An R-type open core and its application in Hall current sensor

Abstract

The present invention provides an R-type open iron core and its application in a Hall current sensor. The iron core is formed by winding a long strip of metal sheet from the inside to the outside, and an open air gap is cut out at the side position where the coil is not wound. The magnetic cross section of the iron core is circular; the metal sheet includes a plurality of segments connected end to end, the thickness of each part of the metal sheet is equal and the width decreases from the middle to the two ends, the width of each part in the same segment is equal, and a transition connection section with a gradually changing width is provided between adjacent segments, wherein the width of the middle segment is equal to the diameter of the magnetic cross section of the iron core, and the widths of the two segments symmetrical about the middle segment are equal, and the length of each segment is set to be able to continue to be fully wound on the basis of the previous winding. The use of the above-mentioned iron core in the Hall current sensor can achieve the goals of extremely small leakage magnetic field, low magnetic resistance, small iron loss, and minimum coil internal resistance, thereby improving the accuracy and performance of the sensor.

Description

Technical Field

[0001] The invention relates to the technical field of Hall current sensors, and in particular to an R-type open iron core and application thereof in a Hall current sensor. Background Art

[0002] The Hall current sensor is an electric-magnetic-electric conversion device based on the Hall effect and made of semiconductor materials. The Hall current sensor can achieve isolation and signal conversion between the primary side (main circuit) and the secondary side (secondary circuit), thereby realizing the detection and monitoring of strong and large currents in the working circuit, and output weak current signals or other communication signals with a certain ratio to meet the data collection of the upper-level control and protection system.

[0003] Most of the Hall current sensors in the prior art use C-shaped (ring-shaped) or U-shaped traditional iron cores, which are unsatisfactory in performance, structure and manufacturing process, mainly including the following defects:

[0004] 1. C-type core

[0005] When the measured current flows through the copper bus (i.e., bus), a magnetic field is generated along the current direction of the copper bus according to the right-hand screw rule. According to instrument detection and experimental analysis, it is found that the magnetic induction intensity distributed in the middle area of ​​the wide side (the upper and lower wide sides) of the copper bus cross-section is the largest, that is, the magnetic lines of force are the densest; while the magnetic induction intensity distributed on the narrow side is relatively small.

[0006] Therefore, when the C-type iron core is used with the copper busbar, the four corners of the copper busbar's busbar cross-section are closest to the iron core and the coil, while the two wide sides are farthest from the iron core and the coil. When the measured current passes through the primary busbar, a uniform magnetic field cannot be obtained around the iron core and the coil, that is, the C-type iron core cannot accurately gather the magnetic field around the copper busbar.

[0007] In addition, due to the structural characteristics of the C-type iron core, the secondary side compensation coil winding is unbalanced. The distance between two adjacent turns in the coil is closer on the inner side of the ring and farther on the outer side of the ring. As a result, the coil is arranged more densely inside the ring and more sparsely outside the ring. When the compensation current passes through, the magnetic density gathered in the inner ring of the iron core is greater than that of the outer ring, causing the magnetic field to leak from the center of the inner ring of the iron core.

[0008] 2. U-shaped core

[0009] When the U-shaped cores are in use, the openings of the two cores are facing each other, so that there are joint surfaces in the core magnetic circuit, and the joint surfaces are perpendicular to the magnetic flux lines, forming a magnetic break layer, that is, the magnetic flux density at the gap is significantly reduced, resulting in leakage magnetic field and magnetic resistance, and the magnetic field distribution is uneven. In addition, affected by the ambient temperature, the core expands and contracts, causing the size of the gap to change, resulting in the instability of the leakage magnetic field and the temperature drift of the sensor.

[0010] 3. The magnetic cross-section of the existing iron core is rectangular, so the length of copper wire consumed to wind one turn of coil on the iron core is relatively long, and the resistance of the coil is large, resulting in high output power consumption and weak driving ability of the sensor, while limiting the matching of the subsequent control system or signal acquisition device. Summary of the invention

[0011] The object of the present invention is to provide a technical solution which can reduce magnetic leakage, lower magnetic resistance and shorten the length of the coil with the same number of turns, so as to solve the problems raised in the background technology.

