Flux-switching Motor Research Articles

Optimization Design of a Novel Flux-Switching Transverse-Flux Permanent Magnet Tube Linear Motor

A novel flux-switching transverse-flux permanent magnet tube linear motor (FSTFPMTLM) with oblique air-gap is proposed in this article, which combined the merits of the tube linear motor, the transverse-flux linear motor, and the switched-flux linear motor. The structure and operating principle of the FSTFPMTLM is presented first. Considering this motor has a 3-D magnetic circuit and designing the motor with high performance, this article proposes an optimization method for the FSTFPMTLM by decomposing the design of the motor into two steps to separate optimization using experimental design method. The first step is to optimize the cross-section part of the motor. After that the optimized motor is compared with the initial one by finite element method (FEM). The prototype is then manufactured and tested.

A Novel Double-Sided High Temperature Superconducting Linear Modular Flux-Switching Motor

Double-Sided Linear Flux-Switching Permanent Magnet (DSLFSPM) motor has the merits of high efficiency, high power factor and low-cost stator structure. But the speed range of DSLFSPM is limited due to its adoption of permanent magnets. Double-Sided High Temperature Superconducting Linear Flux-Switching Motor (DSHTS-LFSM) adopts HTS coils to replace the permanent magnets, thus obtaining better power density and wider speed range. However, when the magnetic field gets much stronger, the iron core is easily saturated and flux leakage gets serious, which threatens the reliability of HTS coils and lowers the utilization of iron core. To solve this problem, a novel Double-Sided High Temperature Superconducting Linear Modular Flux-Switching Motor (DSHTS-LMFSM) is proposed. The armature windings are designed different from existing DSHTS-LFSMs to reduce flux leakage. Furthermore, by sealing the HTS coils together in a Dewar away from armature windings, the reliability is improved. In this paper, the structure and working principle of the proposed DSHTS-LMFSM is explained. The electromagnetic performance of it is calculated using Finite Element Method (FEM). As evaluation, its performance is compared against a traditional DSHTS-LFSM.

Comparative Investigation of High Temperature Superconducting Linear Flux-Switching Motor and High Temperature Superconducting Linear Switched Reluctance Motor for Urban Railway Transit

Both Linear Switched Reluctance Motor (LSRM) and Linear Flux-Switching Motor (LFSM) have the merits of none-adhesive thrust force and simple and robust secondary structures. Therefore, LSRM and LFSM are quite suitable for applications such as vertical lifting, wave power generation and urban railway transit. To further improve the power density of them, the field windings of LFSM and DC windings of LSRM can be replaced with High Temperature Superconducting (HTS) coils, and thus forming High Temperature Superconducting Linear Flux-Switching Motor (HTS-LFSM) and High Temperature Superconducting Linear Switched Reluctance Motor (HTS-LSRM). Despite their similar structure, they have different working principles and electromagnetic performances. To reveal their merits and drawbacks for urban railway transit system, a comparative investigation is conducted in this paper using Finite Element Method (FEM).

Reduction of Thrust Force Ripple of High Temperature Superconducting Linear Flux-Switching Motors using Asymmetry Mover Structure

Compared with traditional linear motors, such as Linear Permanent Magnet Motors (LPMs) and Linear Induction Motors (LIMs), Linear Flux-Switching Permanent Magnet (LFSPM) motors have the merits of high efficiency, power density, with simple and robotic secondary structure. Despite these advantages, the flux-weakening ability of LFSPM motor is limited and thus the speed range of it is not ideal. As a promising choice, it is feasible to replace the PMs of LFSPM motors with coils made with High Temperature Superconducting (HTS) tapes. By using HTS material, High Temperature Superconducting Linear Flux-Switching Motors (HTS-LFSMs) have good flux-weakening ability while inheriting the edges of LFSM motors. Since the existence of HTS coils, the cooling system has a minimum size and has to take up certain room of the motor. When it comes to applications where the volume of motor is strictly restrained, there may not be enough room for a basic pattern of typical pole pitch combinations for HTS-LFSM, such as 12-7 or 12-9, leading to large thrust ripple. To solve this problem, a method of reducing thrust force using asymmetry mover structure is proposed based on a 9-5 pole pitch ratio. The mechanism and working principle are analyzed and the validation is verified with the help of Finite Element Method (FEM).

