Patent Application
20100321003
This invention relates to adapters to meters that, among other capabilities, measure common resources, especially electrical energy.
There are meters that, among other capabilities, measure common resources (herein, meant to include consumption of commodities like electrical energy, water, and gas). Standard meters, as understood in the electrical utilities business in the United States, Canada and herein, are those that conform to ANSI standard C12.10. This standard and others (and counterparts in jurisdictions around the world) dictate a host of restrictions, including the physical envelope or form factor, the dimensions, locations and materials for power pins, the permissible types of electrical connections with the meter, and similar items, for a one or multi-phase electricity measuring meter. These standards try to maximize safety and inter-compatibility of meters from different manufacturers. This ANSI standard in effect, prohibits or strongly discourages any electrical connection between the meter and anything else except for the power pins and grounds.
To make a standard meter a useful part of a network, it is desirable to provide it with extra functionality and ideally, to so provide by means of an easily releasably attachable adapter, and in particular herein, a collar with superior (mechanical and electrical) interconnection and safety (e.g. fuse) capabilities. It is also desirable to minimize the overall physical “footprint” of the collar (while still conforming to safety standards) and yet be large enough to house the desired extra functionality. The present invention addresses those objectives. And although the embodiment of the present invention described below is with reference to a standard electrical meter, certain aspects of it are not thereby restricted thereto, and are applicable to meters that measure other resources (such as water and gas).
The current art has complexities and associated disadvantages. Typical is U.S. Pat. No. 5,762,522 that shows a fuse and mechanical contact clip which is complex (in requiring a plurality of parts, including rivets and several angled portions). The present invention addresses the complexities with a simpler approach.
For a metered premise (house or commercial/industrial venue), the branch circuits and associated safety management (e.g. fuses) are conventionally on the load side of the meter (i.e. the part of the meter that is associated with the load side terminals, and which the utility uses to measure consumption or other attribute of electricity by the load side circuit, and is governed by a utilities regulatory regime, as distinct from a safety standards regime). Thus, for example, fuse/circuit breaker panels (and associated branch circuits to various in-house loads) are found typically inside the house and are (at least) electrically downstream from the line side of the meter, i.e. they tap the load side terminals.
For evolving applications and needs (e.g. for “smart grid” meters, as exemplified in U.S. Pat. No. 7,019,666), there are advantages to create and supply “branch circuits” on the line side of the meter (i.e. the part of the meter that is associated with the line side terminals, and that is not measured by the utility for consumption of electricity, and is governed by a safety and related regulatory regime (like the National Electric Code or equivalent), as distinct from a utilities regulatory regime).
Previous attempts (for examples, U.S. Pat. Nos. 7,182,632 and 7,040,920) promised added functionality to the meter collar using the line side of the meter without address the consequent issues. For such extra functionality, the present invention addresses such issues, including those related to safety.
Although counter to the conventional approach of the average skilled person in transformer design, the present invention suggests to such person, to sacrifice some transformer efficiency (e.g. by inherently limiting the current) to meet space and safety constraints. Although some inefficiency results (for example, perhaps greater total I2R losses and core losses of the transformer), the “hot spot” or “hotter spots” can be reduced in maximum severity. The present invention also teaches to approximately equalize the I2R losses of the primary and secondary windings, or perhaps set a simple ratio relationship between them, and discloses the method by which to achieve approximate equality.
A better understanding of the present invention can be obtained when the following detailed description of the preferred embodiment is considered in conjunction with the following drawings, in which:
a), 13(b) and 13(c) show views of the components that are assembled into the extender;
a) shows a back perspective view of the interior of bottom access cover of the extender;
b) shows a front perspective view of the exterior of bottom access cover of the extender;
a) and 17(b) show perspective views of a transformer assembly of windings, bobbins and bobbin holder; and
c) shows an alternative transformer configuration to that of
As shown in
The mechanical interposition is achieved partially by conventional mechanisms (including fastening mechanisms and mating of respective perimeter profiles and mounting surfaces) and partially by improved mechanisms (described below). The electrical agency between meter 10 and meter socket 20 is provided by the use of four identical power pins 109, snugly fitted into collar mounting slots 121 and 122 (for the meter load line terminals) and into collar mounting slots 123 and 124 (for the meter line side terminals).
As shown in
In
As shown in
Ring spring 112, as shown in
Once tabs 1131 and 1132 are inserted in their respective associated apertures 1141 and 1142, they remain there, and ring spring 112 then biases opposed fingers 1091 and 1092 toward each other to resist separation in the “installed state” of meter 10. (i.e. when meter 10, and in particular its meter blades 11, 12, 13 and 14, are inserted into collar 105, and in particular, its power pins 109).
