A magnetic circuit with multiple magnet types.

Abstract

We will improve the magnetic circuit that incorporates multiple types of magnets. [Solution] The device includes a first magnet 102 having a first remanent magnetization value and a first coercivity value, the first magnet having a first cross-sectional area substantially perpendicular to the magnetization direction of the first magnet, and a second magnet 104 arranged in series with the first magnet, the second magnet having a second remanent magnetization value and a second coercivity value smaller than the first coercivity value, and having a second cross-sectional area substantially perpendicular to the magnetization direction of the second magnet. The ratio of the first cross-sectional area to the second cross-sectional area is equal to or greater than the ratio of the second remanent magnetization value to the first remanent magnetization value.

Description

Technical Field

[0001] Cross - Reference to Related Applications This application claims priority to U.S. Non - Provisional Patent Application No. 17 / 701,047, filed on March 22, 2022, entitled "MAGNETIC CIRCUIT WITH MORE THAN ONE MAGNET TYPE", which is hereby incorporated by reference in its entirety.

[0002] Technical Field The present disclosure relates to the field of magnetic circuits, particularly to permanent magnets used in magnetic circuits.

[0003] Description of Related Art Permanent magnets are widely used in electrical and electromechanical applications. For example, a permanent magnet can be used to provide a magnetic field, which can interact with a current - carrying conductor. This interaction can generate a mechanical force on the conductor and the magnet assembly, and this force can be utilized in various applications such as motors.

Summary of the Invention

Means for Solving the Problems

[0004] In some aspects, the technology described herein relates to an apparatus that includes a first magnet having a first remanence value and a first coercivity value, the first magnet having a first cross - sectional area that is substantially perpendicular to the magnetization direction of the first magnet, and a second magnet arranged in series with the first magnet, the second magnet having a second remanence value and a second coercivity value that is less than the first coercivity value, the second magnet having a second cross - sectional area that is substantially perpendicular to the magnetization direction of the second magnet. The ratio of the first cross - sectional area to the second cross - sectional area is equal to or greater than the ratio of the first remanence value to the second remanence value.

[0005] In some aspects, the second magnet is arranged in the path of the magnetization direction of the first magnet. In some embodiments, the second remanent magnetization value is greater than the first remanent magnetization value. The operating point of the second magnet is located in the second quadrant of the magnetization (BH) curve associated with the second magnet. , a magnetic flux density value greater than the magnetic flux density value in the case where the first cross-sectional area is equal to the second cross-sectional area. It is located there.

[0006] In some embodiments, the first magnet has a shape having a non-constant cross-sectional area perpendicular to the magnetization direction of the first magnet, and the first cross-sectional area is equal to the smallest of the non-constant cross-sectional areas. In some embodiments, the second magnet has a shape having a non-constant cross-sectional area perpendicular to the magnetization direction of the second magnet, and the second cross-sectional area is equal to the largest of the non-constant cross-sectional areas.

[0007] In some embodiments, the first magnet has a first curved shape defined by a first curved surface and a second curved surface separated by the thickness of the first magnet, the magnetization direction of the first magnet is parallel to one radius of the first curved shape, and the first cross-sectional area includes the area of ​​a first plane perpendicular to the magnetization direction of the first magnet. In some embodiments, the first plane perpendicular to the magnetization direction of the first magnet has the smallest area among the set of planes perpendicular to the magnetization direction of the first magnet.

[0008] In some embodiments, the first magnet has a first curved shape defined by a first curved surface and a second curved surface separated by the thickness of the first magnet, the magnetization directions of the first magnet have a plurality of directions extending along the radius of the first curved shape, and the first cross-sectional area includes the area of ​​the curved surfaces perpendicular to the plurality of directions. In some embodiments, the curved surfaces perpendicular to the plurality of directions are the curved surfaces having the smallest area among the set of curved surfaces perpendicular to the plurality of directions.

[0009] In some embodiments, the second magnet has a second curved shape defined by a third and a fourth curved surface separated by the thickness of the second magnet, the magnetization direction of the second magnet is parallel to one radius of the second curved shape, and the second cross-sectional area includes the area of ​​a second plane perpendicular to the magnetization direction of the second magnet.

[0010] In some embodiments, the second plane perpendicular to the magnetization direction of the second magnet has the largest area among the set of planes perpendicular to the magnetization direction of the second magnet. In some embodiments, the second magnet has a second curved shape defined by a third and a fourth curved surface separated by the thickness of the second magnet, the magnetization direction of the second magnet has multiple directions extending along the radius of the second curved shape, and the second cross-sectional area includes the area of ​​the curved surface perpendicular to the multiple directions. In some embodiments, the curved surface perpendicular to the multiple directions is the curved surface having the largest area among the set of curved surfaces perpendicular to the multiple directions.

[0011] In some embodiments, the first magnet and the second magnet are separated by a spacer. In some embodiments, the spacer includes a ferromagnetic material. In some embodiments, the spacer has a cross-sectional area at least equal to the larger of the first and second cross-sectional areas. In some embodiments, the thickness of the spacer is 3 mm or less. In some embodiments, the device further includes an electromachine including a stator and a rotor separated from the stator by an air gap, wherein the first magnet and the second magnet are arranged in series with only one of the stator or the rotor. In some embodiments, the first magnet is positioned closer to the air gap than the second magnet. In some embodiments, the electromachine includes a plurality of poles, at least one of which includes the first magnet and the second magnet.

[0012] In some embodiments, the first magnet is of the neodymium-iron-boron type. In some embodiments, the first magnet is of the samarium-cobalt type. In some embodiments, the second magnet includes at least one of the iron nitride type. [Brief explanation of the drawing]

[0013] [Figure 1A-1B] Figures 1A and 1B show examples of magnetic devices that include two magnets connected in series.

[0014] [Figure 2A-2B] Figures 2A and 2B are diagrams depicting exemplary graphs representing the magnetization characteristics (also known as B-H curves) of two magnets connected in series.

[0015] [Figure 3A-3D] Figures 3A to 3D are diagrams showing various examples of magnet arrangements showing at least two magnets arranged in series. [Figure 3E-3F] Figures 3E to 3F are diagrams showing various examples of magnet arrangements showing at least two magnets arranged in series.

