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In this article, a clear and concise analytical method for predicting the performance of a Liquid-cooling eddy current brake (LC-ECB) is proposed. The LC-ECB has a coolant channel in the rotor to allow direct cooling of the inner surface of the stator. The static air-gap magnetic field distribution is obtained by the dynamic magnetic equivalent circuit (MEC) method, and the magnetic flux leakage and global magnetic saturation effects are fully considered. The magnetic field intensity distribution function of the eddy current reaction magnetic field is derived for the first time based on Ampere circuital theorem. Considering the local magnetic saturation and skin effect, a novel double-iteration algorithm based on the conservation principle of magnetic pressure drop is applied to obtain the transient air-gap flux density distribution, and then the brake torque expression is obtained. The finite element method (FEM) and experimental results show that the proposed method is feasible and effective. The new model is easy to program and can be easily used in the initial design and optimization of LC-ECB. [ABSTRACT FROM AUTHOR]

This paper deals with the design and analysis of a surface-mounted outer rotor in-wheel motor (IWM) with the aim of reducing cogging torque and torque ripple for electric vehicles. The proposed IWM is equipped with axial sinusoidal surface-mounted permanent magnets (PMs), with the purpose of producing sinusoidal air gap flux density distribution, thus to realize sinusoidal back electromotive force (EMF) and smooth electromagnetic torque. To highlight the advantage of the proposed IWM, the conventional IWM with tile-shaped PMs and the IWM with stepwise-shaped PMs are also studied for comparison. The finite element method in the commercial software package is utilized to analyze the performance of the three motors, including the radial flux density of air gap, back EMF, cogging torque, and electromagnetic torque. Through the quantitative comparison, it is found that the proposed IWM greatly reduces the cogging torque, highly improves the sinusoidality of back EMF, and nearly eliminates the torque ripple. [ABSTRACT FROM AUTHOR]

In this paper, power-sizing equations of rotor-permanent-magnet flux-switching (RPM-FS) machines are proposed and implemented, where the main decisive factors of the electromagnetic torque, namely electric loading and magnetic loading, are deduced, respectively. Although the topologies of RPM-FS machines are evolved from traditional stator-PM flux-switching machines, there are still seriously flux leakages between poles, and it is hard to derive the peak value of the air-gap flux density directly. Hence, a local simplified magnetic equivalent circuit is utilized to calculate the magnetic loading, which is crucial for the power-sizing equation. The influences of the pole-to-pole flux-leakages and harmonics in back-EMF are considered to improve the calculated accuracy of the power-sizing equation. Consequently, the electromagnetic torque can be predicted with acceptable accuracy. The feasibility of the power-sizing equation is verified by the finite element analysis and experimental results. [ABSTRACT FROM AUTHOR]

In this work, a novel superconducting (SC) inductor topology for an axial flux synchronous machine is presented and tested. The proposed device combines HTS YBaCuO bulks and coils supplied with DC current to create a variable air gap flux density distribution. In fact, the two SC bulks modulate and redirect the flux lines produced by the coil thanks to their magnetic field shielding property. This results in a periodic space variation of the axial component of the flux density. A 3D electromagnetic modeling based on a finite element solution is developed to demonstrate the relevance of using the magnetic shielding properties of SC bulks. In order to verify the screening properties of the SC bulk, a prototype of the proposed inductor was constructed and tested in the laboratory. [ABSTRACT FROM AUTHOR]

The torque ripple is affected by both the stator and the rotor magnetic field harmonics. In synchronous reluctance motors (SynRM), there are only rotor permeance harmonics existing on the rotor side for the absence of the rotor windings. Since the asymmetric rotor flux barriers are widely applied in the SynRM rotor, it is difficult to calculate the rotor permeance accurately by the analytical method. In this article, the effects of the rotor permeance harmonics on the air-gap magnetic field are studied by a virtual permanent magnet harmonic machine (VPMHM), which is a finite-element (FE) based magnetostatic analysis model. The air-gap flux density harmonics produced by the SynRM rotor are extracted from the VPMHM model and used as the intermediate variables for the torque ripple optimization. The proposed method does not need to solve the transient process of motor motion. Hence, the time of the optimization process can be significantly shortened. Finally, a full electric cycle is simulated by dynamic FE simulation, and the torque ripple is proved to be effectively reduced. [ABSTRACT FROM AUTHOR]

