Cooling of active elements of electrical machines

Abstract

To provide electrical machines and methods for cooling active elements of the electrical machines.SOLUTION: The present disclosure relates to electrical machines and methods for cooling active elements of the electrical machines. More specifically, the present disclosure relates to generators and methods for cooling adjacent active rotor elements and / or adjacent active stator elements of a generator of a wind turbine, e.g. of a direct drive wind turbine. An electrical machine comprises a rotor including a plurality of active rotor elements, a stator including a plurality of active stator elements, and an air gap separating the active rotor elements and the active stator elements. The electrical machine further comprises a radiation absorber arranged between first and second adjacent active rotor elements or between first and second adjacent active stator elements.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present disclosure relates to electric machines and methods for cooling active elements of electric machines, and more particularly to generators and methods for cooling adjacent active rotor elements and / or adjacent active stator elements of wind turbines, such as generators of direct drive wind turbines. [Background technology]

[0002] Electric machines, such as motors and generators, generally comprise a rotor structure and a stator structure. Large generators may be, for example, electric excitation generators or permanent magnet excitation generators (PMG). The rotor of an electric machine rotates relative to the stator. The rotor may be an inner structure and the stator may be an outer structure. Thus, the stator in this case surrounds the rotor, for example, radially. Alternatively, the configuration may be reversed, i.e., the rotor surrounds the stator, for example, radially.

[0003] Such generators can be used, for example, in wind turbines. A wind turbine generally comprises a rotor having a rotor hub and a number of blades. The rotor is configured to rotate under the influence of wind on the blades. The rotation of the rotor shaft either directly drives the generator rotor ("direct drive") or is driven using a gearbox.

[0004] Direct drive wind turbine generators may have a diameter of, for example, 6 to 10 meters (236 to 328 inches), a length of, for example, 2 to 3 meters (79 to 118 inches), and may rotate at low speeds, for example, in the range of 2 to 20 rpm (revolutions per minute). Alternatively, the generator may also be coupled to a gearbox that increases the rotational speed of the generator, for example, to 50 to 500 rpm or more.

[0005] Cooling is generally important in electric machines, such as generators in direct-drive wind turbines. In particular, the active elements of the rotor and stator, such as permanent magnets and coils, can generate heat. Increased temperatures in the active rotor and stator elements can lead to failure of the active elements and reduce the efficiency of the generator. To reduce the temperature of the active rotor and stator elements, a cooling fluid may be flowed through an air gap separating the active elements. The cooling fluid contacts the active elements and removes heat from them. A cooling system may be provided to direct the cooling fluid toward and away from the air gap, thus removing heat from the active rotor and stator elements.

[0006] Thermal radiation emitted by active elements, i.e., electromagnetic radiation of a thermal nature, primarily in the infrared region of the electromagnetic spectrum, increases the temperature of adjacent active elements. According to the Stefan-Boltzmann law, the power radiated by an object, here an active element, increases as the fourth power of the object's temperature. Therefore, a relatively small increase in the temperature of an active element can cause a corresponding increase in the power radiated by the active element.

[0007] Furthermore, the emissivity of the surface of the active elements (emissivity may be defined as the ratio of thermal radiation from a surface to the radiation from an ideal black surface at the same temperature, as given by the Stefan-Boltzmann law) may be close to 1, i.e., may be particularly effective at emitting energy as thermal radiation. For example, the emissivity of a coil may be approximately 0.9 or greater. Thus, a first active element may heat an adjacent second active element by radiation, thus further increasing the temperature of the second active element, and vice versa. For example, two adjacent active stator elements or two adjacent active rotor elements may heat each other by thermal radiation.

[0008] Thermal radiation therefore increases the cooling requirements of the active elements of the electric machine, potentially requiring more powerful cooling systems to cool the active elements. Thermal radiation also limits the power that a generator, for example, can output, because the temperature of the active elements may not overcome a temperature threshold above which element failure occurs. Summary of the Invention

[0009] In one aspect of the present disclosure, an electric machine is provided. The electric machine includes a rotor and a stator. The rotor includes a plurality of active rotor elements, and the stator includes a plurality of active stator elements. The electric machine further includes an air gap separating the active rotor elements and the active stator elements. The electric machine further includes a radiation absorber disposed between first and second adjacent active rotor elements or between first and second adjacent active stator elements.

[0010] According to this aspect, a radiation absorber is provided between two adjacent elements of the rotor or two adjacent elements of the stator. When the active elements heat up during use, the radiation absorber absorbs at least a portion of the thermal radiation emitted by the adjacent active element, thereby preventing at least a portion of the thermal radiation emitted by a first active element from reaching a second active element, and vice versa. A cooling fluid can flow through the adjacent active elements and thus along the radiation elements to reduce the temperature of the active elements and the radiation absorber, for example by convection.

[0011] Therefore, the temperature of the adjacent active elements can be reduced compared to a situation in which the radiation absorber is not present. The reduced temperature of the active elements can extend the lifetime of the active elements. Also, the size of the cooling system fluidly connected to the active elements can be reduced. Additionally, the output of the electric machine can be increased. The power generation of the electric machine can be increased because the active elements may be able to withstand higher temperatures, which may not reach a temperature threshold above which the active elements may fail. Depending on the power production and lifetime requirements of the active elements, a balance may be struck between extending the lifetime of the active elements and increasing the power output of the electric machine.

