Current transducer with shunt and magnetic field detector

Abstract

A current transducer having a shunt and a magnetic field detector is provided. The current transducer includes a primary conductor bus bar, a first current measurement device and a second current measurement device. The primary conductor bus bar includes a first measurement portion having a shunt resistor and a second measurement portion having a notch, the first current measurement device includes a shunt resistor, a first circuit board, and a shunt terminal interconnecting the circuit board to the primary conductor bus bar to measure a voltage across the shunt resistor, the second current measurement device comprises a magnetic field transducer comprising a magnetic field detector for measuring a primary current flowing through the core segment, the second current measurement device comprising a U-shaped magnetic core having an end portion branch and a lateral branch extending from the end portion branch to a free end, a central slot defined between the end portion branch and the lateral branch, a core segment of the primary conductor bus bar is mounted in the central slot, and a magnetic field detector is mounted on a second circuit board independent of the first circuit board and inserted in an air gap formed between the lateral branches.

Description

Technical Field

[0001] The utility model relates to a current transducer, which comprises a magnetic field detector and a primary conductor strip with a shunt resistor. Background Art

[0002] One of the known shunt transducer configurations, particularly for high current applications, includes a bus bar, typically in the form of a rectangular profile bar, configured to be clamped or otherwise connected to a primary conductor carrying the current to be measured. The bus bar typically has a shunt material portion such as Manganin - a copper, manganese, nickel alloy, integrally formed and connected to either end of the copper bus bar, whereby the resistance across the shunt material portion is measured.

[0003] In many applications, for example in the automotive sector, it is important to have a redundant measurement signal for safety and reliability reasons, which usually requires a second current transducer. It is known to provide a magnetic field sensor in the form of a Hall cell on an integrated circuit mounted on a circuit board located near the primary conductor strips, which also processes the shunt resistor signal. Although this arrangement is compact, reliability and safety are not optimized, as a faulty circuit board common to both the shunt sensor and the magnetic field sensor may result in failure of both current sensors. Furthermore, the accuracy of the magnetic field detector depends on the accuracy of the spacing and positioning of the Hall cell relative to the primary conductor strips, and for low currents the magnetic field strength is low and results in a high noise-to-signal ratio, which may be problematic in demanding applications such as electric motors in automotive drive applications. Utility Model Content

[0004] In view of the above, an object of the present invention is to provide a current transducer having a primary conductor bar and two current measurement systems which is durable, reliable and accurate over a wide range of operating conditions.

[0005] It would be advantageous to provide a current transducer that is economical to produce.

[0006] It would be advantageous to provide a shunt current transformer that is compact and easily integrated into external systems.

[0007] For certain applications it is advantageous to provide a current transducer which is suitable for measuring high currents and which is in the form of a bus bar which can be coupled to a standard circuit provided with bus bar terminal connections.

[0008] The purpose of the present invention is implemented by providing a system according to the present disclosure, and the advantageous embodiments set forth various advantageous features of the embodiments of the present invention.

[0009] The present invention discloses a current transducer, comprising a primary conductor bus bar, a first current measuring device and a second current measuring device. The primary conductor bus bar comprises a first measuring portion and a second measuring portion. The first measuring portion comprises a shunt resistor, and the second measuring portion comprises a notch.

[0010] The first current measuring device comprises:

[0011] - the shunt resistor,

[0012] - a first circuit board, and

[0013] - a shunt terminal interconnecting the circuit board to the primary conductor bus bar for measuring the voltage across the shunt resistor.

[0014] The second current measuring device comprises:

[0015] - a magnetic field transducer comprising a magnetic field detector for measuring a primary current flowing through the core segment, and

[0016] - A U-shaped magnetic core having end branches and transverse branches extending from the end branches to a free end and defining a central slot between the end branches and the transverse branches.

[0017] The core segment of the primary conductor bus bar is mounted in the central slot, and the magnetic field detector is mounted on a second circuit board independent of the first circuit board and inserted into the air gap formed between the lateral branches.

[0018] In an advantageous embodiment, the end branches of the U-shaped magnetic core are mounted against one side of the core segment of the primary conductor busbar.

[0019] In an advantageous embodiment, the second circuit board is arranged parallel to the transverse branches and the magnetic field detector comprises an integrated circuit chip mounted in an insulating overmolded surface on the second circuit board.

[0020] In an advantageous embodiment, an insulating housing is overmolded or assembled around the U-shaped magnetic core and the core segments, the housing comprising a cavity within a central slot of the U-shaped magnetic core into which the magnetic field detector and a portion of the second circuit board are inserted.

