Magnets in electrical machinery

Abstract

To provide: electrical machines, and more specifically, electrical machines including permanent magnets; wind turbines comprising such electrical machines, and in particular, wind turbines comprising permanent magnet generators with cooling arrangements.SOLUTION: The present disclosure relates to rotors for an electrical machine comprising a first type of permanent magnets and a second type of permanent magnets, where the first and second types of permanent magnets have the same magnetic strength, and where the first type of permanent magnets has a first temperature rating, and the second type of permanent magnets has a second temperature rating different from the first temperature rating. The present disclosure relates to generators, and in particular to wind turbines comprising such generators, and to methods for selecting or providing magnets for permanent magnet rotors.SELECTED DRAWING: Figure 3

Description

Technical Field

[0001] The present disclosure relates to an electromechanical machine, and more particularly to an electromechanical machine including a permanent magnet. The present disclosure also relates to a wind turbine including such an electromechanical machine, and in particular to a wind turbine including a permanent magnet generator having a cooling arrangement.

Background Art

[0002] Electromechanical machines such as motors and generators generally include a rotor structure and a stator structure. Large generators may be, for example, permanent magnet excited generators (PMGs).

[0003] Such generators can be used, for example, in wind turbines. A wind turbine generally includes a rotor having a rotor hub and a plurality of blades. The rotor is configured to rotate under the influence of wind on the blades. The rotation of the rotor shaft directly drives the generator rotor ("direct drive type") or is driven using a gearbox. Such direct drive type wind turbine generators can have, for example, a diameter of 6 to 10 meters (236 to 328 inches), a length of, for example, 2 to 3 meters (79 to 118 inches), and can rotate at a low speed in the range of, for example, 2 to 20 rpm (revolutions per minute). Alternatively, the permanent magnet generator may also be coupled to a gearbox that increases the rotational speed of the generator to, for example, 50 to 500 rpm or more.

[0004] The electromechanical machine includes a rotor that rotates with respect to the stator. The rotor may be an inner structure, and the stator may be an outer structure. Thus, in this case, the stator surrounds the rotor. Alternatively, the configuration may be the opposite, i.e., the rotor may surround the stator.

[0005] In permanent magnet excited generators (PMGs), the permanent magnets (PMs) are generally located in the rotor (although they can also be arranged alternately in the stator structure), while the winding elements (e.g., coils) are usually contained within the stator (although they can also be arranged alternately in the rotor structure). Permanent magnet generators are generally considered reliable and require less maintenance than other types of generators. This is a key reason why permanent magnet generators are used in offshore wind turbines, particularly direct-drive offshore wind turbines.

[0006] Multiple permanent magnets may be provided in a permanent magnet module, and these may be mounted on the rotor as a single component. A permanent magnet module may be defined as a unit having multiple permanent magnets, which can be mounted together and removed together. Such a module may have a module base having a shape suitable for housing or supporting multiple permanent magnets that can be fixed to a base. The base may be configured to be fixed to the rotor rim such that the multiple magnets are fixed together to the rotor rim through the module base. The use of a permanent magnet module can facilitate the manufacture of the rotor.

[0007] Because active elements (magnets or coils) generate heat during use, cooling is generally important in electromechanical systems. Excessively high temperatures can lead to failure of these elements and reduced operational efficiency.

[0008] Different configurations of electromechanical machinery are known, such as radial and axial machines. In axial machines, the rotor and stator face each other axially. An air gap is positioned axially between the rotor and stator. In radial machines, a substantially annular air gap may be formed between the rotor and stator. One of the rotor and stator is positioned to radially surround the other. The motion of the rotor causes air in the air gap to move around it. This allows the air to provide a cooling effect, especially in the case of high-speed rotation.

[0009] An active air cooling system or air conditioning system is known to provide a low-temperature airflow through an internal stator structure. The cooling airflow is then distributed along the circumference of the stator. The airflow then cools the active elements of the rotor and stator by axially crossing the air gap from one side to the other. Hot air is then collected on the opposite axial side. The hot air is then exhausted or cooled in a heat exchanger and can be reused. This type of cooling, in which cooling air axially crosses a radial air gap, is generally referred to as axial cooling.

[0010] Radial cooling is also known, in which cooling air is blown radially into a radial air gap at various points along the axial length of the rotor. Axial cooling is generally preferred for electromachines with short axial lengths, while radial cooling is often preferred for electromachines with long axial lengths.

[0011] When cooling air travels axially across an air gap from one side to the other, the air is heated as it passes through the gap. Therefore, the cooling air is cooler on one side than on the other, and thus one side is cooled more effectively than the other. As a result, the cooling of the active elements is not uniform; that is, the magnets on one side of the rotor may reach a higher temperature than the magnets on the other side.