[0012] To achieve the above object, the present invention provides an R-type open iron core, wherein the iron core is formed by winding a long strip of metal sheet from the inside to the outside, and an open air gap is cut at the side position of the non-winding coil, and the magnetic conductive cross section of the iron core is circular;

[0013] The metal sheet comprises a plurality of segments connected end to end, the thickness of each portion of the metal sheet is uniform and the width gradually decreases from the middle to both ends, the width of each portion within the same segment is uniform, and a transition connection segment with a gradually changing width is provided between adjacent segments, wherein the width of the middle segment is equal to the diameter of the magnetic conductive cross-section of the iron core, and the widths of the two segments symmetrically positioned about the middle segment are equal, and the length of each segment is set so as to allow a complete winding to continue on the basis of the previous winding.

[0014] The total number of all segments is an odd number, one of which is a middle segment located at the center of the metal sheet, and the remaining half of the segments are arranged on both sides of the middle segment.

[0015] Preferably, the open air gap is located in the middle of the side where it is located, and the iron core is symmetrical about the central magnetic conductive cross-section of the open air gap.

[0016] Preferably, along the direction in which the width of the metal sheet narrows, the width of each segment is set to be 2 to 4 times less than the width of the previous segment by the thickness of the metal sheet.

[0017] Preferably, along the winding direction of the metal sheet, the length of each segment is set to be 3 to 8 times the thickness of the metal sheet compared with the length of the previous segment.

[0018] Preferably, the metal sheet is a soft magnet, such as 1K107 soft magnetic alloy or 1J85 soft magnetic alloy.

[0019] Preferably, the thickness of the metal sheet is 0.1 mm to 0.5 mm.

[0020] Preferably, the width of the open air gap is 1 mm to 5 mm.

[0021] In conjunction with the use of the above-mentioned R-type open core, another object of the present invention is to improve the accuracy and performance of the Hall current sensor.

[0022] The Hall current sensor comprises an R-type open iron core, a primary bus bar, a first side compensation coil, a second side compensation coil and a Hall element;

[0023] The primary side busbar passes through the middle cavity of the iron core in the center, the Hall element is arranged at the open air gap of the iron core, the first side compensation coil and the second side compensation coil are respectively arranged on the two symmetrical sides of the iron core and are symmetrically balanced wound, and the two secondary side compensation coils are connected in series. The symmetrical balanced winding means that the first side compensation coil and the second side compensation coil are exactly opposite in position when they are wound, and the number of turns is completely equal.

[0024] Preferably, a coil frame is laid between the two secondary compensation coils and the iron core to facilitate coil wiring.

[0025] Preferably, copper foil is arranged between the two secondary compensation coils and the primary bus and insulated; specifically, the secondary compensation coil is wound after wrapping the insulating film on the coil frame, the insulating film is wrapped around the wound secondary compensation coil, and the copper foil is mounted on the surface opposite to the primary bus, and finally the copper foil is wrapped inside the insulating film.

[0026] The technical solution provided by the present invention has at least the following beneficial effects:

[0027] 1. The iron core of the present invention is formed by winding a whole metal sheet from the inside to the outside, so that there is no other joint surface in the entire magnetic circuit except the position of the open air gap, reducing the number of magnetically disconnected layers. In addition, the gaps between the metal layers are parallel to the direction of the magnetic flux lines. Therefore, the magnetic resistance and leakage of the iron core are extremely small and the magnetic field around the iron core is evenly distributed, which is conducive to improving the accuracy of the sensor.

[0028] 2. Since the circumference of a circle is the shortest under the condition of equal area, the present invention makes the magnetic cross-section of the iron core formed by winding into a circle (it can also be a regular polygon, an ellipse, an approximate circle, etc.) through the unique design of the metal sheet structure. The total length of the secondary side compensation coil is the shortest under the conditions of the same magnetic cross-sectional area and number of turns, and the coil resistance (copper resistance) is the lowest, which is beneficial to reducing the heat loss of the coil, reducing the built-in impedance and power consumption of the sensor output, and improving the output driving capability of the sensor.

