Patent Application
20190180920
This invention relates to the field of surge suppression and more particularly to a coil to protect a circuit from surges.
Sudden power surges caused by lightning or equipment malfunction often causes failure of circuits and equipment due to power surges. Equipment located in the vicinity of the cause of the surge is often destroyed, especially sensitive equipment such as cable repeaters. Many such equipment are often protected from surge entering on power inputs and on signal inputs/outputs, but not from surges entering on ground lines (earth ground).
Lightning often strikes trees, the ground, and other objects such as power lines. Lightning protection currently covers structural protection as well as electrical power protection on the power and data lines. Structural protection is commonly known as a “lightning rod” system that provides lightning strike current a safe, low resistance path to ground (earth ground). The “lightning rod” system is typically provided to prevent structural fires as the building structure itself is often a high resistance path to ground and large lightning currents cause heat and, therefore, fire.
Surge protection is currently provided to protect electrical power and data communication lines. Surge protection devices attempt to block or mitigate surges entering a building from the incoming metallic conductors (power and data).
For both lightning rod systems and for power surge protection devices to provide protection, the energy from a lightning strike must hit either the structure or the incoming metallic lines.
There is another path for surge damage that has not been considered. Surges from nearby lightning strikes, for example, enter through the earth ground. In the literature any voltage appearing in the earth is known as “ground potential” and if there is a sudden change in voltage of the ground, it is called a “ground potential rise.” There have been many studies of ground potential rise and it is known that ground potential rise can cause surge damage similar to a direct lightning strike.
Inductive coils have been used in electrical grounding systems in the past. In particular a Peterson grounding coil has been used to ground electrical utility power transformer secondary windings. The Peterson coil was introduced and studied extensively in the 1920's and 1930's. Because the Peterson coil affects system voltage balance and fault currents, use was discontinued in electric utility practice.
One of the issues with any inductive coil is the effects the coil can have on an electrical system due to the coil's inductance at the 60 cycle power line frequency.
What is needed is a grounding protection coil that exhibits almost zero inductance at the 60 cycle power system frequency and, therefore, has little effect on the electric power system.
In one embodiment, a ground protection coil for insertion into a circuit is disclosed including an inner coil section consisting of a wire wound in a first direction for a first number of turns and an outer coil section consisting of the wire wound in a second direction for a second number of turns. The second direction is at an angle of approximately 90 degrees from the first direction.
In another embodiment, a method of protecting an electrical device from ground surges is disclosed including installing ends of a temporary electrical jumper on a ground path that provides a ground potential to the electrical device at a location of installation of a ground protection coil then cutting the ground path between the ends of a temporary electrical jumper. Next, the ground protection coil is electrically connected into the ground path where the ground path was cut and then the temporary electrical jumper is removed. The ground protection coil includes an inner coil section consisting of a wire wound in a first direction for a first number of turns and an outer coil section consisting of the wire wound in a second direction for a second number of turns, the second direction being rotated 90 degrees from the first direction.
In another embodiment, a ground protection coil is disclosed including a first winding being a first serpentine printed circuit path running in a first direction for a first number of turns and a second winding consisting of a second serpentine printed circuit path running in a second direction for a second number of turns. The second direction is at an angle of approximately 90 degrees from the first direction.
The invention can be best understood by those having ordinary skill in the art by reference to the following detailed description when considered in conjunction with the accompanying drawings in which:
Reference will now be made in detail to the presently preferred embodiments of the invention, examples of which are illustrated in the accompanying drawings. Throughout the following detailed description, the same reference numerals refer to the same elements in all figures.
Any coiled wire of sufficient length will have inductance. The inductance will vary with the number of turns of wire in the coil. Current flowing through a coil of wire will create an electrical field. Each turn of wire has a field that affects nearby turns of wire. These fields slow the flow of current through the coiled wire. When a coil is wound over an iron core, the field magnetizes the core and the inductance is higher. Losses in the coil result in heating of the coil and core. Therefore, a typical iron core inductor must be made very large in order to carry a high load current without overheating.
