OVERLOAD CURRENT DETECTION IN A CIRCUIT INTERRUPTION DEVICE

Abstract

A circuit-interrupting device with overload current detection is provided. It comprises a live conductor, a main contactor, and a first electromagnetic device configured to remove power from an electrical circuit when the overload current exceeds a predetermined percentage of the rated load current. It further comprises a section of conductor that generates heat and a thermal overload current detection mechanism, including a temperature-sensing switch with contacts. The temperature-sensing switch closes its contacts when the temperature reaches a predefined threshold corresponding to an overload current, in which case the temperature-sensing switch electrically couples power to a second electromagnet arranged across the live conductor and a connection to a neutral conductor.The second energized electromagnet generates a magnetic force capable of moving a frame that opens the latch, releasing the spring to open the main contactor, removing energy from the electrical circuit.

Description

OVERLOAD CURRENT DETECTION IN A CIRCUIT INTERRUPTION DEVICE BACKGROUND 1. Field of the invention The aspects of the present invention generally relate to the detection of overload current in a circuit interruption device. 2. Description of the Related Technique Electrical power is distributed to loads in buildings using insulated conductors of varying sizes, appropriate for the current supplied to the load. The amount of current required for safe continuous operation of a given wire gauge is known as the rated current. If the rated current is exceeded, the conductor will overheat to the point where the insulation melts, leading to dangerous situations of electric shock due to the exposed voltage potential energy and flame ignition due to the exposed thermal energy. Initially, fuses were implemented to prevent these hazardous conditions resulting from electrical circuit overload. Over time, fuses were replaced by circuit breakers, which function as resettable switches.The circuit breaker typically has a robust, spring-loaded main contactor, which is held in the closed position by a latch. In situations of very high overload current, exceeding approximately 800% to 1000% of the rated current of an electrical circuit, the overload current itself is used to generate a magnetic force that disengages the latch and releases a spring to open the contactor switch, cutting power to the electrical circuit. For overload current situations greater than 135% but less than approximately 800% to 1000%, a bimetallic device is placed near the latch in series with the electric current so that the heat generated by the overload current causes the bimetallic device to deform, generating a force to disengage the latch, releasing a spring to open the contactor switch, eliminating energy from the electric circuit. The use of a bimetallic device presents several problems. The amount of displacement achieved through deformation of the bimetallic device is very small and requires a high degree of precision. The amount of displacement varies substantially from one piece to another, necessitating calibration to bias the bimetallic device arrangement. This is particularly problematic when mass-producing circuit breakers for commercial sale. After circuit breaker assembly, the bimetallic device arrangement is initially calibrated to a standard configuration known to produce an optimal first-pass test performance of around 70%. Testing the tripping time of a circuit breaker can take up to one minute. The bimetallic device arrangement in non-conforming units is readjusted based on the previous test time result.The adjusted units are retested. Non-conforming units are re-adjusted once more and retested. Any unit that fails to meet requirements after a third round of testing is disassembled, and the bimetallic device and assembly are discarded. The normal overall performance after three rounds of testing is approximately 85%. This is a costly, inefficient, and time-consuming process that results in approximately 15 percent non-conforming units. And the testing time and cost really add up when you're mass-producing millions of units per year. There has been no simple alternative solution that has high accuracy without adding electronic sensors, amplifiers, and potentially a microprocessor for overcurrent time calculations and an electronic AC-DC adapter power supply to power the electronics. Therefore, there is a need to provide an alternative method and apparatus to a bimetallic device. SUMMARY Briefly described, the aspects of the present invention relate to the detection of overload current in a circuit interrupting device. This invention solves the problem by providing an alternative method and apparatus to the bimetallic device that monitors the temperature of a section of an internal conductor in a circuit breaker and generates a force to open a latch, releasing a spring to open a contactor switch and remove energy from the electrical circuit. It does so at a more precise temperature that is repeatable from unit to unit in mass production. The invention utilizes a novel soft magnetic material called