Electrical circuit for fault current detection in electric vehicle charging stations

Abstract

An electrical circuit for detecting a fault current in an electric vehicle charging station, the electrical circuit comprising a print substrate comprising at least two conductive tracks for carrying a charging current for charging and / or discharging an electric vehicle along the print substrate, the electrical circuit further comprising a fluxgate current sensor for detecting a fault current in the at least two conductive tracks, the fluxgate current sensor comprising a magnetic core having through holes disposed about the at least two conductive tracks passing through the through holes in the magnetic core.

Description

[Technical field]

[0001] The present invention relates generally to an electrical circuit for detecting fault currents in an electric vehicle charging station. [Background technology]

[0002] A Residual Current Device (RCD) is a protective device designed to interrupt an electrical circuit when a leakage current (i.e., fault current) is detected. The operation of an RCD relies on measuring the balance between the outflow current of the live conductors and the return current of the neutral conductor of an electrical circuit.

[0003] Additionally, a typical RCD relies on the transformer principle to detect the presence of a magnetic field. In a balanced electrical circuit, the magnetic fields generated by each conductor in a supply line cancel each other out as the sum of the currents becomes zero. However, when a fault current is present, the vector sum of all the currents in the supply line will not be zero, creating a detectable magnetic field around the supply line.

[0004] For safety reasons, RCDs are also installed in electric vehicle (EV) charging stations to protect users from potential safety hazards and property damage. Type A RCDs can detect AC faults, but have limited ability to detect fault currents with DC components. Furthermore, fault currents with DC components above a certain threshold current (e.g., 6mA) may impair the function of type A RCDs. Since EV charging can induce harmonics or DC residual currents even when charging with AC, an additional residual direct current detection device (RDC-DD) may be mandatory for EV charging stations using type A RCDs.

[0005] Such an RDC-DD is designed to detect DC faults above a certain minimum threshold current (e.g. 6mA) and can interrupt the circuit before the type A RCD is damaged. Alternatively, a type B RCD can be used which detects both AC and DC faults. However, this can be significantly more expensive compared to a type A RCD in combination with an RDC-DD.

[0006] A typical RDC-DD solution is installed inside the charging station housing with a dedicated type A RCD. Alternatively, the RCD can be installed inside the switchboard that supplies power to the charging station. The problem with current RDC-DD solutions is the extensive wiring required to install them in the charging station. Power conductors from the switchboard must connect to at least the charging station controller, the RDC-DD, and the EV charging socket. This wiring needs to be done on-site by trained professionals, which can significantly increase the installation costs. Another challenge is that current RDC-DD solutions have limited resolution, accuracy, linearity, and can have significant noise. Summary of the Invention

[0007] SUMMARY OF THE PRESENT EMBODIMENT An object of the present invention is to at least partially solve the above problems and issues by, among other things, providing an electrical circuit for detecting fault currents that reduces wiring in an electric vehicle charging station. [Means for solving the problem]

[0008] According to a first aspect of the invention, this object is achieved by an electric circuit for detecting a fault current in an electric vehicle charging station, the electric circuit comprising a print substrate comprising at least two conductive tracks for carrying a charging current for charging and / or discharging the electric vehicle along the print substrate, the electric circuit further comprising a fluxgate current sensor for detecting a fault current in the at least two conductive tracks, the fluxgate current sensor comprising a magnetic core having through holes arranged around the at least two conductive tracks passing through the through holes in the magnetic core.

[0009] In other words, the fluxgate current sensor is disposed around conductive tracks provided on a printed substrate. In the context of this application, the term "fault current" refers to an unintended and / or uncontrolled flow of current (e.g., residual current, leakage current, or short circuit current) through at least two conductive tracks that exceeds a certain threshold.

[0010] The at least two conductive tracks are provided on or in a print substrate of the electric vehicle charging station, for example as strips of conductive material contained in or on a surface of the print substrate. An electric charge can be passed along the at least two conductive tracks in the form of a charging current. The charging current can be supplied to an electric vehicle connected to the electric vehicle charging station. The charging current then flows along the conductive tracks to charge the electric vehicle. The charging current can be an alternating current (AC) or direct current (DC) supplied to the electric vehicle charging station by a power source (e.g., a local power grid, a power grid, a solar panel installation, or an energy storage system). The charging current can also flow in the reverse direction (i.e., from the electric vehicle toward the power source), thereby discharging the electric vehicle along the at least two conductive tracks. The print substrate can be, but is not required to be, further configured to control one or more functions associated with the operation of the electric vehicle charging station (e.g., monitoring and / or controlling the charging process).

