Compact plane-mounted segmented Rogowski coil

Abstract

The improved PCB Rogowski coil solves challenges brought about by spatial constraints within a circuit interrupter. The disclosed coil includes a plurality of PCBs coupled together as compared to known coils made up of only a single PCB. During the pre-assembly phase, the three PCBs are coupled to each other so as to form a partial coil assembly configured to be mounted onto a primary conductor of a circuit interrupter. After the partial coil assembly is mounted on the primary conductor, the fourth PCB is connected to the partial coil assembly via a press-fit connector to form a complete coil. In contrast to known PCB Rogowski coils configured to be mounted perpendicular to the primary conductor, the disclosed modular PCB Rogowski coil enables a majority of the PCB surface area to be mounted parallel to the primary conductor and thus occupies significantly less space than known PCB Rogowski coils.

Description

Technical Field

[0001] The disclosed concepts generally relate to current sensors, and more particularly, to an optimized design of Rogowski coils for measuring current in circuit breakers and other current measurement applications. Background Art

[0002] Circuit breakers (such as, for example but not limited to, circuit breakers) are commonly used to protect circuits from damage due to various trip conditions, including overcurrent conditions (such as overload conditions), short circuits, or other fault conditions (such as arc faults or ground faults). Referring Figure 1 , a circuit breaker (such as the schematically depicted circuit breaker 1) is typically configured to be electrically connected between a power source 2 and a load 3 via line and neutral conductors 4, 6. A circuit breaker typically includes separable electrical contacts 8 that operate as a switch. When the separable contacts 8 are in contact with each other in the closed state, current can flow through any circuit connected to the circuit breaker 1. When the separable contacts 8 are isolated from each other in the open state, current flow through any circuit connected to the circuit breaker 1 is prevented. Generally, a circuit breaker includes an operating mechanism 10 and a trip monitoring mechanism (such as an electronic trip unit 12), the operating mechanism being designed to quickly open or close the separable contacts 8, and the trip monitoring mechanism using a current sensor 14 or other type of sensor to detect a plurality of fault conditions. Upon sensing a fault condition, the trip unit 12 is configured to instruct the operating mechanism 10 to trip open the separable contacts 8.

[0003] A Rogowski coil is a type of current sensor 14 that is commonly used to monitor AC current flowing through a circuit breaker 1. A schematic diagram of a conventional Rogowski coil current sensor 14 is shown in FIG. 2. A conventional Rogowski coil is constructed as a non-ferromagnetic, generally circular core 15 around which a wire 16 is wound. A first portion 17 of the wire 16 forms multiple turns and is wound around the core 15, and a second portion 18 of the wire 16 is a return portion that passes through the interior of the core 15. The return portion 18 of the wire 16 forms a generally circular shape in a plane.

[0004] The Rogowski coil 14 can be used to detect the current flowing through the primary conductor of the circuit breaker 1 (such as, for example but not limited to, the line conductor 4). To detect the current flowing through the line conductor 4, the Rogowski coil 14 is positioned such that the line conductor 4 and the flow of the current i(t) pass through the center of the coil 14. The ends of the first wire portion 17 and the ends of the second wire portion 18 are located at the same end of the core 15 and form the output terminals of the coil 14. The AC current i(t) passing through the line conductor 4 generates a first voltage signal V(t) across the output terminals. This output voltage signal V(t) is proportional to the rate of change of the current di / dt passing through the line conductor 4. The output terminals of the coil 14 are connected to an integrator and amplifier circuit 20 that generates a second voltage signal V(t), where the second voltage signal V(t) is proportional to the current i(t) passing through the line conductor 4. Thus, the current passing through the line conductor 4 can be determined based on the V(t) signal.

[0005] The function of the Rogowski coil can generally be described as enabling the indirect measurement of the current passing through a conductor by directly measuring and processing the voltage signal induced in a nearby wire, the voltage being induced by the time-varying magnetic field generated by the current passing through the conductor. Note that this general principle can be implemented by a Rogowski coil having a geometry slightly different from that of the conventional coil shown in FIG. 2. In modern circuit breakers, the Rogowski coil is typically implemented as a printed circuit board (PCB) circuit, where the integration and amplification functions performed by the integrator 20 shown in FIG. 2 are typically performed by an analog circuit and then the output thereof is sampled by the analog-to-digital converter (ADC) of a microcontroller.

[0006] Although the PCB assembly (PCBA) is advantageous in several respects, the task of mounting the Rogowski coil PCBA in a circuit breaker presents challenges because the available space within the circuit breaker structure is typically very compact (e.g., <5 mm wide). Known Rogowski coil PCBA typically use circular or oval PCBs that have a relatively large surface area relative to the conductor whose current is being sensed. In addition, for most known Rogowski coil PCBA used in circuit breakers, most of the PCB surface area is mounted perpendicular to the primary conductor (e.g., Figure 1 the line conductor 4 shown in ). Thus, mounting the circular or oval PCB coil vertically uses a large amount of vertical space and is cumbersome.