[0012] Uneven temperature distribution between magnets can affect the operation of electromechanics. Demagnetization is the process by which permanent magnets lose their magnetic properties. Demagnetization occurs in the presence of a strong magnetic field, such as that caused by stator current, especially fault current in electromechanics. Therefore, demagnetization of permanent magnets can occur during use and throughout the lifespan of electromechanics, and demagnetization occurs more rapidly and to a greater extent at high temperatures.

[0013] As mentioned above, if the temperature distribution is non-uniform in the axial direction, magnets located on one side of the rotor may undergo more demagnetization and may be demagnetized more quickly than magnets located on the other side of the rotor.

[0014] The dimensions and types of electromechanical devices and their potential problems described herein are not limited to generators for direct drive applications, nor are they limited to the field of wind turbines. Electromechanical devices of considerable size that may suffer from the same problems and / or have the same complexity may also be found, for example, in steam turbines and hydraulic turbines.

[0015] This disclosure provides examples of systems and methods that address at least partially some of the aforementioned shortcomings. [Overview of the Initiative]

[0016] In a first embodiment, the rotor for an electromechanical device comprises a first type of permanent magnet and a second type of permanent magnet. The first and second types of permanent magnets have the same magnetic strength, the first type of permanent magnet has a first temperature rating, and the second type of permanent magnet has a second temperature rating different from the first temperature rating.

[0017] This embodiment provides a permanent magnet rotor which can cause an uneven temperature distribution along the rotor. Demagnetization of the permanent magnets can occur, for example, when a fault current occurs. To avoid demagnetization, permanent magnets of a sufficiently high "grade" (combination of strength and temperature rating) are usually selected to avoid demagnetization even when the magnets are at their highest temperature. However, high-grade magnets are more expensive than low-grade magnets. A known solution is to increase the cooling of the permanent magnet rotor, thereby reducing the grade of the magnets. However, according to the above embodiment, different grades of magnets can be used in different regions of different temperatures, thereby providing a cost-effective solution.

[0018] Throughout this disclosure, different temperature ratings imply different intrinsic coercivity. Coercivity, or magnetic coercivity, is a measure of a ferromagnetic material's ability to withstand an external magnetic field without demagnetizing. Coercivity is typically measured in Ørsted or amperes / meter, and H CThis is expressed as follows. Larger values ​​represent the intrinsic coercivity H, which considers only magnetization and does not take into account the contribution of the negative vacuum permittivity to the magnetic field B. Ci That is the case.

[0019] Throughout this disclosure, the strength of a permanent magnet can be considered as its magnetic resilience. Resilience, or remanent magnetization, or remanent magnetism, is the magnetization that remains in a ferromagnetic material when an external magnetic field is removed. Throughout this disclosure, the same magnetic resilience or the same magnetic strength means that the difference in magnetic resilience between one magnet and another is less than 10%, specifically less than 5%.

[0020] In a further embodiment, a method is provided that includes the steps of determining the magnetic remnants of permanent magnets in a permanent magnet rotor of an electromachine, and determining the temperature distribution of the permanent magnet rotor in operation. The method then includes the steps of determining a first region of the permanent magnet rotor having a higher average temperature and a second region of the permanent magnet rotor having a lower average temperature. A first type of magnet for the first region and a second type of magnet for the second region are then selected, the second type being different from the first type.

[0021] Non-limiting examples of this disclosure are described below with reference to the attached drawings. [Brief explanation of the drawing]

[0022] [Figure 1] This is a perspective view of an example wind turbine. [Figure 2] This is a detailed internal diagram of a wind turbine nacelle, as an example. [Figure 3] This is a schematic diagram showing a cross-sectional view of an example of an electrical machine. [Figure 4A] This is a diagram illustrating the demagnetization curve in general terms. [Figure 4B] This is a diagram illustrating the demagnetization curve in general terms. [Figure 5A] This diagram schematically shows two examples of permanent magnet modules. [Figure 5B]A diagram schematically showing two examples of a permanent magnet module. [Figure 6] A diagram schematically showing an example of a method for selecting a permanent magnet suitable for a rotor of an electric machine.

Embodiments for Carrying out the Invention

[0023] In these diagrams, the same reference numerals are used to indicate corresponding elements.

