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Appreciation/understanding of the factors that affect proximal coupling in magnetic circuits and the manifestations of the effect of coupling due to magnetic proximity are of paramount importance in electrical engineering. In this paper and in another companion paper we endeavor dealing with each of the aspects critically and putting them in one place. Mainly three aspects—factors that affect the coefficient of coupling, expressing the coefficient of coupling in terms of the design parameters—thus showing the symmetry of the inductance matrix, and the factors that contribute to the deviation of the voltage/current ratios from turns‐ratio is considered, with the introduction of a new factor—a measure of (a)symmetry between the magnetic paths seen by the associated coils. It is also attempted to counter the wide‐spread myth that the proximal coupling imperfection is because of the air‐medium and to highlight the fact that it can also arise because of and be controlled by providing controlled magnetic shunting between the associated coils—a very useful insight. © 2024 Institute of Electrical Engineers of Japan and Wiley Periodicals LLC. [ABSTRACT FROM AUTHOR]

This paper investigates two studies on the magnetic circuit model incorporating the play model. First, the calculation speed of several general‐purpose circuit simulators is compared when analyzing the magnetic circuit model incorporating the play model. Second, the calculation accuracy and speed of the two modeling methods of the play model on a general‐purpose circuit simulator are compared. © 2024 Institute of Electrical Engineers of Japan. Published by Wiley Periodicals LLC. [ABSTRACT FROM AUTHOR]

In‐vacuum undulators (IVUs), which have become an essential tool in synchrotron radiation facilities, have two technical challenges toward further advancement: one is a strong attractive force between top and bottom magnetic arrays, and the other is a stringent requirement on magnetic materials to avoid demagnetization. The former imposes a complicated design on mechanical and vacuum structures, while the latter limits the possibility of using high‐performance permanent magnets. To solve these issues, a number of technical developments have been made, such as force cancellation and modularization of magnetic arrays, and enhancement of resistance against demagnetization by means of a special magnetic circuit. The performance of a new IVU built upon these technologies has revealed their effectiveness for constructing high‐performance IVUs in a cost‐effective manner. [ABSTRACT FROM AUTHOR]

In view of the problem of large torque ripple and poor output performance of permanent magnet synchronous motor, a new topology of asymmetric magnetic pole permanent magnet synchronous motor is proposed, and the torque ripple of this motor structure and the suppression method are analyzed. First, the equivalent magnetic circuit method and Lorentz force law are used to derive the analytical formula of torque ripple of the motor. Then, based on the analytical formula, the parameters of permanent magnet of the asymmetric magnetic pole permanent magnet synchronous motor are optimized and verified by finite element software simulation; on this basis, the method of rotor eccentricity is used to further weaken the torque ripple of the motor, and the optimal eccentricity distance is analyzed. The research shows that when the parameters of the magnetic pole of the asymmetric magnetic pole permanent magnet synchronous motor is appropriate, the harmonic content of the air gap magnetic density of the optimized motor is greatly reduced, and the motor has good output characteristics, and the torque ripple is reduced to 5.4%. Finally, the prototype is trial‐manufactured and tested. The results show that after optimization, the cogging torque of the motor is reduced, the torque output performance is improved, and the overall motor performance is improved. © 2024 Institute of Electrical Engineers of Japan and Wiley Periodicals LLC. [ABSTRACT FROM AUTHOR]

Accurate calculation of equivalent circuit parameters is a prerequisite for accurately calculating the large‐capacity synchronous condenser parameter model. Due to its special transient operating conditions, the high transient magnetic saturation effect during operation causes the non‐linearity and time‐varying of the equivalent circuit parameters. The field mutual leakage reactance is the critical factor affecting the field current, and the time‐varying of the equivalent circuit parameters is closely related to the field current. However, the existing equivalent circuit parameter calculation methods considering field leakage reactance cannot achieve time‐varying parameters. A calculation method of time‐varying equivalent circuit parameters based on a back propagation neural network algorithm is proposed, which solves the calculation problem of time‐varying equivalent circuit parameters considering field mutual leakage reactance. Then, a 300MVar condenser is taken as the research object, and the proposed method is used to simulate the different operating conditions of the condenser and verified by the finite element method and experiment. The results show that the method improves the calculation accuracy of the equivalent circuit parameter model, reduces the calculation time, and applies to different operating conditions. [ABSTRACT FROM AUTHOR]

Magnetic resonance imaging (MRI) is widely used in clinical care and medical research. The signal‐to‐noise ratio (SNR) in the measurement affects parameters that determine the diagnostic value of the image, such as the spatial resolution, contrast, and scan time. Surgically implanted radiofrequency coils can increase SNR of subsequent MRI studies of adjacent tissues. The resulting benefits in SNR are, however, balanced by significant risks associated with surgically removing these coils or with leaving them in place permanently. As an alternative, here the authors report classes of implantable inductor–capacitor circuits made entirely of bioresorbable organic and inorganic materials. Engineering choices for the designs of an inductor and a capacitor provide the ability to select the resonant frequency of the devices to meet MRI specifications (e.g., 200 MHz at 4.7 T MRI). Such devices enhance the SNR and improve the associated imaging capabilities. These simple, small bioelectronic systems function over clinically relevant time frames (up to 1 month) at physiological conditions and then disappear completely by natural mechanisms of bioresorption, thereby eliminating the need for surgical extraction. Imaging demonstrations in a nerve phantom and a human cadaver suggest that this technology has broad potential for post‐surgical monitoring/evaluation of recovery processes. [ABSTRACT FROM AUTHOR]

Summary The aim of this paper is to present a methodology for solving а dynamic electric circuit with nonlinear hysteretic inductor without the use of hysteresis model or equivalent circuits. A consideration of nonlinear and hysteretic behaviour of the magnetic core under quasistatic conditions is based on applying harmonics interpolation method (HIM) to the measured magnetising field strength waveforms. A dynamic behaviour of the magnetic core is considered through the application of the statistical theory of losses (STL). A considered electric circuit consists of AC voltage source connected in series with shunt resistor, additional linear resistor and inductor, as well as a nonlinear hysteretic inductor. The solution for electric current of the circuit is obtained by solving equation derived from Kirchhoff's laws through a series of successive iterations. Coupling of electric and magnetic part of the circuit is obtained from fundamental laws of electromagnetism. Methodology is validated for four cases of the considered electric circuit — without additional elements, with one additional or both additional elements, for sinusoidal voltage source amplitudes of 2, 4, 6, 8 and 9 V and frequency of 50 Hz. Validation is repeated for frequencies of 100, 200 and 300 Hz while keeping the ratio of the amplitude to frequency constant. Detailed theoretical approach and methodology, comparisons between measured and calculated results, as well as adequate discussion are presented. [ABSTRACT FROM AUTHOR]