[0029] 3. The present invention lays a coil skeleton between the iron core and the secondary compensation coil to facilitate coil arrangement; the two secondary compensation coils are symmetrically balanced and wound, and the same-name ends of the two are connected in series and the magnetic lines of force are in the same direction. This design greatly reduces leakage magnetic field and magnetic circuit loss and improves the accuracy of the sensor.

[0030] 4. In the present invention, the iron core is provided with only one open air gap, which can reduce the magnetic leakage and magnetic resistance of the sensor and improve the accuracy of the sensor. In addition, the corresponding Hall current sensor is provided with only one Hall element and one post-circuit part, so as to minimize the overall power consumption of the sensor.

[0031] 5. The present invention also arranges copper foil on the opposite side of the two secondary compensation coils and the primary bus respectively, and wraps it with an insulating film for insulation treatment. The copper foil is connected to the ground as the sensor PE terminal by a lead wire to shield and isolate the electromagnetic interference between the primary and secondary sides. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following briefly introduces the drawings required for describing the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative work, among which:

[0033] Figure 1 1 is a schematic structural diagram of an R-type open core in Embodiment 1 of the present invention (the cross-sectional shape of the core is shown in the figure);

[0034] Figure 2 yes Figure 1 A side cross-sectional view of the middle iron core;

[0035] Figure 3 yes Figure 1 Schematic diagram of the unfolding of the metal sheet before the middle iron core is formed;

[0036] Figure 4 yes Figure 3 Schematic diagram of the metal sheet during winding (arrow indicates the winding direction);

[0037] Figure 5 is used Figure 1 The schematic diagram of the structure of the Hall current sensor in the middle iron core;

[0038] Figure 6 yes Figure 5 Schematic diagram of the structure of the middle coil frame laid on the R-type open core (only one coil frame leaf is shown);

[0039] Figure 7 It is a structural schematic diagram of another R-type open core in the present invention (the cross-sectional shape of the core is shown in the figure);

[0040] In the figure, 1 is an R-type open iron core, 11 is a metal sheet, 12 is an open air gap, 2 is a primary side bus, 3 is a first side compensation coil, 4 is a second side compensation coil, 5 is a Hall element, 6 is a coil frame, and 7 is a copper foil. DETAILED DESCRIPTION

[0041] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0042] Embodiment 1:

[0043] See also Figures 1 to 4 An R-type open core 1 is a square frame structure with four arc-shaped chamfered edges. The R-type open core 1 is formed by winding a long strip of metal sheet 11 from inside to outside, and an open air gap 12 is cut out at the side position of the non-winding coil, and the magnetic conductive cross section of the core is circular.

[0044] The metal sheet 11 includes a plurality of segments connected end to end, the thickness of each part of the metal sheet 11 is uniform and the width gradually decreases from the middle to both ends, the width of each part in the same segment is uniform, and a transition connection section with a gradually changing width is provided between adjacent segments, wherein the width of the middle segment is equal to the diameter of the magnetic conductive cross-section of the iron core, and the widths of the two segments symmetrical about the middle segment are equal, and the length of each segment is set to allow a complete winding to continue on the basis of the previous winding.

[0045] Along the direction of narrowing the width of the metal sheet, the width of each segment is set to be 2 to 4 times less than the width of the previous segment by the thickness of the metal sheet.

[0046] Along the winding direction of the metal sheet (from one end to the other end), the length of each segment is set to be 3 to 8 times the thickness of the metal sheet more than the length of the previous segment.

[0047] In this embodiment, the material of the metal sheet 11 is 1K107 soft magnetic alloy or 1J85 soft magnetic alloy; the thickness of the metal sheet 11 is 0.1 mm to 0.5 mm.

[0048] In this embodiment, the width of the open air gap 12 is 1 mm to 5 mm and is located in the middle of the side where it is located. The cutting surface of the R-type open iron core 1 with respect to the open air gap 12 is completely symmetrical.

[0049] See also Figure 7 The R-type open core 1 can also be designed to be notched.

