Cooling of coils of electrical machines

Abstract

To provide electrical machines comprising coils, and methods for cooling coils of a generator of a wind turbine, e.g., coils of a stator of a direct drive wind turbine.SOLUTION: The present disclosure relates to coils 121, electrical machines comprising the coils 121, (e.g., a wind turbine generator), and methods for cooling the coils 121 of the electrical machines and for winding and / or electrically insulating the coils 121. An electrical machine comprises a rotor and a stator. At least one of the rotor and the stator comprises a plurality of teeth and a plurality of coils 121, the coils 121 comprising a strand which is wound around the teeth in layers 130, 131. A first axial end portion of a first layer 131 of at least one of the coils 121 is axially displaced with respect to a first axial end portion of a second layer 131 of the coil 121.SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] The present disclosure relates to electric machines including coils and methods for cooling coils of electric machines. More particularly, the present disclosure relates to electric generators including coils and methods for cooling coils of generators of wind turbines (e.g., coils of the stators of direct drive wind turbines). The present disclosure also relates to coils and methods for winding and / or electrically insulating coils. [Background technology]

[0002] Electric machines (such as motors and generators) typically include a rotor structure and a stator structure. Large generators are, for example, electrically excited generators or permanent magnet excited generators (PMG). The rotor of an electric machine rotates relative to the stator. The rotor can be the inner structure and the stator the outer structure. In this case, the stator surrounds the rotor, e.g., radially. Alternatively, the reverse configuration can be used, i.e., the rotor surrounds the stator, e.g., radially.

[0003] Such generators can be used, for example, in wind turbines. A wind turbine typically includes a rotor having a rotor hub and a number of blades. The rotor rotates when the wind blows on the blades. As the rotor shaft rotates, it drives the rotor of the generator either directly ("direct drive") or by using a gearbox.

[0004] A direct drive wind turbine generator may be, for example, 6 meters to 10 meters (236 inches to 394 inches) in diameter, 2 meters to 3 meters (79 inches to 118 inches) long, and may rotate at a low speed, for example, in the range of 2 rpm to 20 rpm (revolutions per minute). Alternatively, the generator may be coupled to a gearbox that increases the rotational speed of the generator, for example, to a speed between 50 rpm and 500 rpm, or even higher.

[0005] Cooling is generally important in electric machines (such as generators in direct drive wind turbines). In particular, the electromagnetic or "active" elements of the generator can heat up, for example, the permanent magnets and the rotor and stator coils. Increased coil temperature can lead to coil failure and reduce the efficiency of the generator. Coil temperature can effectively limit the nominal power output of the generator; in effect, the amount of power produced by the generator can be limited by a maximum allowable temperature threshold.

[0006] To reduce the temperature of the active elements, a cooling fluid (such as air) can be passed through the air gap separating the rotor coils and the active elements. The cooling fluid contacts the active elements and removes heat from them. A cooling system can be provided that directs the cooling fluid toward and away from the air gap, thus removing heat from the active elements of the generator. In practice, heating of the coils is generally much more significant than heating of the permanent magnets.

[0007] During operation of a wind turbine, heating of active elements is not necessarily uniform. For example, a coil may heat up more at its axial ends (specifically, the axial ends further from the cooling fluid inlet and closer to the cooling fluid outlet). It is known to supply air to an air gap along the axial direction of the generator from multiple inlets and remove air from the generator through multiple outlets. In this case, the axial end of the coil closer to the inlet is cooled more than the axial end of the coil closer to the outlet because the cooling air is heated as it passes axially through the air gap.

[0008] In addition to the cooling air being at a higher temperature when it reaches the axial ends of the coils near the outlet, the cooling air may not follow the curvature of the coils at these axial ends, i.e., the contact (and therefore the heat exchange) between the cooling air and these ends of the coils may not be very good. Also, one or more coil support elements (such as teeth and optionally other additional elements around which the coils are positioned) generally do not aid in cooling the coils.

[0009] The present disclosure is directed to improving cooling of coils in electric machines. Summary of the Invention

[0010] In one aspect of the disclosure, an electric machine is provided. The electric machine includes a rotor and a stator. At least one of the rotor and the stator includes a plurality of teeth and a plurality of coils, each of the coils including one or more strands wound in layers around the teeth. The coil includes a first axial end, a central portion, and a second axial end opposite the first axial end. The layer of coils includes a first axial end, a central portion, and a second axial end opposite the first axial end. The first axial end of the first layer of at least one of the plurality of coils is axially offset relative to the first axial end of the second layer of coils.

[0011] According to this embodiment, the ends of the two layers at the first axial end of the coil are axially offset, i.e., the end of one layer protrudes axially beyond the end of the other layer.

[0012] This increases the surface area of ​​the first axial end of the coil exposed to the cooling fluid. Also, making the first axial end irregular can create turbulence in the cooling fluid, allowing the first axial end of the coil to be cooled more efficiently.

[0013] Throughout this disclosure, a coil may be formed by a stack of layers or turns of electrical conductor around a core (e.g., one or more copper strands). Each layer may be electrically insulated from the others and may be formed by two generally straight, parallel portions (the center of the layer) and two curved portions (the axial ends of the layer). Each layer is continuous with the layer immediately above or below it. Electrical insulation between layers may be achieved, for example, by insulating tape.

