Performance Analysis of Wide Magnesium Alloy Foil Rolled by Multi-Pass Electric Plastic Rolling

Lipo Yang,Hailong Zhang,Gengliang Liu 대한금속·재료학회 2023 METALS AND MATERIALS International Vol.29 No.10

Wide magnesium alloy foil is usually difficult to roll due to severe anisotropy or texture. It has become the biggest obstacle to the traditional rolling process, although it can be realized through some special methods. Low efficiency and high cost limit its application. Aimed at this problem, a multi-pass electric plastic rolling process was designed to successfully roll the magnesium alloy foil from 1.0 to 0.13 mm. According to actual test results, the anisotropy and properties of magnesium alloy foil were analyzed when the pulse current densities were adjusted. Under the same temperature as the isothermal rolling process, the pure electric effect could contribute to remarkably improving the plasticity and rollability of magnesium alloy foil. Thus, it could minimize the action of Joule heat as much as possible to avoid surface oxidation and grain growth. In addition, the size effect of magnesium alloy foil should be considered for the electric plastic rolling. Practical measured data verified that varied pulse current densities played important roles in the performances of wide magnesium alloy foil when the grain size and anisotropy were online adjusted by the synergy of electric plastic effect and reduction rate.

Anisotropy evolution of wide magnesium alloy foils during continuous electroplastic rolling

Lipo Yang,Hailong Zhang,Gengliang Liu 대한기계학회 2023 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.37 No.4

Anisotropy or brittleness poses an obstacle to the rolling of wide magnesium alloy foils, particularly those with a thickness of 1.0 mm. To address this problem, a special electroplastic rolling (EPR) process was developed to provide a better method than traditional isothermal heat treatment. Actual measured results showed that the pulse current with high energy could rapidly adjust high brittleness and severe anisotropy. This condition was helpful in the plasticity and rollability of wide magnesium alloy foils during continuous EPR process. Finally, a 0.13 mm-thick magnesium alloy foil was successfully rolled through continuous EPR processes without any intermediate annealing or reheating in the furnace. Evidently, the developed method contributed to the best matching conditions between the pulse current and deformation parameters along different directions. Therefore, EPR is a promising technology for changing the anisotropy or brittleness of wide magnesium alloy foils online.

Dual-Stator Two-Phase Permanent Magnet Machines With Phase-Group Concentrated-Coil Windings for Torque Enhancement

Zhao, Wenliang,Lipo, Thomas A.,Kwon, Byung-Il IEEE 2015 IEEE transactions on magnetics Vol.51 No.11

<P>This paper presents two types of novel dual-stator two-phase permanent magnet synchronous machines (PMSMs) equipped with an advanced phase-group concentrated-coil winding and a spoke-type PM array for direct-drive applications. The key advantage of the proposed two-phase PMSMs is its superior flux-focusing effects, which greatly enhance the torque, benefiting from the whole machine configuration. To highlight the advantages of the proposed two-phase PMSMs, one three-phase PMSM and one two-phase PMSM with the conventional stator and winding configurations are adopted for comparison. All relevant machine characteristics, including the air-gap flux density, back electromotive force, and electromagnetic torque, are predicted by a 2-D finite-element method. Finally, one of the proposed dual-stator two-phase PMSMs is optimized to minimize cogging torque and torque ripples using the Kriging method and a genetic algorithm.</P>

A Novel Two-Phase Permanent Magnet Synchronous Motor Modeling for Torque Ripple Minimization

Fei Zhao,Lipo, T. A.,Byung-Il Kwon IEEE 2013 IEEE transactions on magnetics Vol.49 No.5

<P>This paper proposes a novel two-phase, two-pole, permanent magnet synchronous motor (PMSM) with dual U-core stator structure for torque ripple minimization. The proposed motor is modeled based on the conventional single-phase U-core PMSM with approximate output power and core dimension. Torque ripple in the novel motor can be reduced significantly due to 90 <SUP>°</SUP> electrical angle phase shift in two sets of magnet pairs and 90<SUP>°</SUP> shift in two-phase excitation currents. Characteristics of both PMSMs such as back-EMF, cogging torque and electromagnetic torque are analyzed and compared by using the 3-D finite element analysis (FEA). As shown in the result, the cogging torque and torque ripple in the novel two-phase PMSM are efficiently reduced with sinusoidal back-EMF waveform and reasonable current density value. The validity of both PMSM models is also verified by the comparison between simulated and experimental measured results.</P>

Comparative Study on Novel Dual Stator Radial Flux and Axial Flux Permanent Magnet Motors With Ferrite Magnets for Traction Application

Wenliang Zhao,Lipo, Thomas A.,Byung-Il Kwon IEEE 2014 IEEE transactions on magnetics Vol.50 No.11

<P>This paper proposes two novel traction motors with ferrite magnets for hybrid electric vehicles (HEVs), which have competitive torque density and efficiency as well as operating range with respect to a referenced rare earth magnet motor employed in the third-generation Toyota Prius, a commercialized HEV. The two proposed traction motors, named as dual stator radial flux permanent magnet motor (DSRFPMM) and dual stator axial flux permanent magnet motor (DSAFPMM), adopt the same design concept, which incorporates the unaligned arrangement of two stators together with the use of spoke-type magnet array and phase-group concentrated-coil windings for the purpose of increasing torque density and reducing torque ripple. A finite element method is utilized for predicting the main characteristics, such as back electromotive force, cogging torque, electromagnetic torque, iron loss, and efficiency in both of the proposed motors. Moreover, a comparative study between the proposed DSRFPMM and DSAFPMM is performed under the same operating condition. As a result, it is demonstrated that both of the proposed ferrite permanent magnet motors could be good alternatives for traction application, replacing the rare earth magnet motors.</P>