[0024] FIG. 1 shows a perspective view of an example of a wind turbine 160. As shown, the wind turbine 160 includes a tower 170 extending from a support surface 150, a nacelle 161 mounted on the tower 170, and a rotor 115 coupled to the nacelle 161. The rotor 115 includes a rotatable hub 110 and at least one rotor blade 120 coupled to the hub 110 and extending outwardly from the hub 110. For example, in the illustrated embodiment, the rotor 115 includes three rotor blades 120. However, in alternative embodiments, the rotor 115 may include more or fewer than three rotor blades 120. Each rotor blade 120 can be spaced around the hub 110 to facilitate rotation of the rotor 115 and enable the kinetic energy from the wind to be converted into mechanical energy that can be used, and subsequently into electrical energy. For example, the hub 110 can be rotatably coupled to a generator 162 (FIG. 2) positioned within the nacelle 161 to enable the generation of electrical energy.

[0025] Figure 2 shows a simplified internal view of an example of the nacelle 161 of the wind turbine 160 of Figure 1. As shown, the generator 162 may be located within the nacelle 161. Generally, the generator 162 may be coupled to the rotor 115 of the wind turbine 160 to generate electricity from the rotational energy generated by the rotor 115. For example, the rotor 115 may include a main rotor shaft 163 coupled to the hub 110 for rotation together with the hub 110. The generator 162 may then be coupled to the rotor shaft 163 so that the rotation of the rotor shaft 163 drives the generator 162. For example, in the illustrated embodiment, the generator 162 includes a generator shaft 166 rotatably coupled to the rotor shaft 163 via a gearbox 164.

[0026] It should be understood that the rotor shaft 163, gearbox 164, and generator 162 can generally be supported within the nacelle 161 by a support frame or bed plate 165 located at the top of the wind turbine tower 170.

[0027] The nacelle 161 is rotatably coupled to the tower 170 by a yaw system 20 so that the nacelle 161 can rotate around the yaw axis YA. The yaw system 20 comprises a yaw bearing having two bearing components configured to rotate relative to the other. The tower 170 is coupled to one of the bearing components, and the bed plate or support frame 165 of the nacelle 161 is coupled to the other bearing component. The yaw system 20 comprises an annular gear 21, a plurality of yaw drive units 22 having motors 23, a gearbox 24, and a pinion 25 for meshing with the annular gear 21 to rotate one of the bearing components relative to the other.

[0028] The blade 120 is coupled to the hub 110 via a pitch bearing 100 between the blade 120 and the hub 110. The pitch bearing 100 comprises an inner ring and an outer ring. The wind turbine blade can be mounted on either the inner bearing ring or the outer bearing ring, and the hub is connected to the other. When the pitch system 107 is activated, the blade 120 can perform rotational motion relative to the hub 110. Thus, the inner bearing ring can perform rotational motion relative to the outer bearing ring. The pitch system 107 in Figure 2 comprises a pinion 108 that meshes with an annular gear 109 provided on the inner bearing ring to rotate the wind turbine blade around the pitch axis PA.

[0029] The energy generated by the generator can be delivered to a converter that adapts the generator's output power to the requirements of the power grid. The electromechanical unit may have electrical phases, for example, three electrical phases. The converter may be located inside the nacelle, inside the tower, or outside.

[0030] Figure 3 schematically illustrates the electrical machinery. The electrical machinery may be a generator, specifically a direct-drive wind turbine generator.

[0031] The generator 10 in Figure 3 comprises a rotor 20 extending from a first side 101 to a second side 102 and configured to rotate around a rotation axis 33, a stator 30, and an air gap 40 between the rotor 20 and the stator 30.

[0032] The stator 30 in this figure comprises a stator structure 50 having a plurality of electric coils 90 and a circumferential support 60 that supports the plurality of electric coils 90. The stator structure 50 extends from a first side 31 to a second side 32 along the rotation axis 33 of the generator.

[0033] The generator 10 in Figure 3 further comprises an air cooling system 110 for cooling a plurality of electric coils 90. In this example, the air cooling system 110 includes an electromechanical air inlet 111, an air distribution channel extending through a portion of the circumferential support 60, and an electromechanical air outlet 112 in fluid communication with the air gap 40. The electromechanical air inlet may allow airflow to enter the electromechanical device.

[0034] The cooling air delivered by the air cooling system 110 can provide low-temperature air to the air gap 40. This air can then cool electromagnetic elements positioned along the air gap, such as the magnets 21 located on the rotor 20, along with the electric coils 90 located on the stator.

[0035] The air distribution channel in this example includes an air entrance 71 located on the first side 31 of the circumferential support 60, which is in fluid communication with the electromechanical air inlet 111. The air distribution channel further includes a plurality of axial air openings 73 located on the second side 32 of the circumferential support 60, which are in fluid communication with the air gap 40, in order to distribute the airflow from the electromechanical air inlet 111 along the air gap 40.