[0016] [Figure 3G-3H] Figures 3G to 3H are diagrams showing examples of arrangements of magnets that are considered not to be in series.

[0017] [Figure 4A-4C] Figures 4A to 4C are diagrams showing the determination of the cross-sectional areas of magnets having various shapes and magnetization direction orientations. [Figure 4D-4E] Figures 4D to 4E are diagrams showing the determination of the cross-sectional areas of magnets having various shapes and magnetization direction orientations.

[0018] [Figure 5] Figure 5 is a diagram showing a part (one pole) of the cross-section of a permanent magnet motor.

Embodiments for Carrying out the Invention

[0019] Similar reference numerals and names in the various drawings indicate similar elements.

[0020] Detailed Description The various concepts presented above and further detailed below can be implemented in any of a number of aspects because the concepts being described are not limited to a particular implementation method. Specific implementation examples and application examples are provided primarily for the purpose of explanation.

[0021] As will be apparent to those skilled in the art upon reading this disclosure, each of the individual embodiments described and illustrated herein has distinct components and features, which without departing from the scope or spirit of the present disclosure, can easily be separated from or readily combined with any of several other embodiments.

[0022] Any of the described methods can be carried out in the order of the described events or in any other logically possible order. That is, unless otherwise explicitly stated, it is not intended that the methods or aspects described herein be construed as requiring that their steps be executed in a particular order. Thus, where a method claim does not specifically recite in the claims or description that the steps are limited to a particular order, no order should be inferred in any respect. This applies to any implicit interpretive criteria, such as logical matters regarding the arrangement of steps or the flow of operations, the plain meaning derived from grammatical construction and punctuation, or the number and types of aspects described in the specification.

[0023] All publications referred to herein are incorporated herein by reference for the purpose of disclosing and describing the methods and / or materials in connection with which they are cited. The publications discussed herein are provided solely for their disclosure prior to the filing date of the present application. Nothing in this specification is to be construed as an admission that the present invention is not entitled to antedate such publications by virtue of prior invention. Further, the publication dates provided herein may be different from the actual publication dates and may require independent verification.

[0024] Aspects of the present disclosure may be described and claimed in terms of specific statutory classes, such as systems, but this is for convenience only, and those skilled in the art will understand that each aspect of the present disclosure can be described and claimed in terms of any statutory class.

[0025] Furthermore, it should be understood that the terms used herein are for the sole purpose of describing specific embodiments and are not intended to be limiting. Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those generally understood by those skilled in the art in the art to which the disclosed compositions and methods belong. In addition, terms as defined in commonly used dictionaries should be interpreted as having the meaning consistent with their meaning in the context of this specification and related art, and should not be interpreted in an idealized or overly formal sense unless expressly defined herein.

[0026] It should be noted that ratios, concentrations, quantities, and other numerical data may be expressed in range form as specified herein. It will be further understood that each endpoint of a range is important with respect to the other endpoint and is important independently of the other endpoint. Also, it will be understood that there are many values ​​disclosed herein, and each value is disclosed herein not only as the value itself but also "about" that particular value. For example, if the value "10" is disclosed, "about 10" is also disclosed. Ranges may be expressed herein as "about" a particular value and / or "about" another particular value. Similarly, it will be understood that when a value is expressed as an approximation by the use of the antecedent "about", a particular value forms further aspects. For example, if the value "about 10" is disclosed, "10" is also disclosed.

[0027] Where a range is expressed, further embodiments include a range from one specific value and / or to the other specific value. For example, if a specified range includes one or both limit values, the disclosure also includes a range that excludes either or both of those limit values, for example, the expression "x~y" includes not only the range from "x" to "y" but also the range greater than "x" and less than "y". A range can also be expressed as an upper limit, for example, "about x, y, z, or less", which should be interpreted as including the specific ranges of "about x", "about y", and "about z", and the ranges of "less than x", "less than y", and "less than z". Similarly, the phrase "about x, y, z, or greater than" should be interpreted as including the specific ranges of "about x", "about y", and "about z", and the ranges of "greater than x", "greater than y", and "greater than z". Furthermore, the phrase "about 'x'~'y'" includes "about 'x'~about 'y'" when "x" and "y" are numerical values.

[0028] It should be understood that such range formats are used for convenience and conciseness, and should be interpreted flexibly to include not only the numerical values ​​explicitly stated as range limits, but also all individual numerical values ​​or subranges contained within that range, as if each numerical value and subrange were explicitly stated. For illustrative purposes, the numerical range "approximately 0.1% to approximately 5%" should be interpreted to include not only the explicit numerical values ​​of approximately 0.1% to approximately 5%, but also individual numerical values ​​(e.g., approximately 1%, approximately 2%, approximately 3%, approximately 4%) and subranges (e.g., approximately 0.5% to approximately 1.1%, approximately 5% to approximately 2.4%, approximately 0.5% to approximately 3.2%, approximately 0.5% to approximately 4.4%, and other possible subranges).

[0029] As used herein, the terms “about,” “approximate,” “at or about,” and “substantially” mean that the quantity or value in question may be an exact value or a value that provides an equivalent result or effect as described in the claims or taught herein. That is, quantities, sizes, formulations, parameters, and other quantities and characteristics are not and do not need to be exact, but may be approximate and / or greater or less, as desired, to reflect tolerances, conversion factors, rounding, measurement errors and the like, and other factors known to those skilled in the art that result in an equivalent outcome or effect. In some circumstances, it may not be possible to reasonably determine a value that yields an equivalent result or effect. In such cases, as used herein, “about” and “at or about” are generally understood to mean a variation of ±10% of the stated nominal value unless otherwise indicated or inferred. Generally, quantities, sizes, proportions, parameters, or other quantities or characteristics are "about," "approximate," or "at or about," whether explicitly stated as such. When "about," "approximate," or "at or about" is used before a quantitative value, it is understood that the parameter includes the specific quantitative value itself, unless otherwise specified.

[0030] Before describing the various aspects of this disclosure, the following definitions are provided and should be used unless otherwise indicated. Additional terms may be defined elsewhere in this disclosure.

