Cooling of Electrical Machinery

Abstract

To provide an electrical machine.SOLUTION: The electrical machine comprises a rotor 20, a stator 30, and an air gap 40 arranged between the rotor 20 and the stator 30. The stator 30 or rotor 20 comprises a plurality of electrical coils 90, where one or more of the electrical coils 90 carry a heat sink, where the heat sink is attached to the electrical coil with a thermally conductive material. Methods for modifying a temperature distribution of a stator in an electrical machine are also provided.SELECTED DRAWING: Figure 3

Description

Technical Field

[0001] The present disclosure relates to an electromechanical machine, and more particularly, to an apparatus, system, and method for cooling an electromechanical machine. The present disclosure also relates to a wind turbine comprising such an electromechanical machine, and more particularly, to a wind turbine comprising a permanent magnet generator having a cooling arrangement.

Background Art

[0002] Electromechanical machines such as motors and generators generally comprise a rotor structure and a stator structure. Large generators may be permanent magnet excited generators (PMGs) or electrically excited synchronous generators (EESGs).

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

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

[0005] In permanent magnet-excited generators (PMGs), the permanent magnets (PMs) are generally located in the rotor (although they can also be arranged alternately in the stator structure), while the winding elements (e.g., coils) are usually contained within the stator (although they can also be arranged alternately in the rotor structure). Permanent magnet generators are generally considered reliable and require less maintenance than other types of generators.

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

[0007] An electrically excited synchronous generator generally comprises a rotor having multiple pole pieces and excitation coils. During operation, current is applied to the excitation coils, generating polarity in the magnetic poles. Adjacent poles have different magnetic polarities. As the rotor rotates, magnetic fields from the pole pieces are applied to the stator windings, creating a variable magnetic flux in the stator windings and generating a voltage in the stator windings. In an electrically excited synchronous generator, the magnetic field for generating power is electrically generated. As a result, such generators do not require the use of permanent magnets containing rare earth elements.

[0008] Because active elements (magnets or coils) generate heat during use, cooling is generally important in electromechanical systems. Excessively high temperatures can lead to failure of these elements and reduced operational efficiency.

[0009] Different configurations of electromechanics are known, such as radial machines and axial machines. In axial machines, the rotor and stator face each other axially. An air gap is positioned axially between the rotor and stator. In radial machines, a substantially annular air gap may be formed between the rotor and stator. One of the rotor and stator is positioned to radially surround the other. The motion of the rotor causes air in the air gap to move around it. This provides a cooling effect to the air.

[0010] An active air cooling system or air conditioning system is known to provide a low-temperature airflow through an internal stator structure. The cooling airflow is then distributed along the circumference of the stator. The airflow then cools the active elements of the rotor and stator by axially crossing the air gap from one side to the other. Hot air is then collected on the opposite axial side. The hot air can then be exhausted or cooled in a heat exchanger and reused.

[0011] When cooling air travels axially across an air gap from one side to the other, the air is heated as it passes through the gap. Therefore, the cooling air is cooler on one side than on the other, and thus one side is cooled more effectively than the other. As a result, the cooling of the active element is not uniform; that is, one side of an electromechanical coil may always have a higher temperature than the other side of the same coil. Of course, this effect is not limited to a single coil, nor is it limited to multiple coils. Rather, this effect can generally be observed for active elements arranged along an air gap.

[0012] Non-uniform temperature distribution affects the operation of electromechanical machinery. The maximum temperature of an electromechanical machine is generally required to remain below a certain threshold. Meeting this maximum temperature requirement may require increasing the cooling airflow or limiting the maximum power of the electromechanical machine. If the temperature distribution can be made more uniform for a given electromechanical machine, the requirements for the air cooling system may be lower, or the nominal power may be increased.

[0013] The sizes and types of electromechanics and potential problems described herein are not limited to generators for direct-drive applications, nor are they limited to the field of wind turbines. Electromechanics of considerable size that may suffer the same problems and / or have the same complexity may also be found, for example, in steam turbines and hydraulic turbines.

[0014] This disclosure provides examples of systems and methods that address at least partially some of the aforementioned shortcomings. [Overview of the project]

[0015] In a first embodiment, an electromachine is provided comprising a rotor, a stator, and an air gap disposed between the rotor and the stator. The stator and / or rotor comprises a plurality of electric coils, one or more of the electric coils carrying a heat sink that dissipates heat from the electric coils to the air gap. The heat sink is attached to the electric coils having a thermally conductive material.

