RU2772982C2 - Integrated unit for determination of arc and earth fault current - Google Patents

Abstract

FIELD: electrical engineering.

SUBSTANCE: present invention relates to two-functional circuit breakers or arc fault breakers. Linear and neutral conductors for a circuit breaker defining arc fault, for example, a miniature circuit breaker, are made as a rigid conductor surrounding and retaining an isolated flexible conductor, passing through a current transformer of an earth fault protection breaker. The measurement of voltage is carried out in parallel to the rigid conductor to detect arc faults and ground faults in the miniature circuit breaker in the space of a single current transformer.

EFFECT: elimination of a load shift error due to elimination of need for a twisted wire node.

20 cl, 5 dwg

Description

1. Scope of invention

[01] The present invention relates to dual function circuit breakers (arc fault and earth fault) or arc fault breakers that perform earth fault detection as part of fault detection methods, collectively referred to hereinafter as "arc fault detection" breakers or switches and , in particular, to such miniature arc fault breakers and sockets, which are most often used in residential areas.

2. Description of the prior art

[02] FIG. 1 shows the main features of a prior art circuit breaker 10 of the earth fault breaker type and shows a schematic representation of the line current path 1. The path of the linear current starts from the network terminal 13 of the interrupter 10 and passes through the removable contacts 15 and the toroidal current sensor 17 of the current transformer to the load terminal 18, which is connected to the load branch 22, in this case represented by the motor. The mechanical "side" or section 16 of the circuit breaker 10 comprises thermal and magnetic circuit breaker modules 19, typically a bimetal assembly and a magnetic deflection assembly, respectively, which are the components for tripping, i. disconnection of contacts 15 under current overload conditions.

[03] The electronic "side" or portion 20 of the arc fault detection circuit breaker 10 includes a current sensor in the form of a current transformer 17 and associated electronics 21 for evaluating ground fault events. The electronics 21 controls the actuator 23, typically a solenoid, the function of which is to open the releasable contacts 15 and cut off the power supply to the load 22.

[04] Return neutral path 24 current from load 22 is from load 22 to neutral terminal 28 through current transformer current sensor 17 and to neutral return wire 26. It should be understood that a neutral type plug-in breaker will have a terminal clamp and not the coiled wire shown. .

[05] The directions of current in the power conductors and neutral conductors are opposite when the conductors pass through the sensor housing of the earth fault current transformer 17 . Each conductor carrying current creates a magnetic flux, which corresponds to the "right hand rule" used to determine the direction of magnetic flux. When a current of the same magnitude flows in opposite directions through two conductors, the magnetic flux of one conductor dampens the magnetic flux of the other conductor. In this case, the net value of the magnetic flux is zero. If the earth fault protection breaker outputs a current equal to the current returned to the breaker, the earth fault sensor will not output any signals. If a current imbalance occurs in the wires, the earth fault circuit breaker sensor outputs a current proportional to this current imbalance and if this imbalance exceeds a predetermined limit, the earth fault circuit breaker detects the presence of an earth fault and interrupts the electrical current.

[06] A known issue with earth fault breaker sensors is that if the conductors in the sensor are not positioned correctly, uneven magnetic fields in the current sensor assembly can cause current to be output from the current sensor, even if the total current across the conductors is balanced. The result is an inaccurate current sensor output, known as load shift error. Typically this error is compensated for by twisting the main conductors (line and neutral) as they pass through the earth fault current transformer. It has been proposed, for example, in US Pat. No. 3,725,741 issued to Misencik, to replace the twisted pair of main conductors (line and neutral) with a rigid tubular outer conductor surrounding an insulated flexible conductor passing through a hole in the current transformer of the earth fault circuit breaker.