To improve the speed of mass transfer, a magnetic suspension platform (MSP) is used to transport the display chips. A novel 6‐DOF MSP is proposed in this paper. An improved Halbach array is used to supply the magnetic flux density. Two types of permanent magnets are utilised in the improved Halbach array. The smaller permanent magnet serves to consolidate the magnetic flux density, thereby enhancing the uniformity of the magnetic field. The finite element method is employed to analyse how variations in angle impact both the strength and uniformity of the magnetic flux density. The results show that the magnetisation direction of 45° is the most effective in terms of improving the uniformity and strength of the magnetic density. Finally, a 6‐DOF MSP prototype is manufactured. A magnetic density measurement experiment and a stable suspension experiment for the actuator are conducted. The results indicate an enhancement in the uniformity of the magnetic field within the air gap. Additionally, the maximum suspension positioning accuracy of the actuator is about 750 nm. [ABSTRACT FROM AUTHOR]

To facilitate the regulation of the air‐gap magnetic field of permanent magnet synchronous machines, a novel topology of a high‐speed hybrid excitation synchronous machine (HESM) was presented. The electromagnetic performance of the proposed HESM was evaluated. The air‐gap magnetic field regulation principle was introduced first. Then, a mathematical model of the HESM was established. Based on the characteristics of a 3D magnetic circuit, the HESM equalled three types of 2D magnetic circuit machines in axial parallel superposition, and thus the expressions of inductance parameters were deduced. Subsequently, the voltage regulation performance of the HESM was assessed according to the mathematical model and inductance parameters. The loss and efficiency were calculated. Finally, a HESM prototype was tested and verified. [ABSTRACT FROM AUTHOR]

The permanent magnet eddy‐current coupler (PMEC) is a kind of non‐contact, stepless speed regulation device and has been widely used in transmissions. However, the current PMECs are coaxial and cannot achieve transmission and speed regulation in intersecting axes. An intersecting‐axis permanent magnet (PM) eddy current coupler (IPMEC), which consists of a disk‐type PM rotor and a barrel‐type conductive sheet (CS) rotor arranged with intersecting axes, is proposed. It generates eddy currents through the speed difference between the two rotors and uses the non‐contact electromagnetic force between the eddy currents and permanent magnets to transmit torque. During operation, the speed can be adjusted by altering the coupling area or air gap. A theoretical model of the IPMEC based on the equivalent magnetic circuit method is presented and verified by finite element simulation using ANSYS. Then, the effects of the pole number of the PMs, the radius of the CS rotor and the PM rotor on the performance were analysed, and the design method of the IPMEC was proposed. This study can be used to expand the application range of PMECs. [ABSTRACT FROM AUTHOR]

The axial flux permanent magnet (AFPM) machines with the parallel magnetic circuit (PMC) rotor can effectively improve its torque density. The PMC rotor consists of two sub‐rotors, radial Halbach array permanent magnet (PM) and tangential PM. The magnetic fields generated by two sub‐rotors are not in the same 2‐D analytical planes. In this paper, an equivalent analytical model of PMC‐AFPM machines is proposed to solve this problem. The radial Halbach array PM rotor is equated to the axial Halbach array PM rotor based on the equivalent transformation principle. The exact subdomain models of equivalent axial Halbach array PM rotor and tangential PM rotor are built respectively and then superimposed to obtain the magnetic field distribution. The electromagnetic characteristics of the PMC‐AFPM machine under no‐load and load conditions are calculated by the proposed analytical model and compared with calculations of the finite element model (FEM). The results verify the accuracy of the equivalent analytical model. The comparative analysis of the AFPM machines with PMC rotor and tangential PM rotor verifies the advantage of PMC rotor configuration to improve the torque density. © 2024 Institute of Electrical Engineer of Japan and Wiley Periodicals LLC. [ABSTRACT FROM AUTHOR]

In the field of electric aircraft, the axial force of the conical motor is used to offset propeller thrust and reduce bearing wear. For the problem of accurate calculation of the no‐load axial force of the conical motor, combined with the characteristics that the rotor magnetic bridge of the hybrid conical inner‐mounted permanent magnet synchronous motor (HC‐IPMSM) is easy to be saturated and difficult to be calculated analytically, an equivalent analytical calculation method is proposed. According to the principle of constant air‐gap magnetic flux, the HC‐IPMSM is equivalent to many cylindrical surface‐mounted permanent magnet synchronous motors (CY‐SPMSM), and an analytical model is gained. Combining with the scalar magnetic potential Laplace equation and Poisson equation, the air‐gap flux density distribution on the rotor surface is calculated. And finally, the no‐load axial force of the motor is obtained by using the cone angle and the Maxwell stress method. Simulation and experiments verify the correctness and validity of the analytical model. [ABSTRACT FROM AUTHOR]

Summary: The energy coupling behavior is propagated through the magnetic field and would seriously affect the operation performance of two‐degree‐of‐freedom motion system based on linear‐rotary motor. This paper proposes a novel double‐stator linear‐rotary switched reluctance motor (DSLR‐SRM) to suppress the energy coupling behavior. First, the structure and operation principles of DSLR‐SRM are presented. The two stators of DSLR‐SRM are radially arranged to perform the independent magnetic circuit and suppress the energy coupling behavior through the magnetic field. Then, an equivalent circuit model is established to shorten the modeling and calculation time. It could be found that the energy coupling behavior directly affects the torque and force performance. Next, the sensitivity of the DSLR‐SRM dimensions is developed. Meanwhile, the dimensions of DSLR‐SRM are optimized to enhance the torque and force output via TOPSIS decision‐making. Finally, the validity of equivalent circuit modeling analysis and optimization results are verified through three‐dimensional finite element model. [ABSTRACT FROM AUTHOR]