[0016] According to this embodiment, the cooling of the electric coil can be influenced and controlled. The heat sink may be attached to the surface of the coil, thereby influencing the airflow around the coil. Since electric coils are typically made from highly thermally conductive materials such as copper, this can affect the temperature distribution of the coil along its entire length, not just where the heat sink is attached.

[0017] In this example, this allows for a more uniform temperature distribution across the entire coil. By avoiding hot spots, the efficiency of the electromechanical unit can be improved.

[0018] The heat sinks used throughout this disclosure can be understood as any structure that acts as a passive heat exchanger, transferring heat from an electrical coil to the air in an air gap.

[0019] In a further aspect, a method for modifying the temperature distribution of a stator in an electric machine is provided. The method includes operating the electric machine and measuring the temperature distribution of the stator during operation. The method further includes attaching a heat sink to a selected area of the surface of one or more electrical coils of the stator to increase the contact surface with the air flow around the electrical coils.

[0020] Non-limiting examples of the present disclosure are described below with reference to the accompanying drawings.

Brief Description of the Drawings

[0021] [Figure 1] A perspective view of a wind turbine according to an example. [Figure 2] A detailed internal view of the nacelle of a wind turbine according to an example. [Figure 3] A diagram schematically representing a cross-sectional view of an example of an electric machine. [Figure 4] A diagram schematically showing the temperature distribution along the length of a coil in an electric machine. [Figure 5] A diagram schematically showing the coils of a stator of an electric machine having a plurality of heat sinks according to an example. [Figure 6] A diagram schematically showing another example of an electrical coil having a heat sink.

Modes for Carrying Out the Invention

[0022] In these figures, the same reference numerals are used to indicate corresponding elements.

[0023] FIG. 1 shows a perspective view of an example of a wind turbine 160. As shown, the wind turbine 160 includes a tower 170 extending from a support surface 150, a nacelle 161 mounted on the tower 170, and a rotor 115 coupled to the nacelle 161. The rotor 115 includes a rotatable hub 110 and at least one rotor blade 120 coupled to the hub 110 and extending outwardly from the hub 110. For example, in the illustrated embodiment, the rotor 115 includes three rotor blades 120. However, in alternative embodiments, the rotor 115 may include more or fewer than three rotor blades 120. Each rotor blade 120 may be spaced about the hub 110 to facilitate rotation of the rotor 115 and to enable conversion of kinetic energy from the wind into mechanical energy that can be used and subsequently into electrical energy. For example, the hub 110 may be rotatably coupled to a generator 162 (FIG. 2) positioned within the nacelle 161 to enable generation of electrical energy.

[0024] FIG. 2 shows a simplified internal view of an example of the nacelle 161 of the wind turbine 160 of FIG. 1. As shown, the generator 162 may be disposed within the nacelle 161. Generally, the generator 162 may be coupled to the rotor 115 of the wind turbine 160 to generate electrical power from the rotational energy generated by the rotor 115. For example, the rotor 115 can include a main rotor shaft 163 coupled to the hub 110 for rotation therewith. Next, the generator 162 may be coupled to the rotor shaft 163 such that rotation of the rotor shaft 163 drives the generator 162. For example, in the illustrated embodiment, the generator 162 includes a generator shaft 166 rotatably coupled to the rotor shaft 163 via a gearbox 164.

[0025] It should be understood that the rotor shaft 163, the gearbox 164, and the generator 162 may generally be supported within the nacelle 161 by a support frame or bedplate 165 positioned at the top of the wind turbine tower 170.

[0026] The nacelle 161 is rotatably coupled to the tower 170 by a yaw system 20 so that the nacelle 161 can rotate around the yaw axis YA. The yaw system 20 comprises a yaw bearing having two bearing components configured to rotate relative to the other. The tower 170 is coupled to one of the bearing components, and the bed plate or support frame 165 of the nacelle 161 is coupled to the other bearing component. The yaw system 20 comprises an annular gear 21, a plurality of yaw drive units 22 having motors 23, a gearbox 24, and a pinion 25 for meshing with the annular gear 21 to rotate one of the bearing components relative to the other.