This paper proposes a novel flux switching claw pole machine (FSCPM) with soft magnetic composite (SMC) cores. The proposed FSCPM holds advantages of the conventional flux switching permanent magnet machine (FSPMM) and claw pole machine (CPM) with SMC cores. As permanent magnets are installed between the stator claw pole teeth, FSCPM has good flux concentrating ability, and the air gap flux density can be significantly improved. The torque coefficient of FSCPM is relatively high due to the applied claw pole teeth and global winding. FSCPM is mechanically robust because there are no windings or PMs on its rotor. Moreover, the core loss of FSCPM is relatively low for the SMC material has lower core loss at high frequency compared with silicon steels. The topology and operational principle of FSCPM are explained first. Several main dimensions of the machine are optimized to achieve better performance, based on 3D finite element method (FEM). Furthermore, the rotor skewing technology is adopted to reduce the cogging torque and torque ripple. [ABSTRACT FROM AUTHOR]

This paper presents a nonlinear iterative magnetic equivalent circuit (MEC) model for a novel counter-rotation dual-rotor axial flux permanent magnet synchronous machine (CRDR-AFPMSM). The proposed machine mainly consists of two rotors with opposite rotation directions, two sets of concentrated windings and a stator core sandwiched in between the two rotors. The model takes into account of the nonlinear characteristics of the saturable permeance in the stator core, and the permeance matrix is updated by an iterative procedure to accurately illustrate its nonlinear feature. The air gap flux density, back electromotive force (EMF) and torque are predicted by the model. Based on the nonlinear model, the thickness of the stator yoke is determined. All of the results obtained by the proposed model match with finite element analysis (FEA) results closely, thus the validity of the proposed MEC model is verified. [ABSTRACT FROM AUTHOR]

This paper examines the influence of pole and slot combinations on the electromagnetic performance of the flux-switching permanent magnet (FSPMs) machine. For this purpose, first the production of air gap flux density in machine analytically discussed. Next, five different pole and slot combination are selected by using the knowledge of air-gap flux density expression. The performances of the different combinations are analyzed and compared using the finite element analysis (FEA), and optimal pole and slot combination is suggested. It is found that the pole and slot combination has a dominant effect on machine performance and needs to be considered during the design stage. [ABSTRACT FROM AUTHOR]

This paper presents a new rotor shape design with optimum reverse 3rd harmonic for wound field synchronous machines to effectively enhance the saliency ratio and reduce the torque ripple in a micro electric vehicle traction system. Due to the enhanced saliency ratio, the reluctance torque is expected to be improved. The air gap flux density distribution is reshaped by the new rotor shape method, which benefits the low torque ripple. By contrast, the reverse 3rd harmonic injection is much more suitable than the general 3rd harmonic injection for increasing the effective air gap length along the q-axis for a high saliency ratio. Subsequently, three amplitudes of the reverse 3rd harmonic are studied and it is found that the optimum reverse 3rd harmonic is 1/6 of the fundamental one. To verify the effectivity of the proposed design, the original model and the ICS model are compared. Finally, all the motor characteristics, such as back electromotive force, cogging torque, and electromagnetic torque, are predicted using a 2-D finite-element method with the aid of JMAG-Designer. [ABSTRACT FROM AUTHOR]

This paper investigates the opportunity to use a proper geometry of Line start permanent-magnet synchronous motor (LSPMSM) that allows the same stator to be used for three different rotor structures, namely, typical, solid rotor and strange rotor. The air-gap flux density, back electromotive force (EMF), cogging torque, efficiency, starting performance and synchronization capability of the three machines are analyzed and compared. It is demonstrated that the typical rotor has the highest air-gap flux density, and the strange rotor has the lowest cogging torque and highest starting torque. In addition, the solid rotor has the lowest total harmonic distortion (THD), the highest efficiency, and the lowest cost. The size of PM and rotor structure are optimized to maximize the starting torque and efficiency of the solid rotor LSPMSM based on response surface method (RSM). Finally, the solid rotor LSPMSM is prototyped to verify the results of the finite element analysis. [ABSTRACT FROM AUTHOR]