Several types of fault current limiters have been studied so far, including superconductor based one or nonsuperconductor based one. However, it is difficult to satisfy all requirements for cost, maintainability, and current limiting performance. This study proposes another type of fault current limiter, variable transformer based one. It is supposed to be less expensive and easier to be maintained since it is based on the conventional transformer, and to be expected better current limiting performance since the magnetic circuit of the transformer is drastically changed. The magnetic circuit of the transformer is switched to be opened and to produce another one by shifting a portion of its iron core mechanically, allowing the primary and secondary electric circuit to be magnetically isolated. In that way, the electromotive force of the secondary winding could be reduced so that the secondary current could be limited. The prototype based on this concept was designed and built up, and its stational performance has been investigated. As a result, it was confirmed that the prototype shows good current limiting performances identical to the results of the previous FE analysis. Furthermore, the prototype was connected to the operating mechanism to investigate the transient performances, and as a result, satisfying current limiting performances are confirmed [ABSTRACT FROM AUTHOR]

Harmonic magnetic gears (HMGs) have the advantage of lubrication‐free, high speed ratio and high torque density, which make it an attractive solution for safety critical applications. Due to eccentricity caused by machining and assembly, HMG suffers from dynamic eccentricity (DE) in operation, however, its effect on HMG performance is still unknown. Transmission characteristic of HMG under DE is studied. First, a magnetic equivalent circuit (MEC) model of HMG is proposed to build the magnetic coupling torque analytically, and the geometry of air gap is analysed parametrically to derive its equivalent reluctances. Flux density and coupling torque can be acquired by solving MEC equations. The accuracy of the MEC model is verified by finite element method. To study the transmission characteristic, an electromechanical coupling simulation framework for HMG is constructed, motion trajectories of rotors are investigated in case of DE, the output torque in locked‐rotor condition and speed response in continuous operation can be derived by simulation. It is found that torque ripples that have the same frequency with input rotor are induced by DE; the results are then verified in the experiment. This paper provides a theoretical guidance for the design and condition monitoring of HMG. [ABSTRACT FROM AUTHOR]

A modified non‐linear magnetic equivalent circuit (MEC) model is presented for double‐stator single‐rotor axial flux permanent magnet (AFPM) (DSSR‐AFPM) machine considering stator radial‐end flux‐leakage, which is severer under a heavier load. Compared to the conventional MEC model for DSSR‐AFPM machine, the proposed model can predict the electromagnetic performance more accurately when the machine operates under a heavy load. The proposed MEC model is verified by the finite element analysis (FEA) on a 24‐slot/20‐pole DSSR‐AFPM machine. The comparison results show that the relative error between the proposed MEC model and FEA is <4% for back electromotive force and <5% for average electromagnetic torque, respectively. Specifically, the relative error of the average torque for the modified MEC model is 4.92% at 28.30 Arms/mm2 slot current density, which is lower than the conventional MEC model, that is, 7.75%. [ABSTRACT FROM AUTHOR]

The isolated DC/DC converter plays an irreplaceable role in the development of the DC microgrid. However, the multiple discrete high‐frequency transformers occupy considerable volume in power converters due to the connection of multiple isolated converters. In order to reduce the number of discrete transformers and increase the power density as well as the reliability of the power converter, a three‐port isolated DC/DC converter with a decoupling magnetic integrated high‐frequency transformer (DMIHFT) is proposed for the DC microgrid in this paper. The semiconductor count of the proposed converter is reduced by combining one DAB converter and two LLC converters. Three discrete transformers are integrated into a single common core, and magnetic decoupling is achieved among each transformer by rational design at the same time. In addition, the magnetic circuit model derivation process of the proposed DMIHFT and the operation principles of the converter are described in detail. The design guidance of the proposed DMIHFT is present. And then, a 15 kW/20 kHz DMIHFT is designed based on the design guideline, and the simulation is carried out. Finally, a 15 kW/20 kHz DMIHFT prototype is fabricated, and the effectiveness of the proposed DMIHFT is verified by experimental results. [ABSTRACT FROM AUTHOR]

The aim of this article is to develop a rotor reconstruction method for the V‐shaped interior permanent magnet (IPM) machine so that the subdomain method to analytically calculate the air‐gap flux density can be applied. With the proposed method, the V‐shaped IPM rotor with rectangular magnets, magnetic barriers, and saturated iron bridges can be transformed into a U‐shaped equivalent analytical model. The geometry and material parameters of the magnets in the equivalent U‐shaped model can be determined according to the flux equivalence in the air‐gap of the motor. Then using the subdomain method on the U‐shaped equivalent rotor, the static magnetic field problem can be solved and the flux density distribution in the air‐gap be obtained. The validity of this method and accuracy of the solution is verified by the finite element method with case studies. Compared with existing methods, the improved subdomain method has higher accuracy in calculating flux density including radial and tangential components. The presented rotor reconstruction method is not only limited to single‐layer V‐shaped rotor, it can also be applied to other IPM rotors with more complex structures. It is valuable in the design, optimisation of IPM motors, and even development of new rotor topology. [ABSTRACT FROM AUTHOR]

A backstepping controller based on a non‐linear disturbance observer (NDOB) was created to enhance the dynamic performance and reliability of three‐degree‐of‐freedom hybrid magnetic bearings. After the structure of three‐degree‐of‐freedom hybrid magnetic bearings is introduced, the mathematical model is established, and the equation of the state is derived by the equivalent magnetic circuit technique. Based on the mathematical model, non‐linear disturbance observer (NDOB) is designed and is used to predict the system disturbance, and the backstepping control algorithm is compensated. To verify the effectiveness of the proposed controller, the backstepping controller, proportion integration differentiation controller, and backstepping controller based on a NDOB were compared by simulation and experiment. Results show that the backstepping controller based on a NDOB has better dynamic performance and robustness. [ABSTRACT FROM AUTHOR]

In order to solve the problems of complex structure and the difficulty of neutral adjustment of the existing 2D valve electro‐mechanical converter, a kind of claw pole magnetic levitation torque motor (CPMLTM) was proposed, which automatically suspended the rotor in an axially and circumferentially neutral position by using the cogging torque and axial recovery forces between the stator claw pole and the rotor permanent magnet (PM). Compared with the conventional moving iron torque motor, it has positive magnetic stiffness, 1.54 times higher PM utilisation and 33.6% lower mass. A qualitative mathematical model of output torque is derived based on equivalent magnetic circuit model. Then, the response surface method was used to build the second‐order response surface model, and NSGA‐2 was used to optimise the design of five key structural parameters, and the non‐inferior solution sets satisfying the maximisation of the cogging torque, output torque and axial recovery force were obtained. The experimental prototype was developed, and static experiments were carried out on the experimental rigs. The results show that the relationship between the input current and the output angular displacement of the CPMLTM is linearly proportional when the magnetomotive force generated by the coil winding is from −50 to 50 A. [ABSTRACT FROM AUTHOR]