[07] The dual-function circuit breaker performs both the earth fault protection function and the arc fault protection function. Therefore, known devices typically add another current transformer (not shown) to measure current anomalies indicative of a fault event. One of the primary current conductors, i.e. the line wire or the neutral current wire is routed through both the ground fault and arc fault current transformers, and the other wire is routed only through the ground fault sensor. Of course, the available space for installing current transformers and wiring in a miniature circuit breaker is rather limited. It has also been proposed in the prior art to measure the voltage drop across an already present conductor in order to detect current anomalies in an arc fault. US Pat. No. 6,232,857 to Mason Jr et al. proposes using a bimetal thermal resistive breaker element in an arc breaker circuit breaker to detect such arc fault currents.

Brief description of the invention

[08] The line and neutral conductors for the miniature arc fault circuit breaker are arranged as an improved rigid conductor surrounding and holding the insulated flexible conductor as it passes through the current transformer of the earth fault circuit breaker.

[09] The integrated arc and earth fault current detection unit uses a so-called "pseudo-coaxial bus", i.e. rigid conductor enclosing and holding a flexible insulated conductor passing through the core of a current transformer instead of stranded wires to better control the load shear characteristics inside the earth ground current sensor. Aspects of the present invention can be used to determine line current draw by means of pseudo-coaxial bus voltage drop to detect arc faults in the system. Integrating line current measurement with the pseudo-coax bus allows the line current sensor to be efficiently placed in a space also used for ground fault detection, thereby eliminating the need for an arc fault current transformer. The pseudo-coaxial layout also creates a more appropriate route for the line and neutral wires to achieve more consistent load shear behavior while eliminating the need for a twisted wire knot.

[010] In one aspect of the present invention, a miniature two-function breaker (arc and earth fault protection) with line current and neutral current paths and a current transformer with a hole for detecting earth fault current anomalies is provided, containing a rigid conductor, surrounding and holding flexible conductor; wherein the rigid conductor and the flexible conductor pass through a hole in the earth fault detection current transformer inside the miniature circuit breaker; and a voltmeter measuring the voltage drop across the rigid conductor and transmitting the voltage drop measurement to the arc fault detector.

[011] In some aspects of the present invention, a rigid conductor is connected to and forms part of the neutral connection current path. Alternatively, the rigid conductor may be part of a line connection and the neutral line may be connected via a flexible conductor surrounded by a rigid conductor. The rigid conductor may also be given the function of creating increased resistance to current, for example, electrical resistance in the rigid conductor is created by a reduced wall thickness in a substantially tubular cross section.

[012] Other aspects of the present invention provide an improvement in an arc protection type earth fault breaker device comprising a magnetic core current transformer having an opening; printed circuit board with electronics for detecting ground fault events; first and second primary conductors passing through the core; while the first primary conductor is essentially a rigid conductor, the tubular part of which is located inside the core and having non-tubular second and third parts located outside the core and passing at angles to the tubular part; while one of the second and third parts is fixed on the printed circuit board; wherein the second primary conductor is a flexible wire held within the tubular portion of the first primary conductor substantially coaxially; wherein the current sensor further comprises a secondary winding containing a plurality of turns on the core; an opening circuit that responds to detected signals on the secondary winding; and a voltmeter connected in parallel with the substantially rigid conductor to detect arc fault currents. In some aspects, in a miniature circuit breaker, one of the voltmeter wires may be attached to a printed circuit board. In other aspects, the tubular portion of the rigid conductor may not form a fully enclosed tube.

Brief description of the drawings

[013] The above and other advantages of the disclosed embodiments of the present invention will be apparent from the following detailed description with reference to the drawings where:

[014] FIG. 1 is a schematic illustration of the working parts of a known arc fault protection interrupter.

[015] FIG. 2 is an inside view of the mechanical part of a conventional arc fault breaker.

[016] FIG. 3 is an exploded view of the electronics of the breaker of FIG. 2 according to the present invention.

[017] FIG. 4 is a perspective view of the printed circuit board of a dual-function circuit breaker, with an integrated arc fault and earth fault detection unit of the present invention, using a single earth fault detection current transformer.

[018] FIG. 5A, 5B, and 5C are exemplary rigid conductors used to assemble pseudo-coaxial conductors through the earth fault circuit breaker current transformer.