[0027] The blade 120 is coupled to the hub 110 via a pitch bearing 100 between the blade 120 and the hub 110. The pitch bearing 100 comprises an inner ring and an outer ring. The wind turbine blade can be mounted on either the inner bearing ring or the outer bearing ring, and the hub is connected to the other. When the pitch system 107 is actuated, the blade 120 can perform rotational motion relative to the hub 110. Thus, the inner bearing ring can perform rotational motion relative to the outer bearing ring. The pitch system 107 in Figure 2 comprises a pinion 108 that meshes with an annular gear 109 provided on the inner bearing ring to rotate the wind turbine blade around the pitch axis PA.

[0028] The energy generated by the generator can be delivered to a converter that adapts the generator's output power to the requirements of the power grid. The electromechanical unit may have electrical phases, for example, three electrical phases. The converter may be located inside the nacelle, inside the tower, or outside.

[0029] Figure 3 schematically shows a generator, specifically a direct-drive wind turbine generator.

[0030] The generator 10 in Figure 3 comprises a rotor 20 extending from a first side surface 101 to a second side surface 102 and configured to rotate around a rotation axis 33, a stator 30, and an air gap 40 between the rotor 20 and the stator 30.

[0031] The stator 30 in this figure comprises a stator structure 50 having a plurality of electric coils 90 and a circumferential support 60 that supports the plurality of electric coils 90. The stator structure 50 extends from a first side 31 to a second side 32 along the rotation axis 33 of the generator.

[0032] The generator 10 in Figure 3 further comprises an air cooling system 110 for cooling a plurality of electric coils 90. In this example, the air cooling system 110 includes an electromechanical air inlet 111, an air distribution channel 72 extending through a portion of the circumferential support 60, and an electromechanical air outlet 112 in fluid communication with the air gap 40. The electromechanical air inlet can allow airflow to enter the electromechanical device.

[0033] The cooling air delivered by the air cooling system 110 can provide low-temperature air to the air gap 40. This air can then cool electromagnetic elements positioned along the air gap, such as the rotor and magnets or coils positioned with the electric coils 90 located in the stator.

[0034] In this example, the air distribution channel 72 is in fluid communication with the electromechanical air inlet 111 and includes an air entrance 71 located on a first side surface 31 of the circumferential support 60. The air distribution channel further includes a plurality of axial air openings 73 located on a second side surface 32 of the circumferential support 60, which are in fluid communication with the air gap 40, in order to distribute the airflow from the electromechanical air inlet 111 along the air gap 40.

[0035] In the generator 10 shown in this figure, the rotor 20 surrounds the stator 30. The rotor is rotatably mounted to the support frame 9 of the wind turbine via generator bearings 11. The rotor 20 can be connected to the rotor hub of the wind turbine (not shown in this figure) to rotate the rotor hub. The stator 30 can be firmly connected to the support frame 9 of the wind turbine. The electric windings 90 are located outside the outer rim of the circumferential support, and the magnet module 21 may be located inside the outer rotor rim 22.

[0036] In this example, the generator includes a cover plate 12 located on the first side surface 101. The cover plate 12 can close the generator and may be fixedly mounted to the support frame 9 of the wind turbine. A sealing member may be located between the portion of the rotary rim 22 closest to the first side surface 101 and the cover plate 12.

[0037] In other examples, the cover plate 12 may form part of the rotor 20. In some of these examples, additional generator bearings can rotatably connect the cover plate to the support frame of the wind turbine.

[0038] A low-temperature airflow can enter the generator 10 through the electromechanical air inlet 111. This low-temperature airflow can be guided through the stator structure 50 and a plurality of axial air openings 73 toward the air gap 40 of the generator 10. Thus, the airflow can be distributed substantially uniformly along the circumference of the air gap 40. Thus, this low-temperature airflow can cool the electromagnetic components of the rotor and stator located in the air gap 40. The airflow can pass axially through the air gap from the second side 102 to the first side 101 in order to cool the electromagnetic components located in the air gap. Heat from the electromagnetic components is transferred to the airflow, and the temperature of the airflow at the first side 101 may be higher than that of the airflow at the second side 102. This high-temperature airflow can then exit the generator through the electromechanical air outlet 112 and be cooled in a heat exchanger. The electromechanical air outlet can allow the airflow to exit the electromechanical.

