A Z-shaped anti-magnetic bridge air-gap magnetic core and its working method

Abstract

The present invention discloses a Z-shaped anti-magnetic bridge air-gap magnetic core and its working method. The magnetic core includes a magnetic core body, and a gap is formed on the magnetic core body. A Z-shaped anti-magnetic bridge for connecting both ends of the gap of the magnetic core body is arranged in the gap. A first air gap and a second air gap are respectively formed between the Z-shaped anti-magnetic bridge and the magnetic core bodies on both sides. The included angle between the middle bridge arm and the two side bridge arms of the Z-shaped anti-magnetic bridge is an acute angle. By adopting the structure of the Z-shaped anti-magnetic bridge, the existence of the magnetic bridge ensures the integrity of the magnetic core. At the same time, because there is a reverse magnetic field inside the magnetic bridge, the problems of magnetic saturation and heating of the magnetic bridge caused by large-current excitation are overcome.

Description

Technical Field

[0001] The invention belongs to the technical field of magnetic cores, and in particular relates to a Z-shaped reverse magnetic bridge air gap magnetic core and a working method thereof. Background Art

[0002] The core of the open-loop Hall current sensor is usually made of FeSi (silicon steel), FeNi (Permalloy), and ferromagnetic soft magnetic materials such as amorphous or nanocrystalline, which are rolled or stamped. With the rapid development of electric vehicles, the demand for on-board high-current sensors is growing rapidly. However, due to the limitation of saturation flux density of soft magnetic materials themselves, how to make low-cost, wide linear range, and high-sensitivity current sensor cores in high-current application scenarios is not only a technical problem that needs to be overcome for high-current sensors, but also a major issue faced by the electric vehicle industry.

[0003] The basic principle of the current sensor is: according to the law of electromagnetic induction, the electrical signal of the measured current is converted into a proportional magnetic signal (magnetic field) through a magnetic core (hereinafter referred to as the magnetic core), and then the magnetic signal is converted into an electrical signal through a magnetic sensitive chip such as Holl (or TMR, AMR, GMR) and outputs a proportional voltage value. After the voltage value is collected, it is converted and converted to obtain the current value. However, when the measured current value is large, the magnetic field inside the magnetic core will tend to saturation, and the magnetic flux density cannot increase proportionally with the increase of current, and the linearity tends to decrease rapidly with the increase of current, resulting in a decrease in the measurement accuracy of the large current end.

[0004] In view of the above problems, the solutions in the prior art are: ① increasing the circumference of the magnetic core (ie, the length of the magnetic path); ② increasing the width of the air gap of the magnetic core; ③ increasing the number of air gaps, for example, using a double air gap magnetic core.

[0005] However, solution ① is limited by the installation space and is difficult to implement in practice.

[0006] In case ②, increasing the width of the air gap can indeed increase the magnetic resistance of the magnetic circuit, thereby reducing the maximum magnetic flux density inside the magnetic core, and then delaying the arrival of the magnetic saturation point, achieving a wider linear threshold, and improving the detection linearity of large currents within a certain range. However, the shortcomings and limitations of this method are also very obvious: first, increasing the width of the air gap will reduce the magnetic flux density inside the magnetic core, thereby reducing the resolution and detection accuracy of the current sensor, which is especially not conducive to accurate measurement of small current ends; secondly, the leakage flux of the magnetic core will increase with the increase of the air gap, and a larger proportion of leakage flux will be generated under large currents. Therefore, the effect of improving the detection linearity of large currents by simply increasing the air gap is limited. In fact, when this method is used for large current detection above 800A, its linearity is often not satisfactory.

