Flux Permanent Magnet Research Articles

Effects of electric and magnetic fields on dielectric and elastic properties of membranes composed of cotton fabric and carbonyl iron microparticles

This study investigates the influences of electric and magnetic fields applied both separately and superimposed on the dielectric and elastic properties of membranes (Ms) composed of cotton fabric and carbonyl iron microparticles (CI). To this end, three membranes were fabricated: one without CI microparticles and the remaining two with various proportions of CI microparticles. Additionally, scanning electron microscopy and energy emission X-ray spectroscopy were used to perform morphological and elemental analysis of the cotton fabric sample, CI microparticles, and the prepared Ms. Subsequently, flat capacitors (FCs) were manufactured using these Ms, encapsulated in a silicone rubber sheath. The FCs were introduced in static electric and magnetic fields superimposed over a sinusoidal electric field of frequency f = 1 kHz, and the electric capacity Cpand the tangent of dielectric loss angle Dpof the FCs were measured, depending on the E values of the static electric and magnetic fields superimposed over the medium-frequency electrical field. The values of the static electric field intensity and magnetic flux density were varied in steps of 4 kV/m within an interval 0 ≤ E (kV/m) ≤ 48 and in steps of 100 mT within an interval 0 ≤ B (mT) ≤ 300, respectively. Based on the obtained data, the components of the complex dielectric permittivity, those of the deformations, and the coefficients of elasticity of the Ms were determined to characterize the dependence of these values on the composition of Ms under the applied fields. Furthermore, the observed physical mechanisms were described based on the elements of physics of linear dielectrics and small deformation theory. Ultimately, the development of these materials can aid the design of various electrical devices for diverse applications such as sensors with electric field transducer, magnetic field, vibrations, and mechanical deformations.

Anti-Demagnetization Analysis of Fractional Slot Concentrated Windings Interior Permanent Magnet Motor Considering Effect of Rotor Design Parameters

This work investigates the effect of design parameters of permanent magnets (PMs) and flux barriers (FBs) in the rotor on the anti-demagnetization ability (ADA) of fractional slot concentrated windings interior PM (IPM) motors for electric scooters. A 2.5 kW IPM motor (12 slots and 8 poles) is designed for a wide speed range, and its ADA associated with different PM and FB arrangements is studied under high temperature and high current density operations. The analysis shows the relationship between the ADA and characteristic current (<inline-formula> <tex-math notation="LaTeX">$I_{\mathrm {ch}}$ </tex-math></inline-formula>, defined as the ratio of PM flux linkage to <inline-formula> <tex-math notation="LaTeX">$d$ </tex-math></inline-formula>-axis inductance). It is also found that proper designs of FBs can significantly improve the ADA of the IPM motor without much affecting <inline-formula> <tex-math notation="LaTeX">$I_{\mathrm {ch}}$ </tex-math></inline-formula>. Thus, the motor ADA and performance can be simultaneously improved. Finite element analysis is used for evaluation, and experiments are conducted to validate the analysis.

A New Harmonic Current Injection Technique to Reduce Cogging Torque in Axial Flux Permanent Magnet Motors

In this article, a new two-stage harmonic current injection (TSHCI) technique is proposed for permanent magnet (PM) synchronous machines to reduce the cogging torque and torque ripple components at low speeds. The developed algorithm is validated for two different axial flux PM (AFPM) motors experimentally. It has been shown that the proposed technique help reduce the cogging components of axial gap disk motors significantly especially at very low speeds.

Hybrid Excited Synchronous Machines

Hybrid excited synchronous machines (HESMs) combine permanent-magnet (PM) excitation and wound field (WF) excitation. The goal of hybrid excitation is to combine the advantages of PM excited machines and WF synchronous machines. HESM have been identified as one of the emerging technologies for modern energy conversion systems. They have been the subject of many review articles. The principle of hybrid excitation allows solving many drawbacks related to PM electric machines operation: flux weakening, energy efficiency, and PMs price fluctuation. It helps to introduce an additional degree of freedom in the design of synchronous machines, and allows therefore an easier adaptation of PM synchronous machines to a wider applications scope. To this additional degree corresponds the possibility of adjusting the contribution of the two magnetic field sources: PM and WF. The use of this technology for electric traction has been the subject of many scientific and technical contributions. In this contribution, the emphasis will be put on the use of these machines as generators in transportation applications and renewable energy applications. The design and operation of three particular structures will be presented. Two of them have been designed as generators for transportation applications, and the third one has been designed as generator for renewable energy conversion. All of them are flux switching hybrid excited synchronous machines (FSHESM).

