Flux-switching Permanent Magnet Motor Research Articles

Suppression of Torque Ripple of a Flux-Switching Permanent Magnet Motor in Perspective of Flux-Modulation Principle

In this article, the suppression mechanism of torque ripple for the flux-switching permanent magnet (FSPM) motor is investigated. According to the flux modulation principle, the generation principle of torque harmonics is analyzed, which is generated by the interaction between the radial and tangential airgap harmonics. Based on the analysis, a method to suppress the torque ripple of the FSPM motor is proposed, where the airgap harmonics are newly applied to be the bridge to establish the relationship among torque ripple, torque harmonic components, and key design parameters. To confirm the effectiveness of the proposed method, an FSPM motor with the V-shape permanent magnet (VS-FSPM) motor is selected as the research example. The leading torque harmonics and leading airgap harmonics of the VS-FSPM motor are picked out effectively. Some key design parameters are selected according to the flux modulation principle to improve the leading airgap harmonics and reduce the corresponding torque ripple successively. Furthermore, the torque ripples of the initial and improved VS-FSPM motor are calculated and compared in detail. Finally, a prototype motor is built and tested. Both the theoretical analysis and experimental results verify the effectiveness of the proposed new method.

Modeling and Analysis of Dual-Winding Bearingless Flux-Switching Permanent Magnet Motor Considering Magnetic Saturation Based on Subdomain Model

Dual-winding bearingless flux-switching permanent magnet machine (BFSPMM) is composed of power winding and suspension winding. The permanent magnet and the power winding provide a biased air gap magnetic field, and the suspension winding generates an air gap modulation magnetic field. The structure of stator and rotor are double salient poles. This paper proposes a subdomain model for the on-load field prediction in dual-winding BFSPMM. In the developed model, the field domain is divided into seven types of subdomains, viz. rotor slot, internal air gap, stator slot, permanent magnet slot upper layer, permanent magnet slot lower layer, permanent magnet, and external air gap. The electromagnetic parameters of the motor are analyzed, including air gap flux density, flux linkage, back-EMF, suspension forces, and electromagnetic torque. Based on the principle of conservation of magnetomotive force, a distributed equivalent magnetic circuit model is proposed to compensate for the magnetic saturation. Finally, the analytical predictions are verified by finite-element analysis and prototype experiments.

A dynamic model for the investigation of twisting effect in long flux‐ switching PM motors in ESPs

Shaft twisting occurs along the length of electric motors rotors. The twisting depends on the shaft properties and the transmitted torque. In Electrical Submersible Pumps, due to the high ratio of length to the diameter of the motor and the high load torque, the twisting effect occurs significantly. Thus, when such a condition emerges for an electric motor, the electromagnetic torque is not uniformly produced along the motor length, since shaft twisting results in rotor position variation with respect to the stator. Therefore, the twisting and the produced electromagnetic torque of the motor are interdependent. It means that these two issues cannot be studied separately and a model must be proposed to consider them together so that the electromagnetic performance of the motor can be studied under such conditions. Despite the importance of modeling the twisting effect for the electric motor, this issue has never been investigated before. In this article, a novel dynamic model for the flux-switching permanent magnet motor is proposed by which the shaft twisting effect is simulated to study the motor performance. Eventually, the twisting effect during startup and steady-state are studied as well as the effect of shaft diameter and motor length on shaft twisting. To evaluate the model, it is compared with the verified steady-state model for the flux-switching permanent magnet motor with the twisted shaft obtained from another article, and also results obtained by finite element analysis.

Performance optimisation of a segmented outer rotor flux switching permanent magnet motor for direct drive washing machine application

Electrical machines are widely used in home appliances, the performance of which is mostly related to the quality function of the electrical machines. What has been used so far in home appliances brought with themselves a wide assortment of advantages and disadvantages. With the aim to overcome the drawbacks of the previously implemented electrical motors in washing machines, a new configuration of flux switching permanent magnet motor (FSPM) with the segmented outer rotor (SOR-FSPM) is proposed benefitting from a direct driven drum. To reduce the cogging torque as well as torque ripple and to improve the total harmonic distortion, cutting the stator in a way to lower overlapping between the rotor and stator pole, inserting notches into the poles of the rotor to modify the air gap between the stator teeth and the rotor segments are proposed. The Taguchi method and sensitivity analysis are further applied to find the best combination set of changes in such a way to smoothen the chart showing reluctance between stator and rotor and fix the zero-point crossing of the flux linkages in different rotor positions. Finally, the proposed SOR-FSPM is prototyped, and experimental results along with the finite element method results are discussed and compared in order to verify the design process.

