Wave transmission lines and networks – Transmission line inductive or radiation interference...
Reexamination Certificate
2001-08-27
2003-11-04
Ham, Seungsook (Department: 2817)
Wave transmission lines and networks
Transmission line inductive or radiation interference...
C333S181000
Reexamination Certificate
active
06642806
ABSTRACT:
FIELD OF THE INVENTION
The invention relates to frequency suppression devices and more particularly to magnetic frequency suppression devices used in medium and high voltage power systems and data communication systems.
BACKGROUND OF THE INVENTION
Very fast transients (VFT's) and high frequency (HF) harmonics are becoming ubiquitous in electrical power transmission and distribution systems. Transients are an electrical phenomena that appear as rapid voltage fluctuations in an electrical system. Therefore, an electrical power system not only carries a productive power signal, for example, operating at 60 Hz, but also inadvertently carries transients and harmonics operating at frequencies other than 60 Hz. As such, VFT's and HF harmonics compromise power quality and often disrupt industrial processes causing equipment damage and expensive downtime. Essentially, power quality is a performance measure for electrical power. Power quality has become essential in today's electronics-based world where electrical equipment has become increasingly sensitive to variations in power. Therefore, power quality must be kept high in order to meet the electrical demands of such equipment.
Power quality is kept high by decreasing the occurrence of VFT's and HF harmonics in medium and high voltage electrical systems. Traditionally, inductor-capacitor (LC) filters have been used to decrease the occurrence of transients and harmonics by electrically filtering such transients and harmonics from the electrical system. LC filters typically include an inductor and capacitor connected in series or in parallel and are electrically coupled to the electrical system. There are, however, several disadvantages to using LC filters. First, because the LC filter is electrically coupled to the system, installation costs are relatively high for implementing the intrusive filter into the system and maintenance costs are incurred in periodically maintaining the filter. Second, the large size of the filters often hinder the installation process and therefore also raise costs.
Toroids provide another way of decreasing VFT's and HF harmonics. Unlike LC filters, toroids non-intrusively filter transients and harmonics from an electrical system using electromagnetism. Generally, toroids are donut shaped, i.e. with a circular shape and a circular aperture. The electrical conductor extends through the toroid's aperture. Toroids are made from magnetic materials having a relative permeability and resistivity, that determine the toroid's effectiveness in suppressing VFT's and HF harmonics. That is, as electrical power passes through the conductor extending through the center of the toroid, the toroid's magnetic properties suppress the VFT's and HF harmonics carried by the conductor. The toroid may be constructed to selectively filter certain frequencies from the conductor. While high frequency (HF) toroids have been used to suppress transients in low voltage applications, such as personal computer monitor cables, toroids have not been not used in medium or high voltage applications.
For the foregoing reasons, there is a need for a simple, low cost and easily installable high frequency suppression device that can maximize power quality in medium and high voltage industrial distribution systems without introducing significant losses to the desired frequency.
SUMMARY OF THE INVENTION
The invention provides a device that selectively and magnetically filters HF transients from an industrial distribution system or an electrical power system without introducing any losses or compromising the power signals operating at about 50-60 hertz. The invention is a simple, low cost, and easily installable high frequency suppression device that improves power quality in industrial distribution systems.
The toroid filters medium voltage and high voltage conductors. The toroid includes an interior surface, an exterior surface and a material located between the interior surface and the exterior surface. Such material magnetically filters the medium voltage and/or high voltage conductors by passing signals in a first frequency range and impeding signals in a second frequency range.
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Hitachi Metals, Ltd., Mn-Zn Ferrite material, 2001.
Glinkowski Mietek T.
Trivette Marty L.
ABB Inc.
Ham Seungsook
Woodcock & Washburn LLP
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