[0039] Therefore, electromagnetic components placed in the air gap, such as electric coils, can operate within a predetermined temperature range, and thus the electromechanism can operate efficiently. Since the stator structure is used to distribute airflow along the circumference of the stator, fewer air entrances are required. Therefore, the integration constraints of, for example, attaching a generator to a direct-drive wind turbine can be minimized.

[0040] The air cooling system shown in this figure includes a second lateral radial air channel 114 extending radially between the second side surface 32 of the circumferential support 60 and the second side surface 102 of the rotor 20. The second lateral radial air channel 114 can connect a plurality of axial air openings 73 to the air gap 40.

[0041] The air cooling system may include a first lateral radial air channel 113 extending radially between the first side surface 31 of the circumferential support 60 and the first side surface 101 of the rotor 20. The first lateral radial air channel 113 can connect the air gap 40 to the electromechanical air outlet 112.

[0042] In some examples, the cooling system may include a heat exchanger. The heat exchanger may comprise a first fluid circuit and a second fluid circuit. The first fluid circuit may be connected to the cooling system to cool an electromechanical device. The second fluid circuit may cool a fluid flowing along the first fluid circuit. The fluid in the second fluid circuit may be, for example, air or water. The first fluid circuit may include a heat exchanger air inlet connected to an electromechanical air outlet to receive a warm airflow from an air gap. In addition, the first fluid circuit may include a heat exchanger air outlet connected to an electromechanical air inlet to deliver an airflow to the air gap. A conduit may be placed between the electromechanical air outlet and the heat exchanger air inlet to guide the airflow toward the heat exchanger. The conduit may connect the heat exchanger air outlet to the electromechanical air inlet.

[0043] The airflow from the air gap can be cooled by a second fluid circuit, and this cooled airflow can be introduced into the electromechanical machine through an electromechanical air inlet to cool the electromagnetic components located in the air gap.

[0044] As mentioned above, the low-temperature airflow can therefore cool the electromagnetic components of the rotor and stator located in the air gap 40. The airflow can pass axially through the air gap from the second side 102 to the first side 101 in order to cool the electromagnetic components located in the air gap. Heat from the electromagnetic components is transferred to the airflow, and the temperature of the airflow at the first side 101 may be higher than that of the airflow at the second side 102. (Cooling) Since the temperature of the airflow may be higher at the first side 101, the cooling of the coils on this side of the electromachine is performed with warmer air. Therefore, the cooling may be less effective locally.

[0045] An example of the temperature distribution obtained along the axial length of the coil can be seen in Figure 4. On the first side surface 101, the coil has a significantly higher temperature than on the second side surface 102, i.e., the side where the cooling airflow approaches the air gap.

[0046] Such localized hotspots can be a limiting factor in the design of electromechanical systems. One way to reduce hotspots is to provide colder cooling air or a higher mass flow rate of cooling air. However, these measures require an overall increase in pump power or blow-off power.

[0047] Regarding Figures 5 and 6, several systems and methods are shown for reducing the temperature within an electrical coil and distributing heat differently, and especially more uniformly, along the coil. While the problem of non-uniform temperature distribution was shown in electromachines with a radial air gap, the following also applies to axial air gaps. Furthermore, although Figure 3 shows the rotor surrounding the stator radially, the same or similar systems and methods can be applied when the stator surrounds the rotor radially.

[0048] In one embodiment, the electromachine 10 comprises a rotor 20, a stator 30, and an air gap 40 disposed between the rotor 20 and the stator 30, the stator 30 comprising a plurality of electric coils 90. One or more of the electric coils 90 support heat sinks 82, 84, and the heat sinks 82, 84 are attached to the electric coils 90 having a thermally conductive material.

[0049] The electromachine may be a permanent magnet generator. The rotor of the permanent magnet generator carries multiple magnets, which may be in the form of permanent magnet modules. The rotor may be arranged to radially surround the stator. A wind turbine may be equipped with an electromachine, i.e., in this case, a permanent magnet generator. The permanent magnet generator may be directly driven.

[0050] In some examples, as shown in the example in Figure 5, the heat sinks 82, 84 may have multiple fins. The fins can be considered herein as ribs protruding outward. The fins may have a constant or varying spacing from one another. The design of the fins, and their spacing, may be optimized to provide an optimized cooling airflow. The (cooling) air in the air gap can cool the fins.