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

[0015] In another aspect, a method of insulating a coil is provided, the method comprising bending conductive strands to form layers of coils, wherein a first axial end of a first layer of the coil is offset longitudinally of the coil relative to a first axial end of a second layer of the coil, the method further comprising electrically insulating the first axial ends of the first layer and the second layer.

[0016] According to another aspect, a generator for a wind turbine is provided. The generator includes a rotor, a stator, and a radial air gap separating the rotor and the stator. The stator includes a plurality of teeth and a plurality of coils wound in layers around the teeth. The coils include a first layer, the first layer having an axial end that is axially offset from an axial end of a second layer adjacent to the first layer. The axial ends of the first layer and the second layer are in the same axial region of the coil. [Brief explanation of the drawings]

[0017] [Figure 1] 1 shows a schematic perspective view of an example wind turbine; [Figure 2] 1 shows an example of a hub and nacelle of a wind turbine. [Figure 3] 1 shows a schematic enlarged cross-sectional view of an example electric machine; [Figure 4]4A and 4B show schematic enlarged top views of two examples of a stator as seen from the air gap. [Figure 5] 5A and 5B are schematic enlarged views of an example of a central cross section of the coil taken along line AA in FIGS. 4A and 4B, respectively. [Figure 6] 4B shows a schematic enlarged view of another example of a central cross section of the coil of FIG. 4A taken along line AA. [Figure 7] 1 shows a schematic enlarged view of another example of a central longitudinal cross section of a coil, the cross section including a direction parallel to the length of the coil and the height of the coil. [Figure 8] 8A-8C show schematic enlarged top views of an example coil with support inserts positioned at the ends of the coil. [Figure 9] 8D is a schematic diagram of a central longitudinal section of FIG. 8C. [Figure 10] 10A and 10B show schematic diagrams of two example enlarged tips of a coil and a scoop for directing the flow of cooling fluid. [Figure 11] FIG. 1 is a schematic diagram of a flow chart of an example method for insulating a coil. [Figure 12] 12A and 12B show schematic diagrams of two examples of preformed elements for electrically insulating the axial ends of layers of a coil. [Figure 13] 1 shows a schematic representation of an example of an electrically insulating strand before being folded to form a coil, specifically with thicker insulation at the axial end portions of the strand. DETAILED DESCRIPTION OF THE INVENTION

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

[0019] Although reference will be made primarily to generators for direct drive wind turbines, the invention is applicable to electrical 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 mounted on ground 12, a nacelle 16 attached 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 may be any suitable type of tower having any suitable height. Alternatively, the tower may be a hybrid tower including portions made of concrete and portions made of steel pipes. Additionally, the tower may be a partial or full lattice tower. The wind turbine 10 may be located on land or offshore.

[0021] Rotor blades 22 are spaced about hub 20 to rotate rotor 18 and convert kinetic energy from the wind into usable mechanical energy and then electrical energy. Rotor blades 22 are mated to hub 20 by connecting blade roots 24 to hub 20 at a plurality of load transfer regions 26. Load transfer regions 26 may include hub load transfer regions and blade load transfer regions (both not shown in FIG. 1 ). Loads induced on rotor blades 22 are transferred to hub 20 through load transfer regions 26.

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

[0023] Additionally, 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) can 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 shown. During operation of the wind turbine 10, the pitch system 32 can vary the pitch angle of the rotor blades 22 to, among other things, reduce the angle of attack of (some of) the rotor blades, which can reduce the rotational speed and / or stall the rotor 18.

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

[0025] Furthermore, in this embodiment, as wind direction 28 changes, the yaw direction of nacelle 16 can 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 centrally located within nacelle 16, however, wind turbine controller 36 may be a distributed system located throughout wind turbine 10, 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 a generator 42 disposed within nacelle 16 by a main shaft 44, a gearbox 46, a high-speed shaft 48, and a coupling 50. In the illustrative embodiment, main shaft 44 is at least partially coaxial 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. High-speed shaft 48 is connected by coupling 50 to generator 42 for generating electrical energy. Further, 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, e.g., at a voltage between 400V and 1000V, into medium voltage (10KV-35KV) electrical energy. Offshore wind turbines may have a generator voltage between 650V and 3500V, e.g., and the transformer voltage may have a voltage between 30kV and 70kV, e.g., The electrical energy is conducted from the nacelle 16 to the tower 15 through 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 an embodiment, the nacelle 16 also includes a main forward support bearing 60 and a main aft support bearing 62. Furthermore, the generator 42 may be mounted to the main frame 52 by a decoupling support means 54, particularly to prevent vibrations of the generator 42 from being introduced into the main frame 52 and thereby becoming a source of noise emissions.

[0030] Optionally, the main frame 52 is configured to support the overall loads caused by the weight of the rotor 18 and nacelle 16 components, as well as 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 associated fasteners, supports, and / or fixtures (e.g., but not limited to, the supports 52, and the forward and aft support bearings 60, 62) may be referred to as a drive train 64.

