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This study presents a fault coil localisation approach for a direct‐drive permanent magnet synchronous motor (DDPMSM) with inter‐turn short‐circuit fault (ISF) using the search coil (SC) array. The SCs are wound around specific stator tooth of DDPMSM through the proposed SC array arrangement principle, which reduces the invasiveness of the fault coil localisation method. The SCs are classified as several search coil groups (SCGs), the differential between SC back electromotive forces (EMFs) in the same SCGs (δ1) and SC residual back EMF (δ2) are used as fault indicators for ISF localisation. The peak values extracted from δ1 and δ2 are the basis for diagnosing ISF. Hence, the proposed approach does not need a complicated signal processing algorithm, and it is less complex. First, the SC back EMF analytical model is developed to investigate the mapping relationship between the back EMF of each SC and fault coil location. Second, fault coil localisation indicators for ISF are analysed based on the proposed analytical model, and the exact ISF localisation approach is presented. Finally, two basic installation units and the arrangement principle of SC array in DDPMSM are proposed. Simulation and experimental results justify the effectiveness of the selected fault indicators and the feasibility of the proposed SC array for diagnosing ISF. [ABSTRACT FROM AUTHOR]

The three‐phase permanent magnet synchronous motor (three‐phase PMSM) has gained much popularity in many applications due to its various advantages. In addition, due to the good fault tolerance, simple inverter circuit structure and high torque density, the six‐phase PMSM has better prospects than three‐phase PMSM in biomedical devices, electric vehicles and other fields with high reliability requirements. In this study, a six‐phase axial‐flux PMSM inherently without cogging torque is proposed to improve torque density, which equips the 60° phase‐belt toroidal winding (60°TW) and slotless stator core. Based on the same effective volume, permanent magnet material, power grade and the other major motor parameters, two six‐phase PMSMs with 30° phase‐belt toroidal winding (30°TW) and 60°TW are designed, respectively. The armature reaction field, air gap magnetic density, back‐electromotive force, output torque, loss characteristic and torque‐speed characteristic are compared by using three‐dimensional (3D) finite‐element models in detail. Finally, the experimental test is carried out using the prototype of three‐phase PMSM with 120° phase‐belt toroidal winding. The experimental results indirectly verify the feasibility of 60° phase‐belt toroidal winding and correctness of 3D FEM. The 3D FEM analysis results are presented to show that torque density of the proposed six‐phase PMSM with 60°TW is improved in comparison to the six‐phase PMSM with 30°TW. Index Terms—60° phase‐belt toroidal winding, axial flux, six‐phase permanent magnet synchronous motor, torque density [ABSTRACT FROM AUTHOR]

A permanent magnet synchronous motor (PMSM) is introduced with 120° phase belts toroidal windings (PBTWs) (120°PBTWPMSM), in which its armature reaction field principle is elaborated. Then, the experiment concerning the 120°PBTWPMSM is conducted to verify the validity of the related analysis and the feasibility of the 120°PBTWPMSM. In addition, a method of shifting the magnetic poles (SMP) is adopted to suppress the cogging torque and the torque ripple. After this, the 120°PBTWPMSM after SMP is further optimised by the Taguchi method to obtain the structural parameters of the motor with optimal comprehensive performance. Finally, the performance of the original motor, the 120°PBTWPMSM after SMP and the optimal motor are compared, which verify the effectiveness of the optimization methods. [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]

Owing to its many benefits, including convenient and short computing time, the analytical model (AM) is widely used in the performance analyse of the permanent magnet synchronous motor (PMSM). The existing analytical models based on phase winding cannot sufficiently speculate about the contribution of the coil to the performances of direct‐drive PMSM (DDPMSM) with series coils and multiple branches. Hence, in this work, a novel AM for the DDPMSM is proposed. This model, which is based on the winding sub‐element, can analyse the influence of coil on motor performance. First, the structure and key parameters of the DDPMSM are reported. Second, an inductance matrix, which considers the spatial disposition of coils and the characteristics of large self‐inductance and small mutual inductance, is constructed. Then, the influence of the coil on motor performance is analysed based on the proposed AM. Finally, the results of AM, finite‐element model and experiment are compared. The results validate the correctness of the proposed AM. Furthermore, the proposed AM can speculate about the contribution of a coil in the DDPMSM performances with satisfactory accuracy. [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]