[0007] When the measured current is greater than 800 A, a distributed air-gap magnetic core is usually used as a magnetic flux collection means (Scheme ③) to obtain relatively satisfactory measurement accuracy. In Scheme ③, two smaller air gaps are used to replace a single large air gap, which not only ensures that the magnetic core has a wide linear range, but also reduces the leakage magnetic flux due to the narrowing of the air gap, thereby reducing the reduction amplitude of the magnetic core sensitivity. However, the disadvantage of the existing double-air-gap magnetic core is that the magnetic core is cut into two unconnected parts, the structure of the current sensor becomes complex, the relatively high manufacturing cost and the large volume structure are difficult to be accepted by in-vehicle users, etc. Therefore, this scheme is only applied in the power industry. Summary of the Invention

[0008] Object of the Invention:

[0009] In order to overcome the problems existing in the prior art, the present invention provides a Z-shaped anti-magnetic bridge air-gap magnetic core and its working method, adopting the structure of the Z-shaped anti-magnetic bridge. The existence of the magnetic bridge ensures the integrity of the magnetic core, and at the same time, because there is a reverse magnetic field inside the magnetic bridge, the problems of magnetic saturation and heating of the magnetic bridge caused by large-current excitation are overcome.

[0010] To solve the above problems, the present invention adopts the following technical solutions:

[0011] A Z-shaped anti-magnetic bridge air-gap magnetic core includes a magnetic core body. A gap is provided on the magnetic core body, and a Z-shaped anti-magnetic bridge for connecting both ends of the gap of the magnetic core body is arranged in the gap. A first air gap and a second air gap are respectively formed between the Z-shaped anti-magnetic bridge and the magnetic core bodies on both sides. The included angle between the middle bridge arm and the two side bridge arms of the Z-shaped anti-magnetic bridge is an acute angle.

[0012] The main inventive point of the present invention lies in the design that the included angle between the middle bridge arm and the two side bridge arms of the magnetic bridge is an acute angle, forming a Z-shaped anti-magnetic bridge. The function of the first air gap and the second air gap for adjusting the magnetic density is to utilize the constant air and the magnetic conductivity characteristics far lower than those of the soft magnetic material to reduce the main magnetic flux density of the magnetic circuit and avoid the magnetic saturation phenomenon of the magnetic core. One function of the Z-shaped anti-magnetic bridge in terms of structure is to connect the magnetic core into a whole, and the magnetic core is not divided into two parts due to the existence of the air gap. The design of using an acute angle to form the anti-magnetic bridge ensures that no matter what the direction of the measured current is, the component H1 of the main magnetic flux H along the direction of the magnetic bridge is opposite to the magnetic conduction direction of the magnetic core. Since the net magnetic field H1 = Hcosα at the connection part of the Z-shaped anti-magnetic bridge is opposite to the magnetic bridge path with high magnetic permeability, the magnetic flux passing through it must be inhibited by the main magnetic flux. Therefore, the Z-shaped anti-magnetic bridge will not undergo magnetic saturation even under large-current excitation.

[0013] Therefore, the above Z-shaped anti-magnetic bridge ensures the overall structure of the magnetic core on the premise that magnetic saturation does not occur at the connection part.

[0014] Preferably, the angle between the middle bridge arm and the two side bridge arms of the Z-shaped anti-magnetic bridge is 45°. Since the net magnetic field H1 = Hcosα at the connection part of the Z-shaped anti-magnetic bridge, 45° is a better choice.

[0015] Preferably, the magnetic core body is square-ring-shaped, and the gap is opened in the middle of one of the four columns of the magnetic core body.

[0016] Preferably, the first air gap and the second air gap are centrosymmetric with the Z-shaped anti-magnetic bridge as the center.

[0017] Preferably, the magnetic core body is also provided with a measuring air gap, which is arranged in the middle of one of the four columns of the magnetic core body opposite to the column where the gap is opened. The measuring position air gap G3 is used to insert chips such as Hall, TMR, GMR, and AMR. The width of the air gap should be such that the chips can be inserted. To prevent magnetic leakage, it is advisable to be narrow rather than wide.

[0018] Preferably, the magnetic core body 1 is made of soft magnetic material by rolling or laminating.

