A method and apparatus for permeability evaluation
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- BAOTOU INST MAGNETIC NEW MATERIALS CO LTD
- Filing Date
- 2023-12-20
- Publication Date
- 2026-07-21
Smart Images
Figure CN117491923B_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of magnet technology, and more specifically to a method and apparatus for evaluating magnetic permeability. Background Technology
[0002] Permanent magnets are widely used in various industries because they retain their magnetism for a long time after being magnetized. Most permanent magnets are very sensitive to temperature; in practical applications, the impact of high temperatures on magnetism needs to be carefully assessed, as improper assessment can lead to significant losses.
[0003] Using permeability coefficient in conjunction with high-temperature demagnetization curves is a relatively common and effective evaluation method. However, the calculation of permeability coefficient is currently limited to rectangular and circular permanent magnets in the open circuit state. For other shapes (such as the tile shape which is widely used in motors) and other magnetic circuit states (permanent magnets in motors are almost always used in conjunction with magnetic cores, rather than in the open circuit state), it is currently impossible to quickly and effectively calculate their permeability coefficient values.
[0004] There is currently a method for determining the permeability coefficient, patent publication number CN113126008A. Its core technology is to use a relatively simple formula to determine the remanent magnetic induction intensity and magnetic coercivity values at two temperatures, as well as the demagnetization rate of the permanent magnet as it rises from the first temperature to the second temperature and then returns to the first temperature. The permeability coefficient value is then calculated using the formula. The premise of this formula is that the recovery permeability of the permanent magnet is the same at the two temperatures. However, in reality, they are unlikely to be the same. Moreover, there is a trend that the larger the temperature difference, the greater the difference in recovery permeability. Furthermore, the squareness of the demagnetization curve required by the patent to be greater than or equal to 0.95 does not constrain this problem. Summary of the Invention
[0005] In view of this, the purpose of the present invention is to provide a method and apparatus for evaluating the permeability coefficient, so as to solve the problem that the permeability coefficient value of permanent magnets cannot be evaluated quickly and effectively in the prior art.
[0006] According to a first aspect of the present invention, a method for evaluating magnetic permeability is provided, comprising:
[0007] The BH demagnetization curve and the first magnetic moment value of the target permanent magnet at the first temperature are measured. Based on the BH demagnetization curve at the first temperature, the recovery permeability of the target permanent magnet at the first temperature is obtained.
[0008] The first temperature is raised to the second temperature, and the BH demagnetization curve of the target permanent magnet is measured at the second temperature. Based on the BH demagnetization curve at the second temperature, the second remanence value of the target permanent magnet at the second temperature is obtained.
[0009] When the second temperature drops back to the first temperature, the second magnetic moment value of the target permanent magnet is measured.
[0010] Based on the first magnetic moment value, the second magnetic moment value, the second remanence value, and the restored permeability, a virtual BH demagnetization curve is obtained;
[0011] The permeability value is obtained based on the virtual BH demagnetization curve and the BH demagnetization curve at the second temperature.
[0012] Preferably, the step of deriving the virtual BH demagnetization curve based on the first magnetic moment value, the second magnetic moment value, the second remanence value, and the recovering permeability includes:
[0013] Based on the first magnetic moment value, the second magnetic moment value, and the second remanence value, the intrinsic remanence value of the target permanent magnet at the second temperature is calculated.
[0014] Based on the intrinsic remanence and the recovery permeability, a virtual BH demagnetization curve is obtained.
[0015] Preferably, the calculation of the intrinsic remanence of the target permanent magnet at the second temperature includes:
[0016] Based on the second magnetic moment value and the first magnetic moment value, the irreversible decay rate of the target permanent magnet after the first temperature is increased to the second temperature is calculated;
[0017] Based on the irreversible decay rate and the second remanence value, the intrinsic remanence value of the target permanent magnet at the second temperature is calculated.
[0018] Preferably, the step of obtaining the permeability value based on the virtual BH demagnetization curve and the BH demagnetization curve at the second temperature includes:
[0019] The intersection point of the virtual BH demagnetization curve and the BH demagnetization curve at the second temperature is obtained, and the coordinate value of the intersection point is obtained.