[0021] In an advantageous embodiment, the second current measuring device comprises a second connector having an insulating housing part comprising a shield, which is formed integrally with the housing and surrounds the U-shaped magnetic core and the core segments.

[0022] In an advantageous embodiment, the primary conductor busbar comprises transducer terminals at opposite ends of the primary conductor busbar for clamping or bolting to the outer conductor, the first current measuring device and the second current measuring device being positioned between the transducer terminals and in close proximity to each other.

[0023] In an advantageous embodiment, the first circuit board of the first current measuring device is mounted directly on the surface of the primary conductor bus bar above the shunt resistor.

[0024] In an advantageous embodiment, the first current measuring device comprises a first connector mounted on a top side of the first circuit board, the top side being opposite to a bottom side mounted against the primary conductor busbar.

[0025] In an advantageous embodiment, the first circuit board comprises shunt terminals (15) in the form of solder reflow contacts connected directly to the primary conductor busbars.

[0026] In an advantageous embodiment, the shunt resistor is made of manganese copper.

[0027] In an advantageous embodiment, the current transducer is for implementation in an electric vehicle battery management system.

[0028] In an advantageous embodiment, the width ( W3 ) of the lateral branch of the U-shaped core is equal to or smaller than the width ( W2 ) of the corresponding notch in which the lateral branch is located.

[0029] In an advantageous embodiment, the width ( W1 ) of the core segment formed between the recesses is equal to the width of the central groove between the inner sides of the transverse branches, apart from manufacturing tolerances allowing for the fitting of the core segment in the central groove.

[0030] Other advantageous features of the present invention will be apparent from the following detailed description of embodiments of the present invention and the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 is a perspective view of a current transducer according to an embodiment of the utility model;

[0032] Figure 2 yes Figure 1 An exploded view of an embodiment of the present invention;

[0033] Figure 3 yes Figure 1 A side view of an embodiment of the present invention;

[0034] Figure 4 is along Figure 1 A cross-sectional view of line EE;

[0035] Figure 5 Schematic diagram showing a measurement channel of a current transducer according to an embodiment of the present utility model. DETAILED DESCRIPTION

[0036] With reference to the accompanying drawings, a current transducer 1 according to an embodiment of the utility model comprises a primary conductor bus bar 2, a first current measuring device 5 and a second current measuring device 6. The first current measuring device forms part of a first measuring channel 3 outputting a first measuring output signal. The second current measuring device forms part of a second measuring channel 4 outputting a second measuring output signal. An external measurement processing unit connected to the current transducer 1 may include a control system that compares or cross-checks the first measuring output signal and the second measuring output signal to detect faults in the current transducer and ensures safe operation of components monitored or controlled with the aid of the current transducer. Such components may, for example, include a battery pack or an electric motor of an electric vehicle, for which a high level of safety is required.

[0037] The current transducer according to the embodiment of the present invention may be used, for example, in a battery management system for an electric vehicle.

[0038] The primary conductor can be provided with a transducer terminal 10, for example in the form of a known hole, for clamping on a bolt-nut connection. However, other interconnection methods known per se can be provided in various variants, with or without holes, for example by clamping welding or soldering.

[0039] The primary conductors may have non-planar shapes, for example with curved portions, and wherein the transducer terminals are not necessarily aligned. Various configurations of bus bars may be provided to accommodate the primary conductor configuration of the devices and the devices to which they are to be coupled.

[0040] One or more current transducers 1 may be directly integrated within an electrical system of a device having one or more electrical phases, or may be provided as separate components for assembly and connection to external devices.

[0041] The primary conductor busbar 2 may specifically have the form of a substantially rectangular cross-section busbar. The primary conductor busbar 2 extends between opposite ends provided with terminals 10 and between the terminals 10, the primary conductor busbar 2 comprises a first measuring portion 12 comprising the shunt resistor 9 and a second measuring portion 14 comprising a notch 16 located on the side of a narrow core segment 18.

[0042] The first current measuring device 5 includes a shunt resistor 9, a first circuit board 11, and a first connector 20 mounted on and connected to the first circuit board. The shunt resistor 9 is connected to the first circuit board via a shunt terminal 15 located at the end of the shunt resistor so that the current flowing through the shunt portion can be measured. The circuit for measuring the shunt resistance itself is well known.

[0043] In an advantageous embodiment, the shunt terminals comprise pads on a circuit board which are soldered at corresponding discrete points of the primary conductor, for example by reflow soldering. The reflow soldering can be performed in a standard soldering process for SMD components. The pads are separated from one another, and the voltages present on these pads are separate inputs to the analog front end for processing.

[0044] In a variation, the shunt terminal may include a pin terminal that is welded or soldered to the surface of the primary conductor, or inserted with an interference fit into a corresponding terminal receiving cavity formed in the primary conductor.

