Current sensor for monitoring electrical system

Abstract

A current sensing system for fault detection includes a sensing element for detecting a magnetic field, and a magnetic core enclosing at least two target conductors. The sensing element is mechanically decoupled from the magnetic core and is designed to detect a component superimposed by a magnetic field generated by a current in the target conductor, which field is generated within the core and passes through an opening in the core. A sensing element provides an output signal indicative of such superposition. The system can detect the magnetic field effect of a combination of multiple currents, thereby achieving accurate fault detection in an electrical system.

Description

Technical Field

[0001] The present invention relates to a current sensing system for fault detection in electrical systems, and more particularly to a system including magnetic sensors. Background Art

[0002] The field of current sensing is a critical aspect of modern electrical systems, encompassing a wide range of applications from industrial automation to consumer electronics, including power accumulation or energy conversion. Current sensors are important for monitoring the flow of electricity and ensuring the safety, efficiency, and reliability of electrical circuits. They are used to detect overcurrent conditions, measure power consumption, and identify faults within electrical systems.

[0003] In polyphase electrical systems (such as those found in industrial environments), the ability to simultaneously monitor the currents of multiple phases is particularly important. These systems typically employ multiple current-carrying conductors, and the currents can be phase-shifted relative to each other. Accurate detection and monitoring of these currents are crucial for system control and fault detection.

[0004] A common problem in this field is the detection of faults such as ground faults or short circuits within polyphase systems. Faults can have severe consequences, including equipment damage, system downtime, and safety hazards. Therefore, it is crucial to detect such faults promptly and accurately to initiate protective measures.

[0005] Another challenge in this field is the design of current sensors that can operate effectively within the constraints of a compact and densely packed electrical environment. This integration presents its own set of challenges, such as ensuring accurate sensing despite the close proximity of conductors and managing the effects of electromagnetic interference.

[0006] Existing devices include coils wound around cores. Due to the requirement for a large number of windings and accurate components, these systems are expensive, bulky, and have a high manufacturing complexity for high sensitivity.

[0007] Despite the progress in current sensing technology, there is still a need for further improvement in this field. The industry continues to seek solutions that can provide accurate, reliable, and efficient current sensing capabilities to meet the evolving needs of modern electrical systems. Summary of the Invention

[0008] An object of embodiments of the present invention is to provide a current sensing system for detecting faults such as leakage in multiple conductors, having a simple layout, accuracy, and mechanical robustness.

[0009] In one aspect, the present invention provides a current sensing system for fault detection, including a sensing element for detecting a magnetic field and a magnetic core having an opening. The magnetic core is arranged to enclose at least two target conductors, and the sensing element is configured to detect a component of the superposition of magnetic fields generated by at least two currents carried by the respective target conductors passing through the opening. The sensing element is mechanically decoupled from the magnetic core. Further, the sensing element is configured to provide an output signal indicating the superposition of the magnetic fields.

[0010] Advantages of embodiments of the present invention are that a compact, accurate, and fast monitoring device for a multiphase electrical system can be provided. Further advantages are that robustness is improved, as well as thermal drift and lifetime drift are improved.

[0011] In some embodiments, the sensing element is at least 0.5 mm away from the magnetic core.

[0012] Advantages of embodiments of the present invention are that a mechanically robust system can be obtained by avoiding contact between the sensing element or a sensor package including the sensing element and the core.

[0013] In some embodiments, the system further includes a substrate that includes at least two target conductors as conductive traces.

[0014] Advantages of embodiments of the present invention are that the target conductors can be provided in a single PCB, thus facilitating setup and alignment.

[0015] In some embodiments, the width-to-thickness ratio of the traces is at least 10, for example at least 100.

[0016] Advantages of embodiments of the present invention are that a very compact system can be provided.

[0017] In particular, the conductive traces are stacked on top of each other in the substrate.

[0018] Advantages of embodiments of the present invention are that the conversion factor is low. The traces can be embedded in the substrate.

[0019] In some embodiments, the first trace in the stack is located closest to the sensing element, where the second trace is the stacked conductive trace in the stack such that the first trace is present between the second trace and the sensing element. The first current-to-magnetic field conversion factor from the first trace and the second current-to-magnetic field conversion factor from the second trace differ by less than 5%, or less than 2%, or less than 1%.

[0020] Advantages of embodiments of the present invention are that accurate fault detection can be achieved. Further advantages are that in embodiments where the superposition is 0, faults can be detected more reliably due to the smaller conversion factor.

[0021] In certain embodiments, a sensing element is provided on a sensor on a substrate including at least two target conductors. For example, the sensor may be connected to a substrate containing or embedding traces.

[0022] An advantage is that a highly compact device can be obtained.

[0023] In some embodiments, at least one target conductor forms a loop such that the current of the conductor is enclosed by the magnetic core at least twice.

[0024] An advantage of embodiments of the present invention is a lower conversion factor. The traces may be embedded in the substrate.

[0025] In some embodiments, the number of conductors is 2 or greater, for example between 3 and 5.

[0026] An advantage of embodiments of the present invention is that ground faults in polyphase currents can be detected.

[0027] In some embodiments, the sensing element is provided on a planar sensor substrate including at least one maximum dimension. At least one maximum dimension of the sensor substrate is less than the width of the opening of the yoke.

[0028] An advantage is that the system has more compact components. A further advantage is that the system has lower sensitivity to mechanical displacement.

