CA2278831A1 - Standard sized apparatus for detecting arc faults and ground faults in multiwire branch electric power circuits - Google Patents
Standard sized apparatus for detecting arc faults and ground faults in multiwire branch electric power circuits Download PDFInfo
- Publication number
- CA2278831A1 CA2278831A1 CA 2278831 CA2278831A CA2278831A1 CA 2278831 A1 CA2278831 A1 CA 2278831A1 CA 2278831 CA2278831 CA 2278831 CA 2278831 A CA2278831 A CA 2278831A CA 2278831 A1 CA2278831 A1 CA 2278831A1
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- circuit
- interrupter
- circuit interrupter
- compartment
- knockouts
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Abstract
A two pole circuit breaker adapted to connect to a shared neutral, having arc fault and ground fault protection circuits, in addition to a standard thermal-magnetic trip unit that is designed to fit in the standard knockouts of a three quarter inch circuit breaker load center panel. The circuit breaker is divided in two compartments, one housing the electro-magnetic trip mechanism for both poles and the other the electronics associated with the ground fault and arc fault protection circuits. The circuit breaker spans two of the load center=s knockouts with portions seated within the openings. Each compartment aligns with one of the knockouts.
Description
STANDARD SIZED APPARATUS FOR DETECTING ARC FAULTS
AND GROUND FAULTS IN MULTIWIRE BRANCH
ELECTRIC POWER CIRCUITS
BACKGROUND OF THE INVENTION
Field of the Invention This invention relates to apparatus for providing protection in multiwire branch circuits of electrical power distribution systems, and in particular, to two pole circuit breakers that share a common neutral, for providing protection for arc faults and ground faults in such circuits, that are capable of being mounted in two adjacent standard 3/4-inch slots of a load center panel.
Background Information Branch circuits in electric power distribution systems often share a common neutral conductor to reduce the wiring required. Such multiwire branch circuits are often referred to as "home runs". Home runs are permitted as long as the two line conductors are energized by 120 volt separate phases of a center tapped single-phase transformer to avoid overloading the neutral conductor. This simultaneous disconnection of both of the ungrounded conductors can be accomplished with a two pole disconnect, two single pole circuit breakers with a handle tie, or a two pole circuit breaker.
Presently, such multiwire branch circuits can be provided with short circuit and overcurrent protection by the tied single pole breakers or the two pole breaker. Only a two pole breaker can also provide ground fault protection along with the addition of a common ground fault detector.
Ground fault protection can be either personnel protection or equipment protection.
Recently there has been an increased interest in providing protection from arc faults. Arc faults are intermittent high impedance faults which can be caused for instance by worn insulation, loose connections, broken conductors, and the like. Because of their intermittent and high impedance nature, they do not generate currents of sufficient instantaneous magnitude or sufficient average current to trigger the thermal-magnetic trip device which provides the short circuit and overcurrent protection.
Various types of arc fault detectors have been proposed, but except for the circuit described in Patent Application Serial No. 08/939,263, filed September 29, 1997 (attorney docket 97-PDC-312) such detectors have not been adapted to multiwire branches employing a common ground. A further need exists for an arc fault breaker in a two pole design with a shared neutral for application in common household load centers employing standard face panels with 3/4-inch knockouts.
The prior art has taught employing multiple pole breaker designs such as are taught in Patent Number 5,483,211, filed January 9, 1996, and Patent Number 5,453,723, filed September 26, 1995, where the electronic trip circuits are housed in separate compartments from the thermal-magnetic tripping units and span several breaker slots in a load center. However, none of these arrangements are suitable for a home run configuration. Thus, the art evidences the further need for an arc fault breaker in a two pole design with a shared neutral for application in common household load centers employing standard face panels with 3/4-inch knockouts.
SUMMARY OF THE INVENTION
These and other needs are satisfied by the invention which is directed to an apparatus for detecting faults in multiwire branch circuits, that is capable of fitting within standard load center 3/4-inch knockout panels. It includes a two pole circuit breaker (providing standard circuit protection) having a first pole connected to interrupt current in the first line conductor and a second pole connected to interrupt current simultaneously in the second line conductor. The apparatus further includes fault detection circuitry including a first arc fault detector connected to detect arc currents between the first line conductor and neutral/or ground and to generate a trip signal in response thereto, and a second arc fault detector connected to detect arc currents between the second line conductor and neutral or ground and to generate a trip signal in response thereto, and a ground fault detector connected to detect ground faults between each of the line conductors and ground. The apparatus also includes a conventional thermal-magnetic trip mechanism and means responsive to each of the trip signals to trip the two pole circuit breaker.
