Open-loop current transducer

Abstract

The utility model relates to an open loop current transducer. The open-loop current transducer (1) comprises a housing (2), a magnetic core (6) and a magnetic field sensor system (4), the magnetic core (6) and the magnetic field sensor system being mounted within the insulating housing (2), the magnetic core comprising a plurality of magnetic field detector receiving slots (9), and the magnetic field sensor system comprising a corresponding plurality of magnetic field detectors (3), one magnetic field detector being inserted in each magnetic field detector receiving slot (9), the current transducer comprises a primary conductor channel (7) for receiving one or more primary conductors carrying a current to be measured therethrough, the magnetic core (6) comprising a central channel surrounding the primary conductor channel (7), an inner peripheral side (11) of the magnetic core defining the central channel (7c), and an outer peripheral side (12) of the magnetic core defining an outer side of the magnetic core (6), the magnetic core extends axially between first and second opposing axial sides (13). The magnetic core has a closed circuit body comprising a bridge portion (10) between each magnetic field detector receiving slot and respective inner and outer peripheral sides (11, 12).

Description

TECHNICAL FIELD

[0001] The utility model relates to an open loop current transducer with a magnetic core having a plurality of air gaps and a plurality of magnetic field detectors located in the air gaps. BACKGROUND

[0002] Open loop current transducers with a magnetic core having a plurality of air gaps and corresponding magnetic field detectors mounted in the air gaps are known and are typically used for high current applications, typically for measuring currents exceeding 100 amperes, for example for currents that can exceed 1,000 amperes and possibly 10,000 amperes. For such high currents it is known to provide a magnetic core comprising a plurality of limbs between which air gaps are formed in which magnetic field detectors, for example Hall effect sensors, are inserted. The magnetic core components are assembled around a central passage through which a primary conductor carrying the current to be measured extends. The assembly of the different magnetic core components and the adjustment of the air gaps formed between the assembled magnetic core components are expensive and the size of the air gaps can vary as a result of mechanical and thermal effects of the relative position of the moving components. SUMMARY

[0003] In view of the above, it is an object of the utility model to provide a current transducer with a magnetic core and a plurality of air gaps and associated magnetic field detectors that is economical to produce and accurate, in particular with accurate air gap dimensions.

[0004] It is advantageous to provide a robust and stable current transducer.

[0005] It is advantageous to provide a current transducer that is durable and can withstand harsh environments subjected to mechanical and thermal stresses.

[0006] It is advantageous to provide such a current transducer that is easy to install, implement and use.

[0007] The object of the utility model is achieved by providing an open loop current transducer according to the utility model.

[0008] The advantageous embodiments set forth various advantageous features of embodiments of the utility model.

[0009] The utility model discloses a kind of open-loop current transducer, it includes shell, magnetic core and magnetic field sensor system, magnetic core and magnetic field sensor system are installed in insulating shell.The magnetic core includes multiple magnetic field detector receiving slots, and the magnetic field sensor system includes corresponding multiple magnetic field detectors, one magnetic field detector is inserted in each magnetic field detector receiving slot.The current transducer includes primary conductor channel, for receiving one or more primary conductors carrying current to be measured by primary conductor channel, the magnetic core includes the central passage around primary conductor channel, the inner periphery side of magnetic core defines central passage, and the outer periphery side of magnetic core defines the outside of magnetic core, magnetic core extends axially between first and second opposite axial sides.Magnetic core has closed circuit body, which includes bridging portion between each magnetic field detector receiving slot and corresponding inner periphery side and outer periphery side.

[0010] In an advantageous embodiment, the cross-section of the bridging portion of each magnetic field detector receiving slot has a cross-sectional area that is less than 30% of the total cross-sectional area of the magnetic core.

[0011] In an advantageous embodiment, the cross-section of the bridging portion of each magnetic field detector receiving slot has a cross-sectional area that is less than 20%, preferably less than 10%, of the cross-sectional area of the magnetic core.

[0012] In an advantageous embodiment, the magnetic core is made of a ferrite material, as a single integral formed component.