[0011] In addition to the at least two conductive tracks, a fluxgate current sensor is integrated on the print substrate to detect a fault current in the at least two conductive tracks. Furthermore, the fluxgate current sensor includes a magnetic core with a through hole. The cross section of the through hole can be preferably shaped as a substantially elliptical, stadium or rectangular shape. The fluxgate current sensor is then arranged on the print substrate such that the magnetic core is arranged around the at least two conductive tracks. In other words, the at least two conductive tracks pass through the through hole of the magnetic core. Thus, the fluxgate current sensor (particularly the magnetic core) can also be arranged around a portion of the print substrate surface that includes the at least two conductive tracks. The cross section of the through hole is shaped such that the distance between the print substrate and the magnetic core is substantially equal along the inner limit of the magnetic core. This allows the presence of a fault current to be detected by the fluxgate current sensor arranged around the at least two conductive tracks without reducing the reliability of detecting the fault current, since the magnetic core is arranged sufficiently close to the at least two conductive tracks to detect a change in the magnetic field due to the fault current. This has the advantage that the circuit can be made substantially compact and therefore only occupy a limited volume when installed in a charging station.

[0012] The fluxgate current sensor is configured to detect a fault current flowing along at least two conductive tracks (i.e., through a through hole in the magnetic core) based on a magnetic field bias in the magnetic core due to the fault current. Integrating the fluxgate current sensor into a print board allows the at least two conductive tracks to be integrated on or in the print board. Thus, the fault current can be detected in the at least two conductive tracks without additional wiring or connections. Thus, an advantage is that the number of wiring connections inside the electric vehicle charging station can be reduced. A further advantage is that the reliability and safety of the electric vehicle charging station can be improved by reducing the number of joints (e.g., soldered and screwed connections) in the wiring of the main current path. Thus, the joints are typically the points where defects, overheating, and fires can occur. A further advantage is that the installation costs of the electric vehicle charging station can be reduced. A further advantage is that the fluxgate current sensor has a relatively high linearity, high accuracy, high sensitivity, low drift, and low noise, and therefore the fault current can be detected more reliably.

[0013] According to one embodiment, the magnetic core may comprise a single piece of continuous magnetic material arranged around the through hole. In other words, the ends of the magnetic material may be joined to form an infinite loop arranged around the through hole. The magnetic material may preferably be a material (particularly a ferromagnetic material) having a substantially high magnetic permeability, for example, about 1.26E-02 H / m to about 1.88 H / m (preferably about 1.26E-01 H / m). A further advantage is that the magnetic field in the single piece of continuous magnetic material may substantially contain the magnetic field lines generated by the currents in at least two conductive tracks, thus allowing for more accurate detection of fault currents.

[0014] According to one embodiment, the portion of the print substrate may be configured to allow the fluxgate current sensor to be moved over the portion of the print substrate to a designated location. The portion of the print substrate may, for example, be narrow enough to allow the portion to pass through a through hole of the fluxgate current sensor, thereby allowing the fluxgate current sensor to be located at the designated location. This may reduce mechanical forces on the magnetic core during assembly and / or manufacturing of the electric circuit. A further advantage is that the operation of the fluxgate current sensor is more reliable, since the properties of the magnetic core (particularly the magnetic permeability) are not altered by mechanical forces during assembly or manufacturing.

[0015] According to an embodiment, the fluxgate current sensor may further comprise a protective housing surrounding at least a part of the magnetic core, configured to protect the magnetic core from stresses. The protective housing may cover the outer surface, the inner surface and / or at least one side surface of the magnetic core. The protective housing may be made of a substantially rigid material to protect the enclosed magnetic core from mechanical stresses (e.g., compression, elongation or bending). The protective housing may further comprise a filler made of an energy absorbing material (e.g., rubber or foam). The protective housing may further be configured to protect the magnetic core from thermal stresses (e.g., the protective housing made of a thermal insulating material and / or by a thermal insulating layer). A further advantage is that the operation of the fluxgate current sensor is more reliable, since the properties of the magnetic core (in particular the magnetic permeability) do not change due to pressures such as changes in the ambient temperature. A further advantage is that the protective housing may electrically insulate the magnetic core from the at least two conductive tracks that it is surrounded by, allowing the fluxgate current sensor to be substantially compactly integrated on a printed circuit board.

[0016] According to one embodiment, the fluxgate current sensor and the print substrate may comprise at least one mounting means for mounting the fluxgate current sensor to the print substrate. The fluxgate current sensor may thus be mounted (particularly at a specified location) on the print substrate. The at least one mounting means of the fluxgate current sensor may preferably be included within the protective housing (e.g. at both ends of the protective housing, on an inner surface of the protective housing and / or along mounting legs extending from the protective housing). The print substrate may comprise at least one corresponding mounting means configured to receive the at least one mounting means of the fluxgate current sensor. The mounting means fix the position of the magnetic core relative to the conductor, allowing efficient and reproducible measurement of the fault current.

[0017] According to an embodiment, the fluxgate current sensor may further comprise at least two excitation windings wound around the magnetic core. In other words, the at least two excitation windings may form a coil around the magnetic core. Preferably, the at least two excitation windings are interleaved such that the at least two windings are consecutive to each other in a regular pattern. The at least two excitation windings may be configured to pass an excitation signal (e.g., a voltage signal or a current signal) so that the magnetic core is driven into or out of saturation.