This paper investigates the influence of the loss distribution and magnetic saturation on the efficiency performance, which includes the location of maximum efficiency point, the size of high‐efficiency region and the value of maximum efficiency, for an interior permanent magnet synchronous motor (IPMSM). The loss expressions considering magnetic saturation are first proposed and then the efficiency‐losses function model of the IPMSM is constructed. The efficiency performance of the motor is analyzed quantitatively. The general principle is summarized including adjusting the location of maximum efficiency point, expanding the size of high‐efficiency zone and improving the maximum value of efficiency from the perspective of loss distribution and magnetic saturation. Two IPMSMs with different magnetic circuit characteristics are designed to verify the correctness of the analytical method by finite‐element analysis (FEA). Finally, prototypes are manufactured for the experiment and measurement results are given for validations. © 2023 Institute of Electrical Engineer of Japan and Wiley Periodicals LLC. [ABSTRACT FROM AUTHOR]

To solve the problems mechanically caused by parallel direct‐drive permanent magnet motors (DD‐PMSM). This paper proposes a concave‐core stator direct‐drive permanent magnet motor (CCSDD‐PMSM) structure. In this study, an auxiliary yoke structure is proposed to optimise the magnetic circuit and analyse the cogging torque to achieve the minimum detent force. Based on the unit motor and combined with the magnetomotive force to analyse the symmetry of different winding distributions, the stability characteristics of the motor are studied. The magnetic field distribution of the motor load air gap is calculated using the finite element method. The contribution of different spatial order harmonics to the motor output torque is calculated using the Maxwell tensor method. The torque calculation expression of the CCSDD‐PMSM is given. Finally, an experimental prototype is made to verify the accuracy of the analysis in this paper. [ABSTRACT FROM AUTHOR]

The present work proposes an innovative method to form microgrooves on a tube's internal surface through new machining based on the principle of the closed magnetic circuit. A newly designed machine with a magnetic grooving tool was fabricated. The tool consists of a pair of magnets positioned in the pipe to be pulled by another pairing magnet set at the pipe's external side, arranged in sequence of N−S−N−S direction so that it creates a closed magnetic field that has a greater pulling force. By controlling the magnet pair at the pipe's external side in the linear and rotational direction, the magnetic grooving tool is moved in both directions and simultaneously pulled towards the pipe surface to form the microgrooves. The experiment was carried out by adjusting the magnet's size combination and its distance to vary the magnetic strengths. The grooving dimension was examined by using an optical microscope and analysed using a 3‐dimensional laser profilometer surface analyser. With N52 class Nd2Fe12B neodymium (40×10×10 mm3), the maximum groove depth of 75.51 μm was recorded and the minimum depth of 2.33 μm was recorded by using magnet size 10×10×10 mm3. The method is capable to produce microgrooves on the copper pipe's internal surface. [ABSTRACT FROM AUTHOR]

Because the magnetic circuits of homopolar inductor machines (HIMs) are three‐dimensional (3‐D), a 3‐D finite element model (FEM) is usually built to accurately compute the cogging torque in HIMs, but the drawback is very time‐consuming in modeling and computing. Therefore, a two‐dimensional (2‐D) FEM of HIMs is needed to simplify the computation of the 3‐D FEM. However, the existing odd harmonic 2‐D FEM cannot accurately predict the cogging torque in HIMs. To address this problem, this paper proposes a full‐order harmonic 2‐D FEM. First, the analytical expressions of HIM cogging torque are derived by the combination of energy method and air‐gap field modulation principle. Based on the obtained analytical expressions, the equivalent principles between the 3‐D and 2‐D FEMs are analyzed. According to the above equivalent principles and taking a 48‐slot/4‐tooth (48S4T) permanent magnet (PM) HIM as an example, a full‐order harmonic 2‐D FEM of the example machine excited by a field winding is proposed. The structure of the full‐order harmonic 2‐D FEM is described in detail. The turn number of field winding and field current amplitude of the proposed 2‐D FEM are investigated. The differences between the odd harmonic 2‐D and full‐order harmonic 2‐D FEMs are also analyzed. Finally, the cogging torque in the 48S4T PM HIM with distinct rotor tooth‐arc to tooth‐pitch ratios is computed by 3‐D, odd harmonic 2‐D and full‐order harmonic 2‐D FEMs of the machine, respectively. The results illustrate that compared with the odd harmonic 2‐D FEM, the full‐order harmonic 2‐D FEM can shorten the calculation time and has the similar computation accuracy as the 3‐D FEM. Moreover, the experimental validation is performed on a prototype of the 48S4T PM HIM. The error between the maximum cogging torque obtained by the full‐order harmonic 2‐D FEM and experiments is only 2.12%. © 2023 Institute of Electrical Engineer of Japan and Wiley Periodicals LLC. [ABSTRACT FROM AUTHOR]

Shunt reactor with auxiliary windings (SRAW) can compensate inductive reactive power for long‐distance transmission lines and supply steady power for low‐voltage devices on offshore platforms. The operation characteristics of SRAW can be commonly described by the air‐core transformer equivalent model. However, this model can only make an approximate simulation of the external characteristics of SRAW, and cannot reflect the actual electrical features inside the SRAW. To solve this problem, the authors propose a three‐segment magnetic circuit equivalent model (TMCEM) of SRAW based on the magnetic circuit decomposition method. This model can accurately describe the coupling relationship inside SRAW and can be used for the analysis of internal fault characteristics. Furthermore, through the fault analysis utilizing TMCEM, a novel protection scheme of SRAW based on virtual magnetizing differential current is proposed for the detection of the inner‐turn fault in SRAW. This protection scheme has high sensitivity and can effectively identify the inner‐turn faults without measuring voltages. By testing the physical model of SRAW, the effectiveness of the TMCEM and the proposed protection scheme against inner‐turn fault has been confirmed. [ABSTRACT FROM AUTHOR]