[0031] As used herein, “comprising” is to be interpreted as identifying the presence of the described feature, integer, step, or component mentioned, but not as excluding the presence or addition of one or more features, integers, steps, or components, or groups thereof. Furthermore, the terms “by,” “comprising,” “comprises,” “comprised of,” “including,” “includes,” “included,” “involving,” “involves,” “involved,” and “such as” are used in their open, non-restrictive sense and may be used interchangeably. In addition, the term “comprising” is intended to include examples and aspects encompassed by the terms “consisting essentially of” and “consisting of.” Similarly, the term “consisting essentially of” is intended to include examples encompassed by the term “consisting of.”

[0032] As used herein, the term "and / or" includes any combination of one or more of the relevant list items. Expressions such as "at least one of" qualify the entire list of elements, but not the individual elements of the list, when they precede a list of elements.

[0033] As used herein and in the appended claims, the singular forms “a,” “an,” and “the” include multiple referents unless the context clearly indicates otherwise. Thus, for example, a reference to “a proton beam degrader,” “a degrader foil,” or “a conduit” includes, but is not limited to, two or more such proton beam degraders, degrader foils, or conduits.

[0034] The various concepts presented above and described in more detail below can be implemented in any of many forms, since the concepts described are not limited to any particular method of implementation. Specific examples and applications are provided primarily for illustrative purposes.

[0035] As used herein, the terms “optional” or “optionally” mean that the events or circumstances described thereafter may or may not occur, and that such descriptions include examples of events or circumstances in which they occur and examples of circumstances in which they do not occur.

[0036] Permanent magnets are commonly used in various devices such as electric motors, electric generators, and electric actuators. They provide a magnetic field that interacts with a current-carrying conductor or a moving conductor. Permanent magnets are partially characterized by their remanent magnetization (Br) and coercivity (Hc). The remanent magnetization of a permanent magnet generally refers to the magnetization of the magnet in the absence of an external magnetic field. Remanent magnetization can be measured as the magnetic flux density (Br) when the external magnetic field (H) is zero. The coercivity (Hc) of a permanent magnet generally refers to the magnitude of the external magnetic field that the permanent magnet can withstand without demagnetization. Coercivity can be measured as the magnitude of the external magnetic field when the magnetic flux density becomes zero. It is desirable for permanent magnets to have high remanent magnetization and high coercivity. For example, when permanent magnets are used in electrical machinery such as motors, they may encounter magnetic fields generated by other magnets or current-carrying conductors. These magnetic fields can be large enough to permanently demagnetize the permanent magnet. A demagnetized permanent magnet needs to be replaced, increasing the operating costs of the electrical machinery.

[0037] One method to reduce the risk of demagnetization is to use permanent magnets that possess both high coercivity and high remanent magnetization. However, many permanent magnets that possess both high coercivity and high remanent magnetization are expensive, increasing the cost of electrical machinery. However, there are also examples of using magnets that are relatively inexpensive and exhibit low coercivity but high remanent magnetization. Using such magnets reduces costs, but the risk of demagnetization increases due to the low coercivity. Another method is to reduce the magnitude of the demagnetizing magnetic field generated by electrical machinery. In most cases, this can be done by limiting the current flowing through the conducting conductor. However, limiting the current may also limit the torque generated by the electrical machinery. That is, on the one hand, limiting the magnitude of the demagnetizing magnetic field reduces the risk of demagnetizing the permanent magnet, but on the other hand, limiting the current flowing through the conducting conductor limits the torque generated by the electrical machinery. Since it is desirable to extract as much torque as possible from electrical machinery, limiting the generated torque may be undesirable in some cases.

[0038] As will be described in detail herein, one method for reducing the risk of demagnetization without reducing torque generation and for reducing the costs associated with high residual magnetization and high coercivity permanent magnets is to use multiple permanent magnets in series. Specifically, a first magnet with high coercivity is placed in series with a second magnet having a lower coercivity value than the first magnet. In addition to being placed in series, the dimensions of the first and second magnets are selected such that the magnetic flux density of the second magnet is higher when the first magnet is placed in series than when it is not, as will be described in detail later. By increasing the magnetic flux density of the second magnet in this way, the operating point of the second magnet can be shifted, and the counter-magnetic field can be increased while reducing the risk of demagnetization of the second magnet. The increase in the counter-magnetic field translates to the ability to use a larger current in the current-carrying conductor, resulting in greater torque.

[0039] Figure 1A shows an exemplary first magnetic device 100 including two magnets arranged in series. Specifically, Figure 1A shows the first magnetic device 100 including a first magnet 102 arranged in series with a second magnet 104. The first magnet 102 has a first remanent magnetization value Br1 and a first coercivity value Hc1, and the second magnet 104 has a second remanent magnetization value Br2 and a second coercivity value Hc2. In the first magnetic device 100, the second coercivity value Hc2 is smaller than the first coercivity value Hc1. The first magnet 102 also has a first cross-sectional area S1, and the second magnet 104 has a second cross-sectional area S2.

[0040] Figure 1B shows an exemplary second magnetic device 200 including two series-connected magnets separated by a spacer. Specifically, the second magnetic device 200 includes a first magnet 102 and a second magnet 104 separated by a spacer 202. In some examples, the spacer 202 is a ferromagnetic material. In some examples, the spacer 202 may include ferromagnetic materials such as iron, steel, cobalt, nickel, and neodymium. The spacer 202 may have a cross-sectional area equivalent to at least the larger of the effective cross-sectional area of ​​the first magnet 102 and the effective cross-sectional area of ​​the second magnet 104. For example, as shown in Figure 1B, the cross-sectional area of ​​the spacer 202 is at least equivalent in size to the effective cross-sectional area S1 of the first magnet 102, and the cross-sectional area S1 is larger than the cross-sectional area S2 of the second magnet 104. In some examples, the spacer 202 may be positioned such that its periphery coincides with or extends beyond the periphery of the first magnet 102. In the example shown in Figure 1B, the periphery of the spacer 202 coincides with the periphery of the first magnet 102 (or the magnet with the larger surface area), but in other examples, the outer circumference may extend beyond the periphery of the first magnet 102 (or the magnet with the larger surface area). The presence of the spacer 202, particularly the ferromagnetic spacer, helps to reorient the magnetic flux when it leaves one magnet (e.g., the second magnet) before it enters the other magnet (the first magnet in the same example). This reorientation of the magnetic flux allows for more efficient use of the overall volume of the two magnets. Therefore, the optimal effect is obtained when the spacer 202 is wider than both magnets, or at least as wide as the wider of the two magnets (as shown in Figure 1B). Since the permeability of typical ferromagnetic materials (e.g., steel) is orders of magnitude greater than that of both air and typical magnetic materials, the spacer 202 does not need to be thick. In reality, the main constraints in determining the thickness of a spacer are sometimes not due to magnetic reasons, but rather to mechanical properties or manufacturing convenience.