[0050] The iron core in this embodiment is used in the field of Hall current sensor, see Figure 5The Hall current sensor comprises an R-type open core 1, a primary bus 2, a first side compensation coil 3, a second side compensation coil 4 and a Hall element 5. The primary bus 2 is a rectangular parallelepiped and centrally passes through the middle cavity of the R-type open core 1. The primary bus 2 is made of copper or aluminum and is used to carry the measured current; the Hall element 5 is arranged at the open air gap 12 of the R-type open core 1 and is connected to the post-circuit; the first side compensation coil 3 and the second side compensation coil 4 are respectively arranged on the two symmetrical sides of the R-type open core 1 and are symmetrically balanced.

[0051] See also Figure 6 In this embodiment, a coil frame 6 is laid between the two secondary compensation coils and the R-type open core 1 to facilitate coil wiring. The complete coil frame 6 is formed by splicing two coil frame leaves, and the cavity formed in the spliced ​​frame can just accommodate the core. The two coil frame leaves are exactly the same, that is, mirror symmetric to the splicing surface.

[0052] In this embodiment, copper foil 7 is provided between the two secondary compensation coils and the primary bus 2 and is insulated; specifically, the secondary compensation coil is wound after the insulating film is wrapped on the coil frame, the insulating film is wrapped around the wound secondary compensation coil, and the copper foil is mounted on the surface opposite to the primary bus, and finally the copper foil is wrapped in the insulating film.

[0053] The Hall current sensor also includes an operational amplifier (amplifier A, input resistors R1 and R2), a compensation current power tube (VT1 and VT2) and a measuring resistor Rm, +Vc represents the positive DC power input terminal, -Vc represents the negative DC power input terminal, M represents the output terminal, PE represents the ground terminal, and GND represents the DC power supply 0V point (common point).

[0054] The same-name ends of the first side compensation coil 3 and the second side compensation coil 4 are connected in series, the lead-out end of one coil is connected to the emitter e of the compensation current power tubes VT1 and VT2, and the lead-out end of the other coil serves as the output end M of the current sensor, and the output end M is connected to the GND end (0V point) of the DC power supply through the measuring resistor Rm.

[0055] One output end of the Hall element 5 is connected in series with the resistor R1 and then connected to the in-phase input end (positive input end) of the operational amplifier, and the other output end is connected in series with the resistor R2 and then connected to the inverting input end (negative input end) of the operational amplifier; the output end of the operational amplifier is connected to the base b of the compensation current power tubes VT1 and VT2; the collector c of the compensation current power tube VT1 is connected to the positive DC power input end +Vc of the current sensor, and the collector c of the compensation current power tube VT2 is connected to the negative DC power input end -Vc of the current sensor.

[0056] The copper foil 7 is connected to the ground through a lead wire as the PE end of the sensor, which plays a role in shielding and isolating the electromagnetic interference between the primary side and the secondary side.

[0057] When designing the size of the R-type open core 1, it is designed as small as possible to be close to the primary bus 2 and to meet the insulation spacing between the primary and secondary sides of the sensor and the coil winding principle, so as to shorten the magnetic path length of the core, so that the core can obtain a higher magnetic field strength under the same number of coil turns, and thus the sensor obtains a higher signal-to-noise ratio and anti-interference ability; at the same time, this design can also reduce the magnetic circuit resistance and core iron loss, so that the sensor has higher accuracy and more stable performance.

[0058] The working process of the above Hall current sensor is as follows:

[0059] When the measured current Ip flows through the primary bus, the magnetic field generated is gathered by the R-type open iron core, and the magnetic field passes through the Hall element at the air gap of the iron core to induce a corresponding electrical signal. The electrical signal is amplified by the operational amplifier A and output to drive the compensation current power tube VT1 or VT2, thereby obtaining a compensation current Is. The compensation current Is flows through the secondary compensation coil to generate a compensation magnetic field. The compensation magnetic field is opposite to the magnetic field generated by the measured current Ip flowing through the primary bus, thereby compensating (weakening) the magnetic field of the primary side, and gradually reducing the induction output of the Hall element.

[0060] When the compensation magnetic field is equal to the primary magnetic field, the compensation current Is no longer increases. At this time, the Hall element plays the role of indicating zero magnetic flux, and Ip can be measured through Is. When Ip changes, the balance is destroyed, and the Hall element has a signal output. Repeating the above process can achieve balance again.

