Reduce Leakage Flux Research Articles

Design and Quantitative Analysis of Asymmetric Flux Reversal Permanent Magnet Linear Machine With Reduced Leakage Flux

Design and Quantitative Analysis of Asymmetric Flux Reversal Permanent Magnet Linear Machine With Reduced Leakage Flux

Comparative analysis and optimization design of dual-side-permanent-magnet Halbach array vernier machine for high torque density

PurposeThe purpose of this paper is to introduce and analyze a dual-side-permanent-magnet Halbach array vernier (DSPMHV) machine and to propose methods for achieving high torque density.Design/methodology/approachFlux harmonics and torque characteristics are analyzed by using finite element analysis. First, a suitable pole-slot combination is selected by comparison. Second, field modulation processes of DSPMHV machine are analyzed to identify the reason for high torque density. And it is compared with dual-side-PM (DSPM) machine to analyze flux harmonic and verify the flux concentrating effect of the Halbach array.FindingsThe permanent magnet (PM) field of the DSPM machine is approximately equal to the superposition of stator-PM field and rotor-PM field, which is the reason for high torque density. And the Halbach array can reduce flux leakage and increase the amplitude of main flux harmonics, then further improves torque. Improvement of torque can be achieved by choosing right pole-slot combination, adopting DSPM machine structure, reducing flux leakage and adopting field modulation principle.Originality/valueThe DSPMHV machine with split-tooth is proposed in this paper by combining the Halbach array with DSPM structure. This paper analyzes the bidirectional field modulation process, the reason for high torque density of the DSPM machine is obtained. Comparison with the DSPM machine verifies the flux concentrating effect of Halbach array. To alleviate the magnetic saturation in part of stator teeth, this paper proposes an improved DSPMHV machine with shaped auxiliary magnet.

Micromachined Two-Dimensional Weak Magnetic Field Sensors of Soft Magnetic Film/Planar Coil Laminated

Two-dimensional magnetic sensors of soft magnetic film/planar coil laminated have outstanding advantages in miniaturization and integration. However, due to the cumbersome process and complicated structure of the sensor, its yield rate is extremely low, and the gap between magnetic films is large, resulting in increased leakage flux and low sensitivity. Therefore, a high-performance soft magnetic film with through-holes/ planar coil laminated micro-magnetic sensor with mutual inductance is designed and the sensor is fabricated by Micro-Electro-Mechanical System technology. The micro-magnetic sensor can be processed in 15 steps, with a yield rate of more than 95%, and the gap between magnetic films can be effectively reduced, resulting in reduced leakage flux and improved sensitivity. Moreover, the effect of coil resistance is eliminated, the noise level of the proposed mutual inductance micro-magnetic sensor is reduced and the detectivity can be significantly enhanced. The experiment result shows that the sensitivity of the proposed mutual inductance micro-magnetic sensor is 46.5 mV/Oe in the range of 0 Oe~0.3 Oe, the voltage noise is as low as 0.8 μV/√Hz, and the noise level reaches 17.2 μOe/√Hz. Therefore, the detectivity of the proposed mutual inductance micro-magnetic sensor can reach 17.2 μOe (1.72 nT), which has significant potential in several areas, such as biosensing and geomagnetic navigation.

A Novel Slot-PM Assisted Complementary-Rotor Doubly Salient Machine With Enhanced Torque Performance

This article presents a novel doubly salient permanent magnet (DSPM) machine with enhanced torque performance. The key is that an assistive magnetic flux is produced by using two sets of slot PMs inserted into the slot openings, which can effectively improve the torque production. Besides, a complementary magnetic path is built by dual rotors with 180° angle shift to reduce leakage flux, which can effectively suppress the torque ripple. In this article, the proposed machine design is presented, including working principle, winding configuration, magnetic path analysis. Then, the Genetic Algorithm is used to find the optimal designs for the proposed machine. Further, to verify the effectiveness of the proposed machine, three doubly salient machines are compared, including the proposed machine, a DSPM machine without assistive slot PM design, and a dual-rotor DSPM machine without complementary rotor structure. Finally, a prototype of the proposed machine is built and tested to verify the validity of the proposed machine design.