An Improved Deadbeat Current Controller of PMSM Based on Bilinear Discretization

Based on the bilinear discretization mathematical model of permanent magnet synchronous motor (PMSM), an improved incremental deadbeat current prediction control algorithm is proposed. Aiming at the system instability caused by the forward Euler discretization method, this paper combines the deadbeat current prediction control and the improved bilinear discretization method to improve the system stability. Further, the proposed controller considers the two-beat delay of a digital system to make the mathematical model more accurate. Moreover, the proposed bilinear discretization predictive current controller is not affected by the permanent magnet flux of the motor. Then, the system stability conditions of the proposed controller are analyzed. The simulation and experimental results verify the feasibility and effectiveness of the proposed method.

Analytical Investigation and Heuristic Optimization of Surface Mounted Permanent Magnet Machines With Hybrid Magnetic Structure

Cogging torque causes major operational setbacks for Permanent Magnet (PM) machine operation, particularly in applications where a quiet performance is desired. This paper presents a heuristic optimization framework to optimize the cogging torque in Surface Mounted Permanent Magnet (SPM) machines consisting of a hybrid magnetic structure (i.e., rare-earth and ferrite magnets). To avoid excessive computational time and volume associated with Finite Element (FE)-based optimization solutions, analytical approach is paired up with the optimization algorithm to determine the optimal design while FE is utilized for verification and validation purposes. First, analytical expressions are established for individual objective functions (i.e., airgap PM flux distribution, and cogging torque), and their corresponding spatial harmonics are identified using the air-gap field modulation theory. Next, the presented analytical model is utilized to optimize the system (i.e., minimize the cogging torque) to the desired target level via two different solutions (i.e., Genetic Algorithm (GA) and Particle Swarm Optimization (PSO)), and their respective performance are compared. To determine the efficacy of the presented solutions, the optimal hybrid machine response is compared against the baseline structure.

Compensating Thermal Derated Torque of IPMSM Centric Electric Vehicles

A novel control approach based on Linear Parameter Varying (LPV) is designed for Electric Vehicles (EVs) to address the crucial challenge of torque derating. A high fidelity Interior Permanent Magnet Synchronous Motor (IPMSM) based EV is modelled by taking into account the influence of temperature. A closed loop torque compensation control architecture with LPV based Field Oriented Control (FOC) has been designed to mitigate the thermal effects. In order to curtail deteriorating of FOC due to parameter variation, a robust LPV observer has been proposed to estimate the degraded Permanent Magnet (PM) flux linkage and instantaneous torque production caused by uncertainties in stator resistance arises due to thermal effects. A LPV gain scheduling robust current controller for inner control loop of FOC has also been designed which ensures internal stability. The LPV observer-controller gains are computed by solving Linear Matrix Inequalities (LMIs) using convex optimization and singular value decomposition. The experiments simulations have been performed for EV operation against the Worldwide Harmonized Light Vehicles Test Procedure (WLTP) class 3, New European Driving Cycle (NEDC) and Federal Test Procedure (FTP) driving cycles considering thermal effects in Matlab/Simulink. The efficacy of proposed control architecture for managing the derating torque of IPMSM based EV is demonstrated through the validity of results and detailed data analysis. The LPV based FOC is compared with conventional FOC control counterpart. The comparative experiments simulation results show that the overall Mean Square Error (MSE) value is exponentially reduced which establish superiority of the proposed control scheme.

Investigation of Stator/Rotor Pole Number Combinations and PM Numbers in Consequent-Pole Hybrid Excited Flux Reversal Machine

This paper investigates the influence of stator/rotor pole number combinations and permanent magnet (PM) numbers on electromagnetic performance of consequent-pole hybrid excited flux reversal machines (CP-HEFRMs), which have different numbers of PM poles and iron poles and concentrated AC and DC windings on the stator and a salient pole rotor. PMs in the slots of one stator pole are magnetized radially in the same direction, while opposite on adjacent stator poles. Magnetic field paths of DC, PM, and hybrid excitations are investigated. The phenomenon of flux cancellation, i.e., PM and DC MMFs in CP-HEFRMs are of opposite polarities in the flux-enhancing operating mode, is revealed and verified, for the first time, as the key feature that makes CP-HEFRMs different from other hybrid excited machines. Consequently, the saturation in stator pole and yoke can be mitigated and hence the overload capability of DC excitation is enhanced, which is verified by finite element analysis (FEA). Global optimizations are utilized to obtain the optimal rotor and stator pole number combinations and PM numbers for each stator pole. Torque, torque ripple, inductance, unbalanced magnetic force, and flux regulation capability are compared for different PM numbers and rotor pole numbers. Comparisons are made on consequent-pole and non-consequent-pole topologies in terms of torque capacity, flux regulation capability, and PM consumption to further illustrate the advantages of consequent-pole topology. A prototype machine is built and tested to validate the analyses.

