• 동력기계공학회지
• /
• 제14권2호
• /
• pp.60-64
• /
• 2010

This paper introduces reliability improvement and time saving in eddy current inspection by signal characteristic optimization of multi-coil eddy current array probe. In the past, Multi-coil array probe and single probe were used for the gas turbine rotor surface inspection & defect evaluation. The multi-coil array probe was used for the broad area inspection. But the signal deviations among multi-coil array probe are maximum 28% in commercial probe. This differences were considered to impedance differences among coils, so it is very difficult to evaluate exact defect size. The signal deviations among multi-coil array probe are maximum 28% in commercial probe. So, single coil inspection was used for exact defect sizing. The purpose of this study is to improve signal deviations of multi-coil array probe. The introduced new technology can improves this deviation by adjusting input voltage in each coil. At first, apply same voltage in each coil and collect signal amplitude of each coil. And calculate new input voltage based on signal amplitude of each coil. If the signal amplitude deviation is within 5% among multi-coil array probe, the signal amplitude of multi-coil array probe is reliable. The proposed technology gives 2% signal deviation among multi-coil array probe. The proposed new technology gives reliability improvement and inspection time saving in eddy current inspection.

• 한국전자파학회논문지
• /
• 제19권6호
• /
• pp.603-611
• /
• 2008

본 논문에서는 유도 결합을 이용한 RFID 시스템에서 주변의 RF 잡음의 영향을 감소할 수 있는 다중 코일 안테나를 새로이 제안하고 실험하였다. 다중 코일 안테나는 1개의 중심 코일과 그 주변에 4개의 보조 코일이 등거리에 배치되어 구성되며, 이들을 직렬로 연결하여 중심 코일과 보조 코일에 유도되는 전압이 서로 상쇄되도록 설계된 구조이다. 다중 코일 안테나를 사용한 경우에 단일 코일 안테나에 비하여 유도 잡음이 약 30 dB 감소하였으며, 잡음의 공간적 분포가 급격히 변화하는 환경에서도 유도 잡음의 소거 효과가 매우 높아 이중 코일에 비하여 유도 잡음이 약 16 dB 감소하였다.

• 동력기계공학회지
• /
• 제15권3호
• /
• pp.65-69
• /
• 2011

This paper introduces the multi-coil eddy current sensor and its characteristic in magnetic material gas turbine rotor. In the past, magnetic particle inspection method was used for qualitative defect evaluation in magnetic material gas turbine rotor. And the ultrasonic inspection method was used for quantitative defect evaluation. Nowadays, eddy current method is used in magnetic gas turbine rotor inspection due to advanced sensor design technology. We developed multi-coil eddy current sensor for the rotor dovetail inspection. At first, rotor stress is analyzed for the determination of sensor position and number. The sensor coils are designed to cover the stress concentration area of rotor dovetail. We select optimum frequency according to material standard penetration data and experiment results. The rotor mock-up and artificial defects were made for the signal detection and resolution analysis of multi-coil eddy current sensor. The results show that signal detection and resolution capabilities are enhanced in comparison to the commercialized sensor enough for the gas turbine rotor inspection. So, this developed multi-coil eddy current sensor substituted for commercialized one and it applied in real gas turbine rotor inspection.

• 한국자동차공학회논문집
• /
• 제8권3호
• /
• pp.151-162
• /
• 2000

This study is concerned with computerized multi-level substructuring methods and stress analysis of coil springs. The purpose of substructuring methods is to reduce computing time and capacity of computer memory by multiple level reduction of the degrees of freedom in large size problems that are modeled by three dimensional continuum finite elements. In this paper, the spring super element developed is investigated with tension, torsion, and bending of a cylindrical bar in order to verify its accuracy and efficiency for the multi-level substructuring method. And then the algorithm is applied to finite element analysis of coil springs. The result demonstrates the validity of the multi-level substructuring method and the efficiency in computing time and memory by providing good computational results in coil spring analysis.

• 전력전자학회논문지
• /
• 제25권3호
• /
• pp.162-170
• /
• 2020

In this paper, we report our study of the current measuring technique by implementing a pick-up coil in the PCB pattern instead of the current measuring sensor in a power converter using a WBG device. The proposed PCB pattern coil structure has a higher mutual inductance value than the conventional pattern by constructing the coil using the multi layer board. It has high sensitivity and is configured without additional process outside the PCB. In the current measurement, the integrator is measured by integrating the coil at the back end and the current waveform measured using proposed pick-up coil is confirmed by comparing it with the original current waveform through DPT simulation.