[0019] Preferably, the widths of the first air gap and the second air gap are equal, both between 3 mm and 4 mm.

[0020] The present invention also discloses a working method of the Z-shaped anti-magnetic bridge air gap magnetic core as described above, including the following steps:

[0021] S1. Select a corresponding Z-shaped anti-magnetic bridge air gap magnetic core according to the magnitude of the measured current;

[0022] S2. Install the magnetic core on the corresponding open-loop Hall current sensor, insert a Hall, TMR, GMR, or AMR chip into the measuring air gap, and install the Hall current sensor in the corresponding circuit;

[0023] S3. When the circuit is working, the Hall current sensor measures the circuit current. When the measured current I passes through the magnetic core window, an induced magnetic field with a magnetic field intensity of H will be generated inside the magnetic core. Since the angle between the middle bridge arm and the two side bridge arms of the Z-shaped anti-magnetic bridge is an acute angle, the net magnetic field H1 = Hcosα at the connection part of the Z-shaped anti-magnetic bridge, and the direction is opposite to the magnetic bridge path with high magnetic permeability. Therefore, when the measured current I passes through the magnetic core window, it can suppress the magnetic flux passing through it, and magnetic saturation will not occur even under the excitation of a large current.

[0024] Preferably, when the measured current reaches 1000 A, a Z-shaped anti-magnetic bridge air-gap magnetic core with the widths of the first air-gap and the second air-gap both being 3 mm is selected; when the measured current reaches 1500 A, a Z-shaped anti-magnetic bridge air-gap magnetic core with the widths of the first air-gap and the second air-gap both being 3.5 mm is selected; when the measured current reaches 2000 A, a Z-shaped anti-magnetic bridge air-gap magnetic core with the widths of the first air-gap and the second air-gap both being 4 mm is selected.

[0025] Beneficial effects: Compared with the prior art, the present invention has the following advantages: By adopting the structure of a Z-shaped anti-magnetic bridge, the existence of the magnetic bridge ensures the integrity of the magnetic core. At the same time, because there is a reverse magnetic field inside the magnetic bridge, the problems of magnetic saturation and heating of the magnetic bridge caused by large-current excitation are overcome. Description of the Drawings

[0026] Figure 1 is the plan view of Comparative Example 1 of the present invention;

[0027] Figure 2 is the plan view of Comparative Example 2 of the present invention;

[0028] Figure 3 is the plan view of the present invention;

[0029] Figure 4 is the result diagram of the excitation test of the present invention. Detailed Embodiments

[0030] All the features disclosed in this specification, or all the steps in any disclosed method or process, except for mutually exclusive features and / or steps, can be combined in any manner.

[0031] Any feature disclosed in this specification (including any additional claims, abstract, and drawings) can be replaced by other equivalent or similar-purpose alternative features unless specifically stated otherwise. That is, unless specifically stated otherwise, each feature is only an example of a series of equivalent or similar features.

[0032] To make the above objects, features, and advantages of the present invention more obvious and understandable, the following detailed description of the specific embodiments of the present invention is made in conjunction with the drawings.

[0033] As Figures 1-4 shown, in the first embodiment of the present invention, a Z-shaped anti-magnetic bridge air-gap magnetic core includes a magnetic core body 1. A gap is formed on the magnetic core body, and a Z-shaped magnetic bridge 2 for connecting both ends of the gap of the magnetic core body is arranged in the gap. First air-gap 31 and second air-gap 32 are respectively formed between the Z-shaped magnetic bridge 2 and the magnetic core bodies 1 on both sides. The included angle between the middle bridge arm and the two side bridge arms of the Z-shaped magnetic bridge 2 is an acute angle.