Thermorite® developed by Kemet. The magnetic permeability versus temperature characteristic of Thermorite® exhibits a very steep drop in magnetic permeability at its wedge point.Furthermore, Kemet has commercially available a family of thermal reed switches utilizing Thermorite® technology, which offer fast switching response and an accuracy of ±2.5°C. The advantage of this invention is that it eliminates the need for calibration of the thermal overload current detection mechanism in the circuit breakers. The highly inefficient and costly iterative process of calibrating a bimetallic overload current detection mechanism is eliminated, along with the wasted material discarded due to reworking non-conforming circuit breakers, resulting in valuable time and money saved during mass production. The cost savings, improved testing process, and increased efficiency and performance on the factory line more than offset the cost of adding a thermal reed switch and a second electromagnet.In the case of an electronic circuit breaker for ground fault detection and / or arc fault detection, the second electromagnet already exists as a tripping mechanism that activates upon detecting a fault. Therefore, the only additional cost is the thermal reed switch. According to an illustrative embodiment of the present invention, a circuit-interrupting device is provided. It comprises a live conductor, a spring-loaded main contactor held in a closed switching position by a latch, and a first electromagnetic device configured to instantaneously generate a magnetic force capable of unlocking the latch, releasing a spring to open the main contactor and remove power from an electrical circuit when the overload current exceeds a predetermined percentage of a rated load current. It further comprises a heat-generating conductor section and a thermal overload current sensing mechanism including a temperature-sensing switch having contacts.The temperature detection switch is located very close to the conductor section that closes its contacts when the temperature reaches a predefined threshold corresponding to an overload current. In this case, the temperature detection switch electrically couples power to a second electromagnet, which is connected across the live conductor and a neutral conductor. The energized second electromagnet generates a magnetic force capable of moving a housing that opens the latch, releasing the spring to open the main contactor and remove power from the electrical circuit. According to an illustrative embodiment of the present invention, a method is provided for providing overload current detection in a circuit interrupting device. The method comprises providing a live conductor, providing a spring-loaded main contactor held in a closed switching position by a latch, and providing a first electromagnetic device configured to instantaneously generate a magnetic force capable of unlocking the latch, thereby releasing a spring to open the main contactor, which removes power from an electrical circuit when the overload current exceeds a predetermined percentage of a rated load current. The method further comprises providing a section of conductor that generates heat and providing a thermal overload current detection mechanism that includes a temperature-sensing switch having contacts.The temperature detection switch is located very close to the conductor section that closes its contacts when the temperature reaches a predefined threshold corresponding to an overload current. In this case, the temperature detection switch electrically couples power to a second electromagnet, which is connected across the live conductor and a neutral conductor. The energized second electromagnet generates a magnetic force capable of moving a housing that opens the latch, releasing the spring to open the main contactor and remove power from the electrical circuit. BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 illustrates a circuit interruption device without a bimetallic overload current detection mechanism according to an exemplary embodiment of the present invention. FIG. 2 illustrates an empirical model of the temperature versus time characteristic of a heat-generating conductive section of a nominal 20A circuit breaker during various calibration tests according to an exemplary embodiment of the present invention. nc> i nn / cznz / B / viAi FIG. 3 illustrates a circuit interrupting device with a thermal reed switch according to an exemplary embodiment of the present invention. FIG. 4 illustrates a circuit-interrupting device where the current required to energize a second electromagnet exceeds the rated current of a thermal reed switch according to an exemplary embodiment of the present invention. FIG. 5 illustrates a circuit interrupting device that integrates nicely into an electronic ground fault and / or arc fault circuit interrupter to form an additional alternative embodiment. FIGURES 6-8 illustrate a schematic view of a mechanical form of a circuit breaker device according to an exemplary embodiment of the present invention. FIG. 9 illustrates a schematic view of a flowchart of a method for providing overload current detection in a circuit