A Novel Dual-Stator Axial-Flux Spoke-Type Permanent Magnet Vernier Machine for Direct-Drive Applications

Fei Zhao,Lipo, Thomas A.,Byung-Il Kwon IEEE 2014 IEEE transactions on magnetics Vol.50 No.11

<P>This paper proposes a novel double-stator axial-flux spoke-type permanent magnet vernier machine, which has a high torque density feature as well as a high-power factor at low speed for direct-drive systems. The operation principle and basic design procedure of the proposed machine are presented and discussed. The 3-D finite element method (3-D-FEM) is utilized to analyze its magnetic field and transient output performance. Furthermore, the analytical method and a simplified 2-D-FEM are also developed for the machine basic design and performance evaluation, which can effectively reduce the modeling and simulation time of the 3-D-FEM and achieve an adequate accuracy.</P>

Design and Analysis of a Novel Brushless Wound Rotor Synchronous Machine

Ali, Qasim,Lipo, Thomas A.,Kwon, Byung-Il IEEE 2015 IEEE transactions on magnetics Vol.51 No.11

<P>This paper presents a new concept for brushless excitation of a wound rotor synchronous machine (WRSM) based on the generation and utilization of a subharmonic component of the stator magnetomotive force (MMF). In this method, a dual inverter topology for the stator winding is proposed. The idea is to generate and utilize an additional subharmonic stator MMF component along with the fundamental component. The rotor carries two different windings: 1) excitation winding and 2) field winding. The subharmonic component induces voltage in the excitation winding and feeds the field winding through a rotating rectifier on the rotor. A 2-D finite-element analysis was performed to analyze and verify the proposed brushless WRSM.</P>

Optimal Design of a Novel Asymmetrical Rotor Structure to Obtain Torque and Efficiency Improvement in Surface Inset PM Motors

Wenliang Zhao,Lipo, Thomas A.,Byung-Il Kwon IEEE 2015 IEEE transactions on magnetics Vol.51 No.3

<P>This paper proposes an optimal design of a novel asymmetrical rotor structure for surface inset permanent magnet (PM) motors to obtain torque and efficiency improvement. Different from the conventional approach, the proposed design of asymmetrical rotor structures is employed to improve the torque production by creating rotor asymmetry to allow the reluctance torque and the magnetic torque to reach a maximum at the same current phase angle. To evaluate the contribution, the frozen permeability method is utilized to segregate the torque into its reluctance and magnetic torque components. For demonstrating the design concept and obtaining a criterion for improving torque by making full use of torque components, an optimal design by iterative computation is first to be performed utilizing the finite-element method. Based on the obtained criterion, the optimal design by algorithms, such as the Kriging method and genetic algorithm, is applied to further improve the torque and efficiency. As a result, the performance of the proposed surface inset PM motor by two-step optimization is dramatically improved compared with that of the conventional surface inset PM motor. Furthermore, a comparison between the optimized surface inset PM motor and a conventional surface-mounted PM (SPM) motor is also performed under the same operating condition, which demonstrates that the optimized surface inset PM motor can significantly save the magnet amount compared with the conventional SPM motor for producing the same output torque.</P>

Torque Pulsation Minimization in Spoke-type Interior Permanent Magnet Motors With Skewing and Sinusoidal Permanent Magnet Configurations

Zhao, Wenliang,Lipo, Thomas A.,Kwon, Byung-Il IEEE 2015 IEEE transactions on magnetics Vol.51 No.11

<P>This paper proposes two approaches to minimize torque pulsations, including cogging torque and electromagnetic torque ripple, for spoke-type interior permanent magnet (IPM) motors. The first approach is an improved skewing method, in which the rotor PMs are skewed by being symmetrical in the axial direction within one magnet pole pitch for not only reducing torque pulsations but also maintaining maximum available torque and eliminating unbalanced axial electromagnetic forces. The second one is a sinusoidal PM-shaping method with the aim of achieving the same advantageous effects as the proposed skewing method. Both the proposed methods adopt stepped rotor-PM schemes, and the effects of the rotor-PM step numbers on motor performance are investigated. To highlight the advantages of the proposed approaches, a spoke-type IPM motor with the conventional PM configuration is adopted as the basic model. All the motor characteristics, such as back electromotive force, cogging torque, and electromagnetic torque, are predicted by a 3-D finite-element method with the aid of JMAG-Designer.</P>

A 32 000 r/min Axial Flux Permanent Magnet Machine for Energy Storage With Mechanical Stress Analysis

Kumar, Sunil,Lipo, Thomas A.,Byung-Il Kwon IEEE 2016 IEEE transactions on magnetics Vol.52 No.7

<P>This paper focuses on the design and analysis of a high-speed axial flux permanent magnet (PM) machine for an aerospace flywheel energy storage system. The design target is to experimentally verify the sinusoidal back electromotive force (EMF) considering the mechanical stress limitation of the machine at a speed of 32 000 r/min. Two machine models based on ferrite and SmCo PMs have been proposed. First, the back EMF analysis using a 3-D finite-element method is performed to determine the performance of the two models. Second, the mechanical stress analysis is performed to check the durability of the rotor strength. Finally, the selected model utilizing the ferrite PMs has been manufactured and tested at 32 000 r/min to validate its effectiveness at high-speed operation.</P>