Preferably the thermal-magnetic trip unit for both poles is maintained within a standard 3/4-inch circuit breaker case having a face designed to protrude through the standard 3/4-inch load center panel knockouts. The electronic processing circuits for the ground fault and arc faults detection circuits are maintained within a second standard 3/4-inch circuit breaker housing that abuts the first housing on its side so the two housings are aligned and connected at their juncture in a manner that permits them to protrude through adjacent knockouts in the load center panel. In one embodiment the breaker switches protrude through the face of the first housing while the trip indicator and duel trip test button protrude through the face of the second housing. Desirably, electrical shielding is provided at the interface between the first and second housings.
These, together with other objects and advantages which will be subsequently apparent, reside in the details of construction and operation as more fully hereinafter described and claimed, reference being had to the accompanying drawings forming a part hereof.
BRIEF DESCRIPTION OF THE DRAWINGS
AND GROUND FAULTS IN MULTIWIRE BRANCH
ELECTRIC POWER CIRCUITS
BACKGROUND OF THE INVENTION
Field of the Invention This invention relates to apparatus for providing protection in multiwire branch circuits of electrical power distribution systems, and in particular, to two pole circuit breakers that share a common neutral, for providing protection for arc faults and ground faults in such circuits, that are capable of being mounted in two adjacent standard 3/4-inch slots of a load center panel.
Background Information Branch circuits in electric power distribution systems often share a common neutral conductor to reduce the wiring required. Such multiwire branch circuits are often referred to as "home runs". Home runs are permitted as long as the two line conductors are energized by 120 volt separate phases of a center tapped single-phase transformer to avoid overloading the neutral conductor. This simultaneous disconnection of both of the ungrounded conductors can be accomplished with a two pole disconnect, two single pole circuit breakers with a handle tie, or a two pole circuit breaker.
Presently, such multiwire branch circuits can be provided with short circuit and overcurrent protection by the tied single pole breakers or the two pole breaker. Only a two pole breaker can also provide ground fault protection along with the addition of a common ground fault detector.
Ground fault protection can be either personnel protection or equipment protection.
Recently there has been an increased interest in providing protection from arc faults. Arc faults are intermittent high impedance faults which can be caused for instance by worn insulation, loose connections, broken conductors, and the like. Because of their intermittent and high impedance nature, they do not generate currents of sufficient instantaneous magnitude or sufficient average current to trigger the thermal-magnetic trip device which provides the short circuit and overcurrent protection.
Various types of arc fault detectors have been proposed, but except for the circuit described in Patent Application Serial No. 08/939,263, filed September 29, 1997 (attorney docket 97-PDC-312) such detectors have not been adapted to multiwire branches employing a common ground. A further need exists for an arc fault breaker in a two pole design with a shared neutral for application in common household load centers employing standard face panels with 3/4-inch knockouts.
The prior art has taught employing multiple pole breaker designs such as are taught in Patent Number 5,483,211, filed January 9, 1996, and Patent Number 5,453,723, filed September 26, 1995, where the electronic trip circuits are housed in separate compartments from the thermal-magnetic tripping units and span several breaker slots in a load center. However, none of these arrangements are suitable for a home run configuration. Thus, the art evidences the further need for an arc fault breaker in a two pole design with a shared neutral for application in common household load centers employing standard face panels with 3/4-inch knockouts.
SUMMARY OF THE INVENTION
These and other needs are satisfied by the invention which is directed to an apparatus for detecting faults in multiwire branch circuits, that is capable of fitting within standard load center 3/4-inch knockout panels. It includes a two pole circuit breaker (providing standard circuit protection) having a first pole connected to interrupt current in the first line conductor and a second pole connected to interrupt current simultaneously in the second line conductor. The apparatus further includes fault detection circuitry including a first arc fault detector connected to detect arc currents between the first line conductor and neutral/or ground and to generate a trip signal in response thereto, and a second arc fault detector connected to detect arc currents between the second line conductor and neutral or ground and to generate a trip signal in response thereto, and a ground fault detector connected to detect ground faults between each of the line conductors and ground. The apparatus also includes a conventional thermal-magnetic trip mechanism and means responsive to each of the trip signals to trip the two pole circuit breaker.