interrupting device according to an exemplary embodiment of the present invention. DETAILED DESCRIPTION To facilitate understanding of the embodiments, principles, and features of the present invention, they are explained below with reference to illustrative implementations. Specifically, they are described in the context of a circuit-interrupting device without a bimetallic overload current detection mechanism. A circuit-interrupting device comprises a thermal overload current detection mechanism that includes a temperature-sensing switch. For example, a circuit-interrupting device includes a thermal reed switch that utilizes a novel soft magnetic material called Thermorite®. The thermal reed switch has a fast switching response and an accuracy of ±2.5°C. The highly inefficient and costly iterative process of calibrating a bimetallic overload current detection mechanism, along with the wasted material, is eliminated.However, the realizations of the present invention are not limited to use in the devices or methods described. The components and materials described below as components of 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 to the materials described herein are intended to be included within the scope of the embodiments of the present invention. These and other embodiments of the circuit-interrupting device according to the present description are described below with reference to Figs. 1-6 herein. Similar reference numbers used in the drawings identify similar or identical elements throughout the various views. The drawings are not necessarily to scale. According to one embodiment of the present invention, FIG. 1 represents a block diagram of a circuit-interrupting device 105 that provides overload current detection according to an exemplary embodiment of the present invention. The circuit-interrupting device 105 does not have a bimetallic overload current detection mechanism. The circuit-interrupting device 105 comprises a live conductor 107, a main contactor 110 that is spring-loaded but held in a closed switching position by a latch 112, and a first electromagnetic device 115 (1) configured to instantaneously generate a magnetic force capable of unlocking the latch 112, which releases a spring 117 to open the main contactor 110, thereby removing power from an electrical circuit when the overload current exceeds a predetermined % 120 of a rated load current 122.For example, the predetermined % 120 of the nominal load current 122 may be 800%. The circuit-interrupting device 105 further comprises a conductor section 125 that generates heat and a thermal overload current sensing mechanism 127 that includes a temperature-sensing switch 130 having contacts 132. The temperature-sensing switch 130 is located very close to the conductor section 125 and closes the contacts 132 when the temperature 135 reaches a predefined temperature threshold 137 corresponding to an overload current 140, in which case the temperature-sensing switch 130 electrically couples power to a second electromagnet 115(2) that is arranged across the live conductor 107 and a connection to a neutral conductor 145.When the circuit interrupting device 105 is an electronic circuit breaker for ground fault detection and / or arc fault detection, it has a second electromagnet 115(2) integrated into a tripping mechanism that is activated upon detecting a fault. The energized second electromagnet 115(2) generates a magnetic force capable of moving a frame 147 that opens the latch 112, releasing the spring 117 to open the main contactor 110, thus removing energy from the electrical circuit. The temperature-sensing switch 130 further comprises a soft magnetic material called Thermorite®, which has a magnetic permeability characteristic with respect to temperature, exhibiting a very steep drop in magnetic permeability at its Curie point. For example, a circuit-interrupting device 105 may include a thermal reed switch utilizing a new soft magnetic material called Thermorite®. The thermal reed switch has a fast switching response and an accuracy of ±2.5°C. The highly inefficient and costly iterative process of calibrating a bimetallic overload current sensing mechanism, along with the wasted material, is eliminated. In the case of an electronic circuit breaker for earth-fault and / or arc-fault detection, the second electromagnet 115(2) already exists as a tripping mechanism that is activated upon detecting a fault.Therefore, the only additional cost is the thermal reed switch. Calibration of the thermal overload current detection mechanism 127 of the circuit interrupting device 105 is not required. However, in a design based on a bimetallic device, the amount of bimetallic device displacement varies substantially from piece to piece, necessitating calibration to bias the bimetallic device arrangement. This is particularly problematic when mass-producing circuit breakers for commercial sale. After circuit breaker assembly, the bimetallic device arrangement is initially calibrated to a standard configuration known to produce an optimum performance percentage of approximately 70% in the first-pass test. Testing the tripping time of a circuit breaker can take up to 1 