[0007] Therefore, there is room for improvement in the design of PCB Rogowski coils for sensing current in circuit breakers. SUMMARY OF THE INVENTION

[0008] The improved PCB Rogowski coil assembly disclosed herein meets these and other needs and addresses the drawbacks of known Rogowski coil PCBA. Instead of including only a single PCB, the disclosed improved Rogowski coil assembly includes a plurality of PCBs coupled together. During a pre-assembly phase, three PCBs are coupled to each other to form a partial coil assembly configured to be mounted onto a primary conductor of a circuit interrupter. After the partial coil assembly is mounted onto the primary conductor of the circuit interrupter, a fourth PCB is connected to the partial coil assembly via a press-fit connector to form a complete Rogowski coil positioned around the primary conductor. Contrary to known Rogowski coil PCBA that are configured such that most of the surface area of the PCBA is mounted perpendicular to the primary conductor, the modular design of the disclosed PCB Rogowski coil assembly enables most of the surface area of the PCBs to be mounted parallel to the primary conductor and thus occupies significantly less space than known Rogowski coil PCBA.

[0009] According to one aspect of the disclosed concept, a coil assembly for sensing current passing through a busbar includes: a pre-assembled portion that forms less than an entirety of the coil assembly, a removable portion configured to be coupled to the pre-assembled portion, and a plurality of connectors configured to couple the removable portion to the pre-assembled portion. The pre-assembled portion includes a plurality of PCBs fixedly coupled to each other, wherein each pre-coupled PCB includes a first plurality of wire traces. The removable portion includes a removable PCB that includes a second plurality of wire traces. The coil assembly is configured to be mounted to the busbar in multiple stages, wherein the pre-assembled portion is configured to be mounted to the busbar without the removable portion. The pre-assembled portion and the removable portion are configured such that coupling the removable portion to the pre-assembled portion forms a complete Rogowski coil configured to surround the flow of current passing through the busbar, wherein the Rogowski coil is formed by the first plurality of wire traces and the second plurality of wire traces. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] A full understanding of the present invention can be obtained from the following description of the preferred embodiments when read in conjunction with the accompanying drawings, in which:

[0011] Figure 1 is a schematic diagram of a circuit interrupter including a current sensor and an electronic trip unit;

[0012] FIG. 2 is a schematic diagram of a conventional Rogowski coil that can be used as a current sensor in a circuit interrupter (such as Figure 1 the circuit interrupter schematically depicted in

[0013] Figure 3 shows a perspective view of an electrode unit in a circuit interrupter according to an example embodiment of the disclosed concept, in which an improved PCB Rogowski coil assembly is installed;

[0014] Figure 4 shows Figure 3 a perspective view of the same electrode unit as shown in, in which a prior art PCB Rogowski coil is installed;

[0015] Figure 5A is Figure 3 a front view of the load busbar and the attached PCB Rogowski coil assembly as shown in;

[0016] Figure 5B is Figure 5A a perspective view of the load busbar as shown in, and shows the first stage of installing and assembling the PCB Rogowski coil assembly to the load busbar according to an exemplary embodiment of the disclosed concept;

[0017] Figure 5C is Figure 5B the same perspective view of the load busbar as shown in, and shows the second stage of installing and assembling the PCB Rogowski coil assembly to the load busbar according to an exemplary embodiment of the disclosed concept;

[0018] Figure 5D is a cross-sectional view of the PCB Rogowski coil assembly installed to the load busbar, as indicated by line 5D-5D as shown in Figure 5C ;

[0019] Figure 6 is according to an example embodiment of the disclosed concept Figure 3 and Figures 5A to 5D a perspective view of the improved PCB Rogowski coil assembly as shown in, showing details of the wire traces in the printed circuit board forming the wire trace Rogowski coil;

[0020] Figure 7 is according to an example embodiment of the disclosed concept Figure 6 an exploded view of the improved PCB Rogowski coil assembly as shown in, in which the wire traces are omitted, showing details of the individual PCBs for forming the fully assembled PCB Rogowski coil assembly and the connectors for coupling the individual PCBs to each other;

[0021] Figure 8A is a symbolic representation of the dimensions of the prior art Rogowski coil PCBA shown in Figure 4, which is used to determine the mutual inductance between the prior art coil PCBA and the primary conductor of the circuit breaker;

[0022] Figure 8B is a partial isometric view of the printed circuit board of the coil PCBA shown in Figure 8, showing various surfaces of the printed circuit board;

[0023] Figure 9A is Figure 5D a reproduction of the cross-sectional view of the improved PCB Rogowski coil assembly installed to the load busbar as shown in, including additional reference numerals; and

[0024] Figure 9B is Figure 9A a reproduction of a cross-sectional view of the improved PCB Rogowski coil assembly shown in, with the load busbars omitted, depicting the sizing of the coil assembly for determining the mutual inductance between the improved PCB Rogowski coil assembly and the primary conductor of the circuit breaker according to an example embodiment of the disclosed concept. DETAILED DESCRIPTION

[0025] Directional phrases used herein, such as left, right, front, rear, top, bottom, and derivatives thereof, relate to the orientation of the elements shown in the figures and do not limit the claims unless expressly recited therein.

[0026] As used herein, the term "controller" shall refer to a programmable analog and / or digital device that can store, retrieve, and process data; a control circuit; a computer; a workstation; a personal computer; a microprocessor; a microcontroller; a microcomputer; a processor; a central processing unit; a mainframe computer; a minicomputer; a server; a networked processor; or any suitable processing device or apparatus.

[0027] As used herein, a statement that two or more components are "coupled" together shall mean that the components are directly joined together or joined together through one or more intermediate components.