[0020] The magnetic permeability value is obtained based on the coordinates of the intersection point.
[0021] Preferably, the calculation of the irreversible decay rate of the target permanent magnet after the first temperature is increased to the second temperature includes:
[0022] The irreversible decay rate is calculated using the following formula:
[0023]
[0024] Where Loss is the irreversible decay rate, M2 is the second magnetic moment value, and M1 is the first magnetic moment value.
[0025] Preferably, the calculation of the intrinsic remanence of the target permanent magnet at the second temperature includes:
[0026] The intrinsic remanence at the second temperature is calculated using the following formula:
[0027] Br3 = Br2 × (1 - Loss)
[0028] Wherein, Br3 is the intrinsic remanence value at the second temperature, and Br2 is the second remanence value.
[0029] Preferably, the step of deriving the permeability value based on the coordinates of the intersection point includes:
[0030] The permeability value is calculated using the following formula:
[0031]
[0032] Where Pc is the permeability coefficient, By is the ordinate of the intersection point, and Hx is the abscissa of the intersection point.
[0033] According to a second aspect of the present invention, a magnetic permeability evaluation device is provided, comprising:
[0034] The main controller and the memory connected to the main controller;
[0035] The memory stores program instructions;
[0036] The main controller is used to execute program instructions stored in the memory and perform any of the methods described above.
[0037] The technical solutions provided by the embodiments of the present invention may include the following beneficial effects:
[0038] It is understood that the technical solution shown in this invention can measure the BH demagnetization curve and the first magnetic moment value of the target permanent magnet at a first temperature, and obtain the restoring permeability of the target permanent magnet at the first temperature; raise the first temperature to a second temperature, measure the BH demagnetization curve of the target permanent magnet at the second temperature, and obtain the second remanence value of the target permanent magnet at the second temperature; when the second temperature drops back to the first temperature, measure the second magnetic moment value of the target permanent magnet; based on the first magnetic moment value, the second magnetic moment value, the second remanence value, and the restoring permeability, obtain a virtual BH demagnetization curve, and finally obtain the permeability value. It is understood that the technical solution shown in this invention can accurately evaluate the permeability of the target permanent magnet without being limited by the shape and magnetic circuit state of the permanent magnet.
[0039] It should be understood that the above general description and the following detailed description are exemplary and explanatory only, and are not intended to limit the invention. Attached Figure Description
[0040] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with the invention and, together with the description, serve to explain the principles of the invention.
[0041] Figure 1 This is a schematic diagram illustrating the steps of a method for evaluating magnetic permeability according to an exemplary embodiment;
[0042] Figure 2 This is a coordinate graph of the BH demagnetization curve according to an exemplary embodiment;
[0043] Figure 3 These are demagnetization curves for numbers 1, 2, 4, and 5, shown according to an exemplary embodiment.
[0044] Figure 4 This is a demagnetization curve diagram, number 3, shown according to an exemplary embodiment. Detailed Implementation
[0045] Exemplary embodiments will now be described in detail, examples of which are illustrated in the accompanying drawings. When the following description relates to the drawings, unless otherwise indicated, the same numerals in different drawings denote the same or similar elements. The embodiments described in the following exemplary embodiments do not represent all embodiments consistent with the present invention. Rather, they are merely examples of apparatuses and methods consistent with some aspects of the invention as detailed in the appended claims.
[0046] Example 1
[0047] Figure 1 This is a schematic diagram illustrating the steps of a method for evaluating magnetic permeability according to an exemplary embodiment. See also: Figure 1 A method for evaluating magnetic permeability is provided, comprising:
[0048] Step S11: Measure the BH demagnetization curve and the first magnetic moment value of the target permanent magnet at the first temperature. Based on the BH demagnetization curve at the first temperature, obtain the recovery permeability of the target permanent magnet at the first temperature.
[0049] Step S12: Raise the first temperature to the second temperature, measure the BH demagnetization curve of the target permanent magnet at the second temperature, and obtain the second remanence value of the target permanent magnet at the second temperature based on the BH demagnetization curve at the second temperature.