[0012] A radiation absorber may be understood throughout this disclosure as an element capable of absorbing incident thermal radiation. The higher the absorptivity of a radiation absorber, the better its absorption performance. Absorptivity may be understood throughout this disclosure as the ratio of electromagnetic radiation, particularly thermal radiation, incident on a surface that is absorbed by the surface. Absorptance may also be known as absorptance. Throughout this disclosure, thermal radiation may be considered to be electromagnetic radiation, particularly at a non-zero temperature, in the wavelength range of 0.1 μm to 100 μm. The term thermal radiation is frequently used to distinguish this form of electromagnetic radiation from other forms, such as radio waves, X-rays, or gamma rays.

[0013] As used throughout this disclosure, active elements can be considered to be magnetically and / or electrically active rotor and / or stator elements. Active stator elements may be, for example, one or more permanent magnets, one or more permanent magnet modules, one or more coils, or one or more coil modules. Active rotor elements may similarly be one or more permanent magnets, one or more permanent magnet modules, one or more coils, or one or more coil modules. For example, an active stator element may be a coil, and an active rotor element may be a permanent magnet module. In other examples, both the active stator element and the active rotor element may be coils.

[0014] The electric machine may be a generator, in particular a generator for a wind turbine, more particularly a generator for a direct drive wind turbine.

[0015] In a further aspect, a method is provided that includes rotating a rotor of an electric machine, the method further including flowing a cooling fluid between adjacent active rotor elements and between adjacent active stator elements, and causing the cooling fluid to flow around a plurality of radiation absorbers included at least between one of the adjacent active rotor elements and the adjacent active stator element.

[0016] In yet another aspect, a generator for a wind turbine is provided, the generator comprising: a rotor including a plurality of active rotor elements; a stator including a plurality of active stator elements; and an air gap separating the active rotor elements and the active stator elements. The generator further comprises a plurality of radiation absorbing sheets disposed between adjacent active rotor elements and / or adjacent active stator elements. [Brief explanation of the drawings]

[0017] [Figure 1] FIG. 1 is a schematic diagram illustrating a perspective view of an example wind turbine. [Figure 2] 1 illustrates an example of a hub and nacelle of a wind turbine. [Figure 3] 1 is a schematic diagram illustrating an enlarged cross-sectional view of an electric machine according to an example. [Figure 4] FIG. 4 shows a schematic perspective view of the electric machine of FIG. 3 with some active rotor elements removed. [Figure 5] 5A and 5B show schematic diagrams of some examples of radiation absorbers in enlarged cross-sectional views of the electric machines of FIGS. 3 and 4; [Figure 6] FIG. 10 shows a schematic flow chart of an example method for cooling active rotor and / or stator elements. DETAILED DESCRIPTION OF THE INVENTION

[0018] Reference will now be made in detail to the embodiments of the present disclosure, one or more examples of which are illustrated in the drawings. Each example is provided as an illustration of the present disclosure, not as a limitation of the disclosure. Indeed, it will be apparent to those skilled in the art that various modifications and variations can be made in the present disclosure without departing from the scope and spirit of the disclosure. For example, features illustrated or described as part of one embodiment can be used with another embodiment to yield yet a further embodiment. Accordingly, the present disclosure is intended to cover such modifications and variations as come within the scope of the appended claims and their equivalents.

[0019] Although reference is made primarily herein to generators for direct drive wind turbines, the examples disclosed herein are applicable to electric machines in general.

[0020] FIG. 1 is a perspective view of an example wind turbine 10. In this example, wind turbine 10 is a horizontal axis wind turbine. Alternatively, wind turbine 10 may be a vertical axis wind turbine. In this example, wind turbine 10 includes a tower 15 extending from a support system 14 on ground 12, a nacelle 16 mounted to tower 15, and a rotor 18 coupled to nacelle 16. Rotor 18 includes a rotatable hub 20 and at least one rotor blade 22 coupled to and extending outward from hub 20. In this example, rotor 18 has three rotor blades 22. In alternative embodiments, rotor 18 includes more or fewer than three rotor blades 22. Tower 15 may be fabricated from tubular steel to define a cavity (not shown in FIG. 1 ) between support system 14 and nacelle 16. In alternative embodiments, tower 15 is any suitable type of tower having any suitable height. Alternatively, the tower may be a hybrid tower with a concrete section and a tubular steel section. The tower may also be a partial or full lattice tower. Wind turbine 10 may be installed both on land and offshore.

[0021] Rotor blades 22 may be spaced about hub 20 to facilitate rotation of rotor 18 so that kinetic energy can be transferred from the wind to usable mechanical energy and subsequently to electrical energy. Rotor blades 22 are mated to hub 20 by coupling blade root portions 24 to hub 20 at a plurality of load transfer areas 26. Load transfer areas 26 may include hub load transfer areas and blade load transfer areas (both not shown in FIG. 1 ). Loads induced in rotor blades 22 are transferred to hub 20 through load transfer areas 26.

[0022] In examples, rotor blades 22 may have lengths ranging from about 15 meters (m) to about 90 m or more. Rotor blades 22 may have any suitable length that enables wind turbine 10 to function as described herein. For example, non-limiting examples of blade lengths include lengths of 20 m or less, or lengths of 37 m, 48.7 m, 50.2 m, 52.2 m, or greater than 91 m. When wind strikes rotor blades 22 from wind direction 28, rotor 18 rotates about rotor axis 30. As rotor blades 22 rotate and experience centrifugal forces, rotor blades 22 also experience various forces and moments. Thus, rotor blades 22 may deflect and / or rotate from a neutral or unbiased position to a biased position.

