Patent Grant
11302506
Embodiments of the invention described herein pertain to the field of high voltage electrical fuses. More particularly, but not by way of limitation, one or more embodiments of the invention enable a high voltage fuse adapter system and method.
An electrical fuse is a safety device that operates to provide overcurrent protection of an electrical circuit. The fuse's essential component is a metal wire or strip that melts when too much current flows through the fuse, thereby stopping or interrupting the current and preventing damage to other valuable equipment in the circuit.
Fuses above 600 Volts are considered high voltage, and are conventionally used in industrial applications that require electricity in large quantities, such as refineries, pulp mills and paper mills. In North America, high voltage fuses are typically incorporated into disconnect switches.
In North America, the Institute of Electrical and Electronic Engineers Inc. (IEEE) and the National Electrical Manufacturers Association (NEMA) set standards for fuses. E-Rated fuses have defined current response times specified by ANSI C37.46. E-Rated fuses 100 Amps and below must melt in 300 seconds at a Root Mean Square (RMS) current within the range of 200% to 240% of the continuous current rating. E-Rated fuses above 100 Amps must melt in 600 seconds at a RMS current within the range of 240% to 264% of the continuous current rating of the fuse. E-Rated fuses are used to protect feeder circuits, power transformers and potential transformers.
Many high voltage fuse disconnect switches currently require 15,000 Volt fuses. Previously in North America, a single E-rated fuse made of filament wound fiberglass had been used in such circumstances, mounted in an Underwriters Laboratory (UL) style single-fuse mounting. However, due to heat dissipation problems, use of single E-rated fuses have been discontinued. This leaves legacy disconnect switches with UL style single-barrel mountings, but no fuses that are able to handle the current carrying specifications and also fit within the UL style single-barrel mounting.
Presently, at current levels exceeding 100 Amps, two E-rated 15,000 Volt fuses per phase, mechanically attached together, are required to meet the current carrying specifications due to the low melting temperature of the filament wound fiberglass fuse body. Unfortunately, legacy equipment would need to be retrofit to replace the single-fuse UL mounting block with a double-fuse UL mounting, since double fuse clips do not fit within existing mounting blocks designed for a single fuse. Retrofitting the mounting blocks can cost tens of thousands of dollars due to system downtime required during the retrofit, and the need to hire an electrician. In addition, E-rated high voltage fuses are expensive, typically costing in the range of $2,000 USD per fuse as of this writing, and two such fuses are now required instead of one.
International Electrotechnical Commission (IEC) rated fuses are standardized fuses used in Europe and locations outside of North America. IEC fuses are made of ceramic with a much higher melting temperature, as opposed to filament wound fiberglass, and are therefore able to run more current than North American E-rated fuses. A single IEC standard fuse costs about half of a single E-rated fuse, and would be capable of handling the necessary 200 Amps at 15,000 Volts required for North American E-rated fuses. Unfortunately, the IEC fuses are not the right shape or size to fit into a UL style single-fuse mounting used in North American circuitry. A standardized IEC fuse of the prior art is shown in
For new applications, the ability to use a single fuse, instead of a double fuse arrangement would save cost, materials and space.
As is apparent from the above, North American fuses for high voltage fuse disconnect switches require two, wound filament-style fuses per phase in a UL type fuse mounting. These fuses are expensive at $2,000 each, and the double-barrel fuse mounting does not fit into legacy equipment designed for a single fuse per phase. It would be desirable and less expensive if a single IEC fuse could be used in a UL style singe-fuse mounting. Doing so would save material, save space and achieve significant cost savings. Therefore, there is a need for a high voltage fuse adapter system and method that would allow a single IEC fuse to be used in a North American fuse clip.
One or more embodiments of the invention enable a high voltage fuse adapter system and method.
A high voltage fuse adapter system and method is described. An illustrative embodiment of a high voltage fuse adapter system includes an indicator-end adapter configured to circumferentially enclose an indicator-end terminal of a high voltage International Electrotechnical Commission (IEC)-rated fuse, including a hollow portion having an inner diameter that surrounds the indicator-end terminal, the hollow portion including at least one axially extending slot compressible around the indicator-end terminal, and an indicator portion, a piston and needle enclosed within the indicator portion, the piston and needle coupled to a striker of the high voltage IEC-rated fuse such that upon extension of the striker, the piston at least partially actuates the needle outside of the indicator-end adapter, a non-indicator-end adapter configured to circumferentially enclose a non-indicator-end terminal of the high voltage fuse, and a pair of end caps enclosing the indicator-end adapter and the non-indicator end adapter to form an adapted fuse, wherein the adapted fuse is configured to fit in an Underwriters Laboratory (UL)-style fuse mounting. In some embodiments, the hollow portion of the indicator-end adapter covers the indicator-end terminal. In certain embodiments, a first end cap of the pair of end caps encloses the indicator-end adapter, the first end cap having an opening, and wherein the needle extends through the opening when actuated by the piston. In some embodiments, the hollow portion mates with the indicator-end terminal, and the indicator portion extends on an outward side of the indicator-end adapter. In certain embodiments, the at least one axially extending slot includes two axially extending slots arranged 180 degrees apart. In some embodiments, the indicator-end adapter and the non-indicator-end adapter are silver plated. In certain embodiments, the piston is threadedly connected to the needle, and the piston extends circumferentially around an outer diameter of the striker. In some embodiments, the at least one axially extending slot is compressible by at least one radially-oriented screw extending through an aperture in the indicator-end adapter. In certain embodiments, the high voltage IEC-rated fuse is an IEC standardized Ferrule-style fuse of 15.5 kV and one of 125, 150, 175 or 200 Amperes. In some embodiments, the UL-style fuse mounting is a CLE/CLS UL style fuse clip mounting. In certain embodiments, the non-indicator end adapter further includes a second at least one axially extending slot compressible around the non-indicator-end terminal.