Design and Analysis of a High Torque Density Hybrid Permanent Magnet Excited Vernier Machine

Permanent magnet (PM) excited vernier machines capable of high torque density have good potential for electric vehicles while requiring high rare earth PM consumption. To achieve a high torque density at a reasonable material cost, hybrid PM excited vernier machines incorporating both expensive rare earth and low-cost ferrite magnets are investigated in this paper. Various combinations of PM arrangements for the hybrid permanent magnet excited vernier machine are investigated to acquire low cost and superior torque density. The best solution obtained is that the PM on the stator adopts rare earth material while the rotor uses ferrite. Furthermore, the PMs on the stator are arranged in an iron-cored Halbach array, which can reduce leakage flux and enhance flux density effectively and the ferrite PMs are used in the rotor, therefore, high-temperature demagnetization is avoided. Then, the reluctance torque and the cogging torque can offset each other effectively, which is beneficial to reducing the torque ripple and smoothing the electromagnetic torque. Finally, a prototype is manufactured and tested to verify the correctness of the theoretical analysis.

Ironsand (Titanomagnetite-Titanohematite): Chemistry, Magnetic Properties and Direct Applications for Wireless Power Transfer.

Ironsand is an abundant and inexpensive magnetic mineral resource. However, the magnetic properties of unprocessed ironsand are often inadequate for any practical applications. In this work, the applicability of ironsand for use as a component in a soft magnetic composite for large-scale inductive power transfer applications was investigated. After magnetic separation, the chemical, structural and magnetic properties of ironsand sourced from different locations were compared. Differences observed in the DC magnetic properties were consistent with changes in the chemical compositions obtained from X-ray Absorption Near-Edge Spectroscopy (XANES), which suggests varying the titanohematite to titanomagnetite content. Increased content in titanomagnetite and magnetic permeability correlated well with the total Fe content in the materials. The best-performing ironsand with the highest permeability and lowest core losses was used alongside Mn,Zn-Ferrite particles (ranging from ∼100 m to 2 mm) to fabricate toroid cores with varying magnetic material loading. It was shown that ironsand can be used to replace up to 15 wt.% of the magnetic materials with minimal impact on the composite magnetic performance, thus reducing the cost. Ironsand was also used as a supporting material in a single-rail wireless power transfer system, effectively increasing the power transfer, demonstrating potential applications to reduce flux leakage.

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.

Analytical validation of novel consequent pole E‐core stator permanent magnet flux switching machine

Flux switching machines (FSMs) encompass unique features of conventional direct current machine, permanent magnet (PM) synchronous machine and switch reluctance machine. Permanent magnet FSM (PMFSM) is capable of high torque density and applicable for high-speed application, however conventional PMFSM exhibits demerits of high PM volume, high torque ripples and significant stator flux leakage. In this paper, a novel consequent pole E-core stator PMFSM is proposed and compared with conventional topology utilising 2D finite-element analysis (2D-FEA). Finite-element analysis revealed that proposed design enhanced flux modulation effects by introducing flux bridges and flux barriers as a result reduced cogging torque by reducing 46.53% of the total PM volume, reduce torque ripples by reducing PM slot effects and reduce flux leakage utilising flux bridges in the stator. Furthermore, analytical model for flux linkages, cogging torque, mechanical torque, no load and on-load magnetic flux density (MFD) is developed for initial design of conventional and proposed model. 2D analytical methodologies resolve equivalent magnetic circuits for open-circuit flux linkages, Fourier analysis for cogging torque, Laplace equations for MFD and Maxwell stress tensor for mechanical torque. Finally, results obtained from 2D-FEA and analytical methodologies are validated and compared.