[0034] The main inventive point of the present invention lies in the design where the angle between the middle bridge arm and the two side bridge arms of the magnetic bridge is an acute angle, forming a Z-shaped anti-magnetic bridge. The function of the magnetic flux density adjusting the first air gap and the second air gap is to utilize the constant air and its magnetic permeability far lower than that of the soft magnetic material to reduce the main magnetic flux density of the magnetic circuit and avoid the phenomenon of magnetic core magnetic saturation. One function of the Z-shaped anti-magnetic bridge in terms of structure is to connect the magnetic cores into a whole, without dividing the magnetic cores into two parts due to the existence of the air gap. The design of using an acute angle to form the anti-magnetic bridge ensures that no matter what the direction of the measured current is, the component H1 of the main magnetic flux H along the direction of the magnetic bridge is opposite to the magnetic conduction direction of the magnetic core. Since the net magnetic field H1 = Hcosα at the connecting part of the Z-shaped anti-magnetic bridge and its direction is opposite to the magnetic bridge path with high magnetic permeability, the magnetic flux passing through it must be inhibited by the main magnetic flux. Therefore, the Z-shaped anti-magnetic bridge will not undergo magnetic saturation even under the excitation of a large current.

[0035] In this embodiment, the angle between the middle bridge arm and the two side bridge arms of the Z-shaped magnetic bridge 2 is 45°. Since the net magnetic field H1 = Hcosα at the connecting part of the Z-shaped anti-magnetic bridge, 45° is a preferred choice.

[0036] In this embodiment, the magnetic core body 1 is square-ring-shaped, and the gap is opened in the middle of one of the four columns of the magnetic core body.

[0037] In this embodiment, the first air gap 31 and the second air gap 32 are centrosymmetric with the Z-shaped magnetic bridge 2 as the center.

[0038] In this embodiment, the magnetic core body 1 is further provided with a measurement air gap 4. The measurement air gap 4 is arranged in the middle of one of the four columns of the magnetic core body opposite to the column where the gap is opened. The measurement position air gap G3 is used to insert chips such as Hall, TMR, GMR, and AMR. The width of its air gap should be such that the chips can be inserted. To prevent magnetic leakage, it is preferably narrow rather than wide.

[0039] In this embodiment, the magnetic core body 1 is made of soft magnetic material by rolling or laminating, and it is preferably made by laminating.

[0040] In this embodiment, the widths of the first air gap and the second air gap are equal, both being between 3 mm and 4 mm.

[0041] To verify the magnetic saturation suppression effect of the Z-shaped anti-magnetic bridge, three different magnetic core magnetic bridge structures are respectively used for experiments, as shown in Figure 1 、 2 、3 respectively. Figure 1 It is Comparative Example 1 of conventionally increasing the width of the magnetic core air gap. Figure 2 It is Comparative Example 2 of a paramagnetic bridge with double air gaps. Figure 3This is a specific embodiment of the present invention, and the specific parameters are as follows: the length of the magnetic core window is 24 mm, the width is 11.2 mm, the widths of the first air gap and the second air gap are both 3 mm, the thickness of the magnetic core body is 5 mm, the average magnetic path length is 90.4 mm, the number of turns of the wire is 1 turn, the measured air gap width is 1.5 mm, the cross-sectional area of the magnetic core is 23.6, and the maximum current is 1000 A.

[0042] Under the magnetization field strength of 15000 A / m of the excitation current, a temperature rise comparison test was carried out on the above three magnetic core results through an infrared imager, and the specific test results are shown in the following table:

[0043]

[0044] Let T1 represent the temperature rise value of Comparative Example 1, T2 represent the temperature rise value of Comparative Example 2, and T3 represent the temperature rise value of Example 1. It was found that the order of the temperature rise values was: T1 > T2 > T3, and the values of T1 and T2 at the high-current end were significantly higher than T3. And it was confirmed that even at the high-current end, the temperature rise value of the Z-shaped anti-magnetic bridge was similar to that of the magnetic core body. This shows that under high-current magnetization, both the conventional magnetic bridge and the Z-shaped paramagnetic bridge have different degrees of magnetic saturation phenomenon, while the Z-shaped anti-magnetic bridge does not have the problem of magnetic saturation.