[0018] According to an embodiment, the fluxgate current sensor may further comprise a magnetic shield partially surrounding the magnetic core and the at least two excitation windings, configured to distribute the magnetic field generated by the current in the at least two conductive tracks substantially uniformly in the magnetic core. The magnetic shield may be disposed around an outer surface, an inner surface, and / or at least one side surface of the magnetic core. By partially surrounding the magnetic core, magnetic short circuits are prevented. In that way, the detected magnetic field in the magnetic core generated by the outgoing and return charging currents in the at least two conductive tracks may be substantially zero in the absence of fault currents, especially when the at least two conductive tracks are substantially asymmetrically distributed in the through-hole of the fluxgate current sensor. The magnetic shield may also reduce magnetic interference of other electrical components included on the printed circuit board and / or in the electric vehicle charging station.

[0019] According to an embodiment, the fluxgate current sensor may further comprise a drive circuit configured to alternately drive one of the at least two excitation windings with excitation voltages of opposite polarity and substantially equal magnitude. The drive circuit may include a plurality of electronic components configured to operate the fluxgate current sensor, for example, inter alia, by generating an excitation signal in the at least two excitation windings and measuring a response signal. The excitation signal may preferably be a square wave voltage signal. The excitation voltage may be applied to a first excitation winding, thereby driving the magnetic core into saturation. When a saturation point is reached, the excitation voltage may be switched from the first excitation winding to a second excitation winding. The second excitation winding may preferably be connected to the drive circuit in parallel and opposite polarity to the first excitation winding (i.e., anti-parallel to the first excitation winding). Thus, the fluxgate current sensor may be driven by a substantially symmetrical excitation signal, which may reduce measurement errors of the fluxgate current sensor.

[0020] According to one embodiment, the drive circuit is further configured to generate an output signal based on the presence of a fault current in the at least two conductive tracks. The drive circuit can generate the output signal, for example, when the fluxgate current sensor detects a fault current flowing through the at least two conductive tracks. The output signal can further trigger protection measures (e.g., interrupting the charging current). These protection measures can also, but do not have to, be performed by the electrical circuit.

[0021] According to one embodiment, the drive circuitry is further integrated on the printed substrate, such that the electronic components of the drive circuitry can be electrically interconnected and / or connected to the fluxgate current sensor by conductive tracks included in the printed substrate.

[0022] According to one embodiment, the electric circuit may further comprise a switch configured to interrupt the charging current in the at least two conductive tracks upon detecting a fault current in the at least two conductive tracks. The switch may be an electrically operated switch (e.g., a relay or a circuit breaker). The switch may interrupt the charging current based on an output signal received from the drive circuit.

[0023] According to a second aspect, the present invention relates to an electric vehicle charging station comprising an electric circuit for detecting a fault current according to the first aspect. Such an electric vehicle charging station may provide one or more of the advantages mentioned above. [Brief description of the drawings]

[0024] [Figure 1] FIG. 1 shows a schematic diagram of an electric vehicle charging station including an electrical circuit according to one embodiment of the present invention. [Diagram 2] FIG. 2 illustrates a perspective view of a preferred embodiment of an electrical circuit for detecting fault currents in the electric vehicle charging station of FIG. [Figure 3A]FIG. 3A shows a perspective view of a preferred embodiment of a fluxgate current sensor included in the electrical circuit of FIG. [Figure 3B] FIG. 3B shows a cross-sectional view of a preferred embodiment of a fluxgate current sensor included in the electrical circuit of FIG. [Figure 4A] FIG. 4A illustrates a time-varying excitation voltage that can drive a fluxgate current sensor and the resulting time-varying current response. [Figure 4B] FIG. 4B shows an example of a magnetic hysteresis loop relating the magnetic flux density B of a magnetic core to the surrounding magnetic field strength H. [Figure 4C] FIG. 4C shows the duty cycle of the excitation voltage with and without a fault current. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0025] FIG. 1 shows a schematic diagram 100 of an electric vehicle charging station 130 according to an exemplary embodiment connected to a power source 110 and an electric vehicle 140. The electric vehicle charging station 130, also called a charging station, is a device that charges the electric vehicle 140 with energy from the power source 110. Alternatively or supplementally, the charging station can discharge energy stored in the electric vehicle 140 to the power source 110. The electric vehicle 140 is a vehicle having an energy storage system (e.g., a battery). The electric vehicle can be, for example, a battery-powered electric vehicle, a hybrid electric vehicle, an electric bus, an electric truck, or an electric bike. The electric vehicle 140 can be charged through an electrical connection between the vehicle 140 and the charging station 130. Such a connection is established by a charging cable 131 or a current collector (not shown in FIG. 1), thereby providing conductive charging. Alternatively, the electric vehicle 140 can be charged wirelessly, i.e., through inductive charging (not shown in FIG. 1).

