can be used effectively throughout the entire motor design process. The effectiveness of the proposed SSMEC was verified in comparing with experimental results.

The foil winding temperature distribution is crucial to the life of power transformer since local heating can accelerate aging of insulation materials. However, based on the traditional 3-D electromagnetic model and the principle of heat transfer, the non-uniform losses and temperature distribution of foil windings are difficult to estimate because of complex magnetic leakage flux. In this paper, the magneto-fluid-thermal coupling model has been established to calculate the temperature rise and predict the potential hotspots of a simplified dry-type power transformer rated at 2500 kVA. Moreover, the influence of insulation barrier is considered to reshape the air-flow path and to affect the radiative effect between the high-voltage and low-voltage windings. Experimental temperature rises are measured with infrared thermography to verify the simulation results, which achieved reasonable hotspot predictions and provide the theoretical method for transformer designers.

The original fuzzy-based Taguchi method is restricted with the number of objective functions. Aiming to solve this problem, this paper describes an improved fuzzy-based Taguchi method (IFBTM) coupled with finite-element analysis (FEA) for the multi-objective optimization of direct-drive permanent magnet synchronous motors (DDPMSMs). To reduce the number of dimensions in the fuzzy rule base, the IFBTM uses a factor stratification method to establish multilayer fuzzy rule base. The fuzzy inference system with multilayer fuzzy rule base is introduced to translate the multiple optimization objectives to a single objective. After optimal selection analysis, the best combination of motor structure factors is obtained with small FEA computation. Finally, the performances of DDPMSM are analyzed and compared with those of IFBTM. The results certify the superiority and validity of IFBTM.

Compared with traditional induction machine and direct current machine, permanent magnet synchronous machine (PMSM) holds many merits like higher torque ability and efficiency when high magnetic co-energy sintered NdFeB magnet is used. However, for the operation with high frequency, the resulted eddy current loss by the permanent magnet (PM) is very high and this kind of loss can bring the PM with high-temperature rise, making the PM face the risk of irreversible demagnetization. To reduce the PM eddy current loss, complete magnet segmentation is an effective method. However, taking this kind of method will increase manufacturing cost and reduce the mechanical robustness of the PMSM. Thus, a partial magnet segmentation method was proposed in the past. In this paper, a new annular partial segmentation (APS) method is proposed for the reduction of the PM eddy current loss, including single-side APS and double-side APS configurations. Considering that the additional process on the PM will reduce the mechanical robustness of the PM and the electromagnetic performance of machine, both…

This paper proposes a novel winding scheme to generate an additional sub-harmonic magneto-motive force (SH-MMF) component for the brushless (BL) operation of a wound-field synchronous machine. The existing SH generation schemes for BL operation use a dual inverter or a single inverter with asymmetrical winding and low slot fill factor in half of the stator. The proposed scheme comprises a single inverter with symmetrical stator winding distribution and the same fill factor for all stator slots. The generated additional SH-MMF component in the proposed scheme is induced in the harmonic winding wound on the machine rotor. A rotating bridge rectifier mounted on the rotor periphery connects the rotor harmonic winding with the rotor field winding, and rectified dc is supplied to the rotor field winding. The 2-D finite-element analysis (FEA) was carried out to analyze the principle, and the FEA predictions were experimentally validated.

Composites loaded with various carbonyl iron-based (CI) materials are fabricated and characterized with regards to their electromagnetic properties and absorption in the X-band (8-12 GHz). The combination of inclusion CI particles and multiwalled carbon nanotubes (MWCNT) is also explored. To this effect, CI micropowder has been successively processed to get the form of flaked, porous, and nanosized TiO2-coated particles, whereas MWCNT has been coated with polyaniline (PANI). The processed fillers were primarily characterized to verify their structural consistency and large variations in the microstructure. The static magnetic properties of the CI-based powders have been analyzed via the vibrating sample magnetometry. Finally, complex dielectric permittivity and magnetic permeability spectra along with the return loss (RL) maps of composites loaded with the powders under study have been extensively investigated. Among the studied samples, the multicomponent composite with core-shell-structured CI-TiO2 and MWCNT-PANI exhibits the maximum magnetic and dielectric losses, which yields…

In this paper, a new asymmetric planar V-shaped magnet arrangement for a linear PM synchronous motor is proposed. Several magnet arrangements for the track of the proposed linear permanent magnet (PM) synchronous motor such as un-skewed magnets, conventional magnet skew, and V-shaped planar magnets have been investigated. The performance results of the linear motor with skewed magnets are compared to those of previously designed PM linear synchronous motor with conventional un-skewed rectangular-shaped (CuSRS) magnets. The forcer is kept the same for all track structures and a thorough comparison is provided for low detent force and low force ripple with the CuSRS and proposed planar V-shaped magnet skew approaches.