Preferably the thermal-magnetic trip unit for both poles is maintained within a standard 3/4-inch circuit breaker case having a face designed to protrude through the standard 3/4-inch load center panel knockouts. The electronic processing circuits for the ground fault and arc faults detection circuits are maintained within a second standard 3/4-inch circuit breaker housing that abuts the first housing on its side so the two housings are aligned and connected at their juncture in a manner that permits them to protrude through adjacent knockouts in the load center panel. In one embodiment the breaker switches protrude through the face of the first housing while the trip indicator and duel trip test button protrude through the face of the second housing. Desirably, electrical shielding is provided at the interface between the first and second housings.
These, together with other objects and advantages which will be subsequently apparent, reside in the details of construction and operation as more fully hereinafter described and claimed, reference being had to the accompanying drawings forming a part hereof.
BRIEF DESCRIPTION OF THE DRAWINGS
The foregoing features will be more fully appreciated in view of an illustrative example thereof taken in conjunction with the accompanying figure of which:
Figure 1 is a top prospective view of a circuit breaker housing constructed in accordance with this invention.
DESCRIPTION OF THE PREFERRED EMBODIMENT
Figure 1 illustrates a circuit breaker housing constructed in accordance with this invention. The 10 housing 10 forms two interior compartments 12 and 14. Each of the compartments 12 and 14 are sized to be substantially equivalent in volume and design to a standard 3/4-inch circuit breaker housing. The compartment 12 houses the thermal-magnetic trip mechanism of the circuit breaker which is well known in the art. The thermal-magnetic trip mechanism includes separate thermal-magnetic trip assemblies for each pole, which are tied together by a common trip bar.
Each pole can be reset by using the switch levers 16 and 18 which are connected by handle link 17 so both poles reset simultaneously. Where a common neutral conductor is employed, it is important that both poles are disconnected simultaneously. Though not shown, a male clip is provided under each of the housings 12 and 14 to connect to the hot side of the line respectively for phases A and B. A female clip is also provided on the underside of the breaker and aligned to connect to the line ground in the back panel of the load center. The phase A load wiring is connected to terminal 24 and the phase B load wiring is connected to terminal 26; both terminals being positioned on the periphery of the housing 12.
The second compartment 14 houses the electronics for the ground fault detection circuit and the arc fault detection circuit. The electronics and the operation of the fault detection circuits can be better appreciated by reference to co-pending application serial number 08/939,263 (attorney docket number 97-PDC-312). Preferably electrical shielding is provided between the housings 12 and 14 so that any arcing that occurs within compartment 12 does not affect the electronics housed in compartment 14. A duel test button 22 protrudes through the face of the compartment 14 for testing the ground fault and/or arc fault detection circuits. In addition, a trip indicator is provided on the 5 face of compartment 14. Both compartment 12 and compartment 14, respectively, have a raised portion on their face which fits through the knockout in the load center panel. A
recess 32 is provide between the two raised faces 28 and 30 to seat the crossbar spanning between the knockouts on the load center panel.
Thus, the housing of this invention permits a two pole breaker employing a shared neutral and having arc fault and ground fault trip capability to be seated within a standard 3/4-inch breaker panel in a manner that enables the electronics to be shielded from arcs generated within the thermal-magnetic trip mechanism portion of the housing.
While specific embodiments of the invention have been described in detail, it will be appreciated by those skilled in the art that various modifications and alternatives to those details could be developed in light of the overall teachings of the disclosure. Accordingly, the particular arrangements disclosed are meant to be illustrative only and not limiting as to the scope of the invention which is to be given the full breath of the claims appended and any and all equivalents thereof.
Figure 1 is a top prospective view of a circuit breaker housing constructed in accordance with this invention.
DESCRIPTION OF THE PREFERRED EMBODIMENT
Figure 1 illustrates a circuit breaker housing constructed in accordance with this invention. The 10 housing 10 forms two interior compartments 12 and 14. Each of the compartments 12 and 14 are sized to be substantially equivalent in volume and design to a standard 3/4-inch circuit breaker housing. The compartment 12 houses the thermal-magnetic trip mechanism of the circuit breaker which is well known in the art. The thermal-magnetic trip mechanism includes separate thermal-magnetic trip assemblies for each pole, which are tied together by a common trip bar.