[0041] In some examples, the spacer may have a shape and dimensions such that there is no intentional air gap between the surface of the spacer 202 and the adjacent magnet. For example, the surface of the spacer 202 adjacent to the first magnet 102 may have a shape that conforms to the shape of the surface of the first magnet 102 facing the spacer. Similarly, the surface of the spacer 202 adjacent to the second magnet 104 may have a shape that conforms to the shape of the surface of the second magnet 104 facing the spacer 202. In some examples, the thickness of the spacer may be between 1 mm and 5 mm, or it may be 3 mm.

[0042] The series combination of the first magnet 102 and the second magnet 104, having relative dimensions described later, allows the combination to have a lower risk of demagnetization. Specifically, such a series combination shifts the operating point of the magnet with lower coercivity, thereby reducing the risk of demagnetization of that magnet. Figures 2A and 2B show exemplary graphs representing the BH characteristics of two magnets arranged in series. The same BH curve is shown in both Figures 2A and 2B, which reflects that the same magnetic material is used for the first and second magnets. The difference between the two figures lies in the operating points of the two magnets. Specifically, Figure 2A shows a situation where the first magnet 102 and the second magnet 104 have similar effective cross-sectional areas, while Figure 2B shows another situation where the two magnets have different effective cross-sectional areas. Specifically, the ratio of the effective cross-sectional area of ​​the first magnet 102 to the effective cross-sectional area of ​​the second magnet 104 is equal to or greater than the ratio of the remanent magnetization value of the second magnet 104 to the remanent magnetization value of the first magnet 102. Referring to Figure 2A, the x-axis represents the applied magnetic field (H), and the y-axis represents the magnetic flux density of the magnets (B). Note that Figures 2A and 2B show a portion of the BH curves of the two magnets (especially the upper left quadrant). Generally, such a BH curve is called a hysteresis curve or magnetization curve. The upper left portion of the BH curve shows the magnetic flux density of the magnets in response to an opposing magnetic field (indicated by a negative value on the x-axis) H.

[0043] As mentioned above, permanent magnets can be characterized in part by their remanent magnetization (Br) and coercivity (Hc). Referring to the BH curve of the second magnet in Figure 2A, the remanent magnetization (Br) of the second magnet 104 can be determined by the value of the magnetic flux density B when the value of the magnetic field H is equal to zero. The value of the remanent magnetization Br is indicated by the value of the magnetic flux density B at which the BH curve intersects the y-axis. The coercivity (Hc) of the second magnet 104 can be determined by the value of the magnetic field H at which the magnetic flux density B is equal to zero. The value of the coercivity Hc is indicated by the value of the magnetic field H at which the BH curve intersects the x-axis. In the example shown in Figures 2A and 2B, the coercivity Hc1 of the first magnet 102 is greater than the coercivity Hc2 of the second magnet 104, and the remanent magnetization Br1 of the first magnet 102 is less than the remanent magnetization Br2 of the second magnet 104.

[0044] Magnets can also be characterized by a demagnetization point (or commonly called a "demagnetization knee"), which is a point on the BH curve where the magnetic flux density decreases rapidly in response to a further increase in the magnitude of the opposing magnetic field. Operating a permanent magnet beyond its demagnetization point can increase the risk of demagnetization. For example, referring to the BH curve of the second magnet in Figure 2A, the BH curve decreases substantially linearly as a function of the increasing magnitude of the opposing magnetic field from the point where the BH curve intersects the y-axis to the demagnetization point. As the magnitude of the opposing magnetic field increases further, the BH curve decreases nonlinearly and quite rapidly. Beyond the demagnetization point, the magnet may be irreversibly demagnetized.

[0045] It is desirable to design the second magnet 104 such that its operating point does not fall below the demagnetization point on the BH curve. It should be noted that the operating point of a permanent magnet is the intersection of the BH curve and the load line (also known as the permeability line). The operating point exhibits a magnetic flux density corresponding to the magnitude of the opposing magnetic field. As long as the operating point is maintained above the demagnetization point on the BH curve, the operating point may return to the remanent magnetization value Br when the opposing magnetic field is removed. However, if the operating point of a permanent magnet falls below the demagnetization point, the operating point may not return to the original remanent magnetization value Br even when the opposing magnetic field is removed. Instead, the operating point is more likely to return to a value smaller than the original remanent magnetization value, which indicates irreversible demagnetization of the permanent magnet.

[0046] When considering the two magnets 104 and 102 individually (i.e., not adjacent but in similar magnetic circuits), each magnet will have an operating point on its own BH curve. In many cases, if the two magnets have equal effective cross-sectional areas and are in similar magnetic circuits, the operating point of the second magnet 104 will be at a higher magnetic flux density than the operating point of the first magnet 102 due to the stronger residual magnetization of magnet 104. However, if the two magnets are arranged in series and have equal effective cross-sectional areas, due to magnetic flux conservation, the operating point of the second magnet 104 will be "deflected downward" or even further down on the second magnet's BH curve. This can be seen in Figure 2A, where the operating points of the first magnet 102 and the second magnet 104 have equal magnetic flux densities (B1=B2). The downward deviation of the operating point of the second magnet 104 brings it closer to the demagnetization point, and as mentioned above, the risk of permanent demagnetization of the second magnet 104, which has lower coercivity than the first magnet 102, increases.