[0026] Charging current may be supplied to charging station 130 by power source 110 (e.g., a local power grid, a utility grid, a solar panel installation, or an energy storage system). The charging current may be alternating current (AC) or direct current (DC). The charging current may, but need not, be converted between AC and DC at least once along the path from power source 110 to electric vehicle 140. Charging current may also flow in the reverse direction (i.e., from electric vehicle 140 to power source 110), thereby discharging the electric vehicle. Vehicle-to-grid or vehicle-to-home systems are examples where charging current may flow in both directions.

[0027] The power source 110 can be connected to a power distribution board 120 (i.e., a system that can split the supply current into auxiliary circuits and provide protection measures for those circuits at the same time). The power distribution board can include an auxiliary circuit 121 that is connected to the charging station 130. The power distribution board 120 can further include a residual current device (e.g., a type A residual current device) to protect the auxiliary circuit that powers the charging station 130. Alternatively, the residual current device can be included in the charging station 130.

[0028] The charging station 130 includes an electrical circuit 200 for detecting fault currents and controlling the operation of the charging station. The electrical circuit 200 comprises a print board 210 including at least two conductive tracks 211, 212 for carrying a charging current along the print board 210. The electrical circuit 200 may comprise one or more connectors 213, 214 for establishing and maintaining electrical contact with, for example, the distribution board 120 and the electric vehicle 140. The first connector 213 may be configured to connect the at least two conductive tracks 211, 212 of the electrical circuit 200 to the auxiliary circuit 121 of the distribution board 120. The second connector 214 may be configured to connect the at least two conductive tracks 211, 212 of the electrical circuit 200 to the electric vehicle 140, for example via a socket 132 configured to receive a plug 133 of the charging cable 131.

[0029] The electric circuit 200 further comprises a fluxgate current sensor 220 for detecting fault currents in the at least two conductive tracks 211, 212. In particular, the electric circuit 200 can be configured to detect fault currents that may interfere with the functioning of the residual current device (e.g. fault currents with a DC component above a certain threshold current). Upon detecting such a fault current, the electric circuit 200 can activate protective measures, for example interrupting the charging current. These protective measures can be, but do not have to be, performed by the electric circuit 200. Alternatively, the protective measures can be performed by other components included in the charging station 130, by components included in the switchboard 120, or by the electric vehicle 140.

[0030] Print board 210 may not be limited to including electrical circuit 200 for detecting fault current. Print board 210 may further comprise components configured to, for example, among others, monitor and / or control the charging process, read or scan an RFID card, arrange for payment, display messages, or any other function related to the operation of the charging station. Alternatively, charging station 130 may include one or more additional print boards that comprise components for the operation of charging station 130.

[0031] 2 shows a perspective view of a preferred embodiment of an electrical circuit 200 for detecting fault currents in an electric vehicle charging station. A "fault current" refers to any unintended and / or uncontrolled flow of current (e.g., residual current, leakage current, or short circuit current) above a certain threshold through at least two conductive tracks. Fault currents can result, for example, from short circuits, unintended current interruptions, ground faults, or short circuits between one or more phases in a three-phase system, among others.

[0032] At least two conductive tracks 211, 212 are included in the print substrate 210 of the electric circuit 200. The conductive tracks 211, 212 may be strips of a conductive material, such as copper, deposited on an insulating surface of the print substrate 210, for example. Alternatively, the conductive tracks 211, 212 may be disposed within the print substrate 210 (for example between two insulating layers of a multi-layer print substrate). Thus, an electric charge (i.e., a charging current) can flow along these at least two conductive tracks 211, 212 (i.e., along the print substrate 210). The print substrate may preferably include more than two (in particular, three or four) conductive tracks 211, 212, depending on the type of current (i.e., AC or DC) and the type of electrical system (for example, single phase, three phase, or three phase with neutral).

[0033] To detect fault currents in the conductive tracks 211, 212, the electric circuit 200 comprises a fluxgate current sensor 220. The fluxgate current sensor 220 may preferably be a self-oscillating fluxgate current sensor, in particular an open-loop self-oscillating fluxgate current sensor. The fluxgate current sensor 220 comprises a magnetic core made of a magnetic material. The magnetic material may preferably be a material (in particular a ferromagnetic material) having a substantially high magnetic permeability, for example of about 1.26E-02 H / m to about 1.88 H / m (preferably about 1.26E-01 H / m). The magnetization of the magnetic material may preferably be characterized by a magnetic hysteresis with a relatively low saturation flux (i.e. the flux corresponding to the saturation point of the hysteresis loop). Preferably, the magnetic core may comprise a single piece of continuous magnetic material. In other words, the ends of the magnetic material may be joined to form an infinite loop. In this case, the magnetic core does not comprise separate pieces of magnetic material that require assembly to form the magnetic core. In doing so, the permeability of the magnetic core can be improved since there are no air gaps in the magnetic core material, and therefore the magnetic field within the magnetic core can contain more magnetic field lines generated by the currents in the conductive tracks 211, 212. Alternatively, the magnetic core can comprise separate pieces of magnetic material that require assembly to form the magnetic core.