minute. The bimetallic device arrangement in non-conforming units is readjusted based on the previous test time result.The retested units are retested. Non-conforming units are retested once more and retested. Any unit that fails to meet requirements after a third round of testing is disassembled, and the bimetallic device and assembly are discarded. The overall normal yield after three rounds of testing is approximately 85%. This is a costly, inefficient, and time-consuming process that results in approximately 15 percent non-conforming units. And the testing time and cost really add up when millions of units are mass-produced annually. The predefined temperature threshold of 137 is selected to ensure compliance with the UL489 safety standard. For the 200% and 135% calibration tests performed at an ambient temperature of 25°C, a 15A to 30A circuit breaker must trip within 2 minutes while carrying 200% of its rated current and within 1 hour while carrying 135% of its rated current. For the 100% calibration test performed at an ambient temperature of 40°C, the circuit breaker must not trip while carrying 100% of its rated current until its temperature has stabilized. With reference to FIG. 2, it illustrates an empirical model of the temperature-versus-time characteristic of a heat-generating conductive section of a 20A rated circuit breaker during various calibration tests according to an exemplary embodiment of the present invention. A predetermined threshold 205 of the temperature-sensing switch 130 is set at approximately 120°C to achieve a tripping time of approximately 1 minute while carrying 200 percent of its rated current (25°C ambient), a tripping time of approximately 3.5 minutes while carrying 200 percent of its rated current (25°C ambient), and no tripping while carrying 100 percent of its rated current (40°C ambient), which are within the test limits described in UL489. Figure 3 illustrates a circuit-interrupting device 305 with a thermal reed switch 307 according to an exemplary embodiment of the present invention. The thermal reed switch 307 utilizes Thermorite®, providing a fast switching response and an accuracy of ±2.5°C. The circuit-interrupting device 305 further comprises an optional metal oxide varistor (MOV) 310 arranged across a live conductor 312 and a connection to a neutral conductor 315 to protect the thermal reed switch 307 from overvoltages. The circuit-interrupting device 305 further comprises a second electromagnet 317. If the current required to energize the second electromagnet 317 exceeds the current rating of the thermal reed switch 307, a commercially available thermal reed switch may be used to turn on a solid-state switch that has a current rating to safely and repeatedly supply the current required to energize the second electromagnet 317. It is estimated that the current required to energize the second electromagnet 317 exceeds the rated current ncj i nn / cznz / B / viAi of the thermal reed switch 307. Instead of using a temperature-sensing switch or a custom-designed thermal reed switch that has a current rating to safely and repeatedly supply the current required to energize the second electromagnet, a commercially available thermal reed switch can be used to turn on a solid-state switch that has a current rating to safely and repeatedly supply the current required to energize the second electromagnet 317. Figure 4 illustrates a circuit-interrupting device 405 where the current required to energize a second electromagnet 407 exceeds the rated current of a thermal reed switch according to an exemplary embodiment of the present invention. The thermal reed switch 410 electrically couples energy from a live conductor 412 to a gate 415 of a silicon-controlled rectifier (SOR) 420 through a resistance divider 422 consisting of a 100 kΩ resistor 425 and a 1 kΩ resistor 430, which turns on and energizes the second electromagnet 407 arranged across the live conductor 412 and a connection to a neutral conductor 435 through the SOR 420. The thermal reed switch 410 may be of the make-up or break-down type configured to allow energy to be electrically coupled to the gate 415 of the silicon-controlled rectifier (SOR) 420.The "make" type refers to contacts that normally open and close when a predetermined temperature is reached. The "break" type refers to normally closed contacts that open when the predetermined temperature is reached. As shown in FIG. 5, a circuit interrupting device 505 is well integrated into an electronic ground fault and / or arc fault circuit interrupter to form an additional alternative embodiment. The circuit interrupting device 505 further comprises an electronic ground fault and / or arc fault detection circuit 507 where a second electromagnet 510 and a solid-state switch can be used by a thermal overload current detection mechanism 527 and a ground fault and / or arc fault detection mechanism. In this embodiment, a power supply 513, arranged across a live conductor 501 and a neutral conductor 502, typically converts 120 V AC power to 5 V DC power, which is supplied to the ground fault and / or arc fault detection electronic circuit 507. Upon detection of a ground fault or