In “installed state”, jaw 110 of each power pin 109 (and in particular, fingers 1091 and 1092 thereof) releasably or removably receives therebetween a meter power blade (one of blades 11, 12 associated with meter line side terminals, or one of blades 13 and 14 associated with meter load side terminals); and blade terminal 111 of each power pin 109 is inserted into the corresponding socket of meter socket 20; thereby creating electrical agency between meter 10 and meter socket 20. In “installed state”, ring spring 112 force fingers 1091 and 1092 towards each other to enhance the sandwich grip thereby on meter power blades 11, 12, 13 or 14.
When meter 10 is not inserted into collar 105 (the “uninstalled state”), although ring spring 112 contacts fingers 1091 and 1092 at tabs 1131 in apertures 1141 and 1142, they apply no or very little force on fingers 1091 and 1092.
Conventional jaws are completely planar or have a hard angle that becomes the edge of contact with the installed meter blade. In contrast, power pin jaw finger 1091 is smoothly curved. The curve is modeled on the behaviour of three locations thereof, 1091a, 1091b and 1091c, in response to the installation of meter 10 into collar 105 (i.e. the insertion of a meter blade into power pin jaw 110), as explained below.
As seen in
First, the vertical displacement of “spring location” 1091a (employing a rigid beam model of jaw finger 1091), is approximated by:
Δa=(F·(Lac−x)/Lac)/Ka
where x=0 corresponds to spring location 1091a; Ka=approximated effect of the (inward) remainder of jaw at 1091a represented by a spring stiffness thereat; and Lac=horizontal distance between “spring location” 1091a and “jaw crest” 1091c.
Next, the vertical displacement of “jaw crest” position 1091c is due to the force felt at that position (assuming a rigid beam model), and is approximated as:
Δc=(F·x/Lac)/Kc
where Kc=approximated effect of the (outward) remainder of jaw at 1091c represented by a spring stiffness thereat; E=modulus of elasticity of copper; and I=the area moment of the cross-section of the meter blade profile=w·t3/12, where w=width of meter blade and t=half of the thickness of the meter blade (as applicable to interaction with jaw finger 1091).
Due to these above factors, the total vertical displacement of “leading edge” position 1091b (employing a rigid beam model of jaw finger 1091), is approximated by:
Δb(rigid)=Δc·(x/Lac)+Δa·(L−x)/Lac
Next, employing an elastic beam model of jaw finger 1091 with fixed ends at 1091a and 1091c, the vertical displacement of “leading edge” 1091b is approximated as;
Δb(elastic)=(F·x2·(Lac−x)2)/(3·E·I·Lac)
Thus the total vertical displacement of “leading edge” 1091b at position (x) is
Δ(x)=Δb(rigid)+Δb(elastic).
Jaw finger 1091 is advantageously formed to have a curve in accordance with preceding formula. The preceding explanation applies identically to jaw finger 1092 and meter blades identical to meter blade 11.
An example of the model formula is show in
In uninstalled state, the separation between fingers 1091 and 1092 is about 57 mils; and in installed state, the separation is in the order of 100 mils.
Examples of details of the practising of the present invention, include the following. Ring spring 112 metal is 302 or 301 stainless steel with minimum yield strength of 150000 psi. Fuse 410 is a common, high interrupt amperage capability. Power pin 109 is made of hard copper with tin plating. Fuse holder 400 is made of phosphor bronze and can be made integrally by suitable bending of a single sheet of such metal. Collar 105 may be formed of polycarbonate plastic or any other material having similar physical properties, such as those related to robustness, rigidity, temperature sensitivity, and electrical insulation. Ring spring 112 can be made of a single metal sheet of appropriate tensile and other properties, that can be cut and bent cylindrically to create opposed tabs 1131 and 1132 that are alignably insertable into corresponding apertures 1141 and 1142 of fingers 1091 and 1092 respectively.
Fingers 1091 and 1092 of power pin 109 are identical and are orientated in opposition as shown in the drawings. They may be made of a single sheet bent at the point corresponding to the jaw terminal 110 (to obviate the need of a fastener thereto). If fingers 1091 and 1092 are made discretely, they may be conventionally fastened rigidly (e.g. rivets).
Although a cylindrical ring spring 112 is disclosed, other generally C-shaped shapes are possible, each with respective advantages and disadvantages. For example, a V-shaped spring is possible.