Overhang is a useful structure for increasing the torque and power densities of permanent-magnet (PM) machines without expansion of the machine space. A 3-D finite-element method (FEM) is needed to evaluate the performances of PM machines with an overhang structure because the overhang structure results in non-uniform magnetic flux distributions in the axial direction. However, it is computationally expensive, especially in the early design stage. In this paper, we propose a magnetic equivalent circuit (MEC) model considering the overhang effects of interior PM (IPM) machines. With the proposed MEC, the performances of IPM machines with an overhang structure were precisely calculated and the computational time was significantly reduced. The proposed MEC was verified by the 3-D FEM.

This paper presents the topology optimization of the magnetic core for a wireless power transfer (WPT) device. In this optimization, the coil and magnetic-core shapes for WPT are represented by the Gaussian basis functions. They are sequentially optimized using the genetic algorithm and 3-D finite-element analysis so that the coupling coefficient of the WPT device is maximized. Moreover, a robust optimization method is proposed to keep the interlinkage flux as large as possible against misalignment in the coils. It is shown by the computational and experimental results that the optimized device outperforms the conventional devices.

Power allocation is important for dynamic dual-pickup wireless charging system of electric vehicles (EVs). The existing power allocation methods of wireless power transfer technology mainly focus on allocating the power to loads according to the needs with different resonant frequencies. However, the issues of inaccuracy and low power are still not well solved by the existing methods. In addition, the control strategies of existing methods are complex and difficult to implement in practical situations. In this paper, a new power allocation method is proposed, which can dynamically and precisely allocate power to loads. Moreover, the dynamic mutual inductance estimation and the power ratio change between loads are also investigated. In addition, this method has no need to use additional circuits for the receiving coil. Thus, it is convenient to implement in the dual-pickup wireless charging system of EVs. Experimental results have well verified the correctness of the proposed dynamic mutual inductance estimation and power allocation method.

This paper investigates the online fault detection (FD) of the inter-turn short-circuit (ITSC) fault in direct torque control (DTC)-driven induction motors (IMs). We conducted the investigations of harmonic, inter-harmonic, and sub-harmonic contents for FD purposes. The harmonics in the flux leakage spectrum appear as a result of diverse causes including stator fault, DTC reaction to the fault, switching activities, and core saturation effect. Physics-based co-simulation was held through the coupling between a finite-element model (FEM) of the faulty IM and the circuit simulation of DTC. Its advantages are: 1) the IM harmonic contents including stator slots, rotor slots, saturation, switching activity, and fault are simulated and 2) dangerous experimentations of a faulty IM can be avoided. Therefore, we can safely study all the characteristics on a faulty IM. We exploited FEM for the verification of the experimental harmonic signatures of the scattered magnetic field. We verified the online FD technique based on the radiated magnetic field's spectrum through the co-simulation and…

The technology for inductive wireless power transfer (IWPT) by using strongly coupled magnetic resonance has been applied successfully to supply energy to several applications such as biomedical implants, radio frequency identification systems, Internet-of-Things sensors, and battery chargers for personal devices. In order to attain high values of efficiency and reach, the technology requires the employment of coils with high values of quality factor. However, this feature can only be found by using large wire coils. A compact IWPT system composed of printed coils, which typically have low values of quality factor, is proposed in this paper. An evolutionary algorithm is used to optimize the printed coil geometry so that it presents the greatest value of quality factor possible, according to the imposed restrictions. With the aim to improve the system efficiency and reach, the effect of metamaterial surfaces inclusion is investigated. In addition, in order to increase the amount of power processed by the system, a low-cost self-oscillating electronic converter is proposed to power it.