arc fault, the ground fault and / or arc fault detection electronic circuit 507 asserts a trip signal 530, which is coupled through a 4K resistor 535 to the gate of an SCR 540. This turns on and energizes the second electromagnet 510, which is arranged across a live conductor 501 and a connection to the neutral conductor 502 via the SCR 540. The energized second electromagnet 510 generates a magnetic force capable of moving a housing that opens the latch, releasing the spring to open the contactor switch and remove power from the electrical circuit. As shown in FIGURES 6-8, they illustrate a schematic view of a mechanical form of a circuit breaker device 600 according to an exemplary embodiment of the present invention. FIG. 6 shows the embodiment in its mechanical form when the circuit breaker device 600 is in a reset state where a main contactor 603 is open and a latch 619 is locked by loading a spring 620 of the main contactor 603. This is achieved by moving a handle 623 from an energized position shown in FIG. 8 to the reset position in FIG. 6. A separate spring 621 holds a trip frame 622 in place. FIG. 7 shows the embodiment in its mechanical form when the circuit breaker device 600 is in an energized state where the main contactor 603 is closed by moving the handle 623.Figure 8 shows the mechanical embodiment when the circuit-interrupting device 600 is in an activated state as a result of a thermal switch in FIG. 1 located very close to a heating conductor 605, which activates a second electromagnet 607 upon exceeding a predetermined temperature threshold. The energized electromagnet 607 exerts a force on the trip frame 622, which opens the latch 619, releasing the spring 620. The force of the spring 620 moves the handle 623 to the activated position and opens the main contactor 603, removing energy from the electrical circuit. Figure 9 illustrates a schematic view of a flowchart of a method 900 for providing overload current detection in a circuit interrupting device 105 according to an exemplary embodiment of the present invention. Reference is made to the elements and features described in Figures 1-8. It should be appreciated that some steps do not need to be performed in any particular order, and that some steps are optional. Method 900 comprises step 905 of providing a live conductor. Method 900 further comprises step 910 of providing a main contactor that is spring-loaded but held in a closed switch position by a latch. Method 900 further comprises step 915 of providing a first electromagnetic device configured to instantaneously generate a magnetic force capable of unlocking the latch by releasing a spring to open the main contactor, thus removing power from an electrical circuit when the overload current exceeds a predetermined percentage of a rated load current. Method 900 further comprises step 920 of providing a section of conductor that generates heat. Method 900 further comprises step 925 of providing a thermal overload current sensing mechanism that includes a temperature-sensing switch having contacts.The temperature detection switch is located very close to the conductor section that closes its contacts when the temperature reaches a predefined threshold corresponding to an overload current. In this case, the temperature detection switch electrically couples power to a second electromagnet, which is connected across the live conductor and a neutral conductor. The energized second electromagnet generates a magnetic force capable of moving a housing that opens the latch, releasing the spring to open the main contactor and remove power from the electrical circuit. While the present invention describes a temperature sensing switch based on Thermorite®, it also contemplates a range of one or more types of temperature sensing switch components or other forms of temperature sensing. For example, other types of temperature sensing switch components can be implemented based on one or more of the features presented above without departing from the spirit of the present invention. The techniques described herein may be particularly useful for an electronic ground fault and / or arc fault circuit interrupter. While the specific implementations are described in terms of a particular ground fault and / or arc fault configuration and specific circuit breakers, the techniques described herein are not limited to such a limited configuration and circuit breakers, but may also be used with other configurations and circuit breakers. Although embodiments of the present invention have been described in exemplary forms, it will be evident to those skilled in the art that many modifications, additions, and deletions can be made without departing from the spirit and scope of the invention and its equivalents, as set forth in the following claims. The embodiments and their various advantageous features and details are explained in more detail with reference to the non-limiting embodiments illustrated in the accompanying drawings and detailed in the following description. Descriptions of well-known starting materials, processing techniques, components, and equipment are omitted to avoid unnecessarily obscuring the details of the