[0028] As used herein, when ordinal terms such as "first" and "second" are used to modify a noun, such use is only intended to distinguish one item from another and is not intended to require a sequential order unless specifically stated.

[0029] As used herein, the term "digital" shall refer to an integer of one or greater (i.e., plural).

[0030] An improved PCB Rogowski coil is disclosed herein to address the drawbacks of known PCB-type Rogowski coils used in circuit breakers. Known PCB Rogowski coils typically include a single PCB, which results in a design that occupies a large amount of vertical space within the circuit breaker. In contrast, the improved PCB Rogowski coil disclosed herein has a modular design that includes a plurality of individual PCBs coupled together to form a complete Rogowski coil, such that the fully assembled Rogowski coil can occupy significantly less space.

[0031] In Figure 3 is shown an improved PCB Rogowski coil assembly 100 according to an exemplary embodiment of the disclosed concept. Figure 3 A perspective view of the PCB coil assembly 100 installed in the electrode unit 30 of a circuit breaker (such as the circuit breaker 1 schematically depicted in Figure 1 is shown. The electrode unit 30 includes a line busbar 32 (corresponding to Figure 1the line conductor 4) and the load bus 36 shown in correspond to Figure 1 the neutral conductor 6) shown in, wherein the line bus 32 and the load bus 36 are configured to be connected to the power supply 2( Figure 1 ). The line bus 32 includes a central portion 33 from which a plurality of branches 34 extend, and a service input portion 35 adjacent to the central portion 33. The load bus 36 similarly includes a central portion 37 from which a plurality of branches 38 extend, and a service return portion 39 adjacent to the central portion 37. The service input portion 35 and the service return portion 39 are configured to facilitate easy connection of the corresponding line bus 32 and load bus 36 to the power supply 2.

[0032] Each line bus branch 34 corresponds to a load bus branch 38, and a power electronic module 40 is located between the line branch 34 and the load branch 38. Each line bus branch 34 and its corresponding load bus branch 38 may be referred to as a branch pair 41, and each branch pair is configured to supply power to a load. When a load is connected to the branch pair 41, power flows from the power supply 2 through the line branch 34 to the load, and then returns to the power supply 2 through the load branch 38 to complete the circuit.

[0033] FIG. 4 shows a Rogowski coil PCBA 50 representative of a known PCB Rogowski coil, which is mounted on Figure 3 the same load bus 36 shown in. Similar to other typical known PCB Rogowski coils, the Rogowski coil PCBA 50 shown in FIG. 4 includes a single oval or circular PCB 51, wherein wire traces are formed in the PCB 51 to resemble the general structure of the wires 16 of the conventional Rogowski coil 14 shown in FIG. 2 (the wire traces are not visible in FIG. 4 but are further shown and described in conjunction with FIG. 8A). The PCB 51 is formed with a central opening 52 that is configured to receive the load bus service return portion 39 such that the coil PCBA 50 can be mounted on the load bus 36 as shown in FIG. 4. Figure 3 The improved PCB coil assembly 100 depicted in and the known Rogowski coil PCBA 50 depicted in FIG. 4 are designed to have the same maximum achievable sensitivity to each other, i.e., the improved PCB coil assembly 100 has the same mutual inductance with the primary conductor of the circuit breaker 1 as the known Rogowski coil PCBA 50.

[0034] The load bus 36 is depicted in Figure 3 and FIG. 4 as having substantially the same dimensions, and thus the relative dimensions of the improved PCB coil assembly 100 and the known Rogowski coil PCBA 50 having the same maximum achievable sensitivity can be easily compared. Later herein, reference is made to FIGS. 8A to 8B and Figures 9A to 9BAn analysis of the dimensions and maximum achievable sensitivity of the improved PCB coil assembly 100 and the known Rogowski coil PCBA 50 is provided. When comparing FIG. 4 with Figure 3 it can be seen that the circular coil PCBA design 50 occupies a large amount of vertical space (vertical with respect to Figure 3 and the views shown in 4), and a significant reduction in the space occupied by the disclosed improved Rogowski coil assembly 100 compared to the known Rogowski coil PCBA 50 is evident.

[0035] Figure 5A A front view of the load busbar 36 removed from the service panel 30 is shown, with the PCB coil assembly 100 attached, so that the structure of the load busbar 36 can be more easily seen. When viewed in conjunction with Figure 3 it can be seen that the service return portion 39 of the load busbar 36 extends from the central portion 37, and the service return portion 39 includes two sections 43, 44. A notch 42 formed in the central portion 37 of the load busbar (numbered only in Figure 3 observing Figure 5A separates the first section 43 of the service return portion 39 from the central portion 37. The formation of the notch 42 enables the PCB coil assembly 100 to be easily coupled to the first section 43 of the service return portion 39 in a manner suitable for detecting the current passing through the load busbar 36, as described in further detail later in this document with respect to Figure 5A The second section 44 of the service return portion 39 (numbered only in Figure 6 is disposed perpendicular to the first section 43 and is configured to facilitate the easy connection of the load busbar 36 to the power supply 2. Figure 3 Now referring to

[0036] it is noted that the assembly and installation of the PCB coil assembly 100 to the electrical service panel 30 is carried out in two stages. As described in further detail later in this document with respect to Figure 5B and Figure 5C the PCB Rogowski coil assembly 100 is composed of a plurality of printed circuit boards (PCBs) 102 coupled to each other using various connectors. Figure 6 and Figure 7 As described in further detail later in this document with respect to Figure 5B FIG. shows the first stage of coupling the PCB coil assembly 100 to the load busbar 36, in which the pre-assembled portion 103 of the PCB coil assembly 100 is installed on the service return portion 39 of the load busbar 36. The pre-assembled portion 103 includes fewer than all of the PCBs 102 required to complete the PCB coil assembly 100. As described in further detail later in this document with respect to Figure 7 an exemplary embodiment of the complete PCB coil assembly 100 includes four PCBs 102, and the pre-assembled portion 103 includes three of the four PCBs 102 coupled together.