[0034] The magnetic core further comprises a through hole around which the magnetic material is disposed. The magnetic core is further disposed around the conductive tracks 211, 212 (i.e. the conductive tracks pass through the through holes of the magnetic core). In high power applications (e.g. when charging and discharging electric vehicles), the conductive tracks 211, 212 may be substantially wider to accommodate large currents. The conductive tracks 211, 212 may be integrated alongside (e.g. parallel to) each other on the printed substrate, so that the conductive tracks 211, 212 may occupy a substantially wider or larger area on the printed substrate. To this end, the cross section of the through hole may preferably be shaped as a substantially ellipse, stadium or rectangle, such that the distance between the printed substrate 230 and the magnetic core of the fluxgate current sensor 220 is substantially equal along the inner limits of the magnetic core. In other words, the inner surface of the fluxgate current sensor 220 is disposed substantially equidistant from the portion of the printed substrate 230 surrounded by the fluxgate current sensor 220. This allows the presence of a fault current to be detected by the fluxgate current sensor 220 arranged around the conductive tracks 211, 212 without reducing the reliability of the detection of the fault current, since the magnetic core is placed close enough to the conductive tracks 211, 212 to reliably detect the change in the magnetic field due to the fault current. This has the further advantage that the circuit can be made more compact and therefore takes up less space in the charging station, compared to a through-hole shaped, for example, as a circle or a square.

[0035] Thus, the fluxgate current sensor 220 can be integrated onto the print substrate such that the conductive tracks 211, 212 pass through the through holes of the magnetic core (i.e. the magnetic core is disposed around the conductive tracks 211, 212). Because the conductive tracks 211, 212 are included in the print substrate 210, the fluxgate current sensor 220 (particularly the magnetic core) can also be disposed around a portion of the surface of the print substrate 210 (particularly the portion of the surface that includes the conductive tracks 211, 212).

[0036] The fluxgate current sensor 220 may further comprise a protective housing 223 that encloses at least a portion of the magnetic core and is configured to protect the magnetic core from stresses (i.e., forces acting on a unit area of ​​the magnetic core). The protective housing 223 may cover the outer surface, the inner surface, or at least one side surface of the magnetic core. The outer surface and the inner surface of the magnetic core refer to the surfaces of the magnetic core that face away from and towards the centerline of the magnetic core, respectively. The side surface of the magnetic core refers to a lateral surface that is substantially orthogonal to the outer surface and the inner surface of the magnetic core.

[0037] To protect the magnetic core from mechanical stresses (e.g., compression, stretching, or bending), the protective housing 223 can be made of a substantially rigid material (i.e., a material that cannot be substantially bent or forcibly deformed out of shape). Alternatively or supplementarily, the protective housing 223 can include an energy-absorbing material (i.e., a material that can elastically deform to absorb at least a portion of the mechanical stresses), such as, for example, rubber or foam. This energy-absorbing material can be included, for example, in the protective housing 223 as an additional inner layer between the outer layer of the housing and the magnetic core. Alternatively, the enclosed volume of the protective housing 223 can be filled, for example, with a filler material, thereby sealing the entire magnetic core. In addition to mechanical stresses, the protective housing 223 can protect the magnetic core from thermal stresses, for example, by including a layer or filler made of a thermal insulating material.

[0038] The print substrate 210 may further comprise a portion 230 configured to allow the fluxgate current sensor 220 to move over the portion to a designated position. The portion 230 may thus be configured to allow the fluxgate current sensor 220 to move substantially freely along the portion 230 toward a designated position. The designated position refers to a position on the print substrate 210 where the fluxgate current sensor 220 can detect fault currents in the conductive tracks 211, 212. To move the fluxgate current sensor 220 to this position, the portion 230 may be shaped according to the shape and dimensions of the through-holes in the magnetic core. The portion 230 of the print substrate may, for example, be narrow enough to pass through the through-holes of the fluxgate current sensor 220, thereby allowing the fluxgate current sensor to be located at the designated position. Thus, the print substrate 210 may accommodate the fluxgate current sensor 220 even when the magnetic core comprises a single piece of continuous magnetic material. Allowing substantially free movement of the fluxgate current sensor 220 can reduce mechanical forces on the fluxgate current sensor during manufacture or assembly of the electrical circuit, which may be undesirable as mechanical forces on the fluxgate current sensor may change the mechanical and / or magnetic properties of the magnetic core, thereby affecting the performance of the fluxgate current sensor 220.

[0039] The fluxgate current sensor 220 may further be attached to the print substrate 210 (particularly at a specified location). To this end, the fluxgate current sensor 220 and the print substrate 210 may comprise at least one attachment means. The at least one attachment means of the fluxgate current sensor 220 may preferably be included within the protective housing 223 (e.g., at both ends of the protective housing, on an inner surface of the protective housing, and / or along attachment legs 224, 225 extending from the protective housing 223). The attachment means may be, for example, among others, retainers, screws, bolts, rivets, grommets, plugs, pins, snap fasteners, snap fits, or any other attachment means known to those skilled in the art. The print substrate 210 may comprise at least one corresponding attachment means configured to receive the attachment means of the fluxgate current sensor 220. The attachment means may further provide a removable or permanent connection to the print substrate 210.

