• Proceedings of the KIPE Conference
• /
• 2017.07a
• /
• pp.401-402
• /
• 2017

넓은 범위의 토크-속도 특성을 가지는 직류기는 소형에서부터 대형까지 다양한 산업분야에서 폭넓게 사용되고 있다. 이러한 직류기 중 영구자석으로 자기장을 형성하는 영구자석 직류기 (Permanent magnet dc motor, PMDC motor)의 제어방식에 대해 비교 분석했다. 가장 대중적으로 사용되고 있는 진폭 변조 방식 (PWM, Pulse Width Modulation)과 벅-부스트 컨버터 (Buck-Boost converter)를 이용한 직류기 제어 방식에 대해 비교했다. PWM 방식은 인버터를 이용하여 펄스폭을 변조하였고, 벅-부스트 컨버터를 이용하는 방식은 스위치의 듀티비를 제어하여 직류 전압의 크기를 조절하였다. 시뮬레이션 결과 벅-부스트 컨버터를 이용한 방식이 PWM 방식보다 5 rad/s 까지 정착 시간은 54.4 % 단축되었지만, 전력 소모는 194 % 증가하는 결과를 얻었다.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
• /
• v.28 no.7
• /
• pp.48-54
• /
• 2014

This paper discusses study of torque ripple minimization employing an improved TDF(torque distribution function)-based instantaneous torque control to reduce acoustic noise and vibration problem of the SRM. As the flux linkage of the SRM is a nonlinear function of phase current and rotor position, design of optimal controller for the SRM is quite complicated. Hence, an accurate mathematical model considering the nonlinearity of the SRM is required. An improved TDF based torque control has been proposed in order to reduce the toque ripple at high speed operation. Dynamic simulation using Matlab/Simulink as well as Finite Element Analysis is presented. A prototype SRM for electric vehicle traction has been manufactured to validate the experimental results comparing the dynamic simulation results.

• Proceedings of the KIEE Conference
• /
• 2005.07b
• /
• pp.921-923
• /
• 2005

본 논문은 LCD 제조 공정라인에서 LCD 원판을 이송하기 위한 영구자석 여자 횡자속형 선형 진동기 개발에 관한 내용이다. 3차원 등가 자기 회로망법과 2차원 유한 요소법을 사용하여 이동자의 단부 효과를 고려하여 전동기 특성을 해석하였으며 정특성 실험을 통하여 설계 및 해석의 타당성을 검증하였다.

• The Transactions of the Korean Institute of Power Electronics
• /
• v.6 no.4
• /
• pp.333-340
• /
• 2001

This paper presents a calculating method for inductance of the Switched Reluctance Motor(SRM) for torque characteristics and driving by analytical model. The torque generating characteristics of the SRM depend on the phase current and the inductance variation features, but Its nonlinear magnetic characteristics make it difficult to calculating inductance. Recently, The approaches for calculating inductance have taken vary from detailed finite element method(FEM) and Fitting method in magnetization curves using complex nonlinear magnetic circuit models. But those methods have not satisfactory approach for machine performance calculations, because of having a long time and remodeling for analyses, therefore thus an alternative approach is required. So it is suggested simply calculating method of the inductance based on designed data of machinery by analytical model in unaligned and aligned rotor. In order to prove the calculating, there are compare with analytical FEM. direct measurement, this method, and simulation. The compared result is shown to obtain good accuracy.

• The Journal of the Korea Contents Association
• /
• v.20 no.4
• /
• pp.464-474
• /
• 2020

This study provides basic data for nursing intervention to increase self management of hemodialysis patients by identifying the relation among their illness perception, physiological indicators, and self management. The participants were 134 patients receiving hemodialysis at a general hospital in Seoul. Data were collected by using a structured questionnaire and medical records. The collected data were analyzed by using descriptive statistics, independent t-test, one-way ANOVA, Pearson correlation coefficient and multiple regression analysis with the SPSS/WIN 23.0 program. The significant factors influencing self-management of hemodialysis patients have been identified with 8 variables. The first one is registration for kidney transplantation (β=-.20, p=.034). Among sub items of illness perception are consequence (β=-.20, p=.031), treatment control (β=.19, p=.040), and illness coherence (β=-.18, p=.049). In addition, among physiological indicators are hematocrit (β=.38, p<.001), hemoglobin (β=.29, p=.005), BUN (β=-.25, p=.010), and phosphorous (β=.22, p=.033). These variables explained 26.3% for self-management of hemodialysis patients. In order for hemodialysis patients to improve their self-management, a concrete nursing intervention improving the treatment control among illness perception as well as improving the understanding of physical indicators needs to be provided.