[0045] The shunt terminal 15 is preferably connected to the main material of the primary conductor at the interface (boundary) of the shunt portion, rather than directly to the shunt resistor material.

[0046] The material of the shunt resistor 9 is preferably a material with a low temperature coefficient of resistance, in particular a copper-manganese-nickel (Cu-Mn-Ni) alloy, such as Manganin (Cu84 / Mn12 / Ni4 or Cu86 / Mn12 / Ni2) or a copper-nickel (Cu-Ni) alloy Constantan (Cu55 / / Ni35), which are known for their very low temperature coefficient of resistance properties in shunt resistors. Other materials with low temperature coefficient of resistance values, such as certain nickel-chromium alloys NiCr, may also be advantageously used.

[0047] The second current measuring device comprises a magnetic field transducer. The magnetic field transducer comprises a U-shaped magnetic core 7, a magnetic field detector 8 mounted in an air gap of the magnetic core 7, and a second connector 24 connected to the magnetic field detector.

[0048] The U-shaped core 7 comprises an end branch 7a and two parallel spaced lateral branches 7b extending from the end branch 7a to respective free ends. The two parallel spaced lateral branches 7b define a central slot 26 which also constitutes an air gap formed at the free ends of the lateral branches.

[0049] The magnetic field detector 8 is mounted on a second circuit board 13, which is also at least partially positioned within the air gap. The magnetic field detector may for example comprise a Hall sensor in an integrated circuit (IC) chip 11, which is per se well known in the field of magnetic field detectors.

[0050] The magnetic field transducer further comprises an insulating housing 22 surrounding the U-shaped magnetic core 7 and a portion 18 of the second measurement portion 14 of the primary conductor busbar 2 .

[0051] The central slot 26 of the U-shaped core 7, which defines the distance between the inner parallel sides of the transverse branches 7b, has a width equal to the width W1 of the core segment 18, except for a slight tolerance to allow for the assembly of the central slot 26 between the transverse branches 7b. The U-shaped core is inserted on the core segment 18 until the end branch 7a rests on the core segment 18. The width W3 of the transverse branch 7b is preferably smaller than the width W2 of the notch 16, so that the transverse branch 7a is completely located inside the notch 16. In this way, the width of the magnetic field transducer is kept within the width of the primary conductor busbar, which results in a compact structure.

[0052] The insulating housing 22 may be overmolded around the U-shaped core 7 and the core 18 of the primary conductor busbar on the side opposite to the side contacting the end branch 7a of the U-shaped core, or alternatively assembled. The housing also comprises a housing portion which forms a housing portion of a second connector 24, in particular a shield 27 which forms an electrical terminal 25 of the second connector. In the embodiment shown, the electrical terminal is in the form of a pin terminal 25 surrounded by the shield 27 of the second connector housing portion, the opposite end of the pin contact being connected to the second circuit board 13 and supported by the overmolded housing.

[0053] The second circuit board 13 is arranged substantially parallel to the transverse branch 7b, and the magnetic field detector 8 can be surface mounted on the second circuit board 13 and inserted into the central groove 26 together with the circuit board, in particular, accommodated in the housing central groove 29. The positioning of the magnetic field detector 8 and the second circuit board 13 can be defined by the housing 22 overmolded or assembled around the transverse branch 7b of the U-shaped magnetic core 7.

[0054] like Figure 4 As best shown in , the magnetic field transducer can have a width within the width of the primary conductor bus bar 2 to obtain a very compact construction, and also have a relatively low height, while benefiting from the good capture of the magnetic field generated by the reduced width core segment 18 of the primary conductor. Given the relatively narrow length of the magnetic field transducer 6, it can be positioned close to the first current measurement device 5 with the shunt resistor 9, while having a completely separate circuit board and connector for safe and reliable operation.

[0055] The first circuit board 11 of the first current measuring device can be mounted directly against the surface of the main conductor bus 2, and the first connector 20 is mounted on top of the first circuit board 11, whereby the first connector 20 can be formed separately and mounted on the circuit board, or include a shell that is overmolded around the first circuit board 11 and optionally overmolded around a portion of the main conductor bus.

[0056] It may be noted that, in a variant, the insulating housing of the first connector 20 and the magnetic field transducer may be formed together as a single overmoulding (not shown).

[0057] The central slot 26 into which the magnetic field detector 8 and the second circuit board 13 are inserted may be closed by a separately assembled cover element 28 .