Switched reluctance machines offer a robust structure, inexpensive maintenance, and a low‐cost drive. However, they can suffer from low mean torque, low torque density, and high noise. Techniques such as offering the stator poles at each phase in the shape of a C core, adding several teeth to the two poles of each C‐core, and embedding permanent magnets to overcome these deficiencies are presented. Permanent magnets are embedded into the structure to create a hybrid excitation that provides a higher torque density. The C‐core stator modules of the stator are toothed to improve the torque. The radial forces on the shaft are balanced. The design procedure, operating principles, and performance trade‐offs are explained. Also, a magnetic equivalent circuit model is introduced. The model provides continuous relationships over the operating regions and incorporates core saturation and accurate flux tubes to attain high precision. Finite element models are also employed in the analysis and design process. The motor is prototyped, and experimental results are extracted, closely matching those obtained with the model and finite‐element analysis. [ABSTRACT FROM AUTHOR]

A computationally efficient time‐harmonic finite element model for the steady‐state analysis of a brushless doubly fed induction machine (BDFIM) is proposed. In the model, the electromagnetic couplings of the BDFIM are described by means of the sum of two complex magnetic vector potentials that represent the two fundamental harmonic time components of the magnetic flux density distribution in the rotor frame of reference. As in an ordinary induction motor, the non‐linearity of the magnetisation characteristic is accounted for using an effective magnetic permeability. For the BDFIM, this is derived by considering the features of modulated magnetic flux density waveform. The accuracy of the approach has been validated by comparing the characteristics of a D270 machine operating in the double‐feed mode with ones obtained from the experimentally verified time‐stepping model at various operating conditions. High accuracy of the results coming from the proposed model is demonstrated even under deep saturation conditions within the magnetic circuit. [ABSTRACT FROM AUTHOR]

The dual‐stator permanent magnet (PM) machine has the advantages of high torque density, high efficiency, and compact size, which makes it suitable for low‐speed high‐torque applications. A dual‐stator low‐speed high‐torque permanent magnet drive machine (DLHPMDM) is discussed and studied in this paper, which is applied to the ball mill application. First, in order to meet the requirements of high efficiency and high reliability, a DLHPMDM with the inner and outer windings connected in parallel is obtained through the designs carried out in terms of the magnetic circuit structure, structural size, and the pole‐slot number combination. However, for the DLHPMDM with the inner and outer windings connected in parallel, the power allocation between the inner and outer machines is a critical problem that needs to be accurately analyzed, and the circulating current between the two sets of windings is also a particular issue that merit attention. Therefore, a new modeling method is proposed for the DLHPMDM to solve such cases more accurately. The proposed new method combines the advantages of the rapidity of the finite element analysis (FEA) with current excitations and the accuracy of the FEA with voltage excitations. Finally, a prototype of the DLHPMDM is manufactured and tested. The feasibility of the design theory and the validity of the proposed modeling method is verified by both the tested and simulated results. © 2023 Institute of Electrical Engineer of Japan and Wiley Periodicals LLC. [ABSTRACT FROM AUTHOR]

Neurophysiological evidence that transcutaneous auricular vagal nerve stimulation (taVNS) affects neuronal signalling at the cortical level is sparse. We used transcranial magnetic stimulation to assess the effect of taVNS on the excitability of intracortical GABAergic and cholinergic circuits. In this within‐subject, double‐blind study on 30 healthy participants, we used TMS paradigms to assess the effect of a single session of taVNS at 100 Hz and sham earlobe VNS (sVNS) on short‐interval intracortical inhibition (SICI) curve and short‐latency afferent inhibition (SAI). Control experiment was performed on additional 15 participants using the same experimental settings, but delivering no stimulation (xVNS). Bayesian statistics were used to assess the differences, producing % values that reflect the certainty that the values of interest were decreased during or after stimulation compared with baseline. taVNS increased SICI (96.3%), whereas sVNS decreased SICI (1.2%). SAI was not affected by taVNS, although it was decreased during sVNS (1.34% and 9.1%, for interstimulus intervals 20 and 24 ms, respectively). The changes in TMS parameters detected during sVNS were present in the same direction in the control experiment with no stimulation. Our study provides evidence that taVNS increases the activity of cortical GABAAergic system, leaving cortical cholinergic circuits unaffected. Changes in intracortical cortical excitability during sVNS, which were also observed in the control experiment with no stimulation were likely the effect of expectation related to participation in an interventional study. [ABSTRACT FROM AUTHOR]

Here, a modified magnetic equivalent circuit model which can accurately consider the air‐gap region is presented. The main defect of magnetic equivalent circuit model is in the modelling of air‐gap region. To solve this problem, a new approach based on conformal mappings is presented to accurately calculate the air‐gap permeances between the elements of stator and rotor while considering the real paths of flux tubes in air gap. The distributions of equivalent virtual currents on the both sides of air gap are obtained through modified magnetic equivalent circuit model, which represent the effects of slots, magneto motive force drops in iron parts, and magneto motive force sources. The conformal mapping method is then used to calculate the components of air‐gap magnetic field for every operating point under starting conditions and different loads. One typical cage‐rotor induction motor, which is used in electric submersible pumps, is considered to investigate the accuracy of modified magnetic equivalent circuit model. Some of the analytical results obtained through modified magnetic equivalent circuit model are verified by comparing with the corresponding results obtained from finite element method and experiment set up. [ABSTRACT FROM AUTHOR]

In order to solve the problem of the decreasing torque density caused by the complex structure of the hybrid excitation machine, a novel flux–torque regulation hybrid excitation machine with axial–radial magnetic circuit is proposed by the authors, which innovatively realises the increase of additional torque and the regulation of the magnetic field by an axial structure. In particular, the additional torque has a certain boost to the output torque under the flux‐weakening condition of the machine. Based on the equivalent magnetic network model, the flux regulation principle of the machine is analysed, and the expressions for the flux linkage and no‐load back electro‐motive force are given to obtain the important factors affecting the flux regulation. Based on the analysis of complex forces generated by the rotating permanent magnet in the coupling magnetic fields, the generation and control principle of the additional torque is expounded. The expression of the additional torque is derived by the Maxwell stress tensor method, which can determine the main influencing factors and these relationships. Finally, the rationality of the proposed hybrid excitation machine structure is verified by experiments. [ABSTRACT FROM AUTHOR]

