• Journal of Magnetics
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• v.20 no.2
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• pp.148-154
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• 2015

48-V ISG (Integrated Starter Generator) system has attracted attention to improve the fuel efficiency of ICE (Internal Combustion Engine) vehicle. One of the key components that significantly affects the cost and performance of the 48-V ISG system is the motor. In an ISG motor, the core and copper loss make the motor efficiency change because the motor has a broad driving operated range and more diverse driving modes compared with other motors. When designing an ISG motor, the selection of an electrical steel sheet is important, because the electrical steel sheet directly influences the efficiency of the motor. In this paper, the efficiency of the ISG motor, considering core loss and copper loss, is analyzed by testing different types of electrical steel sheets with respect to the driving speed range and mode. Using the results of a finite element method (FEM) analysis, a method to select the electrical steel sheet is proposed. This method considers the cost of the steel sheet and the efficiency according to driving mode frequency during the design process of the motor. A wound rotor synchronous machine (WRSM) was applied to the ISG motor in this study.

• Transactions of Materials Processing
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• v.30 no.2
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• pp.91-98
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• 2021

The present study deals with the microstructure and mechanical properties of 700 MPa-grade high-strength seismic resistant reinforced steel bars fabricated by various TempCore process conditions. For the steel bars, in the surface region tempered martensite was formed by water cooling and subsequent self-tempering during TempCore process, while in the center region there was ferrite-pearlite or bainite microstructure. The steel bar fabricated by the highest water flow and the lowest equalizing temperature had the highest hardness in all regions due to the relatively fine microstructure of tempered martensite and bainite. In addition, the steel bar having finer microstructures as well as the high fraction of tempered martensite in the surface region showed the highest yield and tensile strengths. The presence of vanadium precipitates and the high fraction of ferrite contributed to the improvement of seismic resistance such as high tensile-to-yield strength ratio and high uniform elongation.

• Transactions on Electrical and Electronic Materials
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• v.16 no.1
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• pp.37-41
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• 2015

The most common structure of the current transformer (CT) consists of a length of wire wrapped many times around a silicon steel ring passed over the circuit being measured. Therefore, the primary circuit of CT consists of a single turn of the conductor, with a secondary circuit of many tens or hundreds of turns. The primary winding may be a permanent part of the current transformer, with a heavy copper bar to carry the current through the magnetic core. However, when the large current flows into a wire, it is difficult to measure its magnitude of current because the core is saturated and the core shows magnetic nonlinear characteristics. Therefore, we proposed a newly designed CT which has an air gap in the core to decrease the generated magnetic flux. Adding the air gap in the magnetic path increases the total magnetic reluctance against the same magnetic motive force (MMF). Using a ferrite core instead of steel also causes the generation of low magnetic flux. These features can protect the magnetic saturation of the CT core compared with the steel core. This technique can help the design of the CT to obtain a special shape and size.

• Earthquakes and Structures
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• v.15 no.4
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• pp.351-360
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• 2018

Energy-based methodology is utilized to design novel timber-steel hybrid core wall system. The timber-steel core wall system consists of cross laminated timber (CLT), steel columns, angled brackets and t-stub connections. The CLT wall panels are stiff and strong, and ductility is provided through the steel t-stub connections. The structural system was modelled in SAP2000 finite element program. The hybrid system is explained in detail and validated using first principles. To evaluate performance of the hybrid core system, a 7-story building was designed using both forced-based design and energy based design (EBD) approaches. Performance of the structure was evaluated using 10 earthquakes records selected for 2500 return period and seismicity of Vancouver. The results clearly served as a good example of the benefits of EBD compared to conventional forced based design approaches.

• Proceedings of the KIEE Conference
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• summer
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• pp.881-883
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• 2004

The high efficiency for motors has been continuously required for energy saving. The iron losses occurring in motor cores account for high percentage in the energy losses of motors, so that electrical steels with lower iron losses have been desired as core materials. It is necessary to understand the basic charecteristic of the electrical steel to design motors and establish manufacturing process for the loss reduction. Therefore, this paper deal with the basic characteristic related with the magnetic properties of electrical steels and descibes the cause of core loss in electrical machines.

