Flux Path Research Articles

An Inductive Power Transfer System With Multiple Receivers Utilizing Diverted Magnetic Field and Two Transmitters for IoT-Level Automatic Catering Vehicles

Automatic catering vehicles (ACVs) are increasingly adopted in restaurants to save expensive human resources. Especially in special situations such as a pandemic, ACV offers a wise choice to keep social distance. In this paper, a wireless power transfer (WPT) system is proposed to charge four ACVs at the same time. With the help of ferrite cores, the flux can be guided through all four receivers while the leakage magnetic field can be reduced simultaneously. Two transmitters are utilized to confine the flux path further. Both areas #A and #B can charge UAVs with the consideration of the mechanical structure of the food preparation area and charging standby area (Areas #A and #B). The presented system can also realize zero phase angle (ZPA) to degrade the volt-ampere (VA) rating. Finally, an experimental setup is constructed, and the overall dc-dc efficiency is 87.6% when delivering 120 W to four loads.

A Built-In Integrated Magnetorheological Fluid Brake Permanent Magnet Synchronous Motor

In this paper, a built-in integrated magnetorheological (MR) fluid brake permanent magnet synchronous motor is presented, which can switch between rotation and brake operation states in a relatively simple structure by integrating the MR fluid brake inside the rotor of the PMSM. Benefiting from the different flux paths design corresponding to the armature winding in the outer stator and the braking winding in the inner stator, the proposed machine can provide adequate brake torque and improve space utilization. This paper illustrates machine topology, operation principles, and design considerations. After proceeding flux leakage reduction, magnetic pole layout optimization of the braking winding, and balance optimization between brake torque and electromagnetic torque, successively, the optimal machine is obtained. Finally, the finite element analysis is devoted to the electromagnetic performance analysis of the proposed machine, and torque capabilities between rotation and brake states are compared, verifying the feasibility of the integration design.

Evaluation of microstructure, mechanical and magnetic properties of laser powder bed fused Fe-Si alloy for 3D magnetic flux motor application

Since their high power-to-volume property, electric machines with 3D magnetic flux (3D-flux) structure are of great current interest. In them, the flux path is typically achieved by utilizing a soft magnetic composite (SMC) material to minimize the eddy current losses. Here, laser powder bed fusion (LPBF) technique is employed to manufacture a soft magnetic core (Fe-3.5 wt%Si alloy) with the following advantages: i) the (001) texture of Fe-Si alloy is well aligned with the Z direction of the 3D-flux path, which is the easiest magnetization direction in the cubic system; ii) the strength and ductility of the annealed alloy are far superior to those of SMCs. The alternating-current ring method was employed to measure the magnetic properties and a simulation of the 3D-flux electric machine was conducted. The results illustrated that the rotary torque generated with the additively manufactured alloy is 19.1% higher than that of SMCs in the weak magnetic field excited by ferrite at the 50 Hz frequency. However, it is important to note that the additively manufactured alloy also exhibited higher total iron loss in strong magnetic field and high electric frequency, indicating a need for further research to optimize the microstructure and reduce losses for medium/high frequency applications.

Electromagnetic and Thermal Analysis of a 6/4 Induction Switched Reluctance Machine for Electric Vehicle Application

In this paper, an oil-cooling induction switched reluctance machine (ISRM) is offered. The stator and rotor of the electric machine are non-segmental. However, by placing coils on the rotor, a short magnetic flux path is achieved in the rotor and stator cores. As a result, a higher torque with lower losses is generated. This configuration can be used in high-power electric motors for electric and hybrid vehicles. ISRM is a novel machine and there is a lack of access to its operation and data characteristics. ISRM can be designed in different configurations with various stator and rotor pole numbers and winding strategies. In this study, an oil-cooling three-phase ISRM with 6 stator poles and 4 rotor poles was considered. Firstly, a 2D finite element model of it is created, and its magnetic properties extracted, the flux path, torque and efficiency of the ISRM are calculated, and the results are presented. Secondly, the thermal performance of the motor is analyzed using ANSYS Motor-Cad software. Finally, a prototype of the ISRM and its appropriate drive with the oil cooling system is built and tested. The experimental results and conclusions which prove the ability of the presented machine are presented in the last parts of the paper.