[0036] In this particular example of generator 10, the rotor 20 surrounds the stator 30. The rotor is rotatably mounted to the support frame 9 of the wind turbine via generator bearings 11. The rotor 20 can be connected to the rotor hub of the wind turbine (not shown in this figure) to rotate the rotor hub. The stator 30 can be rigidly connected to the support frame 9 of the wind turbine. The electric windings 90 are located outside the outer rim of the circumferential support, and the magnets or magnet modules 21 may be located inside the outer rotor rim 22.

[0037] In this example, the generator includes a cover plate 12 located on the first side 101. The cover plate 12 can close the generator and can be fixedly attached to the support frame 9 of the wind turbine. A sealing member may be located between the portion of the rotary rim 22 closest to the first side 101 and the cover plate 12.

[0038] In other examples, the cover plate 12 may form part of the rotor 20. In some of these examples, additional generator bearings can rotatably connect the cover plate to the wind turbine support frame. In other examples, the rotor 20 may be radially inward of the stator, i.e., the stator 30 may radially surround the rotor 20. The rotor 20 may be directly coupled to the wind turbine rotor (e.g., to the rotor shaft or rotor hub), or a gearbox may be located between the wind turbine rotor and the generator.

[0039] A low-temperature airflow can enter the generator 10 through the electromechanical air inlet 111. This low-temperature airflow can be guided through the stator structure 50 and a plurality of axial air openings 73 toward the air gap 40 of the generator 10. Thus, the airflow can be distributed substantially uniformly along the circumference of the air gap 40. Thus, this low-temperature airflow can cool the electromagnetic components of the rotor and stator located in the air gap 40. The airflow can pass axially through the air gap from the second side 102 to the first side 101 in order to cool the electromagnetic components located in the air gap. Heat from the electromagnetic components is transferred to the airflow, and the temperature of the airflow at the first side 101 may be higher than that of the airflow at the second side 102. This high-temperature airflow may then exit the generator through the electromechanical air outlet 112 and be cooled in a heat exchanger. The electromechanical air outlet may allow the airflow to exit the electromechanical device.

[0040] Therefore, electromagnetic components placed in an air gap, such as magnets, can operate within a predetermined suitable temperature range, and thus the electromachine can operate efficiently.

[0041] The air cooling system shown in this figure includes a second radial air channel 114 extending radially between the second side 32 of the circumferential support 60 and the second side 102 of the rotor 20. The second radial air channel 114 can connect a plurality of axial air openings 73 to the air gap 40.

[0042] The air cooling system may include a first-side radial air channel 113 extending radially between the first side 31 of the circumferential support 60 and the first side 101 of the rotor 20. The first-side radial air channel 113 can connect the air gap 40 to the electromechanical air outlet 112.

[0043] In some examples, the cooling system may include a heat exchanger. The heat exchanger may comprise a first fluid circuit and a second fluid circuit. The first fluid circuit may be connected to the cooling system to cool an electromechanical unit. The second fluid circuit may cool a fluid flowing along the first fluid circuit. The fluid in the second fluid circuit may be, for example, air or water. The first fluid circuit may include a heat exchanger air inlet connected to an electromechanical air outlet to receive a warm airflow from an air gap. Furthermore, the first fluid circuit may include a heat exchanger air outlet connected to an electromechanical air inlet to deliver an airflow to the air gap. A conduit may be placed between the electromechanical air outlet and the heat exchanger air inlet to guide the airflow toward the heat exchanger. The conduit may connect the heat exchanger air outlet to the electromechanical air inlet.

[0044] The airflow from the air gap can be cooled by a second fluid circuit, and this cooled airflow can be introduced into the electromechanical machine through an electromechanical air inlet to cool the electromagnetic components located in the air gap.

[0045] As mentioned above, the low-temperature airflow can therefore cool the electromagnetic components of the rotor and stator located in the air gap 40. The airflow can pass axially through the air gap from the second side 102 to the first side 101 in order to cool the electromagnetic components located in the air gap. Heat from the electromagnetic components is transferred to the airflow, and the temperature of the airflow at the first side 101 may be higher than that of the airflow at the second side 102. (Cooling) Since the temperature of the airflow may be higher at the first side 101, the cooling of the magnets on this side of the electromachine is carried out with warmer air. Therefore, the cooling may be less effective locally.

[0046] Therefore, the high-temperature magnet 21 may operate at a higher temperature than the magnet on the rotor's cooler side.

[0047] Figure 4A shows the demagnetization curve 205 for a permanent magnet, specifically a neodymium-iron-boron magnet. While demagnetization curve 205 is the "normal" demagnetization curve, the "inherent" demagnetization curve 200 is also shown for the same magnet.