Without the iron core, only the magnetic fields resist current flow and those fields are not nearly as strong as magnetic fields in a coil having an iron core. When used on alternating current power systems, coreless coils can carry much more current without overheating than similar size coils having iron cores.
Unfortunately due to the small fields, prior coreless coils are not useful for surge protection as they do not reduce surge levels significantly.
U.S. Pat. No. 7,085,115 for “non-ferrous surge balancing coil” describes a pair of coils placed such that the windings were located 90 degrees to each other. This surge balancing coil was designed to be used in electrical power and data systems where each opposed winding of the coil is independent and connected to a different power conductor.
The ground protection coil 10 (see
This ground protection coil 10 provides resistance to sudden changes of ground current attempting to enter the power system through an electrical grounding path, while providing low resistance to lower frequency changes (e.g. DC to 60 Hz).
In some applications, two or more ground protection coils 10 are inserted into power lines to reduce the passage of transient surge spikes.
Referring to
In some embodiments the inner coil section 16 and the outer coil section 20 are made from a single, continuous wire. In some embodiments the inner coil section 16 is wrapped in one direction, then the inner coil section 16 is rotated 90 degrees and the outer coil section 20 is wrapped over the inner coil section 16. The wire size/gauge and number of turns is dependent upon the amount of current carrying capacity needed. For example, for a 15 amp load, at least a 14 gauge wire size is required.
The coil is typically manufactured by winding wire on a coil form. Typically 3 turns of wire or more are wound, though it has been shown as few as 3 turns work although somewhat weakly and that more than 20 turns has diminishing returns due to the cost of wire (e.g. copper wire).
In some embodiments, the inner coil section 16 has the same number of turns as the outer coil section 20. For example, if the inner coil section 16 has 20 turns, then the outer coil section 20 will also have 20 turns. In some embodiments, the inner coil section 16 has a different number of turns as the outer coil section 20. For example, if the inner coil section 16 has 20 turns, then the outer coil section 20 has some number of turns other than 20.
Referring to
In one embodiment, multiple printed circuit board(s) 110 with are stacked with serpentine circuit traces 116 on each printed circuit board 110 running at 90 degrees with respect to serpentine circuit traces 116 on the adjacent printed circuit board 110. One printed circuit board 110 has an input connector and another has an output connector.
In another embodiment, printed circuit board(s) 110 are made with serpentine circuit traces 116 on one side of the printed circuit board 110 running at 90 degrees with respect to serpentine circuit traces 116 on the opposing side of the printed circuit board 110. One side of the printed circuit board 110 has an input connector at a first end of the serpentine circuit trace 116 on that side, the other side of the printed circuit board 110 has an output connector a first end of the serpentine circuit trace 116 on that side, and there is a through-board connection (via) between the second end of both serpentine circuit traces 116.
In another embodiment, printed circuit board(s) 110 are made with serpentine circuit traces 116 on multiple layers of the printed circuit board 110 running at 90 degrees with respect to serpentine circuit traces 116 on other layers of the printed circuit board 110. One layer of the printed circuit board 110 has an input connector at a first end of the serpentine circuit trace 116 on that layer, another layer of the printed circuit board 110 has an output connector a first end of the serpentine circuit trace 116 on that layer, and there is a through-layer connections (via) between the second end of both serpentine circuit traces 116. Multiple are anticipated, but a minimum of 4 layers is preferred. In the example shown in
Referring to
Referring to
As shown in
It should be noted that it is anticipated that the ground protection coil 10 will be used to protect many devices other than the cable television distribution amplifier 210 that is shown as an example.
Equivalent elements can be substituted for the ones set forth above such that they perform in substantially the same manner in substantially the same way for achieving substantially the same result.
It is believed that the system and method as described and many of its attendant advantages will be understood by the foregoing description. It is also believed that it will be apparent that various changes may be made in the form, construction and arrangement of the components thereof without departing from the scope and spirit of the invention or without sacrificing all of its material advantages. The form herein before described being merely exemplary and explanatory embodiment thereof. It is the intention of the following claims to encompass and include such changes.