[0023] Furthermore, the pitch angle of the rotor blades 22, i.e., the angle determining the orientation of the rotor blades 22 relative to the wind direction, may be varied by a pitch system 32 to control the load and power generated by the wind turbine 10 by adjusting the angular position of at least one rotor blade 22 relative to the wind vector. A pitch axis 34 of the rotor blades 22 is also shown. During operation of the wind turbine 10, the pitch system 32 may particularly vary the pitch angle of the rotor blades 22 such that the angle of attack of (some of) the rotor blades is reduced, thereby facilitating a reduction in rotational speed and / or facilitating stalling of the rotor 18.

[0024] In this example, the blade pitch of each rotor blade 22 is individually controlled by the wind turbine controller 36 or pitch control system 80. Alternatively, the blade pitch for all rotor blades 22 may be controlled simultaneously by the control system.

[0025] Additionally, in this example, as wind direction 28 changes, the yaw direction of nacelle 16 may be rotated about yaw axis 38 to position rotor blades 22 relative to wind direction 28 .

[0026] In this example, wind turbine controller 36 is shown as being centralized within nacelle 16, but wind turbine controller 36 may be a distributed system throughout wind turbine 10, on support system 14, within a wind farm, and / or at a remote control center. Wind turbine controller 36 includes a processor 40 configured to perform the methods and / or steps described herein. Additionally, many of the other components described herein include a processor.

[0027] As used herein, the term "processor" is not limited to integrated circuits referred to in the art as computers, but refers broadly to controllers, microcontrollers, microcomputers, programmable logic controllers (PLCs), application specific integrated circuits, and other programmable circuits, and these terms are used interchangeably herein. It should be understood that a processor and / or control system may also include memory, input channels, and / or output channels.

[0028] 2 is an enlarged cross-sectional view of a portion of wind turbine 10. In this example, wind turbine 10 includes a nacelle 16 and a rotor 18 rotatably coupled to nacelle 16. More specifically, a hub 20 of rotor 18 is rotatably coupled to an electric generator 42 positioned within nacelle 16 by a main shaft 44, a gearbox 46, a high-speed shaft 48, and a coupling 50. In this example, main shaft 44 is disposed at least partially coaxially with a longitudinal axis (not shown) of nacelle 16. Rotation of main shaft 44 drives gearbox 46, which in turn drives high-speed shaft 48 by converting the relatively slow rotational motion of rotor 18 and main shaft 44 into relatively faster rotational motion of high-speed shaft 48. The latter is connected to generator 42 for producing electrical energy with the aid of coupling 50. Furthermore, a transformer 90 and / or appropriate electronics, switches, and / or inverters may be disposed in the nacelle 16 to convert the electrical energy generated by the generator 42 having a voltage of 400V to 1000V into electrical energy having a medium voltage (10 to 35 kV). The electrical energy is conducted from the nacelle 16 to the tower 15 via a power cable.

[0029] The gearbox 46, generator 42, and transformer 90 may be supported by a main support structure frame of the nacelle 16, which may optionally be embodied as a main frame 52. The gearbox 46 may include a gearbox housing connected to the main frame 52 by one or more torque arms 103. In this example, the nacelle 16 also includes a main forward support bearing 60 and a main aft support bearing 62. Additionally, the generator 42 may be mounted to the main frame 52 by an isolation support means 54, particularly to prevent vibrations of the generator 42 from being introduced into the main frame 52 and thereby causing a source of noise emissions.

[0030] Optionally, the main frame 52 is configured to carry the weight of the rotor 18 and nacelle 16 components, as well as the overall loads caused by wind and rotational loads, and to introduce these loads into the tower 15 of the wind turbine 10. The rotor shaft 44, the generator 42, the gearbox 46, the high-speed shaft 48, the coupling 50, and any associated fastening, supporting, and / or securing devices, including, but not limited to, the supports 52, the forward support bearing 60, and the aft support bearing 62, may be referred to as a drive train 64.

[0031] In some examples, the wind turbine may be a direct drive wind turbine without a gearbox 46. The generators 42 operate at the same rotational speed as the rotor 18 in direct drive wind turbines. Therefore, they generally have a much larger diameter than the generators used in wind turbines with gearboxes 46 to provide a similar amount of power as wind turbines with gearboxes.

[0032] The nacelle 16 may also include a yaw drive mechanism 56 that can be used to rotate the nacelle 16, and thus the rotor 18, about the yaw axis 38 to control the balance of the rotor blades 22 relative to the wind direction 28.

[0033] To properly position the nacelle 16 relative to the wind direction 28, the nacelle 16 may also include at least one meteorological measurement system, which may include a wind vane and an anemometer. The meteorological measurement system 58 may provide information, which may include the wind direction 28 and / or wind speed, to the wind turbine controller 36. In this example, the pitch system 32 is at least partially disposed within the hub 20 as a pitch assembly 66. The pitch assembly 66 includes one or more pitch drive systems 68 and at least one sensor 70. Each pitch drive system 68 is coupled to a respective rotor blade 22 (shown in FIG. 1 ) to modulate the pitch angle of the rotor blade 22 along the pitch axis 34. Only one of the three pitch drive systems 68 is shown in FIG. 2 .