A Comparative Study of Dual Stator With Novel Dual Rotor Permanent Magnet Flux Switching Generator for Counter Rotating Wind Turbine Applications

Compared with the single rotor wind turbine, a counter-rotating (CR) wind turbine with two rotor sets leads to twice power density. In this regard, dual stator CR (DSCR) permanent magnet flux switching generator (DSCR-PMFSG) is employed. However, in DSCR-PMFSG both rotor and armature parts are rotating and require slip rings for power transmission. These slip rings associate demerits of constant maintenance, poor speed regulation, increased cost, and additional slip ring losses, whereas DSCR-PMFSG offer lower flux and lesser power density. To overcome the demerits of DSCR-PMFSG as mentioned earlier, this paper proposed a novel dual rotor counter-rotating permanent magnet flux switching generator (DRCR-PMFSG) for wind turbine applications that eliminate the requirements of slip rings and retain brushless operation. The proposed DRCR-PMFSG share one stator connected back-to-back through a flux bridge that provides an alternate flux path between two mechanical ports associated with the inner rotor and outer rotor, contributing to the cumulative output. A detailed comparative analysis of DSCR-PMFSG and DRCR-PMFSG is performed under static characteristics, overload, and wide speed range to generate output power, voltage, current, power density, and efficiency. Quantitative comparative analysis under static analysis evident that proposed DRCR-PMFSG exhibits 33.29% higher flux, suppressed cogging torque and torque ripples up to 53.48% and 67.45%, respectively. Furthermore, a comprehensive quantitative analysis is performed under coupled overload and over-speed capability. Analysis exposes that in comparison with DSCRP-PMFSG, the proposed DRCR-PMFSG improves voltage regulation factor by 55.88%, output current enhanced by 67.9%, raise output voltage to 2.01 times, and power density to 1.72 times while maintaining the efficiency of 90.195% and achieving stable voltage profile with load variation. Finally, a detailed comparative analysis with conventional designs is performed and comprehensive mathematical modelling based on sub-domain model is developed accounting stator slot and rotor pole combinations, magnetic saturation, and winding configuration to validates finite element analysis (FEA) of JMAG Designer v.20.1.

A Novel Dual Rotor Permanent Magnet Flux Switching Generator for Counter Rotating Wind Turbine Applications

In this paper counter rotating (CR) dual rotor permanent magnet flux switching generator (CR-DRPMFSG) is designed and relatively studied with co- rotating DRPMFSG (CoR-DRPMFSG) for wind turbine applications. The developed CR- DRPMFSG and CoR-DRPMFSG share same stator linked with flux bridge which provide flux route. A comprehensive relative assessment of both CR- DRPMFSG and CoR-DRPMFSG are presented with static attributes, over-load, and over-speed capability for generating output voltage, output current, output power, power density, losses, and efficiency. Comparative study with static characteristics illustrates that developed CR- DRPMFSG shows 34.34% elevated phase flux which improve output power, cumulative output torque is improved by 23.86%, and suppressed cogging torque by 66.87% at CoR-DRPMFSG that results lower pulsation in instantaneous torque. Furthermore, a detailed performance analysis is investigated with different number of armature winding turns per phase and combined over-load and over-speed capability. Study discloses that in contrast with CoR-DRPMFSG, counterpart CR- DRPMFSG offer 27.17% higher output power that results 1.25 times power density with a good voltage regulation factor of 18.67%. In additional, despite of 2.27% improvement of efficiency in case of phase winding turns analysis and 4.81% increase in over-load and over-speed capability, contour efficiency map unveils that CR- DRPMFSG offer wide range of higher efficiency operating region during over-load and over-speed condition accompany with stable voltage profile with load variation.