[0051] A heatsink may be designed to maximize its surface area in contact with the surrounding air. Air velocity, material selection, protrusion design, and surface treatment are factors that affect the performance of a heatsink.

[0052] The fins may be attached to the electrical coil via a thermally conductive adhesive or resin, or double-sided tape. When the fins are cooled, the electrical coil can be locally cooled. The resin or adhesive may be an electrically insulating material. Alternatively, the fins may be made of a non-conductive material.

[0053] In some examples, the glue may be an epoxy resin containing metal, metal oxide, silica, or ceramic microspheres. For example, epoxy containing aluminum nitride or boron nitride fillers may be used. These materials may have high thermal conductivity and electrical insulation properties.

[0054] Electrical coils are generally made from highly thermally conductive materials such as copper, so if the temperature inside the coil drops locally, heat conduction will affect the heat distribution throughout the rest of the coil.

[0055] In some cases, the heatsink may be made of a substantially non-magnetic material. By using a non-magnetic material, the electromagnetic field generated between the rotor and stator cannot be affected by the placement of the heatsink. A suitable material for the heatsink / fin may be aluminum.

[0056] In some examples, as shown in Figures 5 and 6, for example, the electric coil may be arranged around the stator teeth 96, and the coil 90 has a substantially oval shape having a first straight side surface 93, a second straight side surface 94 parallel to the first straight side surface 93, a first curved portion 91 connecting the first straight side surface 93 to the second straight side surface 94 at a first end 101, and a second curved portion 92 connecting the first straight side surface 93 to the second straight side surface 94 at a second end 102.

[0057] The stator teeth 96 may form a pole core around which an electric coil is arranged and may include pole pieces. The stator teeth 96 may be attached to the stator rim at a base 98.

[0058] In the example in Figure 6, the heat sinks 82 and 84 are attached to the first curved portion 91. In this example, as in the examples in Figures 3 and 4, the second end 102 is closer to the cooling air supply than the first end 101.

[0059] In some examples, the heatsink 82 may be mounted on the outside of the winding. In the example in Figure 5, the coil defines an outer diameter and an inner diameter at both ends of the coil 90. The heatsink 82 is mounted along the outer diameter of the coil. In some examples, depending on the available space between the pole core (stator teeth 96) and the coil 90, the heatsink 84 may be mounted on the inside of the winding, i.e., along the inner diameter of the coil.

[0060] In some examples, as shown in Figures 5 and 6, the heat sink may be mounted both inside and outside the winding.

[0061] In some examples, one or more electrical coils are fitted with multiple heat sinks. In some electromachines, it can be assumed that the cooling airflow is distributed substantially uniformly along the circumference (i.e., along the radial air gap). In other electromachines, the cooling airflow is not actually distributed uniformly. Such non-uniform cooling air distribution along the circumference can be compensated for by placing heat sinks only on selected coils, or for different sizes and numbers of heat sinks between various coils.

[0062] As mentioned above, if cooling air is supplied at the second end, a higher temperature can be expected at the first end. This does not mean that the heatsink is suitable or useful only at the second end.

[0063] In the example shown in Figure 6, the first heatsink 82 is attached to the inside of the first curved portion 91 at the first end 101, and the second heatsink 84 is attached to the outside of the first curved portion 91. Alternatively, a third heatsink may be attached to the second curved portion 92. The third heatsink 87 may be attached to the outside of the electrical coil at the second end 102. The fourth heatsink 89 may be attached to the inside of the electrical coil at the second end 102.

[0064] In some examples, as shown in Figure 6, the heatsink 86 is attached to one of the first and second straight sides 93, 94, or to both of the first and second straight sides. In this example, the heatsink along the straight side may be substantially linear fins. The arrangement of the heatsink along the straight side can be adjusted according to the specific needs of the electromechanical device in order to generally lower the average temperature of the stator coil and / or to make the temperature distribution more uniform.

[0065] In the example shown in Figure 6, the heatsink may extend along the entire height of the electrical coil. In other examples, the heatsink may extend only along a portion of the height of the electrical coil.