[0040] The electric circuit 200 may further comprise a switch 240 configured to interrupt the current in the conductive tracks 211, 212 upon detection of a fault current, in particular a fault current that may impede the functioning of the residual current device (e.g., a fault current with a DC component above a certain threshold current). Preferably, the switch may be triggered by a fault current exceeding an adjustable threshold current (e.g., 6 mA). The switch 240 may be an electrically operated switch, such as, for example, a relay, a circuit breaker, or any other switch known to a person skilled in the art. The switch 240 may preferably be included (i.e., integrated) on the print board 210. Alternatively, the switch 240 may be provided elsewhere in the charging station (i.e., not included on the print board 210). The switch 240 may be controlled by a signal received from the fluxgate current sensor 220 upon detection of the fault current.

[0041] It should be understood that Fig. 2 does not show all components of the print board 210. The print board 210 may further include multiple electronic components for controlling the operation of the charging station, for connecting the print board 210 to other components, for testing the correct and safe operation of the fluxgate sensor, and / or for detecting fault currents. Such electronic components may include, for example, resistors, connectors, transistors, capacitors, control units, comparators, multivibrators, operational amplifiers, switches, voltage sources, or current sources, among others. This has the added advantage of limiting the number of print boards in the charging station.

[0042] 3A and 3B show perspective and cross-sectional views, respectively, of a preferred embodiment of a fluxgate current sensor. In addition to being surrounded by a protective housing 223, the magnetic core 221 may further be partially surrounded by a magnetic shield 226. The magnetic shield 226 may be disposed around the outer surface, inner surface, at least one side, or any combination thereof of the magnetic core 221, so long as the magnetic shield 226 does not surround all sides of the magnetic core 221. The magnetic shield 226 may substantially uniformly distribute the magnetic field generated by the current flowing through the conductive track within the magnetic core 221. Thus, the detected magnetic field within the magnetic core 221 may be substantially zero in the absence of a fault current, especially if the conductive track is asymmetrically distributed within the through-hole 222 of the fluxgate current sensor 220. In other words, the magnetic shield 226 may help to nullify the detected magnetic field within the magnetic core 221 in the absence of a fault current. The detected magnetic field refers to the net magnetic field seen by the magnetic core. In the absence of a fault current, the detected magnetic field may be produced by at least one outflow charging current and a return charging current of substantially equal magnitude flowing in substantially opposite directions in at least two conductive tracks through the through holes 222 of the magnetic core 221. The magnetic shield 221 may also reduce magnetic interference of other electrical components contained on the printed circuit board or within the electric vehicle charging station.

[0043] The fluxgate current sensor 220 may comprise at least two excitation windings 227, 228 wound around the magnetic core 221. In other words, the excitation windings 227, 228 may form a coil wound around the magnetic core 221. Preferably, the at least two excitation windings 227, 228 are alternately arranged to follow and follow each other in a regular pattern. The excitation windings 227, 228 may be electrical conductors, such as insulated copper wires, configured to carry an excitation signal. The excitation signal may be any signal (e.g., a current signal or a voltage signal) that drives the magnetic core into or out of saturation. Preferably, a magnetic shield 226 may surround these excitation windings 227, 228 in addition to surrounding the magnetic core 221.

[0044] The excitation windings 227, 228 may further be connected to a drive circuit, for example via a connector 229. The drive circuit may include a number of electronic components, such as, for example, a comparator, a multivibrator, an operational amplifier, a switch, a voltage source, or a current source, among others. Preferably, the drive circuit may be integrated on a printed circuit board. In other words, the electronic components of the drive circuit may be electrically interconnected by conductive tracks on a printed circuit board in addition to being connected to the excitation windings 227, 228 via the connector 229. The drive circuit may be configured to operate the fluxgate current sensor 220, for example, by generating an excitation signal and measuring a response signal, among others. Preferably, the excitation signal may be an excitation voltage and the response signal may be a current flowing through the excitation windings 227, 228 as a result of the applied excitation voltage.

[0045] FIG. 4A shows an example of such a time-varying excitation voltage 401 and the resulting time-varying current response 402. The excitation voltage 401 generated by the electronic components of the drive circuit may preferably be a square wave signal. In other words, the excitation voltage 401 may be switched between predetermined minimum 403 and maximum 404 values ​​at a substantially constant frequency and with a substantially equal duration (i.e., duty cycle 405) at the minimum 403 and maximum 404 voltages. The minimum 403 and maximum 404 voltages may preferably be substantially equal in magnitude and opposite in polarity (e.g., −3.5V and 3.5V, respectively). Thus, the fluxgate current sensor may be driven by a substantially symmetric excitation voltage 401, which may reduce measurement errors of the fluxgate current sensor.