A Study on a Fully Integrated Coil Based on the LCCL-S Compensation Topology for Wireless EVs Charging Systems

This study proposes a full integration method for the double capacitances and inductance–series (LCCL-S)-compensated inductive power transfer (IPT) of electric vehicles (EVs). The transmitter and receiver coils adopt the unipolar coil, and the compensation inductor is designed as an extended DD coil. Specifically, the use of an extended DD coil enhances the misalignment tolerance of the EVs. When the IPT system is in the misaligned state, a primary transfer path for magnetic flux is established between the transmitter and receiver coils, and a secondary transfer path is established between the extended DD coil and receiver coil. The distance between the two unipolar coils of the extended DD coil is optimized to maximize the magnetic flux on the secondary transfer path, thereby increasing the total power of the system misaligned state. Simultaneously, the most suitable turns and inner diameter of the extended DD coil are designed by using the finite element method (FEM) simulation tool. In order to verify the performance of the proposed integrated coil method, a 3.3 kW experimental prototype with a 100 mm air gap was constructed and compared with the conventional integration method under the same conditions. The experimental results show that the proposed magnetic coupling structure maintains at least a 63.6% well-aligned value at a door-to-door 150 mm misaligned state, and the output power of the system is 1.05 kW higher than that of the traditional integration method without extra control algorithms.

Implementation of Different 2D Finite Element Modeling Approaches in Axial Flux Induction Motors

Axial flux induction motors (AFIM) are gaining popularity due to their higher torque density than radial flux motors. However, axial flux motors have a more complex structure than radial flux motors due to their diameters expanding from the inside out. Before manufacturing, designers have two contradictory goals in the simulation phase. These are high accuracy and short analyses time. The finite element method is a commonly utilized technique for verifying designs. However, in the early stages of AFIM design, a 2D radial flux modeling approach can yield faster results. This approach is well-suited for radial motors, where 2D analysis is widely employed to achieve accurate designs within reasonable analysis times. However, for AFIM with a non-axisymmetric flux path, the application of 2D analysis poses some difficulties. This study compares three modeling approaches, linear, inner rotor and outer rotor modeling approaches to a 3D model and examines their steady-state performance. The results show compatibility in performance data, with some deviations in the torque-speed curve for inner rotor modeling and outer rotor modeling approach methods, which can be reduced by resizing the slots. Overall, acceptable errors and consistent results were achieved between the models.

An improved equivalent magnetic network model of IPM motor in electric vehicles for dynamic simulation of transient effects

The existing electric motor model for electric vehicles cannot address the simulation of transient conditions. Moreover, it is difficult to balance the computation time and simulation accuracy. To address these shortcomings, an improved internal permanent magnet motor model containing nonlinear magnetic field factors was proposed based on the equivalent magnetic circuit theory. The effects of the magnetic circuit saturation, cogging torque, and magnetic field harmonics on the electromagnetic torque could be reflected. Furthermore, the electromagnetic vibration and rotor eccentricity could be considered. To improve the computational efficiency of the equivalent magnetic network method, lumped parameter or mesh-based methods were used for flux paths with different complexities. Second, the single-layer mesh-based method with local variable permeability parameters improved the efficiency of the air-gap dynamic analysis and computational efficiency while simulating 2D flux paths. The radial and tangential electromagnetic forces were calculated using the Maxwell tensor method and the action on the rotor. The accuracy of the nonlinear magnetic field modeling was verified by finite element analysis and experimental. In addition, the motion modeling method and dynamic characteristics of the model were studied. A reference was provided for dynamic simulations of electric vehicles and other using permanent magnet motors.

Electromagnetic Characteristics of Dual-Air-Gap Surface Permanent Magnet Synchronous Motor

This paper introduces a novel dual-air-gap surface permanent magnet synchronous motor (DAG-SPMSM) and investigates its electromagnetic characteristics. The motor comprises two stators (inner and outer) and a single rotor with permanent magnets on both sides (inner and outer). The magnets are arranged in a zig-zag configuration to isolate the inner and outer stator and rotor magnets. Additionally, a magnetic shield is incorporated into the rotor to further isolate the rotor magnetic flux, which results in a localized short flux path that can reduce core loss. The insertion of the magnetic shield also affects the flux path, reducing torque ripple. The electromagnetic characteristics, such as flux path, flux density, and torque, are analyzed using finite element analysis. The effectiveness of using a magnetic screen is also evaluated, and simple experiments are conducted to validate the observed characteristics of the proposed motor.

