With the advance of artificial intelligent (AI), analog computation-in-memory (A-CiM) has been extensively studied for edge-AI applications, due to their low power operations. In this study, we demonstrated the modulation of multi-level weight conductance of ferroelectric field-effect-transistor (FeFET) devices as a synaptic cell. For the precise conductance modulation of FeFET synapses, we developed the simulation framework by combining a ferroelectric switching model, FeFET threshold (Vth) model, and accurate MOSFET drain current model. Then, the poly-Si channel FeFET synapses confirmed the multi-level conductance states (≥ 16-level/cell) with ultra-low current levels and stable retention, which improves energy efficiency of inference for image classification.

This study presents an in-depth analysis aimed at minimizing alternating current (AC) winding loss in high speed train (HST) traction motors using interior permanent magnet synchronous motors (IPMSMs). Focused on distributed traction (DT) systems, the research evaluates different rectangular conductor configurations and slot wedge designs to enhance high voltage winding efficiency. Finite element analysis (FEA), integrated with motor drive circuit simulations, is employed to assess AC winding losses across various configurations, identifying an optimal design that maximizes overall efficiency. The chosen configuration demonstrates reduction in eddy current losses induced by leakage flux, skin depth, and proximity effects. Validation of this configuration is achieved through prototyping and dynamometer testing, confirming FEA predictions. The findings not only contribute to the theoretical understanding of AC winding loss in traction motors but also provide practical guidelines for designing more efficient traction motors by minimizing the AC winding losses, crucial for advancing high speed train systems.

This research proposes a bi-directional electromagnetic-thermal coupled analysis model based on node-to-node data transfer for a totally enclosed air over (TEAO) permanent magnet synchronous motor (PMSM) for a high-speed train (HST) distributed traction (DT). The study begins by highlighting the advantages of the DT-HST system and identifying the heat sources within the traction motor based on design requirements. A bi-directional coupled model is then introduced to evaluate the physical performance of the proposed traction motor under various operating conditions, including rated and continuous power ratings. This model combines electromagnetic and thermal models and utilizes node-to-node data transfer to update material characteristics, such as electromagnetic losses and temperature, ensuring accurate predictions of machine performance. The simulation results were used to develop a prototype, which was subsequently tested and compared against the simulation results. The comparison between the bi-directional simulation model and test results demonstrates good agreement in terms of temperature rise. Specifically, for the winding active and end parts, the temperature deviations between the bi-directional simulation and test results were found to be only 0.01%, 1.4%, and 1.7%, 1.8% for continuous and full-rated ratings, respectively. As for the ferromagnetic core, the deviations were 11% and 5.8%. Similarly, the PM temperature recorded by the test setup exhibited deviations of 3.3% and 8.3% compared to the simulation results under continuous and full-rated operations.

Railway electrification has posed a challenge for power quality in railway networks due to their unique characteristics. This research paper explores the impact of an inductor filter on high-order harmonic currents generated by the pulse-width modulation (PWM) converter in the traction drive of high-speed railway (HSR) systems. The paper begins by providing an overview of the traction power transfer system (TPTS) in a HSR and models a permanent magnet synchronous motor (PMSM) for traction applications. Then, a laboratory-based system (LBS) HSR is built to replicate the energy flow characteristics observed in a real-world HSR system. The LBS-HSR is modeled in Matlab/Simulink and is utilized to analyze the harmonic spectrum of current on the grid and motor terminal under various operating conditions. Furthermore, the paper investigates the impact of the inductor filter on other system components such as the input current of the converter and the voltage on the DC capacitor. Finally, a laboratory-based HSR system is developed on experiment and validated against the results obtained from the simulation model.

This paper presents a critical review of traction motors used for distributed traction (DT) applications in high-speed railways (HSR). The motor topologies that can be used for DT-HSR are presented. The advantages and disadvantages of each motor in terms of structural and electromagnetic performance are discussed from the perspective of motor design. A survey of the advancement of the HSR industry in South Korea is presented, and the required torque–speed profile for the HSR traction motors for the South Korean railway is studied. Along with the electromagnetic design, detailed structural modeling constraints such as the framing design, slot insulation, end-winding potting, and slot wedge modeling are explained.

The main goal of this paper is to design the shield ring for the Rogowski coil embedded in the UHV-class gas-insulated switchgear (GIS) spacer. Because the UHV-class GIS spacer holds the individual conducting wires adjacent, the Rogowski coil can be affected by electromagnetic interference from adjacent large sinusoidal currents. The purpose of a shield ring eliminates electromagnetic interference caused by adjacent sinusoidal currents so that the Rogowski coil can operate normally. We designed shield rings considering the material and geometry to reduce the electromagnetic influence from adjacent currents. Finally, we evaluated and compared the performances of shield rings in terms of material and geometry. Three dimensional (3-D) finite element analysis (FEA) was used to analyze the electromagnetic effects of the Rogowski coil.

