Flux Permanent Magnet Research Articles

Research on Torque Performance of a Traction Motor by Using Fe-Co-V Soft Magnetic Alloys

As a device that realizes the “static-to-motion” transformation which influences the national economy and people’s livelihood, the electric machine (EM) has put forward higher requirements for the torque/power density with the development of industry. It is difficult to meet the new requirements by using traditional silicon steel. Therefore, the application of “new” materials has become a breakthrough point. This article studied the properties and the application of Fe-Co-V alloys (1J22) which has a high saturation magnetic polarization, then analyzed its performance in high torque density EMs. Since the stator field is a rotating magnetic field which changes with time, the variable-angle magnetic performance test was carried out on 1J22 to discuss the influence of the magnetic performance under different shear angles on the stator magnetic flux. The EM’s design and prototype production were carried out for the unique properties of the 1J22 material itself. Compared with the EM model using traditional non-grain-oriented (NGO) silicon steel 35ADG1900, the use of 1J22 material can solve the temperature rise problem under special working conditions. At the same time, the feasibility of 1J22 in high torque density traction motor has been verified.

Effect of Flux Barriers on Short-Circuit Current and Braking Torque in Dual Three-Phase PM Machine

This paper investigates the influence of stator flux barriers on the short-circuit current (SCC) and braking torque of a dual three-phase permanent magnet (PM) synchronous machine. By optimizing the position and width of stator flux barriers, the machine has a lower amplitude of short-circuit current and brake torque when the short-circuit fault occurs. First, the SCC and braking torque are analytically derived. The amplitude of SCC is proportional to the PM flux linkage and inversely proportional to the inductance. The braking torque is proportional to the square of the PM flux linkage and inversely proportional to inductance. Then, the equivalent magnetic circuit model of flux barriers is established. Its influence on flux linkage and inductance is analyzed, and the improvement mechanism of output torque and fault tolerance is revealed. Furthermore, the flux barriers’ width is optimized by finite element analysis and the theoretical analysis is verified. Finally, experiments on the prototype machine are carried out for the validation.

A Phase-Domain Model of Dual Three-Phase Segmented Powered Linear PMSM for Hardware-Assisted Real-Time Simulation

In this article, a hardware-assisted real-time simulation phase-domain (PD) model of a dual three-phase segmented powered linear permanent magnet synchronous machine (SP-LPMSM) used in electromagnetic drive is established. The model is able to consider the end-effect, saturation effect, coupling effect, and open-phase fault conditions, which are specially occurs in the segmented structure in SP-LPMSM. The unbalanced inductances and saturation effect caused by the segmented structure are investigated and a simplified look-up table for inductances is introduced. Additionally, to accurately evaluate the coupling effect, the permanent magnet (PM) flux linkage is decoupled into the product of unit PM flux linkage and coupling coefficient. In order to avoid the numerical impulse caused by the derivative in the progress of calculating back-EMF, sigmoid function is adopted to express the coupling coefficient. Meanwhile, to make the PD-model compatible with the open-circuit fault conditions, incidence matrices and current constraint matrices are introduced to unify the PD-models with different winding connection types and open circuit faults into one general form. The PD-model realized in field-programmable gate arrays (FPGA) based hardware is validated in comparison with finite-element analysis results.

Computationally Efficient Analytical Model of Interior Permanent Magnet Machines Considering Stator Slotting Effects

Subdomain modeling is among the most reliable and accurate analytical tools for designing and analyzing permanent magnet machines. However, the application of the two-dimensional (2-D) subdomain model is mainly limited to permanent magnet machines with homogeneous rotor structures (with uniform permeability), such as surface-mounted or surface-inset permanent magnet machines. Solving Maxwell's equations and applying 2-D boundary conditions on structures with permanent magnets embedded in the rotor core, such as interior permanent magnet machines, are quite complex. Given the importance of enabling the tangential field component to capture accurate results, a 2-D hybrid analytical solution is proposed and applied to a multilayer interior permanent magnet machine. For this purpose, the radial components of the permanent magnet flux and the armature flux are first calculated using the magnetic circuit and the magnetic islands methods, respectively. Next, their respective tangential flux components are computed by solving Poisson's equation and applying a 1-D boundary condition along the tangential direction. Meanwhile, the stator slotting effect is included via the theory of virtual surface current. Finally, the steady-state performance metrics of the motor are calculated and verified via finite-element and experimental measurement.