Design and Analysis of Dual Mover Multi-Tooth Permanent Magnet Flux Switching Machine for Ropeless Elevator Applications

A dual mover yokeless multi-tooth (DMYMT) permanent magnet flux switching motor (PM-FSM) design is presented in this article for ropeless elevator applications. The excitation sources, including a field winding and permanent magnet, are on the short mover in the proposed design structure, whereas the stator is a simple slotted iron core, thus reducing the vertical transportation system cost. The operational principle of the proposed DMYMT in PM-FSM is introduced. The proposed dual mover yokeless multi-tooth Permanent Magnet Flux Switching Motor is analyzed and compared for various performance parameters in a Finite Element Analysis package. The proposed machine has high thrust force and cost-effectiveness compared to conventional dual permanent magnet motor. Finally, this paper also develops an analytical model for the proposed structure, validated by comparing it with Finite Element Analysis simulation results. Results show good agreement between analytical prediction and Finite Element Analysis results.

전기 자전거에 적합한 스포크 형 및 자속 교번 영구자석 전동기 설계와 특성 비교

In this paper, a spoke-type interior permanent magnet synchronous motor(IPMSM) and a flux switching permanent magnet(FSPM) using ferrite magnet designed for electric bicycles and compare the advantages and disadvantages of the two motors. The motors were optimized in the same design order and the efficiency map was analyzed to verify the performance of each driving section. From the results, the FSPM motor is cheaper, but the performance is lower than the spoke-type IPMSM, and the performance is excellent only at high speed. Therefore, the spoke-type IPMSM, which has good average efficiency in all driving areas, is more suitable for electric bicycles.

Research on Detent Force Characteristics of a Linear Flux-Switching Permanent-Magnet Motor

Linear flux-switching permanent-magnet (LFSPM) motors have been proposed for electromagnetic launch system (EMLS). Benefiting from the permanent magnet (PM) settled on the long double-sided primary and the yokeless secondary, the proposed structure has the advantage of high thrust force density and simple structure compared with the traditional linear permanent-magnet synchronous motor (LPMSM) and linear induction motor (LIM), which makes it more suitable for the EMLS. However, it suffers from the deficiency of relatively high detent force due to the permanent magnets (PMs) settled on the primary, which will also exert an influence on the thrust ripple. Different from the traditional rotary motor, the linear motor also suffers from the end force caused by the end effect. So, a new structure of secondary, which is called symmetric unequally spaced (SUS) secondary in this paper, is proposed to improve the electromagnetic performance from the point of the detent force and thrust ripple for the motor. The thrust ripple and detent force are effectively declined by applying the proposed method without the sacrifice of the average thrust force. The validity of the method is verified by finite element analysis (FEA). A prototype with SUS secondary is manufactured to verify the simulation result.

Fault-Tolerant Operation Control Strategy for Combined Winding Bearingless Flux-Switching Permanent Magnet Motor Drive System With One Opened Phase

The failure of the inverter bridge arm or the open circuit of the phase winding may occur during the operation of a combined winding bearingless flux-switching motor, causing both rotor rotation and suspension to malfunction, hence fault-tolerant control is vital for the motor's reliability and stability. In this paper, a fault-tolerant operation control strategy for combined winding bearingless flux-switching permanent magnet motors under open-circuit fault condition is proposed. Firstly, how to control the electromagnetic torque and suspension force acting on the rotor with the combined winding structure is explained, and then the mathematical models of the torque and suspension force which can be controlled individually by different current components are deduced in detail. Afterward, the relation of the phase current without and with winding fault is discussed, and the operation conditions of maintaining constant torque and suspension force after fault are demonstrated. Whereupon, the fault-tolerant control block diagram is constructed. Finally, the experimental results are presented to demonstrate the performance of the proposed strategy.