[0031] In some embodiments, the wind turbine may be a direct drive wind turbine without a gearbox 46. The generator 42 operates at the same rotational speed as the rotor 18 of the direct drive wind turbine. Therefore, the generator used in a direct drive wind turbine typically has a much larger diameter than the generator used in a wind turbine with a gearbox 46 in order to provide the same amount of power as a wind turbine with a gearbox.

[0032] The nacelle 16 may also include a yaw drive mechanism 56. The yaw drive mechanism 56 may be used to rotate the nacelle 16, and therefore the rotor 18, about the yaw axis 38 to control the orientation 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 including 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 embodiment, 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 adjust 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 the illustrative embodiment, 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, and pitch drive motor 74 provides mechanical power to pitch drive gearbox 76. Pitch drive gearbox 76 is coupled to pitch drive pinion 78, and pitch drive pinion 78 is rotated by pitch drive gearbox 76. Pitch bearing 72 is coupled to pitch drive pinion 78, and rotation of pitch drive pinion 78 causes pitch bearing 72 to rotate.

[0035] The pitch drive system 68 is coupled to the wind turbine controller 36 and may adjust the pitch angle of the rotor blades 22 upon receiving one or more signals from the wind turbine controller 36. In this example, the pitch drive motor 74 may be any suitable motor powered by an electric and / or hydraulic system that enables the pitch assembly 66 to function as described herein. Alternatively, the 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, the pitch drive motor 74 is powered by energy extracted from the rotational inertia of the hub 20 and / or energy extracted from a stored energy source (not shown) that provides energy to components of the 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 rotor 18 over-speed. In an embodiment, 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 an embodiment, 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 such that the pitch angle of rotor blades 22 is adjusted.

[0037] According to one embodiment, a generator 84, including, for example, a battery and an electrical capacitor, is disposed on or within the hub 20, and the generator 84 is coupled to and provides power to the sensors 70, the pitch control system 80, and the pitch drive system 68. In this example, the generator 84 continuously provides power to the pitch assembly 66 during operation of the wind turbine 10. In an alternative embodiment, the generator 84 provides power to the pitch assembly 66 only during a power loss event of the wind turbine 10. The power loss event may include an electrical grid outage or voltage dip, a failure in the wind turbine 10's electrical system, and / or a failure of the wind turbine controller 36. During a power loss event, the generator 84 operates to provide power to the pitch assembly 66, allowing the pitch assembly 66 to operate during the power loss event.

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

[0039] In one aspect of the disclosure, an electric machine is provided. An enlarged cross-section of an example electric machine 100 is shown schematically in Figure 3. The cross-section in Figure 3 is perpendicular to the axis 142 of the rotor, stator, and therefore the electric machine. Although the rotor and stator are shown as extending linearly (i.e., horizontally), in practice both the rotor and stator may be curved if there is a radial air gap between the active elements.

[0040] Enlarged top views of two example stators as viewed from the air gap between the rotor and stator are shown schematically in Figures 4A and 4B, and enlarged views of example central longitudinal sections of the coils taken along line AA in Figures 4A and 4B are shown schematically in Figures 5A and 5B, respectively.

[0041] The electric machine 100 includes a rotor 110 and a stator 120 (see FIG. 3). At least one of the rotor 110 and the stator 120 includes a plurality of teeth 119 and a plurality of coils 121. The coils 121 include strands wound in layers 130, 131 around the teeth 119. The coils 121 include a first axial end 123, a central portion 124, and a second axial end 125 opposite the first axial end 123 (see FIGS. 4A and 4B). As used herein, the axial end may be considered to include the bends in each layer of strands. As used herein, the central portion may be considered to include the straight portions of the layers of strands.

[0042] Similarly, the layer of coils includes a first axial end, a center portion, and a second axial end opposite the first axial end. The first axial end of the first layer 130 of at least one of the plurality of coils 121 is axially offset (117) relative to the first axial end of the second layer 131 of coils 121.

[0043] Thus, at the same axial end of the coil, at least one axial end of the layers of the coil 121 is axially offset relative to another end of the layers of the coil 121. For example, at a first axial end 123 of the coil 121, the end of one layer 130 is offset in the axial direction 142 relative to the end of an adjacent layer 131. Thus, at the axial ends 123, 125 of the coil 121, the surface area of ​​the layers 130, 131 exposed to the cooling fluid (e.g., cooling air in an air gap) is increased. This improves cooling of the axial ends of the coil 121.

[0044] The axial offset can also contribute to creating turbulence in the cooling fluid when it reaches the corresponding axial end of the coil, again improving cooling. It also increases the stiffness of the coil, making it more resistant to bending under electromagnetic load.

[0045] In some cases, the cooling fluid can be air. In some cases, the cooling fluid can flow axially 142 between the coils 115 (see, for example, FIG. 3). In particular, the axial ends further from the cooling air inlet can benefit from the strand arrangement described above to improve cooling.

[0046] 3, the electric machine 100 is a radial electric machine (particularly, a generator 42). The generator may be a generator for a wind turbine 10, more particularly, a generator for a direct drive wind turbine. Although the stator 120 includes a plurality of coils 121 and the rotor 110 includes a plurality of permanent magnet modules 111, in other embodiments, the coils 121 may be provided only on the rotor 110, or the coils 121 may be provided on both the rotor 110 and the stator 121.