[0034] In this example, pitch assembly 66 includes at least one pitch bearing 72 coupled to hub 20 and each rotor blade 22 (shown in FIG. 1 ) to rotate each rotor blade 22 about pitch axis 34. Pitch drive system 68 includes a pitch drive motor 74, a pitch drive gearbox 76, and a pitch drive pinion 78. Pitch drive motor 74 is coupled to pitch drive gearbox 76 such that pitch drive motor 74 imparts mechanical power to pitch drive gearbox 76. Pitch drive gearbox 76 is coupled to pitch drive pinion 78 such that pitch drive pinion 78 is rotated by pitch drive gearbox 76. Pitch bearing 72 is coupled to pitch drive pinion 78 such that rotation of pitch drive pinion 78 causes rotation of pitch bearing 72.

[0035] Pitch drive system 68 is coupled to wind turbine controller 36 to adjust the pitch angle of rotor blades 22 upon receiving one or more signals from wind turbine controller 36. In this example, pitch drive motor 74 is any suitable motor driven by an electrical and / or hydraulic system that enables pitch assembly 66 to function as described herein. Alternatively, pitch assembly 66 may include any suitable structure, configuration, arrangement, and / or components, such as, but not limited to, hydraulic cylinders, springs, and / or servo mechanisms. In certain embodiments, pitch drive motor 74 is driven by the rotational inertia of hub 20 and / or energy extracted from a stored energy source (not shown) that provides energy to components of wind turbine 10.

[0036] Pitch assembly 66 may also include one or more pitch control systems 80 for controlling pitch drive systems 68 according to control signals from wind turbine controller 36 for certain priority conditions and / or during overspeed of rotor 18. In this example, pitch assembly 66 includes at least one pitch control system 80 communicatively coupled to each pitch drive system 68 for controlling pitch drive systems 68 independently from wind turbine controller 36. In this example, pitch control system 80 is coupled to pitch drive systems 68 and sensors 70. During normal operation of wind turbine 10, wind turbine controller 36 may control pitch drive systems 68 to adjust the pitch angle of rotor blades 22.

[0037] According to one embodiment, a power generator 84, comprising, for example, a battery and an electrical capacitor, is disposed at or within the hub 20 and is coupled to the sensors 70, the pitch control system 80, and the pitch drive system 68 to provide a source of electrical power to these components. In this example, the power generator 84 provides a continuous source of electrical power to the pitch assembly 66 during operation of the wind turbine 10. In an alternative embodiment, the power generator 84 provides electrical power to the pitch assembly 66 only during a power loss event of the wind turbine 10. A power loss event may include a loss or degradation of the electrical grid, a malfunction of the electrical system of the wind turbine 10, and / or a failure of the wind turbine controller 36. During a power loss event, the power generator 84 operates to provide electrical power to the pitch assembly 66 so that the pitch assembly 66 can operate during the power loss event.

[0038] In this example, pitch drive system 68, sensor 70, pitch control system 80, cables, and power generator 84 are each positioned within a cavity 86 defined by an inner surface 88 of hub 20. In alternative embodiments, the components may be positioned relative to and directly or indirectly coupled to the outer surface of hub 20.

[0039] In one aspect of the disclosure, an electric machine 100 is provided. The electric machine 100 comprises a rotor 110 and a stator 120. The rotor 110 comprises a plurality of active rotor elements 115, and the stator comprises a plurality of active stator elements 125. The electric machine 100 further comprises an air gap 116 separating the active rotor elements 115 and the active stator elements 125. The electric machine 100 further comprises a radiation absorber 130 disposed between first and second adjacent active rotor elements 111, 112 or between first and second adjacent active stator elements 121, 122.

[0040] FIG. 3 shows a schematic enlarged cross-section of the electric machine 100. In this example, the electric machine 100 is a radial machine, specifically a generator 42. The generator may be a generator for the wind turbine 10, more specifically for a direct-drive wind turbine. The active rotor elements 115 are permanent magnet modules and the active stator elements 125 are coils, although other active rotor elements and stator elements are possible. For example, both the active rotor elements and the active stator elements may be coils. As shown in FIG. 3, the stator coils 125 are wound around the stator teeth 119.

[0041] A permanent magnet module can be defined as a unit having multiple permanent magnets such that the multiple magnets can be attached and detached together. Such a module may have a module base having a shape suitable for housing or receiving the multiple permanent magnets. The magnets may be secured to the base in various ways. The base may be configured to be secured to a field rim, e.g., a rotor rim, such that the multiple magnets are secured together to the field rim via the module base. The use of permanent magnet modules can facilitate the manufacture of a generator field.

[0042] 3, rotor 110 surrounds stator 120, but in other examples, stator 120 may surround rotor 110. Similarly, other configurations and types of electric machine 100 may be used. For example, electric machine 100 may be an axial machine, such as an axial generator. In some other examples, electric machine 100 may be a motor.

[0043] The electric machine 100 further includes a radiation absorber 130 between two adjacent active elements, in this illustration between two adjacent active stator elements 125, such as coils, in a circumferential direction 132. The electric machine 100 may include one or more radiation absorbers 130 in the stator 120 and / or one or more radiation absorbers 130 in the rotor 110. For example, the electric machine 100 may include a radiation absorber 130 between each pair of adjacent active stator elements 125. Alternatively or additionally, the electric machine 100 may include a radiation absorber 130 between each pair of adjacent active rotor elements 115.