[0050] Step S13: When the second temperature drops back to the first temperature, measure the second magnetic moment value of the target permanent magnet;
[0051] Step S14: Based on the first magnetic moment value, the second magnetic moment value, the second remanence value, and the restored permeability, derive the virtual BH demagnetization curve;
[0052] Step S15: Based on the virtual BH demagnetization curve and the BH demagnetization curve at the second temperature, the permeability value is obtained.
[0053] It is understood that the technical solution shown in this invention can measure the BH demagnetization curve and the first magnetic moment value of the target permanent magnet at a first temperature, and obtain the restoring permeability of the target permanent magnet at the first temperature; raise the first temperature to a second temperature, measure the BH demagnetization curve of the target permanent magnet at the second temperature, and obtain the second remanence value of the target permanent magnet at the second temperature; when the second temperature drops back to the first temperature, measure the second magnetic moment value of the target permanent magnet; based on the first magnetic moment value, the second magnetic moment value, the second remanence value, and the restoring permeability, obtain a virtual BH demagnetization curve, and finally obtain the permeability value. It is understood that the technical solution shown in this invention can accurately evaluate the permeability of the target permanent magnet without being limited by the shape and magnetic circuit state of the permanent magnet.
[0054] In practical application, see Figure 2 This illustrates a specific example where the first temperature is 20 degrees Celsius (room temperature) and the second temperature is 123 degrees Celsius. Figure 2 The curves at 20 degrees Celsius, 123 degrees Celsius, the BH demagnetization curve at 20 degrees Celsius, the BH demagnetization curve at 123 degrees Celsius, and the dashed line represents the virtual BH demagnetization curve.
[0055] In step S11, the target permanent magnet is measured to obtain the BH demagnetization curve and the first magnetic moment value M1 under the 20-degree Celsius curve. From the BH demagnetization curve under the 20-degree Celsius curve, the recovery permeability of the target permanent magnet at the first temperature can be obtained: the magnetic coercivity value Hcb1 = 12.68 kOe, so the recovery permeability μ1 = Br1 / Hcb1 = 13.18 / -12.68 = -1.039, where Br1 is the first remanence value.
[0056] Then, in step S12, the temperature is increased from 20 degrees Celsius to 123 degrees Celsius, thereby obtaining... Figure 2 The BH demagnetization curve under the 123°C curve is used to obtain the second remanence value Br2 of the target permanent magnet at the second temperature.
[0057] When the second temperature drops back to the first temperature, the second magnetic moment value of the target permanent magnet is measured.
[0058] It should be noted that, in step S14, the process of deriving the virtual BH demagnetization curve based on the first magnetic moment value, the second magnetic moment value, the second remanence value, and the recovering permeability includes:
[0059] Based on the first magnetic moment value, the second magnetic moment value, and the second remanence value, the intrinsic remanence value of the target permanent magnet at the second temperature is calculated.
[0060] Based on the intrinsic remanence and the recovery permeability, a virtual BH demagnetization curve is obtained.
[0061] It should be noted that the calculation of the intrinsic remanence of the target permanent magnet at the second temperature includes:
[0062] Based on the second magnetic moment value and the first magnetic moment value, the irreversible decay rate of the target permanent magnet after the first temperature is increased to the second temperature is calculated;
[0063] Based on the irreversible decay rate and the second remanence value, the intrinsic remanence value of the target permanent magnet at the second temperature is calculated.
[0064] It should be noted that the calculation of the irreversible decay rate of the target permanent magnet after the first temperature is increased to the second temperature includes:
[0065] The irreversible decay rate is calculated using the following formula:
[0066]
[0067] Where Loss is the irreversible decay rate, M2 is the second magnetic moment value, and M1 is the first magnetic moment value.
[0068] In the example above, assuming that the first magnetic moment value M1 measured at room temperature of 20 degrees Celsius is 10 mWbcm, and after being baked at a high temperature of 123 degrees Celsius for 2 hours and then cooled to room temperature, the second magnetic moment value M2 measured later is 8.8 mWb·cm, then the irreversible decay rate is 12%.