Each pole can be reset by using the switch levers 16 and 18 which are connected by handle link 17 so both poles reset simultaneously. Where a common neutral conductor is employed, it is important that both poles are disconnected simultaneously. Though not shown, a male clip is provided under each of the housings 12 and 14 to connect to the hot side of the line respectively for phases A and B. A female clip is also provided on the underside of the breaker and aligned to connect to the line ground in the back panel of the load center. The phase A load wiring is connected to terminal 24 and the phase B load wiring is connected to terminal 26; both terminals being positioned on the periphery of the housing 12.
The second compartment 14 houses the electronics for the ground fault detection circuit and the arc fault detection circuit. The electronics and the operation of the fault detection circuits can be better appreciated by reference to co-pending application serial number 08/939,263 (attorney docket number 97-PDC-312). Preferably electrical shielding is provided between the housings 12 and 14 so that any arcing that occurs within compartment 12 does not affect the electronics housed in compartment 14. A duel test button 22 protrudes through the face of the compartment 14 for testing the ground fault and/or arc fault detection circuits. In addition, a trip indicator is provided on the 5 face of compartment 14. Both compartment 12 and compartment 14, respectively, have a raised portion on their face which fits through the knockout in the load center panel. A
recess 32 is provide between the two raised faces 28 and 30 to seat the crossbar spanning between the knockouts on the load center panel.
Thus, the housing of this invention permits a two pole breaker employing a shared neutral and having arc fault and ground fault trip capability to be seated within a standard 3/4-inch breaker panel in a manner that enables the electronics to be shielded from arcs generated within the thermal-magnetic trip mechanism portion of the housing.
While specific embodiments of the invention have been described in detail, it will be appreciated by those skilled in the art that various modifications and alternatives to those details could be developed in light of the overall teachings of the disclosure. Accordingly, the particular arrangements disclosed are meant to be illustrative only and not limiting as to the scope of the invention which is to be given the full breath of the claims appended and any and all equivalents thereof.
Claims (13)
1. A circuit interrupter that fits within a load center panel having standard knockouts through a front panel through which a part of the load center=s circuit breakers protrude wherein the circuit interrupter is divided into two compartments and spans two adjacent knockouts, a first of the two compartments housing a two pole thermal-magnetic trip mechanism and the second of the two compartments housing an electronic trip circuit.
2. The circuit interrupter of Claim 1 wherein the first compartment is aligned with a first knockout and the second compartment is aligned with a second knockout.
3. The circuit interrupter of Claim 2 wherein part of the first compartment of the circuit interrupter protrudes through the first knockout exposing a reset handle of the circuit interrupter through the front of the panel.
4. The circuit interrupter of Claim 3 wherein part of the second compartment of the circuit interrupter protrudes through the second knockout exposing a test button for the electronic circuit through the front of the panel.
5. The circuit interrupter of Claim 4 wherein the part of the second compartment that protrudes through the second knockout includes a trip indicator.
6. The circuit interrupter of Claim 4 wherein the electronic trip circuit includes a ground fault interrupter and an arc fault interrupter and the test button activates a test of the ground fault and/or arc fault interrupter circuits.
7 7. The circuit interrupter of Claim 1 wherein the electronic trip circuit includes a ground fault interrupter.
8. The circuit interrupter of Claim 1 wherein the electronic trip circuit includes an arc fault circuit interrupter.
9. The circuit interrupter of Claim 1 wherein the electronic trip unit includes a ground fault interrupter and an arc fault interrupter.
10. The circuit interrupter of Claim 1 for a two pole circuit having a shared neutral.
11. The circuit interrupter of Claim 10 wherein the terminals for the two poles are housed in the first compartment.
12. The circuit interrupter of Claim 1 wherein the knockouts are designed to interface with a 3/4-inch circuit breaker.
13. The circuit interrupter of Claim 12 wherein the first and second compartments occupy no more than a space within the load center that two 3/4-inch traditional breakers would normally occupy.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US12236198A | 1998-07-24 | 1998-07-24 | |
| US09/122,361 | 1998-07-24 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA2278831A1 true CA2278831A1 (en) | 2000-01-24 |
Family
ID=31186192
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA 2278831 Abandoned CA2278831A1 (en) | 1998-07-24 | 1999-07-23 | Standard sized apparatus for detecting arc faults and ground faults in multiwire branch electric power circuits |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA2278831A1 (en) |
-
1999
- 1999-07-23 CA CA 2278831 patent/CA2278831A1/en not_active Abandoned
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| Date | Code | Title | Description |
|---|---|---|---|
| FZDE | Dead |