embodiments. It should be understood, however, that the detailed description and specific examples, while indicating preferred embodiments, are provided for illustrative purposes only and not as a limitation. Various substitutions, modifications, additions, and / or rearrangements within the spirit and / or scope of the underlying inventive concept will be apparent to those skilled in the art from this description. As used herein, the terms comprise, comprising, include, having, or any other variation thereof, are intended to cover a non-exclusive inclusion. For example, a process, article, or apparatus comprising a list of elements is not necessarily limited to only those elements but may include other elements not expressly listed or inherent in such composition, mixture, process or method, article, or apparatus. Furthermore, the examples or illustrations provided in this document should not be considered in any way as restrictions, limitations, or express definitions of any term or terms with which they are used. Instead, these examples or illustrations should be considered as describing a particular embodiment and are illustrative only. Those skilled in the art will appreciate that any term or terms with which these examples or illustrations are used will encompass other embodiments that may or may not occur with the same or elsewhere in the specification, and all such embodiments are intended to be included within the scope of that term or terms. The foregoing description describes the invention with reference to specific embodiments. However, a person skilled in the art will appreciate that various modifications and changes can be made without departing from the scope of the invention. Consequently, the description and figures should be considered illustrative rather than restrictive, and it is intended that all such modifications fall within the scope of the 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 present description of the illustrated embodiments of the invention is not intended to be exhaustive nor to limit the invention to the precise forms described 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 to provide a person skilled in the art with an understanding of the invention without limiting the invention to any particular embodiment, feature, or function described.Although the specific embodiments and examples of the invention are described here for illustrative purposes only, several 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 the illustrated embodiments of the invention and must be included within the spirit and scope of the invention. Therefore, although the invention has been described here with reference to specific embodiments thereof, the foregoing disclosures intend a latitude of modification, various changes and substitutions, and it will be appreciated that in some cases, some features of the embodiments of the invention will be employed without the corresponding use of other features without departing from the scope and spirit of the invention as set forth.Therefore, many modifications can be made to adapt a particular situation or material to the essential scope and spirit of the invention. The respective occurrences of the phrases “in an embodiment” or “in the embodiment” or “in a preferred embodiment” in various places throughout this specification do not necessarily all refer to the same embodiment. Furthermore, the functions, structures, or specific features of any particular embodiment may be combined in any suitable manner with one or more embodiments. It should be understood that other variations and modifications of the embodiments described and illustrated herein are possible in light of the teachings hereof and should be considered part of the spirit and scope of the invention. In this description, numerous specific details, such as examples of components and / or methods, are provided to give a complete understanding of the embodiments of the invention. A person skilled in the relevant art will recognize, however, that an embodiment can 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 cases, known structures, components, systems, materials, or operations are not specifically shown or described in detail to avoid obscuring aspects of the embodiments of the invention. While the invention can be illustrated by the use of a particular embodiment, this does not, and does not, limit the invention to any particular embodiment, and a person skilled in the art will recognize that additional embodiments are readily understandable and form part of this invention. It will also be appreciated that one or more of the elements represented in the drawings / figures may also be implemented in a more separate or integrated manner, or even removed or rendered inoperable in certain cases, as useful according to a particular application. The benefits, other advantages, and solutions to problems have been described above with respect to specific implementations. However, these benefits, advantages, solutions to problems, and any component that may generate or enhance any benefit, advantage, or solution should not be interpreted as a critical, required, or essential feature or component.