[0045] In a further test, a conventional excitation test was also carried out on the magnetic core structure in Example 1. The maximum excitation current was 1000 A and the frequency was 50 Hz. At different excitation currents, a Gauss meter (model: Japanese kanetec TM-801EXP) was used to test the data of the magnetic flux density B of the corresponding magnetic core after excitation (the probe was placed at the center point of the detection air gap). The specific test results are as Figure 4 shown. The results show that under the excitation of a large current of 1000 A, the Z-shaped anti-magnetic bridge air gap magnetic core of the present invention shows a linear relationship between the magnetic flux density B and the current intensity I from a small current to the peak current, and its linearity reaches the level of R2 = 1, and it also has good linearity when detecting a large current of 1000 A.

[0046] In the second embodiment of the present invention, the widths of the first air gap and the second air gap are equal to 3.5 mm, and the corresponding excitation current can reach 1500 A.

[0047] In the third embodiment of the present invention, the widths of the first air gap and the second air gap are equal to 4.0 mm, and the corresponding excitation current can reach 2000 A.

[0048] Compared with the first embodiment, the specific parameters only need to adjust the window size of the magnetic core to the size of the copper bar suitable for the corresponding current requirement.

[0049] Due to the aforementioned characteristics of the Z-shaped anti-magnetic bridge air-gap core and its good performance in large current detection, it is very suitable for application scenarios that require low cost, small size, compact structure, large current, etc. Such as electric vehicles, high-speed rails, new energy power transmission and distribution equipment or energy storage systems, as well as industrial equipment and other fields.

[0050] The raw materials of the core involved in the present invention can be ferromagnetic soft magnetic materials such as FeSi (silicon steel), FeNi (Permalloy), amorphous or nanocrystalline.

[0051] The widths of the first air gap and the second air gap of the core can be adjusted according to the magnitude of the current. The principle is to take a relatively small air gap width value as much as possible on the premise of ensuring that magnetic saturation does not occur at the large current end, so as to improve the sensitivity of the core.

[0052] The present invention also discloses a working method of the above-mentioned Z-shaped anti-magnetic bridge air-gap core, including the following steps:

[0053] S1. Select a corresponding Z-shaped anti-magnetic bridge air-gap core according to the magnitude of the measured current;

[0054] S2. Install the core on the corresponding open-loop Hall current sensor, insert a Hall, TMR, GMR or AMR chip in the measurement air gap, and install the Hall current sensor in the corresponding circuit;

[0055] S3. When the circuit is working, the Hall current sensor measures the circuit current. When the measured current I passes through the core window, an induced magnetic field with a magnetic field intensity of H will be generated inside the core. Since the angle between the middle bridge arm and the two side bridge arms of the Z-shaped magnetic bridge is an acute angle, the net magnetic field H1 = Hcosα at the connection part of the Z-shaped anti-magnetic bridge, and the direction is opposite to the magnetic bridge path with high magnetic permeability. Therefore, when the measured current I passes through the core window, it can suppress the magnetic flux passing through it, and magnetic saturation will not occur even under the condition of large current excitation.

[0056] When the measured current reaches 1000 A, select a Z-shaped anti-magnetic bridge air-gap core with the widths of the first air gap and the second air gap both being 3 mm; when the measured current reaches 1500 A, select a Z-shaped anti-magnetic bridge air-gap core with the widths of the first air gap and the second air gap both being 3.5 mm; when the measured current reaches 2000 A, select a Z-shaped anti-magnetic bridge air-gap core with the widths of the first air gap and the second air gap both being 4 mm.

[0057] The present invention also discloses an open-loop Hall current sensor, including the above-mentioned Z-shaped anti-magnetic bridge air-gap core.