[0047] To mitigate the risk of demagnetization, the relative dimensions of the first magnet 102 and the second magnet 104 can be selected so that the operating point of the second magnet 104 (which has a relatively low coercivity) is deflected upward away from the demagnetization point. In particular, the ratio of the effective surface area S1 of the first magnet 102 to the effective surface area S2 of the second magnet 104 is greater than or equal to the ratio of the remanent magnetization value Br2 of the second magnet 104 to the remanent magnetization value Br1 of the first magnet 102, and the following equation

number

[0048] Equation (1) suggests that the relative size of magnets in series is a function of their relative remanent magnetization. In some examples, if the second magnet 104 has a greater remanent magnetization than the first magnet 102, the effective cross-sectional area of ​​the second magnet 104 will be smaller than that of the first magnet 102. The extent to which the effective cross-sectional area of ​​the second magnet 104 is smaller than that of the first magnet 102 depends on the ratio of the remanent magnetizations of the two magnets. Figure 2B shows an example of the resulting relative position of the operating point of the second magnet 104. Specifically, by ensuring that the effective surface areas of the first magnet 102 and the second magnet 104 satisfy equation (1) above, magnetic flux conservation moves the operating point of the second magnet 104 further away from the demagnetization point on the BH curve. As a result, the risk of demagnetization of the second magnet 104 is reduced. Conversely, the operating point of the first magnet becomes lower, but this is acceptable because the coercivity of the first magnet is high.

[0049] As mentioned above, currently known permanent magnets that possess both high coercivity and high remanent magnetization (such as neodymium-iron-boron magnets and samarium-cobalt magnets) are expensive, which restricts or even prohibits their use in many applications. Other currently known magnets, such as iron nitride magnets, have high remanent magnetization but low coercivity and are relatively inexpensive. By utilizing a series combination of a first magnet 102 with high coercivity and a second magnet 104 with relatively low coercivity and a relatively low cost, it is possible to achieve the desired level of performance in an application while reducing the overall cost of using permanent magnets. In other words, while conventionally the entire magnet was composed of expensive high-coercivity material, in a series combination, only a portion of the entire magnetic device is composed of expensive high-coercivity material, and the rest of the magnetic device is composed of relatively inexpensive low-coercivity material.

[0050] Furthermore, a method of mitigating demagnetization by reducing the current in the current-carrying conductor that generates the opposite and demagnetizing magnetic fields has also been described. This method affected the maximum torque that the electromachine could generate. However, by utilizing the series combination of magnets described herein, the current in the current-carrying conductor can be unaffected or at least increased, potentially resulting in higher torque from a given electromachine. For example, referring to Figure 2B, the "upward deflection" of the operating point of the second magnet 104 moves the operating point of the second magnet 104 away from the demagnetizing point. This provides a larger margin in terms of magnetic field strength for operating the second magnet 104 before the risk of demagnetization arises. This larger margin translates into a larger current in the current-carrying conductor within the electromachine, thereby allowing the electromachine to generate a relatively large torque before it incurs the risk of irreversible demagnetization.

[0051] In the descriptions of the first magnetic device 100 and the second magnetic device 200, it was mentioned that the first magnet 102 is arranged in series with the second magnet 104. In this specification, "arranging the first magnet in series with the second magnet" means that in a magnetic circuit partially formed by the first magnet and the second magnet, the second magnet is positioned relative to the first magnet such that the entire magnetic flux of the second magnet crosses at least a portion of the first magnet. "Entire magnetic flux" excludes leakage flux generated in the second magnet or within the magnetic circuit.

[0052] Figure 3A shows an example of a series arrangement of two magnets. Specifically, Figure 3A shows a first magnet 102 and a second magnet 104 in a series arrangement. The first magnet 102 can have a cylindrical or rectangular parallelepiped shape with a constant cross-sectional area along its magnetization direction. Similarly, the second magnet 104 can also have a cylindrical or rectangular parallelepiped shape with a constant cross-sectional area along its magnetization direction. For illustrative purposes, the magnets in Figures 3B to 3H can have similar shapes to those shown in Figure 3A, although their dimensions may differ. However, it should be noted that the cylindrical or rectangular parallelepiped shapes are merely examples and do not limit the types of magnet shapes that can be used. The first magnet 102 has a first magnetization direction 302, and the second magnet has a second magnetization direction 304. The first magnet 102 and the second magnet 104 can partially form a magnetic circuit 306, which may include one or more closed-loop paths containing the magnetic flux generated by the first magnet 102 and the second magnet 104. The magnetic circuit 306 may include additional components containing the magnetic flux, such as a portion of the rotor or stator, or an air gap. The entire magnetic flux 308 of the second magnet 104 traverses at least a portion of the first magnet 102. In some examples, the second magnet 104 may generate some leakage flux. In this context, the entire magnetic flux 308 does not include that leakage flux.

[0053] Figure 3B shows another example of the arrangement of the two magnets. Specifically, the arrangement shown in Figure 3B is the same as the arrangement shown in Figure 3A, except that it includes a spacer similar to the spacer 202 shown in Figure 2B. In this arrangement as well, the entire magnetic flux 308 of the second magnet 104 crosses at least a portion of the first magnet 102.

[0054] Figure 3C shows another example of the arrangement of two magnets. In particular, the arrangement shown in Figure 3C shows additional elements such as steel (310 and 312) and an air gap, which typically form part of a magnetic circuit in electrical machinery such as motors and generators. Specifically, the first steel element 310 is adjacent to the first magnet 102 and positioned between the first magnet 102 and the air gap, and the second steel element 312 is adjacent to the second magnet 104. The steel elements 310 and 312, as well as the air gap, form part of the magnetic circuit 306. In this arrangement as well, in the magnetic circuit 306 partially formed by the first magnet 102 and the second magnet 104, the entire magnetic flux 308 of the second magnet 104 crosses the first magnet 102. Although the arrangement shows steel elements, it is understood that other ferromagnetic materials can also form part of the magnetic circuit 306.