This paper proposes a flux-intensifying permanent magnet-assisted synchronous reluctance motor (FI-PMa-SynRM) using surface-inset permanent magnet (PM) instead of embedded PM in the rotor. The proposed FI-PMa-SynRM employs a small amount of PM that is inset on the rotor surface facing d-axis instead of facing q-axis as in common PMa-SynRMs. It also differs from conventional flux-intensifying interior PM motor, where the PM is embedded inside the rotor. The proposed motor enables making use of the arrangements of two types of flux barriers (FBs): the cutoff FB and the magnet FB, collectively referred to the outer FBs, to enhance the torque output and reduce the torque ripple. The first objective in this paper is to explain the principles of the proposed FI-PMa-SynRM, and the second is to analyze the proposed technique for enhancement of the torque output with small PM volume while keeping the lowest possible torque ripple. The finite-element analysis is employed to validate the proposed motor and analyses, and the results demonstrate their advantages and effectiveness.

In this paper, a new consequent-pole hybrid excitation brushless wound field synchronous machine (CpHE-BL-WFSM) with fractional-slot concentrated winding is proposed. The proposed machine inherits the features of a brushless excited topology in which a rotor field is excited through an additional sub-harmonic magnetomotive force generated by the stator winding arrangement. In conventional BL-WFSMs, the zero starting torque and relatively low efficiency compared to that of permanent magnet synchronous machines (PMSMs) makes it difficult to replace expensive PMSMs in low- and medium-power applications. The advantages of the proposed machine are improved efficiency, improved starting torque, and high electromagnetic torque as compared to conventional brushless machines. A 2-D finite-element analysis is conducted to compare the proposed machine with the conventional BL-WFSM topologies. The results reveal that the proposed machine topology exhibits greater efficiency, improved starting torque, high average torque, and improved torque density.

Magnetic equivalent circuit (MEC) modeling is a challenging work to machines with novel structures, although it is an effective tool in the design process. The parameterized dynamic MEC modeling method is developed in this paper for the analysis of a novel rotor-segmented axial-field switched reluctance machine (RS-AFSRM). The “parameterization” is the feature leading the general MEC models in each interval of the rotor position, and the “dynamic” characteristic depends on the change of the flux patterns in the air region with the rotor displacement. By the proposed MEC model, the RS-AFSRM is analyzed on the smooth transition with efficient computation. The results obtained through the developed MEC models are verified by both the static and motion-coupled analyses.

An increasing need for fast and reliable models has led to a continuous development of Fourier-based (FB) analytical modeling. This paper presents an overview of the techniques that are currently available in FB modeling for electric machines. By coupling that overview to the most relevant literature related to the subject, an interesting starting point is provided for anyone who wants to use or improve FB models. The following seven aspects of FB models are discussed in detail: 1) the magnetic potential (scalar or vector potential); 2) the coordinate system and the solution of the partial-differential equations for each magnetic potential and for each coordinate system; 3) the way in which time dependence is accounted for; 4) the implementation of the source terms; 5) the possibilities to account for slotted structures; 6) the modeling of eccentricity; and 7) the post-processing computation of physical quantities, such as flux density, electromotive force, torque, losses, and eddy currents in conductive objects. Furthermore, this paper gives the closed form solution of the Laplace,…

A quantitative analysis and design guideline for dual-permanent-magnet Vernier machine (DPMVM) are presented in this paper. First, by winding factor analysis for dominant air-gap harmonics, torque components excited by stator PMs and rotor PMs are quantified, which reveals that, in DPMVM, the rotor PMs essentially have higher torque generation ability than stator PMs, due to the effective utilization of fundamental PM harmonic without flux modulation. Furthermore, mutual influence between dual PM sources is analyzed. It is revealed torque contribution of stator PMs is unilaterally affected by design parameters of rotor PMs. Finally, a design guideline is provided for DPMVM, considering the design priorities of dual-PM sources. Finite element simulation and prototype experiments prove the validity of the theoretical analysis.