Investigation of an unconventional exciter of a toothed stator using software by the finite element method

In this article we investigate an unconventional design of an exciter having a toothed stator. The main purpose is to check whether the proposed machine can meet the operating parameters specified in the specification. This chapter begins with a description of a current exciter with protruding poles and a description of a design with teeth. The toothed stator is also distinguished by being made of an inexpensive ferromagnetic material such as cast iron. When choosing cast iron, they are guided by the fact that it is already used in industry in other components of alternators, such as bearings and some connecting bushings. The use of cast iron also reduces eddy current losses compared to solid steel parts. Since the path of the magnetic flux in the stator is three-dimensional, the study is carried out using software for 3D finite element calculation. The model of the machine is compared with the experimental results obtained on the layout. Then we make changes to the geometry of the machine to improve its characteristics. In conclusion, we present the balance of active substances of the gear structure and the balance. The obtained results allow us to establish a good consistency of the finished element model with the test results.

Design of Rotor Magnetic Barrier Structure of Built-in Permanent Magnet Motor Based on Taguchi Method

In this paper, a 20kW vehicle built-in permanent magnet synchronous motor is taken as an example, and a magnetic barrier structure is added to the rotor of the motor to solve the uneven saturation problem of the rotor side magnetic bridge. This structure improves the air-gap flux density waveform of the motor by influencing the internal magnetic flux path of the motor rotor, thus improving the sine of the no-load back EMF waveform of the motor and reducing the torque ripple of the motor. At the same time, Taguchi method is used to optimize the structural parameters of the added magnetic barrier. In order to facilitate the analysis of its uneven saturation phenomenon and improve the optimization effect, a simple equivalent magnetic network (EMN) model considering the uneven saturation of rotor magnetic bridge is established in this paper, and the initial values of optimization factors are selected based on this model. Finally, the no-load back EMF waveform distortion rate, torque ripple and output torque of the optimized motor are compared and analyzed, and the influence of magnetic barrier structure parameters on the electromagnetic performance of the motor is also analyzed. The results show that the optimized motor can not change the output torque of the motor as much as possible on the basis of reducing the waveform distortion rate of no-load back EMF and torque ripple.

A Study on the Improvement of Power Density of Axial Flux Motors for Collaborative Robot Joints through Same-Direction Skew

Axial flux motors have a large output density with a large outer diameter of the motor and a short axial length. Since it is advantageous in short axial length, the axial thickness of motor components becomes a very important parameter when designing axial flux motors. Among the components, the back yoke exists to serve as a path for magnetic flux and must have a certain thickness to prevent magnetic saturation. However, as the thickness of the back yoke increases within the axial size limit of the motor, the output of the motor may decrease. In this paper, same-direction skew that increases the cross-sectional area of the magnetic flux path without increasing the thickness of the back yoke is presented. Same-direction skew is a way to increase the cross-sectional area of the back yoke by skewing the rotor and stator in the same direction. The back yoke thickness that can be reduced by same-direction skew was calculated. Performance with same-direction skew designed using the equations was analyzed and compared, and the effectiveness of each type of rotor was verified. The validity of the proposed model was examined using the finite element analysis method.

Torque characteristic improvement of dual-PM modular doubly salient permanent magnet machine using machine ratio adaptation

Machine ratio adaptation of a dual-PM modular doubly salient permanent magnet machine (DPM-DSPM) was proposed to improve the torque characteristics. An optimization design process was examined. Essential machine indicators were investigated to obtain an optimal machine ratio. It was found that p = 4 and a 0.8 rotor pole width ratio of the DPM-DSPM produced the best essential machine indicator that provided the appropriate magnetic flux path and high flux regulation quality. Then, the DPM-DSPM with an optimal machine ratio was investigated based on open-circuit and on-load tests and then compared to a reviewed DPM-DSPM. The results, based on 2-D finite element analysis, verified that the optimal proposed DPM-DSPM had better torque characteristics. In particular, the optimal proposed structure produced 35.04% higher electromagnetic torque with 61.75% lower ripple torque than the review structure. Therefore, an optimal machine ratio for a DPM-DSPM can be beneficial in solving industrial machine problems, especially noise reduction from vibration.

Segmented Stator Switched Reluctance Motor Drive for Light Electric Vehicle

The world market of electric light vehicles will significantly increase in the coming years. What will require the development of better high-performance drives with lowcost, and, if possible, free of permanent magnets. A segmented stator switched reluctance motor is presented to fulfill this objective because it has advantages over the conventional switched reluctance machines, such as segmented stator construction, stator shorter flux paths without flux reversal, and as a consequence, fewer iron losses. Simulations will demonstrate that the proposed segmented stator switched reluctance motor drive is suitable as a powertrain for light electric vehicles.