[0055] Figure 3D shows an example of the arrangement of three magnets. In this arrangement, two magnets are arranged in series with the first magnet 102. Specifically, the second magnet 104 and the third magnet 314 are each arranged in series with the first magnet 102. The third magnet 314 has a magnetization direction 316 parallel to the magnetization direction 304 of the second magnet 104. In this arrangement, it should be noted that the second magnet 104 is not in series with the third magnet 314 because the magnetic flux 308 of the second magnet 104 does not cross the third magnet 314. However, since the entire magnetic flux 308 of the second magnet 104 crosses the first magnet 102, the second magnet 104 is in series with the first magnet 102.

[0056] Figure 3E shows yet another arrangement of the two magnets. In this arrangement, the length of the second magnet 104 is perpendicular to the length of the first magnet 102. The first magnet 102 and the second magnet 104 partially form a magnetic circuit 318. Within the magnetic circuit 318, the entire magnetic flux 308 of the second magnet traverses at least a portion of the first magnet 102. A portion 320 of the first magnet 102 is not traversed by the magnetic flux 308 of the second magnet 104. However, since the entire magnetic flux 308 traverses "at least a portion of the first magnet 102", the second magnet 104 can be considered to be in series with the first magnet 102.

[0057] Figure 3F shows yet another arrangement of the two magnets. This arrangement is similar to the arrangement shown in Figure 3E, but includes a complete magnetic circuit. This arrangement includes a first magnet 102, a first air gap 324, a first steel core 326 around which a coil 328 is wound, a second air gap 330, and a second steel core 332. The coil 328 can carry an electric current to magnetize the first steel core 326. The first air gap 324 is located between the first magnet and one end of the first steel core 326, and the second air gap 330 is located between the second end of the first steel core 326 and the second steel core 332. The arrangement shown in Figure 3F can represent a part of an electromachine, where the first steel core 326 represents part of the stator, the combination of the second steel core 332, the first magnet 102, and the second magnet 104 can represent part of the rotor, and the first air gap 324 and the second air gap 330 allow the rotor to move relative to the stator. The first magnet 102 includes a portion 334 that is not traversed by the magnetic flux 308 of the second magnet 104. Similar to the arrangement shown in Figure 3E, in the arrangement shown in Figure 3F, the second magnet 104 is in series with the first magnet 102, since the entire magnetic flux 308 of the second magnet 104 traverses at least a portion of the first magnet 102 in the magnetic circuit 322 which is partially formed by the first magnet 102 and the second magnet 104.

[0058] Figure 3G shows another arrangement where the two magnets are not in series. Specifically, the arrangement in Figure 3G shows that the second magnet 104 is positioned adjacent to the first steel element 310, and the first magnet 102 is positioned adjacent to the second steel element 312. The third magnet 336 is positioned parallel to the first magnet 102 and has a magnetization direction 340 parallel to the first magnet 102. The third magnet 336 may have similar properties to the second magnet 102, but this is not necessarily required. For example, the third magnet 336 can have the same coercivity and remanent magnetization values ​​as the second magnet 104. In this arrangement, at least a portion of the second magnet 104 is not in series with the first magnet 102. This is because, although the magnetization directions of both magnets are the same, the entire magnetic flux 308 of the second magnet does not cross the first magnet 102. Therefore, it cannot be considered that the second magnet 104 is in series with the first magnet 102.

[0059] Figure 3H shows another configuration in which the two magnets are not in series. In this configuration, at least a portion of the magnetic flux 308 of the second magnet 104 does not cross the first magnet 102. Therefore, the second magnet 104 is not in series with the first magnet 102.

[0060] Referring to equation (1) above, the left-hand side of equation (1) is the ratio of the effective surface area S1 of the first magnet 102 to the effective surface area S2 of the second magnet 104. This ratio, or the relative size of the magnets, can be a function of the relative remanent magnetization of the two magnets. In general, the effective surface area of ​​a magnet is the cross-sectional area of ​​the magnet perpendicular to the magnetization direction. If the shape of the magnet is cylindrical or rectangular (such as the first magnet 102 and the second magnet 104 mentioned above in relation to Figures 3A to 3F), and the direction of magnetization is along the longitudinal axis of the magnet, the effective cross-sectional area can be the actual cross-sectional area of ​​the magnet. However, if the direction of magnetization is not along the longitudinal axis, or if the cross-sectional area of ​​the magnet is not uniform along the direction of magnetization, the cross-sectional area perpendicular to the longitudinal axis does not represent the effective cross-sectional area. In such cases, further consideration is needed to determine the effective cross-sectional area.

[0061] Figure 4A shows a permanent magnet 400 in which the cross-sectional area perpendicular to the magnetization direction is not constant. The magnet 400 includes a first surface 402, a second parallel surface 404 opposite the first surface 402, and a plurality of sides 406 extending between the periphery of the first surface 402 and the second surface 404. The first surface 402 has a larger surface area than the second surface 404. As a result, the plurality of sides 406 make non-perpendicular angles with respect to both the first surface 402 and the second surface 404. Additionally, the cross-sectional area of ​​the magnet 400 is not constant or equal along the length of the magnet 400. The magnet 400 has a magnetization direction indicated by arrow 408, which is substantially perpendicular to the first surface 402 and the second surface 404. Given the shape of the magnet 400 in which the cross-sectional area along the magnetization direction is not constant, it is necessary to consider which of the multiple cross-sectional areas should be selected to represent the effective cross-sectional area. One factor that may influence the selection is whether magnet 400 is used as the first magnet 102 or as the second magnet 104. In other words, the choice of cross-sectional area may depend on whether magnet 400, which is placed in series with the other magnets, is a magnet with a higher coercivity or a magnet with a lower coercivity.

[0062] If magnet 400 has a lower coercivity than the other magnets in series, its effective cross-sectional area will be equal to the largest of the non-constant cross-sectional areas. There is at least one reason to select the largest of the non-constant surface areas: for a magnet with low coercivity, the magnetic flux density is lowest at the largest cross-sectional area, which is the region where the magnet is most easily demagnetized. Therefore, the effective surface area of ​​a magnet with low coercivity is the cross-sectional area where the magnetic flux density is lowest. In the case of magnet 400 shown in Figure 4A, the largest cross-sectional area is the area of ​​the first surface 402.

[0063] If magnet 400 has a higher coercivity than the other magnets in series, its effective cross-sectional area will be equal to the smallest non-constant cross-sectional area. Therefore, if magnet 400 is used as the first magnet 102, its effective cross-sectional area will be the area of ​​the second surface 404 which has the smallest cross-sectional area among all non-constant cross-sectional areas.