[0037] In Figure 5C it shows the second stage of assembling the coil assembly 100, where the removable part 104 of the PCB coil assembly 100 is coupled to the pre-assembled part 103 to complete the PCB coil assembly 100. Figure 5D It shows a cross-sectional view of the load bus service return part 39 on which the fully assembled PCB coil assembly 100 is mounted, including the pre-assembled part 103 and the removable part 104. It should be noted that only the load bus 36 and the electrode unit 30 are shown and described herein to provide a non-limiting illustrative example of how the improved PCT coil 100 can be mounted in the circuit breaker 1, and it should be understood that the size of the PCT coil assembly 100 can be easily adapted to be used with electrode units different from Figure 3 and Figures 5A to 5D the electrode unit shown in the electrode unit 30 without departing from the scope of the disclosed concept.

[0038] Now referring to Figure 6 and Figure 7 , in an exemplary embodiment of the disclosed concept, the PCB coil assembly 100 includes four rectangular PCBs 102 (each PCB 102 is numbered in Figure 7 ) coupled to each other. Note that all PCBs 102 are depicted as semi-transparent in Figure 6 and 7 to more easily show the features of each PCB 102. Each PCB 102 includes a non-conductive substrate 105 and is formed with a certain combination of wire traces 106, 107, 108 and vias 109 (the traces 106, 107, 108 and vias 109 are shown and numbered in Figure 6 ). The non-conductive substrate 105 of the PCB 102 functions similarly to the core 15 of the conventional Rogowski coil 14 (Figure 2). As shown in Figure 6 , different combinations of wire traces 106, 107, 108 and vias 109 are formed in each PCB 102 such that when all four PCBs 102 are coupled to each other using various connectors (described in detail later in this document in connection with Figure 7 ), the wire traces 106, 107, 108 and vias 109 are positioned in a winding configuration forming a complete trace Rogowski coil 110. Referring again to Figure 6 briefly to Figure 3 , it should be understood that the improved PCB coil assembly 100 is configured such that when the assembly 100 is coupled to the load bus 36, the current flowing through the load bus 36 flows through the loop formed by the wire trace Rogowski coil 110.

[0039] Each PCB 102 has an inner surface 111 that faces the load bus 36 when the PCB coil assembly 100 is mounted to the load bus 36, and an outer surface 112 opposite the inner surface 111 that is disposed away from the load bus 36 when the PCB coil assembly 100 is mounted to the load bus 36. It should be noted that each via 109 extends from the inner surface 111 of its corresponding PCB 102 to the outer surface 112, and this can be best understood by viewing Figure 7 as follows. As Figure 7 marked, for any given via 109 included in a given PCB 102, a first end 109A of the via 109 is disposed on the inner surface 111 of the PCB 102, and a second end 109B of the via 109 is disposed on the outer surface 112 of the corresponding PCB 102 of the via. The first end 109A of the via 109 may alternatively be referred to as the inner end 109A, and the second end 109B of the via 109 may alternatively be referred to as the outer end 109B.

[0040] As Figure 6 marked, when the coil assembly 100 is fully assembled, there is a gap 113 that separates the inner surfaces 111 of all four PCBs 102 from each other, and the gap 113 can be more easily determined by combining Figure 6 viewing Figure 7 as follows. The space between the inner surfaces 111 may be referred to as the "inside" of the PCB coil assembly 100, and all other spaces that are not inside the inside of the coil assembly 100 may be referred to as the "outside" of the coil assembly 100. A first set 106 of wire traces is inner traces formed on the inner surface 111 of the PCB 102, a second set 107 of wire traces is outer traces formed on the outer surface 112 of the PCB 102, and a third set 108 of wire traces is intermediate layer traces formed in an intermediate layer of the PCB 102 between the inner surface 111 and the outer surface 112. Each inner trace 106 extends between the inner end 109A of one via 109 and the inner end 109A of another via 109, while each outer trace 107 extends between the outer end 109B of one via 109 and the outer end 109B of another via 109.

[0041] Figure 6The shape of the fully assembled PCB coil assembly 100 in the exemplary embodiment shown herein is referred to herein as an open rectangular prism. The open rectangular prism is characterized by including a total of four sides (each side being a separate rectangular PCB 102), which four sides form two parallel pairs of PCBs 114 and 115 such that each PCB 102 in a given pair 114, 115 is disposed parallel to the other PCB 102 in the given pair 114, 115. Further, each PCB 102 from a given one of pairs 114 or 115 is adjacent and perpendicular to two PCBs 102 from the other pair 115 or 114. This configuration causes the inner surface 111 of each PCB 102 in pair 114 to face the inner surface 111 of the other PCB 102 in pair 114, and the inner surface 111 of each PCB 102 in pair 115 to face the inner surface 111 of the other PCB 102 in pair 115.