The branch circuit may be within (entirely or partially) within collar 105 or connect to loads (i.e. devices) applicable in the factory, house or other venues. Examples of branch loads include those related to auxiliary power supply, data modem (for examples, for Internet Protocol based communications and Wide Area Networks and Local Area Networks (both wireless and wired embodiments), and external VoIP supervisory circuitry. Some branch loads may be manifested in compact form and be insertable (entirely or partially) within collar 105 and directly contact branch fuse terminal 404 (as shown). An example is the “adapter assembly” of U.S. Pat. No. 7,040,920, which may, for example, house an auxiliary backup battery pack. But also, some branch loads may be physically remote from collar 105 but electrically connected to branch fuse terminals 404.
Although branch fuse holder 400 has been shown and explained for a line side power pin, it can be used for a load line power pin, with fuse 410 appropriate for the applicable branch circuit load.
Also, although two branch fuse holders 400 have been shown, one will suffice for some applications and this invention does not require two. However, depending on the particular application and risk management concerns, the advantages of redundancy of two branch fuses are justified—in addition to redundancy, fuse 410 for both line side terminals (as shown in
Although fuse holder 400 has been shown with conductive friction grips 401 to attach (electrically and mechanically) holder 400 to power pin 109, other fuse holders and conductive attachments are contemplated as physically residing within collar 105, in particular, and electrically on the load line side of meter 10, more generally.
Although the embodiment described relates to a standard electrical power meter conforming to Form 2S, this invention is applicable to other standard meters (such as Form 3S and 4S) where only obvious modifications are necessary to accommodate a different socket/power pin arrangement. Also, it is understood by those in the art that this ANSI standard is unlikely to be modified substantially in the future but if it is modified slightly, it will be readily apparent to those in the art that this invention may be easily adjusted accordingly to fit the amended envelope or form factor. It would be a matter of simple design to accommodate different form factors (i.e. geometry of and number of sockets) and different types of meters (e.g. single-phase or multi-phase).
Interface extender 200 extends the space (beyond that provided by collar 105) for housing more interface functionality. Interface functionality assists in the transfer and/or conversion of information and/or of power. An example of the former is metered data in one communications protocol (such as AINSI C12.18 and C12.19) that is converted into another protocol (such as IP protocol for Web-based applications). An example of the latter is the power transformer (for stepping down the line voltage for use in or around the home).
The interface functionality is implemented by conventional methods in the software, hardware, chemical, and mechanical arts. Examples of interface functionality include transformers, voltage regulators, temperature sensors, fibre-to-copper communication interfaces, communications protocol converters, data modem for Internet Protocol-based communications and Wide Area Networks and Local Area Networks, whether wired or wireless).
As seen in
As seen in
In the example shown in
Electronics 313 may include power regulators, voltage rectifiers, control circuitry for the fan, heat sinks, temperature sensors, wireless communications transceivers, data modems, and other application-specific circuitry, whose physical footprint is compact enough to be housed in extender 200.
Like main housing body 201, arcuate portion 204 can also house interface functionality (e.g. wireless transceivers). Optionally, arcuate portion 204 has a port or knockout 205 (and related box connectors, couplings and the like) for power and communications cables and the like, for connection to remote entities (for example, a UPS (Universal Power Supply), and external VoIP supervisory circuitry, not shown).
Because arcuate portion 204 is always exposed to environmental potential hazards (e.g. water, insects, dust, and human mischief), it is formed to present minimum opportunity and/or access to illegitimate or undesired intrusion/access/interference in engaged position in collar 105. For example, arcuate portion 204 presents a minimized number of, and minimized access to, openings into extender 200 (a single knockout 205 is shown as visible to the passerby while vent hood 250 (for fan 252) is “hidden” in the back). Extender 200 resides securely within collar 105 in an engaged position, as explained above, but does so in releasable way. As shown in
Front securing mechanism 106 includes combination of conventional lock ring 115 and an annular ledge shoulder 116 of extender 200 (as seen in
Back securing mechanism 110 includes one or several snap-fit mechanisms.
As seen in
Also, bottom-back access cover 202 (part of arcuate portion 204) has another snap-fit mechanism, as follows.
As indicated above, one advantageous interface functionality is transformer 300. A common issue with transformers are regulatory and safety concerns and requirements about their thermal output. In particular, air flow, cooling and transformer design are addressed by the present invention.