[0069] It should be noted that the calculation of the intrinsic remanence of the target permanent magnet at the second temperature includes:
[0070] The intrinsic remanence at the second temperature is calculated using the following formula:
[0071] Br3 = Br2 × (1 - Loss)
[0072] Wherein, Br3 is the intrinsic remanence value at the second temperature, and Br2 is the second remanence value.
[0073] In the example above, from Figure 2 From this, we can derive Br2 as 11.71 kGs, and the intrinsic remanence Br3 = 11.71 * (1 - 12%) = 10.305 kGs.
[0074] After obtaining the intrinsic remanence Br3 and the restoring permeability μ1, it is possible to... Figure 2 The virtual BH demagnetization curve, as shown by the dashed line, is obtained. Its slope is equal to that of the BH demagnetization curve at 20℃, and it intersects the BH demagnetization curve at 123℃ at point A.
[0075] It should be noted that, in step S15, the process of obtaining the permeability value based on the virtual BH demagnetization curve and the BH demagnetization curve at the second temperature includes:
[0076] The intersection point of the virtual BH demagnetization curve and the BH demagnetization curve at the second temperature is obtained, and the coordinate value of the intersection point is obtained.
[0077] The magnetic permeability value is obtained based on the coordinates of the intersection point.
[0078] It should be noted that the process of deriving the permeability value based on the coordinates of the intersection point includes:
[0079] The permeability value is calculated using the following formula:
[0080]
[0081] Where Pc is the permeability coefficient, By is the ordinate of the intersection point, and Hx is the abscissa of the intersection point.
[0082] In the example above, the coordinates of point A are (-9.25, 0.71). According to the permeability Pc = By / Hx, the permeability Pc = 0.71 / -9.25 = -0.077.
[0083] The permeability of any permanent magnet can be accurately evaluated using the above evaluation methods. To verify its accuracy, open-circuit verification was also performed at other temperatures. Table 1 below shows the evaluation table of the permeability of regular-shaped permanent magnets with open circuits:
[0084] Table 1
[0085]
[0086] The above verification shows that the method is quite accurate in evaluating the permeability of regular-shaped permanent magnets in open circuit. Table 2 further verifies the permeability of tile-shaped magnets in open circuit state and the permeability of magnets assembled into magnetic components after baking. The verification results are also quite accurate.
[0087] Table 2
[0088]
[0089] The demagnetization curves for numbers 1, 2, 4, and 5 above are shown in [reference]. Figure 3 For the demagnetization curve in number 3, please refer to [reference needed]. Figure 4 .
[0090] Example 2
[0091] A magnetic permeability evaluation device is provided, comprising:
[0092] The main controller and the memory connected to the main controller;
[0093] The memory stores program instructions;
[0094] The main controller is used to execute program instructions stored in the memory and perform any of the methods described above.
[0095] It is understood that the same or similar parts in the above embodiments can be referred to each other, and the contents not described in detail in some embodiments can be referred to the same or similar contents in other embodiments.
[0096] It should be noted that in the description of this invention, the terms "first," "second," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance. Furthermore, in the description of this invention, unless otherwise stated, "a plurality of" means at least two.
[0097] Any process or method description in the flowchart or otherwise herein can be understood as representing a module, segment, or portion of code comprising one or more executable instructions for implementing a particular logical function or process, and the scope of the preferred embodiments of the invention includes additional implementations in which functions may be performed not in the order shown or discussed, including substantially simultaneously or in reverse order depending on the functions involved, as will be understood by those skilled in the art to which embodiments of the invention pertain.
[0098] It should be understood that various parts of the present invention can be implemented in hardware, software, firmware, or a combination thereof. In the above embodiments, multiple steps or methods can be implemented in software or firmware stored in memory and executed by a suitable instruction execution system. For example, if implemented in hardware, as in another embodiment, it can be implemented using any one or a combination of the following techniques known in the art: discrete logic circuits having logic gates for implementing logical functions on data signals, application-specific integrated circuits (ASICs) having suitable combinational logic gates, programmable gate arrays (PGAs), field-programmable gate arrays (FPGAs), etc.