[0042] Inner traces 106 and outer traces 107 form the turns of the Rogowski coil 110 of the wire traces, similar to the first portion 17 of the conventional Rogowski coil wire 16 (FIG. 2). Inner traces 106 and outer traces 107 are electrically connected to vias 109 and are electrically connected to each other through vias 109. Intermediate layer traces 108 form a return portion that passes through the interior of the coil turns 106, 107, similar to how the second portion 18 of the conventional Rogowski coil wire 16 passes through the first portion 17 (FIG. 2). For each given PCB 102 that includes a via 109, the via 109 is formed within the PCB 102 in two rows 201 and 202 (numbered in Figure 6 ), where the two rows 201 and 202 are parallel to each other and parallel to two sides of the rectangular PCB 102. For each given individual wire trace 106 or 107, the wire trace 106 or 107 extends between the vias 109 in row 201 and the vias 109 in row 202, and the length of the given trace is considered to be the distance 116 between the vias 109 in row 201 and the vias 109 in row 202.

[0043] One of the PCBs 102 is designated to include an electrical start lead 120 and an electrical end lead 121. The start lead 120 is electrically connected to the inner trace 106 and the outer trace 107 and is used to form the start of the turn portion of the wire trace coil 110. The end lead 121 is electrically connected to the intermediate layer trace 108 and is used to terminate the return portion of the wire trace coil 110. The start lead 120 and the end lead 121 extend outward from the outer surface 112 of the PCB to the outside of the coil assembly 100 so that a microcontroller or other suitable signal processing device can be connected to the leads 120, 121 to receive and process the voltage signal generated by the coil 110 and generate a measurement of the current passing through the load bus 36. For example but not limited to, it may be necessary to perform integration and / or amplification of the signals obtained at the start lead 120 and the end lead 121.

[0044] In Figure 6 and Figure 7 In the exemplary embodiment of the PCB coil 110 shown in, one of the PCBs 102 used to construct the pre-assembled portion is the long board 122 (numbered in Figure 7 ), and two of the PCBs 102 used to construct the pre-assembled portion 103 are the short boards 123 (numbered in Figure 7 ). The long board 122 has a greater length than the two short boards 123, and the two short boards 123 have equal dimensions relative to each other. Another long board 124 is used as the removable portion 104 of the coil 110, and the long board 124 has the same dimensions as the long board 122 of the pre-assembled portion 103. Figure 7 Details of the connectors used to couple the PCBs 102 to each other in the exemplary embodiment are shown. Note that the relative dimensions of the long boards 122, 124 and the short boards 123 shown in the figure are not intended to be restrictive. Instead, the relative dimensions shown in the figure are depicted to optimize Figure 3 the available space in the electrode unit 30 depicted in, but it should be understood that PCBs of other relative dimensions can be used to appropriately reflect the available space in electrode units of different designs without departing from the scope of the disclosed concept.

[0045] Still referring to Figure 7 , all of the PCBs 102 used to construct the pre-assembled portion 103 of the coil assembly 100 are formed with holes 125 configured to receive press-fit connectors 127, 128. In addition, the PCB 102 used as the removable portion 104 of the coil 110 is formed with a hole 132 configured to receive a snug-fit 134. Note that Figure 7 denotes that the coil assembly 100 is from Figure 6The position of the coil assembly 100 shown in is rotated 180 degrees such that the starting lead 120 and the ending lead 121 are shown on Figure 7 the right hand side of. As Figure 7 shown in, the starting lead 120 and the ending lead 121 include press-fit connection ends adapted to be inserted into the press-fit holes 125.

[0046] Continuing to refer to Figure 7 , a connector 127 having two press-fit ends is used to couple the long board 122 and the short board 123 together so as to form a pre-assembled portion 103 of the coil assembly 100, and a connector 128 having one press-fit end and one mating end is used to couple the removable portion long board 124 to each of the two short boards 123. After the press-fit ends of the connectors 127, 128 are inserted into the holes 125 of the pre-assembled portion PCB 102, the press-fit connections are soldered. Before the second phase of the PCB coil assembly 100 shown in Figure 5C is assembled, the mating cap 134 is inserted into the mating hole 132 of the removable portion long board 124.

[0047] To couple the removable portion 104 of the coil assembly 100 to the pre-assembled portion 103, the removable portion 104 is first positioned such that the mating cap 134 inserted into the mating hole 132 is aligned with the mating end of the connector 128 coupled to the short board 123. Then pressure can be applied to the outer surfaces 112 of the long boards 122, 124 to facilitate insertion of the mating end of the connector 128 into the mating cap 134 so as to firmly couple the removable portion 104 to the pre-assembled portion 103. The press-fit and mating connectors 127, 128 and the mating cap 134 are used in the exemplary embodiment because of their low cost and ease of use. However, it should be understood that several other types of connectors are suitable for coupling the PCBs 102 to each other. It should be noted that any suitable mechanism can be used to couple the PCBs 102 to each other without departing from the scope of the disclosed concept.