[0029] In some embodiments, the sensing element is sensitive to the component of the magnetic field in one direction.

[0030] An advantage of embodiments of the present invention is that no magnetic concentrator is required, thus reducing crosstalk from the target conductors.

[0031] In some embodiments, the sensing element is provided on a sensor substrate including at least one planar surface on the side, wherein the magnetic sensing element includes a maximum sensitivity axis parallel to the plane of the maximum surface of the sensor substrate, and wherein the opening is provided on the magnetic core such that the magnetic field across the opening is parallel to the maximum sensitivity axis of the sensing element.

[0032] An advantage is that the components are simple because the sensor including the sensing element can be positioned next to the opening.

[0033] In some embodiments, the sensing element is provided on a planar sensor substrate including at least one maximum surface, wherein the magnetic sensing element includes a maximum sensitivity axis perpendicular to the plane of the maximum surface of the sensor substrate. The opening is provided on the magnetic core such that the magnetic field across the opening is parallel to the maximum sensitivity axis of at least one sensing element.

[0034] An advantage is that the detected signal is higher compared to other arrangements. The signal-to-noise ratio can also be higher.

[0035] In some embodiments, the system further includes processing circuitry configured to detect a fault based on the superimposed signal.

[0036] An advantage of embodiments of the present invention is that the accuracy can be adjusted by programming different conditions for fault detection.

[0037] Specifically, the processing circuitry is configured to detect a fault when a field exceeding a threshold is detected.

[0038] An advantage is that a fault can be detected if the sum is different from 0 within the threshold, because the sum of the fields in a balanced system will be zero.

[0039] Specific and preferred aspects of the present invention are set forth in the appended independent and dependent claims. Features from the dependent claims may be combined appropriately with the features of the independent claims and with the features of other dependent claims, not only as explicitly set forth in the claims.

[0040] These and other aspects of the present invention will be apparent from and elucidated with reference to the (one or more) embodiments described hereinafter. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] Figure 1 is a cross-sectional view of a current sensing system according to an embodiment of the present invention, the current sensing system having a stacked magnetic core enclosing conductive traces on a PCB and a sensor having a sensing element that detects a magnetic field through an opening in the core.

[0042] Figure 2 is a cross-sectional view of a current sensing system having a magnetic core and a sensor according to an embodiment of the present invention, the sensor having a sensing element that detects a vertical magnetic field component through an opening adjacent to a stack of conductive traces on a PCB.

[0043] FIG. 3 shows a perspective view of two magnetic cores having different opening configurations and different relative positions of the openings with respect to a target conductor.

[0044] These drawings are only schematic and non-limiting. In the drawings, for illustrative purposes, the size of some of the elements may be exaggerated and not drawn to scale.

[0045] Any reference signs in the claims shall not be construed as limiting the scope.

[0046] In different drawings, the same reference signs refer to the same or similar elements. DETAILED DESCRIPTION

[0047] The present invention will be described with respect to specific embodiments and with reference to certain drawings, but the invention is not limited thereto and is only defined by the claims. The dimensions and relative dimensions do not correspond to the actual reductions in the practice of the invention.

[0048] Furthermore, the terms first, second, etc. in the description and claims are used to distinguish between similar elements and are not necessarily used to describe an order in time, space, ranking, or any other manner. It should be understood that the terms so used are interchangeable where appropriate, and the embodiments of the invention described herein are capable of operating in an order different from the order described or illustrated herein.

[0049] In addition, the terms top, bottom, etc. in the description and claims are used for descriptive purposes and are not necessarily used to describe relative position. It should be understood that the terms so used are interchangeable where appropriate, and the embodiments of the invention described herein are capable of operating in an orientation different from the orientation described or illustrated herein.

[0050] It should be noted that the term "comprising" used in the claims should not be construed as being limited to the means listed thereafter; it does not exclude other elements or steps. Thus, this term should be interpreted as specifying the presence of the stated features, integers, steps, or components as mentioned, but not excluding the presence or addition of one or more other features, integers, steps, or components, or groups thereof. Accordingly, the term "comprising" encompasses both the case where only the stated features are present and the case where these features and one or more other features are present. Thus, the scope of the expression "an apparatus comprising devices A and B" should not be construed as being limited to an apparatus consisting only of components A and B. This means that for the purposes of the present invention, the only relevant components of the apparatus are A and B.

[0051] References throughout this specification to "one embodiment" or "an embodiment" mean that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment of the invention. Thus, the appearances of the phrases "in one embodiment" or "in an embodiment" throughout this specification are not necessarily all referring to the same embodiment, but may refer to different embodiments. Furthermore, in one or more embodiments, as will be apparent to those of ordinary skill in the art through the present disclosure, the particular features, structures, or characteristics may be combined in any suitable manner.

[0052] Similarly, it should be appreciated that in the description of the exemplary embodiments of the present invention, for the purpose of streamlining the present disclosure and facilitating the understanding of one or more of the various inventive aspects, the various features of the present invention are sometimes grouped together in a single embodiment, drawing, or description thereof. However, this method of the present disclosure should not be construed as reflecting an intention that the claimed invention requires more features than are expressly recited in each claim. On the contrary, as reflected by the appended claims, the inventive aspects lie in less than all of the features of a single foregoing disclosed embodiment. Thus, the claims appended to the specific embodiments are hereby expressly incorporated into this specific embodiment, where each claim by itself represents a separate embodiment of the present invention.

