A superconducting disc motor

Abstract

The invention discloses a superconducting disc motor, wherein the stator comprises a stator shell and a stator core; the rotor comprises a rotor shaft; the stator core comprises a wedge-shaped core body formed by stacking oriented silicon steel; a superconducting coil is wound between the two ends of the wedge-shaped core body; a plurality of stator cores are distributed and rotated about an axis parallel to the direction of the magnetic field thereof and arranged in a disc shape; the stator cores arranged in a disc shape are coaxially embedded in the stator shell; a rotor back iron shell is coaxially sleeved on the hollow rotor shaft, and a copper heat-conducting component is included in the hollow rotor back iron shell; the copper heat-conducting component comprises a columnar end parallel to the rotor axis, and the columnar end is arranged in a circular ring along the rotor rotation direction; a superconducting coil is wound on the columnar end extending from the rotor back iron shell to the outside of the rotor back iron shell; the outer shell comprises a cooling gas / liquid circuit, and the cooling circuit cools the hollow cavity in the potted stator; a cooling gas / liquid circuit is included in the rotor back iron shell, and the rotor shaft is a hollow shaft.

Description

Technical Field

[0001] The invention relates to the fields of disc motors and superconducting technology, and in particular to a superconducting disc motor. Background Art

[0002] The disc motor, also known as the axial flux motor, has the main magnetic circuit direction of the motor axial direction. Compared with the traditional radial flux cylinder motor, the disc motor has the advantages of small size, light weight, high torque density and high power density.

[0003] The structures of existing axial flux disc motors mainly include single stator and single rotor, double stator and single rotor, double rotor and single stator and multi-stage motor structures, in which the stator part is composed of stator core and copper wire winding, and the rotor part is composed of rotor bracket, rotor back iron and permanent magnet magnetic steel.

[0004] The traditional motor with dual rotor and single stator structure can be found in CN107408875A / CN109478808A. The motor in CN109478808A is a YASA type yokeless axial flux motor, and the patent is mainly a new type of stator core structure and production process. Although the scheme optimizes the mechanical stability and / or good or improved cooling capacity based on the YASA type motor, its winding still uses copper wire. Therefore, although the heat dissipation is improved, as the alternating current is passed, copper wire loss will still be generated in the form of heat energy, causing the temperature of the stator part to rise. And the rotor part will also produce losses due to the eddy current generated by the alternating current inductance, causing the temperature of the rotor part to rise.

[0005] Although the name of patent CN101262169A contains the words "axial flux" and "high-temperature superconducting motor", it is essentially a topological structure optimization of a stepper motor.

[0006] Although the title of patent CN101599690B also contains the words "axial flux motor" and "high-temperature superconducting motor", its content focuses only on the optimization of axial and tangential magnetic circuits, which is essentially different from the magnetic circuit form of the YASA type axial flux motor. At the same time, there is no in-depth creative design for the description of superconducting materials and the use process.

[0007] Patent CN107769501B is a YASA type disc motor, but its solution mainly involves the optimization of the magnetic circuit of the rotor part, and the purpose of enhancing the magnetic flux strength of the motor is achieved by additionally setting permanent magnets in the axial direction.

[0008] In summary, in a disc motor, when copper wire windings are used, the current loss in the copper wire will reduce the motor efficiency, and the heat generated will cause the stator temperature to rise; in addition, the eddy current loss of the upper magnetic steel of the rotor disk causes the rotor temperature to rise, and if the temperature is too high, it may cause the magnetic steel to demagnetize. Summary of the invention

[0009] A technical solution provided by the present invention is a superconducting disc motor, which solves:

[0010] 1. The loss (in the form of heat energy) generated by the stator copper wire will greatly reduce the operating efficiency of the motor, and at the same time cause the temperature to rise during the operation of the motor and increase the copper loss of the motor;

[0011] 2. The use of superconducting materials that can generate stronger magnetic fields can further enhance the air gap magnetic field of the motor;

[0012] 3. The permanent magnets of the motor rotor generate losses (in the form of heat energy), causing the temperature to rise during the operation of the motor;

[0013] 4. The eddy current loss of the upper magnetic steel of the rotor disk causes the rotor temperature to rise. If the temperature is too high, it may cause the magnetic steel to demagnetize;

[0014] The technical solution of the present invention is: for the disc-type superconducting motor, the stator part is designed to adopt a stator core, a high-temperature superconducting tape (such as YBCO) coil and a high-temperature superconducting tape protection cover, and the rotor part also adopts a superconducting coil.