This article aims at investigating the impact of harmonic current, vibration, and noise on induction motors (IMs) with a fractional order (FO) proportional-integral-derivative (PID) controller. Conventional PID controllers are widely used in closed-loop vector-space to control IMs. In general, the parameters of a PID controller should be considered carefully because the vector-space loop can induce imbalanced current and magnetic flux in the α-β sub-plane closed-loop system. If this occurs, the imbalanced current affects not only the IM performance but also the harmonic current, motor vibration, and noise. In this study, an FO PID (Pp IλDμ) controller is used for stabilizing the effect of the current and harmonic on the IM. This PID controller is built based on the results of measurements on motor design parameters. By using the phase margin rule to design and determine suitable parameters, several orders of p, λ, and μ in their reasonable ranges are evaluated to obtain a relative optimal FO (Pp IλDμ) controller. This can improve the performance of the IM in terms of harmonic…

Electric machine design optimization is a popular topic in electrical engineering. Thanks to major accomplishments in Mathematics and Computer Science, nowadays the investigation of thousands of designs for particular optimization tasks is possible. Huge effort is made for developing evermore complex multi-physics simulation models including, e.g., thermal or mechanical aspects besides electromagnetic performance investigation. The impact of tolerances is often disregarded. This paper gives an overview of recent activities in machine design optimization. Consequently, the implementation of tolerance analyses for machine designs is explained. A categorization based on mathematical tolerance representations, typical tolerance-affected parameters and their respective modeling effort, as well as measures for evaluating the impact of tolerances, i.e., the design's robustness, are discussed. An exemplary sensitivity analysis featuring an interior permanent magnet synchronous machine with spoke-type rotor structure is introduced. The performance of two different designs in the presence of…

This paper presents a multi-objective optimized design for a 75 kW, 24 000 r/min high-speed surface-mounted permanent magnet synchronous motor (SMPSM) for a magnetically levitated flywheel energy storage system. The main goal of the optimization process is to determine the optimal motor geometry, and thus obtain maximum efficiency, minimum weight, and minimum torque ripple in the SMPSM. To achieve this goal, three objective functions are used. The first function is used to obtain maximal output torque, and thus produce highest efficiency; the second function is used to minimize materials utilization to realize the lowest possible production cost; and the third function is used to achieve minimal torque ripple, and thus constrain the motor's vibration and noise. The optimization process uses an ant colony algorithm with continuous domains. The optimized motor parameters can be selected from the Pareto solution set obtained. A comparison of the results calculated using the optimization algorithm with the results obtained using finite-element analysis software shows a good agreement.

The 2-degree-of-freedom (2DoF) rotary-linear (RL) motors are capable of implementing pure rotary motion, pure linear motion, or helical motion along the same axis, which have definite advantages of integrated structures, high material utilization, and fast response. Therefore, such motors have an extensive application prosperity ranging from robots, electric vessels, electric and hybrid vehicles, screwing machines, drilling machines, and intelligent machining systems. In this paper, an overview of 2DoF RL motors is presented, which can be divided into the motors with crossed RL magnetic field and those with independent RL magnetic fields. The development of various topologies and the corresponding coupling effect, optimization designs, and decoupling control algorithms are discussed and reviewed.

This article describes the development of an exact analytical model for predicting magnetic field distribution within active parts of a dual-rotor (DR) permanent magnet (PM) synchronous machine with a Halbach array. The model is based on the accurate solution of Laplace's and Poisson's partial differential equations (PDEs) using a method of separation of variables. The model also allows the calculation of the DR machine flux linkage, back electromotive force (bEMF), and electromagnetic torque at on load and cogging torque at a no-load condition. The model can be used at the initial stage of designing a DR PM machine for the estimation of electromagnetic parameters and the optimization of machine geometry.

Modular-spoke-type permanent-magnet (MSTPM) machines are novel in-wheel traction machines for electric vehicles (EVs). Considering the strict constraints including the mass and volume of electric machines in EVs, which are heavily dependent on the dissipation condition, an accurate thermal model and resultant temperature distribution analysis are key challenges. Therefore, in this paper, a lumped parameter thermal network (LPTN) model for thermal analysis of MSTPM machines is proposed, where the heat transfer coefficients are determined theoretically instead of empirically, which means that the proposed LPTN model can be applicable for the MSTPM machines with different specifications and parameters. Both the steady-state and transient-state temperature rises are analyzed by the LPTN model, and the results are verified by both 3-D finite element analysis (FEA) predictions and experiments, indicating that the proposed method has advantages in both computational efficiency and accuracy.