[0053] In addition, although some of the embodiments described herein include some features included in other embodiments but not other features included in other embodiments, it will be understood by those skilled in the art that combinations of features of different embodiments are intended to fall within the scope of the present invention and form different embodiments. For example, in the appended claims, any of the claimed embodiments can be used in any combination.

[0054] Numerous specific details are set forth in the description provided herein. It should be understood, however, that embodiments of the present invention may be practiced without these specific details. In other instances, well-known methods, structures, and techniques have not been shown in detail so as not to obscure the understanding of this description.

[0055] The following are provided separately to assist in the understanding of the present invention.

[0056] When "trace" is mentioned in an embodiment of the present invention, it refers to a type of conductor characterized by its shape. Specifically, a trace is a conductive metal sheet that carries an electrical signal. Generally, a conductor disposed on a substrate and carrying a signal in a plane parallel to the surface of the substrate is commonly referred to as a trace. This is the case for a particular printed circuit board (PCB). As shown below, a trace is typically a flat conductor having a first dimension through which a signal is transmitted between a source and a sink, a second dimension is the width, and a third dimension is the thickness. In a trace, the thickness is much lower than the width.

[0057] The present invention relates to current sensing that uses devices designed to monitor current for the purpose of identifying abnormal conditions or faults. The system includes components capable of detecting the magnetic fields generated by the current and interpreting these magnetic fields to identify potential faults.

[0058] To detect current leakage, specialized circuits such as residual current devices (RDCs), including ground fault circuit interrupters (GFCIs), can be used. These circuits typically disconnect electrical power if there is a loss to ground within 1 / 40 of a second or even faster. Existing RDCs include a coil wound around a core, the coil wound around the core having two conductors which, if unbalanced, generate a magnetic flux on the core, causing a current that can be detected. The detected current implies an imbalance in the current between the conductors, thus indicating leakage.

[0059] The present invention provides a simplified and robust current sensing system for fault detection that can be used as a circuit breaker, power supply unit, or any other electrical system that requires monitoring of current for safety or operational integrity. For example, the present invention can be implemented as an RDC, such as a GFCI. These devices include sensors that generate a readable signal when an electromagnetic field is detected. In some embodiments, for example, the system can be implemented such that an electromagnetic field is generated when a fault (e.g., leakage) occurs between a plurality of conductors herein referred to as "target conductors" or TCs. In the absence of leakage, the TCs generate a zero (null) electromagnetic field.

[0060] The present invention provides magnetic field detection. The TCs are arranged such that they generate a predetermined magnetic field by superposition. The superposition of the magnetic fields generated by the TCs is detected by a magnetic sensing element that can be disposed on the sensor. The superposed field is detected and can be compared with a desired signal (e.g., an expected value of the signal). The measurement of the superposed field (especially the result of the comparison with a predetermined value or signal) is used to detect faults, such as leakage (e.g., caused by a ground fault).

[0061] As used herein, the term "sensing element for detecting a magnetic field" refers to a component or device within a current sensing system that is specifically designed to sense or measure a magnetic field. The element converts magnetic field information into an electrical signal that can be further processed. Examples of specific embodiments of a sensing element for detecting a magnetic field include Hall effect elements, magnetoresistive elements, inductive coil elements, and fluxgate elements.

[0062] In cases where "sensor" is mentioned in embodiments of the present invention, reference is made to a die, or "sensor substrate", including the sensing element and signal connections, commonly referred to as "leads". The die can be a semiconductor die and can be processed as an integrated circuit (IC). In some embodiments, the (one or more) sensing elements are disposed on the active surface of the sensor substrate or within the active surface of the sensor substrate. The sensor substrate and the sensing element can be molded, thereby forming a sensor package that can be connected to a substrate such as a PCB.

[0063] In some embodiments of the present invention, the substrate including the TC is also the substrate to which the sensor package is connected, thereby advantageously providing a compact current sensing system.

[0064] The TC can carry different types of current, such as DC current, or alternating current, such as polyphase current. A balanced 3-phase current with a 120-degree phase shift is an example of such polyphase current. In a balanced 3-phase system (120-degree phase shift), the sum of the currents should be zero, which is the expected signal. Thus, in a 3-phase system, the superposition is checked not to exceed a predetermined value. However, the present invention can be applied to other alternating currents (e.g., 2-phase current). In a two-phase, 90-degree phase shift system, the superposition field generates a sinusoidal signal. Deviations from such behavior are picked up by the magnetic sensor from the change in the magnetic field. Other currents can be applied to the TC, and the TC generates a field through superposition.

[0065] The magnetic field around the TC is captured by a magnetic core, which is commonly referred to as a "yoke". The magnetic core is arranged such that it surrounds or encloses two or more conductors through which current flows. This configuration allows the magnetic fields from separate TCs to interact within the opening of the core. The conductors can be wound around the core.

[0066] Examples of specific embodiments of the magnetic core with an opening can include a toroidal core, an E-shaped core, or a C-shaped core, etc. The terms "magnetic core" or "yoke" will be used interchangeably throughout the specification and claims. The yoke in the embodiments of the present invention encloses the TC conductors. However, the yoke has an opening, so it does not surround the TC 360 degrees. In other words, the magnetic core is made of a magnetic material shaped to have a gap or hole through which magnetic flux can leave the yoke, pass through a different material (such as air), and enter the yoke again. The magnetic core is used to concentrate and direct the magnetic field generated by the current in the target conductor.

