Patent Application
20190096618
Aspects of the present invention generally relate to a circuit breaker and more specifically relate to a bimetal plate adapted to be used in circuit breakers.
Within circuit breakers, one or more movable electrical contacts may be provided. Such electrical contacts, in some circuit breaker configurations, may be electrically coupled by one or more flexible conductors to a heater-bimetal assembly. The heater-bimetal assembly functions to trip the circuit breaker when a persistent over-current situation is encountered in the electrical circuit protected by the circuit breaker. Tripping involves resistive heating of a heating element, which, in turn, heats a bimetal element thereby causing bending of a bimetal element. Upon bending, the bimetal element makes engaging contact with a portion of a trip mechanism, and if sufficient heating is present will resultantly trip the circuit breaker. This opens the electrical contacts thereby opening the protected circuit.
Currently to modify the current rating of thermal protection we need to modify the bimetal plate of a heater element of a circuit breaker. Until now the solution to control when a trip unit is activated is made by two means, the first is to use a different bimetal for every rating current protected and the second one is changing the properties of the heater to generate the heat required for the bimetal plate to act at different current ratings.
So there is a big quantity of catalogue products since there is one item for every bimetal configuration. However, this problem creates a solution that involves having a big inventory and a complex logistics process to produce the final product and to provide the material source.
Therefore, there is a need for efficiently producing a trip unit of a circuit breaker that is capable to thermally protecting the circuit at two current ratings, meaning it provides dual thermal protection.
Briefly described, aspects of the present invention relate to dividing a bimetal in two parts wherein the size of the sections of the bimetal is to be selected according by the protection ratings required. Embodiments of the present invention provide a solution that produces a trip unit capable of thermally protecting the circuit at two current ratings which means it can provide dual thermal protection. This technique provides a way to reduce the catalogue of products since the trip unit will make possible to offer a product capable of covering two different current ratings.
In accordance with one illustrative embodiment of the present invention, a circuit breaker having a frame is provided. The circuit breaker comprises a bimetal plate having a longitudinal length and a heating element coupled to the bimetal plate to heat a narrow section and a wider section when a current goes through the heating element. The bimetal plate is cut along the longitudinal length into the narrow section and the wider section both being parallel to each other such that the bimetal plate is configured to control when and how a trip mechanism of a trip unit activates. The narrow section and the wider section of the bimetal plate to deflect differently when a same amount of heat is applied in a same amount of time to control when and how the trip mechanism activates such that to allow to have two different current ratings in the frame in that the bimetal plate allows to increment a current protection level from a lower current rating to a higher current rating.
In accordance with another illustrative embodiment of the present invention, a circuit breaker having a frame is provided. The circuit breaker comprises a trip unit including a trip mechanism having a trip bar with a tip, a bimetal plate having a longitudinal length, a heating element coupled to the bimetal plate to heat a narrow section and a wider section when a current goes through the heating element and a selector configured to rotate to a low current position and a high current position in order to pick the current protection level from two options. The bimetal plate is cut along the longitudinal length into a narrow section and a wider section both being parallel to each other such that the bimetal plate is configured to control when and how the trip mechanism of the trip unit activates and wherein the bimetal plate comprises a union of two different metal layers with different thermal expansion coefficients. The narrow section and the wider section of the bimetal plate to deflect differently when a same amount of heat is applied in a same amount of time to control when and how the trip mechanism activates such that to allow to have two different current ratings in the frame in that the bimetal plate allows to increment a current protection level from a lower current rating to a higher current rating.