[0047] The generator 100 further includes an air gap 116 separating the active rotor elements 111 (in this example, permanent magnet modules) and the active stator elements 121 (in this example, coils). The air gap 116 may be a radial air gap.

[0048] Active elements can be considered as elements that act magnetically and / or electrically on the rotor and / or stator. Active elements can be, for example, permanent magnets, permanent magnet modules, single coils or pole shoes, or pole shoes containing multiple coils. As shown in the example of Figure 3, active elements 111, 121 are connected (e.g., directly attached or attached through other elements) to the corresponding rotor or stator rims.

[0049] A permanent magnet module 111 can be defined as a unit that can collectively install and remove multiple permanent magnets. Such a module can have a module base that has a shape suitable for housing or accepting multiple permanent magnets. The magnets can be secured to the module base in various ways. The module base can be secured to a field rim (e.g., a rotor rim), and the multiple magnets can be secured to the field rim via the module base. The use of a permanent magnet module can facilitate the formation of a magnetic field for a generator.

[0050] 3, the rotor 110 surrounds the stator 120, but in other examples, the stator 120 may surround the rotor 110. Similarly, other configurations and types of electric machine 100 may be used. For example, the electric machine 100 may be an axial machine (e.g., an axial generator). In other examples, the electric machine 100 may be a motor.

[0051] First axial end 123 is farther away from an inlet of electric machine 100 configured to receive a cooling fluid for cooling coil 121 than second axial end 125. Electric machine 100 may include an inlet for receiving a cooling fluid and an outlet for discharging heated cooling fluid after contacting the coil. Thus, axial offset 117 at the axial end proximate the outlet may facilitate cooling of coil 121 and improve operation of electric machine 100.

[0052] In this regard, a cooling system may be provided for cooling at least the coils 121 of the electric machine 100. Such a cooling system may include a primary or "main" path (or primary or main loop). The main loop may include a fluid inlet for a cooling fluid. The cooling fluid may be transported to the coils from a fluid inlet of the electric machine. In some examples, air may be delivered to the air gap 116 between the stator coils 121 and the permanent magnets 111. During operation, the coils heat up, and the cooling fluid (which may be air) also heats up. The heated cooling fluid then flows to a fluid outlet of the electric machine.

[0053] In some examples, the fluid outlet and inlet can be in fluid communication with the outside of the machine. For example, in the case of a wind turbine, the outlet and inlet can be in fluid communication with the air surrounding the nacelle. For example, the cooling system can include a fan, e.g., within the nacelle, to draw air from the outside of the wind turbine through the fluid inlet for the cooling fluid. A conduit can transport the cooling fluid from the cooling fluid inlet to the generator air gap, and the conduit can then transport the heated cooling fluid from the generator air gap to the fluid outlet. Some or all of the heated cooling fluid can be exhausted to the outside.

[0054] In some examples, the fluid inlet and fluid outlet ports can be in fluid communication with a heat exchanger, where the temperature of the cooling fluid used to cool the coils is reduced as it flows through the air gap. Conduits can be used to direct heated cooling fluid into the heat exchanger and, once cooled, to discharge the cooled fluid. The cooled cooling fluid can be redirected, for example, to the air gap between the rotor permanent magnets and the stator coils. The above systems can also be combined; for example, some of the cooling fluid can be discharged and some recirculated.

[0055] The first axial end 123, which includes the offset layer of strands, can be the axial end of the coil 121 where the coil is not electrically connected to other parts of the electrical circuit (e.g., to a bus bar or another coil). In the example of Figures 4A and 4B, the second axial end 125 is the axial end where the electrical connection 113 is located, while the first axial end 123 does not have an electrical connection located thereon.

[0056] The first layer 130 and the second layer 131 may be adjacent layers. That is, the first layer 130 may be axially offset relative to the second layer 131 adjacent to the first layer 130. The layers may be adjacent along a radial direction 144 of the electric machine 100 (and thus of the stator 120 and rotor 110). Generally, the coil 121 may include multiple layers stacked together (see, e.g., FIGS. 5A and 5B). Each layer may include multiple strands. The stacking direction may define the height of the coil. When the coil is positioned in the electric machine (e.g., around a stator tooth 119), the coil may have a height measured in the radial direction 144. In the example of FIGS. 5A and 5B, the coil 121 includes 10 layers. In other examples, the coil may include a different number of layers.

[0057] In some examples, the first layer 130 is an outer layer of the coil 121, and the first axial end of the first layer 130 extends axially less than the first axial end of the second layer 131 (see, for example, FIGS. 4A and 4B). The axial ends of the layers at least partially overlap.

[0058] In this configuration, both the outer layer and the layer adjacent to the outer layer are exposed to a cooling fluid (e.g., air), but without adding excessive material (and therefore weight) to the electric machine. Thus, the top and / or bottom layers of coil 121 (i.e., the outer layers of the coil) do not extend axially further than the adjacent layers, thereby improving cooling at the axial ends of coil 121.