[0067] The opening provides a complete separation or gap that breaks the field loop. The magnetic field is forced to pass through the opening to close the loop. The magnetic sensing element senses the magnetic field through this opening. The opening can cover 25% or less of the outer perimeter of the yoke. For example, if the yoke is square, one of the sides of the square is removed, leaving a square "u" shape. The opening can cover, for example, between 0.5% and 20% of the perimeter, such as between 1% and 10% of the perimeter.

[0068] In an embodiment of the present invention, the sensing element in the system of the present invention is mechanically decoupled from the yoke. For example, the sensor including the sensing element does not mechanically contact the yoke (e.g., there is no mechanical contact between the sensor package and the yoke). This means that the sensing element, or the sensor on which the sensing element is mounted, is not rigidly attached or directly mechanically connected to the physical arrangement of the magnetic core, which allows for independent movement or vibration without being directly mechanically affected by the core. Examples of specific embodiments of mechanical decoupling include mounting the sensor on a separate substrate. Non-rigid couplings can be used, such as adhesives with damping properties, spacers adapted to provide non-rigid coupling, etc. The field is sensed by the sensing element through an opening, but the sensing element (or sensor) is not attached to the yoke around the opening or is not generally attached to the yoke. Although this may potentially reduce the positioning accuracy, it has been found that the mechanical robustness of the device is improved. There is no stress caused by an attachment layer, etc. between the yoke and the sensor, and the thermal stress is also reduced. In other words, there is a gap such as an air gap between the sensing element (e.g., sensor) and the yoke, and both the sensor and the yoke are decoupled from each other. In an embodiment, there may be an air gap of at least 0.5 mm (e.g., at least 1 mm) between the sensing element (e.g., the sensor including the sensing element) and the magnetic core.

[0069] In some embodiments, the sensing element is mounted on a circuit substrate (such as a PCB, etc.), for example, the sensor including the sensing element is connected to the substrate. The substrate may also include a TC. In this case, the substrate may be a base material on which conductive paths or lines (referred to as traces) are formed or deposited. These traces serve as target conductors for the current sensing system. Examples of specific embodiments of the substrate with conductive traces include printed circuit boards (PCBs), flexible circuits, or ceramic substrates with metal traces. The PCB may also include additional traces for sensing signal processing and / or output. The sensor substrate may be directly disposed on the substrate including the traces, for example, it may be directly mounted on the substrate (such as a PCB) and encapsulated, or even integrated inside the substrate of the TC. However, in the embodiment shown in the figure, the sensor substrate is shown as being separately encapsulated and then connected to the substrate including the TC.

[0070] In some embodiments, the TC is provided as a stack of traces in the substrate. The TC is stacked on top of each other, which indicates that multiple traces are vertically layered one above the other with respect to the conductive traces, rather than being arranged side by side in the same plane. Examples of specific embodiments of the stacked conductive traces include multi-layer PCBs where the traces are present on different layers of the board. Since the sensor and the traces are disposed on a single substrate (such as a PCB substrate), a very compact current sensing system is obtained.

[0071] The yoke partially encloses the substrate. The current through each TC generates a corresponding field, and these fields are combined by the yoke into a superimposed field that is monitored by the sensor. Although the presence of traces with relatively high currents may have a thermal impact on the electronics of the sensor, the system is generally highly stable since there is no contact between the sensor and the yoke, and thus thermal stress is negligible.

[0072] In a first aspect, the present invention relates to a current sensing system for monitoring an electrical system having a plurality of phases, such as a three-phase system.

[0073] A current sensing system for fault detection includes a sensing element for detecting a magnetic field and a magnetic core having an opening. The magnetic core is designed to enclose at least two TCs, and the sensing element is configured to detect a component of the superimposed magnetic field generated by the current carried by the respective target conductors through the opening. The sensing element is mechanically decoupled from the magnetic core. For example, the sensing element may be mounted on a sensor that is mechanically decoupled from the magnetic core, thereby providing an output signal indicative of the superimposed magnetic field. "Mechanically decoupled" means that the sensor is separated from the core and there is no direct contact between the two. For example, mechanical decoupling allows relative movement between the sensing element and the yoke without affecting or straining each other. Any mechanical link between the sensing element and the yoke provides damping of the movement between them.

[0074] Generally, the sensing element (or package, or PCB containing the sensing element) is mechanically decoupled from the yoke in the vicinity of the sensing element (e.g., not in direct contact with the yoke), such that vibrations, shocks, etc. are damped before any transmission between the sensing element and the yoke occurs.

[0075] The present invention provides a compact, accurate, and fast monitoring device for a multi-phase electrical system (e.g., for detecting faults such as ground faults). Specifically, the present invention relates to a device capable of detecting ground faults in a multi-phase electrical system. The current sensing system includes a magnetic sensor that is arranged to detect a field through an opening in a magnetic core configured to enclose a plurality of TCs.

[0076] In one embodiment, the sensing element is positioned at least 0.5 mm from the magnetic core to prevent mechanical stress and potential damage. The system may also include a substrate having conductive traces that act as target conductors, which simplifies the system design and components. The width-to-thickness ratio of these traces is at least 10, or even at least 100, thereby enhancing the magnetic field detection sensitivity. These conductive traces may be stacked on top of each other to achieve a compact design, and at the location where the traces are stacked, the conversion factor is lower. The traces may be embedded in the substrate.