Claims

1. A circuit-interrupting device, characterized in that it comprises: a live conductor; a spring-loaded main contactor, held in the closed switch position by a latch; a first electromagnetic device configured to instantaneously generate a magnetic force capable of unlocking the latch by releasing a spring to open the main contactor, thereby removing power from an electrical circuit when the overload current exceeds a predetermined percentage of a nominal load current; a section of conductor that generates heat;A thermal overload current detection mechanism that includes a temperature detection switch having contacts, the temperature detection switch being located very close to the conductor section that closes the contacts when the temperature reaches a predefined temperature threshold corresponding to an overload current, in which case the temperature detection switch electrically couples energy to a second electromagnet that is arranged across the live conductor and a connection to a neutral conductor, where the energized second electromagnet generates a magnetic force capable of moving a frame that opens the latch releasing the spring to open the main contactor removing energy from the electrical circuit.

2. The circuit interruption device of claim 1, characterized in that the temperature sensing switch further comprises: a soft magnetic material called Thermorite® having a magnetic permeability characteristic with respect to temperature exhibiting a very steep drop in magnetic permeability at its Curie point.

3. The circuit-interrupting device of claim 1, characterized in that the temperature-sensing switch further comprises: a thermal reed switch utilizing Thermorite® so as to have a fast switching response and an accuracy of ± 2.5 C.

4. The circuit interruption device of claim 3, characterized in that it further comprises: an optional metal oxide varistor (MOV) arranged across the live conductor and a connection to the neutral conductor to protect the thermal reed switch from overvoltages.

5. The circuit-interrupting device of claim 3, characterized in that if the current required to energize the second electromagnet exceeds the current rating of the thermal reed switch, a commercially available thermal reed switch can be used to turn on a solid-state switch having a current rating to safely supply the current required to energize the second electromagnet.

6. The circuit-interrupting device of claim 3, characterized in that when the current required to energize the second electromagnet exceeds the current rating of the thermal reed switch, the thermal reed switch electrically couples the energy from the active conductor to a gate of a silicon-controlled rectifier (SCR) through a resistance divider, which turns on and energizes the second electromagnet that is arranged across the active conductor and a connection to the neutral conductor through the SCR.

7. The circuit-interrupting device of claim 6, characterized in that the thermal reed switch can be of the make-up or break-up type configured to allow power to be electrically coupled to the gate of the silicon-controlled rectifier (SCR), wherein the make-up type refers to contacts that normally open and close when a predetermined temperature is reached, and wherein the break-up type refers to contacts that are normally closed and open when the predetermined temperature is reached.

8. The circuit interrupting device of claim 1, characterized in that calibration of the thermal overload current detection mechanism of the circuit interrupting device is not required.

9. The circuit-interrupting device of claim 1, characterized in that the circuit-interrupting device is an electronic circuit breaker for earth fault detection and / or arc fault detection having the second electromagnet integrated into a tripping mechanism that is activated upon detecting a fault.

10. The circuit interruption device of claim 1, characterized in that the predefined temperature threshold is selected to ensure compliance with the UL489 safety standard.

11. The circuit interrupting device of claim 1, characterized in that it further comprises: an electronic circuit breaker for earth fault detection and / or arc fault detection wherein the second electromagnet and a solid-state switch can be used by a thermal overload current detection mechanism and an earth fault and / or arc fault detection mechanism.

12. The circuit interruption device of claim 1, characterized in that the predetermined % of the nominal load current is 800%.

13. A method for providing overload current detection in a circuit interrupting device, characterized in that the method comprises: providing a live conductor; providing a spring-loaded main contactor, but held in the closed switch position by a latch; providing a first electromagnetic device configured to instantaneously generate a magnetic force capable of unlocking the latch by releasing a spring to open the main contactor, removing power from an electrical circuit when the overload current exceeds a predetermined percentage of a rated load current; providing a section of conductor that generates heat;providing a thermal overload current detection mechanism that includes a temperature sensing switch having contacts, the temperature sensing switch being located very close to the conductor section that closes the contacts when the temperature reaches a predefined temperature threshold corresponding to an overload current, in which case the temperature sensing switch electrically couples energy to a second electromagnet that is disposed across the live conductor and a connection to a neutral conductor, wherein the energized second electromagnet generates a magnetic force capable of moving a frame that opens the latch releasing the spring to open the main contactor removing energy from the electrical circuit.

14. The method of claim 13, characterized in that the temperature sensor switch further comprises: a soft magnetic material called Thermorite® having a magnetic permeability characteristic with respect to temperature that exhibits a very steep drop in magnetic permeability at its Curie point.

15. The method of claim 13, characterized in that the temperature sensing switch further comprises: a thermal reed switch using Thermorite® so as to have a fast switching response and an accuracy of ± 2.5 °C.

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