An illustrative embodiment of a method of employing a single International Electrotechnical Commission (IEC) fuse in an Underwriters Laboratory (UL)-style fuse mounting, including enclosing an indicator-end of the single IEC fuse inside a first adapter piece that lengthens and widens the indicator-end, coupling a piston and needle to a striker of the single IEC fuse such that the needle is visible outside the adapter when the single IEC fuse breaks, and enclosing the non-indicator-end of the single IEC fuse inside a second adapter piece, capping the first and second adapter pieces with end caps, and mounting the single IEC fuse with adapters and end caps into the UL-style mounting. In some embodiments, the method further includes compressing the first adapter piece around the indicator end to mate a hollow portion of the adapter piece to the indicator end. In certain embodiments, the striker of the single IEC fuse actuates the needle at least partially out of the adapter when the single IEC fuse breaks. In some embodiments, the method further includes silver-plating the first and second adapter piece. In certain embodiments, the method further includes taking a resistance reading subsequent to enclosing the indicator-end and the non-indicator end of the single IEC fuse inside the first adapter piece and the second adapter piece. In some embodiments, the method further including employing the mounted single IEC fuse in a phase of a North American style disconnect switch.
An illustrative embodiment of a system for utilizing an International Electrotechnical Commission (IEC)-rated fuse in North American style equipment includes a pair of adapter pieces that compressibly mate around respective terminals of the IEC-rated fuse such that the IEC-rated fuse is configured to fit within a pair of Underwriters Laboratory (UL) standard fuse caps and an indicator is visible outside at least one adapter piece of the pair of adapter pieces and its corresponding UL standard fuse cap upon overload of the IEC rated fuse.
In further embodiments, features from specific embodiments may be combined with features from other embodiments. For example, features from one embodiment may be combined with features from any of the other embodiments. In further embodiments, additional features may be added to the specific embodiments described herein.
Advantages of the present invention may become apparent to those skilled in the art with the benefit of the following detailed description and upon reference to the accompanying drawings in which:
While the invention is susceptible to various modifications and alternative forms, specific embodiments thereof are shown by way of example in the drawings and may herein be described in detail. The drawings may not be to scale. It should be understood, however, that the embodiments described herein and shown in the drawings are not intended to limit the invention to the particular form disclosed, but on the contrary, the intention is to cover all modifications, equivalents and alternatives falling within the scope of the present invention as defined by the appended claims.
A high voltage fuse adapter system and method will now be described. In the following exemplary description, numerous specific details are set forth in order to provide a more thorough understanding of embodiments of the invention. It will be apparent, however, to an artisan of ordinary skill that the present invention may be practiced without incorporating all aspects of the specific details described herein. In other instances, specific features, quantities, or measurements well known to those of ordinary skill in the art have not been described in detail so as not to obscure the invention. Readers should note that although examples of the invention are set forth herein, the claims, and the full scope of any equivalents, are what define the metes and bounds of the invention.
As used in this specification and the appended claims, the singular forms “a”, “an” and “the” include plural referents unless the context clearly dictates otherwise. Thus, for example, reference to a slot includes one or more slots.
As used in this specification and the appended claims, “high voltage” means 600 Volts or above.
As used in this specification and the appended claims, “coupled” refers to either a direct connection or an indirect connection (e.g., at least one intervening connection) between one or more objects or components. The phrase “directly attached” means a direct connection between objects or components.
In the art, a 15,000 Volt fuse is sometimes referred to as a 15.5 kV fuse. Both such terms are used interchangeably to refer to a fuse able to withstand up to 15.5 kV.
One or more embodiments of the invention provide a high voltage fuse adapter. While for ease of description and so as not to obscure the invention, illustrative embodiments are described in terms of a 15,000 Volt fuse, nothing herein is intended to limit the invention to that embodiment. The invention may be applied equally to fuses with other voltages and currents.