[0077] The sensor may include a sensing element for providing sensing of a magnetic field at a single location. The sensing element may be any one of a Hall element, a magnetoresistive element, etc. The sensor may also include an integrated circuit (IC) encapsulated by a molding compound. The IC may include an active portion having the sensing element. The package may include conductive vias or pins for connection to a substrate and provide an output signal representing the value of the detected magnetic field. The IC may have a maximum dimension (e.g., length) that may be less than the width of the opening in the magnetic core. The sensor may be sensitive to field components parallel or perpendicular to the main (largest) side of the package, thereby providing sensing of either component of the field at that single point. Detecting the field at a single location allows for a simple configuration and also allows for a very compact design using a small sensor substrate (e.g., a small IC), as well as cost-effective components since only one sensing element may be required.

[0078] The system may include one or more magnetic concentrators (MCs). These elements redirect the magnetic field. The concentrator allows the use of a sensing element having maximum sensitivity in a given direction by converting the field component into a different component for use with components in different directions. In some embodiments, the output signal is converted by the magnetic concentrator based on signals from sensing elements that detect field components at a single location. In some embodiments, the concentrator is a piece of magnetic material integrated in the sensor substrate. The MCs are referred to as integrated magnetic concentrators (IMCs), and they may be integrated in the IC.

[0079] The system may be adapted to detect faults based on superimposed signals. For example, a processing circuit may receive signals generated by the sensing elements. The processing circuit processes the output signals from the sensing elements (the output signals representing the magnetic field from a combination of multiple conductors) to identify deviations or anomalies indicative of a fault condition. Examples of specific embodiments of the processing circuit include a microcontroller, a digital signal processor (DSP), or a custom integrated circuit designed for fault analysis. The processing circuit may identify a fault when the measured magnetic field, as represented by the superimposed signal, exceeds a predefined limit or threshold. The threshold is set to distinguish normal operating conditions from fault conditions. Examples of specific embodiments of fault detection include overcurrent protection, short-circuit detection, or ground fault interruption. The processing circuit may be external, integrated with the sensor, disposed on the same printed circuit board (PCB) as the sensor, and connected to the same PCB as the sensor by wires, etc.

[0080] Figure 1Shows a cross-sectional view of a current sensing system 100 according to an embodiment of the present invention, the current sensing system 100 including a core and a sensor. A magnetic core 102 with an opening 103 encloses a stack of conductive traces 201, 202 within a printed circuit board (PCB). A sensor 101 with a sensing element 105 is strategically placed above the stack, and the opening in the magnetic core allows a magnetic field to pass through, where it is detected by the sensing element. In some embodiments, the sensor does not have an IMC, which reduces crosstalk from the target conductor and simplifies the components. The yoke can be a C-shaped core or an R-shaped shield, which differ in their shapes, as explained below with reference to FIG. 3.

[0081] The stack of all traces can be made in the same substrate 200. The distance between the traces can be equal to or less than the height H of the substrate 200. In some embodiments, the traces (e.g., all traces) are embedded in the PCB (or generally, in the substrate 200 that carries the traces). The highest and lowest traces in the stack refer to the stack pair that sandwiches the rest of the traces. The outer surfaces of the highest and lowest traces are the surfaces that do not face the rest of the traces in the stack. Under these definitions, in some embodiments of the present invention, the distance N between the outer surfaces of the highest and lowest traces can be lower than the height H of the substrate 200 in which the traces are embedded. A very compact design can be provided. In some embodiments, the trace closest to the sensor is embedded, so that the sensor can be disposed on the same substrate 200 without direct contact with any traces.

[0082] The sensor can be disposed on the substrate. For example, the sensor can be a packaged sensor with pins connected to the substrate. The package protects the IC and optionally any sensing elements therein.

[0083] The IC of the sensor can be smaller than the width of the opening, such that alignment is less sensitive to the exact position of the sensor, because when the opening is larger than the sensor, the detected field changes in a smoother manner. In some embodiments, the package of the sensor can have the same size as or be smaller than the opening.

[0084] Hereinafter, directions are defined based on the direction Y of the current, the direction Z of the TC stack, and the horizontal direction X perpendicular to the two first directions.

[0085] The sensor is sensitive to fields in a direction parallel to its surface or parallel component B 11 of the direction. The sensor is oriented relative to the opening such that the parallel component is in the horizontal direction X in the direction of the width of the opening, and thus it is consistent with the horizontal component Bx of the detected field.

[0086] The sensing element is preferably sensitive to the component of the magnetic field in one direction. The sensing element is designed to primarily detect or measure the magnetic field strength along a specific spatial axis or orientation. This property allows for targeted sensing of the magnetic field aligned with the specified direction. Examples of specific embodiments of a directionally sensitive sensing element include magnetoresistance-based elements such as anisotropic magnetoresistance (AMR) sensors, tunneling magnetoresistance (TMR), or Hall effect sensors with a defined sensing axis. Preferably, the maximum sensitivity axis can be defined as the direction in which the sensing element has the highest responsiveness or gain for detecting the magnetic field. In an embodiment, the system is configured such that the sensing element has its maximum sensitivity axis in the direction X of the maximum field through the opening (B 11 ). In the case where the sensing element includes a Hall element, it can include at least one (e.g., only one) vertical Hall element and / or a combination of an IMC and at least one (e.g., only one) horizontal Hall element.