• 전력전자학회논문지
• /
• 제24권2호
• /
• pp.78-83
• /
• 2019

In this study, we analyze the structure of the transceiver coil in the inductive power transfer (IPT) system. In the IPT system, the transceiver coil design needs to have the highest magnetic coupling possible because of the relatively low magnetic coupling due to the large gap of distance without the core. The transmitting coil may be formed as a multi-layer type according to the distance between the transmitting and receiving coils if the receiving coil is configured as a multi-layer type on the inner structure of the receiving apparatus, thereby improving the magnetic coupling and system efficiency. We compare and analyze the coil magnetic coupling, and system efficiency according to the layer structure of the transmitting and receiving coils and verify the analysis by JMAG simulation. Experimental results show that the layer structure of the transceiver should be considered according to the inner space of the receiving device and the spacing distance.

• 한국산학기술학회논문지
• /
• 제11권12호
• /
• pp.4891-4895
• /
• 2010

본 자기공명영상장치(MRI: Magnetic Resonance Imaging)의 구성 요소인 RF Coil의 성능은 영상의 신호대 잡음비(Signal to Noise Ratio)를 결정하는 장치이다. RF Coil의 성능은 민감도(Sensitivity)와 라디오주파수 필드 균질성(RF Field Uniformity)으로 나타내고, RF Coil에 의해 유기되는 라디오 주파수 자기장(B1 Field)의 세기는 RF Coil의 구조 및 배열에 따라 공간적으로 달라진다. MRI 신호의 크기는 RF Coil이 만들어내는 자기장의 세기에 의해 결정되기 때문에 RF Coil에 의해 형성되는 공간상의 B1 Field의 분포를 확인할 수 있어야 한다. 본 논문에서는 다채널 RF Coil 설계에 있어서 가장 기본이 되는 형태의 RF Coil 구조와 이의 B1 Field 분포를 Matlab을 이용하여 모의실험을 통해 확인 하였다. Matlab을 이용하여 계산된 기본 구조의 RF 코일이 형성하는 B1 Field 분포는 다채널 RF 코일 설계시 매우 유용하게 사용될 수 있을 것이다.

• 대한전기학회논문지:전기기기및에너지변환시스템부문B
• /
• 제50권6호
• /
• pp.273-281
• /
• 2001

In order to overcome the demerit and to improve the operation characteristics of Moving Coil type Linear Oscillatory Actuator(MC-LOA) with single-pole permanent magnet, this paper presents two models having the balanced magnetic circuit by multi-pole permanent magnet. They are short coil type with two-pole single-sided and two-ple double-sided permanent magnet. The characteristics between single-pole and multi-pole permanent magnet type MC-LOA are compared. As a result, multi-pole type MC-LOA has more merits than single-pole type about operation characteristics improvement and machine volume. The characteristics analysis is performed by their dynamic analysis composed of kinetic and electric equations and Finite Element Method(FEM). The propriety of multi-pole type MC-LOA model is verified with analysis results.

• 한국자동차공학회논문집
• /
• 제8권2호
• /
• pp.138-150
• /
• 2000

This study is concerned with computerized multi-level substructuring methods and stress analysis of coil springs. The purpose of substructuring methods is to reduce computing time and capacity of computer memory by multiple level reduction of the degrees of freedom in large size problems which are modeled by three dimensional continuum finite elements. In this paper, a super element has been developed for stress analysis of coil springs. The spring super element developed has been examined with tension and torsion simulation of cylindrical bars for demonstrating its validity. The result shows that the super element enhances the computing efficiency while it does not affect the accuracy of the results and it is ready for application to the coil spring analysis.

• Journal of Electrical Engineering and Technology
• /
• 제7권6호
• /
• pp.926-931
• /
• 2012

Since robot industry growing, the machine that could move with multi-DOF has been studied in many industrial fields. Spherical motor is one of the multi-DOF machine that doesn't need gear for multi-DOF motion. Unlike conventional motor, spherical motor can not only rotate on the shaft axis (rotating motion), but tilt the shaft with 2-DOF motion (positioning motion). In the typical type of spherical motor, one coil took part in positioning motion and rotating motion at the same time. As the result, the control algorithm was complex. To solve this problem, this study proposed a novel type of coil on the stator. The coils were separated for positioning motion and rotating motion. Thus the linkage flux of rotating coil didn't be affected the positioning angle. In this paper, comparing the back-EMF of typical and novel type was conducted and the driving experiment was carried out as the positioning angle. From the experiment result, the performance of proposed spherical motor could be verified.