[0048] The demagnetization curve shows the behavior of a magnet at a given temperature and how demagnetization can occur in the presence of a specific magnetic field. Typically, the demagnetization curve 205 shows a knee point 208. As long as the magnetic field is within the linear region 207 of the curve, the properties of the magnet return to their original strength. However, if the magnetic field is above the knee point 208, without the magnetic field, the magnet will not return to its original strength, i.e., its original magnetic remotherapism. Rather, line 209 shows how the magnet returns to a lower remotherapesis, i.e., the magnet is partially demagnetized.

[0049] High magnetic fields that can be partially or completely demagnetized may be caused, for example, by an electrical failure in a generator.

[0050] For different temperatures, different demagnetization curves exist for a given magnet. At higher temperatures, the knee point is reached at a lower magnetic field, meaning demagnetization occurs more easily.

[0051] Figure 4B schematically shows the demagnetization curves 205 and 207 for two types of permanent neodymium magnets with the same strength, i.e., the same magnetic residivity.

[0052] However, magnets have different temperature ratings, i.e., different intrinsic coercivity. Curve 207 (and curve 202) is the demagnetization curve for the permanent magnet N48SH with a higher temperature rating, and curve 205 (and curve 200) is the demagnetization curve for the permanent magnet N48H with a lower temperature rating.

[0053] Demagnetization curves 205 and 207 show demagnetization at a temperature of 80°C. Irreversible demagnetization of the permanent magnet N48SH has been shown to occur at higher magnetic fields.

[0054] In an aspect of the present disclosure (see Figure 3), a rotor 20 for an electromachine 10 is provided, comprising a first type of permanent magnet and a second type of permanent magnet. The first and second types of permanent magnets have the same magnetic strength, the first type of permanent magnet has a first temperature rating, and the second type of permanent magnet has a second temperature rating different from the first temperature rating.

[0055] In the example in Figure 3, the electromachine may comprise a first set of permanent magnets (of the first type) and a second set of permanent magnets (of the second type). That is, different individual magnets can be used. In other examples, the magnetic material may be provided by additive manufacturing. In such examples, variations in magnet grade (especially temperature rating) may be more continuous.

[0056] Permanent magnets may be made from rare earth materials, specifically neodymium-iron-boron magnets. In alternative examples, permanent magnets may be made from, for example, ceramic materials, samarium-cobalt, or alnico (alnico is a group of iron alloys consisting mainly of aluminum (Al), nickel (Ni), and cobalt (Co) in addition to iron).

[0057] In this example, the rotor 20 may have a radial rotor rim extending axially from a first end 102 to a second end 101, with a first set of permanent magnets located in a first area of ​​the rotor and a second set of permanent magnets located in a second area of ​​the rotor, the first area being closer to the first end 102 than the second area.

[0058] In this example, the rotor is configured to be positioned in the electromachine 10 such that the first end 102 is closer to the cooling air supply unit 73 than the second end 101.

[0059] In some examples, the rotor may further comprise a third set of permanent magnets having the same magnetic strength but a third temperature rating different from the first and second temperature ratings. In these examples, three different temperature zones can be defined, and appropriate permanent magnets can be selected for each of these zones. In further examples, four, five, or more different sets of permanent magnets may be provided.

[0060] In examples where magnetic materials are provided using 3D printing or additive manufacturing, a specific number of magnet types (temperature ratings) can be provided, or a continuous change in temperature ratings can be provided.

[0061] In a further embodiment, an electromachine 10 is provided that includes such a rotor. The electromachine 10 may be a generator. In yet another embodiment, there is a wind turbine 160 comprising a tower 170, a nacelle 161 rotatably mounted on the tower 170, and a wind turbine rotor 115 including a plurality of blades 120, wherein the wind turbine rotor 115 is operably connected to the rotor of a generator, and the rotor is the rotor described herein.

[0062] Figures 5A and 5B schematically illustrate two examples of permanent magnet modules for an electromechanical rotor. Figure 5A shows an example of a permanent magnet module 220 having a base 225. The base can be attached to a rotor rim. The base can be attached, for example, using T-shaped anchors that fit inside recesses on both sides of the base 225. Multiple permanent magnets 230 can be arranged on top of the base 225.

[0063] In this example, the permanent magnet module 220 may have the same length as the rotor, that is, the permanent magnet module extends from the first (front) side of the rotor to the second (rear) side of the rotor. The first side 232 of the rotor (and permanent magnet module 220) may be the low-temperature side, and the second side 234 may be the high-temperature side. During operation, the average temperature of the magnets on the low-temperature side 232 may be lower than the average temperature on the high-temperature side.

[0064] A first area 240 having a lower average temperature may be defined, or a second area 242 having a higher average temperature may be defined. The magnets 230 in the first area 240 may be different from the magnets 230 in the second area 242.