In accordance with yet another illustrative embodiment of the present invention, a method is provided. The method comprises providing a trip unit including a trip mechanism having a trip bar with a tip, providing a bimetal plate having a longitudinal length, providing a heating element coupled to the bimetal plate to heat a narrow section and a wider section when a current goes through the heating element, and providing a selector configured to rotate to a low current position and a high current position in order to pick the current protection level from two options. The bimetal plate is cut along the longitudinal length into a narrow section and a wider section both being parallel to each other such that the bimetal plate is configured to control when and how the trip mechanism of the trip unit activates and wherein the bimetal plate comprises a union of two different metal layers with different thermal expansion coefficients. The narrow section and the wider section of the bimetal plate to deflect differently when a same amount of heat is applied in a same amount of time to control when and how the trip mechanism activates such that to allow to have two different current ratings in the frame in that the bimetal plate allows to increment a current protection level from a lower current rating to a higher current rating.
Still other aspects, features, and advantages of the present invention may be readily apparent from the following description by illustrating a number of example embodiments and implementations. The present invention may also be capable of other and different embodiments, and its details may be modified in various respects, all without departing from the substance and scope of the present invention. The invention covers all modifications, equivalents, and alternatives falling within the substance and scope of the invention.
To facilitate an understanding of embodiments, principles, and features of the present invention, they are explained hereinafter with reference to implementation in illustrative embodiments. In particular, they are described in the context of a bimetal plate that is cut in two parallel sections to provide two different current ratings within a frame of a circuit breaker. Embodiments of the present invention, however, are not limited to use in the described devices or methods.
The components and materials described hereinafter as making up the various embodiments are intended to be illustrative and not restrictive. Many suitable components and materials that would perform the same or a similar function as the materials described herein are intended to be embraced within the scope of embodiments of the present invention.
These and other embodiments of a circuit breaker are described below with reference to
Consistent with one embodiment of the present invention,
In operation, as a bimetal plate 20 hits the trip bar 10 it moves in a rotational form causing the latch 12 to go up which releases the trip mechanism and contacts go from close to open. In one embodiment, the bimetal plate 20(1) is sectioned in a 75%:25% ratio. As the current goes through the heating element 15(1) heat goes through the bimetal plate 20(1). More the current means more the heat. When relatively more current goes through the heating element 15(1) the 75% section of the bimetal plate 20(1) will deflect and when relatively less current flows though the heating element 15(1) the 25% section of the bimetal plate 20(1) will deflect. In this way, the 3-pole circuit breaker 5 will have two different current ratings. Current can be controlled to activate faster one of the two sections of the bimetal plate 20(1).
The bimetal plate 20(1) is mechanically connected to the heating element 15(1) which is connected in series with the electrical circuit and which has known heat generating electrical resistance properties wherein the rate of heat generation can be correlated to specific magnitudes of electrical current flow therethrough. The heating element 15(1) conducts some of the generated heat to the bimetal plate 20(1), thereby equally elevating the temperature of both strips which comprise the bimetal plate 20(1). Such heating of the bimetal plate 20(1) causes it to bend out of its planar configuration since the two separate strips, from which the bimetal plate 20(1) is formed, elongate to a different length under such temperature elevation.
The bimetal plate 20(1) is positioned in spaced-apart relationship with respect to the trip bar 10 of the trip unit 7 when no current is flowing through the 3-pole circuit breaker 5. However, when electrical current is flowing through the 3-pole circuit breaker 5, the bimetal plate 20(1) bends toward the trip bar 10. When the electrical current flowing through the 3-pole circuit breaker 5 exceeds the predetermined limit for a predetermined period of time, the bimetal plate 20(1) will bend to such an extent that it engages the trip bar 10 thereby rotating it and tripping the 3-pole circuit breaker 5.
Referring to
Turning now to
The bimetal plate 300 has a longitudinal length 25 such that the bimetal plate 300 is cut along the longitudinal length 25 into a narrow section 315 and a wider section 320 both being parallel to each other such that the bimetal plate 300 is configured to control when and how a trip mechanism of the trip unit 7 activates. The heating element 305 is coupled to the bimetal plate 300 to heat the narrow section 315 and the wider section 320 when a current goes through the heating element 305. The narrow section 315 and the wider section 320 of the bimetal plate 300 deflect differently when a same amount of heat is applied in a same amount of time to control when and how the trip mechanism activates such that to allow to have two different current ratings in the frame in that the bimetal plate 300 allows to increment a current protection level from a lower current rating to a higher current rating.