Improved Open-Circuit Airgap Field Model for FSCW-STPM Machines Considering PM-MMF Fluctuation

In this article, we propose an improved analytical model for the fractional-slot concentrated-winding spoke-type permanent-magnet (PM) machines, where the impact of slotting on magnetomotive force (MMF) is elaborately considered. First, the deficiency of the existing MMF-permeance model using Carter's coefficient is discussed. It is found that adopting Carter's coefficient will cause considerable prediction errors in flux density, especially for machines with a small equivalent airgap and considerable PM-MMF fluctuation. Second, an improved analytical model is proposed based on the relative permeance function and a simplified magnetic circuit model. The proposed model enables to predict common electromagnetic performance, such as PM flux density and back electromotive force with higher accuracy. Moreover, the radial forces exerted on the stator teeth can be predicted precisely as well, which is conducive to further vibration analysis. Both the experimental and finite-element analysis results indicate that the proposed model can enhance the characterization capability of the slotting effect and improve the performance prediction accuracy.

Study of Boosted Toothed Biased Flux Permanent Magnet Motors

In this article, three new toothed biased flux permanent magnet (PM) motors are introduced and studied, each of which has a specific arrangement of excitation (dc field/PM) and flux path (series/parallel). This results in three main structures, namely, hybrid excited toothed slot-PM (HETSPM), toothed biased flux PM (TBFPM) with series flux path, and, finally, toothed biased flux slot PM (TBFSPM) with hybrid flux path. The TBFSPM structure has improved the average torque, torque ripple, and efficiency compared to other stator-PM motors. The HETSPM structure has improved the average torque per PM, and the TBFPM structure features a very low-torque ripple profile compared to other stator-PM motors. All the topologies have shown a good PM demagnetization resistance and lower PM loss compared to other structures. Moreover, a new Carter’s coefficient is introduced to increase the accuracy of harmonic analysis for split-tooth structures by modeling the nonlinear effect of fringing flux with a new transition function, which has increased the accuracy by 20% compared to the traditional approach. The theoretical analyses have been checked by the 2-D finite element method (FEM), and the TBFSPM structure is prototyped and tested to validate the simulation analyses.

An Improved Implicit Model Predictive Current Control With Continuous Control Set for PMSM Drives

This article proposes an improved implicit model predictive current control (IMPCC) method for permanent magnet synchronous motor (PMSM) drives. Compared to the conventional implicit MPC, the proposed IMPCC has a much lower computational burden and thus is suitable for real-time applications. Two-step optimization is employed in this method to minimize the cost function based on continuous control set (CCS) while respecting the constraints. Furthermore, the proposed IMPCC uses an incremental model that eliminates the permanent magnet flux linkage. Its strong parameter robustness against stator resistance and inductance variations is also theoretically analyzed. Experimental results are presented to show the superior performance of the proposed IMPCC.

Model Predictive Current Control With Variable Gain Adaptive Observer Based on Current Augmenter Prediction Model for IPMSM Drives

This paper proposes a model predictive current control (MPCC) method based on current augmenter prediction model (CAPM) appropriate for interior permanent magnet synchronous motor (IPMSM) under high-speed condition. The accuracy of CAPM is improved by considering rotor movement during one control period especially under high-speed condition. Meanwhile, the use of the permanent magnetic flux linkage is eliminated. In order to further improve the robustness of the MPCC method, an adaptive observer based on CAPM is designed to estimate the model error. The proposed adaptive observer also eliminates the use of the permanent magnetic flux linkage, so the whole implementation process of the MPCC method with adaptive observer is independent of the permanent magnetic flux linkage. Moreover, since the adaptive observer with fixed adaptive integral gain cannot achieve satisfactory performance under different operating conditions of the motor, this paper designs a calculation method for the variable adaptive integral gains by considering the current estimation error, the amplitude of current and the angular velocity of the IPMSM. Finally, the proposed method is validated by means of the experimental results on a 20-kW test platform.