[0044] The radiation absorber 130 may have an absorptivity greater than 0.8, more specifically greater than 0.9, and even more specifically greater than 0.95. In some examples, the absorptivity of the radiation absorber may be approximately 0.98. The absorptivity can indicate how efficiently the radiation absorber absorbs thermal radiation. The closer the absorptivity value is to 1, the better the absorber. In some examples, the radiation absorber 130 may be black.

[0045] In some examples, the radiation absorber 130 may have a surface that has been treated to have suitable or enhanced heat absorption properties. The radiation absorber may have, for example, a thermal radiation absorbing coating. The radiation absorber 130 may be painted with a thermal radiation absorbing paint, such as an infrared absorbing paint. One or more thermal radiation, e.g., infrared radiation, absorbing films or foils may be used to cover (partially or entirely) the radiation absorber. The radiation absorber 130 may comprise both a thermal radiation absorbing paint and a film.

[0046] In some examples, the radiation absorber 130 may comprise one or more metal alloys. Metal alloys may be suitable for efficiently absorbing thermal radiation. Metal alloys may include, for example, silver alloys, copper alloys, aluminum alloys, or brass alloys. The surface of the metal alloy radiation absorber 130 may be treated, for example, painted with one or more thermal radiation absorbing paints and / or covered with one or more thermal radiation absorbing films or foils.

[0047] The radiation absorber 130 may be positioned in an intermediate region between two adjacent active stator elements 121, 122 or between two adjacent active rotor elements 111, 112. That is, the radiation absorber 130 may be positioned such that the distance 135a between the radiation absorber 130 and a first adjacent active element 111, 121 is similar to or substantially the same as the distance 135b between the radiation absorber 130 and a second adjacent active element 112, 122. The distances 135a, 135b between the radiation absorber and the active elements may be measured in the circumferential direction 132 at a given radial height.

[0048] By placing a radiation absorber 130 between two adjacent active elements 111, 112 of a rotor or between two adjacent active elements 120, 121 of a stator, the use of cooling fluid between adjacent active elements can be improved, especially when the distances 135a, 135b from the absorber 130 to the adjacent elements are substantially the same. Without the radiation absorber 130, only a portion of the cooling fluid adjacent to or in contact with the active elements is heated and carries away heat to reduce the temperature of the active elements. However, when the radiation absorber 130 is used, a portion of the cooling fluid adjacent to or in contact with the absorber 130 is also heated and carries away heat. Therefore, better use of cooling fluid can be achieved by placing the radiation absorber 130 between two adjacent active rotor elements or active stator elements, especially when the radiation absorber 130 is located at substantially the same distances 135a, 135b from the active elements. Therefore, cooling efficiency can be improved.

[0049] In the example of Figure 3, it can be seen that the spacing between adjacent coils increases slightly in the radial direction. In this particular example, the thickness of the radiation absorber sheet 130 is constant. In other examples, the thickness of the radiation absorber may vary in the radial direction. In some examples, the thickness of the radiation absorber may vary so that the distance to adjacent coils (or magnets) is substantially constant in the radial direction, i.e., along the height of the radiation absorber.

[0050] The radiation absorber 130 may have a length, e.g., a length in an axial direction 131, a height, e.g., a height in a radial direction 133, and a width, e.g., a width in a circumferential direction 132. The radiation absorber may have a thickness, i.e., width, of 0.1 to 5 millimeters (mm), more specifically 0.1 to 3 mm, and more specifically 0.2 to 1 mm, e.g., about 0.5 mm.

[0051] Placing a radiation absorber 130 between adjacent active elements 115 in the rotor 110 or between adjacent active elements 125 in the stator 120 may impede the flow of cooling fluid between the adjacent active elements. In some examples, the thickness of the radiation absorber 130 may be, for example, 1% to 20%, more specifically 1% to 10%, or even more specifically 2% to 5% of the distance 135 between adjacent active elements 121, 122. Although the flow of cooling fluid may be reduced, this reduction may be compensated for by the heat absorption provided by the radiation absorber 130.

[0052] Within this range, the loss of cooling due to the placement of the radiation absorber 130 between adjacent active elements can be compensated for by the increased heat removal provided by the radiation absorber 130. In some instances, the flow of cooling fluid may be reduced by 2-4% due to the placement of the radiation absorber 130, but the radiation absorber 130 can increase cooling by approximately 10%, thereby improving heat removal.

[0053] The radiation absorber 130 may extend partially or entirely along a dimension of the active elements 115, 125. Like the radiation absorber 130, the active elements 115, 125 may have a length, e.g., a length in the axial direction 131, a height, e.g., a height in the radial direction 133, and a width, e.g., a width in the circumferential direction 132. The radiation absorber 130 may extend partially or entirely along any of the dimensions of the active elements 115, 125. For example, in FIG. 3, the radiation absorber 130 extends entirely along the height of the active elements 125.

[0054] The active elements 115, 125 may be connected, e.g., attached, to the rotor or stator rim. The height of the active elements 115, 125 may generally be measured substantially perpendicular to the local surface of the rotor or stator rim to which the active elements are connected, e.g., attached. Similarly, the height of the radiation absorber 130 may be measured substantially perpendicular to the local surface of the rotor or stator rim to which the active elements are connected, e.g., attached.