[0087] In Figure 1 a particular case, the sensor is positioned through the opening, e.g., next to the opening. In some embodiments, the symmetric plane of the core passes through the sensor, in other words, the sensor is at the center of the core and intersects the central plane of the opening. The inner surface of the core facing the enclosed TC at the side of the opening can form a plane passing through the opening. The plane can be located at a predetermined distance from the sensing element, e.g., at least 0.5 mm, e.g., at least 1 mm, so that the sensor (e.g., the package) does not contact the yoke. The sensor can be provided on a substrate, such as a PCB, which includes the TC internally. Thus, the sensor can overlap with the TC. The TC can be traces stacked in the vertical direction Z, which is perpendicular to both the horizontal direction X and the direction Y of the current. The TC is at least 2, but it can be 3, 4, 5, or more. In other words, the number of conductors specifies the number of separate conductive paths or traces enclosed by the magnetic core and which are part of the current sensing system, and examples of specific embodiments of this term include systems with 2, 3, 4, or 5 separate conductive traces or wires, which are monitored by the sensing element. This makes the system suitable for different electrical configurations.

[0088] One or more TCs can include loops such that the current of the conductor is enclosed by the magnetic core at least twice. A loop in this context refers to the physical layout of at least one target conductor such that its path forms one or more loops, causing the magnetic core to enclose the current path multiple times. This configuration can enhance the interaction of the magnetic field with the core. This allows for improved fault detection sensitivity. Examples of specific embodiments of a conductor forming a loop can include a helical or coiled conductor or trace that passes through the opening of the core more than once.

[0089] In some embodiments, the substrate including the sensor and the TC is part of the sensing system.

[0090] The system can have a configuration including 2 conductors through a yoke. For example, the conductors can carry currents having phases, and the conductors can be grounded. When the currents are opposite, the sum of the currents is zero, and the superposition of the fields is also zero. The system can have a configuration including 3 conductors having 3 phases. For example, in a balanced system, the phases are adapted such that the current through the yoke is zero (and the superposed field is also zero). The system can have a configuration of 4 conductors, one of the 4 conductors being neutral and the other three conductors carrying alternating current having a predetermined phase. The system can have a configuration of 5 conductors, one of the 5 conductors being neutral, another conductor being grounded, and the other three conductors carrying alternating current having a predetermined phase. As explained earlier, the sum of the currents through the conductors having alternating current can be zero, and the currents in the neutral line and the ground connection (grounding) are also zero. In normal operation, the superposed field is zero, and in the case of an error, the superposition will result in a non-zero magnetic field exceeding a threshold.

[0091] As mentioned before, this is not the only possibility; the expected superposed signal can be non-zero, so the system can be adapted to compare the measured signal with an expected, predetermined signal (e.g., a known sinusoidal signal).

[0092] Currents can flow through traces in a substrate, each trace can carry approximately 30 A RMS (root mean square), which means that for the same power dissipation through the conductors, the alternating current through the traces would be equivalent to a DC current of 30 A. The present invention can detect a deviation of the sum of all phases of at least 30 mA, or at least 20 mA, or at least 10 mA. Depending on the type and accuracy of the sensor, a 30 mA difference between the traces causes a sufficient magnetic field detected by the sensor through the yoke, and an output signal of approximately 30 mV can be generated. These specific values are only indicative, and the present invention can use different values. The triggering of an action (such as the shutting off of the current through the TC) can take into account both the measured value and the period over which the reading is taken. For example, when a reading corresponding to 30 mA or 35 mA is obtained, the action can occur after a fraction of a second (e.g., one-third of a second), while during the measurement of a much higher current (e.g., 150 mA), the action can be executed after a much shorter time (e.g., 40 milliseconds).

[0093] As used herein, and unless otherwise specified, the term "current-to-magnetic field conversion factor" refers to the proportionality constant or coefficient that relates the current flowing through a conductor to the magnetic field it generates.

[0094] Surprisingly, it has been found that in embodiments of the present invention, the current-to-field conversion factors for each trace at the sensor location are very similar. For example, differences of less than 5%, 2%, or 1% in the conversion factors between two traces have been found, indicating a high similarity in how the current in these traces is converted into a magnetic field. In some embodiments, even when the traces are set at different distances from the sensor location, the differences exist only in the fourth decimal place of μT / mA (where μT indicates microtesla). This allows for precise fault detection. For example, in a 3-phase system, this means that the superposition of the magnetic fields will be close to 0. Specifically, in a balanced 3-phase system, the sum of the fields generated by the currents is zero. However, each individual current is not 0. If the current-to-field conversion factors at the sensor location are substantially equal, the superposition of the magnetic fields will produce a zero field. However, in cases where they are not substantially equal, the field produced by the superposition will not always be close to 0 and may in fact vary over time. As provided in some embodiments of the present invention, the advantage that the conversion factors are substantially equal within a few percentages (e.g., less than 5%) is that a simple threshold on the signal can be used to determine whether there is a fault at the output. Thus, the system can include a comparator with a simple configuration for detecting faults.

[0095] In some embodiments, the geometric centers of the stacked traces are close to each other in the Z direction, thereby improving the conversion factor. In some embodiments, the distance between the centers is equal to less than 5 times the thickness of the trace, such as 3 times the thickness of the trace, or even smaller. This advantageously improves the conversion factor and maintains a high signal for a relatively low current passing through the trace.