Improved super-twisting-observer-based finite-control-set model-predictive fault-tolerant current control of PMSM considering demagnetization fault

Temperature and other factors will cause the permanent-magnet flux to demagnetize. The demagnetization fault inevitably results in the prediction error since the finite-control-set model-predictive current control (FCS-MPCC) method is sensitive to the parameter variation of permanent magnet synchronous motor (PMSM). This paper presents a improved super-twisting-observer-based FCS model-predictive fault-tolerant current control (ISTO-based FCS-MPFTCC) method to compensate for the prediction error caused by the demagnetization fault. The unified PMSM model of healthy and demagnetized is first derived. Next, a improved super-twisting-observer (ISTO) is designed to detect permanent-magnet flux. The estimated permanent-magnet flux updated the prediction model. Thus, the presented method performs fault-tolerant current-control of PMSM on the demagnetization fault. It eliminates the influence caused by the demagnetization fault. The experiment results validate the effectiveness of the presented ISTO-based FCS-FCS-MPFTCC method.

Modeling and designing a hybrid reluctance actuator for fast-steering mirror

The actuator is a primary component of the fast-steering mirror (FSM), and its quality directly determines the performance of FSM. To achieve high compactness, high efficiency, large output torque, and effective linearity, a hybrid reluctance actuator (NHRA) for FSM was designed. To obtain a high-force density and small flux leakage, four permanent magnets (PMs) were designed on the side of the armature, which improves the linearity of the actuator by generating a bias flux. Meanwhile, to obtain the maximum output torque for a limited size, the structural model of the actuator was established in ANSYS Maxwell, and all structural parameters were optimized. In addition, an analytical model of the actuator was established via the equivalent magnetic circuit method. To improve the modeling accuracy, both PM and coil flux leakages were considered. The theoretical and simulation results were insignificant in agreement, and both showed the output torque of this actuator to be approximately twice that of a state-of-the-art actuator under the same volume, simultaneously improving the linearity.

Detection of Demagnetization Faults in Axial Flux Permanent-Magnet Synchronous Wind Generators

A new method for detecting demagnetization faults in axial flux permanent magnet synchronous wind generators is presented in this study. Demagnetization faults occur in the case of total or partial loss of the magnetic properties of one or more permanent magnets of the machine. Fault signatures appearing in the current or voltage signal due to a demagnetization fault can often be confused with those produced by eccentricity faults, making the discrimination between the two types of faults difficult. The proposed methodology is based on the analysis of the instant power spectrum of the generator, combined with an estimator to derive the permanent magnet flux, based on the machine equations. Short-Time Fourier Transform is proposed as the means for spectrum analysis to ensure performance during variations of the generator speed. Results derived from the experimental tests are presented, which show that the proposed methodology is capable of detecting demagnetization faults and distinguishing them from eccentricity ones under a wide variety of operating conditions.

Design optimization with improved torque performance of a new flux-intensifying PMSM using multilayer barriers for solar water pumps

A novel flux-intensifying interior (FII) permanent magnet synchronous motor (PMSM) based on multilayer barriers in rotor structure with improved torque performance for solar water pump system is proposed here. The conventional interior (CI) PMSM generates maximum total torque on application of negative current along d-axis, resulting in an increment of demagnetization possibility of permanent magnets (PMs). Although flux-intensifying PMSMs solve this issue, their reluctance torque is lower due to the reduced saliency difference. This problem is solved by the presented FII-PMSM, which produces higher reluctance torque through specially designed barriers. Two types of barriers namely, inner and outer cutoff barriers are designed in rotor along quadrature axis. The inner barriers realize flux-intensifying effect while the outer cutoff barriers increase the saliency difference and hence the reluctance torque. Besides, the dimensions of barriers are optimized by using parametric optimization to maximize saliency difference and minimize torque ripples. The finite element methods based electromagnetic performances of FII-PMSM like inductance curves, torque profiles, airgap gap flux density, back electromotive force plots, efficiency map, output power map and PM flux density are obtained and compared with the CI-PMSM to show the superiority of presented motor.

