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In this paper, a dual-rotor slotless axial-flux permanent magnet (AFPM) motor with equidirectional toroidal winding (ED-TW) is proposed and compared with the AFPM motor with traditional toroidal winding (T-TW) with the same dimensions, number of coils and poles. Different from the T-TW, only the positive sides of coils of the ED-TW are left on one side of the stator core, the return sides of the coils are all removed to the other side of the stator core. Firstly, the structure and operation principle of the two motors are introduced and analyzed. To clarify the features of the ED-TW, the synthetic electromotive force (EMF) vector and armature reaction field of the ED-TW and T-TW are studied. Secondly, the main size equations of the AFPM motors with toroidal windings are presented. Subsequently, the electromagnetic characteristics of the AFPM motors with ED-TW and T-TW are analyzed and compared based on the three-dimensional finite element method (3D-FEM). The comparison results indicate that the AFPM motor with ED-TW has superiority in torque density and efficiency. Finally, a prototype of the AFPM motor with ED-TW is manufactured and tested, which validates the feasibility of the proposed motor and the correctness of the analysis of the 3D-FEM. [ABSTRACT FROM AUTHOR]

Direct‐drive permanent magnet synchronous generators (DDPMSGs) are gaining more and more attention in the field of wind power because of the advantages of simple structure, high efficiency and high reliability. However, due to the extremely low rotational speed, large volume and heavy weight of DDPMSGs, it poses serious challenges for transportation and installation, which limits its application. Therefore, a DDPMSG with novel toroidal windings (NTW) is proposed to improve power density in this paper. Unlike regular windings, each coil of the NTWs is wound onto the stator yoke in the same direction. The special configuration enables the generator to have higher winding coefficient, so that the DDPMSG with NTWs (NTW‐DDPMSG) can achieve higher power density than traditional fractional slot concentrated windings (FCW). The proposed topology and operating principles are described in detail. To verify the merits of the proposed NTW‐DDPMSG, the electromagnetic parameters of two external rotor surface‐mounted DDPMSGs equipped with NTW and FCW respectively are designed. The characteristics of air‐gap magnetic field, no‐load electromotive force, output power, loss and efficiency are analysed on the conditions of different loads and speeds. Comparison results show that the proposed NTW‐DDPMSG has higher power density than FCW‐DDPMSG. [ABSTRACT FROM AUTHOR]

The six‐phase direct‐drive permanent magnet synchronous motor (DDPMSM) has a good prospect in electric vehicles, ship propulsion, aerospace and other fields due to the advantages of low voltage, high power, low speed and high torque. In this study, a six‐phase DDPMSM is proposed with 60° phase‐belt toroidal winding configuration (60°‐TW). Different from traditional overlapping windings, each coil of 60°‐TW is wound onto the stator yoke in the same direction. The topology of the proposed motor is introduced, and its operation principle is analysed by describing the variation of the magnetic field produced by the six‐phase 60°‐TW versus time. Meanwhile, based on the same power grade and effective volume, the six‐phase PMSM and dual‐three phase PMSM with different winding arrangements are designed. The magnetic field distribution, back‐EMF, cogging torque, torque and loss characteristics are explored in detail. The results show that the proposed six‐phase DDPMSM with 60°‐TW has the characteristics of low speed and high torque in comparison to the traditional six‐phase PMSM and dual‐three phase PMSM, which is expected for direct‐drive systems. [ABSTRACT FROM AUTHOR]

Inter‐turn short‐circuit fault (ISF) degrades its reliability and may cause serious catastrophes for direct‐drive permanent magnet synchronous motor (DDPMSM). Fault location technology can reduce maintenance time, increase the mean time between failure (MTBF), and then improve the reliability of DDPMSM. Hence, an intelligent fault locating system for DDPMSM is proposed in this paper. This system proposes a knowledge graph (KG) based diagnostic tool for detection and location of the fault coil. First, the fault model of the DDPMSM with multiple branches parallel winding is established, which is used to analyze the fault characteristics of motor. Second, the BDC and BRC are proposed as the fault indicator. The effectiveness and robustness of fault indicator are analyzed. Then, the KG system are designed and established according to the relationship between fault indicator and location of fault coil. Finally, the system is tested by data under different fault and operation conditions. The test results showed that the proposed fault locating system can detect and locate the fault coil in early stage. The minimum ratio of shorted turns to branch turns that can be detected is 0.52%. The minimum ratio of shorted turns to branch turns that can be located is 6.25%. [ABSTRACT FROM AUTHOR]

This paper investigates the influence of stator slots and rotor pole pairs combinations on torque performances in rotor permanent magnet flux switching (RPM-FS) machines. Based on a magnetomotive force (MMF) permeance model, the candidates of stator slots and rotor pole pairs combinations with higher torque capability can be determined by analyzing the PM-MMF and winding factor. Meanwhile, the candidates with a lower torque ripple can be obtained by referring to the cogging torque, which is related to the greatest common divisor of stator slots and rotor pole pairs. In addition, from the field modulation principle, the RPM-FS machines with the same fundamental magnetic loadings and winding factors exhibit identical fundamental harmonic torque, but different modulation harmonic components. Finally, four candidates with attractive torque performance are chosen, and the characteristics are verified by finite-element analysis and experiments. [ABSTRACT FROM AUTHOR]