[0066] In a further embodiment, a method is provided for correcting the temperature distribution of a stator 30 in an electromachine. The method includes operating the electromachine and measuring the temperature distribution of the electric coils 90 of the stator 30 during operation. The method further includes attaching heat sinks 82, 84, 87, 89, 86 to selected areas of the surface of one or more electric coils of the stator (or rotor, if the rotor has coils) to increase the contact surface with the airflow around the electric coils.

[0067] The electromechanical device here may be a generator or a motor. Even if simulations are performed before the design and operation of the electromechanical device, the actual temperature distribution may differ from what is expected. If a problematic temperature distribution is detected, for example, if the average temperature may be higher than expected, or if localized hot spots may occur, providing a heatsink can be a relatively easy way to solve these problems. One or more heatsinks can be retrofitted to an existing electromechanical device.

[0068] In one example, before the heatsink is installed, the temperature difference between the minimum and maximum temperatures of the electrical coil may be, for example, 30°C, 40°C, or 50°C or more. The heatsink may be installed in a selected area, particularly in the hotter area of ​​the electrical coil. The selection of an appropriate area of ​​the coil may take into account the temperature distribution during operation as well as the availability of space on and around the coil. In some examples, after the heatsink is installed, the maximum temperature difference may be, for example, 20°C or less.

[0069] In particular, for large electrical machinery such as direct-drive wind turbine generators, retrofitting localized heat sinks may be beneficial compared to alternative solutions such as increasing airflow mass.

[0070] In some cases, the temperature distribution of the stator coil during operation may be more uniform after a heatsink is installed. In further cases, the average overall temperature may be reduced after installing one or more heatsinks. In other cases, the average temperature may be lower, and the overall heat distribution may be more uniform.

[0071] In some examples, operating an electromachine may involve providing a cooling airflow through an air gap located between the rotor and stator. In some electromachines, a dedicated air cooling system may be provided. In other electromachines in which the apparatus and systems disclosed herein can be used, a dedicated air cooling system does not exist. Instead, cooling is generally provided by the movement of air through the air gap.

[0072] Further embodiments of the present disclosure provide an electromachine comprising a stator having a plurality of electric coils, a rotor, and a radially positioned air gap between the stator and the rotor. The electromachine further comprises a cooling system configured to provide a cooling airflow from a first side of the air gap to a second side of the air gap. In this specification, one or more passive heat exchangers are attached to the electric coils, configured to modify the cooling airflow and / or to increase the contact surface with the airflow.

[0073] As mentioned above, modifying the cooling airflow and increasing the contact between the coil being cooled and the cooling airflow can affect the average temperature and temperature distribution of the coil.

[0074] A passive heat exchanger may have multiple fins. In the example, these passive heat exchangers or "heat sinks" may include structures that generate turbulence or vortices to optimize contact between the (cooling) airflow and the heat sink.

[0075] In some examples, the electric coil may be positioned around the stator teeth, and the coil has a substantially oval shape having a first straight side surface, a second straight side surface parallel to the first side surface, a first curved portion connecting the first straight side surface to the second straight side surface at the first end, and a second curved portion connecting the first straight side surface to the second straight side surface at the second end. Fins may be attached to one or both of the first and second curved portions. Structures that increase the contact area may also be attached along the straight side surface, but generally there is more available space at the curved ends of the coil.

[0076] In the illustrated example, the passive heat exchanger of the heatsink is shown mounted on the surface of the coil on the stator, but it can be similarly applied to the coil on the rotor.

[0077] This specification discloses the present invention, including preferred embodiments, using examples, and enables those skilled in the art to practice the invention, including by constructing and using any device or system and by carrying out any incorporated method. The patentable scope of the present invention is defined by the claims and may include other embodiments that a person skilled in the art may conceive. Such other embodiments are intended to be within the claims if they have structural elements that do not differ from the language of the claims, or if they include equivalent structural elements that do not substantially differ from the language of the claims. A person skilled in the art can construct further embodiments and techniques in accordance with the principles of this application by combining and adapting aspects from the various embodiments described above and other known equivalents for each such aspect. Where reference numerals related to the drawings are placed in parentheses within the claims, those reference numerals are merely for clarity of the claims and should not be construed as limiting the claims. [Explanation of Symbols]