Since the discontinuation of single E-rated fuses, resellers and end-users of high voltage fuses have recognized a need to replace the double-barrel design required for 15,000 Volt E-rated fuses in North America with a less-expensive, lower footprint alternative that continues to operate reliably and does not interfere with the functioning of the overload indicator. Illustrative embodiments may solve this need by, and may include, a high voltage fuse adapter. The adapter of illustrative embodiments may modify a single IEC fuse to fit into a UL style single-barrel mounting in high voltage embodiments. A piston and needle of illustrative embodiments coupled to the striker of the IEC fuse may provide a visible indication of overload despite the striker being covered inside the adapter of illustrative embodiments. The adapter allows a single fuse per phase to be employed, rather than a set of two North American style fuses. Using a single fuse per phase amounts to considerable cost savings since it obviates the need to replace mounting blocks in legacy equipment. A single IEC fuse also has a smaller footprint than the double barrel design, thus saving space and material in newbuild applications. In addition, as of the date of this writing, a single high voltage fuse costs approximately $2,000 USD, and an IEC fuse costs about half of one E-rated fuse.
Illustrative embodiments may include a pair of adapter pieces that attach to the indicator and non-indicator side of an IEC fuse. Each adapter piece may be cylindrical in shape with a hollow portion, slotted and screwed, snapped and/or fit tightly around the terminal ends of the fuse. The adapter pieces may increase the length and width of the terminal ends of the IEC fuse such that the IEC fuse can accommodate a three-inch diameter fuse cap, which is the UL standard that matches fuse clip dimensions of the single barrel UL design used in North American applications. The fuse caps, which may also be called end caps, may be placed over each adapter prior to mounting. Thus, making illustrative embodiments “plug and play”. The indicator-side adapter piece may include an internal piston and needle that aligns with the striker of the IEC fuse. Should the fuse become overloaded and the striker be triggered, the striker may hit, push and/or move the piston, and the needle may extend out of the adapter body as a visible indicator of overload. The adapter pieces of illustrative embodiments may be silver plated after machining and prior to assembly to ensure good electrical conductivity. A resistance reading of the fuse may be conducted prior to assembly and after assembly to ensure the characteristic of the final product has not been changed and provide the user with confidence that the adapter is functioning properly.
Indicator-end adapter 300 may include hollow portion 320. Hollow portion 320 may provide a female connection to mate snugly with indicator-end terminal 605 and/or cover indicator-end terminal 605. Indicator portion 325 of indicator-end adapter 300 may include an inner diameter that forms piston cavity 335 and needle-shaped channel 340. Axially extending passages 330 may accommodate fasteners 615 (shown in
Indicator-end adapter 300 and non-indicator-end adapter 400 may be 360 brass and silver plated to ensure good electrical conductivity. Silver plating may be 0.0001 inches thick and may be applied after machining and prior to attachment of adapters 300, 400 onto fuse 500. In one non-limiting example, to form a 15.5 kV E-rated fuse size D from standardized IEC fuse 500, adapters 300, 400 may each be about 3.19 inches in length and about 2.872 inches in outer diameter. Passages 330 may be about 0.750 inches deep.
In illustrative embodiments, piston 700 may be aluminum and needle 705 may be 300 series stainless steel in one non-limiting embodiment. In exemplary embodiments, needle 705 may be about 1.670 inches in length, and needle 705 and piston 700 assembled length may be about 1.8 inches. The length of needle 705 and piston 700 should be such that needle 705 does not extend and/or is not visible outside fuse cap 610 if fuse 500 is not broken, and alternatively visible outside fuse cap 610 if fuse 500 overloads. In some embodiments, needle 705 may be attached to piston 700 with a threaded connection.
Upon overload, striker 625 may extend outward from fuse 500 in the direction of arrow 710, as shown in
Illustrative embodiments may enable the utilization of IEC style fuses in North American equipment. Illustrative embodiments may convert the physical dimensions of an IEC fuse design without inhibiting the functioning of the fuse or interfering with the visible indication of overload of the fuse. Illustrative embodiments may conserve resources by replacing a single fuse where two fuses would otherwise be required. Those of skill the art may appreciate that the adapter system of illustrative embodiments may be employed with other voltages and currents other than 15,000 Volts.
A high voltage fuse adapter system and method has been described. Further modifications and alternative embodiments of various aspects of the invention may be apparent to those skilled in the art in view of this description. Accordingly, this description is to be construed as illustrative only and is for the purpose of teaching those skilled in the art the general manner of carrying out the invention. It is to be understood that the forms of the invention shown and described herein are to be taken as the presently preferred embodiments. Elements and materials may be substituted for those illustrated and described herein, parts and processes may be reversed, and certain features of the invention may be utilized independently, all as would be apparent to one skilled in the art after having the benefit of this description of the invention. Changes may be made in the elements described herein without departing from the scope and range of equivalents as described in the following claims. In addition, it is to be understood that features described herein independently may, in certain embodiments, be combined.
This application claims the benefit of U.S. Provisional Application No. 63/012,558 to Drotar et al., filed Apr. 20, 2020 and entitled “HIGH VOLTAGE FUSE ADAPTER SYSTEM AND METHOD,” which is hereby incorporated by reference in its entirety.
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| Number | Date | Country | |
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| 63012558 | Apr 2020 | US |