Dual mechanical port power distribution in dual rotor permanent magnet flux switching generator for counter‐rotating wind turbine applications

The cover image is based on the Research Article Dual mechanical port power distribution in dual rotor permanent magnet flux switching generator for counter-rotating wind turbine applications by Wasiq Ullah et al., https://doi.org/10.1049/rpg2.12450.

Vortex Ring and Helical Current Formation in Superconductors Driven by a THz‐Field‐Induced Toroidal Vector Potential

Herein, the vortex dynamics in a type II superconducting torus driven by a curl‐free vector potential corresponding to a toroidal moment is studied, which is triggered within picoseconds in an enclosed semiconductor by polarization‐structured THz vector field pulses. Numerical simulations of the time‐dependent Ginzburg–Landau equation in the presence of the toroidal vector potential evidence the formation of vortex ring structures that depend on the toroidal moment strength with a behavior resembling the Little–Parks effect. Applying in addition a static external magnetic flux density, the induced textures in the superconducting phase can be stabilized and steered to form stripe domains with corresponding helical supercurrent density.

Torque Control for Electric Drive System Used in Electric Vehicle in the Presence of Permanent Magnet Demagnetization Faults

The performance of conventional torque control for PMSM drive used in electric vehicles (EVs) from the viewpoint of permanent magnet (PM) demagnetization faults has not been satisfactory. Therefore, a combination method based on sliding-mode observer and active disturbance rejection control is presented. First, the model of the PMSM system with PM demagnetization faults is constructed. Then, a sliding-mode observer is designed based on a minimum extended flux linkage to estimate the torque and the PM flux linkages of the system. A current controller is presented based on active disturbance rejection control approach to reject the PM demagnetization faults. The method is useful to improve the control performance of the PMSM drive system. And the system is robust to system parameters variations. Finally, an RT-LAB real-time simulation is used to build a simulation model of hardware-in-the-loop based on the experimentally validated model that is derived from the actual development process for an electric bus. The simulation and experimental results demonstrate the effectiveness of the method.

Performance Investigation and Cogging Torque Reduction in a Novel Modular Stator PM Flux Reversal Machine

In this research paper, various performances of five different rotor pole topologies of the proposed novel modular stator (MS) permanent magnet (PM) flux reversal machine were investigated. The proposed design had concentrated, non-overlapping winding, which offered high average torque capability at a wide speed range. The no-load performances such as coil test analysis, three-phase flux linkage, flux distribution, back-EMF, and cogging torque, and load analysis, such as average torque versus current density, instantaneous torque, and average electromagnetic torque, were compared. The PM modular stator machine had high cogging torque, which created vibration and noise in the machine. Different cogging torque reduction techniques, such as notching, arc, flange and hybrid technique arc flange, arc notch, notch flange, and arc notch flange, were applied to reduce the cogging torque, improve average load torque, and reduce the induced voltage, harmonics, and torque ripples. The maximum cogging torque decreased by 87.66% and 82% when the arc notch flange and notch arc techniques were applied, respectively, and the minimum effect on cogging torque by the flange technique was 20.66%. Furthermore, the arc flange technique reduced the average torque by 66.72%. The maximum induced voltage was reduced by up to 12.83% using the notch arc technique. The hybrid technique of arc notch flange reduced the harmonics content in flux by 40% and enhanced electromagnetic performance. When applying the hybrid arc notch flange technique, torque ripples were reduced to 90.11%.

Dual mechanical port power distribution in dual rotor permanent magnet flux switching generator for counter‐rotating wind turbine applications