[0078] 9. Support frame 10. Generators, electrical machinery 11 Generator bearing 12 Cover Plate 20 Yaw system, rotor 21 Annular gear, magnet module 22 Yaw drive unit, external rotary rim 23 Motor 24 Gearbox 25 pinion 30 staters 31. First Aspect 32. Second Aspect 33 Rotation axis 40 Air gap 50 Stator Structure 60 Circumferential support 71 Air Entrance 72 Air distribution channels 73 Axial air opening 82. First heatsink 84. Second heatsink 86 Heatsink 87. Third heatsink 89. The fourth heatsink 90 Electric coils, electric windings 91 First curved section 92 Second curved section 93 First straight side 94 Second straight side 96 stator teeth 98 Base 100 pitch bearing 101 First side, first end 102 Second side, second end 107 Pitch System 108 pinion 109 Ring gear 110 hub, air cooling system 111 Electrical and mechanical air inlet 112 Electrical and mechanical air outlet 113 First lateral radial air channel 114 Second lateral radial air channel 115 Rotor 120 rotor blades 150 Support surface 160 Wind Turbine 161 Nacer 162 Generators 163 Rotor Shaft 164 Gearbox 165 Support frame, bed plate 166 Generator shaft 170 Wind Turbine Towers PA pitch axis YA yaw axis

Claims

1. An electric machine (10) comprising a rotor (20), a stator (30), and an air gap (40) disposed between the rotor (20) and the stator (30), the stator (30) and / or the rotor (20) comprises a plurality of electric coils (90); one or more of the electric coils (90) carry heat sinks (82, 84) that dissipate heat into the air gap (40), the heat sinks (82, 84, 86, 87, 89) being attached to the electric coils (90) with a thermally conductive material; Electric machine (10).

2. The electric machine (10) of claim 1, wherein the heat sink (82, 84, 86, 87, 89) comprises a plurality of fins.

3. The electric machine (10) of claim 1 or 2, wherein the heat sink (82, 84, 86, 87, 89) is made of a substantially non-magnetic material.

4. The electric machine (10) of any one of claims 1 to 3, wherein the heat sink (82, 87) is attached to the outside of the coil (90).

5. The electric machine (10) of any one of claims 1 to 4, wherein the heat sink (84, 89) is mounted inside the coil (90).

6. 6. The electric machine of claim 1, wherein the electric coil is disposed around the tooth, the coil having a substantially elliptical shape having a first straight side, a second straight side parallel to the first side, a first curved portion connecting the first straight side to the second straight side at a first end, and a second curved portion connecting the first straight side to the second straight side at a second end.

7. The electric machine (10) of claim 6, wherein the heat sink (82, 84, 86, 87, 89) is attached to the first curved portion (91).

8. 8. The electric machine (10) of claim 6 or 7, wherein the second end (102) is closer to a cooling air supply than the first end (101).

9. The electric machine (10) of any one of claims 6 to 8, wherein one or more of the electric coils (90) comprises a plurality of heat sinks (82, 84, 86, 87, 89).

10. 10. The electric machine (10) of claim 9, wherein a first heat sink (82) is attached to an inside of one of the first curved portions (91), a second heat sink (84) is attached to an outside of the first curved portion (91), and a third heat sink (87, 89) is attached to the second curved portion (92), and optionally a further heat sink (86) is attached to one of the first and second straight sides (93, 94).

11. The electric machine (10) of any one of claims 1 to 10, wherein the stator (30) comprises the plurality of electric coils (90).

12. A wind turbine (160) comprising an electric machine (10) according to any one of claims 1 to 11, optionally said electric machine (10) being a permanent magnet generator.

13. A method for modifying the temperature distribution of an electric coil (90) in an electric machine (10), comprising: operating the electric machine (10); measuring the temperature distribution of the electric coil (90) during operation; attaching heat sinks (82, 84, 86, 87, 89) to selected areas of the surface of said electric coil (90) to increase the contact surface with the airflow around said electric coil (90); A method comprising:

14. 14. The method of claim 13, wherein the temperature distribution of the electric coil (90) during operation is more uniform after attaching the heat sink (82, 84, 86, 87, 89) than before attaching the heat sink (82, 84, 86, 87, 89), in particular the difference between the maximum and minimum temperatures of the coil (90) is less than 20°C.

15. 15. The method of claim 13 or 14, wherein operating the electric machine (10) includes providing a cooling airflow through an air gap (40) disposed between a rotor (20) and a stator (30).

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