[0059] Depending on the degree to which a layer 131 is axially offset (117) relative to an adjacent layer 130, the axial ends of the layers 130, 131 may not touch or may not overlap. When the axial ends of the layers do not touch, an axial gap 118 is created. For example, an electric machine may have an axial gap 118 between a first axial end of a first layer 130 of coils and a first axial end of a second layer 130 of coils. The axial gap 118 may be understood herein as the distance between the most distal portion of the axial end of one layer and the most distal portion of the axial end of another layer (the axial ends being axial ends located on the same axial side of the coils).

[0060] Axial gap 118 further increases the surface area of ​​the axial end of the coil exposed to the cooling fluid, and thus, providing one or more axial gaps can further improve cooling of the axial end of the coil. Additionally, by combining axial gap 118 with other features, such as one or more cooling fluid guide structures 149 (see, e.g., FIGS. 10A and 10B), increased cooling fluid velocity can be utilized, and therefore, the surfaces of the axial end of the coil exposed to the cooling fluid can be better cooled.

[0061] In the example of Figure 5A, the first axial end of the first layer 130 and the first axial end of the second layer 131 are axially offset, but the ends of the layers still abut or at least overlap in the radial direction 144, thus eliminating an axial gap. In the example of Figure 5B, the first axial end of the first layer and the first axial end of the second layer are axially offset, and an axial gap 118 is also provided.

[0062] In some examples, the axial misalignment can be measured between the outer edge of the axial end of one layer and the outer edge of the axial end of an adjacent layer, as shown schematically in Figures 5A and 5B. Similarly, in some examples, the axial gap 118 can be measured between the outer edge of the axial end of one layer (the outer edge of the layer with the shorter axial extension at the centerline 109 of the coil; see Figure 4A) and the inner edge of the axial end of an adjacent layer (the inner edge of the layer with the longer axial extension at the centerline 109 of the coil) (see Figure 5B). The centerline 109 can be parallel to the radial direction 144 of the electric machine when the coil 121 is installed in the electric machine.

[0063] For the first axial end of the coil, the axial positions of the axial ends of the layers can vary along the height of the coil in any suitable manner. For example, the axial positions can alternate from the top layer to the bottom layer or from the bottom layer to the top layer (e.g., along the radial direction of the electric machine 144). In some of these examples, the first axial ends of the layers of the coil 121 can be axially offset, particularly along the height of the coil (i.e., in the radial direction of the electric machine). Cooling of the first end 123 of the coil 121 can be enhanced because every layer is axially offset relative to the adjacent layer, improving contact with the cooling fluid. Thus, for the first axial end 123 of the coil 121, the axial ends of the layers can form a wavy or triangular shape along the height of the coil. For example, the first ends of odd-numbered layers of the coil (e.g., layer numbers 1, 3, 5, etc., starting from the top or bottom layer) can extend further in the axial direction 142 than the first ends of even-numbered layers of the coil (e.g., layer numbers 2, 4, 6, etc.). In another example, the first ends of the odd layers of coils may extend axially no further than the first ends of the even layers of coils.

[0064] The even layers can extend axially the same amount; that is, all even layers can have the same half-length (measured relative to the centerline 109). In these or other examples, the odd layers can extend axially the same amount; that is, all odd layers can have the same half-length. An example of equal extension for both the even and odd layers is illustrated in Figures 5A and 5B. When the top layer 130 is layer number 1, the odd layers have a shorter axial extension than the even layers.

[0065] In some other examples, the coil 121 can include groups of layers; for example, the layers of the coil can be grouped in pairs, trios, etc., and the first axial ends of the groups can be axially offset in alternating directions between groups. An example of this configuration is shown schematically in FIG. 6. In this example, the layers of the coil are grouped in pairs. In some other examples, the groups of layers can have a different number of layers. For example, the coil can have layers grouped in pairs and layers grouped in trios.

[0066] At the first axial end of the coil, the axial position of the axial end of the layer can increase and then decrease in a direction parallel to the height of the coil (e.g., the radial direction 144 of the electric machine). For example, the half-length of the layer including the first end can increase along the radial direction from the top or bottom layer of the coil to a central region and then decrease from the central region toward the bottom or top layer of the coil. As previously discussed, the axial position of the axial end of the layer, or the half-length of the layer including the first end of the coil, can vary between adjacent layers in some embodiments and between groups of layers in some other embodiments.

[0067] Varying the end positions of the layers in this manner is beneficial for efficient cooling (e.g., more uniform cooling), particularly in a direction parallel to the height of the coil. If the cooling fluid cools the axial ends of the coil from the outside, the innermost layers of the coil may be less cooled. By extending the central layer axially 142 significantly at one or both axial ends of the coil, these central regions can be cooled more effectively. In this way, the risk of damage to the coil can be reduced.

[0068] Figure 7 shows a schematic enlarged view of another example of a central longitudinal section of a coil. In this example, the axial positions of the axial ends of the layers increase from the top of the coil toward the central region of the coil and then decrease toward the bottom of the coil. The layers are formed into groups, and the axial positions of the axial ends of the layers vary between groups of layers.