[0058] Reference numerals list Current transducer 1

[0059] Primary conductor busbar 2

[0060] Transducer terminal 10

[0061] First measuring section 12

[0062] Shunt resistor 9

[0063] Second measuring section 14

[0064] Notch 16

[0065] Core segment 18

[0066] First measurement channel 3

[0067] First current measuring device 5

[0068] Shunt resistor 9

[0069] Shunt terminal 15

[0070] The first circuit board 11

[0071] First connector 20

[0072] Second measurement channel 4

[0073] Second current measuring device 6

[0074] Magnetic field transducer

[0075] U-shaped core 7

[0076] End branch 7a

[0077] Lateral branch 7b

[0078] Center slot 26

[0079] Magnetic field detector 8

[0080] For example, the Hall sensor on the integrated circuit (IC) chip 11 and the second circuit board 13

[0081] Housing 22

[0082] Connector shroud 27

[0083] Shell center groove 29

[0084] Cover element 28

[0085] Second connector 24 pin terminal 25 primary conductor width W core segment width W1

[0086] Notch depth W2 lateral branch width W3 core segment length L.

Claims

1. A current transducer (1) comprising a primary conductor busbar (2), a first current measuring device (5) and a second current measuring device (6), the primary conductor busbar comprising a first measuring portion (12) comprising a shunt resistor (9) and a second measuring portion (14) comprising a notch (16), The first current measuring device (5) comprises - the shunt resistor (9), - a first circuit board (11), and - a shunt terminal (15) interconnecting the circuit board to the primary conductor bus bar for measuring the voltage across the shunt resistor (9), The second current measuring device (6) comprises - a magnetic field transducer comprising a magnetic field detector (8) for measuring a primary current flowing through a core segment (18), It is characterized in that The second current measuring device (6) comprises a U-shaped magnetic core (7), the U-shaped magnetic core having end branches (7a) and transverse branches (7b) extending from the end branches to a free end, and defining a central slot (26) between the end branches and the transverse branches, the core segment (18) of the primary conductor bus bar being mounted in the central slot (26), and the magnetic field detector (8) being mounted on a second circuit board (13) independent of the first circuit board (11) and inserted in an air gap formed between the transverse branches (7b).

2. The current transducer according to claim 1, characterized in that: The end branch (7a) of the U-shaped magnetic core (7) is mounted against one side of the core segment (18) of the primary conductor busbar (2).

3. The current transducer according to claim 1 or 2, characterized in that: The second circuit board (13) is arranged parallel to the transverse branch (7b), and the magnetic field detector (8) comprises an integrated circuit chip mounted in an insulating overmolded surface on the second circuit board (13).

4. The current transducer according to claim 1, characterized in that: An insulating housing (22) is overmolded or assembled around the U-shaped magnetic core (7) and the core segment (18), the housing comprising a cavity (29) within the central slot (26) of the U-shaped magnetic core, the magnetic field detector and a portion of the second circuit board (13) being inserted into the cavity.

5. The current transducer according to claim 1, characterized in that: The second current measuring device (6) comprises a second connector (24) having an insulating housing portion, the insulating housing portion comprising a shield (27) formed integrally with the housing (22) around the U-shaped magnetic core (7) and the core segment (18).

6. The current transducer according to claim 1, characterized in that: The current transducer comprises transducer terminals (10) at opposite ends of the primary conductor bus bar for clamping or bolting to an external conductor, the first current measuring device (5) and the second current measuring device (6) being positioned between the transducer terminals and in close proximity to each other.

7. The current transducer according to claim 1, characterized in that: The first circuit board (11) of the first current measuring device (5) is mounted directly on the surface of the primary conductor bus bar above the shunt resistor.

8. The current transducer according to claim 7, characterized in that: The first current measuring device (5) comprises a first connector (20) mounted on a top side of the first circuit board (11) opposite to a bottom side mounted against the primary conductor busbar.

9. The current transducer according to claim 7 or 8, characterized in that: The first circuit board (11) includes shunt terminals (15) in the form of solder reflow contacts directly connected to the primary conductor busbar (2).

10. The current transducer according to claim 1, characterized in that: The shunt resistor (9) is made of manganese copper.

11. The current transducer according to claim 1, characterized in that: The current transducer is intended for implementation in an electric vehicle battery management system.

12. The current transducer according to claim 1, characterized in that: The width (W3) of the lateral branch (7b) of the U-shaped magnetic core (7) is equal to or smaller than the width (W2) of the corresponding notch (16) in which the lateral branch is located.

13. The current transducer according to claim 1, characterized in that: Apart from manufacturing tolerances that allow the core segment (18) to be assembled within the central groove (26), the width (W1) of the core segment (18) formed between the recesses (16) is equal to the width of the central groove (26) between the inner sides of the lateral branches (7b).

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