Regarding the configurations of percentage of bimetal metals vs. applied force, appropriate testing can determine the nature of this relationship which can be exploited based on a specific application. The volume of materials gives different deflections of sections of the bimetal plate 400. One region/section can be smaller than other region/section. Different regions/sections heat at different rates. If a section is heated faster, it deflects more and activates the trip unit 7. The trip unit 7 provides a switch to release mechanism to open contacts of the 3-pole circuit breaker 5 of
The partitioning of the bimetal plate 400 modifies the performance of the bimetal plate 400. Also there is need to use a new configuration on the trip bar 10 to allow two positions of function. This combination of the bimetal plate 400 and the trip bar 10 will allow having two different rated currents.
The bimetal plate 400 is being used to control when the trip unit 7 activates. Since the bimetal plate 400 will have two different positions it will implement two different current ratings. The bimetal plate 400 deflects in a direct response of the heat in the part but since there are two sections it will have different deflections when the same heat is applied in the same amount of time. This will provide two different current ratings in the same frame of the 3-pole circuit breaker 5 of
As seen in
The heating element 15 (not shown) may be coupled to the bimetal plate 515 to heat the narrow section 520(1) and the wider section 520(2) when a current goes through the heating element 15. At the low current position 502, the bimetal plate 515 is given heat by the heating element 15 to deflect the wider section 520(2) of the bimetal plate 515 and make the wider section 520(2) hit the tip 510 of the trip bar 505 of the trip mechanism of the 3-pole circuit breaker 5 of
As shown in
In
The bimetal plate 515 may be shaped in different forms depending upon a particular requirement of current ratings. For example, the bimetal plate 515 may be either in a rectangular shape or a trapezoid shape.
As indicated in
As further indicated in
The method 1300 comprises a step 1305 of providing the trip unit 7 including a trip mechanism having the trip bar 505 with the tip 510. The method 1300 further comprises a step 1310 of providing the bimetal plate 515 having a longitudinal length. The bimetal plate 515 is cut along the longitudinal length into a narrow section and a wider section both being parallel to each other such that the bimetal plate 515 is configured to control when and how the trip mechanism of the trip unit 7 activates. The bimetal plate 515 comprises a union of two different metal layers with different thermal expansion coefficients.
The method 1300 further comprises a step 1315 of providing the heating element 15 coupled to the bimetal plate 515 to heat the narrow section and the wider section when a current goes through the heating element 15. The narrow section and the wider section of the bimetal plate 515 to deflect differently when a same amount of heat is applied in a same amount of time to control when and how the trip mechanism activates such that to allow to have two different current ratings in the frame in that the bimetal plate 515 allows to increment a current protection level from a lower current rating to a higher current rating. The method 1300 further comprises a step 1320 of providing the selector 700 configured to rotate to a low current position and a high current position in order to pick the current protection level from two options.
As used herein, “bimetal plate” refers to a bimetallic strip that is used to convert a temperature change into a mechanical displacement. The strip comprises two strips of different metals which expand at different rates as they are heated, usually steel and copper, or in some cases steel and brass. The strips are joined together throughout their length by riveting, brazing or welding. The different expansions force the flat strip to bend one way if heated, and in the opposite direction if cooled below its initial temperature. The metal with the higher coefficient of thermal expansion is on the outer side of the curve when the strip is heated and on the inner side when cooled. Bimetallic strips are used in miniature circuit breakers to protect circuits from excess current. A coil of wire is used to heat a bimetallic strip, which bends and operates a linkage that unlatches a spring-operated contact. This interrupts the circuit and can be reset when the bimetal strip has cooled down. A circuit breaker is an automatically operated electrical switch designed to protect an electrical circuit from damage caused by excess current, typically resulting from an overload or short circuit. A circuit breaker is provided with a first conductive plate fixed with a bimetallic strip attached with a moving contact, a second conductive plate attached with a fixed contact. A bimetallic strip in a circuit breaker bends when a temperature exceeds a specified level which deforms movable plate so as to separate the contacts. The deflection of a bimetallic strip of approximately rectangular configuration is used to provide two different current ratings within a frame of a circuit breaker.
