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| We have two types of electric source : AC(Alternating Current) and DC(Direct Current). AC is a sinusoidal current alternating 60 times a second of which power is usually producted by power-stations. It is used commercially on account of the easiness to generate and to transform compared with DC. But, unfortunately, it can not be saved. Only thing which can save electricity has been a battery so far and it uses DC. Sometime there is a need of saving AC, then it has to be converted to DC, when the apparatus to do it is called `Rectifier.' Contrarily, it can be used as the commercial power after being converted to AC, when the apparatus is called "Inverter". This inverter which generates constant voltage & constant frequency like the commercial utility especially called "CVCF Inverter". |
| FES는 잉여의 전력을 회전체의 회전 관성 에너지의 형태로 저장한 다음 필요시 전력의 형태로 이용하는 시스템을 의미한다. 이 때 회전체에 저장되는 에너지는 회전 관성모멘트에 비례하고 회전 각속도의 제곱에 비례한다. 따라서 회전속도를 증가함에 따라 많은 에너지를 저장할 수 있다.배터리 전력저장시스템과 비교하여 단위 무게당 저장밀도가 높고 수명이 길며 유해가스를 발생하지 않는 장점이 있으므로 우주 항공시스템이나 전기자동차의 에너지저장장치로써 많이 연구되고 있다. 상용화 되지 않는 이유로는 베어링 마찰로 인한 손실증가 저밀도 고장력재료의 사용문제 등을 들 수 있다. 본 연구실의 실험장치는 베어링에 초전도 베어링을 사용하고 휠은 40,000 RPM-65Wh의 금속제 플라이휠을 사용하는 FES에 대해 실험하고 있다. 연구의 목표는 휠진동을 없애고 고효율로 제어하는 것이다. 따라서 운전속도 영역에서 모터 입력전류를 역기전력과 동상 또는 180도의 상차각을 갖는 정현파 전류로 제어하기위한 전력변환시스템개발에 목표를 두고 있다. |
| The privatization of utilities and the deregulation of the electrical energy market have introduced a new level of competition to the energy supply business. At the same time, the increasing use of electronics in everyday appliances and apparatus, plus a proliferation of highly sensitive end-user devices, are starting to draw the attention of consumers and energy suppliers alike to the issue of power quality. Solid-state transfer switches as an alternative to in-house uninterruptible power supplies, distribution static synchronous compensator for reducing flicker produced by arc furnaces, and dynamic voltage restorers that avoid production losses caused by voltage sags, are among the innovative solutions addressing the question of power quality. |
| The last line of defense against critical power loss has historically been the DC battery. Conscientious planned maintenance insured the availability of that battery. Today the last line of defense has shifted to yet another layer; intelligent battery validation systems. These surveillance devices coupled with quality software, a personal computer and a phone line, provide the predictive capability once enjoyed by manual surveillance techniques. The duty of these validation systems goes beyond reporting a failure but must include warning and alarm capability for impending battery system failure. The following illustrates such a system and highlights two examples of fault identification using battery validation equipment. For discussion purposes, we will concentrate on valve regulated or sealed type batteries since they offer the most critical maintenance issues to date |
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