[0013] In an advantageous embodiment, the magnetic core is made of an axially arranged stack of sheets of ferromagnetic material.

[0014] In an advantageous embodiment, some of the plurality of sheets do not include a bridging portion, while the outer opposite axial sheets include said inner and outer bridging portions.

[0015] In an advantageous embodiment, only the axially outer sheets include said bridging portions.

[0016] In an advantageous embodiment, the plurality of magnetic field detector receiving slots and the associated corresponding plurality of magnetic field detectors are four or more.

[0017] In one embodiment, the magnetic core has a rectangular shape, and has four magnetic field detectors and associated magnetic field detector receiving slots, one on each branch of the rectangular shape.

[0018] In one embodiment, the magnetic core has a circular shape, and includes more than four said magnetic field detectors and associated corresponding magnetic field detector receiving slots, the corresponding magnetic field detector receiving slots being distributed with uniform spacing between adjacent magnetic field detectors.

[0019] In an advantageous embodiment, the magnetic field sensor system comprises a circuit board arranged in parallel and covering the axial sides of the magnetic core, the magnetic field detector has a connection pin connected to a circuit trace on the circuit board and extending upright from the circuit board into a receiving slot of the magnetic field detector.

[0020] In an advantageous embodiment, the magnetic core, the magnetic field sensor system and the housing are assembled together in axial direction.

[0021] In an advantageous embodiment, the housing comprises a base having a central channel section extending through the central channel of the magnetic core and defining a primary conductor channel, the housing further comprises an insulating filler or potting material placed around the magnetic field sensor system and the magnetic core mounted within the base of the housing.

[0022] In an advantageous embodiment, the magnetic field sensor system comprises a connector mounted on the circuit board for connection to an external circuit.

[0023] In an advantageous embodiment, the open loop current transducer is configured for measuring currents exceeding 100 amperes, preferably currents exceeding 1,000 amperes.

[0024] Further advantageous features of the present utility model will become apparent from the following detailed description of the utility model embodiments and the attached drawings. BRIEF DESCRIPTION OF DRAWINGS

[0025] Figure 1a is a perspective view of a current transducer according to an embodiment of the present utility model;

[0026] Figure 1b is an exploded perspective view of an embodiment of Figure 1a

[0027] Figure 2a is a front plan view of a current transducer of Figure 1a

[0028] Figure 2b is a cross-sectional view along line A-A of Figure 2a

[0029] Figure 2c is a cross-sectional view along line B-B of Figure 2a

[0030] Figure 3a is a perspective view of a magnetic core of a current transducer according to an embodiment of the present utility model;

[0031] Figure 3b is a perspective view of a magnetic core of a current transducer according to another embodiment of the present utility model;

[0032] Figure 3c ​​​​is a perspective view of a magnetic core of a current transducer according to yet another embodiment of the present utility model;

[0033] Figure 4a is a plot of the primary current of a current transducer from having Figure 1a and Figure 1b the characteristics shown in Figure 4b and the dimensions shown in

[0034] Figure 4b shows the dimensions of the magnetic core used in the measurement of Figure 4a . DETAILED DESCRIPTION

[0035] With reference to the drawings, an open loop current transducer 1 comprises an insulating housing 2, a magnetic core 6 and a magnetic field sensor system 4, the magnetic core 6 and the magnetic field sensor system 4 being mounted within the insulating housing 2.

[0036] The insulating housing can comprise a base 2a, for example an injection moulded plastic base, and an insulating filler or potting material 2b which is injected or cast over the components mounted within the housing to provide electrical insulation and also to provide a stable secure retention of the components within the housing. As an alternative to, or in addition to, the insulating filler, the housing can comprise a cover (not shown) which fits to the base 2a and covers the magnetic field sensor system 4 and the magnetic core 6 within the housing. Potting materials and the insulating housing materials themselves are well known in the art of current transducers.