The techniques described herein can be particularly useful for providing two different current ratings within a frame of a circuit breaker. While particular embodiments are described in terms of two different current ratings, the techniques described herein are not limited to just two different current ratings but can also provide multiple current ratings.
Electrical circuit breakers are well known and have been employed for many years to control the flow of electrical current in serially connected electrical circuits. Typically, two modes of operation are provided to control the flow of current in the electrical circuit; a manual mode and an automatic mode.
In the manual mode, a person moves an operating lever between an on position and an off position which closes and opens, respectively, separable contacts within the circuit breaker. This either allows or interrupts the flow of electrical current through the circuit breaker and, thus, through the serially connected electrical circuit.
In the automatic mode of operation, the operating lever is first placed in the on position, thereby allowing electrical current to flow through the circuit breaker. When a predetermined overcurrent condition occurs the circuit breaker automatically opens the separable contacts thereby interrupting the flow of current to the electrical circuit.
The circuit breaker includes an operating mechanism which is mechanically connected to both the operating lever and the separable contacts and which moves the separable contacts between their open and closed positions in response to movement of the operating lever or in response to an automatic signal to open the contacts of the circuit breaker under the prescribed overcurrent conditions. An automatic trip unit is mechanically connected to the operating mechanism and employed to provide such an automatic signal thereby interrupting the flow of electrical current through the circuit breaker and the serially connected electrical circuit, under such prescribed conditions. This is termed “tripping the circuit breaker.”
Automatic trip units, generally, employ two different apparatuses to trip the circuit breaker during overcurrent conditions. One such apparatus employs an electromagnet, which is connected to the electrical current path through the circuit breaker. The electromagnet includes a fixed member and a movable member which develop varying degrees of magnetic flux, therebetween, in relation to the magnitude of current flowing through the circuit breaker. The magnetic flux applies a force to the movable member and rotates it to an extent determined by the magnitude of electrical current flowing through the electrical circuit. The movable member is connected to the trip bar of the trip unit and the trip bar trips the circuit breaker when rotated past a prescribed point.
The circuit breaker is assigned a nominal value, termed “rating,” which is the maximum continuous magnitude of current which may flow through the circuit breaker without tripping. The electromagnet is designed to immediately trip the circuit breaker when the current flow through the electrical circuit exceeds approximately 500 percent of the rating of the breaker.
A second device employed in the automatic trip unit, which responds to overcurrent conditions of less than 500 percent of the rating of the breaker, is a thermal tripping device. Thermal tripping devices, typically, employ a bimetal strip wherein two different, generally, flat pieces of metal are mechanically attached together and define, generally, a planar surface when the temperature of the strips is equal to the ambient temperature surrounding the circuit breaker. The distinct metals from which each strip is constructed have different thermal expansion coefficients so that they elongate to different lengths whenever their temperatures are elevated above ambient.
While embodiments of the present invention have been disclosed in exemplary forms, it will be apparent to those skilled in the art that many modifications, additions, and deletions can be made therein without departing from the spirit and scope of the invention and its equivalents, as set forth in the following claims.
Embodiments and the various features and advantageous details thereof are explained more fully with reference to the non-limiting embodiments that are illustrated in the accompanying drawings and detailed in the following description. Descriptions of well-known starting materials, processing techniques, components and equipment are omitted so as not to unnecessarily obscure embodiments in detail. It should be understood, however, that the detailed description and the specific examples, while indicating preferred embodiments, are given by way of illustration only and not by way of limitation. Various substitutions, modifications, additions and/or rearrangements within the spirit and/or scope of the underlying inventive concept will become apparent to those skilled in the art from this disclosure.