• Journal of the Korean Magnetics Society
• /
• v.9 no.4
• /
• pp.184-189
• /
• 1999

1000 $\AA$ thick Fe films were epitaxially grown on MgO(001) by an rf sputtering and effects of substrate temperature on the structural and magnetic properties were investigated. X-ray diffraction intensity increased with increasing substrate temperature and inter-planar spacing $d_{(002)}$ decrease with increasing the temperature up to 25$0^{\circ}C$. The increased intensity and decreased inter-planar spacing were thought to be attributed to the enhancement of lattice match between Fe films and MgO, thus yielding good epitaxial growth. By using torque magnetometer, VSM and pole figure, very nice epitaxial growth of sputtered Fe films on MgO could be confirmed and $K_1$ value of Fe films grown at 25$0^{\circ}C$ was $4.6{\times}10^5\;erg/cc$, which was very similar to that of bulk single Fe crystal.

• Journal of the Korean Magnetics Society
• /
• v.21 no.2
• /
• pp.48-51
• /
• 2011

We performed macro-spin simulation studies of the current-induced magnetization reversal of nanomagnetic elements with short current pulses. A special attention was paid to the effect of the energy barrier on the switching current distribution. The switching current and its distribution increase with decreasing the current pulse-width. The relationship between the energy barrier and switching current distribution is described by the Arrhenius-N$\'{e}$el law at a long pulse-width regime. At a regime of short pulse-width, however, the relationship is left unaddressed. The difficulty to address this issue arises because the magnetization switching with a short current pulse is governed not by the thermal activation but by the precession motion. Therefore, an exact formulation for the short pulse regime by solving the Fokker-Plank equation is needed to understand the result.

• The Proceedings of the Korean Institute of Illuminating and Electrical Installation Engineers
• /
• v.9 no.2
• /
• pp.58-67
• /
• 1995

The paper describes the variation of magnetic fields caused by the operation of induction motors. The measuring system consists of the self-integrating magnetic field sensor, amplifier, and active integrator. From the calibration experiments, the frequency bandwidth of the magnetic field measuring system ranges from 20[Hz] to 300[kHz] and sensitivity is 0.234(mV/$\mu\textrm{T}$]. The magnetic fields generated under steady state and starting operations of duction motor are recorded by the proposed measuring system, and the fast Fourier transformation(FFT) of the measured data is performed to analyze the harmonic components. A single pulsed magnetic field is strongly caused by direct starting the induction motor, and its peak value is greater than 5 times as compared with the steady state value. The long transient duration and high intensity originates from the large inductance and dynamic characteristic of the induction motor, During the steady state operation of induction motor, subharmonics of magnetic field components, which depend on the pole number of induction motor, are observed. The lower order power-line harmonics can be inferred from the voltage flicker and current ripple which are derived from the torque fluctuation of induction motor. In the case of the induction motor drived by inverter, the harmonics of magnetic field are much more than those caused by direct starting method and are found generally to increase with decreasing the driving frequency.

• Journal of Dental Rehabilitation and Applied Science
• /
• v.34 no.2
• /
• pp.80-88
• /
• 2018

Purpose: Implant surface modification and implant design are the principle targets for achieving successful primary stability. The aim of this study was to measure implant stability quotient (ISQ) values of sandblasted, large-grit, acid-etched (SLA) implants with tapered straight body design during the healing period, and to determine the various factors affecting implant stability. Materials and Methods: To measure implant stability, resonance frequency analysis (RFA) was performed in 26 patients (13 women and 13 men) with 44 SLA implants with tapered straight body design. Implant stability (ISQ values) was evaluated at baseline and healing abutment connection (12 weeks), and the correlations between RFA and insertion torque (IT), bone quality, and jawbone were determined. Results: The mean ISQ value of the implants was $69.4{\pm}10.2$ at the time of implant placement (baseline) and $81.4{\pm}6.9$ at the time of healing abutment connection (P < 0.05). Significant differences were found between RFA and bone quality and between RFA and jawbone (P < 0.05). No significant differences were found between RFA and IT, insertion area, fixture diameter, and implant length (P > 0.05). Conclusion: ISQ values of SLA implants with tapered straight body design were high at baseline and healing abutment connection. It was concluded that SLA implants with tapered straight body design show improved primary and secondary stability, and that immediate or early loading may be applicable.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.21 no.5
• /
• pp.77-83
• /
• 2020

4WD technology is being actively applied to passenger cars. Therefore, dry multi-plate clutches are used for transfer cases. On the other hand, dry clutches have problems related to large vibrations and poor ride quality. To solve this problem, this paper proposes a multi-plate clutch with an MR fluid. When fastening the multi-plate clutch in the transfer case, the proposed MR clutch was applied to reduce the shock and friction, which is a key component in a four-wheel-drive system. MR multi-plate clutch has a fluid coupling mode and a compression mode. A torque model equation was derived for the optimal design. The analysis was performed using Ansys Maxwell to optimize the design parameters of the multi-plate clutch. Electromagnetic field analysis confirmed the strength of the magnetic field when the number of disks and plates were changed, and the maximum strength of the magnetic field was 0.45 Tesla. By applying this to the torque equation, the spacing between the plates was 2 mm, and the inner and outer diameters of the plates were selected to be 45 mm and 55 mm, respectively. Overall, this paper proposes an optimal design technique to maximize the performance of an MR multi-plate clutch.