Design and Evaluation of the Performance of an Integrated Flux-Switching Motor–Compressor With Airfoil-Shaped Rotor

The objective of this article is to propose the concept of and evaluate the potential performance of an integrated flux-switching permanent magnet (FSPM) motor-compressor that has rotor poles designed as airfoils to perform compression functions. The airfoil-shaped rotor functions as the rotor of both an electric motor and an axial-flow compressor. As a result, the integrated motor-compressor increases the compressor system compactness by eliminating the separation between the motor and compressor. In this article, the electromagnetic and thermodynamic designs are developed using sizing equations and mean line analysis. Four design configurations of the integrated motor-compressor are carried out and evaluated, including the continuous-skewed versus step-skewed structure and laminated steels versus soft magnetic composite (SMC) materials. The thermodynamic performance is calculated by mean line analysis and computational fluid dynamics (CFD). The electromagnetic performance and structural analysis are evaluated by finite element analysis (FEA). The comparisons of the integrated motor-compressor with conventional motor-driven compressors are conducted. Results from FEA and CFD verify the integrated motor-compressor.

Slot Filling Factor Calculation and Electromagnetic Performance of Single Phase Electrically Excited Flux Switching Motors

For variable speed applications, flux controlling capability of electrically excited flux switching motors (EEFSMs) attract researchers’ attention. However, low copper slot filling factor of the EEFSM with standard stator slot vitiates the electromagnetic performance and efficiency. This paper has proposed a new Octane Modular Stator (OMS) EEFSM model that has pentagonal stator slot and high copper slot filling factor. Copper slot filling factor is deliberated analytically for the proposed model and designs with standard stator slots, i.e., trapezoidal and rectangular. Electromagnetic performance of the OMS, Rectangular Stator Slot (RSS) and Trapezoidal Stator Slot (TSS) EEFSM designs are evaluated by finite element analysis (FEA) through JMAG v18.1 FEA solver. The proposed OMS EEFSM model has 9% higher copper slot filling factor in comparison with standard stator slots designs under same geometric parameters. The high copper slot filling factor of the proposed OMS EEFSM model has improved performance in term of low electric and magnetic loading.

Design and Implementation of Position Sensorless Field-Excited Flux-Switching Motor Drive Systems

Field-excited flux-switching motor drive systems have become more and more popular due to their robustness and lack of need for a permanent magnet. Three different types of predictive controllers, including a single-step predictive speed controller, a multi-step predictive speed controller, and a predictive current controller are proposed for sensorless flux-switching motor drive systems in this paper. By using a 1 kHz high-frequency sinusoidal voltage injected into the field winding and by measuring the a-b-c armature currents in the stator, an estimated rotor position that is near ± 2 electrical degrees is developed. To improve the dynamic responses of the field-excited flux-switching motor drive system, predictive controllers are employed. Experimental results demonstrate the proposed predictive controllers have better performance than PI controllers, including transient, load disturbance, and tracking responses. In addition, the adjustable speed range of the proposed drive system is from 4 r/min to 1500 r/min. A digital signal processor, TMS-320F-2808, is used as a control center to carry out the rotor position estimation and the predictive control algorithms. Measured results can validate the theoretical analysis to illustrate the practicability and correctness of the proposed method.

Performance comparisons of alternative permanent‐magnet motor designs for personal mobility‐assistive device applications

Demands of appropriate personal mobility-assistive devices for those needed persons have been increased considerably in recent years, with their specific operational requirements, developments of adequate motors to different device parts are the main concerns. For applications onto those knee joint parts of the exoskeleton system, three types of permanent-magnet (PM) motors, namely the surface-mounted PM motor, the Vernier motor, and the flux-switching motor were designed. Based on the operational and physical constraints of the particular exoskeleton parts, optimisations of these PM motors were provided along with their thorough performance comparisons. From emulated finite-element analyses along with hardware experimental validations, by following the standard test settings, selection guidance for the suitable motor structures at different operational objectives will thus be supplied.

