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The flux-concentrating permanent-magnet (FCPM) machine with two V-shape magnet pieces in one stator pole has attracted considerable attention due to its excellent torque density and permanent magnet (PM) usage efficiency, whereas the torque ripple of the FCPM machine is usually high. This article aims to make a multiobjective optimization design for the FCPM machine. The optimization process is divided into three steps for different optimization objectives on two sets of geometric variables at different operation conditions. The simulated results show that the output torque of the optimized FCPM machine is increased significantly while the torque ripple has been decreased greatly. Finally, the open-circuit field distributions, the output torque, the torque-speed characteristics, and PM demagnetization of the optimized FCPM machine are investigated considering different PM shapes and PM temperature rise, which indicates that the optimized FCPM machine has favorable torque characteristics, speed range, and antidemagnetization abilities. [ABSTRACT FROM AUTHOR]

A fast and precise lumped-parameter thermal network (LPTN) model is presented for a flux-switching permanent-magnet double-rotor machine used for hybrid electric vehicles (HEVs), which has attracted attention due to the compact structure. The three-dimensional (3-D) LPTN model provides the steady-state thermal solution to derive the temperatures at different parts of the machine, in which the power losses of various working conditions are used as heat sources for calculating the temperatures of different operational modes. In the LPTN studies, a transformation of an irregular slot structure into a regular one is applied to simplify the calculation of the winding thermal resistance. A 3-D finite element thermal model of this machine is also established to calculate the temperatures of the main machine components for a comparative study purpose. Tests performed on the designed machine verify that the defined LPTN model has a high ability to predict the nodal temperatures accurately. [ABSTRACT FROM AUTHOR]

In this paper, an outer-rotor-permanent-magnet flux-switching (ORPM-FS) machine is proposed. It not only inherits the traditional flux-switching permanent-magnets (FSPM's) flux-switching principle and the high torque density, but also overcomes the FSPM's magnetic saturation and adds the slot area, thus producing favorable output torque capability at rated load and overload condition. By means of finite element method, the ORPM-FS machine is optimized through multi-level process for multi-objectives: the basic variables optimization for high output torque and low torque ripple, the pitch coefficient optimization for favorable torque characteristics and efficiency, the optimal selection for high efficiency at flux-weakening operation. At last, the electromagnetic performances of the optimized ORPM-FS machine are analyzed, which shows that the proposed machine can receive high torque density, low torque ripple, high efficiency, and favorable overload capability. [ABSTRACT FROM AUTHOR]

In order to reduce the axial length and increase the critical speed of the small magnetic suspension drive system, a new slice hybrid magnetic bearing (SHMB) with two radial air-gaps is proposed. The structure and suspension mechanism of the SHMB is introduced, and then the mathematical models of the radial suspension force are deduced using the equivalent magnetic circuit method. The suspension mechanism is proved. The radial and axial suspension forces are then calculated by the finite element method. The experimental prototype SHMB is finally designed and constructed. The stable suspension of the rotor is realized, and the suspension forces are measured. The results of the finite element calculation and experimental measurement verify the correctness of the mathematical models. [ABSTRACT FROM AUTHOR]

The multimechanical-port double-rotor machine, as a core component in hybrid electric vehicles, has attracted considerable attention due to the merits of compact structure, control flexibility, and diverse performances. However, since there often exist two electric or mechanical ports in one compound machine frame, traditional design theory cannot be applied to it directly. Besides, because of the relatively complex machine structure and multiple design parameters, design objectives often influence even conflict with each other. In this paper, a new multiobjective optimization design approach is proposed to design and optimize a flux-modulated double-rotor flux-switching permanent magnet machine, where multiple driving modes are considered. To verify the feasibility of the double-rotor machine and the effectiveness of an optimization design method, the electromagnetic characteristics of the machine are investigated in detail. Finally, a prototype machine is built and tested. Both theoretical analysis and experimental results verify the validity of the proposed machine and multiobjective optimization design approach. [ABSTRACT FROM AUTHOR]

The flux-switching permanent-magnet (PM) double-rotor machine (FSPM-DRM) used for hybrid electric vehicles has attracted considerable attention due to the compact structure and high torque density. Compared with the conventional machine, the FSPM-DRM suffers from more iron loss, PM eddy-current loss, and conductor eddy-current loss for its larger rotor pole numbers. The iron loss exists not only in the stator but also in the rotor, while its calculation becomes more difficult due to complex flux density waveforms. A more accurate analytical model for the iron loss, PM eddy-current loss, and conductor eddy-current loss calculation is proposed for the FSPM-DRM and compared with the results from finite-element method. Based on the calculated losses, the efficiency of the FSPM-DRM is also investigated. Some experimental results are reported, validating the numerical and simulation results. [ABSTRACT FROM AUTHOR]

The flux-switching permanent-magnet double-rotor machine (FSPM-DRM) used for hybrid electric vehicles has attracted considerable attention due to the compact structure and high torque density. Compared with conventional machine, the FSPM-DRM suffers from more severe thermal problems in its inner rotor. This paper aims to make an accurate prediction of the performances and temperature distributions in the FSPM-DRM. First, the eddy current loss in windings with an improved analytical method is discussed and the results are validated by those from a 2-D finite-element (FE) model. With the obtained power losses, the lumped-parameter scheme considering end effect is compared with a 3-D FE thermal model to predict the temperature in each part of the FSPM-DRM at hybrid driving mode, in which both yield similar results. Then the maximum temperatures of different parts at the rated load and 160% load under various operational modes are simulated. Some experimental results are reported, validating the numerical and simulated results. [ABSTRACT FROM AUTHOR]