[0048] The unique planar mounting design of the improved PCB coil assembly 100 enables the coil windings of the wire trace coil 110 (i.e., traces 106, 107) to capture the magnetic field generated around the primary conductor of the circuit breaker 1 more effectively than the wire traces of known PCBA Rogowski coils. A comparison of the dimensions of the improved PCB coil assembly 100 and the known Rogowski coil PCBA 50 (Figure 4) is given later in this article in Table 1 to demonstrate the advantages of the improved PCB coil assembly 100 over the known PCB Rogowski coil. To make the differences between the disclosed improved PCB coil assembly 100 and the prior art Rogowski coil PCBA 50 obvious, this comparison is based on both assemblies using printed circuit boards with a standard thickness of 1.57 mm and on both assemblies having the same maximum achievable sensitivity of 0.88×10 -7 H, where "sensitivity" represents the mutual inductance between the wire trace coil of the improved assembly 100 or the prior art PCBA 50 and the circuit breaker primary conductor. For example, with respect to the disclosed improved PCB coil assembly 100, the sensitivity is the mutual inductance between the wire trace coil 110 and the circuit breaker primary conductor.

[0049] Table 1 shows the various parameter specifications that a prior art Rogowski coil PCBA (such as the known coil PCBA 50) would need to meet and the comparable parameter specifications that the improved PCB coil assembly 100 would need to meet in order to achieve the same sensitivity of 0.88×10 -7 H (the maximum achievable sensitivity is denoted as the Rogowski mutual inductance (M) in Table 1). The explanations of the parameters listed in Table 1 are as follows. In conjunction with Figures 8A through 8B and Figures 9A to 9B to explain the Table 1 parameters, Figures 8A through 8B depict the parameters of the prior art coil PCBA design 50, Figures 9A to 9B depicting the parameters of the disclosed improved PCB coil assembly design 100. The calculation of the maximum achievable sensitivity of the prior art coil PCBA 50 is explained later in this article in conjunction with Equations (1) and (2), while the calculation of the maximum achievable sensitivity of the improved PCB coil assembly 100 is explained later in this article in conjunction with Equations (3) and (4).

[0050] Before detailing the parameters of Table 1 in connection with the prior art coil PCBA design 50, some details regarding the prior art coil PCBA design 50 shown in FIGS. 8A - 8B should be noted. FIG. 8A is a front view of one surface of the PCBA design 50, which shows a Rogowski coil formed by wire traces formed in the PCB 51, and FIG. 8B is a perspective view provided to better show all surfaces of the PCB 51. Note that FIG. 8A depicts fewer wire traces and turns of the Rogowski coil than a coil PCBA typically has to avoid cluttering the figure. Also note that FIG. 8B shows only two wire traces of the PCBA design 50 rather than the entire wire trace coil to more clearly show certain features of the PCB 51. Further note that the dimensions of the PCB 51 depicted in FIG. 8B are not to scale, as for the coil PCBA 50 depicted in Table 1, the diameter of the circular surface area of the PCB 51 is more than 250 times greater than the thickness of the PCB 51.

[0051] As previously described in connection with FIG. 4 and as shown in FIGS. 8A - 8B, the PCB 51 of the prior art coil PCBA 50 includes a central opening 52 that is configured to receive a conductor whose current i(t) is to be sensed, e.g., the service return portion 39 of the load bus 36 (FIG. 4). The current i(t) represented in FIG. 8A corresponds to the current passing through the load bus 36 (FIG. 4). The PCB 51 further includes a circumference 53 and is formed with wire traces 54 that form a Rogowski coil 55. The PCB 51 is further defined by an inner diameter 57 and an outer diameter 58, where the inner diameter 57 is the diameter of the central opening 52 and the outer diameter 58 is the diameter measured relative to the circumference 53. As shown in FIG. 8B, the PCB 51 includes a first circular surface 60 and a second circular surface 61, and a cylindrical section 62 extending from the first circular surface 60 to the second circular surface 61. The surface shown in FIG. 8A is the first circular surface 60.

[0052] Continuing to refer to FIGS. 8A - 8B, there are three sets of wire traces 54 shown in FIG. 8A: a first set 63 formed on a first circular surface 60, a second set 64 (shown in dashed lines) formed on a second circular surface 61, and a third set 65 formed in the cylindrical section 62 (shown only in FIG. 8A), such that the third set 65 is formed in the intermediate layer of the PCB 51 disposed between the first circular surface 60 and the second circular surface 61. The first set 63 and the second set 64 of wire traces form the turns of the Rogowski coil. The third set 65 of wire traces forms the return portion of the Rogowski coil, as well as the start lead 66 and the end lead 67 for connection to an integrator and / or amplifier circuit. A via 69 formed in the cylindrical section 62 (labeled in FIG. 8B) or other structures suitable for electrically connecting wire traces can be used to connect wire traces from one set to wire traces from another set. As labeled in FIG. 8A, the Rogowski coil includes an inner point 70 and an outer point 71, where the inner point 70 is the point located closest to the current i(t), and the outer point 71 is the point located farthest from the current i(t). For each given individual wire trace 63 or 64, the length of the given trace is considered to be the distance 73 between the inner point 70 and the outer point 71 corresponding to the given trace.