Improvement of Model Predictive Current Control Sensing Strategy for a Developed Small Flux-Switching Permanent Magnet Motor.

This paper presents an improved control system for a small flux-switching permanent magnet motor (FSPM) to enhance its performance and torque sensing. The analytical magnetic circuit design was used to determine the related motor parameters, such as the air gap flux density, permeance coefficient (Pc), torque, winding turns, pole number, width, length, magnet geometry, and the current density of FSPM. The electromagnetic analysis of this motor was performed by software (ANSYS Maxwell) to optimize the motor performance. In this study, the performance of FSPM was investigated by the uniform design experimentation (UDE). For the control system, the model predictive current control (MPCC) is currently recognized as a high-performance control strategy, due to its quick response and simple principle. This model contained the nonlinear part of the system, to improve the torque ripple of FSPM. A modified MPCC strategy was proposed to improve the distortion of the current waveform and decrease the computational burden. The new modified control architecture was mainly composed of three parts, such as the estimation of electromotive force (EMF), current prediction, and optimal vector selection/vector duration. When the reference voltage vector was obtained, the three-phase duties were easily determined by the principle of space vector modulation (SVM). The results show the different strategy methods between the newly proposed modified MPCC and traditional proportional integral (PI) controller. In the control of FSPM, a modified MPCC strategy was able to achieve a better performance response and decrease the computational burden. At a low speed of 350 rpm, the proposed modified MPCC can achieve a better dynamic response. The nonlinear problem of the startup speed was also effectively resolved. The torque sensing performance of the simulation and the experimental test value were compared. The torque sensing performance of the simulation and the actual test value were also examined. In this study, the optimization focused not only on the motor design and fabrication, but also on an improved motor control strategy and torque sensing, in order to achieve the integrity of the FSPM system.

Investigation of High Temperature Superconducting Linear Flux-Switching Motors With Different Secondary Structures

Compared with Linear Induction Motor (LIM), which is widely adopted for urban railway transit system, Linear Flux-Switching Permanent Magnet (LFSPM) motor has the merits of high efficiency, power factor and simple secondary structure. Therefore, LFSPM motor is claimed to be promising for urban railway transit system. However, research shows that speed range of LFSPM motor is limited due to Permanent Magnets (PMs). But for Linear Wound Field Flux-Switching (LWFFS) motor, electromagnetic performance is influenced by the large airgap. To incorporate the merits of LWFFS motor and LFSPM motor, High Temperature Superconducting Linear Flux-Switching Motor (HTS-LFSM) is proposed. However, it remains unknown which secondary structure of HTS-LFSM is suitable for urban railway transit. Hence, two HTS-LFSMs of slotted and segmented secondaries are designed, optimized, compared and analyzed in this paper. Finite Element Method (FEM) is adopted to calculate their performance.

An On-Board Two-Stage Integrated Fast Battery Charger for EVs Based on a Five-Phase Hybrid-Excitation Flux-Switching Machine

In this article, to solve the existing problems in general on-board integrated chargers, a novel three-phase on-board two-stage integrated charger is proposed by taking the unique advantages of a five-phase hybrid-excitation flux-switching (HEFS) motor. The general topologies and newly presented integrated chargers are reviewed first, and existing problems are concluded. Then, a two-stage integrated charger is proposed, and all winding selections are thoroughly investigated by theoretical analysis, finite-element analysis (FEA), and experiments. In the proposed topology, the existing problems are all solved by employing this multiphase system, reasonable winding selection, and reconfiguring the field winding. After that, a current balance control method for charge mode without a phase-locked loop circuit is presented. The simulation results verify the effectiveness of the proposed control methods. Finally, based on a 5-kW five-phase HEFS prototype machine and two sets of the three-phase generic motor controller, an experiment platform is built. The experiment results agree well with the simulation results. Therefore, the feasibility of a two-stage integrated on-board charger that can operate at any voltage level is confirmed, where only the hybrid-exciting machine and its driving system are used without any additional power devices.

