阅读说明：本技术 具有超导线圈绕组的发电机 (Generator with superconducting coil winding ) 是由 E·格伦达尔 P·H·索伦森 A·托马斯 于 2019-08-07 设计创作，主要内容包括：描述一种发电机(11),其包括：定子(20),所述定子(20)具有至少一个槽(12),形成定子线圈的超导绕组(13)容纳在所述槽(12)中；转子(30),所述转子(30)可旋转地布置在所述定子(20)内部或外部；以及散热器(16),所述散热器(16)热联接到所述超导绕组(13)。所述散热器(16)被构造成运送第一冷却剂以冷却所述超导绕组(13)。所述散热器(16)和所述超导绕组(13)布置在具有热绝缘性质的热屏障(14)内部。(A generator (11) is described, comprising: a stator (20), the stator (20) having at least one slot (12), a superconducting winding (13) forming a stator coil being housed in the slot (12); a rotor (30), the rotor (30) being rotatably arranged inside or outside the stator (20); and a heat sink (16), the heat sink (16) being thermally coupled to the superconducting winding (13). The heat sink (16) is configured to carry a first coolant to cool the superconducting winding (13). The heat sink (16) and the superconducting winding (13) are arranged inside a thermal barrier (14) having thermal insulating properties.)

1. An electrical generator (11), comprising:

a stator (20), the stator (20) having at least one slot (12), a superconducting winding (13) forming a stator coil being housed in the slot (12);

a rotor (30), the rotor (30) being rotatably arranged inside or outside the stator (20); and

a heat sink (16), the heat sink (16) thermally coupled to the superconducting winding (13), the heat sink (16) configured to carry a first coolant to cool the superconducting winding (13); wherein

The heat sink (16) and the superconducting winding (13) are arranged inside a thermal barrier (14) having thermal insulating properties and placed in the slot (12).

2. Generator (11) according to the preceding claim,

wherein the heat sink (16) comprises a support member supporting the superconducting winding (13) and having a cooling channel (17), the cooling channel (17) being configured to receive the first coolant.

3. The generator (11) of any one of the preceding claims,

wherein the stator (20) comprises an additional cooling tube (18), the additional cooling tube (18) being configured to carry a second coolant.

4. Generator (11) according to the preceding claim,

wherein the first coolant is provided to cool the superconducting winding (13) below a first temperature and the second coolant is provided to cool the stator (20) below a second temperature, wherein the first temperature is lower than the second temperature.

5. Generator (11) according to the preceding claim,

wherein the superconducting winding (13) is superconducting at a temperature equal to or lower than the first temperature, and wherein the superconducting winding (13) is not superconducting at a temperature equal to or higher than the second temperature.

6. The generator (11) of any one of the preceding claims,

wherein the stator (20) is at least partially accommodated in a vacuum vessel (19), the vacuum vessel (19) being made of a material that is permeable to magnetic fields.

7. The generator (11) of any one of the preceding claims,

wherein the stator (20) comprises a plurality of laminated stator segments.

8. The generator (11) of any one of the preceding claims,

wherein the stator (20) comprises a core.

9. The generator (11) of any one of the preceding claims,

wherein at least one pump and at least one heat exchanger are provided, which are configured to pump at least one of the first and second coolant through the radiator (16) and/or the additional cooling pipe (18) and to carry out a heat transfer from at least one of the first and second coolant to another medium.

10. The generator (11) of any one of the preceding claims,

wherein the heat transfer from at least one of the first and second coolants to the other medium is effected by convection flow and/or thermal convection.

11. A wind turbine (1) comprising a generator (11) according to any of the preceding claims.

Technical Field

The present invention relates to the field of electrical generators, in particular electrical generators for wind turbines.

Background

In the above-mentioned technical field, it is known to use superconducting motor generators for wind turbines. The use of superconductors in wind turbines is attractive because it permits weight savings and/or the generation of greater amounts of power.

In order to remove the heat generated in the coils, the above-mentioned superconducting generators usually comprise a cooling system for lowering the temperature of the coils to a temperature below the cryogenic temperature, e.g. a temperature of 77K.