[0099] Those skilled in the art will understand that all or part of the steps of the methods in the above embodiments can be implemented by a program instructing related hardware. The program can be stored in a computer-readable storage medium, and when executed, the program includes one or a combination of the steps of the method embodiments.
[0100] Furthermore, the functional units in the various embodiments of the present invention can be integrated into a processing module, or each unit can exist physically separately, or two or more units can be integrated into a module. The integrated module can be implemented in hardware or as a software functional module. If the integrated module is implemented as a software functional module and sold or used as an independent product, it can also be stored in a computer-readable storage medium.
[0101] The storage media mentioned above can be read-only memory, disk, or optical disk, etc.
[0102] In the description of this specification, references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.
[0103] Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of the present invention.
Claims
1. A method for evaluating magnetic permeability, characterized in that, include: The BH demagnetization curve and the first magnetic moment value of the target permanent magnet at the first temperature are measured. Based on the BH demagnetization curve at the first temperature, the recovery permeability of the target permanent magnet at the first temperature is obtained. The first temperature is raised to the second temperature, and the BH demagnetization curve of the target permanent magnet is measured at the second temperature. Based on the BH demagnetization curve at the second temperature, the second remanence value of the target permanent magnet at the second temperature is obtained. When the second temperature drops back to the first temperature, the second magnetic moment value of the target permanent magnet is measured. Based on the first magnetic moment value, the second magnetic moment value, the second remanence value, and the restored permeability, a virtual BH demagnetization curve is obtained; The permeability value is obtained based on the virtual BH demagnetization curve and the BH demagnetization curve at the second temperature.
2. The method according to claim 1, characterized in that, The step of deriving the virtual BH demagnetization curve based on the first magnetic moment value, the second magnetic moment value, the second remanence value, and the restored permeability includes: Based on the first magnetic moment value, the second magnetic moment value, and the second remanence value, the intrinsic remanence value of the target permanent magnet at the second temperature is calculated. Based on the intrinsic remanence and the recovery permeability, a virtual BH demagnetization curve is obtained.
3. The method according to claim 2, characterized in that, The calculation of the intrinsic remanence of the target permanent magnet at the second temperature includes: Based on the second magnetic moment value and the first magnetic moment value, the irreversible decay rate of the target permanent magnet after the first temperature is increased to the second temperature is calculated; Based on the irreversible decay rate and the second remanence value, the intrinsic remanence value of the target permanent magnet at the second temperature is calculated.
4. The method according to claim 1, characterized in that, The step of deriving the permeability value based on the virtual BH demagnetization curve and the BH demagnetization curve at the second temperature includes: The intersection point of the virtual BH demagnetization curve and the BH demagnetization curve at the second temperature is obtained, and the coordinate value of the intersection point is obtained. The magnetic permeability value is obtained based on the coordinates of the intersection point.
5. The method according to claim 3, characterized in that, The calculation of the irreversible decay rate of the target permanent magnet after the first temperature is increased to the second temperature includes: The irreversible decay rate is calculated using the following formula: Where Loss is the irreversible decay rate, M2 is the second magnetic moment value, and M1 is the first magnetic moment value.
6. The method according to claim 5, characterized in that, The calculation of the intrinsic remanence of the target permanent magnet at the second temperature includes: The intrinsic remanence at the second temperature is calculated using the following formula: Br3 = Br2 × (1 - Loss) Wherein, Br3 is the intrinsic remanence value at the second temperature, and Br2 is the second remanence value.
7. The method according to claim 4, characterized in that, The step of deriving the permeability value based on the coordinates of the intersection point includes: The permeability value is calculated using the following formula: Where Pc is the permeability coefficient, By is the ordinate of the intersection point, and Hx is the abscissa of the intersection point.
8. A magnetic permeability evaluation device, characterized in that, include: The main controller and the memory connected to the main controller; The memory stores program instructions; The master controller is used to execute program instructions stored in the memory to perform the method as described in any one of claims 1 to 7.