[0069] Although only a few particularly advantageous examples of axial offset of the layer ends have been described herein, it should be noted that the half-length of the layers and the axial gap 118 can generally be varied in any suitable manner along a direction parallel to the height of the coil 121.

[0070] If axial gaps 118 are provided at the axial ends of coils 121, one or more support inserts may be provided to stabilize the axial ends of the coils. Accordingly, electric machine 100 may further include a support insert disposed in axial gap 118 and at least partially (e.g., entirely) bridging axial gap 118. In some examples, the support insert may include a central body and two or more arms extending in opposite directions. For example, the shape and size of the support insert may be varied and adjusted depending on how the axial offset of the layer ends varies along the height of the coil.

[0071] Examples of support inserts 145 are shown in Figures 8A-8C and 9. In Figure 8A, the support insert 145 is located at the first end of the coil 123 (specifically, at the axial end of the coil). In Figure 8B, the support insert 145 is attached to the first end of the coil. Comparing Figures 8A and 8B, the support insert 145 is rotated. In Figure 8B, the arms of the support insert 145 extend axially. The arms fill the space between adjacent layers. The attached support insert 145 can also be seen in Figure 9.

[0072] In some embodiments, the support insert 145 can be directly or indirectly connected to the axial protrusion 147 of the corresponding tooth 119 of the coil 121. The end of the coil of the support insert 145 can be coupled to the axial protrusion 147, for example, with a suitable rope or tape 146 (e.g., prepeg tape). In some embodiments, the tape 146 can be wrapped around the end of the coil and the axial protrusion 147 connected to the corresponding tooth 119 (see FIGS. 8C and 9).

[0073] The axial protrusion 147 can be disposed between the tooth 119 and the end of the coil 123. The axial protrusion 147 can include a through hole for the tape 146 to pass through (e.g., extend radially). The axial protrusion 147 can be non-magnetic. The axial protrusion 147 can be attached to an axial portion of the tooth 119. By coupling (e.g., axially coupling) the end of the coil 121 to the axial protrusion 147, the end of the coil can be properly positioned relative to the tooth 119.

[0074] The electric machine 100 may further include one or more guide structures for directing the cooling fluid toward the axial ends of the coils. The guide structures (e.g., scoops) may be located in an axial region of the electric machine closer to an outlet for removing the cooling fluid than to an inlet for introducing the cooling fluid into the electric machine. For example, if the cooling fluid flows axially between the coils, the guide structures may be located in an axial region closer to the output axial ends of the coils.

[0075] In some embodiments, the coil 121 can include one or more cooling fluid guide structures. For example, two guide structures (e.g., scoops 149) can be positioned at the first axial end 123 of the coil 121 and / or two guide structures 149 can be positioned at the second axial end 125 of the coil 121 (see FIG. 10A ). The guide structures can be attached to the ends of the layers that protrude axially outward, for example, with an adhesive. The guide structures (e.g., scoops) can be curved to match the curvature of the axial ends of the coil. The guide structures 149 can have, for example, a shape similar to an integral sign (∫). The one or more guide structures can be used to guide the cooling fluid, for example, to increase the area where the cooling fluid comes into contact with the ends of the coil 121 (see the arrows in FIG. 10A ). The guide structures can be non-metallic.

[0076] In another example, the electric machine 100 may include one or more guide structures 149 on an inner wall (e.g., an axial wall) facing the axial ends 123, 125 of the coils 121. For example, one or more scoops 149 may be disposed on a stator wall facing the first (or second) axial end of the coils 121 (see FIG. 10B). Any suitable guide structure may be used. For example, at least when the scoop is disposed on an inner wall of the electric machine, the scoop may be a static scoop or a dynamic scoop (e.g., a rotating scoop).

[0077] In some embodiments, one or more fans may be provided in addition to or as an alternative to one or more guide structures (such as scoops) provided on the interior wall, and may be positioned to blow air toward, for example, the first axial end of the coil.

[0078] The features of this embodiment are primarily described with respect to one (e.g., first) axial end of coil 121. It should be understood that the features and descriptions also apply to the other axial end of the coil. That is, the descriptions and discussion with respect to Figures 3-9 apply to both axial ends 123, 125 of the coil. In this regard, the first axial end of coil 123 may include an axial offset (117) between layers 130, 131, the second axial end of coil 125 may include an axial offset (117) between layers 130, 131, or both the first and second axial ends may include axially offset layers.

[0079] For example, the second axial end of the first layer 130 of the coil 121 is axially offset relative to the second axial end of the second layer 131 of the coil 121 (e.g., FIGS. 4A and 4B). When the two axial ends of the coil 121 comprise axially offset layers, the offset of the first axial end 123 and the offset of the second axial end 125 can be equal (e.g., symmetrical). In other examples, the first axial end and the second axial end of the coil can be different.

[0080] In a further aspect of the present disclosure, a wind turbine 10 is provided. The wind turbine includes an electric machine 100 of the above-described aspect. The electric machine 100 may be a generator 42. The wind turbine may be an onshore wind turbine or an offshore wind turbine, for example, a direct drive wind turbine. In some examples, the generator 42 includes a rotor and a stator, and the stator may include a coil 121. The rotor may include, for example, a permanent magnet.