Accordingly, there may still be a need to provide a generator, in particular for a wind turbine, comprising a superconducting motor-generator and a cooling system for more efficiently cooling the motor-generator.

There may be a need for a generator that is lightweight and at the same time provides sufficient cooling capacity to maintain superconductivity in the coil windings during operation.

Disclosure of Invention

This need may be met by the subject matter according to the independent claims. The invention is further extended as set forth in the dependent claims.

According to a first aspect of the invention, a generator comprises: a stator having at least one slot in which a superconducting winding forming a stator coil is received; a rotor rotatably disposed inside or outside the stator; and a heat sink thermally coupled to the superconducting winding, the heat sink configured to carry a first coolant to cool the superconducting winding. The heat sink and the superconducting winding are arranged in a thermal barrier having thermal insulating properties and placed in the slot. Preferably, the first coolant is configured to set the superconducting winding in a superconducting state. This generator is lightweight while providing sufficient cooling capacity to maintain superconductivity in the coil windings during operation. Preferably, the stator is cooled by a second coolant to eradicate the heating effect of core losses caused by variable magnetic flux induction in the stator laminations.

The superconducting windings are cooled by a heat sink, which may carry liquid nitrogen (LN 2) or another suitable cooling medium to cool the superconducting windings to the desired operating temperature. The heat sink removes any losses of the superconducting coils during operation and is encased in a material to minimize radiative heating from the superconducting windings of the surrounding stator.

In a broad interpretation of the first aspect of the invention, the radiator may be formed as such from the first coolant. Preferably, however, the heat sink comprises a support member supporting the superconducting winding and further having cooling channels configured to receive and carry the first coolant.

Preferably, the stator comprises an additional cooling tube configured to carry a second coolant, preferably different from the first coolant. The additional cooling pipe may be arranged separately from the radiator. More preferably, the additional cooling pipe carries a water/glycol solution and it removes iron losses during operation. More preferably, a first coolant is provided to cool the superconducting windings below a first temperature and a second coolant is provided to cool the stator below a second temperature, wherein the first temperature is lower than the second temperature. Thus, the radiator and the additional cooling pipe provide a two-stage cooling system having different temperature stages, so that cooling efficiency is improved.

Preferably, the superconducting winding is superconducting at a temperature equal to or lower than said first temperature, and wherein the superconducting winding is not superconducting at a temperature equal to or higher than the second temperature.

Preferably, the stator is at least partially housed in a vacuum vessel, said vacuum vessel being made of a material that is permeable to magnetic fields. Since the stator is enclosed in a vacuum vessel, convective heating of the superconducting windings is minimized.

Preferably, the stator comprises a plurality of laminated stator segments, which may minimize undesired eddy currents in the stator. The laminated stator segment may be a portion of a stator that is housed in a vacuum vessel.

Preferably, the stator comprises a core to minimise magnetic circuit reluctance.

Preferably, at least one pump and at least one heat exchanger are provided, configured to pump at least one of the first and second coolants through the radiator and/or the additional cooling pipe and to carry out a heat transfer from at least one of the first and second coolants to another medium. Alternatively, the heat transfer from at least one of the first and second coolants to the other medium is effected by convective flow and/or thermal convection.

According to a second aspect of the invention, the generator is used in a wind turbine.

It has to be noted that embodiments of the invention have been described with reference to different subject-matters. In particular, some embodiments have been described with reference to apparatus type claims, while other embodiments have been described with reference to method type claims. However, a person skilled in the art will gather from the above and the following description that, unless other notified, in addition to any combination of features belonging to one type of subject matter also any combination between features relating to different subject matters, in particular between features of the apparatus type claims and features of the method type claims is considered to be disclosed with this application.

Drawings

The aspects defined above and further aspects of the invention are apparent from the examples of embodiment to be described hereinafter and are explained with reference to these examples of embodiment. The invention will be described in more detail hereinafter with reference to examples of embodiment but to which the invention is not limited.