Detailed description

[019] First of all, it should be understood that the development of a real commercial solution that uses aspects of the options described will require specific decisions specific to that option to achieve the ultimate goal facing the developer to create a commercial solution. Such variant-specific decisions may include, but are not limited to, likely to be consistent with relevant system, business, regulatory requirements, and other constraints that may vary by variant, location, and change over time. Although in the absolute sense, the developer's efforts can be complex and time consuming, such efforts are nonetheless routine for those skilled in the art to take advantage of the present invention.

[020] It is also to be understood that the embodiments described and shown may take various and numerous forms and may be subject to various and numerous variations. Therefore, the use of terms in the singular does not limit the number of objects. Likewise, relative terms such as but not limited to "top", "bottom", "left", "right", "top", "bottom", "down", "up", "side", etc. . used in the written description are given for clarification in specific reference to the drawings and do not limit the scope of the present invention.

[021] Words that define relative values, such as "approximately", "substantially", etc., are used in the present description in the sense of "at, or almost at", taking into account manufacturing, design tolerances and tolerances on materials, applicable in the circumstances" and are used to prevent an unfair patent infringer from unfairly taking advantage of the invention, when exact or absolute numbers are given and operational or design relationships are described as an aid to understanding the invention.

[022] One of ordinary skill in the art will appreciate that well-known electronic miniature breaker components that are not necessary to present the present invention are not described in detail, but are understood to be present in the operation of the breaker as briefly described above. Although the present invention is described in the context of a miniature circuit breaker, those skilled in the art will appreciate that the invention is applicable to other forms of arc fault sensing circuit breakers, such as socket outlets or monitoring systems.

[023] In FIG. 2 shows the "mechanical part", i.e. a portion of a partially assembled arc fault detection circuit breaker 30, in accordance with some aspects of the present invention. The terms "part" and "section" are used herein to convey the meaning of a functional grouping that may or may not exist as discrete physical arrangements in a breaker design. Further, the description may use some of the general reference numerals in FIG. 1 and the rest of the drawings, if the functionality of the components in these drawings is essentially the same. The path of the linear (power) current begins at the line terminal 13 of the breaker 30 and passes through the break contacts 15 to the movable contact lever 74 and passes through the wire 72 through the mechanical opening sections of the yoke 74 and the bimetallic element 76, which cause a mechanical opening, disconnecting the plate 78 of the yoke latch 74 from the release lever 80. The current path then passes through the earth fault circuit breaker current transformer 34, as will be described below, to exit at load terminal 18, which is wired to load leg 22 (FIG. 1).

[24] FIG. 3 shows an electronic "part" or portion 31 of an arc fault detection circuit breaker 30 comprising a current transformer current sensor 34 and associated electronics 52 mounted on a circuit board 50 for judging arc fault and ground fault events. Electronics 52 controls a solenoid actuator 53 whose function is to move latch plate 78 (FIG. 2) away from release lever 80 to open shared contacts 15 and remove power from a load (not shown). The return (neutral) current path from the load extends from the neutral return terminal 28, which is the second end of the rigid conductor 36, through the current sensor current transformer 34, as described below, and to the neutral return (spiral) wire 26 and the neutral socket 82, both of which are shown here for clarification.

[025] In FIG. 4 is an overview of the PCB 50 of the arc fault detection circuit breaker with an integrated arc fault and earth fault detection unit 32 using a single earth fault current transformer 34 acting as a current sensor. As understood in the art, the current transformer 34 comprises a toroidal core wound within a housing. As shown in FIG. 4 and FIG. 5A-5C, a rigid conductor 36 extends through the opening 40 of the toroidal core of the transformer, surrounding and holding the insulated flexible conductor 38, i. e. a wire located here to carry the line current through the breaker, and terminating at load terminal 18 for connection to the load branch line. This design creates a so-called "pseudo-coaxial conductor" for use in the integrated arc and earth fault current detection unit 32 of the present invention, which includes a current sensor 34, a rigid conductor 36, a voltmeter 54, and associated electronics 52. The rigid conductor 36 is connected with a neutral return wire 26, sometimes referred to as a helix, at the first end 42 of the rigid conductor as part of the neutral current path through the circuit breaker 30. The second end 44 of the rigid conductor 36 is formed as the neutral terminal 28 of the circuit breaker 10 for connection to the neutral line of the load branch (not shown).