The purpose of this paper is to optimize the PM arc ratio of consequent pole permanent magnet vernier machine (CP_PMVM). The operation principle of the CP_PMVM is discussed. An optimization parameter K related to the PM arc ratio is derived. For the CP_PMVM, the amplitudes of the 4th and 14th order harmonics of the air-gap flux density, the amplitude of the back electromotive force (back-EMF) and the average torque all have positive correlations with K. The optimal PM arc ratio is 0.64. The three phase inductances are approximately constants, and the d-axis inductance is equal to the q-axis inductance. The PM flux linkages are sinusoidal. The no-load back-EMF waveform of the measured phase is nearly sinusoidal. The gear ratio of the CP_PMVM evaluated from the back-EMF is close to the design value. Furthermore, a controller according to the mathematical model is designed. The CP_PMVM vector control with a sliding-mode (SM) speed controller exhibits a smooth starting, and has an anti-jamming capability. [ABSTRACT FROM AUTHOR]

In this paper, one kind of U-shape permanent magnet embedded salient pole wind generator is proposed. The permanent magnet is divided into three sections to form a U-shaped structure and inserted into the salient pole in the generator. The size of the PM near the side frame is small, therefore, there is sufficient PM location modification space in the salient pole. Some flux-barriers are set in the upper core of the salient pole, which can reduce the q-axis inductance, and ultimately increases the generator maximum output power. To evaluate the generator's overall performance, some other important electromagnetic parameters such as the air-gap flux density, the output voltage, the cogging torque, the output power, and the demagnetization performance are all calculated and analyzed base on finite element method (FEM). All the above parameters are compared with that of one V-shape permanent magnet embedded salient pole wind generator. The analysis results show that, with the same volume of permanent magnet, the proposed U-shape permanent magnet embedded salient pole wind generator has higher power density than the V-shape permanent magnet embedded salient pole wind generator. [ABSTRACT FROM AUTHOR]

To improve the utilization of wind energy, a new type of deflectable double-stators switched reluctance wind power generator is proposed to solve the unicity of the rotor rotation of existing switched reluctance generator (SRG). The generator adopts inner and outer double-stators structure. The multi-degree-of-freedom deflection of the rotating shaft can adapt to different wind directions and is suitable for the combination of electric fields with unstable energy amplitude, which can improve the working efficiency of the generator. The finite element analysis is used to calculate the rotation of the air gap magnetic flux inside the generator rotor, which lays a foundation for analyzing the vibration displacement of the stator structure. The magnetostriction of stator structure is the main cause of generator vibration. Based on the theory of mechanics, the basic equation of structural mechanics considering magnetostrictive effect is established. Magnetio-solid coupling simulation of internal and external stator and rotor rotation and deflection is carried out using FEA, and the stress distribution and corresponding vibration displacement are obtained. The simulation and analysis results provide a reference for further optimizing the structure of such generators and improving the stability of their operation. [ABSTRACT FROM AUTHOR]

This paper presents an analytical method to calculate the air-gap magnetic flux density distribution of a permanent magnet (PM) vernier motor. For this purpose, the air gap permeance, the magneto-motive force (MMF) of rotor magnets and the MMF from stator winding are respectively expressed in the form of Fourier series. The permeance function whose values of the all harmonics are given in terms of geometry, is utilized with the MMF of PMs to analyze the air gap flux density of the vernier machine. In addition, the role of each harmonic components of flux density in the production of back electromotive force (back-EMF) and torque is examined. Finally, the effectiveness and accuracy of the derived expressions are checked with the help of finite element (FE) analysis. [ABSTRACT FROM AUTHOR]

In this study an adaptive on-line speed estimation approach has been proposed for a sensor-less indirect air-gap field orientation controlled (AGFOC) induction motor (IM) drive. The indirect AGFOC IM drive was established by utilizing the stator current and air-gap flux. The estimated synchronous speed was derived from the developed reactive power based adaptive air-gap flux estimator, and the estimation of rotor speed was made by subtracting the slip speed from the estimated synchronous speed. Speed estimation and control by the AGFOC IM drive could be extended to include constant power operation mode by utilizing the field weakening technique. The MATLAB® ∖Simulink ® toolbox was used to simulate this system and all the control algorithms were realized using a TI DSP 6713-and-F2812 card to generate pulse width modulation (PWM) signals to the power stage, actuate an IM to validate this approach (sensor-less AGFOC). Both simulation and experimental responses confirmed the effectiveness of the proposed system. [ABSTRACT FROM AUTHOR]