In this paper, a novel dual mechanical port dual rotor counter-rotating permanent magnet flux switching generator (DMPDRCR-PMFSG) for wind turbine applications is proposed. Power distribution between the inner and outer rotors of the proposed DMPDRCR-PMFSG that contributes to the cumulative output power is investigated. The proposed DMPDRCR-PMFSG shares a stator connected back-to-back through flux bridge. The flux bridge physically isolates the armature winding of the inner and outer ports. Furthermore, the flux bridge provides a flux path to magnetic flux of the inner and outer ports that contributes to cumulative output power. Quantitative comparative analysis of the inner and outer ports illustrates that under static analysis 18.57% more flux, 23.95% highly induced back-EMF, 31.08% of enhanced average torque are obtained in the outer rotor at the cost of 64.01% and 22.7% increase in cogging and torque ripple ratio, respectively. Comparative analysis with a number of turns reveals that the outer port offers 41.17% higher output power and 7.09% improved efficiency at the cost of 42.52% increase in voltage regulation factor. Finally, coupled overload and over-speed analysis shows that despite a stable and low voltage drop ratio, the outer port offers 4.65% higher output voltage. Analysis shows that in the proposed DMPDRCR-PMFSG, the outer port has a dominant contribution to the cumulative power distribution.

Speed Sensorless Control for IPMSMs Using a Modified MRAS With Gray Wolf Optimization Algorithm

This article represents modified model reference adaptive system (MRAS) method for speed sensorless control of interior permanent magnet synchronous motor (IPMSM), which can estimate rotor speed and position information. To suppress the adverse effect of parameter variation on control performance, the stator resistance and the permanent magnet flux linkage are estimated and continuously updated in reference and adjustable model. Then, proportional-integral (PI) controller parameters of speed adaptive law obtained by MRAS are optimized by gray wolf optimization (GWO) algorithm. To get the smallest possible speed following error and reference current error, the objective function is designed with discretized rotor speed error and current error as variables. The simulation results show the better performance of rotor speed estimation is obtained with GWO algorithm.

Virtual Sensor Using a Super Twisting Algorithm Based Uniform Robust Exact Differentiator for Electric Vehicles

The highly efficient Interior Permanent Magnet Synchronous Motor (IPMSM) is ubiquitous choice in Electric Vehicles (EVs) for today’s automotive industry. IPMSM control requires accurate knowledge of an immeasurable critical Permanent Magnet (PM) flux linkage parameter. The PM flux linkage is highly influenced by operating temperature which results in torque derating and hence power loss, unable to meet road loads and reduced life span of electrified powertrain in EVs. In this paper, novel virtual sensing scheme for estimating PM flux linkage through measured stator currents is designed for an IPMSM centric electrified powertrain. The proposed design is based on a Uniform Robust Exact Differentiator (URED) centric Super Twisting Algorithm (STA), which ensures robustness and finite-time convergence of the time derivative of the quadrature axis stator current of IPMSM. Moreover, URED is able to eliminate chattering without sacrificing robustness and precision. The proposed design detects variation in PM flux linkage due to change in operating temperature and hence is also able to establish characteristics of fault detection. The effectiveness and accuracy in different operating environments of the proposed scheme for nonlinear mathematical IPMSM model with complex EV dynamics are verified thorough extensive simulation experiments using MATLAB/Simulink.

Analysis of Linear Hybrid Excited Flux Switching Machines with Low-Cost Ferrite Magnets

Linear hybrid excited flux switching machines (LHEFSM) combine the features of permanent magnet flux switching machines (PMFSM) and field excited flux switching machines (FEFSM). Because of the widespread usage of rare-earth PM materials, their costs are steadily rising. This study proposes an LHEFSM, a dual stator LHEFSM (DSLHEFSM), and a dual mover LHEFSM (DMLHEFSM) to solve this issue. The employment of ferrite magnets rather than rare-earth PM in these suggested designs is significant. Compared to traditional designs, the proposed designs feature greater thrust force, power density, reduced normal force, and a 25% decrease in PM volume. A yokeless primary structure was used in a DSLHEFSM to minimize the volume of the mover, increasing the thrust force density. In DMLHELFSM, on the other hand, a yokeless secondary structure was used to lower the secondary volume and the machine’s total cost. Single variable optimization was used to optimize all of the proposed designs. By completing a 3D study, the electromagnetic performances acquired from the 2D analysis were confirmed. Compared to conventional designs, the average thrust force in LHEFSM, DSLHEFSM, and DMLHEFSM was enhanced by 15%, 16.8%, and 15.6%, respectively. Overall, the presented machines had a high thrust force density, a high-power density, a high no-load electromotive force, and a low normal force, allowing them to be used in long-stroke applications.