[026] The rigid conductor is fixed, for example, by soldering, to the printed circuit board 50 along with various other electronic components, collectively indicated by the position 52, necessary to perform the functions of interrupting the interrupter 50. These electronic components include a voltmeter 54 (Fig. 4), leads which can be built into the printed circuit board 50 and contact the rigid conductor 36 where it is soldered to the board, for example, on one of its pins 57 (Fig. 5B), for connection in parallel with the first end 42 and the second end 44 of the rigid conductor 36 for providing the functionality necessary to detect a rapid change in voltage and current in rigid conductor 36 indicative of an arc current event. Such a design can thus eliminate the need for a second current transformer for arc fault detection, which is typically found in prior art miniature dual function circuit breakers.

[027] FIGS. 5A, 5B, and 5C show three variants 36a, 36b, and 37c of rigid connector 36 used to assemble pseudo-coaxial conductors through the earth fault protection breaker current transformer. Each rigid conductor 36a, 36b, and 37c may begin as a flat plate-like portion stamped, bent, and bent in the process of making the rigid conductor of pseudo-coaxial sensor assembly 32. In each embodiment, the first end 42 of the rigid conductor 36 is bent to form an open cylinder of flexible wire connection point 60 within the interrupter. While this wire is described herein as carrying a neutral current, it should be understood that the rigid conductor 36 may otherwise be designed to carry line current as well. The central tubular part 62, in this case not closed in all three cases, is formed by bending the wider central part of the plate. The central part in Fig. 5A is bent and/or twisted through 180°. The central part in Fig. 5B is bent and/or twisted by 90°, and the central part in FIG. 5C has a so-called zero-degree twist, in which the edges of the central plate are simply rotated towards each other with respect to the axis of the original plate. The central part in Fig. 5C additionally has a feature 64 for adding resistance to current, which is stamped in the central part as a section of the wall of reduced thickness.

[028] To optimize load shear performance and line current detection, as well as optimize voltage drop at both typical frequencies of 50 and 60 Hz, and at higher frequency signatures during arc faults, many variations of the pseudo-coaxial conductor concept can be used using different geometries. , some examples include the shape, length, thickness of the material of the coaxial conductor, etc.

[29] Rigid conductor in combination with PCB conductors can additionally be used to replace individual wiring connections to the module. For example, the power input and test (PTT, push-to-test) input can be implemented using a hardwire instead of using jumper wires. It should also be understood that the rigid conductor body can be insulated to reduce dielectric problems with surrounding components. Similarly, it should be understood that rigid conductor 36 in a pseudo-coaxial design may be connected either via the line (hot) wire or via the neutral wire.

[030] While specific aspects, embodiments, and uses of the present invention have been described and illustrated above, it should be understood that the present invention is not limited to the precise structures and compositions described, and various alterations, substitutions, and variations may be made from the foregoing description, without going beyond the scope of the invention as defined by the appended claims.

Claims (41)