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.

An Improved Sub-Domain Model of Flux Switching Permanent Magnet Machines Considering Harmonic Analysis and Slot Shape

The flux switching permanent magnet motor is a kind of double-salient machine with good speed regulation performances and application prospects. However, in traditional sub-domain models which are used to exactly calculate the magnetic field of the flux switching permanent magnet motor, the orders of major harmonics can not be intuitively obtained. The computational efficiency and practicality of the sub-domain models are limited. Meanwhile, some errors are caused in the equivalent process of iron slot shapes. Aiming at these problems, an improved sub-domain model is proposed in this paper. The major magnetic field harmonics are selected in advance for each sub-domain region by the magnetic permeance function model of the air gap. In addition, the influence of the slot shape equivalence is corrected by the magnetic permeability of slots, and the accuracy of the sub-domain calculation is improved. The proposed model is verified to have the advantages of high accuracy and fast computing speeds by 2-D finite element analysis. A convenient and reliable approach for flux switching permanent magnet motor designs is provided thereby.

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).

Comparative Study of E- and U-core Modular Dual-Stator Axial-Field Flux-Switching Permanent Magnet Motors With Different Stator/Rotor-Pole Combinations Based on Flux Modulation Principle

In this paper, the dual-stator axial-field flux-switching permanent magnet (DSAFFSPM) motors with E- and U-core stator modular segments, as well as different stator/rotor-pole combinations are compared. The operation performance of the DSAFFSPM machines are explored by using the MMF-permeance model method. A more comprehensive theoretical analysis, no more limited to numerical calculation, is presented. This reveals directly the relations between the operation performance and design parameters of the machine. The performance comparisons between the E-shaped and U-shaped teeth DSAFFSPM machines are given, including the effects of the structural parameters on the electromagnetic torque, different stator/rotor-pole combinations on the winding factor and gear ratio, the differences of the average torque and the torque density and the efficiency in the 12/10 U-core and 6/10 E-core topology. These are the basis of the DSAFFSPM machine design and optimization. Finally, the experiments on the two prototype, 6/10 E-core and 12/10 U-core DSAFFSPM machines are carried out. The results show that the average torque of the 12/10 U-core prototype is higher than that of the 6/10 E-core prototype, while the torque density and the efficiency of 6/10 E-core DSAFFSPM machines are much higher.

Application of Magnetic Metal 3-D Printing on the Integration of Axial-Flow Impeller Fan Motor Design

This article aims to implement a fan motor design with an airfoil-shaped rotor via the newly developed 3-D printing method. This integrated design is originated from a flux-switching permanent magnet motor, in which the motor rotor can directly produce airflow without any external impellers. Such a design and manufacturing process can effectively enhance the robustness of the fan motor structure and increase its power density. This article adopts 3-D finite element analysis for electromagnetic and fluid field simulation. Moreover, a new metal 3-D printing method with a low core loss feature during high frequency operation is applied. Finally, the experimental results with a prototype are presented to verify the designed performance.

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.

Introducing a novel FSPM motor with double rotor and toroidal windings

In this study, a new flux-switching permanent-magnet (FSPM) motor with two rotors and toroidal coil are introduced. First, the proposed FSPM (PFSPM) motor structure and performance principles are presented. Then, the performance parameters of the PFSPM motor, including flux linkage, back-electromotive force, air-gap flux distribution, inductance, eddy current loss, cogging torque and the output electromagnetic torque are compared with a conventional FSPM motor based on finite-element analysis. Then, the effect of the angle between the two-rotor poles on the performance parameters of the PFSPM motor is indicated. Finally, the PFSPM motor model is manufactured and the results of the finite-element test are compared with the results of the experimental test and the accuracy of the finite-element model is confirmed.