A fully coreless Multi-Stator Multi-Rotor (MSMR) AFPM generator with combination of conventional and Halbach magnet arrays

An axial flux permanent magnet (AFPM) generator is known to be a good candidate for both low and high-speed application. In this paper, a new design of fully coreless multi-stator multi-rotor (MSMR) AFPM generator has been presented with conventional and Halbach magnet arrangement combined with an ironless (epoxy) rotor. For MSMR topology of AFPM machine, back iron is still present in the middle rotor and to maintain the same distribution of magnetic flux, magnets are using on both side of the middle rotor. This paper suggests replacing the middle iron rotors with a single epoxy rotor which reduces the weight of the machine, hence increase power density. On the other hand, for the elimination of iron and magnets in the middle rotor, conventional magnet arrays are used to maintain a continuous flux path. In addition, Halbach array is adopted on the external epoxy rotor to reduce flux leakage on the external sides of the machine. The performance of the proposed generator is investigated in terms of voltage, current, power, power density, and torque ripple. The analytical design approach is first presented and subsequently validated using ANSYS Maxwell® electromagnetic finite element analysis (FEA) software. It is found that a fully coreless MSMR AFPM generator with conventional and Halbach magnet arrays gives higher power density and lower torque ripple with a reduced axial length which is favorable in wind power and pico-hydro applications.

A Novel Spoke-Type PM Machine Employing Asymmetric Modular Consequent-Pole Rotor

This paper proposes a novel spoke-type permanent magnet (PM) machine, which adopts asymmetric modular consequent-pole (AMCP) rotor to enhance the effective PM flux due to the increased flux-focusing effect and reduced leakage flux and to improve the flux-weakening capability due to the increased d -axis inductance. Moreover, the pole-shaping method based on three sectional arcs is proposed to suppress the harmonics of airgap flux density. Since the rotor structure is relatively complex, the finite-element analysis together with multiobjective genetic algorithm is adopted to optimize this design. Furthermore, the electromagnetic performance of the spoke-type PM machine with the proposed AMCP rotor (Spoke-AMCP), including the open-circuit airgap flux density, phase back electromotive force, torque, PM utilization ratio, efficiency, and flux-weakening capability, are compared with two conventional spoke-type PM machines with evenly distributed and alternate flux barriers (Spoke1 and Spoke2) and consequent-pole spoke-type PM machine (Spoke-CP). It is demonstrated that the Spoke-AMCP machine obtains the largest output torque and PM utilization ratio, lowest torque ripple and similar efficiency compared to Spoke1, Spoke2 and Spoke-CP machines. Moreover, although the Spoke-AMCP machine has the largest PM flux linkage, it has slightly better flux-weakening capability than the Spoke1 and Spoke2 machines. Finally, a 12-slot/10-pole Spoke-AMCP machine is built and tested to verify the analyses.

Properties of a magnetic concrete core transformer for application in wireless power transfer systems

A combination of ferrimagnetic and ferromagnetic inclusions were blended within a diamagnetic Portland cement matrix to increase bulk relative permeability for possible application in wireless power transfer. The objective of this study is to quantify the interactive flux exchange coupling between ferritic inclusions of different composition, shape, size, volume fraction, core geometry, and coil winding configuration. Cores made of cement mortar and various combinations of ferrimagnetic and ferromagnetic inclusions were cast and the permeability was quantified. A total of 21 different mix combinations were considered. ANOVA was used to assess the level of significance of each individual inclusion and their interaction with each other with respect to relative magnetic permeability. X-Ray diffraction, thermogravimetric analysis, and mechanical compression tests were also completed. The results suggest that powder and fibrous ferritic inclusions at a volume fraction greater than 10% can reduce flux leakage, reduce hysteresis core loss, and significantly increase relative permeability. A steel reinforced magnetic concrete CI core can achieve a peak flux of 100 mT and relative permeability of 28 when the cement matrix contains 20% volume fraction of ferritic fiber and powder inclusions.