1. A dual function circuit breaker device with arc fault and ground fault detection functions, comprising: flexible conductor; current transformer with a hole for detecting current anomalies in case of earth fault; a rigid conductor configured to surround and hold the flexible conductor, the rigid conductor and the flexible conductor passing through a hole in the current transformer, the rigid conductor comprising: a slotted central tubular portion having a first open end and a second open end; a second slotted tubular portion having a first open end; a rigid connector that connects the first open end of the central tubular portion to the slot and the first open end of the second tubular portion to the slot at a substantially right angle; and a non-tubular neutral terminal connected to a second open end of the central tubular portion with a slot substantially at a right angle; and a voltmeter configured to measure the voltage drop across the rigid conductor and report the results of the voltage drop measurements to the electronic circuit of the arc fault detector. 2. The dual function circuit breaker device of claim 1, wherein the device has only one current transformer. 3. The dual function circuit breaker device of claim 1 wherein the rigid conductor is connected to and forms part of the return neutral current path. 4. The dual function circuit breaker device of claim 1, wherein the rigid conductor has electrical resistance features placed in a slotted central tubular portion to provide increased resistance to current flowing through the rigid conductor. 5. The dual function circuit breaker device of claim 1, wherein the electrical resistance feature in the rigid conductor is created by reduced wall thickness in the section of the rigid conductor. 6. A miniature circuit breaker of the arc fault type, comprising: a current transformer with a magnetic core in which a hole is made; printed circuit board with electronics for detecting ground fault events; first and second primary conductors passing through the core; wherein the first primary conductor is a substantially rigid conductor comprising: a central tubular portion with a slot located inside the magnetic core, in which the hole is made, and having a first open end and a second open end; a second slotted tubular portion having a first open end; a rigid connector that connects the first open end of the central tubular portion to the slot and the first open end of the second tubular portion to the slot at a substantially right angle; and a non-tubular neutral terminal connected to a second open end of the central tubular portion with a substantially right angle slot, fixed on the printed circuit board; wherein the second primary conductor is a flexible wire held within the tubular portion of the first primary conductor substantially coaxially; a current transformer further comprising a secondary winding comprising a plurality of turns on the core; an opening circuit that responds to the received signals on the secondary winding; and a voltmeter connected in parallel with a substantially rigid conductor to detect arc fault currents. 7. The miniature circuit breaker of claim 6 wherein one of the leads of the voltmeter is attached to the printed circuit board. 8. A miniature circuit breaker according to claim 6, wherein the tubular portion does not form a fully enclosed tube. 9. The dual function circuit breaker device of claim 1, wherein the non-tubular neutral terminal includes one or more pins. 10. The dual function circuit breaker apparatus of claim 1, wherein the opening of the slotted central tubular portion is oriented substantially 180 degrees from the front side of the rigid conductor. 11. The dual function circuit breaker apparatus of claim 1, wherein the opening of the slotted central tubular portion is oriented substantially 90 degrees from the front side of the rigid conductor. 12. The dual function circuit breaker apparatus of claim 1, wherein the opening of the slotted central tubular portion is oriented at substantially 0 degrees from the front side of the rigid conductor. 13. The dual function circuit breaker device of claim 1, wherein the non-tubular neutral terminal comprises a flat rigid terminal made of a conductive material. 14. The miniature circuit breaker of claim 6 wherein the rigid conductor has electrical resistance features placed in a slotted central tubular portion to provide increased resistance to current flowing through the rigid conductor. 15. The miniature circuit breaker of claim 6, wherein the electrical resistance feature in the rigid conductor is provided by reduced wall thickness in a substantially tubular section. 16. The miniature circuit breaker of claim 6, wherein the non-tubular neutral terminal includes one or more pins. 17. The miniature circuit breaker of claim 6 wherein the opening of the slotted central tubular portion is oriented substantially 180 degrees from the front side of the rigid conductor. 18. The miniature circuit breaker of claim 6 wherein the opening of the slotted central tubular portion is oriented substantially 90 degrees from the front side of the rigid conductor. 19. The miniature circuit breaker of claim 6 wherein the opening of the slotted central tubular portion is oriented at substantially 0 degrees from the front side of the rigid conductor. 20. Rigid conductor for use in breaker devices, comprising: a slotted central tubular portion having a first open end and a second open end, a second slotted tubular portion having a first open end, a rigid connector that connects the first open end of the slotted central tubular portion and the first open end of the slotted second tubular portion substantially at a right angle, and a non-tubular neutral terminal connected to the second open end of the central tubular part with a slot essentially at a right angle, and the non-tubular neutral terminal includes one or more pins and the opening of the central tubular part with a slot is oriented 180 degrees from the front side hard conductor.

Images