A Single-Phase On-Board Two-Stage Integrated Battery Charger for EVs Based on a Five-Phase Hybrid-Excitation Flux-Switching Machine

In this paper, to solve the existing problems in general on-board integrated chargers (IC), a novel single-phase on-board two-stage integrated charger is proposed by taking the unique advantages of the five-phase hybrid-excitation flux-switching (HEFS) motors. The general topologies and newly presented ICs are reviewed firstly, and three main problems are concluded. Then, the proposed two-stage IC is presented, and all winding selections are thoroughly investigated by theoretical analysis, finite-element analysis (FEA) and experiments. In the proposed topology, the existing problems are all solved by employing this multi-phase system, making the reasonable winding selection, and reconfiguring the field winding. After that, a control method for charge mode and two current balance control methods are developed. The simulation results verify the effectiveness of the proposed control methods. Finally, based on a 5-kW five-phase HEFS prototype machine and two sets of the 3-phase generic motor controller, an experiment platform is built. The experiment results agree well with the simulation results. Therefore, the feasibility of a two-stage integrated on-board charger that can operate at any voltage level is confirmed, where only the hybrid-exciting machine and its own driving system are used without any additional power devices.

Low-Loss-Design of a Flux-Switching Motor Considering Air-Gap Harmonics

In this paper, a new low-loss-design method based on MMF harmonics is proposed for a flux-switching permanent magnet (FSPM) motor. By analytical method, the relationship between permanent magnet loss and air-gap harmonics caused by magneticmotive force (MMF) is deduced theoretically. By introducing a loss impact factor, the correlation designs among the impact factor, PM loss, torque and cogging torque are carried out to realize the PM loss reduction with comprehensively optimal motor performances. By utilizing finite-element method, the electromagnetic performances of initial and optimal motor are analyzed and compared in detail, consisting of PM loss and torque performances. Finally, theoretical analysis and simulation results verify the effectiveness of the proposed design method and motor.

Performance Evaluation of Flux-Switching Permanent Magnet with Modifications to Stator and Rotor

A flux-switching motor is a synchronous electric motor in which both field and armature coils are placed on the stator. There are thus three different stator structure types with regard to field excitation: permanent magnet, direct current field excitation, and hybrid. The rotor structure of the motor in this study reflected two types: integrated and multi-piece structure. The permanent magnet flux switching motor with integrated rotor structure offers more advantages and more attention has been paid to this as compared to other electric motors in various industries. The major advantages of this type are high torque density, ease of manufacture, high reliability, and robustness of rotor. However, these flux switching motors have relatively high cogging torque, and while work has been done on reducing the cogging torque and some literature published, most such works have focused on modifying the rotor tooth, skewing the rotor. These works study the effect of rotor shaping on motor performance, while in this paper, new rotor shapes are also considered. Finally, a method is introduced to minimise the cogging torque that has least adverse effect on other effective parameters such as torque density. Using the results of other papers, the finite element method is used to find the best method of rotor shaping in this paper.

Establishment of a New Dual Rotor Flux Switching Motor Magnetic Circuit Model and Optimization of No-Load Back EMF

A novel double rotor flux switching motor with a better output torque performance is proposed. The equivalent magnetic circuit model and the simplified equivalent magnetic circuit model of the motor are established, and the equations for calculating the main flux and the main flux density of the motor are derived. Finally, the Taguchi method is introduced into the optimization design of the dual rotor flux switching motor proposed in this article. A reasonable orthogonal test is designed. By comparison and analysis of the test results, it verifies that this optimization design can not only reduce the high-order harmonic content of no-load back electromotive force (EMF) but also improve the sinusoidal degree of no-load back EMF waveform.

Shaft twisting effect on steady state performance of flux switching motor with long rotor

Torque transmission along a shaft results in the shaft twisting which is negligible in the conventional motors. However, a long and thin shaft is subject to non-negligible twisting effect. This Phenomenon can affect the electromagnetic performance of the motor. In this article, the shaft twisting effect on the electromagnetic behavior of a flux-switching permanent magnet (FSPM) motor is studied. A model of an FSPM motor is proposed to study the electromagnetic performances of the motor. The electromagnetic torque and twisting rate of each point are calculated along the shaft. Then the model results are compared with finite element analysis results for a long motor.