A Novel Method for Field Analysis and Design of Electromagnet Used in Lifting Applications

Magnetic crane is one of the industrial applications of magnetic absorption, which uses an electromagnet to create the necessary force for lifting and moving objects. In this paper, the field analysis and design of an electromagnet are discussed. During the electromagnet analysis and design process, with special attention to leakage fluxes and fringing effects, a new magnetic equivalent circuit for an electromagnet is proposed. Also, the nonlinear behavior of the B-H curve of the ferromagnetic core and its saturation point are considered. Due to the various shapes of the ferromagnetic core, the U_I structure is selected with a symmetrical winding to reduce leakage flux and fringing effects. MATLAB software is used for analyzing and designing the electromagnet, and ANSYS Maxwell software is used to simulate its magnetic field. To verify the accuracy of the proposed method, the prototype was made of a magnetic crane with designed electromagnet. The comparison between measurement and simulation results shows that the error is less than 2%, which confirms the accuracy of the proposed method.

Optimal Design of an Ultra-Premium-Efficiency PMA-Synchronous Reluctance Motor With the Winding Method and Stator Parameters to Reduce Flux Leakage and Minimize Torque Pulsations

In this paper, the optimal design for a permanent magnet-assisted synchronous reluctance motor (PMA-SynRM) is proposed in terms of efficiency, maximum torque, and minimum torque pulsations. Design variables, objective functions, and constraints are selected for this optimal design, which is divided into two steps. Step I utilizes the pole/slot combination of the PMA-SynRM and winding methods. The chosen 4-pole/36-slot model with distributed winding maximizes the rated efficiency. In Step II, the optimal design of the stator parameters is obtained using the response surface method and the precise torque and torque ripple are calculated using the finite-element analysis (FEA). The proposed stator slot openings are minimized to minimize the air-gap flux leakage, and consequently, realize a smooth electromagnetic torque. Finally, a few FEA results are validated by experimental results.

HTS Dual-Stator Spoke-Type Linear Vernier Machine for Leakage Flux Reduction

In this paper, a high-temperature superconductor dual-stator spoke-type linear vernier machine (HTS-DSSLVM) is proposed for wave energy extraction, which offers high-thrust force density and better power factor due to leakage flux reduction. HTS bulks are introduced in between the split flux modulation teeth to shield the leakage flux and hence improve the force density and power factor. The electromagnetic characteristics of the machine are comprehensively investigated and compared with that of a recently presented dual-stator spoke-type linear vernier machine (DSSLVM). The results show that the proposed machine yields higher thrust force and better power factor than the DSSLVM due to reduced leakage flux in the proposed machine.

The Ferrite Effect on Magnetic Field Distribution with Two Rotors and One Stator Machine Topology

The study of axial flux permanent magnet machine (AFPMM) has been increasingly interesting to develop, since its construction is simple, easy to make, cheap, and portable. The application of NdFeB having high density, widely available in market and low cost maintenance was beneficial as this machine was brushless so that it didn’t need routine maintenance. The results of many earlier researchers showed that there are still opportunities to improve engine performance. In this study, ferrite was used to collect and divert the magnetic flux, thereby reducing the magnetic flux leakage. This paper discussed ferrite installation technique in a cylinder and ring shape to direct magnetic flux circulation into closed circuit, and thus it could reduce leakage flux. This technique was performed on two rotors one stator topology using yhe finite element method for magnetic (FEMM) simulation. The simulation result presented magnetic field distribution on coil stator disc (1) without using ferrite having value of B = 364 to 379 mT (2) with ferrite core in coil having value of B = 399 to 419 mT (3) with ferrite core in each stator edges having value of B = 443 to 409 mT, and (4) with ferrite core both in coil and stator edges having the value of B = 467 to 446 mT.