Fig. 1 shows schematically and partially a longitudinal section of a wind turbine comprising a motor-generator and a cooling system according to the invention; and is

Fig. 2 shows a schematic partial cross-section through a stator of a generator according to an embodiment of the invention.

Detailed Description

The illustration in the drawings is schematically. It should be noted that in different figures, similar or identical elements are provided with the same reference numerals.

Fig. 1 shows schematically and partially a longitudinal section of a wind turbine 1 comprising a motor generator 11 according to the invention and a cooling system. The wind turbine 1 comprises a tower 2 mounted on a base, not depicted. The nacelle 3 is arranged on top of the tower 2.

The wind turbine 1 further comprises a wind rotor 5 having two, three or more blades 4 (only two blades 4 are visible in the perspective view of fig. 1). The wind rotor 5 is rotatable about an axis of rotation Y. In the following, the terms axial, radial and circumferential are made with reference to the axis of rotation Y, if not stated differently.

The blades 4 extend radially with respect to the rotation axis Y.

The wind turbine 1 comprises a permanent magnet motor generator 11. According to other possible embodiments of the invention (not shown in the drawings), the invention can be applied to any other type of electric machine with an internal or external rotor and with any type of field excitation (for example permanent magnets or DC coils).

The wind rotor 5 is rotationally coupled to a generator 11, either directly (e.g. directly driven) or by means of a rotatable main shaft 9 and through a gearbox (not shown in fig. 1). A schematically depicted bearing assembly 8 is provided in order to hold the main shaft 9 and the rotor 5 in place. The rotatable spindle 9 extends along the axis of rotation Y.

The motor generator 10 includes a stator 20 and a rotor 30. The rotor 30 is rotatable relative to the stator 20 about a rotation axis Y. In the illustrated embodiment, the rotor 30 is rotatably disposed outside the stator 20. The rotor 30 has a plurality of permanent magnets (not shown).

Fig. 2 shows a schematic partial cross-section through a stator 20 of a generator 11 according to an embodiment of the invention. The stator 20 has a plurality of slots 12, and the superconducting windings 13 forming the stator coils are accommodated in the slots 12. The stator coil of the stator 20 faces the rotor 30. When the rotor 30 rotates relative to the stator 20 having the stator coils, an AC current is generated in the stator coils.

A heat sink 16 thermally coupled to the superconducting winding 13 is arranged in the slot 12. The heat sink 16 is configured to carry a first coolant to cool the superconducting windings 13. The first coolant is used to cool the superconducting winding 13. The first coolant is configured to set the superconducting winding 13 in a superconducting state. The heat sink 16 and the superconducting winding 13 are arranged in a thermal barrier 14 having thermal insulating properties. This material may be any suitable material having thermal insulating properties.

In broad interpretation, the radiator 16 may be established as such by the first coolant. Alternatively, as shown in the illustrated embodiment, the heat sink 16 includes a support member that supports the superconducting windings 13 and has cooling channels 17, the cooling channels 17 being configured to receive the first coolant. The cooling channel 17 has a circular cross-section; however, the cooling channel 17 may equally have a rectangular cross-section or any other cross-section. Since the superconducting winding 13 is generally made of a material that can be set in a superconducting state, the superconducting winding 13 is generally made of a refractory material, such as a type of ceramic that does not have sufficient solidity. Since the superconducting windings 13 are supported by the heat sink 16, said heat sink 16 may also act as a support member and it is typically formed of a stronger material (e.g. metal), the superconducting windings 13 are protected and will be less likely to be damaged.

This structure is efficient and light weight and at the same time provides sufficient cooling capacity to maintain superconductivity in the superconducting windings 13 of the stator coil during operation.