Permanent Magnet Parameter Design and Performance Analysis of Bearingless Flux Switching Permanent Magnet Motor

Since the bearingless flux switching permanent magnet motor has a doubly salient pole structure of conventional flux switching permanent magnet motor, there are many problems, such as high cogging torque, high torque ripple, and the magnetic flux leakage produced by PMs, which affect the characteristics of the electromagnetic torque and suspension force. To overcome the shortcomings above, a novel method-right angle chamfering scheme, is investigated to reduce the cogging torque. Firstly, based on the given rated speed and rated power, the parameter ranges of the angle variables at both ends of the permanent magnets are designed by the empirical formulas. Then, under the condition that the torque and the power are reduced in allowable ranges, the electromagnetic characteristics, such as cogging torque, harmonic, electromagnetic torque, radial suspension force, and decoupling, are simulated and analyzed in detail. Based on the proposed design method, the compromise design of the above design objectives is considered and realized. Finally, the scheme of stator and rotor component is built, and the experimental results show that the effectiveness and feasibility of the scheme are verified.

Detent Force Minimization of a Tubular Flux-Switching Permanent Magnet Motor Using Un-Equal Width Stator Slots Based on Taguchi Method

The detent force caused by the cogging effect and end effect will seriously affect the operation of a tubular flux-switching permanent magnet motor (TFSPMM). This paper proposes a method to weaken the end effect and minimize the detent force and force ripple of a TFSPMM using un-equal width stator slots. To overcome the problem of excessive calculation, the Taguchi method is performed to find the optimal combination of stators with unequal slot width. The proposed method can significantly decrease the detent force and force ripple and keep the thrust force basically unchanged. The permanent magnet flux linkage, detent force and electromagnetic force are calculated by the two dimensional (2D) finite element method (FEM).

A Double-Rotor Flux-Switching Permanent-Magnet Motor for Electric Vehicles With Magnetic Differential

In this article, a novel double-rotor flux-switching permanent-magnet (DR-FSPM) motor is proposed for electric vehicles with the capability of magnetic differential (MagD). The key is to introduce a new set of winding, which magnetically couples with the two rotors of the DR-FSPM motor in such a way that the magnetic coupling winding field can interact with the PM fields in the two rotors. Hence, the differential torque can be generated between wheels to achieve accurate cornering during vehicle steering. Consequently, the proposed system can offer higher efficiency and compactness than the conventional mechanical differential system, while providing higher reliability and safer operation than the electronic differential system. The operation principle and performances of the proposed DR-FSPM motor are thoroughly analyzed by finite element analysis while the proposed MagD system is also evaluated with system simulation. Finally, the motor prototype is built while the prototype and MagD system are tested for experimental verification.

Comparative Study of Permanent Magnet Assisted Linear Switched Reluctance Motor and Linear Flux Switching Permanent Magnet Motor for Railway Transportation

Linear switched reluctance motor (LSRM) has been investigated and supposed as a good candidate in railway system. Recently, permanent magnet assisted switched reluctance motor (PMA-SRM) has attracted extensive attention because of the high torque, robust structure and low cost. However, all these researches focus on the application of small air gaps. How does PMA-SRM perform in large air gap? No research has been conducted until now. As we know, there are many similarities between linear flux switching permanent magnet (LFSPM) motor and permanent magnet assisted linear switched reluctance motor (PMA-LSRM) such as similar primary iron, winding structure, robust secondary and a small amount of permanent magnets. In this case, what are the similarities and differences between these two kinds of motors in terms of electromagnetic characteristics? This paper will compare these two kinds of motors based on the volume of rail transit from the following aspects: thrust force, thrust ripple, efficiency. First, the topology, operation principle of the two LSRMs are introduced and designed. Then, the electromagnetic performance of LSRM is optimized through two dimensional finite element analysis (FEA) based on ANSYS software. The optimization objectives of PMA-LSRM are to maximize the thrust and to minimize the ripple at the given dimensions and the rated condition. The comparison of electromagnetic characteristics between LFSPM motor and PMA-LSRM is completed. Finally, it is concluded that the permanent magnets are not conducive to improving the power of LSRM. And the PMA-LSRM is not outstanding compared with LFSPM motor under the condition of large air gap for rail transit.