• Proceedings of the Korea Concrete Institute Conference
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• 1995.10a
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• pp.210-214
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• 1995

Research on concrete-filled steel columns has been conducted. It is also well known that the load and deformation capacity of concrete-filled steel columns are considerable larger than those of widely used reinforced concrete columns and steel encased concrete columns because the concrete core in the steel is confined laterally by the steel. But, most of these works focused on columns with strength enhancement by the confinement effect, so that no local buckling prevented by the concrete. columns because the concrete core in the steel is confined laterally by the steel. But, most of these works focused on columns with strength enhancement by the confinement effect, so that no local buckling prevented by the concrete. This paper, therefore, presents on the stress-strain relation of a concrete filled rectangular steel tube under axial compression. As the results, the axial load verse average axial strain relationship of concrete-filled rectangular steel columns were very stable. The small B/t ratios in concrete-filled rectangular steel columns aren't affected prevention of local buckling but strength enhancement by confinement effect.

• Steel and Composite Structures
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• v.21 no.3
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• pp.461-477
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• 2016

Steel-concrete-steel (SCS) sandwich composite wall has been proposed for building and offshore constructions. An ultra-lightweight cement composite with density1380 kg/m3 and compressive strength up to 60 MPa is used as core material and inter-locking J-hook connectors are welded on the steel face plates to achieve the composite action. This paper presents the numerical models using nonlinear finite element analysis to investigate the load displacement behavior of SCS sandwich walls subjected to axial compression. The results obtained from finite element analysis are verified against the test results to establish its accuracy in predicting load-displacement curves, maximum resistance and failure modes of the sandwich walls. The studies show that the inter-locking J-hook connectors are subjected to tension force due to the lateral expansion of cement composite core under compression. This signifies the important role of the interlocking effect of J-hook connectors in preventing tensile separation of the steel face plates so that the local buckling of steel face plates is prevented.

• Steel and Composite Structures
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• v.19 no.5
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• pp.1321-1331
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• 2015

A square steel sandwich plate with lattice corrugated core is explored for damping improvement. A range of damping materials are filled inside the openings provided by the corrugated core, or are applied on the surfaces of the facesheets. The dynamic properties such as natural frequency and damping factor are experimentally measured for the sandwich plate with each filling solution. The relative performance of each insertion is compared in terms of damping capacity and added mass.

• Journal of the Korean Society for Heat Treatment
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• v.24 no.4
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• pp.209-216
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• 2011

Surface coatings were prepared on SKD11 core mold steel by plasma electrolytic oxidation (PEO). The coatings were investigated about the formation condition of core mold steel. SKD11 were coated by PEO in a mix solution of Sodium Aluminate $NaAlO_2$ (10 g/l), Sodium Silicate powder $Na_2SiO_3$ (0.5 g/l), Sodium tungstate dihydrate $Na_2WO_42H_2O$ (0.5 g/l) at less than $30^{\circ}C$. The electrical condition were voltage : 500~600 V; Pulse : 600~1800 Hz; current density 15~20 $A/dm^2$ various time : 3 min~40 min. The coatings surface morphology, cross-section, friction coefficient, hardness were investigated. The PEO coatings on SKD11 core mold steel showed the extended service life.

• Proceedings of the KIEE Conference
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• 2009.07a
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• pp.887.1_888.1
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• 2009

This paper proposes a core loss analysis method to obtain high accuracy prediction by using Multi-curve representing magnetic properties of a electrical steel in Finite Element Analysis (FEA). Generally, the magnetic prosperities of the electrical steel are measured by Epstein Method based on the international standards that are not good sufficient to predict motor performances. The method only aims to grade products in steel companies The magnetic properties of actual stator core is highly different to those given by steel companies due to the fact that stacking effect, shearing stress, nature anisotropy of electrical steels are not taken into account. In this paper, the magnetic properties are variously measured by three measuring devices, and then the several BH curves and BW curves obtained are used to analyze the core loss of a IPM. The BH curve in the high magnetic field are extrapolated using the mathematical formulation with the maximum saturation magnetic polarization measured