Search

The recent focus on greenhouse gas emissions from fossil fuel usage has led to strengthened regulations on carbon emissions. Consequently, research on electric vehicles (EV), which have higher energy efficiency compared to internal combustion engine vehicles, is actively being pursued. With advancements in the technology of electronic components in electric vehicles, there is a growing trend in the demand for higher-rated capacities of Low DC-DC Converter (LDC) that possess a wide input-output voltage range. Furthermore, the restricted space within vehicles and the emphasis on high energy utilization necessitate converters with high power density and efficiency. Currently, in electric vehicles, the Active Clamp Forward Converter (ACFC) and the Phase Shift Full-Bridge Converter (PSFB) are commonly applied, as they readily achieve a wide input-output voltage range and high power density. However, ACFC and PSFB encounter difficulties in achieving high efficiency and power density due to the requirement for output inductors with high current specifications. To address these challenges, this study proposes a Two-Transformer Phase Shift Full-Bridge Converter (2-TR PSFB) based on planar transformers, which can replace conventional ACFC and PSFB. The proposed converter achieves high efficiency and power density without the need for high-current output inductors. Additionally, the utilization of GaN power semiconductors allows for a high switching frequency, enabling a significant reduction in the volume of magnetic components. This research presents the operational principles of the 2-TR PSFB and provides design directions. To validate the design, a 2.5 kW prototype was manufactured and tested.

With increasing worries about the environment, there is a rising focus on saving energy in various industries. In the e-mobility industry of electric motors, permanent magnet synchronous motors (PMSMs) are widely utilized for saving energy due to their high-efficiency motor technologies. However, challenges like environmental degradation from rare earth development and difficulties in controlling magnetic field fluctuations persist. To address these issues, active research focuses on the wound field synchronous motor (WFSM), known for its ability to regulate field current efficiently across various speeds and operating conditions. Nevertheless, compared with other synchronous motors, the WFSM tends to exhibit relatively lower efficiency and torque density. Because the WFSM involves winding both the rotor and the stator, it results in increased copper and iron losses. In this article, a model that enhances torque density by inserting permanent magnets (PMs) into the rotor of the basic WFSM is proposed. This proposed model bolsters the d axis magnetic flux, thereby enhancing the motor’s overall performance while addressing environmental concerns related to rare-earth materials and potentially reducing manufacturing costs when compared with those of the PMSM. The research methodology involves a comprehensive sensitivity analysis to identify key design variables, followed by sampling using optimal Latin hypercube design (OLHD). A surrogate model is then constructed using the kriging interpolation technique, and the optimization process employs a micro-genetic algorithm (MGA) to derive the optimal model configuration. The algorithm was performed to minimize the use of PMs when the same torque as that of the basic WFSM is present, and to reduce torque ripple. Error assessment is conducted through comparisons with finite element method (FEM) simulations. The optimized permanent-magnet-assisted WFSM (PMa-WFSM) model improved efficiency by 1.08% when it was the same size as the basic WFSM, and the torque ripple decreased by 5.43%. The proposed PMa-WFSM derived from this article is expected to be suitable for use in the e-mobility industry as a replacement for PMSM.

This paper presents optimal rotor permanent magnet (PM) and rotor pole-piece skew to improve the total harmonic distortion (THD) of the back electromotive force (Back-EMF) in magnetic geared permanent magnet synchronous motor (MG-PMSM) for traction. MG-PMSM is a system that integrates a magnetic gear and a PMSM which can minimize the size of the driving system and reduce power loss because there is no mechanical friction unlike the existing motor. For this reason, it is more advantageous in terms of output density and efficiency. However, MG-PMSM has a pole-piece rotor for magnetic flux modulation, which can produce additional spatial harmonics in back electromotive force (back-EMF). In addition, this motor has inevitable to have a salient permanent magnet structure for the stator due to magnet loss, and in the case of winding methods, fractional slot concentrated winding (FSCW) is mainly used, which also causes additional harmonics. THD in back-EMF adversely affects torque ripple and make accurate position control difficult. Therefore, in this paper, THD in back-EMF is reduced by focusing on the optimal rotors skew. Considering the characteristics of MG-PMSM, skew is applied to each rotor, and then compared and analyzed with the proposed model.