[0015] The material of the protective cover can be selected from structural materials with softer surface hardness, higher thermal conductivity and better insulation.

[0016] The stator superconducting structure specifically includes:

[0017] The stator housing is implemented as a disc-shaped bracket body with a central hole penetrating in the axial direction. A series of grooves are provided on the inner ring surface of the bracket body, including: an embedding groove for embedding the stator core and a wedge groove for embedding the wedge. The embedding groove is U-shaped, and multiple embedding grooves are evenly arranged along the rotation direction of the inner ring of the bracket body. T-shaped wedge grooves are arranged between adjacent embedding grooves, and the arrangement of the wedge grooves and the embedding grooves maintains the same rotation center.

[0018] The stator fixing assembly is coaxially assembled in the center hole of the bracket body. The stator fixing assembly is a cylindrical body with an outer edge of a port. T-shaped wedge grooves are also arranged on the outer edges of the ports on both sides. The T-shaped wedge grooves on the bracket body correspond to the T-shaped wedge grooves on the stator housing, which facilitates the assembly of the I-shaped wedge (conveniently connecting the fixing assembly with the stator housing using the I-shaped wedge, and further determining the installation position of the stator core to ensure the concentricity of the stator core).

[0019] At the same time, a radially concave T-groove is arranged on one side of the outer edge of the ports on both sides of the stator fixing assembly, one embedded groove corresponds to one T-groove, and the T-groove can be used to assemble with one end of the wedge-shaped iron core body. That is, the wedge-shaped iron core body can be installed in the embedded groove and inserted into the T-groove by inserting its end into the T-groove so as to be assembled between the stator housing and the stator fixing assembly.

[0020] The wedge is a connecting piece with an I-shaped cross section. One end of the wedge is inserted into the T-shaped wedge groove on the bracket body, and the other end is inserted into the T-shaped wedge groove on the stator fixing assembly, so that the stator housing and the stator fixing assembly can be tightened along the stator radial direction.

[0021] The stator core is mainly a wedge-shaped core body, which is made of oriented silicon steel laminated, bonded and welded. Because it is suitable for disc motors, the solid wedge-shaped core body is cut and designed according to the division of the disc. That is, the wedge-shaped core body is I-shaped, with pole shoes at both ends, and the two sides are cut into bevels. The superconducting tape is wound between the pole shoes at both ends of the wedge-shaped core body. Specifically, a layer of high-temperature superconducting tape protective cover is first installed between the pole shoes at both ends of the wedge-shaped core body, and the superconducting tape, such as yttrium barium copper oxide (YBCO) superconducting tape, is wound on the surface of the high-temperature superconducting tape protective cover. Since the superconducting crystal layer in the YBCO tape is thin and brittle, it is easy to break to affect the overall resistance characteristics. Therefore, the curvature needs to be kept greater than a certain value when winding. Generally, the superconducting coil is wound first and then installed on the stator core.

[0022] The stator core is embedded in the slot, and multiple stator cores are arranged in a circular disc shape. The stator core arranged in a circular disc shape is arranged coaxially with the stator housing and the stator fixing assembly, and the magnetic field formed by the stator core wound with the superconducting coil has a magnetic field direction parallel to the above-mentioned axial direction.

[0023] When the rotor is arranged on the axial end side of the stator housing, the air gap magnetic field formed by the superconducting coil on the stator interacts with the rotor magnetic field, driving the rotor to rotate.

[0024] Based on the above structure, the present solution further solves the cooling and heat dissipation problems in the structure.

[0025] The stator housing, stator fixing assembly, stator core, wedge, rotor, etc. are all integrated into the motor housing, so a series of cooling circuits need to be arranged in the housing. We know that the stator inside the motor generally needs to be potted, usually using resin potting to achieve insulation and fixation effects. Similarly, in this structure, the stator superconducting structure in the housing needs to be potted. In this solution, the potting of the stator superconducting structure uses general-purpose epoxy resin and other materials, or injection molding or thermosetting, thermally conductive BMC materials with better thermal conductivity can be used to replace the resin potting process.