[0065] An electromachine is provided comprising a rotor having a plurality of permanent magnets, a stator having a plurality of electric coils, and a radial air gap between the rotor and the stator. The plurality of permanent magnets include a first group of magnets and a second group of magnets, the first group of magnets having a first intrinsic coercivity, and the second group of magnets having a different second intrinsic coercivity. The first group of magnets may be arranged in a first area 240, and the second group of magnets may be arranged in a second area 242.

[0066] In this example, the magnets in the first and second groups have the same magnetic remnants.

[0067] In some examples, the electromachine may further include a cooling supply unit for supplying cooling air to a radial air gap, with the first group of magnets being closer to the cooling supply unit than the second group of magnets. The intrinsic coercivity of the first group may be lower than that of the second group.

[0068] In some examples, the rotor comprises a rotor rim and several permanent magnet modules mounted on the rotor rim.

[0069] In some examples, a set of permanent magnet modules includes a first group of permanent magnet modules and a second group of permanent magnet modules, where the first group of permanent magnet modules contains magnets from the first group, and the second group of permanent magnet modules contains magnets from the second group. The magnet modules do not necessarily have the same axial length as the rotor. In the example, the two magnet modules may be positioned axially one behind the other. One magnet module may have magnets from the first group, and the other magnet module may have magnets from the second group.

[0070] Figure 5B schematically shows another example of the permanent magnet module 250. The permanent magnet module 250 has a substantially V-shaped magnet portion in an axial cross-section. The permanent magnet module 250 for electromechanical applications extends along the axial direction. As mentioned above, the temperature distribution may be non-uniform in the axial direction. A low-temperature side 282 and a high-temperature side 284 may be present.

[0071] Module 250 comprises a permanent magnet assembly having at least one permanent magnet and a base 255 supporting at least a portion of the permanent magnet assembly. The base extends radially (along line AA) from a bottom adapted to be positioned on a rotor of an electromechanical device (not shown) to a top. The permanent magnet assembly comprises a first inclined permanent magnet portion 261 (V-shaped "first leg") and a second inclined permanent magnet portion 262 (V-shaped "second leg") arranged inclined outward along the radial direction (along line AA), and a tangential permanent magnet portion 263 arranged parallel to the tangential direction (along line BB), the tangential direction being substantially perpendicular to the radial direction.

[0072] In the example shown in Figure 5B, the permanent magnet assembly includes a first inclined permanent magnet section 261 comprising a first permanent magnet, a second inclined permanent magnet section 262 comprising a second permanent magnet, and a tangential permanent magnet section 263 comprising a third permanent magnet. Furthermore, the permanent magnet module may comprise several first permanent magnets 261 arranged in a row axially, or second permanent magnets 262 arranged in a row axially, or third permanent magnets 263 arranged in a row axially. Specifically, the axial lengths of these magnets may be similar.

[0073] Several permanent magnet modules may be arranged axially to one another so as to cover the axial length of the electromachine.

[0074] In the example of Figure 5B, the permanent magnet module 250 further comprises a base extending radially from the bottom to the top, which at least partially supports the permanent magnets and is adapted to be positioned on the rotor of an electromachine, the first permanent magnets 261 and the second permanent magnets 262 being arranged inclined outward along the radial direction, and the third permanent magnet 263 being arranged substantially parallel to the tangential direction, which is substantially perpendicular to the radial direction.

[0075] The first and second permanent magnets may be substantially rectangular in their axial cross-section. Alternatively or additionally, the first permanent magnet 261 and the second permanent magnet 262 may have substantially trapezoidal cross-sections. In this way, the fixation of the magnets to the base is improved, and thus the risk of accidental detachment of such magnets can be reduced.

[0076] Additionally, the third permanent magnet 263 may have a rectangular cross-section. In other examples, the third permanent magnet 263 may have a rectangular cross-section with inclined edges.

[0077] An example in Figure 5B shows a base 255 comprising an upper pole piece 273, a first lateral wing 270, and a second lateral wing 272. The permanent magnet assembly may be positioned between the upper pole piece 273 and the first and second lateral wings 270 and 272. In this example, the upper pole piece 273 has a substantially trapezoidal axial cross-section comprising a long side parallel to the short side and a first and second side connecting the long side to the short side. In this example, a third permanent magnet 263 is attached to the short side of the upper pole piece, a first permanent magnet 261 is attached to the first side of the upper pole piece, and a second permanent magnet portion 262 is attached to the second side of the upper pole piece.

[0078] In this example, the first lateral wing 261 and the second lateral wing 262 have a substantially right-angled triangular cross-section.

[0079] As shown in the example in Figure 5A, the base may further include a lateral recess extending along the axial direction. A well-formed anchor can engage with the shape of such a lateral recess and then be used to secure the permanent magnet module to the rotary rim.