Quantum Physics and Deep Learning to Reveal Multiple Dimensional Modified Regulation by Ternary Substitution of Iron, Manganese, and Cobalt on Na3V2(PO4)3 for Superior Sodium Storage

AbstractNa3V2(PO4)3 is regarded as a promising candidate for sodium ion batteries. Nevertheless, the poor electronic conductivity, low capacities, and unstable structure limit its further investigations. Herein, a new type of Fe/Mn/Co co‐substituted Na3V2(PO4)3 with nitrogen‐doped carbon coating (NFMC) by a facile sol‐gel route is synthesized. The introduced elements feature in both crystal bulk and carbon coating layer. Suitable heteroatom substitution activates more effective Na+ to participate in electrochemical process and reinforce the structure. An extra high voltage platform at 3.8 V resulting from the multi‐element synergy (Mn2+/Mn3+/Mn4+; Co2+/Co3+; V4+/V5+) is stably and reversibly existed in NFMC to supply added capacities, which is investigated by quantum physics calculations. The high flux paths for Na+ migration and spin quantum state distribution in NFMC are demonstrated by molar magneton calculation. Significantly, the generated polyatomic coordination environment of MNC (M = Fe/Co/Mn) in carbon layer is first proposed. The most optimized combination structures are obtained from 69 possible structures and demonstrated by X‐ray absorption spectroscopy. The superior electrochemical performance is precisely forecasted by innovative deep learning. Predicted values with high precision are obtained based on a small number of operating data, extremely short development period, and provide real‐time status references for safer use.

Hybrid Layer Modeling Method With Dual-Leakage Flux Paths for Heavily Saturated Iron-Cored Linear Permanent Magnet Synchronous Motors

This paper presents the dual-leakage hybrid layer modeling (DL-HLM) method for the linear permanent-magnet synchronous motors (LPMSMs) in a heavily saturated state. The proposed hybrid model consists of the nonlinear dual-leakage flux-tube model for the iron-cored armature where the geometric saliency exists, the Maxwell model for the PM track with uniform layers, and the hybrid input-output conversion method for the iteration between two models. As the minimum number of leakage flux paths, the dual-leakage flux-tube network is selected, considering the opposite-direction leakage fluxes generated by the flux-steering effect in heavily saturated iron-core teeth. The novel reluctance adaptation methods are also proposed, which allow the DL-HLM to accurately capture significant nonlinearities even with the minimum number of leakage flux paths, thereby correctly estimating motor forces in high-performance LPMSMs. The proposed DL-HLM is validated comparing to the equivalent finite element method (FEM) in terms of the magnetic fields in the working air-gap and motor force performances. The proposed modeling method estimates the magnetic fields and forces with an accuracy of higher than 95% even at significantly high saturation levels while simultaneously achieving multiple-orders-of-magnitude faster computation time as compared to the FEM.

Analysis and Suppression of Cross-Coupling Demagnetization in Dual Permanent Magnet Machine for Direct-Drive Application

Dual permanent magnet (PM) machines synthesize two PM excitations together and potentially exhibit higher torque density than conventional single-PM excited machines. In dual-PM excited machines, the existence of one PM excitation tends to cause interior flux density reduction and irreversible demagnetization of the other PM set, and this feature is recognized as cross-coupling demagnetization. Therefore, this article systematically analyzed the mechanism and influence of this unique phenomenon in a dual-PM prototype machine. The results reveal that the cross-coupling demagnetization can result in up to 18% torque reduction under a severe working conditions if the machine is not properly designed. Increasing one set of PM thickness along the magnetization direction is beneficial to enhance the self-demagnetization withstanding ability, whereas the cross-coupling demagnetization on the other PM set has deteriorated. In order to eliminate such a side effect, some techniques, e.g., removing the demagnetization region and alleviating the mutual flux path, are presented to suppress the demagnetization. It is revealed that the demagnetization rate can be reduced to less than 3% with proper design. Finally, a dual-PM prototype is manufactured and tested to validate the improvement of demagnetization withstanding capability by using the presented suppression technique.