The long stator of linear synchronous reluctance motor (LSynRM) consists only of low‐cost permeable material. Hence, LSynRM has a good application prospect in long‐distance drive systems. What about the electromagnetic performance of LSynRM under the constraints of installation size of rail transit? What are the advantages of LSynRM compared with the existing linear induction motor (LIM)? Research is non‐existent in academic circles. The purpose of this study is to compare LSynRM with LIM used in rail transit and give a comprehensive evaluation. First, a LIM used in Guangzhou Metro was analysed. Second, the working principle of LSynRM was analysed, and the selection principles of key parameters were determined. On this basis, the relevant parameters were optimized by using two‐dimensional finite‐element analysis (FEA) software. Then, the output characteristics of LIM and LSynRM were compared. The influence of ferrite on LSynRM was explored in view of the low power factor. The influence of winding end effect is explored through three‐dimensional FEA. The thrust force and power factor of LSynRM are corrected and the model is adjusted. Finally, the system cost and energy consumption of the two motors based on Guangzhou Metro Line 4 were estimated and compared in detail. [ABSTRACT FROM AUTHOR]

This paper presents a novel analytical method (NAM) of inductance identification for a direct drive permanent magnet synchronous motor (DDPMSM) with a stator winding fault (SWF), which considers the spatial position of the shorted turns. First, the structure of the DDPMSM is introduced and its key parameters are reported. Second, the NAM on the inductance identification is elaborated. The inductance analytical expressions of the faulty coil are derived in detail, in which the inductances of the faulty coil and the fault branch can be quickly calculated according to the spatial position coordinates of fault turns. Then, the model of DDPMSM with SWF is established. Finally, using the NAM, finite-element method (FEM), and the simplified analytical method (SAM), the inductances of the faulty coil and the branch are calculated under different fault conditions. Additionally, the fault current of the faulty coil is also studied, where the value of the fault current reflects the fault severity. The comparisons among the FEM, NAM, and SAM show that the accuracy of the NAM is higher than that of the SAM. [ABSTRACT FROM AUTHOR]

In this paper, the characteristics of the helical motion of the rotatory-linear 2-degree-of-freedom split-stator induction motor (2DoFSSIM) are investigated, which cannot be regarded as the simple superimposition of the 1DoF rotary and linear motions. A set of torque and force equations of the helical motion is deduced. It illustrates that the interacting electromagnetic torque and force are opposite to the directions of rotary and axial movements, respectively. For the rotating movement, the interacting torque is related to the axial velocity. Moreover, the axial velocity significantly influences the output torque performances and no-load speed. Similar conclusions can be obtained for axial movement of the helical motion. The 3-D finite-element method is applied to calculate the exact output performance considering the interacting influence. Furthermore, the prototype machine is manufactured and tested to verify the analytical results. [ABSTRACT FROM AUTHOR]

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

Two‐degree‐of‐freedom motors are capable of producing linear, rotary, and helical motion, and thus have widespread applications in special industries. In this study, a new concept – static coupling effect – is studied in the two‐degree‐of‐freedom direct‐drive induction motor (2DoFDDIM). The proposed approach is based on the image method and the three‐dimensional (3D) finite‐element method. The image method model is established to analyse its reasons and predict the main effects, which are then verified by the proposed 3D finite‐element static coupling model and experiments. The induced voltages and currents are produced in the static part and induced torque or force is obtained, even though the static part is not energised. It is concluded that the static coupling effect increases with the supply frequency and is influenced by the stator winding configuration. Thus, the existence of the static coupling effect is confirmed, which must be taken into account in future optimisation and precise control of the 2DoFDDIM. [ABSTRACT FROM AUTHOR]

This study presents a composite multilayer method (CMM) to evaluate the performance of a two‐degree‐of‐freedom (2DoF) direct drive induction motor (2DoFDDIM) whose solid rotor is coated with a copper layer. It includes a rotary part and a linear part. Based on the traditional multilayer theory, a complete 2DoFDDIM CMM computer program importing propagation constants is built. Due to the complex magnetic field in a 2DoFDDIM, this study mainly analyses it from the perspective of a single DOF motor. An equivalent circuit for the rotary part of the 2DoFDDIM is then derived applying CMM and the 2D magnetic field distribution is obtained by solving Maxwell's equations in motor layers. The developed torques, power factors and stator currents of the rotary part with different slips and the latter two of the linear part at zero speed are calculated by CMM, which are then compared with results from the finite element method (FEM) and experimental results. The computation time of the CMM is far less than that of the FEM. The acceptable accuracy confirms the effectiveness of the CMM for analysis and performance calculations of the 2DoFDDIM. [ABSTRACT FROM AUTHOR]