[0037] The magnetic field sensor system 4 comprises a circuit board 5 and a plurality of magnetic field detectors 3 mounted on the circuit board 5 and electrically connected to conductive tracks on the circuit board 5 for power supply and measurement signal transmission between the magnetic field detectors and external circuitry (not shown). The magnetic field sensor system 4 also comprises a connector 8 mounted on and connected to the circuit board 5 for interconnection of the current transducer 2 with external circuitry. The connector can have various forms well known in the art, for example for pluggable connection to an external plug connector or for direct mounting to an external circuit board with pins.

[0038] The current transducer 1 has a primary conductor passage 7 extending through the current transducer for insertion of one or more primary conductors therethrough.

[0039] The current transducer can also comprise a length of primary conductor rod pre-assembled to the transducer as is known in the art per se.

[0040] The magnetic core 6 comprises a body of ferromagnetic material around a central passage 7c and can have different shapes, for example Figure 1b and Figure 3a and Figure 3b the rectangular shape shown in Figure 3cThe magnetic core can have various other shapes (not shown), such as square, hexagonal or other polygonal or even irregular shapes, configured to surround one or more primary conductors carrying the current to be measured. Thus, the magnetic core has an inner peripheral side 11 defining a central passage 7c and an outer peripheral side 12 defining the outer boundary of the magnetic core body, the magnetic core extending between opposite axial sides 13, having a thickness T which can vary as a function of the maximum current to be measured, so as to vary the cross section of the magnetic core, so as to avoid saturation at the maximum measurable current.

[0041] The housing 2 can comprise a central passage portion 7a which is inserted in the corresponding central passage 7c in the magnetic core 6. The primary conductors can be inserted or mounted through the housing central passage portion 7a.

[0042] According to one aspect of the application, the magnetic core 6 comprises a plurality of magnetic field detector receiving slots 9 formed inside the magnetic core body, extending between the inner peripheral side 11 and the outer peripheral side 12, with a width W1 which is less than the width W2 defined by the distance between the inner peripheral side 11 and the outer peripheral side 12. The difference in width W1-W2 results in the formation of a bridge 10 between each end of the magnetic field detector receiving slot 9 and the respective inner and outer peripheral sides 11, 12. This is different from conventional transducers which either have a complete separation between the portions of the magnetic core forming the air gap or, in some cases, have slots extending from the outer peripheral side into the magnetic core body. The presence of the bridge portion 10 ensures that the magnetic core 6 has a closed circuit body around the central passage 7c on the inner and outer peripheral sides 11, 12, which provides a particularly robust structure which also has a high dimensional accuracy of the separation of the air gap. The latter ensures a high measurement accuracy of the magnetic field detectors inserted inside the magnetic field detector receiving slots 9. Furthermore, the closed circuit body of the magnetic core is robust during manufacturing, transport, assembly and use in harsh environments.

[0043] In order to ensure that the measurement accuracy is also high for small currents to be measured, the bridge portion 10 has a cross-sectional area (W1-W2) x T which is less than 30%, preferably less than 20%, more preferably less than 10% of the total cross-sectional area W1 x T of the magnetic core at the location of the magnetic field detector receiving slot 9:

[0044] (W1-W2) x T < 0.3 x W1 x T, preferably (W1-W2) x T < 0.2 x W1 x T, more preferably (W1-W2) x T < 0.1 x W1 x T.

[0045] The cross-sectional area is measured transversely to the direction of the magnetic core, i.e. perpendicular to the general direction of the magnetic field lines circulating in the magnetic core 6.

[0046] InFigure 3a In the magnetic core 6 of the illustrated embodiment, the magnetic core can be made of ferrite, such as MnZn or NiZn ferrite, and for very high frequencies also of garnet or spinel as a single piece formed component.

[0047] In the illustrated embodiment, the magnetic core can be made of a stack of sheets of ferromagnetic material, such as FeSi or NiFe (Permalloy, Ni-Fe high permeability alloy, etc.) alloy; and nanocrystalline or amorphous soft magnetic alloys, which are well known per se in the field of soft magnetic cores. Figure 3b Figure 3c In the illustrated embodiment, the magnetic core can be made of a stack of sheets of ferromagnetic material, such as FeSi or NiFe (Permalloy, Ni-Fe high permeability alloy, etc.) alloy; and nanocrystalline or amorphous soft magnetic alloys, which are well known per se in the field of soft magnetic cores.