It is crucial to calculate the levitation force and model the levitation behaviour in the designation of superconducting magnetic bearing (SMB). At present, the related research focuses on the single degree of freedom (DoF) levitation behaviour of the SMB independently, for instance the axial or radial levitation force. Practically, the superconducting magnetic levitation is passive levitation at directions of multi‐DoF. Additionally, the non‐ideal conditions in fabrication, such as the joint effect of superconducting bulks, lead to complex 3‐D‐induced current distributions which generate the levitation force. There are coupling effects which affect the levitation forces at the directions of different DoFs. This paper investigates the multi‐DoF modelling and levitation behaviour of the radial‐type SMB. By adopting the Power‐law E‐J relation, the dependence of conductivity on electric field is derived to define the superconductive material. Then, the software MagNet is employed to establish the 3‐D multi‐DoF finite element model. Under the external disturbance of the PM rotor with axial constant speed and constant load, the multi‐DoF levitation behaviours of radial‐type SMB are discussed considering the joint effect of superconducting bulks. It is also obtained that the influence of the revolving speed, the static, and dynamic eccentricity on the axial levitation force. [ABSTRACT FROM AUTHOR]

Owing to its many benefits, including a high power density, high accuracy, and smooth feeding, the permanent magnet linear synchronous motor (PMLSM) is widely used in many industrial applications. However, the power‐angle curve of the PMLSM has an obvious left deviation phenomenon, which affects the performance of the PMLSM. Hence, in this study, the basic reasons and critical conditions for the deviation are investigated. First, the cause of the deviation is analysed, and a finite‐element model is established to verify the analytical results. Then, using an analytical method, the critical condition of the power‐angle deviation for a PMLSM is determined. Finally, a prototype of a PMLSM is manufactured, and the simulated and experimental results are compared to verify the conclusion. The good comparison results validate the conclusion of this study. This research on the power‐angle characteristics of the PMLSM will provide a significant reference for the design research and precise control of PMLSMs. [ABSTRACT FROM AUTHOR]

The coupling between the rotary and linear magnetic fields is a special feature of two‐degrees‐of‐freedom (2DoF) motors. The magnetic‐coupling effect on the performances of 2DoF direct‐drive induction motors (2DoF‐DDIMs) is exposed and investigated based on 3D finite‐element analysis and experiments on a prototyped motor. The performances of the 2DoF‐DDIM are analysed under the conditions of with and without coupling. Further, the speed coupling coefficient is introduced and calculated to consider the effect of the magnetic‐coupling effect on speed. The magnetic‐coupling effect of 2DoF‐DDIM, which leads to induced voltages and currents under rotary or linear motion and lower speed and higher fluctuations under helical motion, enhances with an increase in the source frequency and rotary speed. This research on the magnetic‐coupling effect of 2DoF‐DDIM will provide a significant reference for characteristic research and precise control of 2DoF‐DDIM. [ABSTRACT FROM AUTHOR]

Two degree‐of‐freedom direct drive induction motor (2DoFDDIM), capable of rotary, linear and helical motion, has widespread application. A new mover structure is proposed, which is made from a hollow cylinder with copper cast in the axial slots and the circumferential slots on its surface. Then, three‐dimensional finite element models of 2DoFDDIM are used to determine the performances of rotary, linear and helical motion developed by the motor. The results show that the new mover has a great improvement on the motor performances of all modes of motions compared with the initial mover. The researches on mover structure and characteristics of 2DoFDDIM present a new path of optimisation on 2DoFIM. [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]