A detailed design of a new rotational single sheet tester device which allows comprehensive multiaxial magneto-mechanical analysis of ferromagnetic sheets is proposed. The challenges that arose during the mechanical and magnetic design phases are addressed. The applicability of the device is tested by performing magneto-mechanical measurements on an M400-50A electrical steel sheet. Results under several multiaxial magneto-mechanical loadings with circular and alternating magnetic flux densities are reported. It is shown that the effect of multiaxial stress on iron losses can be much more significant than that of uniaxial stress.

The permanent magnet (PM) machine with consequent-pole (CP) rotor can improve the PM utilization ratio. However, the replacement of the PMs with the same polarity by the salient iron core deteriorate the electromagnetic performance of the machine, including higher torque ripple and unipolar leakage flux. Therefore, a CP PM machine with asymmetric magnetic pole (AMP) structure is proposed, through which the smaller torque ripple and unipolar leakage flux can be obtained, without deteriorating the torque characteristics compared with the traditional CP PM machine. Furthermore, the electromagnetic performance and the unipolar end leakage flux of the AMP and traditional CP PM machines are investigated by the finite-element method (FEM). It is demonstrated that AMP structure can reduce the cogging torque and torque ripple; furthermore, the unipolar leakage flux can be suppressed effectively. Finally, the prototype with AMP and CP PM rotor are fabricated and tested to verify the theoretical and FE analysis.

This paper analyzes the effect of the operation frequency of an inductive charging system on the heat generation and its impact on the overall system efficiency. This is done considering the change of the material properties due to both frequency and temperature changes. The analysis is achieved using FEA modeling software ANSYS workbench. For faster subsequent optimization, an order-reduced model is implemented in a system-level simulation. Various tests show the good agreement of the results between the reduced order model and those of dynamically coupled-field solvers. Our implementation allows for precise calculation of the losses of the different system parts. Furthermore, an experiment has been conducted to validate the simulation results.

In this work, we have investigated the size induced on the viscoelasticity of CoFe2O4magnetic nanofluids (MNFs). The focus of this work is to provide an insight into the effect of varying particle size on viscoelastic properties of CoFe2O4MNFs with varying CoFe2O4nanoparticle sizes. Kerosene-based MNFs containing surfactant coated CoFe2O4were synthesized using standard optimized coprecipitation method, and variations in average mean size ~ 9–30 nm have been synthesized. The physical properties, such as structural and morphology, have been investigated to confirm the purity, and variation in size. Steady-state and oscillatory mode measurements were performed using a magneto-rheometer to investigate the field-induced magneto-rheology. The steady-state rheograms (viscosity vs. shear rate curve) has been well fitted with power-law$\eta =c\dot {\gamma }^{n}+\eta _{\infty }$, confirming the shear thinning behavior with$n\le 1$. Furthermore, magneto-sweep rheograms (viscosity vs. magnetic field) has been used to investigate the steady increase in viscosity, which is due to the formation of…

The loss prediction of magnetic materials under dc bias is of great significance for the optimization of magnetic components, because the efficiency evaluation of magnetic components involves core loss computation under dc bias. Aiming to develop a calculation method for magnetic material losses under dc bias, a novel dynamic energetic hysteresis model combining the statistical theory of losses (STL) with a static energetic hysteresis model is proposed. Firstly, the effects of dc bias on the hysteresis, classical, and excess loss components are analyzed, respectively, using STL. Then, based on the equivalent field separation technique, the magnetic fields corresponding to classical and excess losses are derived using the analytical equations proposed by STL. Finally, a new dynamic energetic hysteresis model, which can take all the hysteresis, classical, and excess losses of magnetic materials under dc bias into account, is devised with the superposition principle. The simulation and experimental results confirmed the accuracy and efficiency of the proposed model.

This paper proposes a multiphase modular fault-tolerant permanent-magnet (PM) machine with hybrid single/double-layer fractional-slot concentrated winding (FSCW). Comparisons between the proposed machine and conventional FSCW machines are made to indicate the special characteristics in aspects of armature magnetomotive force harmonic distribution, cogging torque, magnetic isolation ability, and torque capability. Then, influences of specific structural parameters, including the angle between single-layer slot (SLS) and double-layer slot (DLS) and the opening widths of SLS and DLS, on machine performances are investigated, and power density of the machine is improved by selecting the parameters appropriately. In addition, two stator modular design schemes are proposed. The influences of gaps between modules on machine performances, such as torque, losses, inductances, and short-circuit current, are investigated.