Magnetic flux analysis and performance test of permanent magnet and claw-pole electromagnetic hybrid excitation generator for electric vehicle range extender

Developed hybrid excitation generator (HEG) has a tangential permanent magnet (PM) and claw-pole electromagnetic parallel combined rotor and a fractional-slot winding stator, which makes stator core eddy-loss and armature winding copper-loss less. By establishing the equivalent magnetic circuit model of each part of HEG and analysing permeance influence factors, magnetic isolation measures are taken to reduce flux leakage and improve output efficiency. The designed electromagnetic coupling regulator controller can ensure stable voltage export of HEG in a wide range of speeds and load states by changing quantity and direction of excitation current to adjust the size of air gap magnetic flux density. Performance test is done and results show that the output voltage is relatively stable. So the HEG can provide electric energy to battery and electrical equipment of vehicles.

Design and optimization of a surface mounted transverse flux permanent magnet machine

Transverse flux permanent magnet machine (TFPM) is well known for its achievable high torque density and flexible topologies, which makes it especially suitable for wind power generation, electric vehicle and direct drive area. Existing TFPM topologies, however, are subject to high flux leakage and cogging torque. This paper deals with the design and optimization of a three phase surface mounted transverse flux permanent machine (SM-TFPM) to reduce flux leakage and cogging torque, the solutions of adjusting the interval between magnets and inserting auxiliary stator are suggested to realize the restriction of both flux leakage and cogging torque. The finite element analysis (FEA) results show the obvious effects, and the FEA design is validated via prototype experiment by using TMS320F28335 based controller and induction machine load. Based on the abovementioned researches, a further multi-objective optimization is applied by using differential evolution (DE) algorithm and the optimization results are compared with the previous design to demonstrate the improved performance

A Novel Linear Permanent-Magnet Vernier Machine With Improved Force Performance

In this paper, a linear permanent-magnet vernier machine is proposed, in which both magnets and armature windings are placed in the short mover, while the long stator consists of an iron core only. Hence, it is suitable for long-stroke applications such as urban rail transit. The proposed machine integrates two magnetization directions of magnets together, which can reduce leakage flux and enhance flux density. Meanwhile, since different topologies and different slot/pole number combinations have an effect on the winding factor, several general rules are established. It is revealed that the thrust force ripple of the proposed machine is lower than its cogging force ripple, which is explained by a built analytical model. Both the analytical model and the finite-element results are validated by experiments based on a prototype machine.

Design of Novel Overhang Structure for Separated Pole-Piece Type Ferrite Magnet Motor

A separated pole-piece type ferrite magnet motor (FMM) is a novel type of motor that can maximize reluctance torque and reduce leakage flux by separating the pole pieces and the web. However, when this type of motor has a short stack length and a large area of pole pieces, the leakage flux in the axial direction has significant influence on the motor's performance. A rotor overhang structure is one of the most crucial design parameters that compensate for the side effects of leakage flux. A conventional overhang structure increases magnetic torque but raises the level of induced voltage. This limits the operation speed range. To overcome such problems, this paper presents a novel multilevel overhang structure. Based on the unique structure of the separated pole-piece type FMM, the overhang length of the pole pieces was set to be shorter than the other parts of the rotor. It was observed that the operating speed range was widened, and more reluctance torque was generated, compared to motors with conventional overhang structures. The proposed overhang structure was optimized by 3-D finite element analysis, and the model was validated by comparing the actual experimental results with its predicted performance.

Design of a 400 mH 400 A Toroid-Type HTS DC Reactor Magnet

Large electric power systems, such as high voltage direct current (HVDC) transmission systems, need dc reactors with large inductance and high transport current. Such systems experience a lot of electrical loss due to the resistance of their copper winding. Employing superconducting magnets for the reactors provides some advantages such as high current density, low electrical loss, and so on. This paper describes the design of a toroid-type high temperature superconductor (HTS) dc reactor magnet. The target inductance and the current level of the HTS dc reactor were 400 mH and 400 A, respectively. The toroid-type HTS magnet reduced leakage flux and increased the critical current of the reactors. The HTS dc reactors were designed using 2G HTS wires. The Finite Element Method was used for the design and analysis of the toroid-type HTS dc reactors.