Here, the authors propose two new Permanent Magnet (PM) embedded linear switched reluctance motors; one is a modular linear hybrid reluctance motor (MLHRM), and the other one is a segmental linear hybrid reluctance motor (SLHRM). Both structures employ PMs between the side teeth of the modules/segments. The main contribution of the PMs is to increase the air‐gap flux density, which results in an enhanced thrust, and decrease the magnetic saturation in iron parts. The magnetic equivalent circuit model is used to demonstrate the positive effect of inserting PMs in the MLHRM and SLHRM compared to their PMless counterparts. The optimal pole number and design procedure are illustrated. The simulation results are obtained in terms of static thrust, flux linkage, flux density distributions, and steady‐state current and thrust. The results show that the proposed MLHRM and SLHRM offer a higher thrust and lower current compared to their PMless form. Also, the PMs decrease the root mean square (RMS) current under the steady‐state performance of the motors, in which a higher thrust is produced with a lower RMS current. Finally, the MLHRM and SLHRM are fabricated and the test results are obtained and compared with the simulations, which illustrate a satisfactory agreement. [ABSTRACT FROM AUTHOR]

Axial flux motors have been in the focus of many research work due to their promising properties when compared to conventional radial flux machines. Axial flux permanent magnet synchronous motors (AFPMSM) studied in the literature were mostly limited to surface‐mounted permanent magnet machines (SPMSM), excluding only a few studies about axial flux internal permanent magnet (AFIPM) or permanent magnet‐assisted synchronous reluctance (AFPMaSynRM) machines. Since numerous rotor topologies have been proposed and investigated in case of radial flux motors, analogous design methodologies can be developed in case of axial flux motors with rotor saliency. The parametrisation and modelling of a magnetically anisotropic rotor axial flux motor are presented. This approach is described generally and the method is applied to an example motor geometry. The results were validated by FEA (Finite Element Analysis), using the 2D multi‐slice and 3D modelling approaches. The modelling error was calculated and the analytical and numerical methods were compared. It was found that the proposed model was suitable for calculating important parameters of the anisotropic rotor axial flux permanent magnet synchronous motor (AnR‐AFPMSM) during the design process. [ABSTRACT FROM AUTHOR]

This study elaborates upon a new modular split‐tooth permanent magnet‐assisted switched reluctance motor (MSTPM‐SRM). In the proposed topology, the stator comprises six modular E‐cores in which the middle poles are split into two teeth. Two permanent magnets (PMs) are placed between each module's middle and side poles. Primarily, the proposed topology is introduced. Next, the principle of operation of the proposed topology are elucidated, and the magnetic equivalent circuit analysis is adopted in order to validate the operational basics. It is proved that the embedded PMs significantly increase the air‐gap's flux density and adjusts the poles' flux density. The flux density distributions, static, and steady‐state characteristics of the proposed MSTPM‐SRM motor and its PMless counterpart are extracted by utilising 2‐D finite element analysis. It is illustrated that the average torque of the proposed MSTPM‐SRM is dramatically increased compared to its PMless counterpart, especially at high excitation currents. Furthermore, the cogging torque analysis is done and it is shown that the proposed structure has approximately zero cogging torque. Finally, a prototyping version of the proposed motor is fabricated, and the experimental results are elicited. It is shown that the experimental results endorse the simulation results. [ABSTRACT FROM AUTHOR]

This article proposes an equivalent magnetic network (EMN) model to improve the accuracy of electromagnetic analysis, where a modular modelling of hybrid cross‐shaped mesh (CS‐M) elements is introduced. By applying hybrid CS‐M elements, the modelling of air gap and its surrounding regions is regulated into an identical width. As a result, the relative motion of the motor is simpler to simulate by changing the nodal connection without involving the non‐linear permeance. The airgap flux density is solved more accurately than the regular CS‐M elements as well. A 12‐slot/10‐pole ferrite permanent magnet (FPM) motor with assisted poles of unequal pole‐arc ratios is selected as an example to be built with the proposed EMN model. After solving the EMN model, the effectiveness and accuracy of the proposed EMN model are verified by comparing it with the FEA model and experiments. Additionally, based on the frozen permeability (FP) method, transient torque components can be separated accurately with a transient torque solution related to virtual work principle (VWP) for the EMN model. [ABSTRACT FROM AUTHOR]

Wind energy as the cleanest source of renewable energy requires a highly efficient lightweight generator that provides maximum power density while having the least vibration noise and maintenance. In this study, an axial air gap transverse flux machine is presented, and all excitation sources are located in the stator. This structure provides lower core loss, weight and cost due to the full utilisation of the permanent magnets, SMC‐free structure and short magnetic flux path. In fact, by combining the features of a flux‐switching machine into a transverse flux generator with an axial air gap, it is possible to improve the performance of a direct‐drive wind turbine generator by overcoming traditional structures' challenges. To analyse the axial transverse flux switching permanent magnet generator performance characteristics, 3D finite element simulations have been performed, which have been validated by comparing them to the practical results of a single‐phase prototype. The results are in agreement with an acceptable error that is caused by manufacturing uncertainties. [ABSTRACT FROM AUTHOR]

Compared with the traditional permanent magnet synchronous motor (PMSM), the double‐stator permanent magnet synchronous motor (DS‐PMSM) can utilise the internal space adequately and has high power density. In this study, the design method of this kind of motor will be researched. Different rotor magnetic circuit topologies are analysed while keeping the outer diameter of outer stator unchanged, and the rotor magnetic circuit topologies with higher power density are selected. Furthermore, the effects of pole‐arc coefficient and stator split ratio on the power density of the motor are analysed, so a high power density DS‐PMSM can be designed. On this basis, a kind of magnetic pole structure with unequal pole‐arc coefficient is proposed to solve the problem of large torque ripple in DS‐PMSM. Finally, the DS‐PMSM is investigated by the FEA, compared with the traditional single stator PMSM, the average torque of the DS‐PMSM is increased by 62.2%, and the torque ripple is only 3.2%. [ABSTRACT FROM AUTHOR]