This paper reports the design of a magnetic-geared permanent magnet synchronous motor (MG-PMSM) for a 45 kW tram traction system based on high torque density. In the case of the existing tram driving system, due to mechanical reduction gear and induction motor, it causes power transmission loss, low efficiency, and difficulty in lightweight. To solve this problem, research on the MG-PMSM, which combines a contactless magnetic gear with a high-power-density PMSM, is being actively conducted. This motor has a double rotor structure, and the inner rotor, including permanent magnet, and the outer rotor composed of pole-pieces rotate at different mechanical speeds. However, it is hard to design a tram driving system with a high torque density within limited conditions, because only one rotor in MG-PMSM is used as an output. In addition, there is no study conducted from basic design to final design, including gear ratio and topology selection in MG-PMSM for tram. Therefore, this paper presents the design process of MG-PMSM with high torque density to be applied to the 45 kW–class tram driving system. After designing the magnetic gear part that increases torque and efficiency by selecting an appropriate topologies-and-gear ratio that meets the constraints, the final finite elements method (FEM) model and electromagnetic field analysis results were derived by considering the number of poles and the number of slots. Through this, we confirmed that it is superior in output characteristics compared to the existing induction motor + mechanical gear.

Research on the magnetic levitation driving system of Hyperloop which has emerged as the next new vehicle is being carried out. Recently, magnetic levitation driving systems use EMS (Electro-Magnetic Suspension) and EDS (Electro-Dynamic Suspension) methods, and both EMS and EDS methods use two or more systems for propulsion/levitation/guidance. However, using two or more driving systems cause complexity of structure of whole system and increase significantly maintenance costs. Therefore, to solve these problems, this study proposed the concept and structure of Double-Sided Linear Induction Motor (DSLIM) that can be generating propulsion/levitation/guidance in one system, and carried out basic design and performance analysis by analyzing the design requirements of DSLIM. In addition, a detailed design through the selection of design parameters and analysis of characteristics that significantly affect the output characteristics was carried out to derive a performance improvement model for DSLIM.

Unlike the conventional railway traction motor, the concept of the dual-rotor in a dual-rotor permanent magnet synchronous motor (DR-PMSM) is that two rotors are mounted on the same rotation axis, and the outer rotor and the inner rotor rotate at different speeds. The DR-PMSM can transmit the power to the wheels in a structure that can cope with various problems of the reducer systems using mechanical gear mechanisms. In this research, the design study of the inner rotor including the permanent magnet is carried out in the application of the DR-PMSM. In designing the DR-PMSM models, surface permanent magnet (SPM) type and interior permanent magnet (IPM) type are considered according to the permanent magnet type of rotor, and IPM type is designed by dividing into bar type and V type. A comparative analysis of the three 1kW-class DR-PMSM models, in terms of electromagnetic properties, is performed to assess their general performance. The overall electromagnetic properties of the three designed models are similarly derived. But, the cogging torque and the rated torque characteristics of the IPM (V) type model are the best in comparison with the other models. In addition, the 1kW-class DR-PMSM prototype with V type magnet is fabricated to verify the validity of the analytical model and performance verification is performed.

Conventional diesel railway vehicles produce many air pollutants. In order to solve this problem, railway vehicles using eco-friendly hydrogen fuel cells are emerging. The main difference from the conventional traction motor is that it does not control the phase back electromotive force (phase-BEMF) separately at the maximum speed. Because of this, it should reduce the use of permanent magnets yet increase their size due to necessary high current. This paper performs the interior permanent magnet synchronous motor (IPMSM) design to meet the harsh electrical and mechanical constraints. Although the basic design is carried out to satisfy the design constraints, structural problems occur. These are resolved through the optimization process to attain the optimal design of a 314kW-class IPMSM for railway vehicles using hydrogen fuel cells.