[0064] When determining the cross-sectional area, it should be noted that only the portion of magnet 400 that is located within a magnetic circuit partially formed by the series of magnets should be considered. For example, referring to Figure 3F, portion 334 of the first magnet 102 may not be considered when determining the effective cross-sectional area of ​​the magnet. This ensures that only the portion of the magnet that carries magnetic flux from the second magnet 104 and thus affects the magnetic flux density of the magnet is included when determining the effective cross-sectional area in the manner described above.

[0065] Figure 4B shows another exemplary permanent magnet 410 in which the cross-sectional area perpendicular to the magnetization direction is not constant. Permanent magnet 410 is similar in shape to permanent magnet 400 shown in Figure 4A, but unlike permanent magnet 400, in which the magnetization direction indicated by arrow 408 is substantially perpendicular to the first surface 402 and the second surface 404, the magnetization direction of magnet 410, indicated by arrow 412, is not perpendicular to both the first surface 402 and the second surface 404. As a result, the cross-sectional area is not constant along the magnetization direction. An example of a cross-sectional area shown by a dashed line shows a cross-sectional area within the magnet that forms an angle with respect to the first surface 402 and the second surface 404 but is perpendicular to the magnetization direction. Similar to the method described in relation to Figure 4A, the effective cross-sectional area of ​​the magnet depends on whether magnet 410 is used as a magnet with high coercivity or as a magnet with low coercivity in a series arrangement. If magnet 410 is used as a magnet with lower coercivity (e.g., a second magnet 104), the effective cross-sectional area will be the largest cross-sectional area within magnet 410 perpendicular to the magnetization direction indicated by arrow 412. If magnet 410 is used as a magnet with higher coercivity (e.g., a first magnet 102), the effective cross-sectional area will be equal to the smallest cross-sectional area within magnet 410 perpendicular to the magnetization direction.

[0066] Figure 4C shows another exemplary permanent magnet 414 in which the magnetization direction lies along multiple directions. Specifically, arrow 416 indicates the magnetization direction of magnet 414. In such an example, the cross-sectional area can be a curved surface within magnet 414, where each direction of magnetization is normal to the curved surface. Multiple such curved surfaces may exist along the length of magnet 414. When magnet 414 is placed in series with other magnets, if it is a magnet with lower coercivity (e.g., a second magnet 104), the effective cross-sectional area of ​​magnet 414 is the area of ​​the largest of the multiple curved surfaces. On the other hand, if magnet 414 has higher coercivity, the effective cross-sectional area is the area of ​​the smallest of the multiple curved surfaces within magnet 414.

[0067] Figure 4D shows yet another example of a permanent magnet in which magnet 418 has a curved shape. Specifically, magnet 418 has a curved shape defined by a first curved surface 420 and a second curved surface 422 separated by the thickness T of the magnet. The magnetization direction indicated by arrow 424 is parallel to one of the radii 426 of the curved shape of magnet 418. Magnet 418 may have multiple cross-sections perpendicular to the magnetization direction. If magnet 418 is a magnet with lower coercivity when placed in series with other magnets (e.g., the second magnet 104), the effective cross-sectional area of ​​magnet 418 is the area of ​​the first plane 428, which has the largest area. On the other hand, if magnet 418 is a magnet with higher coercivity when placed in series with other magnets (e.g., the first magnet 102), the effective cross-sectional area of ​​the magnet is the area of ​​the second plane 430, which has the smallest area. It should be noted that the second plane 430 may be located outside the shape of magnet 418.

[0068] Figure 4E shows yet another example of a permanent magnet in which magnet 432 has a curved shape. In this example, the direction of magnetization may have multiple directions, as indicated by arrow 424. For example, the curved shape of magnet 432 may have multiple radii extending from a virtual center, and the direction of magnetization may extend along these radii. Magnet 432 may include multiple curved surfaces, and for each curved surface, each direction of magnetization is perpendicular to the curved surface. If magnet 432 is a magnet with lower coercivity when placed in series with other magnets (e.g., second magnet 104), the effective cross-sectional area of ​​magnet 432 is the area of ​​the largest of the multiple curved surfaces, in this case the first curved surface 420. On the other hand, if magnet 432 is a magnet with higher coercivity when placed in series with other magnets (e.g., first magnet 102), the effective cross-sectional area of ​​magnet 432 is the area of ​​the smallest of the multiple curved surfaces, in this case the second curved surface 422.

[0069] Please note that the examples described above are not limiting, but are simply provided as examples for determining the cross-sectional area of ​​magnets of different shapes. The cross-sectional area of ​​magnets of different shapes can be determined using the same methods as described above, in relation to Figures 4A to 4E.

[0070] The magnetic devices described herein can be used in several applications. For example, magnetic devices can be used in electrical machinery such as electric motors and generators. Figure 5 is a cutaway section of a permanent magnet motor 500. The portion of the motor 500 shown in Figure 5 is, for example, one pole of the machine 500, specifically one of two poles in a pole pair, and this exemplary machine has three pole pairs. Specifically, the motor 500 includes a rotor 502 and a stator 504 separated by an air gap 506. The stator 504 includes one or more coil windings 510 containing current-carrying conductors. The rotor 502 includes a magnetic device 508. The magnetic device 508 may include at least a first magnet 512, a second magnet 514, and a spacer 516 separating the first magnet 512 and the second magnet 514. The first magnet 512 and the second magnet 514 may be the same as the first magnet 102 and the second magnet 104 described above. In some examples, the magnetic device 508 may not include the spacer 516. In some examples, the additional magnetic poles may or may not include a series configuration of the magnetic device 508, and instead may include only one type of magnet.

[0071] The magnetic device 508 is arranged such that the first magnet 512 is located closer to the air gap 506 than the second magnet 514. This reduces the risk that the magnetic field generated by the energizing conductor of the coil winding 510 will demagnetize the second magnet 514.