[0081] In another aspect of the present disclosure, a method 200 of insulating a coil is provided. A flowchart of the method is shown in FIG. 11. The method includes, at block 210, bending conductive strands to form layers of the coil such that a first axial end of a first layer 130 of the coil is offset longitudinally of the coil relative to a first axial end of a second layer 131 of the coil. The method further includes, at block 220, electrically insulating the first axial ends of the first layer 130 and the second layer 131.

[0082] The electrical insulation step can be performed in several ways. In some examples, the electrical insulation step 220 can include attaching preformed insulating elements to the first axial end of the first layer 130 and the first axial end of the second layer 131. This can be performed after the coil is formed or while the coil is being formed. For example, after forming the first layer 130, a preformed insulating element can be attached, e.g., with an adhesive, to the first axial end of the first layer 130 but before forming the second layer 131. Then, after forming the second layer 131, another preformed insulating element can be attached, e.g., with an adhesive, to the first axial end of the second layer 131. Examples of preformed insulating elements 148 are shown in FIGS. 12A and 12B. In some examples, the preformed insulating elements 148 can be clipped onto the axial ends of the layers.

[0083] Once the preformed insulating elements 148 are attached to the corresponding axial ends of the coil, the ends of the coil or the entire coil can be poured, dipped, brushed, or sprayed. For example, vacuum pressure impregnation (VPI) can be used. Alternatively, other impregnation methods (e.g., immersion impregnation, dip impregnation, vacuum impregnation) can be used.

[0084] In some cases, the pre-formed insulating element 148 can be attached to already existing electrical insulation. For example, if the strands are wrapped with tape, the pre-formed insulating element 148 can be placed on top of the already existing insulation before bending the strands to form the different layers of the coil 121.

[0085] When one or more cooling fluid guide structures (e.g., scoops) are attached to the axial ends of the coil 121, the guide structures can be attached to the preformed insulating element. For example, the preformed insulating element 148 of FIG. 12A can include scoops (e.g., two scoops), which can be attached to the axial ends of the corresponding layers of the coil before or after attaching the preformed insulating element.

[0086] In some other examples, the electrical insulating step 220 can include wrapping the conductive strands with tape before bending the conductive strands. In particular, the conductive strands can be wrapped with tape after bending the strands so that the insulation at the first axial ends of the first and second layers 130, 131 is thicker than the insulation at the center of the first and second layers 130, 131. For example, the center of the coil can be wrapped with more electrical insulation, such as to provide additional protection for the coil after formation, so thickening the insulation at the axial ends of the layers while the coil is being formed can better protect the axial ends of the coil if the ends are axially misaligned.

[0087] The electrical insulation requirements may be different at the axially offset ends of a layer than at the center of that layer. Therefore, the conductive strands may be wrapped with more tape at the axial ends after bending the conductive strands. An example of thicker insulation in these areas is shown in the example of Figure 13.

[0088] In this example, conductive strands 150, specifically three strands (e.g., copper strands), are wrapped with tape 151 before being bent. The strands 150 have more tape 151 wrapped around them in areas that will become the axial ends of the coil 121. This can be achieved in a variety of ways. For example, the feed rate of the tape 151 can be slowed down to wrap the tape around areas that will become the axial ends of the coil layers (or the feed rate can be increased to wrap the tape around areas that will become the center of the coil layers). Alternatively, or in addition, the feed rate of the strands 150 can be slowed down to wrap the tape around areas that will become the axial ends of the coil layers (or the feed rate of the strands 150 can be increased to wrap the tape around areas that will become the center of the coil layers).

[0089] The feed rate of the tape 151 and / or strand 150 can be adjusted depending on the final shape and size desired for each layer of the coil 121. The axial ends, or the entire coil, may be impregnated or dipped, for example, using a VPI.

[0090] According to another aspect of the present disclosure, a generator 42 for a wind turbine 10 (optionally a direct drive wind turbine) is provided. The generator includes a rotor, a stator, and a radial air gap separating the rotor and stator. The stator includes a plurality of teeth 119 and a plurality of coils 121 wound in layers around the teeth 119. The coils 121 include a first layer 130, with the first layer 130 having an axial end that is axially offset relative to an axial end of a second layer 131 adjacent to the first layer 130. The axial ends of the first layer 130 and the second layer 131 reside in the same axial region 123 of the coils 121.

[0091] An axial gap 118 may be provided separating the axial ends of the first layer 130 and the second layer 131 .

[0092] The generator may further include inserts 145 bridging the axial gap to stabilize the ends of the coils 121. Vibrations at the ends may be avoided or at least reduced.

[0093] The generator may further include one or more guide structures (e.g., scoops) attached to the axial ends of the second layer to increase contact between the cooling fluid and the axial ends, and the axial ends of the second layer may protrude axially beyond the first layer.

[0094] The electrical insulation 151 at the axial ends of the first layer 130 and the second layer 131 may be thicker than the electrical insulation in the middle portions of the first layer 130 and the second layer 131 .

[0095] The ends of the layers in the same axial region or at the same end of the coil 121 may alternately protrude axially.