Bottom-back access cover 202 has air vent hood 250 in air-communication with fan 252 through intermediate filter grill 254 (
There is conventional electronics 313 associated with fan 252 and thermistor 315 to turn on/off fan 252 (in response to monitored thermistor 315 (and/or other thermal sensors within extender 200) to draw air into extender 200 to regulate its internal temperature within desired or regulated limits. Also, there is (not shown) a conventional thermal fuse associated with secondary windings 309 and an over-current fuse immediately after transformer secondary windings 309 for any single point of failures in electronics 313 (that may have, for example, switching power supply).
The temperature within extender 200 may rise too high (and become injurious to the operation of electronics 313 and/or offensive to regulatory thermal restrictions) because of I2R losses from transformer 300.
Thermistor 315 (or resistance temperature detectors or other conventional temperature or heat sensor) is attached to (or equivalently associated with) transformer secondary windings 309. One teaching of the present invention is that by balancing or equalizing the I2R losses of transformer primary windings 308 and secondary windings 309, the single sensor 315 associated with secondary windings 309 will, in effect, quickly and accurately detect the temperature at or proximate primary windings 308 (where some regulations/jurisdictions preclude safety devices like fuses and temperature sensors). The way of balancing or equalizing the I2R losses of transformer primary windings 308 and secondary windings 309, will be explained below.
Electronics 301 may, optionally, supplement thermal regulation by providing conventional thermal regulation accessories, including (not shown) a heat sink and a second thermistor or other thermal sensor proximate secondary windings 309. The heat sink can be any black anodized aluminum surface (or similar material) in such shape as can fit within free space within extender 200 without unduly disturbing air flow therethrough.
The dimensions of extender 200, and of transformer 300 housed therein, are restricted by physical-legal constraints and objectives. Examples of constraints and objectives include: the industry-standardized placement of power pins 109 (S-2, as seen in
For a given or maximum load on the side of secondary windings 309 (for example, a UPS that needs to be recharged from the power line), the primary and second windings 308 and 309 are each composed of the particular combination of parameters such, windings wire material, number of turns of windings and the cross-section of windings wire, so that core 310 is saturated when the secondary load is connected, and thus the transformer becomes inherently current-limiting. With the present invention's insight to saturate the core for a given secondary load and other constraints and objectives (explained above), the particular method of saturating by selecting the best combination of transformer design parameters, is within the normal skills of those in the art; and includes the determination or selection of the number of windings turns, the selection of material of core 310, the cross-section of the windings wires and the like. With core 310 in saturation, it is not difficult (by experimentation, if necessary) to select the number of turns and the cross-sections of primary and secondary windings 308 and 309, so that any expected spiked I2R “hot spot” loss on the secondary windings 309 is reduced to approximate that of I2R loss on the primary windings 308. More generally, there are three main sources of losses in transformer 300 with a given secondary load—losses from each of primary and secondary windings 308 and 309, and losses from core 310; and accordingly, it is advantageous to try to reduce the highest or higher sources of loss by “redistributing” the three sources of losses so as to render transformer 300 into a substantially uniform heat radiator. Although the formerly lower sources of loss will increase as a result of the “redistribution” and the overall total loss of transformer 300 might be higher as the result of “redistribution”, the extreme spikes of loss or “hot spot(s”) will be reduced and thereby advantageously address regulatory thermal requirements. And this is all achieved by putting the core into saturation to determine the best combination of core 310 material, number of turns and cross-section for primary and secondary windings 308 and 309 to “even out” the three heat loss sources.
It is advantageous (but not necessary) to select a core material that has properties of maximum flux transfer between primary and secondary windings (in the “normal” range of operation) and then to determine, for example, the number of turns, while respecting all other constraints. But it may be that some of the other constraints affect the choice of core material and dictate some loss of flux transfer.
One advantage of being inherently current-limiting is that no extra external safety devices are needed for primary windings side (which some jurisdictions/standards require).
a) and 17(b) shows transformer 300 assembled from bobbin holder 302 holding primary bobbin 304 and secondary bobbin 306 around which are respectively primary windings 308 and secondary windings 309, in interactive combination with U-I core 310.
The dimensions of the bobbin holder 302 and the flange walls of bobbins 304 and 306 are such to satisfy regulatory requirements related to spacings between bare live parts of opposite polarity. For example, separations for over-the-air and over-surface creepage may be required to be at least 9.5 mm and 19 mm respectively.
What is shown in
Commonly, transformer bobbins and related parts, are conventionally formed of a single molded plastic (e.g. FR 530) piece to act as an insulator. Primary and secondary bobbins 304 and 306 may be identical so for simplicity of explanation herein, only one will be described.