[0048] In the embodiment of the stack, the inner stack can be free of bridging portions, whereby only the sheets on the axial outer sides 13 each have a bridging portion 10. In these embodiments, the bridging portion on the axial outer side sheets provides durability and stability, while the cross section of the bridging portion 10 is significantly reduced and is less than 10%, preferably less than 5%, of the total cross section of the magnetic core in which the magnetic field detector receiving slots 9 are located.

[0049] In the illustrated embodiment, the magnetic core can be made of a stack of sheets of ferromagnetic material, such as FeSi or NiFe (Permalloy, Ni-Fe high permeability alloy, etc.) alloy; and nanocrystalline or amorphous soft magnetic alloys, which are well known per se in the field of soft magnetic cores. Figure 3b Figure 3c In the illustrated embodiment, the magnetic core can be made of a stack of sheets of ferromagnetic material, such as FeSi or NiFe (Permalloy, Ni-Fe high permeability alloy, etc.) alloy; and nanocrystalline or amorphous soft magnetic alloys, which are well known per se in the field of soft magnetic cores.

[0050] Since the cross section of the bridging portion 10 is small compared to the entire cross section of the magnetic core in which the slots 9 are located, the bridging portion saturates at low current values compared to the maximum current to be measured, whereby at saturation the bridging portion has substantially the same permeability as the air in which the magnetic field detectors 3 are located.

[0051] One of the advantages of the bridging portions on the outer peripheral side 11 and the inner peripheral side 12 is the ability to have a large number of slots and associated corresponding magnetic field detectors 3, for example as illustrated in Figure 3c which shows a variant with eight magnetic field detectors and eight magnetic field detector receiving slots in the magnetic core, which allows the measurement of a primary current with very high values for the size of the current transducer 1. This is because this portion of the magnetic core between the magnetic field detectors is rather short and is less prone to saturation compared to longer portions. Furthermore, by increasing the number of magnetic field detectors, a more precise current measurement is provided.

[0052] Figure 4a The relationship between the primary current (Ip) and the output voltage (Vout) of the current transducer according to the embodiments of Figure 1a and Figure 1b is shown, wherein Figure 4b ​​The dimensions in mm are shown in the figure. It can be seen that the measurement errors of small currents are not noticeable on the figure and are negligible on the scale of the maximum measured current of 1,500 amperes.

[0053] The circuit board 5 can advantageously be arranged parallel and covering the axial side 13 of the magnetic core. The magnetic field detector can have a connection pin which is connected to a circuit track on the circuit board and which extends straight up from the circuit board into the magnetic field detector receiving slot. The magnetic core, the magnetic field sensor system and the housing can be assembled together in axial direction.

[0054] List of used markers

[0055] Current transducer 1

[0056] Primary conductor channel 7

[0057] Housing 2

[0058] Base 2a

[0059] Central channel portion 7a

[0060] Cover portion

[0061] Insulating filler / potting 2b

[0062] Magnetic field sensor system 4

[0063] Magnetic field detector 3

[0064] Circuit board 5

[0065] Central bore 7b

[0066] Connector 8

[0067] Magnetic core 6

[0068] Closed ring body

[0069] Central channel 7c

[0070] Inner peripheral side 11

[0071] Outer peripheral side 12

[0072] Axial side 13

[0073] Magnetic field detector receiving slot 9

[0074] Bridge portion 10

[0075] Axial direction A.