A totally enclosed air over (TEAO) permanent magnet synchronous motor (PMSM) for the distributed traction (DT) application of high-speed train (HST) is developed in this work. A study on the usefulness of the DT-HST is performed first. Considering the design requirement, electromagnetic and thermal models of the proposed traction motor are developed to check the operation under different operating conditions such as the machine rated power ratings. Based on the simulation model a prototype is developed and validated against the simulation result.

The memory window (MW) of a metal-ferroelectric-semiconductor (MFS)-based ferroelectric field-effect transistor (FE-FET) is generally 2V c , where V c is the coercive voltage of the FE layer. When applying the program and erase voltages, adverse charge injection from the gate metal or the channel likely occurs. While the latter decreases the MW, the former may further increase it over 2V c , which is highly useful for the multilevel FE-FET. In this work, we propose a metal-insulator-ferroelectric-semiconductor (MIFS)-based FE-FET to widen the MW by providing additional charges at the gate metal/ferroelectric interface. When part of the injected charges are retained at the polarization switching, the V c increases, and thus, MW also increases. This is due to the additional voltage drop by the injected charge exchange at the moment of FE switching. For a given FE layer thickness, the MW of MIFS-stacked FE-FET was expanded by ∼55% compared to MFS-stacked FE-FET.

This paper introduces a novel hybrid analysis method based on 2-D finite element method (FEM) for analyzing surface permanent-magnet machine (SPM) with an overhang structure which the axial length of rotor exceeds that of the stator. The overhang results the enhanced torque and power density by simply adding extra permanent magnet (PM) in axial direction utilizing the spare length of rotor compared to the stator with end-turn coil. However, it causes the flux behavior in axial direction especially around end parts of the motor, with inevitably requiring a time-consuming 3-D FEM for the consideration of the non-uniform aspects. It must be computationally big burden for designers to use the 3-D FEM in whole design process. To deal with the problem, a novel analysis method based on 2-D FEM which utilizes a virtual remanence of PM derived from the magnetic equivalent circuit (MEC) analysis is proposed. This concept introduces the MEC considering the overhang effects and combines remanence with a numerical analysis model. The accuracy and usefulness of the proposed method are validated through 3-D FEM and experimental results.

This paper presents a 2-D analysis of synchronous reluctance motors (SynRMs) considering the end-plate effect. In an electric machine with a laminated steel core, an end-plate is often attached to the rotor core to support the structural robustness of the machine. End-plates occasionally comprise carbon-steel, which changes the magnetic behavior of the electric machine. Thus, an electric machine that utilizes the 3-D finite element analysis (FEA) should be designed to consider the comprehensive magnetic flux path. However, the application of 3-D FEA for the whole design process is computationally expensive. Therefore, we proposed a 2-D FEA-based design strategy that can consider the additional magnetic path of the end-plate for SynRMs. The proposed analysis method was developed based on the magnetic equivalent circuit analysis and d- and q-axis flux linkage calculation. The effectiveness of the proposed method was verified by presenting the actual design case of a SynRM and via an experimental study.

This paper presents a stepwise optimal design (SOD) for an interior permanent magnet synchronous motor (IPMSM) applied to electric vehicle traction, which sequentially utilizes a magnetic equivalent circuit (MEC), finite element analysis (FEA), and a newly proposed optimization algorithm. The design of an IPMSM for the traction motor of a fuel cell electric vehicle (FCEV) is challenging due to its tough requirements, such as high torque density, high efficiency, and low torque ripple; as a result, an iterative trial and error process is required. However, FEA, which is the most generally used analysis technique for electric machine design, has a drawback in terms of the analysis time required when being applied to the entire design process. In this regard, the proposed SOD is presented, which consists of initial, detailed, and optimal design stages, to design an IPMSM with a reasonable design time.

Abstract The ferroelectric field‐effect transistor (FeFET) is one of the leading contenders to succeed charge‐trap‐based flash memory (CTF) devices in the current vertically‐integrated NAND flash storage market. The operation of a FeFET is based on the field‐effect in the channel of the FET that is exerted by the uncompensated ferroelectric bound charge, which is also the fundamental source of the depolarization effect. This paper briefly reviews the current status of CTF‐based NAND flash memory as a benchmark for FeFET. Then, a one‐dimensional model based on a load‐line analysis of FeFET technology is presented. The paper subsequently deals with the two‐dimensional domain effect in nano‐sized NAND‐type FeFET devices. While NAND‐type FeFET operation is likely, current ferroelectric materials with high remanent polarization (Pr) of ∼10 μCcm‐2 and coercive field (Ec) of ∼1 MVcm‐1 are not feasible for use in such devices. This is fundamentally due to the high depolarization field induced by the unnecessarily high Pr, which not only destabilizes the memory state but also induces a severe interference effect between neighboring cells. Therefore, a new ferroelectric material with a moderately low Pr and higher Ec > ∼3 MVcm‐1 is necessary, along with structural innovation to minimize the interference effect.