[0055] The radiation absorber can be mounted to the electric machine in a variety of ways. In examples such as that of FIG. 3, the radiation absorber (e.g., a sheet) may be mounted to the stator rim or rotor rim. That is, the radiation absorber may be mounted to or near the "legs" or base of the coils, or the base of the permanent magnets (modules). In other examples, the radiation absorber may be attached at one or more points to adjacent active elements. For example, adhesives may be used for this purpose. Combinations of these mounting methods are also possible.

[0056] FIG. 4 schematically illustrates an enlarged perspective view of the electric machine 100 of FIG. 3 with some active rotor elements removed. Multiple coils 125 wound around the stator teeth 119 can be seen. As in FIG. 3, the active rotor element 115 is a permanent magnet module. Two radiation absorbers 130 can be seen between adjacent coils. The radiation absorbers 130 may extend partially or entirely along the length of the active elements 115, 125. In FIG. 4, the radiation absorbers 130 extend partially along the length of the coils 125 (measured along the axial direction 131).

[0057] The active elements 115, 125, such as the coils of Figure 4, may have a central portion 128, a first longitudinal end 126, and a second opposing longitudinal end 127. In Figure 4, the radiation absorber 130 does not extend between adjacent ends 126, 127 of the coil 125. In other examples, the radiation absorber 130 may extend between, e.g., only between, the ends 126, 127 of adjacent active elements. The radiation absorber 130 may extend between the first ends 126 and / or the second ends 127 of the active elements.

[0058] In some examples, such as those shown in FIGS. 3 and 4, the radiation absorber 130 may be a sheet. The sheet may be disposed in the relatively small gap 117 between adjacent active elements and may have a shape suitable for optimizing absorption of thermal radiation emitted by the active elements. The sheet may have a first side and a second side. The first side may be positioned to face the first active element 121, and the second side may be positioned to face the second active element 122. The sheet may have a thickness, i.e., width, of 0.1 to 5 millimeters (mm), more specifically 0.2 to 1 mm, e.g., about 0.5 mm.

[0059] The radiation absorber 130 may extend beyond the active elements 115, 125. FIG. 5 shows some examples of radiation absorbers in an enlarged cross-sectional view of the electric machine 100 of FIGS. 3 and 4. In this example, the rotor radiation absorber 130' extends into the air gap 116 beyond the adjacent active rotor elements 111, 112. The stator radiation absorber 130 also extends into the air gap 116 beyond the adjacent active stator elements 121, 122. The rotor radiation absorber 130' curves around the first active element 111 and around the second active element 112. The rotor radiation absorber 130' has a generally T-shaped cross section in this example, but may have other shapes in other examples. The stator radiation absorber 130 curves around the first active stator element 121. The stator radiation absorber 130 has a generally L-shaped cross section in this example, but may have other shapes in other examples. The radiation absorber 130, 130' may be configured to extend beyond one or more adjacent active elements 115, 125 and conform to the contours of one or more of the adjacent active elements 115, 125.

[0060] In some examples, the radiation absorber 230, 230′ may be configured to form a cooling channel 231. It will be understood that the radiation absorber is configured to form a cooling channel 231 if it is configured to be part of the cooling channel 231 that may guide a cooling fluid. The radiation absorber 230 in this case may be attached directly to the rim (in this case the rim of the rotor, although it is clear that the same is possible for a stator) at two points: between the first and second active elements and between the second and third active elements.

[0061] The cooling channel 231 has a closed cross-sectional profile. The cross-section of the cooling channel (and radiation absorber) can be interpreted as being substantially perpendicular to the direction in which cooling fluid is injected between adjacent active elements. For example, the cooling fluid may flow axially 131 through the cooling channel 231, and the cross-section may extend radially 133 and circumferentially 132. When attached to, for example, a rotor or stator, the radiation absorber 230, 230' may form part of a conduit. For example, the radiation absorber may form one or more walls of the conduit.

[0062] When a cooling fluid, e.g., air, is introduced into the cooling channels 231, contact between the cooling fluid and the active elements can be enhanced. Therefore, cooling efficiency can be improved compared to cooling without a radiation absorber forming a cooling channel. Note that increased contact between the cooling fluid and the active elements can also be achieved by a radiation absorber that does not form the cooling channels 231. For example, in FIG. 5, the radiation absorbers 130 and 130′ can also increase contact between the cooling fluid and adjacent active elements while restricting the movement of the cooling fluid in the circumferential direction 132. Therefore, cooling can be enhanced relative to a situation in which the radiation absorbers 130 and 130′ are not present.

[0063] In some examples, the end 232 of the radiation absorber may be attached to the active element support 119 to form the cooling channel 231. For example, if the active stator element 125 is a coil, the end 232 of the radiation absorber may be attached to the tooth 190 around which the coil is wound. An example of attachment to the tooth 119 is shown schematically in FIG. 5, where a short wall of an L-shaped radiation absorber 230 is attached to the tooth 119 of the coil 122. In such an example, as long as the absorber 230 is bonded to the tooth 119 along, for example, the entire length (axial direction 131) of the coil 122, the flow of cooling fluid toward the air gap 116 can be avoided.