In this paper, a novel doubly salient PM motor based on parallel path magnetic technology (PPMT) is presented. PPMT is an advanced magnetic control technology, which can be applied to linear and rotary actuators. First, the fundamental principle of the PPMT prototype is elaborated, and then a comprehensive research and analysis of PPMT motor is carried out, with particular emphasis on machine topology, operation principle and electromagnetic performance. The equivalent no‐load PM magnetic circuit model is established and equations for calculating the main PM flux are derived. Besides, a dual‐stator 6‐pole PPMT motor prototype has been developed to valid the analysis. According to the similarity of topology and operation principle, comparison between the FSPM machine and PPMT machine is conducted, which leads to the conclusion that the PPMT motor has lower cogging torque, lower torque ripple and better sine back EMF waveform, the PPMT motor is more suitable for servo applications compared to FSPM motor. Finally, to improve the power density of PPMT motor, FE parametric modeling method for designing the three coupled stator parameters, which are the PM width, the stator yoke width and the second airgap length is given out. © 2023 Institute of Electrical Engineers of Japan. Published by Wiley Periodicals LLC. [ABSTRACT FROM AUTHOR]

This study investigates the effects of rotor magnetic isolation dimensions on the no‐load performance of ultra‐low speed high torque spoke type permanent magnet motor. The studied spoke type permanent magnet motor structures are shown, where the rotor magnetic isolation parts include a magnetic barrier near the air gap (MB‐NAG), a magnetic barrier near the magnetic isolation sleeve (MB‐NMIS), a magnetic isolation sleeve (MIS). The magnetic circuit model is performed and the finite element analysis method is used to analyse the no‐load performance. Through analysing no‐load performance with three MB‐NAG shapes, the way to narrow the optimise dimension range considering reducing the cogging torque and increasing the back‐EMF synchronously is concluded. The results with different MB‐NMIS and MIS dimensions show that: (a) the optimised MB‐NMIS dimensions can increase the back‐EMF with a thin MIS in a certain dimension range of MB‐NMIS, and (b) the increasing proportion of back‐EMF influenced by the MB‐NMIS is inversely proportional to the thickness of MIS. The feasibility and effectiveness of the proposed motor structure and conclusion are experimentally verified. [ABSTRACT FROM AUTHOR]

Permanent magnet eddy current couplers have been widely used in large fan and pump loads to achieve the purpose of speed regulation and energy saving. In order to reduce the coupler axial volume and simplify the actuator, a novel flux adjustable axial flux permanent magnet eddy current coupler (FAAF‐PMECC) is proposed in this paper. The permanent magnet rotor is divided into three parts: the inner, middle and outer parts, where the permanent magnets are embedded in the core and the adjacent poles are magnetised in opposite directions. The middle part is the adjusting permanent magnet ring (AR), which can rotate around the shaft. The inner part and outer part are fixed permanent magnet rings (FR) that are fixed with the shaft, and the output torque can be controlled by adjusting the relative angle of AR and FR. The structure and working principle of FAAF‐PMECC are described in detail, and the output torque analytical model of the whole regulating process is established based on the magnetic equivalent circuit method. The AR regulation process is simulated by the variable reluctance model. The validation results show that the proposed structure can achieve a good speed regulation effect, and the output torque calculated by the analytical model in a certain slip speed range matches well with the output torque obtained using the 3D finite element method and experimental measurements. The sensitivity analysis of the structure parameters is also carried out. The analysis shows that the proposed coupler can achieve a wide speed range. [ABSTRACT FROM AUTHOR]

In this study, a fractional‐order integral terminal sliding mode control (FITSMC) system is proposed to control a new voice coil motor (VCM)‐driven X–Y motion stage with different thrust forces in the X–Y axes for the tracking of reference contours. First, the operation principle and dynamics of the stage are conducted based on the equivalent electrical circuit and magnetic analysis of the VCM. Subsequently, an integer‐order integral terminal sliding mode control (ITSMC) approach is designed to control the stage for contour tracking in finite time. To enhance the positioning accuracy of the ITSMC, a novel FITSMC system is further proposed by bringing in a new fractional‐order integral terminal sliding surface. However, the hitting control gain for the FITSMC is difficult to design because of the system uncertainties. To address this issue, an intelligent adaptive uncertainty observer (AUO) is proposed to directly observe the system uncertainties, thereby eliminating the need for hitting control term and attenuating the chattering phenomena of control force. Stability analysis of the proposed FITSMC and FITSMC‐AUO systems is conducted on the basis of the Lyapunov stability theory. The experimental results demonstrate the effectiveness and superiority of the proposed control systems in comparison with the existing ITSMC system in the contour tracking tests. [ABSTRACT FROM AUTHOR]

The dual‐excited synchronous condenser (DESC) has two field windings whose axes are located at direct and quadrature axes respectively. The DESC has more capacity of absorbing reactive power than that of the traditional synchronous condenser (TSC). However, the q‐axis field winding distributed on the d‐axis magnetic pole surface can decrease the magnetic circuit area of the rotor core of DESC, thus it may result in the increase of the total harmonic distortion (THD) of the magnetic field and the oversaturation of the rotor magnetic circuit. In order to obtain better electromagnetic characteristics of DESC, a q‐axis field winding structure is proposed by optimising the number of slots, slot pitch and slot dimensions. The influences of the number and pitch of slot in q‐axis on the air‐gap radial flux density and THD of DESC are studied under the d‐, q‐ and dual‐axis excitation modes. The dimensions of the q‐axis slots are optimised by combining the time‐stepping finite element method and Taguchi method, and the optimal structure of q‐axis field winding is obtained. A 10‐kVar DESC is developed to verify the simulation results. This study provides theoretical basis for the design and manufacture of the DESC. [ABSTRACT FROM AUTHOR]

A novel DC‐Excited Flux‐Switching Linear Motor (DC‐FSLM) is investigated in this paper, where a simple secondary is used as the machine stator. The phases and excitation windings are placed on the primary, which contributes to a low‐cost and simple structure linear motor with acceptable dynamic performance. The motor operation under dynamic load is analysed by a parametric Magnetic Equivalent Circuit (MEC), and the core saturation is modelled by the non‐linear reluctance of the flux tubes. Moreover, the end‐effect is considered by virtual zones at both entrance and exit ends of the primary. In the considered MEC, the model accuracy can be selected as desired as well as different DC‐FSLMs with various properties can be modelled. Finally, the machine capabilities and performance characteristics are discussed by simulation results, and validation is performed by the Finite Element Method (FEM). [ABSTRACT FROM AUTHOR]