Robot joint drive motors require high-torque and power densities due to their limited space. Surface mounted permanent magnet (SPM) motors are appropriate for a robot joint drive due to their advantages of ease of construction, high productivity, and high controllability. To utilise the limited space effectively, a rotor overhang structure (OS) is frequently used in SPM motors due the performance enhancement and simple fabrication. However, the OS effects do not increase linearly but converge when it becomes longer. To deal with problem, a flux-absorbing structure (FAS), which can effectively improve the performances even in case of a quite long OS by forming an effective flux path between the OS and stator can be used. However, the FAS results in different electromagnetic and thermal characteristics. In particular, there have been few studies on the thermal characteristics of the FAS, which can change motor performance considerably. Hence, a lumped parameter thermal network (LPTN) which can effectively consider the heat sources and heat transfer characteristics influenced by the use of FAS, is proposed. The feasibility of the FAS and the usefulness of the proposed LPTN was verified experimentally. The presented analyses and results here can be utilised in various high-torque-density application.

The recent demand for analogue devices for neuromorphic applications requires modulation of multiple nonvolatile states. Ferroelectricity with multiple polarization states enables neuromorphic applications with various architectures. However, deterministic control of ferroelectric polarization states with conventional ferroelectric materials has been met with accessibility issues. Here, we report unprecedented stable accessibility with robust stability of multiple polarization states in ferroelectric HfO2. Through the combination of conventional voltage measurements, hysteresis temperature dependence analysis, piezoelectric force microscopy, first-principles calculations, and Monte Carlo simulations, we suggest that the unprecedented stability of intermediate states in ferroelectric HfO2 is due to the small critical volume size for nucleation and the large activation energy for ferroelectric dipole flipping. This work demonstrates the potential of ferroelectric HfO2 for analogue device applications enabling neuromorphic computing.

In the interior permanent magnet synchronous motor (IPMSM) design for the traction motor of fuel cell electric vehicles (FCEVs), it is necessary to analyze the nonlinear characteristics including saturation due to the requirement of a high torque density. The finite element method (FEM) is the most widely used technique for electric machine designs because complicated computations can be taken into account. However, a large amount of analysis over the entire design is a computationally large burden. To address this problem, this paper proposes a fast and accurate analysis method, sequential-stage magnetic equivalent circuit (SSMEC). The proposed method consists of no-load, q-axis circuit analysis, d-axis circuit analysis, and motor characteristic calculation. Because the proposed method can quickly and accurately analyze the complex shapes of an IPMSM, it can be used effectively throughout the entire motor design process. The effectiveness of the proposed SSMEC was verified in comparing with experimental results.

This study presents a stepwise optimal design strategy (SODS) which effectively utilizes the magnetic equivalent circuit (MEC), the finite element method (FEM), and an optimization algorithm for the design of an interior permanent magnet synchronous motor for fuel cell electric vehicles (FCEV). The proposed strategy respectively uses the MEC, the FEM, and the optimization algorithm by dividing the entire design into the initial, detailed, and the optimal design stage. The proposed design strategy can be widely used as a design technique of electric machines since it can not only reduce computational cost but also accurately consider the diverse design cases.

The ferroelectric (FE) properties of 10-nm-thick Hf0.5Zr0.5O2 (HZO) films deposited by an atomic layer deposition technique were improved by adopting O3 as an oxygen source instead of H2O. All HZO films were annealed at 400 °C for 1 min in an N2 atmosphere after TiN top electrode deposition. Regardless of the oxygen source, the HZO films exhibited the formation of a noncentrosymmetric orthorhombic phase, which is responsible for FE behavior with the suppression of the monoclinic phase. However, compared to the O3-based HZO film, it was confirmed that the H2O-based HZO film was more incorporated with hydrogen derived from H2O, thereby degrading FE polarization and leakage behavior. The results indicate that the strategy of using O3 as the oxygen source is useful for the fabrication and integration of FE HZO films for next-generation memory applications.

A segmented-core (SC) structure has been widely used for high-power-density (HP) motors. However, the SC motor is associated with a number of problems due to the complexity of both the structure and the manufacturing process. To address these issues, a novel structure of a HP motor is proposed, referred to as the ring-coupled segmented-stator (RSS) model here. The proposed RSS can increase the reliability, the stability, and the manufacturability of motor. Furthermore, useful thermal analysis and design flow which take into account the RSS and asymmetric overhang structure of the motor are proposed in this research. The proposed lumped parameter thermal network (LPTN) for the thermal analysis shows a good agreement with experimental data within 9.8% difference. The proposed analysis and design method can be used for the diverse kinds of motor requiring the HP. The usefulness of the proposed RSS motor, the analysis method, and the design method are verified through the experiment in this research.

In electric machine design, there is a large computation cost for finite element analyses (FEA) when analyzing nonlinear characteristics in the machine Therefore, for the optimal design of an electric machine, designers commonly use an optimization algorithm capable of excellent convergence performance. However, robustness consideration, as this factor can guarantee machine performances capabilities within design uncertainties such as the manufacturing tolerance or external perturbations, is essential during the machine design process. Moreover, additional FEA is required to search robust optimum. To address this issue, this paper proposes a computationally efficient robust optimization algorithm. To reduce the computational burden of the FEA, the proposed algorithm employs a useful technique which termed static analysis assisted technique (SAAT). The proposed method is verified via the effective robust optimal design of electric machine to reduce cogging torque at a reasonable computational cost.