[0046] To obtain such substantially symmetric excitation voltages in a reliable manner, the excitation windings can be connected in parallel and with opposite polarity (i.e., anti-parallel) to the drive circuit. Thus, the drive circuit can apply the same voltage (e.g., 3.5V) alternately to the first and second excitation windings, and the polarity of the voltage can be reversed due to the anti-parallel connection of the excitation windings. In other words, a minimum 403 and a maximum 404 voltage can be applied to the first and second excitation windings, respectively, thereby subjecting the magnetic core of the flux-gate current sensor to a substantially symmetric square voltage wave.

[0047] An applied excitation voltage 401 may result in a time-varying current response 402 flowing through the excitation winding. This current response 402 may be measured by a driving circuit (e.g., by a shunt or precision resistor). The response current 402 may drive the magnetic core into saturation, since the core may be characterized by magnetic hysteresis. FIG. 4B shows an example of a magnetic hysteresis loop 410 relating the magnetic flux density B in the magnetic core to the surrounding magnetic field strength H. The magnetic flux density B refers to a measure of the actual magnetic field in the magnetic core material and is thought of as the concentration of magnetic field lines or magnetic flux per unit cross-sectional area. The magnetic field strength H refers to a measure of the magnetic field generated by nearby currents flowing in a conductor (e.g., in a conductive track or excitation winding). The magnetic hysteresis loop may be further characterized by a positive saturation point 411 and a negative saturation point 412. At such saturation points 411, 412, changes in the magnetic field strength H no longer result in a substantial change in the magnetic flux density B. In other words, the saturation points 411, 412 can be understood as the points at which the magnetic core becomes saturated with the magnetic field lines.

[0048] For example, when a positive excitation voltage 401 is applied to a first excitation winding, the resulting current 402 can generate a magnetic field. The resulting change in magnetic field strength H will change the magnetic flux density B in the magnetic core according to a hysteresis loop 410. The changing magnetic flux density B in the magnetic core can then affect the response current 402, for example, by back electromotive force, the changing impedance of the excitation winding, and the changing inductance of the excitation winding. During one duty cycle 405, the current response 402 can change, for example, to a maximum value, thereby driving 413 the magnetic core to a positive saturation point 411. Upon reaching saturation, the impedance and inductance of the excitation winding can drop significantly, which can result in a current spike 406. The drive circuit can be configured to detect the current spike 406 and, upon detection of the current spike 406, switch the excitation voltage 401 to a second excitation winding anti-parallel to the first winding. Thus, the polarity of the excitation voltage 401 can be reversed virtually instantly, commencing the next duty cycle, which causes the current response 402 to decrease from a maximum to a minimum, thus driving (414) the magnetic core from the positive saturation point 411 to the negative saturation point 412. Upon reaching the negative saturation point 412, another current spike is detected by the drive circuitry, which can then switch the excitation voltage 401 back to the first excitation winding.

[0049] In the absence of a fault current, the outgoing and return charging currents flowing through the conductive tracks of the electric circuit may be substantially equal in magnitude. Thus, the magnetic fields generated by each conductive track cancel each other. Thus, the response current 402 may be substantially symmetrical and the excitation voltage 401 may switch between predetermined minimum 403 and maximum 404 values ​​at a constant frequency of substantially equal duration. In other words, as shown in FIG. 4C, the duty cycle 405 of the excitation voltage 401 at the maximum 404 or minimum 404 may be substantially symmetrical (i.e., 50%) in the absence of a fault current.

[0050] When a fault current flows through the conductive track of the electric circuit, a magnetic field bias may be applied to the magnetic core. The magnetic field bias may cancel the magnetic hysteresis loop 410, resulting in a substantially asymmetric response current 402 and excitation voltage 401. In other words, the duty cycle 421 of the excitation voltage 401 at the maximum 404 or minimum 404 may be substantially asymmetric (i.e., higher or lower than 50%). The offset 422 from the symmetric duty cycle 405 (i.e., offset from 50%) may relate to the magnitude of the fault current. In other words, the fluxgate current sensor may detect and measure the fault current based on the offset 422 of the excitation voltage duty cycle 421 when the fault current is present compared to the symmetric duty cycle 405 when the fault current is not present.

[0051] The drive circuit can be configured to determine the duty cycle offset 442 and thus detect the presence of a fault current in the conductive track. The drive circuit can further be configured to generate an output signal based on the presence of a fault current in the conductive track. The drive circuit can generate an output signal, for example, upon detection of a fault current that may hinder the functioning of the residual current device (for example a fault current with a DC component above a certain threshold current). Preferably, the threshold current that triggers such an output signal can be adjusted by the drive circuit. The output signal may further trigger protective measures, such as interrupting the charging current. For this purpose, the output signal can preferably be transmitted to an integrated switch of the electric circuit so as to be able to interrupt the charging current. Alternatively or supplementarily, the output signal may be transmitted to other components included in the charging station, to components included in the switchboard, or to the electric vehicle.

