• Journal of Magnetics
• /
• 제21권3호
• /
• pp.405-412
• /
• 2016

In general, surface mounted PM synchronous motors (SPMSMs) are mainly adopted as a driving motor for high-speed applications, because they have high efficiency and high power density. However, the SPMSMs have some weak points such as the increase of magnetic reluctance and additional losses as a consequence of using a non-magnetic sleeve. Especially, the magneto-motive force (MMF) in the air-gap of the SPMSMs is weakened due to the magnetically increased resistance. For that reason, a large amount of PM is consumed to meet the required MMF. Nevertheless, it cannot help using the sleeve in order to maintain the mechanical integrity of a rotor assembly in high-speed rotation. Thus, in this paper, a multi-layer interior PM synchronous motor (IPMSM) not using the sleeve is presented and designed as an alternative of a SPMSM. Both motors are evaluated by test results based on a variety of characteristics required for an air blower system of a fuel cell electric vehicle.

• 전력전자학회:학술대회논문집
• /
• 전력전자학회 2004년도 전력전자학술대회 논문집(1)
• /
• pp.141-143
• /
• 2004

Distributed generation(DG) using microturbine will be adopted widely because of its various usages and merits such as high heat efficiency, environmental-friendliness. Commercialized DG using microtubine that rotates up to $60,000\~100,000[rpm]$ converters mechanical power to electricity by permanent magnet synchronous machine. This paper presents comparative test and simulation results of PMSM as generator. Test was done by diode rectifier and inverter. Parameters used in the simulation are driven from FEM analysis. Under various speed and load conditions, V-I characteristics matches well and it suggests the possibility of high speed PMSM as generator. DG operating at stand alone and grid connection mode will be developed.

• 전력전자학회:학술대회논문집
• /
• 전력전자학회 1998년도 Proceedings ICPE 98 1998 International Conference on Power Electronics
• /
• pp.482-487
• /
• 1998

Field orientation of rotating field machines is influenced by various machine parameters. Most unpleasant are those parameters which vary during machine operation, such as the stator and rotor resistances. Permanent influences of resistance variation in steady state operation could have serious consequences. Also transitory influences are often disturbing. In this paper a control method for a current-fed synchronous machine is presented in which both permanent and transitory parameter influences are suppressed as much as possible.

• 대한전기학회:학술대회논문집
• /
• 대한전기학회 1998년도 하계학술대회 논문집 F
• /
• pp.1973-1976
• /
• 1998

Recently, new trend in telecommunication device is to apply low voltage, about 3.3V-1.5V. However, it is undesirable in view of high efficiency and power desity which is the most important requirement in the distributed power system. Rectification loss in the output stage, in on-board converter for distributed power system are constrained to obtain high efficience at low output voltage power suppies. This paper explains the basic operational principles of three kinds of ZVS DC/DC converters with self-driven synchronous rectifier. The three topologies are analyzed by simulation and exprimentation, and the characteristics comparisons of high efficience converter are carried out in view of the minimized rectification losses in the out stage.

• 대한전기학회:학술대회논문집
• /
• 대한전기학회 2007년도 제38회 하계학술대회
• /
• pp.919-920
• /
• 2007

Currently national High Voltage Gas Insulated Switchgear (GIS) operating mechanism is made up of spring operating mechanism or hydraulic operating mechanism. On the contrary, advanced technology trend in foreign countries replace current mechanical mechanism with electrical motor-drive mechanism that leads to participate GIS bid and increase sales with the point of simplification of driving system and IT application. Therefor it is essential to develop high voltage GIS using the motor-drive system to develop national heavy electric machine industries and catch up the technology to the advanced level. This paper therefore presents design and analysis of permanent synchronous motor for high voltage GIS, verifies the performance by the experimental test.