[0064] In some examples, the ends of the radiation absorber may be attached to the active elements to form the cooling channels 231. For example, if the radiation absorber 131′ of FIG. 5 were to form the cooling channels, the ends extending in the circumferential direction 132 may be attached to the active rotor elements 111 and 112, for example, without entering the air gap 116.

[0065] In some examples, the radiation absorber 230' may have a C-shaped or U-shaped cross section. For example, a radiation absorber may be provided that is configured to completely surround an active element, e.g., rotor element 115, in cross section. In such a case, a radiation absorber 230' is provided that is bonded to the rotor rim and completely surrounds, e.g., active rotor element 111, as shown schematically in FIG.

[0066] The radiation absorber 130, 130', 230, 230' configured to form a cooling channel may include one or more walls. For example, if the cross-sectional shape of the radiation absorber is C-shaped, the radiation absorber may be said to have one wall. However, for example, if the radiation absorber has an L-shaped, T-shaped, or U-shaped cross-section, the radiation absorber may be formed by two or more walls. Two walls, for example, the first and second walls, may be substantially perpendicular between them.

[0067] The radiation absorber 130, 130', 230, 230' can be joined or connected to the rotor or stator rim by any suitable fastener or means. In some examples, T-blocks or wedges may be used as fasteners. The radiation absorber 130 does not necessarily have to be attached directly to the rotor or stator rim, but may be attached to the base of one or more active element supports 119. For example, as shown in the example of FIG. 3, the radiation absorber 130 may be attached between two teeth 119 configured to support a coil.

[0068] In a further aspect of the present disclosure, there is provided a method 300. The method is illustrated schematically in FIG.

[0069] The method includes, at block 310, rotating a rotor 110 of an electric machine 100. The electric machine 100 may be the electric machine 100 described with respect to Figures 3-5. That is, the electric machine includes a rotor 110 and a stator 120, the rotor 110 including a plurality of active rotor elements 115, and the stator 120 including a plurality of active stator elements 125. The electric machine further includes an air gap 116 separating the active rotor elements 115 and the active stator elements 125. In some examples, the electric machine 100 may be a generator 42, particularly a generator for a wind turbine, more particularly a generator for a direct drive wind turbine.

[0070] The method further includes, in block 320, flowing a cooling fluid between adjacent active rotor elements 115 and between adjacent active stator elements 125, and causing the cooling fluid to flow around a plurality of radiation absorbers 130 included at least between one of the adjacent active rotor elements 115 and the adjacent active stator element 125.

[0071] According to this aspect, thermal radiation emitted by adjacent active elements can be absorbed by the radiation absorber 130 disposed between the adjacent active elements. When the cooling fluid contacts the radiation absorber 130 as it flows around the radiation absorber 130, the cooling fluid can remove heat from the radiation absorber 130 (and the active elements 115, 125) by convection. Although the radiation absorber 130 may impede the flow of cooling fluid between adjacent active elements, the thermal radiation absorbed by the radiation absorber 130, and therefore the heat that does not reach the adjacent active elements, can compensate for the cooling effect lost by impeding the flow of cooling fluid by disposing the radiation absorber 130 on the rotor and / or stator 120.

[0072] The radiation absorber 130 may be disposed on the rotor 110 and / or the stator 120. The radiation absorber 130 may have one or more features previously described with respect to Figures 3-5. For example, the radiation absorber 130 may be an alloy metal sheet.

[0073] The cooling fluid may be air in some examples. The cooling fluid may flow axially 131 between the active rotor elements and between the active stator elements in some examples.

[0074] Rotor rotation may be initiated before, after, or substantially simultaneously with turning on the cooling fluid.

[0075] In some examples, rotating the rotor includes rotating a plurality of wind turbine blades 22 through the action of the wind. In these examples, the electric machine 100 is a generator 42. The generator 42 may be directly driven or may be driven via a gearbox.

[0076] In a further aspect of the present disclosure, a generator 42 for a wind turbine 10 is provided. The generator 42 comprises a rotor 110 and a stator 120. The rotor comprises a plurality of active rotor elements 115. The stator comprises a plurality of active stator elements 125. The generator further comprises an air gap 116 separating the active rotor elements 115 and the active stator elements 125. The generator 42 further comprises a plurality of radiation absorbers 130 disposed between adjacent active rotor elements 111, 112 and / or between adjacent active stator elements 121, 122.

[0077] The air gap 116 may be a radial 133 air gap in some examples.

[0078] In some examples, the plurality of radiation absorbers 130 may be a plurality of sheets. In some examples, one or more of the plurality of sheets, such as all of the sheets, may have a thickness of 0.1 to 5 millimeters, more specifically 0.1 to 3 millimeters, and more specifically 0.2 to 1 millimeter.

[0079] In some examples, the absorbency of the plurality of sheets, i.e., each sheet of the plurality of sheets, may be 0.95 or greater.

[0080] The explanations regarding Figures 3 to 5 apply to this embodiment.