Claims

1. An open loop current transducer (1) comprising a housing (2), a magnetic core (6) and a magnetic field sensor system (4), the magnetic core (6) and the magnetic field sensor system being mounted within the insulating housing (2), the magnetic core (6) comprising a plurality of magnetic field detector receiving slots (9) and the magnetic field sensor system (4) comprising a corresponding plurality of magnetic field detectors (3), one magnetic field detector being inserted in each magnetic field detector receiving slot (9), the current transducer comprising a primary conductor passage (7) for receiving one or more primary conductors carrying a current to be measured therethrough, the magnetic core (6) comprising a central passage (7c) around the primary conductor passage (7), an inner peripheral side (11) of the magnetic core delimiting the central passage (7c) and an outer peripheral side (12) of the magnetic core delimiting an outer side of the magnetic core (6), the magnetic core (6) extending axially between first and second opposite axial sides (13), characterized in that, The magnetic core has a closed circuit body comprising a bridge portion (10) between each magnetic field detector receiving slot (9) and a respective inner and outer peripheral side (11, 12).

2. The open-loop current transducer of claim 1, wherein, The cross-sectional area of the cross-section of the bridge portion (10) of each magnetic field detector receiving slot (9) is less than 30% of the total cross-sectional area of the magnetic core.

3. The open-loop current transducer of claim 2, wherein, The cross-sectional area of the cross-section of the bridge portion (10) of each magnetic field detector receiving slot (9) is less than 20% of the cross-sectional area of the magnetic core.

4. The open-loop current transducer of claim 3, wherein, The cross-sectional area of the cross-section of the bridge portion (10) of each magnetic field detector receiving slot (9) is less than 10% of the cross-sectional area of the magnetic core.

5. The open-loop current transducer of any one of claims 1 to 4, wherein, The magnetic core is made of a ferrite material as a single, integrally formed component.

6. The open-loop current transducer of any one of claims 1 to 4, wherein, The magnetic core is made of an axially arranged stack of a plurality of sheets of ferromagnetic material.

7. The open-loop current transducer of claim 6, wherein, Some of the plurality of sheets do not comprise the bridge portion, while the outer, opposite axial sheets comprise the bridge portion (10).

8. The open-loop current transducer of claim 7, wherein, Only the outer, opposite axial sheets comprise the bridge portion.

9. The open-loop current transducer of any one of claims 1 to 4, wherein, The plurality of magnetic field detector receiving slots (9) and the associated corresponding plurality of magnetic field detectors (3) is four or more.

10. The open-loop current transducer of claim 9, wherein, The magnetic core has a rectangular shape, and has four magnetic field detectors and associated magnetic field detector receiving slots, one on each branch of the rectangular shape.

11. The open-loop current transducer of any one of claims 1 to 4, wherein, The magnetic core has a circular shape, and comprises more than four of the magnetic field detectors (3) and associated corresponding magnetic field detector receiving slots (9), distributed with uniform spacing between adjacent magnetic field detectors.

12. The open-loop current transducer of any one of claims 1 to 4, wherein, The magnetic field sensor system (4) comprises a circuit board (5) arranged in parallel and covering an axial side (13) of the magnetic core (6), the magnetic field detectors having connection pins connected to circuit traces on the circuit board and extending upright from the circuit board into the magnetic field detector receiving slots.

13. The open-loop current transducer of any one of claims 1 to 4, wherein, The magnetic core, magnetic field sensor system, and housing (2) are assembled together in an axial direction.

14. The open-loop current transducer of any one of claims 1 to 4, wherein, The housing (2) comprises a base (2a) having a central passage portion (7a) extending through the central passage (7c) of the magnetic core (6) and defining the primary conductor passage (7), and an insulating filler or potting material (2c) placed around the magnetic field sensor system and the magnetic core (6) mounted within the base (2a) of the housing (2).

15. The open loop current transducer of claim 12, wherein, The magnetic field sensor system (4) comprises a connector (8) mounted on the circuit board (5) for connection to external circuitry.

16. The open-loop current transducer of any one of claims 1 to 4, wherein, The open loop current transducer is configured to measure currents in excess of 100 amperes.

17. The open-loop current transducer of any one of claims 1 to 4, wherein, The open loop current transducer is configured to measure currents in excess of 1,000 amperes.

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