• 한국응급구조학회지
• /
• 제25권2호
• /
• pp.157-167
• /
• 2021

Purpose: The study was a qualitative study to examine the synchronous and asynchronous distanced learning experience of online paramedic students during the COVID-19 pandemic. Methods: The subjects included 10 students enrolled in the department of emergency medical service at J City C University. Written consent was provided by the subjects prior to the study, and focus group interviews were then conducted with sufficient explanation. The interviews were recorded and were directly transcribed immediately after the interview. Research results were then derived through content analysis. Results: A total of 4 domains and 9 categories were derived from the experiences of paramedic students on distanced learning. The 4 domains included "distanced lectures type," "student's adaptation and non-adaptation," "change of evaluation," and "learning anxiety." Conclusion: Contents of each domain derived from this study are expected to be used as basic data for the design of the distanced learning in the future.

• 한국인터넷방송통신학회논문지
• /
• 제15권4호
• /
• pp.1-7
• /
• 2015

지금까지 대부분의 코칭은 대면 중심으로 이루어졌으나, 인터넷을 활용한 e-코칭으로 확장이 시도되고 있다. 현재 e-코칭은 대면 코칭을 위한 보조 역할을 수행하고 있다. 따라서 코치와 피코치 간의 수평적 관계에서 언제 어디서나 소통할 수 있는 e-코칭 시스템의 개발이 요구되고 있다. 기존의 e-코칭은 전자문서, 비디오 채팅, 문자 채팅, 전화 등의 네 가지 형태가 일반적이다. 대부분의 e-코칭 방식은 접근성이 용이하나, 비디오 채팅은 우수한 가시성을 제공하나 동기방식을 요구한다. 이에 반해 전자 메일은 비동기 방식이며, 문서 작성 중심이다. 본 논문에서는 동기와 비동기를 지원하는 통합 e-코칭 시스템을 설계하고 구현한다. 제안한 e-코칭 시스템은 비동기 방식의 전자 메일과 동기 방식의 P2P(Peer to Peer) 비디오 채팅과 그룹 문자 채팅을 지원한다. 이를 통해 비동기와 동시적인 방법을 함께 지원하여 개인 혹은 그룹 간의 규칙적, 비공식적 코칭이 가능할 수 있다.

• KIEE International Transaction on Electrical Machinery and Energy Conversion Systems
• /
• 제12B권1호
• /
• pp.1-6
• /
• 2002

The severe problem in improving the positioning precision of a permanent magnet linear synchronous motor (PMLSM) is the large detent farce caused by the permanent magnet arrangement. It is generally an undesired effect that contributes to the torque ripple, vibration and noise of machine. The detent force is arisen from the difference of the position of a permanent magnet end and a tooth position. In this paper, the four methods to reduce detent force were studied and analyzed. The methods are adjusting the width of permanent magnet, varying the shape of armature teeth, relocating the permanent magnet, and adjusting the width of permanent magnet and relocating the permanent magnet at the same time. To analyze the detent farce according to flour methods, a two-dimensional Finite Element Analysis [FEA] was used and we compared with the ratio of reduction of the detent farce according to the flour methods.

• KIEE International Transaction on Electrical Machinery and Energy Conversion Systems
• /
• 제5B권3호
• /
• pp.253-257
• /
• 2005

By using a coupled circuit, time-stepping, two-dimensional finite element method (2-D FEM), the performance of a stand-alone permanent-magnet synchronous generator (PMSG) with inset rotor can be computed without involving the classical two-axis model. The effects of interpolar air gap length and armature resistance on the load characteristics are investigated. It is shown that the interpolar flux density, and hence the amount of voltage compensation, is affected by magnetic saturation. Validity of the coupled circuit and field analysis is confirmed by experiments on a prototype generator. The machine exhibits an approximately level load characteristic when it is supplying an isolated unity-power-factor load.

• ETRI Journal
• /
• 제37권4호
• /
• pp.657-666
• /
• 2015

We propose a two-stage resource allocation algorithm for the high link utilization of an orthogonal frequency-division multiplexing passive optical network (OFDM-PON). An OFDM-PON is assumed to use a synchronous frame structure in supporting service differentiation. In distributing resources, the proposed algorithm first allocates a time window for each optical network unit (ONU), and then it arranges a subchannel, which is a group of subcarriers. This algorithm needs to satisfy two constraints. First, computations for the resource allocation should be done using a frame unit. Second, an ONU has to use a single subchannel to send upstream data for multiple services within a frame duration. We show through a computer simulation that the proposed algorithm improves the link utilization.