[0081] This specification uses examples to disclose the present teachings, including preferred embodiments, and also enables one of ordinary skill in the art to practice the teachings disclosed herein, including making and using any device or system and performing any incorporated methods. The patentable scope is defined by the claims, and may include other examples that occur to those of ordinary skill in the art. Such other examples are intended to be within the scope of the claims if they have structural elements that do not differ from the literal language of the claims, or if they include equivalent structural elements that do not have substantial differences from the literal language of the claims. Those skilled in the art will be able to mix and match aspects from the various embodiments described above, as well as other known equivalents for each such aspect, to construct further embodiments and techniques consistent with the principles of the present application. Where reference signs relating to the drawings are placed within parentheses in the claims, these reference signs are merely to enhance the clarity of the claims and should not be construed as limiting the scope of the claims. [Explanation of symbols]

[0082] 10. Wind Turbines 12 Ground 14 Support System 15 Tower 16 Nacelle 18 rotors 20 Hub 22 Wind turbine blades 24 Blade base 26 Load Transfer Area 28 Wind direction 30 rotor shaft 32 Pitch System 34 Pitch axis 36 Wind Turbine Controller 38 Yaw axis 40 processors 42 Generator 44 rotor shaft, main shaft 46 Gearbox 48 High Speed ​​Shaft 50 Coupling 52 Main frame, support 54 Separation support means 56 Yaw drive mechanism 58 Weather Measurement System 60 Main forward support bearing 62 Main rear support bearing 64 Drivetrain 66 Pitch Assembly 68 Pitch Drive System 70 sensors 72 Pitch bearing 74 Pitch drive motor 76 Pitch drive gearbox 78 Pitch drive pinion 80 Pitch Control System 84 Electric Power Generator 86 Hollow 88 Inner 90 Transformer 100 Electrical Machinery 110 rotor 103 Torque arm 111 active rotor element, first active element, first adjacent active element 112 active rotor element, second active element, second adjacent active rotor element 115 Active rotor element 116 Air Gap 119 Active element support, stator tooth 120 Active element, stator 121 first active element, first active stator element, first adjacent active element 122 second active element, active stator element, coil, second adjacent active element 125 Active elements, active stator elements, stator coils 126 first end, longitudinal end 127 second end, longitudinal end 128 Central part 130 Radiation absorber 130' Radiation Absorber 131 Axial 131' Radiation absorber 132 Circumferential direction 133 Radial 135 distance 135a distance 135b distance 190 teeth 230 Radiation absorber 230' Radiation absorber 231 Cooling Channel 232 End 300 ways

Claims

1. A rotor (110) comprising a plurality of active rotor elements (115), a stator (120) comprising a plurality of active stator elements (125), an air gap (116) separating the active rotor elements (115) from the active stator elements (125), and a radiation absorber (130) disposed between the first and second adjacent active rotor elements (115) and / or between the first and second adjacent active stator elements (125). Comprising the radiation absorber (130) is configured to absorb incident thermal radiation emitted from the first and second adjacent active rotor elements (115) and / or the first and second adjacent active stator elements (125), a circumferential distance (135a) exists between the radiation absorber (130) and the first active rotor element (115) and / or the active stator element (125), during use, a cooling fluid flows between the radiation absorber (130) and the first active rotor element (115) and / or the active stator element (125), and between the radiation absorber (130) and the second adjacent active rotor element (115) and / or the active stator element (125), and from the radiation absorber (130) heated by the absorbed incident thermal radiation, and from the first and second adjacent active rotor elements (115) and / or the first and second adjacent active stator elements (125), and a circumferential distance (135b) exists between the radiation absorber (130) and the second adjacent active rotor element (115) and / or the active stator element (125) to carry away heat, an electromechanical machine (100).

2. The radiation absorber (130) of the electromechanical machine (100) according to claim 1 has an absorption rate for thermal radiation of 0.8 or more, specifically 0.9 or more, and more specifically 0.95 or more.

3. The radiation absorber (130) of the electromechanical machine (100) according to claim 1 is arranged to have substantially the same distance from the first and second adjacent active elements (115, 125).

4. The radiation absorber (130) has a thickness of 1% to 20%, more specifically 1% to 10%, and even more specifically 2% to 5% of the distance between the first adjacent active element (115) and the second adjacent active element (125), for the electromechanical device (100) according to claim 1.

5. The radiation absorber (130) extends substantially completely along the height of the active element, the height being measured substantially perpendicular to the local surface of the rotary rim or the stator rim to which the first and second active elements (115, 125) are connected, for the electromechanical device (100) according to claim 1.

6. The radiation absorber (130) comprises one or more metal alloys, for the electromechanical device (100) according to claim 1.

7. The radiation absorber (130) has a surface treated to enhance its heat radiation absorption performance, for the electromechanical device (100) according to claim 1.

8. The radiation absorber (130) is a sheet having a first face facing the first active element (115) and a second face facing the second active element (125), for the electromechanical device (100) according to claim 1.

9. The sheet has a thickness of 0.1 to 5 millimeters, more specifically 0.1 to 3 millimeters, and even more specifically 0.2 to 1 millimeter, for the electromechanical device (100) according to claim 8.

10. The radiation absorber (130) has a thickness that varies along its height, and optionally, the distance from the radiation absorber (130) to the adjacent active element is substantially constant, for the electromechanical device (100) according to claim 1.

11. The radiation absorber (130) is configured to extend into the air gap (116) beyond one or more adjacent active elements, for the electromechanical device (100) according to claim 1.

12. The radiation absorber (130) is adapted to conform to the contour of one or more of the adjacent active elements, for the electromechanical device (100) according to claim 1.

13. The electromechanical device (100) according to any one of claims 1 to 12, which is a generator (42).

14. The generator (42) according to claim 13, which is a permanent magnet generator.

15. A wind turbine (10) comprising the generator (42) according to claim 13.

Images