Age-related decline in mitochondrial function and oxidative stress plays a critical role in neurodegeneration. Lactate dehydrogenase-B (LDHB) is a glycolytic enzyme that catalyzes the conversion of lactate, an important brain energy substrate, into pyruvate. It has been reported that the LDHB pattern changes in the brain during ageing. Yet very little is known about the effect of LDHB deficiency on brain pathology. Here, we have used Ldhb knockout (Ldhb−/−) mice to test the hypothesis that LDHB deficiency plays an important role in oxidative stress-mediated neuroinflammation and neurodegeneration. LDHB knockout (Ldhb−/−) mice were generated by the ablation of the Ldhb gene using the Cre/loxP-recombination system in the C57BL/6 genetic background. The Ldhb−/− mice were treated with either osmotin (15 μg/g of the body; intraperitoneally) or vehicle twice a week for 5-weeks. After behavior assessments, the mice were sacrificed, and the cortical and hippocampal brain regions were analyzed through biochemical and morphological analysis. Ldhb−/− mice displayed enhanced reactive oxygen species (ROS) and lipid peroxidation (LPO) production, and they revealed depleted stores of cellular ATP, GSH:GSSG enzyme ratio, and downregulated expression of Nrf2 and HO-1 proteins, when compared to WT littermates. Importantly, the Ldhb−/− mice showed upregulated expression of apoptosis mediators (Bax, Cytochrome C, and caspase-3), and revealed impaired p-AMPK/SIRT1/PGC-1alpha signaling. Moreover, LDHB deficiency-induced gliosis increased the production of inflammatory mediators (TNF-α, Nf-ĸB, and NOS2), and revealed cognitive deficits. Treatment with osmotin, an adipoR1 natural agonist, significantly increased cellular ATP production by increasing mitochondrial function and attenuated oxidative stress, neuroinflammation, and neuronal apoptosis, probably, by upregulating p-AMPK/SIRT1/PGC-1alpha signaling in Ldhb−/− mice. In brief, LDHB deficiency may lead to brain oxidative stress-mediated progression of neurodegeneration via regulating p-AMPK/SIRT1/PGC-1alpha signaling, while osmotin could improve mitochondrial functions, abrogate oxidative stress and alleviate neuroinflammation and neurodegeneration in adult Ldhb−/− mice.

In this paper, to complement the capability of the existing heating system using an electric-heating wire for melting snow and ice in railway turnouts, 250kHz-200W-class Induction Heating (IH) system was designed. The IH system consists of the resonant inverter and the IH device. In order to perform the electric circuit, the electromagnetic field, and the thermal analysis, the Multi-Physics analysis for IH system was derived. In addition, IH system was compared with the existing heating system.

The magnetic geared permanent magnet synchronous motor (MG-PMSM) is a PMSM that has two rotors with different rotation speeds and includes the function of magnetic gear. The design studies of the 45kW-class MG-PMSM are conducted for the application of the driving system for a tram. In this research, first, to derive the detailed model of the 45kW-class MG-PMSM for the tram, the analysis of the characteristics according to the stator winding method was performed. After selecting the winding method that can reduce the size of the MG-PMSM, two design topologies were applied to determine the number of stator poles, the number of outer rotor pole pieces, and the number of inner rotor poles of the MG-PMSM. A 45kW-class MG-PMSM detailed model was derived by applying a design topology that can minimize the size of the MG-PMSM, and it was confirmed that the required performance is satisfied through electromagnetic characteristics analysis. In addition, the 4.5kW-class small-scaled MG-PMSM prototype with concentrated winding was manufactured to verify the validity of the analytical model, and performance verification was performed.