Phase-Variable Modeling and Comparative Study between a PMa-CPA and a CPA Alternator by Simulation Analysis

This paper presents the phase-variable modeling of a permanent magnet-assisted claw-pole alternator in PSIM simulation software tool with the performance compared with a claw-pole alternator model, which is a special case of the permanent magnet-assisted claw-pole alternator model with the rotor permanent-magnet flux constant setting equal to zero. The constructed model can be simulated as a real alternator directly connected to a diode-bridge rectifier or switch-mode rectifier circuit for the integrated power application system simulation analysis. The proposed model contains two features, one of which is that the stator and rotor windings are circuit-based. The other one feature is that the mechanical torque input is based on a mathematical function. In this model, the rotor position-dependent variable inductor is replaced by a separate voltage source according to the voltage source absorption theorem. The simulation shows that the proposed model has faster torque step response and higher power efficiency than the claw-pole alternator model. The proposed model can be employed to the application of the control design and simulation study of voltage regulation in automobiles. The simulation results with 15-V command and the load sudden change verify the correction of the proposed model.

Parameter identification of interior permanent magnet synchronous based on local search-based hybrid genetic algorithm

A hybrid genetic algorithm (Is-hGA) parameter identification method based on local search was proposed to solve the anti-salient characteristics of interior permanent magnet synchronous motor (IPMSM) and the defects of traditional genetic algorithm (GA) parameter identification method. In this hybrid optimization method, genetic algorithm is used for global search and hill-climbing algorithm is used for local search. This can not only improve the poor local search ability of genetic algorithm, but also greatly save calculation time. This method can identify four parameters of stator resistance, d-q axis inductance and permanent magnet flux linkage simultaneously. The performance of traditional GA and proposed Is-hGA in IPMSM parameter identification is compared by constructing an experimental platform. As a result, the proposed method can have more accurate identification precise.

Electromagnetic torque prediction and harmonic reduction of interior permanent magnet synchronous motor for electric vehicles using an analytical method

Interior permanent magnet synchronous motors (IPMSMs) have been widely used as drive machines in electric vehicles (EVs) due to their high torque density. However, the torque ripple of IPMSMs will result in severe noise and vibration. This paper proposes a new analytical method for electromagnetic torque prediction and harmonic reduction of IPMSM. On the basis of dq theory, an analytical model of electromagnetic torque is firstly established by taking the permanent magnet flux harmonics and the cross-coupling effect into consideration. And the specific sources and orders of torque harmonics are also determined. Then, the torque-angle characteristics are further studied. In particular, the permanent magnet (PM) torque and the reluctance torque are separated and quantitatively analyzed via the proposed analytical model. Finally, a theoretical method of reducing the specific order torque harmonic by PM shifting is derived and proposed from the perspective of avoiding resonance. The accuracy and effectiveness of the proposed analytical method are verified by finite-element analysis. The results show that the proposed analytical model is accurate enough to predict the electromagnetic torque performance of IPMSM. Moreover, the electromagnetic torque harmonics with specific orders can be effectively reduced by shifting the PM to an appropriate angle.

Design Method Based On Asymmetry Factor of a Novel Three-Pole Magnetic Bearing

Asymmetric three-pole magnetic bearings (MBs) have higher power density and lower cost, compared to the symmetrical magnetic bearings with four poles or eight poles. This paper presents a new asymmetric three-pole structure with secondary air-gap for a radial magnetic bearing. Asymmetric permanent magnet (PM) biased MB can produce a static levitation force by bias magnetic flux. The secondary air-gap can ensure that the armature winding flux and PM flux are separated. The configures of the proposed MB are demonstrated. Analytical model with equivalent magnetic circuit method is deduced. The design method based on asymmetry factor is proposed for the three-pole MB (TPMB). The characteristics of the TPMB such as magnetic flux distribution and magnetic levitation force are analyzed by the finite-element method (FEM). The design values and FEM results are compared to validate the effectiveness of the presented design method.

Analysis of Influence of Stator and Rotor Pole Shape on Electromagnetic Performance of Flux Switching Motor With Segmental Rotor

According to the relationship between the stator and rotor structure and magnetic flux density of the traditional flux switching motor with segmental rotor (SFSM), the mathematical model of the SFSM was established. It was found that the height of the stator pole shoe has a great influence on the no-load electromagnetic characteristics of the motor. After the flux barrier was added on the segmental rotor, it can effectively solve the problem that the positive and negative half period of the no-load electromotive force (EMF) waveform of the motor with low pole shoe height. Using the method of finite element (FEM) parametric simulation, the optimal size of the flux barrier was obtained. Compared with the traditional SFSM, the even harmonics in the phase winding EMF waveform were greatly reduced, and the inductance waveform tends to be sinusoidal. Finally, a prototype was made, and the correctness of the new segmental rotor structure was verified by experiments.