As used herein, the terms “comprises,” “comprising,” “includes,” “including,” “has,” “having” or any other variation thereof, are intended to cover a non-exclusive inclusion. For example, a process, article, or apparatus that comprises a list of elements is not necessarily limited to only those elements but may include other elements not expressly listed or inherent to such process, article, or apparatus.
Additionally, any examples or illustrations given herein are not to be regarded in any way as restrictions on, limits to, or express definitions of, any term or terms with which they are utilized. Instead, these examples or illustrations are to be regarded as being described with respect to one particular embodiment and as illustrative only. Those of ordinary skill in the art will appreciate that any term or terms with which these examples or illustrations are utilized will encompass other embodiments which may or may not be given therewith or elsewhere in the specification and all such embodiments are intended to be included within the scope of that term or terms.
In the foregoing specification, the invention has been described with reference to specific embodiments. However, one of ordinary skill in the art appreciates that various modifications and changes can be made without departing from the scope of the invention. Accordingly, the specification and figures are to be regarded in an illustrative rather than a restrictive sense, and all such modifications are intended to be included within the scope of invention.
Although the invention has been described with respect to specific embodiments thereof, these embodiments are merely illustrative, and not restrictive of the invention. The description herein of illustrated embodiments of the invention is not intended to be exhaustive or to limit the invention to the precise forms disclosed herein (and in particular, the inclusion of any particular embodiment, feature or function is not intended to limit the scope of the invention to such embodiment, feature or function). Rather, the description is intended to describe illustrative embodiments, features and functions in order to provide a person of ordinary skill in the art context to understand the invention without limiting the invention to any particularly described embodiment, feature or function. While specific embodiments of, and examples for, the invention are described herein for illustrative purposes only, various equivalent modifications are possible within the spirit and scope of the invention, as those skilled in the relevant art will recognize and appreciate. As indicated, these modifications may be made to the invention in light of the foregoing description of illustrated embodiments of the invention and are to be included within the spirit and scope of the invention. Thus, while the invention has been described herein with reference to particular embodiments thereof, a latitude of modification, various changes and substitutions are intended in the foregoing disclosures, and it will be appreciated that in some instances some features of embodiments of the invention will be employed without a corresponding use of other features without departing from the scope and spirit of the invention as set forth. Therefore, many modifications may be made to adapt a particular situation or material to the essential scope and spirit of the invention.
Respective appearances of the phrases “in one embodiment,” “in an embodiment,” or “in a specific embodiment” or similar terminology in various places throughout this specification are not necessarily referring to the same embodiment. Furthermore, the particular features, structures, or characteristics of any particular embodiment may be combined in any suitable manner with one or more other embodiments. It is to be understood that other variations and modifications of the embodiments described and illustrated herein are possible in light of the teachings herein and are to be considered as part of the spirit and scope of the invention.
In the description herein, numerous specific details are provided, such as examples of components and/or methods, to provide a thorough understanding of embodiments of the invention. One skilled in the relevant art will recognize, however, that an embodiment may be able to be practiced without one or more of the specific details, or with other apparatus, systems, assemblies, methods, components, materials, parts, and/or the like. In other instances, well-known structures, components, systems, materials, or operations are not specifically shown or described in detail to avoid obscuring aspects of embodiments of the invention. While the invention may be illustrated by using a particular embodiment, this is not and does not limit the invention to any particular embodiment and a person of ordinary skill in the art will recognize that additional embodiments are readily understandable and are a part of this invention.
It will also be appreciated that one or more of the elements depicted in the drawings/figures can also be implemented in a more separated or integrated manner, or even removed or rendered as inoperable in certain cases, as is useful in accordance with a particular application.
Benefits, other advantages, and solutions to problems have been described above with regard to specific embodiments. However, the benefits, advantages, solutions to problems, and any component(s) that may cause any benefit, advantage, or solution to occur or become more pronounced are not to be construed as a critical, required, or essential feature or component.