To facilitate the safe adsorption and stable motion of robots on curved metal surfaces, a wall‐climbing robot with a wheeled‐type mobile mechanism that can passively self‐adapt to walls with different curvature is proposed. The robot is composed of two relatively independent passive adaptive mobile mechanisms and overrunning permanent magnetic adsorption devices to achieve effective fitting of the driving wheels to the wall surface and adaptive surface motion. The overall design is based on a double‐hinged connection scheme and gap‐type permanent magnetic adsorption. The minimum adsorption force required for the robot to achieve stable climbing motion with no risk of slipping or capsizing is determined by developing a static analysis model. The effects of air‐gap size and wall thickness on the adsorption force are analyzed by means of magnetic circuit design studies and parametric simulations on the permanent magnet adsorption device, as well as design optimization of the permanent magnet device. The motion performance test of the fabricated prototype shows that the robot can achieve adaptive curvature motion with self‐attitude adjustment, and has a certain load capacity, obstacle crossing capability, and good surface adaptivity. [ABSTRACT FROM AUTHOR]

Partial deep saturation of magnetic circuit is common in short‐term working permanent magnet (PM) machines in aviation, aerospace, new energy power generation and other fields. In order to accurately calculate the electromagnetic characteristics of the short‐term working machine, a novel mesh‐based equivalent magnetic network for the deep saturation region is proposed. Firstly, the deep saturation mechanism of the magnetic circuit of short‐term working motor is analyzed, and the deep saturation region is determined; Secondly, a Pointy topped hexagonal segmentation approach (PT‐HSA) grid generation method is proposed to effectively simulate complex magnetic flux paths. The PT‐HSA grid division and node compilation rules were analyzed in detail. In addition, a nonlinear magnetic network model based on reluctance grid model and equivalent magnetic circuit model is established. Compared with the quadrilateral segmentation approach (QSA) model, the calculation results of PT‐HSA model are closer to the finite element simulation results in the loading and instantaneous compensation conditions. Finally, an experimental platform is built, and the accuracy of the PT‐HSA magnetic network model is verified by the experimental results. © 2022 Institute of Electrical Engineers of Japan. Published by Wiley Periodicals LLC. [ABSTRACT FROM AUTHOR]

Recently, linear generators have been widely employed to convert oceanic wave energy into electricity. Among various linear generators, linear permanent magnet generators (LPMGs) have gained attention due to their special characteristics such as high power density and simple control structure. In this paper, flat double‐sided LPMG is investigated and designed. Considering all effective design variables, a particle swarm optimization algorithm‐based optimization method is employed to maximize efficiency and minimize weight. The optimization results show an increase in efficiency and a reduction in the weight of the generator. Finally, the design results are evaluated and validated using magnetic equivalent circuit and finite element analysis methods. [ABSTRACT FROM AUTHOR]

The high‐thrust linear motor with a lightweight and high‐strength mover was developed for operating circuit breakers. The linear motor is composed of a lightweight mover that has permanent magnets sandwiched between magnetic poles and an armature with a three‐dimensional magnetic circuit. The specifications and performance of the linear motor were determined to cut off current soundly. Then, a prototype of a fully electrically operated breaker using linear motor was investigated. The linear‐motor‐based operating mechanism designed for the circuit breaker reached the open‐pole position in 13.2 ms from the start of movement. However, the time from opening to 0.5 cycle was 9.0 ms. In addition, the variation in breaking operation time was within 1 ms, which was expected that stable controlled operation. [ABSTRACT FROM AUTHOR]

A new hybrid analytical model (HAM) based on conformal mapping (CM) method and magnetic equivalent circuit (MEC) model is presented in this paper for electromagnetic modelling of cage rotor induction motors (CRIMs) used in electric submersible pumps (ESPs). For every operating point, the iron parts are modelled with a non‐linear MEC model to calculate the equivalent virtual currents, which represent the influence of magneto motive force (MMF) drops and MMF sources in stator and rotor cores. The effects of the equivalent virtual currents on the air‐gap magnetic field are then considered using the CM method and Hague's solution. This approach for calculating the air‐gap field is also used to prepare a 3‐D lookup table (3‐D LUT) for each element of inductance matrix and derivative of inductance matrix in terms of rotor position. These LUTs are then used for transient modelling and analysis of CRIM under no‐load and loading conditions. The accuracy of proposed HAM is validated by comparing the results obtained through HAM with corresponding results obtained from finite element method and experiment set‐up. [ABSTRACT FROM AUTHOR]

In order to improve the reliability of the traditional doubly salient electro‐magnetic generators (DSEG) and realize the isolation of interphase magnetic circuit, a U‐shaped rotor stator excitation generator (UR‐SEG) for vehicle applications is proposed in this paper. The machine has the interphase physical isolation and short flux path structure because of the U‐shaped rotors. According to the theoretical analysis of the fault‐tolerant characteristics of this UR‐SEG, the characteristic of the phase electromotive force (EMF) of the UR‐SEG completely overlaps with the EMF of front and rear phase in the entire power generation stage is revealed. Then the flux linkage, EMF, output voltage of both normal and faulty states are comparative investigated using the two‐dimensional finite element method (FEM). The output characteristics of the normal state and four faulty states of the machine with different exciting currents are researched, and the influence rules of fault on output characteristics are obtained. Finally, the outstanding fault‐tolerant characteristics of the UR‐SEG were verified by the experimental results. © 2022 Institute of Electrical Engineers of Japan. Published by Wiley Periodicals LLC. [ABSTRACT FROM AUTHOR]

Accurate modeling of slotting and magnetic saturation effects has been two main challenges for analytical modeling of electric machines. In this article, first, different techniques such as sub‐domain (S‐D) model, winding function theory, magnetic equivalent circuit (MEC) model, and conformal mapping (CM) method are introduced to analytical model and analysis of electric machines. These techniques are also compared in terms of their accuracy, and computational complexity. Second, with respect to the comparison results, a new hybrid analytical model is presented for electromagnetic modeling of wound rotor induction motors, which consider the modeling accuracy of slotting and magnetic saturation effect, simultaneously. In this way, the air‐gap region is modeled by using S‐D model, and the iron parts are considered by using MEC model assisted by CMs. In final, the analytical results are verified by comparing with corresponding results obtained through finite element method and experiment set‐up. [ABSTRACT FROM AUTHOR]