Design of the Six-Pole Hybrid Magnetic Bearing With Separated Magnetic Circuit to Generate Symmetrical Levitation Force

To solve the problem of generating the different two-degree-of-freedom (two-DOF) maximum levitation forces, a novel six-pole hybrid magnetic bearing (HMB), adopted combined stator and magnetic path structure, and its design method are proposed. Firstly, the configuration of the combined magnetic circuits and levitation principle are introduced. Then, the force-current relationships are derived. Furthermore, according to flux saturation, the permanent magnetic flux density is designed. Moreover, the combined magnetic circuit, force-current curves and design method are calculated and analyzed by Magnet 3D. Finally, the levitation forces are tested. The combined stator, levitation principle, force-current relationship and the design are proved to be correct.

End Effect Analysis of a Slot-Less Long-Stator Permanent Magnet Linear Synchronous Motor

The implications of the end effect for flux linkage and thrust ripple in a slot-less long-stator permanent magnet linear synchronous motor (LSPMLSM), are analyzed in this paper. Since it is affected by the end effect, the air-gap magnetic field density under the end permanent magnet is different from that under the non-end permanent magnet, leading to asymmetry in the thrust ripple. For this reason, we establish a dynamic permanent magnet flux linkage model, which proves that the end effect leads to sub-harmonics in the permanent magnet flux linkage. The motor’s magnetic field distribution in the left and right parts is symmetrical. A thrust model taking into account the flux linkage sub-harmonics is established, from which the amplitude and period of the thrust ripple caused by the end effect can be calculated. There is no detent force for the slot-less LSPMLSM, and the end effect is the primary origin of the motor thrust ripple. In order to suppress the end effect, a method of increasing the end iron length is proposed, as a result of which the sub-harmonics in the flux linkage and the motor thrust ripple are effectively suppressed. Experimental and simulation results verify the results of this paper.

Leakage flux reduction of axial-flux switching PM machine by using HTS-disk

Nowadays, axial flux switching permanent magnet machines are attractive and widely used in direct drive applications because of their unique features. This paper proposes a high temperature superconductor (HTS) disk axial flux switching permanent magnet (AFSPM) machine with spoke type permanent magnets (PMs) and three-phase two layers concentrated windings. The novelty of the proposed machine is using HTS material on the rotor and stator as a disk, insignificant relative permeability of the HTS materials causes magnetic reluctance to become extreme. Because of this feature HTS-Disk in the proposed HTS-AFSPM machine does not allow the flux to enter or exit which causes leakage flux reduces. In order to better investigate and fair comparison, all analyses have done at the same condition using the finite element method (FEM) by Ansys Maxwell. The comparison results show that the proposed HTS-Disk AFSPM machine achieves higher back-EMF, permanent magnet (PM) flux, flux distribution, lower inductance and losses and fewer total harmonics distribution compared to conventional AFSPM machine.

Analysis of a bearingless switched reluctance motor with permanent magnets in the stator yoke

Because a rotor has no permanent magnet and low manufacturing cost, a bearingless switched reluctance motor (BSRM) has unique advantages in medical and health, biochemical reactions, and other applications that need to be abandoned after single use or require the system to deal with high-temperature fluid. By analyzing the topological characteristics of a BSRM, rotor suspension and the mechanism of operation were described. A finite element model of a BSRM with a permanent magnet in the stator yoke (BSRM-PMSY) was established. The performance analysis of the BSRM was emphasized. The airgap flux distribution, no-load permanent magnet flux linkage, and torque of the motor were analyzed under zero load back-electromagnetic flow signals and levitation forces. The results verify that the optimization effect of the new motor on the levitation force is correct and a favorable decoupling control effect is found between the torque and levitation force, which provides the basis for efficient control of the subsequent prototype.

Analysis of a New Linear Dual Stator Consequent Pole Halbach Array Flux Reversal Machine

The permanent magnet machine has attracted much attention due to its high torque density at low speed and simple configuration. This feature is due to many magnetic pole pairs that flux in the air gap can be significantly changed with the smallest motion of the moving. In this paper, a linear dual stator flux reversal permanent magnet machine (LDSFRPMM) with toroidal winding is presented, which magnets embedded with Halbach and simple array on the translator and stator, respectively. The innovation of this structure over a conventional machine is the addition of a magnet between the stator teeth with the appropriate magnetic orientation, and finding the best width of permanent magnet on the stator and a change of the type of winding from the concentrated to the toroidal. By implementing these changes on a conventional machine, the main parameters of the machine such as back electromotive force (EMF), thrust force, power factor and permanent magnetic (PM) flux are increased which improves the performance of the proposed machine.