Fan 252 can be alternatively configured to draw hot air out of extender 200 but in the physical layout illustrated (where transformer 300 is located relative to electronics 313), this dynamic would unadvantageously draw hot air from transformer 300 over the electronics 313. But the (dis)advantages of a direction of fanned air flow depends on the specific interface functionality contents of extender 200 and their physical layout, the air flow paths, and the like, and so configuring the direction of air flow is a simple matter of simple design choice.
Although extender 200 is shown as an assembly of three parts (main body 201 with two access covers 202 and 203), for some applications, only one or no access covers would suffice. Although a removable extender is shown, it need not be removable. Conventional fasteners can be provided so that upon insertion of extender 200 into collar 105, a subsequent removal of extender 200 would require a destructive action of those fasteners or similar. Furthermore, extender 200 need not be discrete from collar 105 and can be mostly formed integrally therewith by conventional plastics technology, leaving only, for example, the bottom-back access cover 202 to be easily detachable as explained herein.
It is possible to simply circulate the air within extender 200 (i.e. draw hot air from transformer 300 and flow it over a heat sink, with no or minimal air flow egress out of extender 200 into the presumably cooler environment). Also, it is possible that the particular interface functionality housed by extender 200 can tolerate a less accurate or quick thermal regulation, in which case, a single temperature sensor (not shown) for the entire extender 200, located proximate transformer 300, would suffice. While these two preceding possibilities may not have a wide range of applications, they may still enjoy the benefits of many aspects of extender 200.
Additional objects and advantages of the invention are set forth in, or will be apparent to those of ordinary skill in the art from, the detailed description herein. Also, it should be further appreciated by those of ordinary skill in the art that modifications and variations to the specifically illustrated, referred and discussed features and steps hereof may be practiced in various embodiments and uses of this invention without departing from the spirit and scope thereof, by virtue of present reference thereto. Such variations may include, but are not limited to, substitution of equivalent means and features, materials, or steps for those shown, referenced, or discussed, and the functional, operational, or positional reversal of various parts, features, steps, or the like.
It is to be understood that different embodiments, as well as different presently preferred embodiments, of this invention may include various combinations or configurations of presently disclosed features, steps, or elements, or their equivalents (including combinations of features or steps or configurations thereof not expressly shown in the figures or stated in the detailed description).
Before any embodiments of the invention are explained in detail, it is to be understood that the invention is not limited in its application to the details of construction and the arrangement of components set forth in the following description or illustrated in the drawings. The invention is capable of other embodiments and of being practiced or of being carried out in various ways. Also, it is to be understood that the phraseology and terminology used herein is for the purpose of description and should not be regarded as limiting. The use of terms “including”, “comprising” or “having” and variations thereof is meant to encompass the items listed thereafter and equivalents thereof as well as additional items. The terms “associated”, “mounted,” “connected,” and “coupled” are used broadly and encompass both direct and indirect association, mounting, connecting, and coupling. Furthermore, “associated”, “connected” and “coupled” are not restricted to physical or mechanical associations, connections or couplings.
Items that are identified herein as “not shown” (or similar) means that they are not illustrated in the drawings only for simplicity of illustration and are, in any case, those conventional items that would be within the conventional design range of the average skilled person in the art. For example, not shown are all the conventional vents and ports for various (air, optical, electrical) inputs and outputs in extender parts like access covers 201 and 202, and body 201 which would be conventionally designed by the skilled person in response to application specific needs. Also, for simplicity of illustration, not all components are shown in all drawings. For example, ring 115 is shown in some drawings but not all.
Although the method and apparatus of the present invention has been described in connection with the preferred embodiment, it is not intended to be limited to the specific form set forth herein, but on the contrary, it is intended to cover such alternatives, modifications, and equivalents, as can be reasonably included within the spirit and scope of the invention as defined by the appended claims. All figures are drawn for ease of explanation of the basic teachings of the present invention only; the extensions of the figures with respect to number, position, relationship, and dimensions of the parts to form the preferred embodiment will be explained or will be within the skill of the art after the following teachings of the present invention have been read and understood. Further, the exact dimensions and dimensional proportions to conform to specific force, weight, strength, and similar requirements will likewise be within the skill of the art after the following teachings of the present invention have been read and understood.
This is a continuation-in-part application of application Ser. No. 12/457,828, filed on Jun. 23, 2009, the entirety of which is hereby incorporated by reference herein and made a part of this specification.
| Number | Date | Country | |
|---|---|---|---|
| Parent | 12457828 | Jun 2009 | US |
| Child | 12822175 | US |