[0053] Table 1

[0054]

[0055] Now, an explanation of the parameters of the prior - art coil PCBA design 50 listed in Table 1 will be provided in conjunction with FIGS. 8A - 8B. The dimension parameter (D) refers to the inner diameter 57 and the outer diameter 58 of the PCB 51 (FIG. 8A). The inner trace distance from the center (i) parameter refers to the distance 74 between the inner point 70 and the current i(t). The outer trace distance from the center (o) parameter refers to the distance 75 between the outer point 71 and the current i(t). The PCB has a thickness 76 of 1.57 mm (labeled in FIG. 8B). The maximum number of turns (N) parameter refers to the number of turns of the wire traces 54 that can be formed in the PCB 51 determined by the via size, the via - to - via gap, and the inner diameter 57. The maximum trace depth (h) parameter refers to the maximum distance between the first set of wire traces 63 and the second set of wire traces 64 (FIG. 8B), which is equal to the length of the via 69.

[0056] Regarding the Rogowski coil 55 of the prior - art coil PCBA 50, the voltage V induced on the Rogowski coil 55 due to the time - varying current on the circuit breaker primary conductor can be calculated using the various parameters listed in Table 1, as represented by Equation (1):

[0057]

[0058] where μ0 is the magnetic permeability of free space, and is the rate of change of the current through the circuit breaker 1. The voltage V across the prior art coil 55 can also be expressed in terms of the Rogowski coil mutual inductance M, as shown in Equation (2):

[0059]

[0060] Therefore, by using the parameters listed in Table 1 to calculate the voltage V using Equation (1), and then using the value of V from Equation (1) to solve for M in Equation (2), the Rogowski coil mutual inductance M of the prior art coil 55 can be found.

[0061] Now will be combined with Figures 9A to 9B Provide an explanation of the parameters listed in Table 1 for the improved PCB coil assembly 100. Figure 9A is mounted on Figure 5D is a reproduction of a cross-sectional view of the improved coil assembly 100 mounted on the load busbar 36 shown, and Figure 9B shows Figure 9A a cross-sectional view of the improved coil assembly 100 shown in, with the load busbar 36 omitted. Referring to the reference numerals used in Figure 9B the width and height dimension parameters (D) of Table 1 refer to the width 151 and height 152 of the fully assembled coil assembly 100 (as shown in Figure 9B shown, the width 151 and height 152 do not include the dimensions of any part of the bonding cap 134 and the starting lead 120 that extend from the PCB 102 to the outside of the coil assembly 100). The width 151 of the assembly 100 is equal to the width of the short board 123, and the reference numeral 151 can be correspondingly used to refer to the width of the short board 123. Each long board 122 and 124 has a height 153, and all four PCBs 102 have a thickness 155. Since the edges of the long boards 122, 124 abut the inner surface 111 of the short board 123, the assembled height 152 is equal to the sum of the height 153 of the long board 122 or 124 and the thicknesses 155 of the two short boards 123.

[0062] Still referring to the parameters listed in Table 1 for the improved PCB coil assembly 100, the trace maximum depth (h) is the distance between the via row 201 and the via row 202 on a given long board 122 or 124 (in Figure 6The maximum distance between the mid - marks), which will achieve the mutual inductance (M) of Rohm given in Table 1. The cross - sectional area parameter (A) refers to the cross - sectional area between the winding traces 106, 107 of each of the long plates 122, 124. Since the inner trace 106 is formed on the inner surface 111 of the long plates 122, 124 and the outer trace 107 is formed on the outer surface 112 of the long plates 122, 124, the cross - sectional area (A) of each long plate 122 or 124 is equal to the maximum depth (h) of the trace multiplied by the PCB thickness 155. The total path length of the loop around the loop parameter (l) refers to the length of the loop formed by the complete wire - trace Rohm coil 110 and is calculated by adding the widths 151 of the two short plates 123 and the heights 153 of the two long plates 122, 124. The maximum number of turns (N) parameter refers to the number of turns of the coil that the wire traces 106, 107 in the PCB 102 can form given the height 153 of the long plates 122, 124 and the length 151 of the short plates 123.

[0063] The mutual inductance M of the disclosed improved PCB coil assembly 100 can be calculated using the parameters listed in Table 1 in the following equation (3):

[0064] M = N×μ0×A / l (3)

[0065] Where μ0 is the magnetic permeability of free space. The voltage V induced on the wire - trace coil 110 of the disclosed improved design 100 is represented by Equation (4):

[0066]

[0067] When comparing the design of the prior - art coil PCBA 50 shown in Figure 4 with Figure 3 the design of the disclosed improved PCB coil assembly 100 and the properties of the prior - art coil PCBA 50 listed in Table 1 and the properties of the disclosed improved coil assembly 100, it is obvious that, compared with the prior - art coil PBA, the disclosed improved PCB coil assembly 100 provides a more economical use of space within the circuit breaker 1 without sacrificing the current - sensing ability. In particular, note that the two long plates 122, 124 include most of the surface area of the improved PCB coil assembly 100, and most of this surface area of the improved assembly 100 is parallel to the first section 43 of the service return portion 39 of the load bus 36 (the first section 43 is in Figure 3 and Figure 5AThe numbering) setting. This results in the lengths 116 of the wire traces 106 and 107 forming the turns of the wire trace coil 110 being set parallel to the flow of the current i(t). In contrast, the first circular surface 60 and the second circular surface 61 include most of the surface area of the prior art coil PCBA 50, and note that most of this surface area of the prior art coil PCBA 50 is set perpendicular to the first section 43 of the service return portion 39 of the load busbar 36. This results in the lengths 73 of the wire traces 63 and 64 forming the turns of the prior art wire trace coil 55 being set perpendicular to the flow of the current i(t).