The traditional bearingless permanent magnet synchronous motor has complex decoupling control problems. To overcome the drawbacks above, a novel hybrid permanent magnet type bearingless motor (HPMTBM) is proposed in this paper, which has integrated the merits of hybrid excitation permanent magnet motor and magnetic bearings. The main advantages of this HPMTBM are the simple control mechanism and the low power consumption. First, the principle and theoretical background of this motor are introduced. Then, the mathematical models of radial suspension force and torque are established using Maxwell stress tensor method, and air-gap magnetic fields, radial suspension forces are calculated by finite-element analysis. Finally, the prototype motor is designed and constructed. The radial suspension forces and rotor radial displacements are tested. The simulation and experimental results show the feasibility of the proposed HPMTBM. [ABSTRACT FROM AUTHOR]

The use of double-rotor machines (DRMs) for hybrid electric vehicles (HEVs) has attracted considerable attention due to their compact structure and high torque density. Compared with the conventional four-quadrant transducer (4QT), the proposed flux switching permanent magnet double-rotor machine (FSPM-DRM) has PMs located in the stator, and can offer better performances in terms of magnetic coupling and torque ripple, which are especially important for DRM control in HEVs. This paper presents a comparative analysis of the 4QT and FSPM-DRM by employing the finite element method (FEM). For a fair comparison, two topologies are designed under the same peripheral dimensions, current density, and copper loss. Considering the effect of skewed slots in the 4QT, the corresponding performances are calculated with multi-slice 2-D time-stepping FEM. The simulated results illustrate that the proposed FSPM-DRM offers larger output torque, lower torque ripple, and smaller magnetic coupling than the 4QT. Nevertheless, the eddy current losses in PMs and windings of the FSPM-DRM are higher than those of the 4QT. Experimental results of the FSPM-DRM prototype are also given to verify the validity. [ABSTRACT FROM AUTHOR]

This paper presents the comparison of linear primary permanent magnet vernier (LPPMV) machine and linear vernier hybrid (LVH) machine. The LPPMV machine and the LVH machine both operate based on the magnetic gear principle, hence possessing the advantages of low speed and high thrust force density. In addition, both machines employ similar configurations between which the key difference is that a one-piece primary iron core is employed in the LPPMV machine instead of the modular cores in the LVH machine. Using the finite element method (FEM), the characteristics and performances of two machines are analyzed and compared. The results show that the LPPMV machine exhibits higher thrust force and lower cogging force. Finally, the FEM results are validated by experiments based on a prototype of the LPPMV machine. [ABSTRACT FROM AUTHOR]

In the permanent magnet (PM) machines, the Halbach PM (HPM) machine can offer higher performance than others, while they require more rare-earth PMs. Due to the high price of rare-earth PMs, such as NdFeB and SmCo magnets, the cost has become a serious drawback of the HPM machine. To overcome this disadvantage, a new fault-tolerant HPM (FTHPM) machine by mixing rare-earth PM and ferrite magnets is proposed in this paper. The proposed machine can be a good candidate for many applications because of low price and stable supply of ferrite magnets. Furthermore, the lumped parameter magnetic circuit method is used to analyze the proposed FTHPM machine. In addition, the finite element method is adopted to verify the effectiveness of the theoretical analysis. [ABSTRACT FROM AUTHOR]

This paper proposes a new magnetic planetary geared permanent magnet brushless (MPG-PMBL) machine for hybrid electric vehicles. According to the dynamic performances in hybrid electric vehicles, the proposed machine needs to offer the advantages of high power density, high efficiency, and low torque ripple. To realize these goals, a multi-objective optimization design method based on the combined design of experiments approach and response surface method is presented, where three key optimization objectives of the efficiency, total loss, and cogging torque are selected. After the optimization, some reasonable key design variables are determined and the proposed MPG-PMBL machine is newly designed and built for evaluation. Both theoretical analysis and experimental results verify the validity of the proposed optimization method. [ABSTRACT FROM AUTHOR]

This paper proposes a new linear hybrid excited flux reversal motor with inset permanent magnets (PMs). The proposed motor adopts the excitation windings in the primary, hence offering the desired flux control capability. The novelty of the proposed motor is to design a modular primary structure. Then, it has very symmetrical and sinusoidal back electromotive force (back-EMF) and smooth thrust even at various excitation currents. In addition, because of the inset PMs, the proposed motor is free from PM irreversible demagnetization. The electromagnetic performances of the proposed motor are analyzed using the time-stepping finite-element method, such as magnetic field distribution, back-EMF, and thrust, verifying the effectiveness of the theoretical analysis. [ABSTRACT FROM AUTHOR]

This paper proposes an axial permanent magnet-biased hybrid magnetic bearing, which possesses the advantages of low power consumption, simple structure, and easy control. The structure and operation principle are introduced. Then, the mathematical models, including the suspension force expression, are built based on traditional equivalent magnetic circuit. In addition, the basic principle of structure parameter design is presented, based on which the key parameters are given. Due to the inaccuracy of the traditional equivalent magnetic circuit, an improved method for magnetic circuit is introduced. Last, the accuracy of the analytical method is validated by finite element analysis and it also has an important reference value for other types of magnetic bearings design. [ABSTRACT FROM AUTHOR]