Source: http://www.google.com/patents/US6756776?dq=5,884,272
Timestamp: 2013-12-10 10:48:30
Document Index: 108505279

Matched Legal Cases: ['arts 110', 'arts 110', 'arts 110', 'arts 110', 'arts 110', 'arts 110', 'arts 110', 'art 110', 'art 120', 'art 110', 'art 120', 'arts 110', 'art 110', 'art 120', 'art 110', 'art 120', 'arts 110', 'arts 110', 'arts 110', 'arts 110', 'art 224', 'art 204', 'arts 110']

Patent US6756776 - Method and device for installing and removing a current transformer on and ... - Google PatentsSearch Images Maps Play YouTube News Gmail Drive More »Advanced Patent Search | Sign inAdvanced Patent SearchPatentsA current transformer to be installed around a current-carrying conductor. The transformer has a split core with two parts, which can be opened to allow the transformer to be installed around or removed from the current-carrying conductor. A winding wound on the core is operatively connected to a switch...http://www.google.com/patents/US6756776?utm_source=gb-gplus-sharePatent US6756776 - Method and device for installing and removing a current transformer on and from a current-carrying power linePublication numberUS6756776 B2Publication typeGrantApplication numberUS 10/293,729Publication dateJun 29, 2004Filing dateNov 12, 2002Priority dateMay 28, 2002Fee statusPaidAlso published asEP1508146A2, US20030222747, WO2003100797A2, WO2003100797A3Publication number10293729, 293729, US 6756776 B2, US 6756776B2, US-B2-6756776, US6756776 B2, US6756776B2InventorsJoseph C. Perkinson, Scott D. BrownOriginal AssigneeAmperion, Inc.Export CitationBiBTeX, EndNote, RefManPatent Citations (11), Referenced by (10), Classifications (9), Legal Events (7) External Links: USPTO, USPTO Assignment, EspacenetMethod and device for installing and removing a current transformer on and from a current-carrying power lineUS 6756776 B2Abstract A current transformer to be installed around a current-carrying conductor. The transformer has a split core with two parts, which can be opened to allow the transformer to be installed around or removed from the current-carrying conductor. A winding wound on the core is operatively connected to a switch so that the winding can be shorted prior to opening the split core when the transformer is removed from the current-carrying conductor in order to reduce the magnetic force holding the split core parts together. The winding is shorted by the switch prior to closing the split core parts when the transformer is installed around the conductor in order to minimize the damage to the core due to the induced magnetic force thereon. A mechanical tool is used to open or close the split-core parts. The switch can be linked to the tool for shorting and opening the winding.
FIELD OF THE INVENTION The present invention relates to broadband communications using a power line as a transmission medium and, more particularly, a current transformer installed on a power line for obtaining power from the power line.
BACKGROUND OF THE INVENTION In power-line communications (PLC), utility power lines, especially the high-voltage (HV, 60 kVAC and up) and medium-voltage (MV, 4-35 kVAC) power lines, are used as a transmission medium. The MV power lines are generally used to power the primaries of distribution transformers feeding electric power to homes and businesses. It is advantageous to convey communication signals in radio frequencies (RF).
SUMMARY OF THE INVENTION It is a primary objective of the invention to reduce or eliminate the magnetic forces exerted on the split core parts of a current transformer when the current transformer is installed on an active, current-carrying power line and when the split core parts are opened for the removal of the current transformer from the power line. This objective can be achieved by shorting the multiple-turn winding on the split core parts during the installation and removal of the current transformer.
BEST MODE TO CARRY OUT THE INVENTION The current transformer 90, as shown in FIG. 2, has a secondary winding 140 of Ns turns around a split core 100. When the winding is shorted, a current with a magnitude substantially equal to Ip/Ns is developed in the shorted winding through normal transformer action, where Ip is the current in the conductor 5. This current creates an opposing magnetic field in the core, canceling the spatially nonlinear magnetic field generated near the surface of the active power line 5 due to the current flow in the conductor. The magnetic field created by the shorted winding greatly minimizes the forces on the core caused by this spatially nonlinear magnetic field. The shorting of the winding both protects the split core parts 110, 120 when they are closed to form a substantially closed-loop and allows the opening of the split core parts with minimal force.