[0061] Since any change in the measured current will destroy this balance; once the magnetic field loses balance, the Hall element will output a signal. After amplification and driving, a corresponding current will immediately flow through the secondary compensation coil to compensate for the unbalanced magnetic field. Theoretically, the time from magnetic field imbalance to re-balance is less than 1us, forming a fast-response closed-loop control process.

[0062] The technical solution of the present invention has been applied as a system current detection component in the traction and power generation system of a railway locomotive, and is used to isolate and detect the output current of the traction and power generation system. By collecting and processing the output signal of the sensor and setting the current limiting working point, it is ensured that the output power of the power generation system will not exceed the rated power of the motor, that is, the control process of the closed-loop system and the detection and protection purpose are realized.

[0063] In actual applications, it is found that when sampling and comparing the magnetic flux density under the same magnetic field strength and magnetic conductive material conditions, the C-type iron core is on average only 89.47% of the R-type open iron core in the present invention. It can be seen that the leakage magnetic flux of the R-type open iron core of the present invention is much smaller than that of the traditional C-type iron core, thereby achieving higher accuracy of the Hall sensor and not causing large temperature drift.

[0064] In addition, the copper resistance (internal resistance) of the secondary compensation coil is the smallest under the same magnetic cross-sectional area, the power consumption of the Hall sensor is reduced, the driving ability is enhanced, the matching with the subsequent system is expanded, and the temperature drift is small. The copper foil set significantly enhances the anti-interference ability of the Hall sensor screen.

[0065] The above description is only a preferred embodiment of the present invention, and does not limit the scope of patent protection of the present invention. For those skilled in the art, the present invention may have various modifications and changes. Within the spirit and principle of the present invention, any improvement or equivalent replacement made by using the contents of the present invention specification and drawings, directly or indirectly applied in other related technical fields, shall be included in the scope of patent protection of the present invention.

Claims

1. A Hall current sensor, characterized in that: It includes a primary side bus, a primary side compensation coil, a secondary side compensation coil and a Hall element; The primary busbar passes through the middle cavity of the iron core in the middle, the Hall element is arranged at the open air gap of the iron core, the primary compensation coil and the secondary compensation coil are respectively arranged on the two symmetrical sides of the iron core and are symmetrically balanced and wound, and the two secondary compensation coils are connected in series; A coil frame is laid between the two secondary compensation coils and the iron core to facilitate coil wiring; Copper foil is arranged between the two secondary compensation coils and the primary busbar and insulation treatment is performed; specifically, the secondary compensation coil is wound after the insulation film is wrapped on the coil frame, the insulation film is wrapped outside the wound secondary compensation coil, and the copper foil is mounted on the surface opposite to the primary busbar, and finally the copper foil is wrapped inside the insulation film; The iron core is an R-type open iron core; the iron core is formed by winding a long strip of metal sheet from the inside to the outside, and an open air gap is cut at the side position of the non-winding coil, and the magnetic conductive cross section of the iron core is circular; The metal sheet comprises a plurality of segments connected end to end, the thickness of each part of the metal sheet is equal and the width gradually decreases from the middle to the two ends, the width of each part in the same segment is equal, and a transition connection section with a gradually changing width is provided between adjacent segments, wherein the width of the middle segment is equal to the diameter of the magnetic conductive cross section of the iron core, and the widths of the two segments symmetrically located about the middle segment are equal, and the length of each segment is set to allow a complete winding to continue on the basis of the previous winding; The metal sheet is a soft magnet; The thickness of the metal sheet is 0.1 mm to 0.5 mm.

2. The Hall current sensor according to claim 1, characterized in that: Along the direction of narrowing the width of the metal sheet, the width of each segment is set to be 2 to 4 times less than the width of the previous segment by the thickness of the metal sheet.

3. The Hall current sensor according to claim 2, characterized in that: Along the winding direction of the metal sheet, the length of each segment is set to be 3 to 8 times the thickness of the metal sheet compared to the length of the previous segment.

4. The Hall current sensor according to claim 3, characterized in that: The width of the open air gap is 1 mm to 5 mm.

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