In order to reduce the transverse edge effect of linear induction motors (LIMs) for low-speed Maglev train, this paper proposes a novel single-sided LIMs (SLIMs) with V-shaped ladder-slit secondary. Firstly, the topology of this SLIMs is introduced based on the erected 3-D finite element model. Secondly, for the V-shaped ladder-slit secondary, the effect of slot combination is investigated, and then the secondary is optimized by a single-parameter optimization method, including the width of secondary side-bars, secondary slot width, transverse width of secondary slits and the skew angle of V-shaped slits. Thirdly, the air gap flux density, eddy current, thrust force and normal force of this SLIMs are calculated, respectively. By comparing to those of two SLIMs with available double ladder-slit and cap-solid secondary, the results show the proposed novel SLIMs can improve the performance due to effectively reducing the transverse edge effect. Finally, to the proposed SLIMs, the effect of the middle bar in V-shaped ladder-slit secondary is studied. It is found that adopting middle bar can improve the performance and increase the mechanical strength, which is more suitable for low-speed Maglev train. [ABSTRACT FROM AUTHOR]

Due to their advantages of high efficiency, high power density, and strong fault-tolerance ability, fractional-slot concentrated-winding permanent-magnet (FSCW-PM) machines are of particular interest in the applications such as wind power generation and electric vehicles. However, FSCW-PM machines suffer from rich winding magnetomotive force (MMF) space harmonics by the armature reaction field, which may increase eddy current loss. In this paper, a new low harmonic FSCWPM machine is designed, which can reduce some space harmonics of low order in the air-gap flux density. A new magnetic equivalent circuit (MEC) model is developed to analyze the designed PM machine, which offers less computation time and more calculation accuracy. Finally, a prototype machine is built and the measured results verify the theoretical analysis and the developed MEC model. [ABSTRACT FROM AUTHOR]

The cogging torque calculation of interior permanent magnet synchronous motors (IPMSMs) has only been conducted by the finite element method (FEM) due to their complexities. However, FEM analysis requires considerable computational time during the design process. To deal with this problem, a new analytical method is proposed to calculate the cogging torque in IPMSMs. The radial and circumferential air-gap flux density for calculating the cogging torque utilizes the magnetic equivalent circuit model, conformal mapping method, and approximate equations of the magnet end. The validity of the proposed method was confirmed by comparing the results of the proposed method with those of FEM. [ABSTRACT FROM AUTHOR]

The E-core hybrid-excitation linear switched-flux permanent magnet machine (LSFPMM) is low cost, which not only accommodates armature and permanent magnets (PMs) in short primary, but also cuts half of PM volumes compared with its C-core counterpart. It also can easily adjust the air gap magnetic field flexibly through the injection of different DC currents. This paper introduces E-HELSFM with different end shapes firstly, while a shape with the best symmetry of flux and minimal detent force is developed and further investigated. Based on finite element model, the flux-adjusting principle of the proposed hybrid-excitation motor is presented, and certain geometric parameters are optimized for better flux-regulating capability and larger thrust force density. Then, the field ratio, which means the ratio of field area to a single slot area, is optimized to reach a tradeoff between force density and flux-adjusting capability. For the optimized model, the flux-adjusting as well as thrust force performances under different excitation conditions are investigated. Then, the flux-weakening control under different excitation levels is discussed. The simulated results show that the optimized machine exhibits good constant power operation capability through flux-weakening control and enhanced overload ability by flux-enhancing control. [ABSTRACT FROM AUTHOR]

Permanent magnet (PM) machines with tooth coil windings are designed and analyzed. We study how the slot wedge material affects the behavior of PM losses when using tooth coil windings, which generate a significant air gap flux density harmonic content. The losses and cogging torques of a surface permanent magnet rotor and an interior permanent magnet rotor are compared in no-load and load situations. A finite element analysis applying Cedrat's Flux2D is made. Motors of this size can have high permanent magnet eddy current losses, and therefore, segmented magnets are often preferred even though interior magnets and semi-magnetic wedge material are used. The study shows that tooth coil windings may benefit from using semi magnetic material as a wedge material as it decreases the stator iron losses and, especially, losses in the permanent magnets. [ABSTRACT FROM AUTHOR]