[0096] The extension of the ends of the layers in the same axial region of the coil can increase from the top layer to the middle layer and then decrease towards the bottom layer.

[0097] For example, the features and descriptions of the above embodiment with respect to Figures 1-13 may be applied to and combined with this embodiment, and vice versa.

[0098] The present specification uses examples to disclose the present invention (including preferred embodiments), and enables one of ordinary skill in the art to practice the present invention (e.g., to manufacture and use devices or systems, and to practice methods incorporating the same). The patentable scope of the invention is defined by the claims, and may include other examples that occur to those skilled 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 claim language, or if they include equivalent structural elements that do not differ substantially from the claim language. Aspects of the various described embodiments, and other known equivalents to such aspects, can be combined and assembled by those skilled in the art to construct additional embodiments and techniques in accordance with the principles of the present application. If reference signs relating to the drawings are placed in parentheses in the claims, the reference signs are merely for the purpose of facilitating understanding of the claims and should not be construed as limiting the scope of the claims. [Explanation of symbols]

[0099] 10. Wind Turbines 12 Ground 14 Support System 15 Tower 16 Nacelle 18 rotors 20 Hub 22 rotor blades 24 Root 26 Load Transfer Area 28 Wind direction 30 rotor shaft 32 Pitch System 34 Pitch axis 36 Wind Turbine Controller 38 axes 40 processors 42 Generator 46 Gearbox 48 High Speed ​​Shaft 50 Coupling 54 Decoupling support means 58 Weather Measurement System 60 Front support bearing 62 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 Generator 86 Cavity 88 Inner 90 Transformer 103 Torque arm 110 rotor 113 Electrical Connections 115 coil 116 Air Gap 117 Shift 119 teeth 120 Stator 124 Central part 146 Tape 147 Axial protrusion 148 Insulating Elements 200 ways

Claims

1. An electric machine (100) comprising: a rotor (110), and Stator (120) Including, At least one of the rotor (110) and the stator (120) includes a plurality of teeth (119) and a plurality of coils (121), the coils (121) including one or more strands (150) wound in layers (130, 131) around the teeth (119); The coil (121) includes a first axial end (123), a central portion (124), and a second axial end (125) opposite the first axial end (123); The layers (130, 131) of the coil (121) include a first axial end, a central portion, and a second axial end opposite the first axial end, a first axial end of a first layer (130) of at least one coil of the plurality of coils (121) being axially offset (117) relative to a first axial end of a second layer (131) of the coils (121).

2. 2. The electric machine of claim 1, wherein a first axial end (123) of the coil (121) is farther from an inlet portion of the electric machine (100) configured to receive a cooling fluid for cooling the coil (121) than a second axial end (125) of the coil (121).

3. 3. The electric machine of claim 1 or 2, wherein the first layer (130) and the second layer (131) are adjacent layers.

4. 4. The electric machine of claim 3, wherein the first layer (130) is an outer layer of the coil (121), and a first axial end of the first layer (130) does not extend further in the axial direction (142) than a first axial end of the second layer (131).

5. 5. The electric machine of claim 3, further comprising an axial gap (118) between a first axial end of the first layer (130) of the coils (121) and a first axial end of the second layer (131) of the coils (121).

6. The electric machine of claim 5 , further comprising a support insert (145) disposed in the axial gap (118) and at least partially bridging the axial gap (118).

7. 7. The electric machine of claim 6, wherein the support insert (145) is directly or indirectly connected to an axial protrusion (147) of a corresponding tooth (119) of the coil (121).

8. 8. The electric machine of claim 7, wherein a first axial end (123) of the coil (121) including the support insert (145) is coupled (146) to the axial protrusion (147).

9. 9. The electric machine of claim 1, wherein at a first axial end (123) of the coil (121), the axial positions of the axial ends of the layers (130, 131) alternate from the top layer to the bottom layer.

10. 9. The electric machine of claim 1, wherein at a first axial end (123) of the coil (121), the axial positions of the axial ends of the layers (130, 131) increase from the top layer towards a central region and decrease from the central region towards the bottom layer.

11. The electric machine of any one of claims 1 to 10, further comprising one or more guide structures (149) for directing cooling fluid towards the first ends (123) of the coils (121).

12. A method (200) for insulating a coil (121), comprising: Bending (210) the conductive strands (150) to form layers (130, 131) of a coil (121), wherein a first axial end of a first layer (130) of the coil (121) is offset (117) in the longitudinal direction of the coil (121) relative to a first axial end of a second layer (131) of the coil (121); and electrically insulating (220) first axial ends of the first layer (130) and the second layer (131); A method (200) comprising:

13. The method of claim 12, wherein the electrically insulating step (220) comprises attaching a preformed insulating element (148) to a first axial end of the first layer (130) and a first axial end of the second layer (130).

14. 13. The method of claim 12, wherein the electrically insulating step (220) comprises wrapping the conductive strands (150) with tape (151) before bending the conductive strands (150).

15. 15. The method of claim 14, wherein after bending the conductive strands, the conductive strands are wrapped with tape such that the electrical insulation at first axial ends of the first layer and the second layer is thicker than at central portions of the first layer and the second layer.

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