[0058] The purpose of the above embodiments is to exemplarily reproduce and deduce the technical solution of the present invention, and to completely describe the technical solution, purpose and effect of the present invention. The purpose is to enable the public to understand the disclosed content of the present invention more thoroughly and comprehensively, and it does not limit the protection scope of the present invention.

[0059] The above embodiments are not an exhaustive list based on the present invention. In addition, there may be multiple other embodiments not listed. Any substitution and improvement made on the basis of not violating the concept of the present invention fall within the protection scope of the present invention.

Claims

1. A Z-shaped reverse magnetic bridge air gap magnetic core, characterized in that: The invention comprises a magnetic core body (1), wherein a gap is provided on the magnetic core body, wherein a Z-shaped anti-magnetic bridge (2) is provided in the gap for connecting the two ends of the gap of the magnetic core body, wherein a first air gap (31) and a second air gap (32) are respectively formed between the Z-shaped anti-magnetic bridge (2) and the magnetic core body (1) on both sides, wherein the angle between the middle bridge arm of the Z-shaped anti-magnetic bridge (2) and the bridge arms on both sides is an acute angle, wherein the magnetic core body (1) is in a square ring shape, wherein the gap is provided in the middle of one of the four columns of the magnetic core body, and wherein the magnetic core body (1) is further provided with a measuring air gap (4), wherein the measuring air gap (4) is provided in the middle of one of the four columns of the magnetic core body which is opposite to the column in which the gap is provided.

2. A Z-shaped inverse magnetic bridge air gap core according to claim 1, characterized in that: The angle between the middle bridge arm and the bridge arms on both sides of the Z-shaped anti-magnetic bridge (2) is 45°.

3. A Z-shaped inverse magnetic bridge air gap magnetic core according to claim 1, characterized in that: The first air gap (31) and the second air gap (32) are centrally symmetrical with the Z-shaped anti-magnetic bridge (2) as the center.

4. A Z-shaped inverse magnetic bridge air gap magnetic core according to claim 1, characterized in that: The magnetic core body (1) is made of soft magnetic material through rolling or lamination.

5. The Z-shaped inverse magnetic bridge air gap core according to claim 1, characterized in that: The widths of the first air gap and the second air gap are equal, both ranging from 3 mm to 4 mm.

6. A method for operating the Z-shaped reverse magnetic bridge air gap core as claimed in any one of claims 1 to 5, characterized in that: The following steps are involved: S1. Select the corresponding Z-shaped anti-magnetic bridge air gap core according to the current being measured; S2. Install the magnetic core on the corresponding open-loop Hall current sensor, insert the Hall, TMR, GMR or AMR chip in the measuring air gap, and install the Hall current sensor in the corresponding circuit; S3. When the circuit is working, the Hall current sensor measures the circuit current. When the measured current I passes through the core window, an induced magnetic field with a magnetic field strength of H will be generated inside the core. Since the angle α between the middle bridge arm of the Z-shaped anti-magnetic bridge and the bridge arms on both sides is an acute angle, the net magnetic field H1 of the middle bridge arm of the Z-shaped anti-magnetic bridge is equal to Hcosα, and the direction of the net magnetic field H1 is opposite to the magnetic bridge path of the high magnetic permeability of the middle bridge arm of the Z-shaped anti-magnetic bridge. Therefore, when the measured current I passes through the core window, the magnetic flux passing therethrough can be suppressed, and magnetic saturation will not occur under the condition of large current excitation.

7. A method for operating a Z-shaped reverse magnetic bridge air gap core according to claim 6, characterized in that: When the measured current reaches 1000A, select a Z-shaped anti-magnetic bridge air gap core with a first air gap and a second air gap width of 3mm; when the measured current reaches 1500A, select a Z-shaped anti-magnetic bridge air gap core with a first air gap and a second air gap width of 3.5mm; when the measured current reaches 2000A, select a Z-shaped anti-magnetic bridge air gap core with a first air gap and a second air gap width of 4mm.

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