The stator 20 includes additional cooling tubes 18, the additional cooling tubes 18 being configured to carry a second coolant, preferably different from the first coolant. In the illustrated embodiment, additional cooling tubes 18 are placed within the stator core. It may also be placed at other locations that will also provide sufficient thermal contact to the stator core. While the first coolant is provided to cool the superconducting windings 13 below a first temperature, the second coolant is also provided to cool the stator 20 below a second temperature, wherein the first temperature is lower than the second temperature. Although the superconducting winding 13 is superconducting at a temperature equal to or lower than the first temperature, the superconducting winding 13 may not be superconducting at a temperature equal to or higher than the second temperature. Such a superconducting winding 13 is also referred to as HTS (high temperature superconductor), although it may also be LTS (low temperature superconductor).

The superconducting winding 13 may have second-order superconductivity. Up to the so-called "lower critical field", the second-order superconductor is in the so-called Meissner phase and functions like a first-order superconductor. In the case of higher magnetic fields, the magnetic field lines in the form of so-called flux tubes can penetrate the material before the superconducting state in the "upper critical field" is completely destroyed. The magnetic flux in a flux tube is generally equal to a magnetic flux quantum (magnetic flux quantum).

The first temperature may be-196 ℃ or less, preferably-206 ℃ or less. The first coolant may be liquid nitrogen (LN or LN)₂) Liquid helium (b)⁴He or³He) or any other coolant suitable for cooling below the first temperature.

The second temperature may be-20 ℃ or lower, preferably-50 ℃ or lower. The second coolant may be water, glycol, ethanol, mixtures thereof, or any other coolant suitable for cooling below the second temperature.

Since the stator 20 is relatively large, it comprises a plurality of laminated stator segments, for example for a wind turbine 1 with an output power above 1 MW. The laminated stator segments may minimize eddy currents. Alternatively, the stator 20 may be made in one piece, for example for smaller wind turbines with less output power.

The laminated stator segments of the stator 20 are housed in a vacuum vessel 19, as shown in fig. 2. The vacuum vessel 19 is made of a material that is permeable to magnetic fields. This is because the generator 11 uses a magnetic field generated between the stator coil of the stator 20 and the rotor 30. The magnetic flux must pass through the vacuum vessel 19. The material of the vacuum vessel 19 may be selected from a non-magnetic material, such as aluminium or stainless steel, or some plastic or fibrous material. Additional thermal insulation of the stator 20 is achieved by the air gap that exists between the rotor 30 and the stator coils of the stator 20.

The stator 20 preferably includes a core disposed radially inside the laminated stator segments. The iron core minimizes magnetic circuit reluctance.

Additional cooling tubes 18 may be arranged within this stator core and/or laminated stator segment.

To move the first and second coolants, two pumps (not shown) are provided, which are configured to pump the first and second coolants through the radiator 16 and the additional cooling pipe 18, respectively. Furthermore, the radiator 16 and the additional cooling tubes 18 are connected to one or more heat exchangers (not shown) for effecting heat exchange between the first and second coolants and the surroundings or another medium. This heat exchange is known in the art and need not be described further. Alternatively, convective flow may be used without a pump.

Advantageously, the present invention enables cooling of the stator 20 to eradicate the heating effect of core losses caused by variable magnetic flux induction in laminated stator segments of the stator 20, and cooling the superconducting windings 13 sufficiently to make them superconducting. The laminated stator segments are enclosed in a vacuum vessel 19 to minimize convective heating of the superconducting windings 13.

In addition, two-stage cooling is achieved to cool the stator 20 via the expansion cooling tube 18 with a water/glycol solution (or similar coolant) to cool the stator 20 and remove iron losses during operation. The superconducting winding 13 is then further cooled by an adjacent heat sink 16 comprising a cooling channel 17, the cooling channel 17 carrying liquid nitrogen (LN 2) or another suitable coolant to further cool the superconducting winding 13 to the desired operating temperature. The heat sink 16 removes any losses of the superconducting windings 13 during operation and is encased in a thermal barrier 14, the thermal barrier 14 being made of a material that minimizes radiative heating from the superconducting windings 13 of the surrounding stator 20.

It should be noted that the term "comprising" does not exclude other elements or steps and the "a" or "an" does not exclude a plurality. Also elements described in association with different embodiments may be combined. It should also be noted that reference signs in the claims shall not be construed as limiting the scope of the claims.