[0096] The following table shows the conversion factors for Hall elements sensitive to the component Bz in different cores (the C-shaped core and the so-called R-shaped core shown in Figure 3). For different layers with 2 loops, the conversion factors show very small differences. The results were obtained by simulation by sequentially passing current through each layer connected to the source while disconnecting the remaining currents from the source. Although these results were obtained by simulation, they can also be provided by measurement. Figure 2

[0097] Table I - Conversion Factors for the System of the Present Invention

[0098]

[0099] The following Table II shows the conversion factors for a sensing system using a Hall element in combination with IMC.

[0100] Table II - Conversion Factors for the System with IMC

[0101] ​

[0102] These results have been found for a so-called power PCB with a height between 3 mm and 5 mm and having four stacked traces. The traces of these PCBs can have such a geometry that the width of each trace is between 10 mm and 50 mm and the thickness is approximately 100 microns. For example, the thickness can be between 30 microns and 300 microns, or between 50 microns and 150 microns. The spacing between the traces can be between 50 microns and 500 microns, or between 250 microns and 350 microns, and can be, for example, approximately 300 microns.

[0103] However, the present invention is not limited to these specific values, and they can have a predetermined width-to-thickness ratio. This term refers to the proportional relationship between the horizontal extent (width) of the conductive trace and its vertical dimension (thickness). A width-to-thickness ratio of at least 10 indicates that the width is at least ten times the thickness. In embodiments of the present invention, the width-to-thickness ratio is at least 10, for example at least 20, for example at least 50, for example at least 100. Examples of specific embodiments of traces with a higher width-to-thickness ratio include flat, ribbed conductors or wide PCB traces with a minimum thickness.

[0104] The yoke acts not only as a pick-up device for the magnetic field but also serves to shield against interference from external stray fields. For example, a stray field of a few mT along x will generate a voltage of less than 100 mV at the output. Additional shielding can be added to reduce the effect. The crosstalk effect is limited. For example, a trace carrying 30 A at about 10 mm from the sensor will generate a signal of 1.31 mV. By compensating with a processor or microcontroller, these errors can be reduced to a negligible effect.

[0105] Although Figure 1 it is shown that the sensing element is sensitive to the component of the magnetic field in one direction in a plane parallel to the largest surface of the sensor substrate, this is not the only option. For example, the sensing element can be sensitive to the perpendicular component.

[0106] Figure 2 A different layout of the system 110 is shown. Specifically, the sensor 111 is inside the opening 113 of the yoke 112. In this case, the sensor is sensitive to the field B1 that vertically passes through the sensor. For example, for a packaged sensor, the field can vertically pass through the largest surface of the package. The vertical field follows the vertical direction Z, which is the direction of the width of the opening. Thus, the field passing through the opening is parallel to the direction to which the sensor is sensitive. In other words, the sensor is sensitive to the field component in the vertical direction, which is the direction of the opening of the yoke.

[0107] As described above, the sensor can be placed on a substrate, which can be shared with the TC. This means that the sensor including the sensing element can be directly mounted on the same substrate that includes the conductive traces serving as the target conductors. Examples of specific embodiments of this configuration include an integrated circuit or a sensor attached to the surface of a PCB. In some embodiments, the sensor substrate (e.g., an IC) including the sensing element can be directly fabricated on or embedded within the PCB including the traces.

[0108] The sensor can be connected on the outer surface of the substrate as described above. In an embodiment, the TC can be a trace that does not extend within an opening, so the leakage of the induced magnetic field can be negligible. Thus, in this case, the PCB extends from the inside of the yoke where the traces are provided to the opening where the sensor is provided and within the opening, so in this case, the sensor does not overlap with the stack of traces.

[0109] As shown in the figure, the opening 113 in the yoke is located on one side of the stack of conductive traces 211, 212. The PCB extends into and beyond the opening, where the sensor 111 and the sensing element 115 are mounted on the part of the PCB within the opening 113. This configuration allows the sensor to detect the vertical component of the magnetic field, which is aligned with the axis of maximum sensitivity of the sensing element 115. When the sensor is within the opening of the yoke, compared to other settings, the advantage is that the detected signal is higher. The signal-to-noise ratio can also be higher.

[0110] In some alternative embodiments, the sensor is offset relative to the symmetry plane of the core. For example, the sensor can be displaced relative to the central axis of the opening. In some embodiments, multiple TCs are symmetrically arranged relative to the symmetry plane of the core, as Figure 2 shown. Thus, in some embodiments, the TC is substantially centered relative to the core, but the sensor is not.

[0111] In some embodiments, the part of the yoke including the opening can be tapered to concentrate the field on or around the area where the sensor is placed. This tapered design can be used whether the sensor is within the opening (as in Figure 2 ) or outside and adjacent to the opening (as in Figure 1 ).

[0112] Figure 3 shows perspective views of two different embodiments of yokes 122, 132 that enclose substrates 220, 230 including multiple TCs. In both cases, the TCs are stacked in the Z direction, and the direction of the current through the TCs follows the direction Y.

[0113] In Figure 3aIn it, the yoke 122 is a C-shaped core, which has faces parallel to the main directions X, Y, Z, including the face with an opening. The opening width is less than 25% of the periphery of the yoke.