Topology Optimization Framework for Simultaneously Determining the Optimal Structural Design and Current Phase Angle of the IPMSMs for the MTPA Control

Although it is crucial to design the magnetic flux path and the maximum torque per ampere (MTPA) current reference under the current limitation, it is challenging to simultaneously consider these features in developing an interior permanent magnet synchronous motors (IPMSM) due to complicated coupling effects. In this article, to overcome the above issue, the motor-design parameters are estimated by conducting electromagnetic finite element (FE) analysis two times at every iteration of topology optimization. Then, the MTPA current phase angle can be analytically expressed in terms of an elementwise relative density (i.e., design variable in topology optimization). In addition, the structural safety is assessed by conducting the structural FE analysis under design-dependent loads to reflect a high-speed rotation. The proposed two-stage topology optimization enables us to simultaneously optimize both a structural design and current phase angle to achieve the maximum electromagnetic performance. Structural safety and manufacturability are also considered to obtain a practically meaningful design. With two different types of permanent magnets, the optimized IPMSMs are obtained and manufactured to validate the proposed method. Simulation and experimental results demonstrate the validity and potential of this work.

A Review of Electric Motors with Soft Magnetic Composite Cores for Electric Drives

Electric motors play a crucial role in modern industrial and domestic applications. With the trend of more and more electric drives, such as electric vehicles (EVs), the requirements for electric motors become higher and higher, e.g., high power density with good thermal dissipation and high reliability in harsh environments. Many efforts have been made to develop high performance electric motors, such as the application of advanced novel electromagnetic materials, modern control algorithms, advanced mathematical modeling, numerical computation, and artificial intelligence based optimization design techniques. Among many advanced magnetic materials, soft magnetic composite (SMC) appears very promising for developing novel electric motors, thanks to its many unique properties, such as magnetic and thermal isotropies, very low eddy current loss, and the prospect of low-cost mass production. This paper aims to present a comprehensive review about the application of SMC for developing various electric motors for electric drives, with emphasis on those with three-dimensional (3D) magnetic flux paths. The major techniques developed for designing the 3D flux SMC motors are also summarized, such as vectorial magnetic property characterization and system-level multi-discipline robust design optimization. Major challenges and possible future work in this area are also discussed.

A New Optimized IPMSM for EVs With Reduced Magnet Loss for Over-Modulation Operation

In the traction motor drives of electric vehicle applications, the over-modulation strategy is usually implemented to enhance the output torque capability of the interior permanent magnet synchronous motor (IPMSM), so that the dc input voltage of the inverters can be fully utilized by operating the inverter up to the six-step mode. However, it will inevitably introduce rich harmonic components into phase current, leading to the worsening issue of magnet eddy-current loss (MECL). Therefore, a new hybrid magnet rotor structure for fractional-slot concentrated-winding IPMSM with optimum design for magnet loss reduction is employed with the vital improvement measures concluded as follows: first, high-resistivity ferrite magnets are introduced in the rotor flux paths of the <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$d$ </tex-math></inline-formula> -axis and <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$q$ </tex-math></inline-formula> -axis, respectively, to form a hybrid magnets rotor structure together with Nd–Fe–B magnets; second, a rotor structure is proposed by employing a V-type placement of Nd–Fe–B magnets in the <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$d$ </tex-math></inline-formula> -axis path with the angle of V-type as one of the critical optimization parameters. An optimized design is finally obtained by employing the multi-objective genetic algorithm optimizer in JMAG finite element analysis tools, which is tested to show that the MECL produced in the over-modulation operation can be significantly suppressed by the optimized design.

Analysis of flux barrier effect of LCF PM in series hybrid magnet variable flux memory machine

Variable flux memory machines (VFMMs) with series hybrid magnets using both low coercive force (LCF) and high coercive force (HCF) permanent magnets (PMs) have been recognized as a viable candidate for wide-speed-range industrial applications due to the advantages of high torque density and wide speed range. Nevertheless, the adverse effects of LCF PM on the HCF PM in series-type VFMM under different magnetization states (MSs) are still unreported. In this paper, the flux barrier effect (FBE) of the LCF PM existing in series hybrid magnet VFMM is first revealed, and its causes are discussed as well as analyzed in depth on the basis of the equivalent magnetic circuit method and finite-element (FE) analyses. A topology of VFMM with dual-layer PMs is further developed to alleviate the FBE induced from LCF PMs. It can be found that the FBE can be effectively suppressed by employing the dual-layer (DL) PM arrangement and additional leakage flux paths. A prototype of the proposed design is built, and the theoretical and FE results are experimentally verified.