[0080] In some examples, the base may include cooling channels 279 for cooling the magnets to avoid overheating of the magnets, which would reduce the efficiency of the electromechanical unit.

[0081] A low-temperature side 282 and a high-temperature side 284 may be present. Magnets 261, 262, and 263 may vary along the axial direction. The lower-temperature region 290 of the permanent magnet module may have lower-grade magnets, and the higher-temperature region 292 may have higher-grade magnets. Specifically, the strength of the magnets may be the same, but the temperature rating may be higher for magnets in the higher-temperature region 292.

[0082] In some examples, one or more permanent magnet modules comprise a first type of magnet and a second type of magnet. The magnet types within a permanent magnet module can be changed axially, as described above.

[0083] Referring particularly to the example in Figure 5B, the permanent magnet module includes one or more inclined magnets 261, 262 arranged at an inclination with respect to the radial direction, and one or more tangential magnets 263 arranged perpendicular to the radial direction, wherein the inclined magnets 261, 262 can be of the first type, and the tangential magnets 263 can be of the second type.

[0084] In this example, the tilt magnets may have a lower temperature rating than the horizontal magnets. During operation, the temperatures of various magnets in the axial plane are actually quite uniform, meaning there may be little difference in temperature among magnets in the same axial plane. However, in the arrangement shown in Figure 5B, the magnetic field of the tangential magnets 263 may be stronger than that of the tilt magnets. For example, in the event of an electrical fault, the magnetic field that can be demagnetized is easier to demagnetize with the tangential magnets 263 than with the tilt magnets 261 and 262. For this reason, the temperature rating or intrinsic coercivity of the tangential magnets 263 can be selected to be higher than that of the tilt magnets.

[0085] The first type of magnet may have a lower temperature rating, such as N48H, and the second type of magnet in these examples may be, for example, N48SH.

[0086] It is also possible to combine both axial-axis variation in magnet type and differentiation within the permanent magnet module.

[0087] Figure 6 schematically illustrates an example of a method 300 for selecting magnets for a permanent magnet rotor of an electromachine. The method includes a step 310 for determining the magnetic remnants of the permanent magnets. Depending on the nominal power of the generator, the number and size of the magnets, etc., the appropriate strength of the permanent magnets can be determined. All magnets in a permanent magnet rotor can have the same strength.

[0088] The method further includes step 330 of determining the temperature distribution of a permanent magnet rotor in operation. The step of determining the temperature distribution may include step 320 of simulating the operation of an electromechanical device.

[0089] The method further includes step 340 of determining a first area of ​​the permanent magnet rotor having a lower average temperature and a second area of ​​the permanent magnet rotor having a higher average temperature. Based on the temperature distribution, two or more areas of the permanent magnet rotor can be defined. In some examples, the first area has an average temperature 10 to 40°C higher than the second area.

[0090] The method in this example further includes the steps of selecting a first type of magnet for a first area and a second type of magnet for a second area, wherein the second type is different from the first type.

[0091] In some cases, the first type of magnet may have a lower temperature rating than the second type of magnet because the first area has a lower average operating temperature. This may occur, for example, if the first area is located near a cooling air supply.

[0092] In some examples, only the first or second type of magnet is selected; that is, only two temperature zones are defined. In many embodiments, it has been found that two temperature zones are sufficient to optimize costs and avoid demagnetization.

[0093] This specification discloses the present invention, including preferred embodiments, using examples, and enables those skilled in the art to practice the invention, including by constructing and using any apparatus or system and by carrying out any incorporated methods. The patentable scope of the present invention is defined by the claims and may include other embodiments that a person skilled in the art may conceive. Such other embodiments are intended to be within the claims if they have structural elements that do not differ from the language of the claims, or if they include equivalent structural elements that do not substantially differ from the language of the claims. A person skilled in the art can construct further embodiments and techniques in accordance with the principles of this application by combining and adapting aspects from the various embodiments described above and other known equivalents for each such aspect. Where reference numerals related to the drawings are placed in parentheses within the claims, those reference numerals are merely for the clarity of the claims and should not be construed as limiting the claims. [Explanation of Symbols]