[0114] The opening is placed at the side of the substrate 220, and if there is a non-zero superimposed field, the non-zero superimposed field will pass through the opening following the vertical direction Z. The sensing element (partially shown at the opening) is located at the opening, and it can be offset from the central axis of the opening. As explained earlier, the sensing element can be connected to the substrate 220 (or integrated with the substrate 220, provided on the sensor substrate and directly packaged or encapsulated on the substrate, or provided as a separate sensor on the chip and connected to the substrate 220).

[0115] Figure 3b An alternative yoke 132 is shown, i.e., an R-shaped shield or R-shaped core, whose opening width is oriented in the X direction. The TC of the sensor and the substrate 230 can be centered on the central axis of the core and the central axis of the opening. The side arms of the yoke around the opening are tapered in a plane perpendicular to the Z direction.

[0116] The opening is configured at the top of the substrate, beside the sensing element (partially shown at the opening). The tapering of the yoke allows the concentration of the field across the opening in the horizontal X direction, so the superimposition of the fields in the yoke increases around the area where the sensor is placed, thereby improving the signal and the signal-to-noise ratio.

[0117] Alternatively, the R-shaped core type yoke 132 can be combined with the substrate 230 suitable for providing a sensing element within the opening of the yoke, and conversely, the substrate 230 can be combined with the C-shaped core type yoke 122, so as to combine the Figure 3a and Figure 3b substrate and yoke as applicable for specific applications.

[0118] In some embodiments, the distance between the outer edge of the trace and the inner edge of the magnetic core can be between 0.5 mm and 10 mm, for example, between 0.5 mm and 5 mm, for example, 1 mm. This achieves low loss in the set of superimposed fields within the magnetic material of the magnetic core.

[0119] In a further aspect of the present invention, the current sensing system includes processing circuitry configured to detect a fault based on a superimposed signal. The superimposed field may be predefined and used to detect faults such as ground faults. In a 3-phase system, the superimposition is checked not to exceed 0 by a predefined value. Even if the traces are set at different distances from the sensor location, the current-to-field conversion factor for each trace at the sensor location remains very close. When the field exceeds a threshold, the processing circuitry can detect the fault, which provides a straightforward method for fault detection. The system is designed to tolerate variations in sensor positioning and is capable of detecting faults with high sensitivity and accuracy, allowing for precise fault detection and accurate detection of, for example, ground faults in polyphase currents.

[0120] Despite potential heat dissipation issues in the substrate containing the PCB due to the TC being able to carry large currents, the system is thermally and mechanically robust due to the mechanical decoupling of the sensor and the core. A very high ratio of traces can result in a good current-to-field factor.

Claims

1. A current sensing system (100, 110) for fault detection, the current sensing system (100, 110) comprising a sensing element (105, 115) for detecting a magnetic field, a magnetic core (102) having an opening (103), and a substrate (200, 210) in which at least two target conductors (201, 202) are embedded, wherein: The magnetic core is arranged to enclose the at least two target conductors (201, 202), the sensing element is configured to detect a superimposed component of the magnetic field generated by at least two currents carried by the corresponding target conductors through the opening, the sensing element is mechanically decoupled from the magnetic core, and the sensing element is further configured to provide an output signal indicative of the superposition of the magnetic fields.

2. The system according to claim 1, wherein: The sensing element (105, 115) is at least 0.5 mm away from the magnetic core (102).

3. The system according to claim 2, wherein: The traces may have a width to thickness ratio of at least 10, such as at least 100.

4. The system according to claim 1, wherein: The conductive traces are stacked on top of each other.

5. The system according to claim 4, wherein: The first trace is a conductive trace of the stack located closest to the sensing element; Wherein the second trace is a stacked conductive trace located in a stack such that the first trace is present between the second trace and the sensing element, wherein a first current-to-magnetic field conversion factor from the first trace differs from a second current-to-magnetic field conversion factor from the second trace by less than 5%, or less than 2%, or less than 1%.

6. The system according to claim 1, wherein: The sensing element is disposed on a sensor on the substrate including the at least two target conductors.

7. The system according to claim 1, wherein: At least one target conductor forms a loop such that the current of the conductor is confined at least twice by the magnetic core.

8. The system according to claim 1, wherein: The number of conductors (201, 202) is between three and five.

9. The system according to claim 1, wherein: The sensing element (105) is disposed on a planar sensor substrate (104) comprising at least one maximum dimension, wherein the at least one maximum dimension of the sensor substrate is smaller than a width (w) of the opening.

10. The system according to claim 1, wherein: The sensing element is sensitive to a component of the magnetic field in one direction.

11. The system according to claim 10, wherein: The sensing element (105) is arranged on a sensor substrate (104) comprising at least one planar surface on a side, wherein the magnetic sensing element comprises a maximum sensitivity axis parallel to the plane of the largest surface of the sensor substrate, wherein the opening is arranged on the magnetic core so that the magnetic field across the opening is parallel to the maximum sensitivity axis of the sensing element.

12. The system according to claim 10, wherein: The sensing element (115) is arranged on a planar sensor substrate (114) comprising at least one largest surface, wherein the magnetic sensing element comprises a maximum sensitivity axis perpendicular to the plane of the largest surface of the sensor substrate, wherein the opening is arranged on the magnetic core so that the magnetic field across the opening is parallel to the maximum sensitivity axis of the at least one sensing element.

13. The system of claim 1, further comprising a processing circuit configured to detect a fault based on the superimposed signal.

14. The system according to claim 13, wherein: The processing circuit is configured to detect a fault when a field exceeding a threshold is detected.

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