[0052] Although the present invention has been described with reference to specific embodiments, the present invention is not limited to the details of the aforementioned exemplary embodiments, and it will be apparent to those skilled in the art that the present invention can be embodied with various changes and modifications without departing from the scope thereof. The present embodiments are therefore to be considered in all respects as illustrative and not restrictive, and the scope of the present invention is indicated by the appended claims, rather than by the foregoing description, and all changes that are within the meaning and range of equivalence of the claims are therefore intended to be included therein. In other words, it is contemplated to cover any modifications, variations, or equivalents that are within the scope of the underlying basic principles and whose essential attributes are claimed in this patent application. Furthermore, readers of this patent application will understand that the words "comprising" or "comprise" do not exclude other elements or steps, and the words "a" or "an" do not exclude a plurality, and that a single element, such as a computer system, a processor, or another integrated unit, can perform the functions of several means recited in the claims. Any signs in the claims shall not be interpreted as limiting the respective claims as applicable. Terms such as "first," "second," "third," "a," "b," "c," and the like, when used in the description or claims, are introduced to distinguish between similar elements or steps and do not necessarily describe a sequential or chronological order. Similarly, terms such as "top," "bottom," "upper," "lower," and the like, are introduced for purposes of description and do not necessarily indicate a relative location. It should be understood that the terms so used are interchangeable under appropriate circumstances and that embodiments of the invention are capable of operating in accordance with the invention in other orders or orientations other than those described or illustrated above.

[0053] As used in this application, the term "circuitry" may refer to one, more, or all of: (a) a hardware-only circuit implementation (e.g., an implementation with only analog and / or digital circuitry); and (b) a combination of hardware circuitry and software, such as (where applicable): (i) a combination of analog and / or digital hardware circuitry(s) and software / firmware; and (ii) any portion of a hardware processor(s) having software (including digital signal processor(s)); and (c) hardware circuit(s) and / or processor(s) (e.g., a microprocessor(s) or part of a microprocessor(s)) that require software (e.g., firmware) for operation, but may not be present when software is not required for operation. This definition of circuitry applies to all uses of the term in this application, including any claims. As a further example, as used in this application, the term circuitry also covers implementations of just a hardware circuit or processor (or processors), or a portion of a hardware circuit or processor, and the software and / or firmware associated therewith (or thereto).

Claims

1. 1. An electrical circuit (100) for detecting fault current in an electric vehicle charging station, comprising: a printed substrate (110) comprising at least two conductive tracks (111) for carrying a charging current along said printed substrate for charging and / or discharging said electric vehicle; A fluxgate current sensor (120) for detecting a fault current in the at least two conductive tracks, the fluxgate current sensor (120) comprising a magnetic core (121) having a through hole (122) arranged around the at least two conductive tracks, the at least two conductive tracks passing through the through hole of the magnetic core; Equipped with An electrical circuit (100), wherein the cross-section of the through-hole is shaped such that the distance between the printed substrate (110) and the magnetic core (121) is substantially equal along an inner limit of the magnetic core.

2. 10. The electrical circuit of claim 1, wherein the cross-section of the through-hole is substantially oval, stadium-shaped, or rectangular shaped.

3. 3. The electric circuit of claim 1 or 2, wherein the magnetic core (121) comprises a single piece of continuous magnetic material disposed about the through hole (122).

4. The electrical circuit of any one of claims 1 to 3, wherein the portion of the printed circuit board (110) is configured to allow the fluxgate current sensor to be moved over the portion of the printed circuit board to a designated position.

5. The electric circuit of any one of claims 1 to 4, wherein the flux-gate current sensor further comprises a protective housing (123) surrounding at least a portion of the magnetic core (121) configured to protect the magnetic core from stress.

6. The electric circuit of any one of claims 1 to 5, wherein the fluxgate current sensor (120) and the print substrate (110) comprise at least one attachment means (124, 125) for attaching the fluxgate current sensor to the print substrate.

7. The electric circuit of any one of claims 1 to 6, wherein the fluxgate current sensor further comprises at least two excitation windings (127, 128) wound around the magnetic core (121).

8. The electric circuit of claim 7, wherein the at least two excitation windings (127, 128) are interleaved.

9. 9. The electric circuit of claim 7 or 8, wherein the flux-gate current sensor further comprises a magnetic shield (126) partially surrounding the magnetic core (121) and the at least two excitation windings (127, 128) configured to distribute a magnetic field generated by currents in the at least two conductive tracks substantially uniformly within the magnetic core.

10. 10. The electric circuit of claim 7, wherein the flux-gate current sensor further comprises a drive circuit configured to alternately drive one of the at least two excitation windings (127, 128) with excitation voltages of opposite polarity and substantially equal magnitude.

11. The electrical circuit of claim 10 , wherein the drive circuit is further configured to generate an output signal based on the presence of a fault current in the at least two conductive tracks.

12. 12. The electric circuit according to claim 10 or 11, wherein the driving circuit is further integrated on the printed circuit board.

13. The electric circuit according to any one of claims 1 to 12, further comprising a switch (140) configured to interrupt the charging current in the at least two conductive tracks (111) upon detection of the fault current in the at least two conductive tracks (111).

14. An electric vehicle charging station comprising an electrical circuit (100) for detecting fault currents according to any one of claims 1 to 13.

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