[0068] While specific embodiments of the invention have been described in detail, those skilled in the art will understand that various modifications and alternatives to those details can be developed in accordance with the general teachings of the disclosure. Accordingly, the particular arrangements disclosed are intended to be illustrative only and not limiting of the scope of the disclosed concepts, the scope of which will be given by the full breadth of the appended claims and any and all equivalents thereof.

Claims

1. A coil assembly for sensing current passing through a busbar, the coil assembly comprising: A pre-assembled part, which forms a whole smaller than the coil assembly, and the pre-assembled part includes: A plurality of pre-coupled printed circuit boards (PCBs), fixedly coupled to each other, and each of the pre-coupled PCBs includes a first plurality of wire traces; A removable part, configured to be coupled to the pre-assembled part, and the removable part includes: A removable printed circuit board (PCB), including a second plurality of wire traces; and A plurality of connectors, configured to couple the removable part to the pre-assembled part, wherein the coil assembly is configured to be mounted to the busbar in multiple stages, wherein the pre-assembled part is configured to be mounted to the busbar without the removable part, and wherein the pre-assembled part and the removable part are configured such that coupling the removable part to the pre-assembled part forms a complete wire trace Rogowski coil, the wire trace Rogowski coil is configured to surround the flow of current through the busbar, and the wire trace Rogowski coil is formed by the first plurality of wire traces and the second plurality of wire traces.

2. The coil assembly according to claim 1, wherein, The pre-assembled part and the removable part are configured such that coupling the removable part to the pre-assembled part forms an open rectangular prism.

3. The coil assembly according to claim 1, wherein, The pre-assembled part includes three pre-coupled PCBs, wherein two of the pre-coupled PCBs are arranged parallel to each other and form a first pair of parallel PCBs, such that the remaining pre-coupled PCB is not in the first pair of parallel PCBs, wherein the remaining pre-coupled PCB is arranged perpendicular to the two pre-coupled PCBs in the first pair of parallel PCBs, wherein the pre-assembled part is configured such that coupling the removable part to the pre-assembled part causes the removable PCB to be arranged perpendicular to the two pre-coupled PCBs in the first pair of parallel PCBs and parallel to the remaining pre-coupled PCB, such that the removable PCB and the remaining pre-coupled PCB form a second pair of parallel PCBs.

4. The coil assembly according to claim 3, wherein, The plurality of connectors includes a plurality of mating connectors, and each of the mating connectors includes a first end and a second end, and the first end is configured to be coupled to one of the pre-coupled PCBs, wherein the plurality of connectors includes a plurality of mating caps, and the mating caps are configured to be coupled to the removable PCB and receive the second end of the mating connector, wherein the first mating connector among the mating connectors is coupled to the first pre-coupled PCB among the pre-coupled PCBs in the first pair of parallel PCBs at its first end, wherein the second mating connector among the mating connectors is coupled to the second pre-coupled PCB among the pre-coupled PCBs in the first pair of parallel PCBs at its first end, wherein the first mating cap among the mating caps and the second mating cap among the mating caps are coupled to the removable PCB, Wherein, the removable portion is configured to be disposed in an alignment position, which is a position where the first mating cap in the mating caps is positioned to receive the second end of the first mating connector in the mating connectors, and wherein the second mating cap in the mating caps is positioned to receive the second end of the second mating connector in the mating connectors, and wherein, the removable portion and the pre-assembled portion are configured such that pushing the removable portion towards the pre-assembled portion when the removable portion is in the alignment position couples the removable portion to the pre-assembled portion.

5. The coil assembly according to claim 3, wherein, The two pre-coupled PCBs in the first parallel PCB pair have the same size as each other. Wherein, the remaining pre-coupled PCB is longer than the two pre-coupled PCBs in the first parallel PCB pair.

6. The coil assembly according to claim 5, wherein, The removable PCB has the same size as the remaining pre-coupled PCB.

7. The coil assembly according to claim 6, wherein, The length of the two pre-coupled PCBs in the first parallel PCB pair is equal to the width of the remaining pre-coupled PCB and the width of the removable PCB.

8. The coil assembly according to claim 1, wherein, The width of the wire trace Rogowski coil does not exceed 18.5 millimeters.

9. The coil assembly according to claim 1, wherein, The width of the coil assembly is 13.22 millimeters or less, and wherein, the height of the coil assembly is 64.02 millimeters or less.

10. The coil assembly according to claim 1, wherein, With respect to the section of the busbar to which the coil assembly is configured to be mounted, the coil assembly is configured such that when the coil assembly is mounted to the busbar, most of the surface area of the coil assembly is disposed parallel to the section of the busbar.

11. The coil assembly according to claim 1, wherein, The wire trace Rogowski coil includes multiple turns. Wherein, the multiple turns are formed by a first subset of wire traces from the first plurality of wire traces and a second subset of wire traces from the second plurality of wire traces. Wherein, the coil assembly is configured such that when the coil assembly is mounted to the busbar, the length of each wire in the first subset of wire traces and the length of each wire in the second subset of wire traces are set to be parallel to the flow of current.

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