As shown in FIG. 2, the two ends 142, 144 of the secondary winding 140 are connected to the shorting mechanism 192. The shorting mechanism 192 is operatively connected to the tool 194 that is used to cause the split core parts 110, 120 to close or to open. During the installation of the current transformer 90, the tool 194 causes the shorting mechanism 192 to close, thereby electrically connecting the ends 142, 144, and shorting the secondary winding 140 prior to closing the split core parts 110, 120 to form a substantially closed-loop around the conductor 5. After the installation is completed, the tool 194 can be disengaged from the core 100, keeping the split core parts 110, 120 in the �closed� position. At the same time, the tool 194 causes the shorting mechanism 194 to open, thereby allowing the secondary winding 140 to obtain the induced current through a transformer action. Preferably, the tool 194 is removed from the control assembly 190 and the housing 200 after the installation of the current transformer 90 is completed.
It should be noted that the winding 140, when it is not shorted, is also used for generating the current conveyed to the power supply electronics 180, as shown in FIG. 2. When the winding 140 is not shorted, the winding 140 is �opened�. The term �opened� simply means that the two ends 142, 144 are not electrically connected with each other. In this context, the winding 140 can be used for obtaining induced current when the winding is �opened�. However, it is also possible to use two separate windings 140, 150 around the split core 100, as shown in FIG. 3.
After the installation is completed, the tool 194 can be disengaged from the core 100, keeping the split core parts 110, 120 in the �closed� position. At the same time, the tool 194 causes the shorting mechanism 192 to open, thereby allowing the secondary winding 140 to obtain the induced current through a transformer action. Preferably, the tool 194 is removed from the control assembly 190 and the housing 200 after the installation of the current transformer 90 is completed. During the removal of the current transformer 90 from the power line 5, the tool 194 is applied to the control assembly 190 of the housing 200. The tool 194 causes the shorting mechanism 192 to close, thereby shorting the secondary winding 140. Subsequently, the tool 194 causes the split core parts 110, 120 to separate, allowing the current transformer 90 to be removed from the conductor 5.
As described in conjunction in FIG. 2, the force can be reduced or eliminated by shorting the ends 142, 144 of the secondary winding 140. After installation is completed and the split core parts 110, 120 is in the �closed� position, the shorting between the ends 142, 144 is removed, as shown in FIG. 4b. As shown, when the ends 142 and 144 are not shorted, the magnetic flux 160 in the split core 100 causes the winding 140 to induce a current, which is conveyed to the power supply electronics 180 (FIG. 2). It should be noted that the gaps 130 and 132 may not be completely closed when the split core 100 is in the �closed� position. An air gap 130′ could exist between the first end 112 of the first split core part 110 and the first end 122 of the second split core part 120. Likewise, an air gap 132′ could exist between the second end 114 of the first split core part 110 and the second end 124 of the second split core part 120. Preferably, the first end 142 and the second end 144 of the winding 140 are brought near the second ends 114 and 124 of the split core parts 110 and 120.
FIG. 5b is a schematic representation showing the split core 100 of the current transformer 90 of FIG. 3. Advantageously, the secondary winding 140 is wound on the first split core part 110, and the further secondary winding 150 is wound on the second split core part 120. When the first split core part 110 and the second split core part 120 are put together around the power line 5 to form a substantially closed loop transformer core, as shown in FIG. 5b, the spatially nonlinear magnetic field near the surface of the conductor 5 will exert a force on the first and second core parts 110 and 120. This force increases rapidly as the gaps 130 and 132 are reduced. As described in conjunction in FIG. 3, the force can be reduced or eliminated by shorting the ends 142, 144 of the secondary winding 140. In this embodiment, the winding ends 152 and 154 of the further secondary winding 150 are not affected by the opening or closing of the split core parts 110, 120. After installation is completed and the split core parts 110, 120 are in the �closed� position, the shorting between the ends 142, 144 is removed, as shown in FIG. 5b. In order to facilitate the opening and closing of the split core 100, the split core parts 110 and 120 are separately disposed in the first half 202 and the second half 204 of the housing 200. The housing 200 has a hinge 210 to keep the two halves 202 and 204 together so that the split core 100 can be operated in the open or closed position as shown in FIGS. 4a to 5 b. The housing 200 also has a latching mechanism to keep the two halves 202, 204 in a locked position when the split core 100 is operated in the closed position. The latching mechanism comprises a hook 222 on the first half 202 to be engaged with a counterpart 224 of the second part 204, for example. As shown, the hinge 210 is mechanically engaged with the control assembly 190 so as to allow the mechanical tool 194 to cause the split core parts 110, 120 to open or to close.
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