Investigation of start-up conditions on electric submersible pump driven with flux switching motor

One of the motor types that is recently considered to be a candidate for electric submersible pumps (ESPs) is the flux switching motor. Therefore, it becomes crucial to verify that this type of motor can stand ESP conditions. The main subject of this paper is to investigate the start-up condition of ESP along with considering the long power supply cable to study the motor performance, where the real aspect of the ESP conditions is investigated. Since there is not any model of pump load that models the dynamic behavior of ESP correctly, first, a model for the pump is developed. Then the flux switching motor model is modified to apply the long cable to the model. The model is simulated and the results are presented. The main advantages of this paper are modeling the height change of fluid, pump efficiency, and pump load torque during the time (from start to steady state when the flow rate of fluid outcome from the well is stable), and considering the long cable. In addition, the flux switching motor model is validated by a built prototype motor.

Hybrid excitation flux switching motor with permanent magnet placed at middle of field coil slots and high filling factor windings

Design and experimental studies on a hybrid excitation flux switching motor as a traction motor for hybrid electric vehicles drive are presented. A stator body of the motor consists of not only laminated silicon-iron electromagnetic steel and three-phase armature windings, but also both of field excitation coils and permanent magnets working together as a variable field magnetomotive force source. On the other hand, a rotor is composed of just laminated silicon-iron electromagnetic steel with salient poles like switched reluctance motor. To bring out the best in drive performances of the hybrid excitation flux switching motor as a variable flux motor for the application, each material adopted for the stator and rotor body should be designed properly in terms of motor efficiency, maximum torque and power densities and so forth. As some of them, in this paper, thinner silicon-iron electromagnetic steel sheet and permanent magnets with high remanent and low amount of Dysprosium used are applied for achieving higher motor efficiency. Moreover, all coils wound flatwise and edgewise using rectangular wires are introduced to realizing high filling factor for reduced copper losses. Experimental tests using a 60kW prototype of the motor demonstrates the designed motor has good motor efficiency under frequent operating points expected for the target vehicle drive.

Electromagnetic Performances and Main Parameter Sensitivity Effect on Unbalance Magnetic Flux in a New Single-Phase FEFSM with Segmental Rotor

Three-phase field excitation flux switching motor (FEFSM) with salient rotor structure has been introduced with their advantages of rotor easy temperature elimination and controllable FEC magnetic flux. Yet, the salient rotor structure is found to lead a longer magnetic flux path between stator and rotor parts, producing a weak flux linkage along with low torque performances. Hence, a new structure of single-phase FEFSM using segmental rotor with non-overlap windings is proposed with advantages of shorter magnetic flux path, light weight and robust rotor structure. Analysis on fundamental magnetic flux characteristics, armature and FEC magnetic flux linkages, cogging torque, back-Emf, various torque capabilities, refinement of unbalance magnetic flux, and torque-power versus speed characteristics are conducted using 2D FEA through JMAG Designer version 15. The results show that magnetic flux amplitude ratio has been improved by 41.2% while the highest torque and power achieved are 1.45 Nm and 343.8 W, respectively.

Fault-Tolerant Field-Oriented Control of Three-Phase Induction Motor Based on Unified Feedforward Method

With the increasing proliferation of variable speed drive, the demand for the more reliable drive is also on the rise. Despite the growing interest on more advanced motors like permanent magnet and flux switching motors, three-phase induction motors (3ph-IMs) are still the main workhorse in the industry and hence the fault-tolerant control of these motor drives remains an interesting and important topic. In this paper, a simple fault-tolerant field-oriented control technique for 3ph-IMs is presented. It is shown that by injecting zero-sequence compensation voltage in a feedforward manner, open-circuit faults can be effectively tolerated. Compared to the previous feedforward fault-tolerant control methods, the proposed approach does not require the knowledge of the magnetizing inductance, which is tricky to be obtained in induction motors. Furthermore, the unified feedforward approach allows the same control structure to be used for different fault-tolerant 3ph-IMs drive topologies, with minor modifications to the feedforward terms. In addition, the effect of inverter non-idealities on the performance of the proposed control method is also highlighted and addressed. The effectiveness of the proposed controller is verified using MATLAB simulation and further validated using experimental tests. This paper is accompanied by a video demonstrating the experimental results.