[0072] As described above, the series arrangement of the first and second magnets reduces the risk of demagnetization of the second magnet. As a result, the magnets can maintain a higher magnetic field strength. These magnetic fields are generated by the current-carrying conductors in one or more coil windings 510. Therefore, these current-carrying conductors can carry a relatively larger current than if the poles only incorporated the second magnet. Since the maximum torque generated by the motor 500 is a function of the magnitude of the current in one or more coil windings 510, the larger the current, the greater the maximum torque provided by the motor 500.

[0073] Figure 5 shows a magnetic device 508 located on the rotor 502, but it should be understood that the magnetic device 508 may also be located on the stator 504, and one or more coil windings 510 may be located on the rotor 502.

[0074] As described herein, the first magnet may have high coercivity and may include, for example, magnet types such as neodymium-iron-boron type and samarium-cobalt type. As described herein, the second magnet may have low coercivity relative to the coercivity value of the first magnet and may include, for example, magnet types such as iron nitride type. In some examples, iron nitride type magnets may include those described in WO / 2020 / 237192 and WO / 2021 / 168438, each of which is incorporated herein by reference in whole.

[0075] Various modifications to the embodiments described herein will be readily apparent to those skilled in the art, and the general principles defined herein may be applied to other implementations without departing from the spirit or scope of this disclosure. Accordingly, the claims are not intended to be limited to the implementations shown herein, but should be given the broadest scope consistent with this disclosure, the principles disclosed herein, and the novel features.

Claims

1. It is a device, A first magnet having a first remanent magnetization value and a first coercivity value, wherein the first magnet has a first cross-sectional area substantially perpendicular to the magnetization direction of the first magnet, A second magnet arranged in series with the first magnet, the second magnet having a second remanent magnetization value and a second coercivity value smaller than the first coercivity value, and having a second cross-sectional area substantially perpendicular to the magnetization direction of the second magnet, The apparatus wherein the ratio of the first cross-sectional area to the second cross-sectional area is equal to or greater than the ratio of the second remanent magnetization value to the first remanent magnetization value.

2. The apparatus according to claim 1, wherein the second magnet is arranged in the path of the magnetization direction of the first magnet.

3. The apparatus according to claim 1, wherein the second remanent magnetization value is greater than the first remanent magnetization value.

4. The apparatus according to claim 1, wherein the operating point of the second magnet, located in the second quadrant of the BH curve corresponding to the second magnet, is at a magnetic flux density value greater than the magnetic flux density value when the cross-sectional area of ​​the first magnet is equal to the cross-sectional area of ​​the second magnet.

5. The apparatus according to claim 1, wherein the first magnet has a cross-sectional area perpendicular to the magnetization direction of the first magnet and has a shape with a non-constant cross-sectional area, and the first cross-sectional area is equal to the smallest cross-sectional area among the non-constant cross-sectional areas.

6. The apparatus according to claim 1, wherein the second magnet has a cross-sectional area perpendicular to the magnetization direction of the second magnet and has a shape with a non-constant cross-sectional area, and the second cross-sectional area is equal to the largest of the non-constant cross-sectional areas.

7. The apparatus according to claim 1, wherein the first magnet has a first curved shape defined by a first curved surface and a second curved surface separated by the thickness of the first magnet, the magnetization direction of the first magnet is parallel to one of the radii of the first curved shape, and the first cross-sectional area includes the area of ​​a first plane perpendicular to the magnetization direction of the first magnet.

8. The apparatus according to claim 7, wherein the first plane perpendicular to the magnetization direction of the first magnet has the smallest area among the set of planes perpendicular to the magnetization direction of the first magnet.

9. The apparatus according to claim 1, wherein the first magnet has a first curved shape defined by a first curved surface and a second curved surface separated by the thickness of the first magnet, the magnetization direction of the first magnet has a plurality of directions extending along the radius of the first curved shape, and the first cross-sectional area includes the area of ​​the curved surface perpendicular to the plurality of directions.

10. The apparatus according to claim 9, wherein the curved surface perpendicular to the plurality of directions is the curved surface having the smallest area among the set of curved surfaces perpendicular to the plurality of directions.

11. The apparatus according to claim 1, wherein the second magnet has a second curved shape defined by a third curved surface and a fourth curved surface separated by the thickness of the second magnet, the magnetization direction of the second magnet is parallel to one of the radii of the second curved shape, and the second cross-sectional area includes the area of ​​a second plane perpendicular to the magnetization direction of the second magnet.

12. The apparatus according to claim 11, wherein the second plane perpendicular to the magnetization direction of the second magnet has the largest area among the set of planes perpendicular to the magnetization direction of the second magnet.

13. The apparatus according to claim 1, wherein the second magnet has a second curved shape defined by a third curved surface and a fourth curved surface separated by the thickness of the second magnet, the magnetization direction of the second magnet has a plurality of directions extending along the radius of the second curved shape, and the second cross-sectional area includes the area of ​​the curved surface perpendicular to the plurality of directions.

14. The apparatus according to claim 13, wherein the curved surface perpendicular to the plurality of directions is the curved surface having the largest area among the set of curved surfaces perpendicular to the plurality of directions.

15. The apparatus according to claim 1, wherein the first magnet and the second magnet are separated by a spacer.

16. The apparatus according to claim 15, wherein the spacer includes a ferromagnetic material.

17. The apparatus according to claim 15, wherein the cross-sectional area of ​​the spacer is at least equal to the larger of the first cross-sectional area and the second cross-sectional area.

18. The apparatus according to claim 15, wherein the thickness of the spacer is 3 mm or less.

19. The electromachine further includes a stator and a rotor separated from the stator by an air gap, The apparatus according to claim 1, wherein the first magnet and the second magnet are arranged in series with only one of the stator or the rotor.

20. The apparatus according to claim 19, wherein the first magnet is positioned closer to the air gap than the second magnet.

21. The apparatus according to claim 19, wherein the electrical machine comprises a plurality of poles, and at least one of the plurality of poles includes the first magnet and the second magnet.

22. The apparatus according to claim 1, wherein the first magnet is of the neodymium-iron-boron type.

23. The apparatus according to claim 1, wherein the first magnet is of the samarium-cobalt type.

24. The apparatus according to claim 1, wherein the second magnet includes at least one iron nitride type magnet.

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