[0094] 9. Support frame 10 Electrical machinery, generators 11 Generator bearing 12 Cover Plate 20 rotors, yaw system 21 Magnets, magnetic modules, annular gears 22 Rotary rim, yaw drive device 25 pinion 30 staters 31 First side 32 Second side 33 Rotation axis 40 Air gap 50 Stator Structure 60 Circumferential support 71 Air Entrance 73 Cooling air supply unit, axial air opening 90 Electric coils, electric windings 100 pitch bearing 101 First side, second end 102 Second side, first end 107 Pitch System 108 pinion 109 Ring gear 110 hub, air cooling system 111 Electrical and mechanical air inlet 112 Electrical and mechanical air outlet 113 Radial air channel on the first side 114 Second side radial air channel 115 Rotor 120 rotor blades 160 Wind Turbine 161 Nacer 162 Generators 163 Rotor shaft, main rotor shaft 164 Gearbox 165 Support frame, bed plate 170 Tower 200 Demagnetization curve 202 Demagnetization curve 205 Demagnetization curve 207 Demagnetization curve, linear area 208 Knee Point 220 Permanent Magnet Module 225 Base 230 magnets 232 First side, low temperature side 240 First area 242 Second area 250 permanent magnet module 255 Base 261 Inclined magnet, inclined permanent magnet section, first permanent magnet, first lateral wing 262 Inclined magnet, inclined permanent magnet section, second permanent magnet, second permanent magnet section, second lateral wing 263 Tangential magnet, third permanent magnet, tangential permanent magnet portion 270 First lateral wing 272 Second lateral wing 273 Upper pole piece 279 cooling channels 282 Low temperature side 284 High temperature side Areas with temperatures below 290°C Areas with temperatures above 292°C 300 ways PA pitch axis YA yaw axis

Claims

1. A rotor (20) for an electromachine (10) comprising a first type of permanent magnet and a second type of permanent magnet, The first type of permanent magnet and the second type of permanent magnet have the same magnetic strength. The first type of permanent magnet has a first temperature rating, and the second type of permanent magnet has a second temperature rating different from the first temperature rating. The rotor (20) comprises a rotor rim (22) and a plurality of permanent magnet modules (220, 250), and each of the permanent magnet modules has a base attached to the rotor rim (22). A rotor (20) in which one or more of the permanent magnet modules (220, 250) comprises the first type of magnet disposed at the base and the second type of magnet or magnetic portion disposed at the base.

2. The rotor (20) according to claim 1, wherein the permanent magnet is made from a rare earth material.

3. The rotor (20) extends axially from the first end (102) to the second end (101), The first set of permanent magnets is arranged in the first area (240) of the permanent magnet module. A second set of permanent magnets is placed in the second area (242) of the permanent magnet module. The rotor (20) according to claim 1 or claim 2, wherein the first area (240) is closer to the first end (102) than the second area.

4. The rotor (20) according to claim 3, configured such that the first end (102) is positioned on the electromachine (10) closer to the cooling air supply unit (73) than the second end (101).

5. The rotor (20) according to any one of claims 1 to 4, further comprising a third set of permanent magnets, wherein the third set of permanent magnets has the same magnetic intensity and a third temperature rating different from the first and second temperature ratings.

6. The plurality of permanent magnet modules (220, 250) include a first group of permanent magnet modules and a second group of permanent magnet modules, The rotor (20) according to any one of claims 1 to 5, wherein a first group of permanent magnet modules comprises a first type of magnet, and a second group of permanent magnet modules comprises a second type of magnet.

7. The permanent magnet module (220, 250) includes one or more inclined magnets (261, 262) arranged at an inclination with respect to the radial direction, and one or more tangential magnets (263) arranged perpendicular to the radial direction. The rotor (20) according to any one of claims 1 to 6, wherein the inclined magnets (261, 262) are of the first type, and the tangential magnet (263) is of the second type.

8. An electric machine (10) comprising a rotor (20) according to any one of claims 1 to 7, wherein the electric machine (10) is a generator (162).

9. A wind turbine (160) comprising a tower (170), a nacelle (161) rotatably mounted on the tower (170), a wind turbine rotor (115) including a plurality of blades (120), and a generator (162) according to claim 8, wherein the generator (162) is of the direct drive type.

10. Step (310) of determining the magnetic residuality of the permanent magnets of the permanent magnet rotor of an electrical machine (10), wherein the permanent magnet rotor includes a rotor rim, Step (330) of determining the temperature distribution of the operating permanent magnet rotor, The steps (340) include determining a first area of ​​the permanent magnet rotor having a lower average temperature and determining a second area of ​​the permanent magnet rotor having a higher average temperature, Step (350) of selecting a first type of magnet for the first area (232) and a second type of magnet for the second area (234), wherein the second type is different from the first type. The steps of providing a permanent magnet module including the first type of magnet and the second type of magnet on a base, The steps of attaching the base to the rotary rim A method including (300).

11. The method according to claim 10 (300), wherein the first type of magnet has a lower temperature rating than the second type of magnet.

12. The method (300) of claim 10 or claim 11, wherein the step of determining the temperature distribution of the operating permanent magnet rotor includes the step (320) of simulating the operation of the electromechanism (10).

13. The method according to any one of claims 10 to 12 (300), wherein the first type of magnet and the second type of magnet are provided by additive manufacturing.

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