[0026] The stator housing includes a structural hole penetrating in the axial direction thereof, and the structural hole can form a cooling cavity. An external water channel is arranged on the axial end surface of the stator housing to connect adjacent structural holes, and each two adjacent structural holes are connected through an external water channel to form a cooling water channel in the stator. The external water channel can be implemented as a flow channel opened on the sheet material, and the flow channel connects two adjacent structural holes.

[0027] The characteristic of this scheme is that the potting is completed by positioning the end faces of the wedge, the housing and the pole shoe of the stator core mutually. During potting, a part of the hollow cavity is reserved in the stator superconducting structure, and the airtightness of the hollow cavity is ensured by thermosetting BMC material or epoxy resin.

[0028] The cooling methods used for the stator superconducting structure include:

[0029] 1. The large-diameter gap reserved in the casing is the coolant passage, which together with the upper and lower parts of the casing constitutes a circulating distributed cooling circuit for the coolant, or an inner and outer jacket combination to form a cooling circuit. The choice of coolant gas can be: gaseous nitrogen → liquid nitrogen → gaseous helium.

[0030] The hollow cavity can be cooled by a dry powder refrigerator or the circulating distributed cooling method described in the previous step. Since the structural strength of the upper and lower surfaces of the cavity is relatively low, it is necessary to ensure a reasonable pressure inside the cavity. The internal step-by-step cooling must ensure that the temperature of the stator and rotor superconducting windings is ≤80K, and the preferred range is 30-50K.

[0031] The rotor superconducting structure specifically includes:

[0032] The rotor shaft is a hollow shaft, which passes through the stator. The rotor shaft is coaxially sleeved with a rotor back iron shell, and the rotor back iron shell is arranged on both sides of the stator. Therefore, direct current is passed through the superconducting coil in the rotor to generate a constant electromagnetic field under an ideal state. At this time, the superconducting winding is reduced to below the critical temperature and reaches the superconducting state. Through the low resistance characteristics in the superconducting state, a steady-state magnetic field is generated with a constant ring current to replace the permanent magnet. In the stator, superconducting coils are used to replace traditional copper coils.

[0033] The rotor back iron shell includes a hollow shell in the shape of a disc and an end plate sealed and assembled at the rear end of the hollow shell. The end plate is encapsulated at the rear end of the hollow shell to form a cavity inside the rotor back iron shell.

[0034] The rotor back iron shell is mounted on the rotor shaft, so the center of the hollow shell and the end plate includes an axial hole for sealing and assembling the rotor shaft. The rotor shaft is in the shape of a stepped shaft, so the structural assembly can be achieved by matching the corresponding shaft diameter with the corresponding shaft hole on the rotor back iron shell. It should be noted that in order to ensure the airtightness of the cavity, a sealing ring is added at the assembly point of the rotor shaft and the corresponding shaft hole, which can effectively ensure the sealing effect of the cavity.

[0035] The copper heat-conducting component is installed in the cavity. The copper heat-conducting component includes a plurality of columnar ends parallel to the rotor axis. The columnar ends are arranged in a circular ring along the rotor rotation direction. A connecting portion extends from the root of the columnar end to connect adjacent columnar ends in series. The connecting portions are continuously connected in series to form an annular bottom that connects all columnar ends in series.

[0036] The front end surface of the hollow shell includes a through hole for matching the cylindrical end, and the through hole is distributed in a circular trajectory corresponding to the columnar end. The copper heat-conducting component is assembled by inserting the columnar end into the through hole, and the columnar end extending out of the hollow shell is wound with a YBCO superconducting coil. A constant DC current is passed through the YBCO superconducting coil, and the superconducting low resistance state will cause the current to circle in the racetrack winding all the time, so that it can generate a constant electromagnetic field under an ideal state, which is used to replace the permanent magnet magnetic steel.

[0037] The cavity formed in the rotor back iron shell includes a distributed cooling gas / liquid loop. The cooling liquid gas introduced into the distributed cooling gas / liquid loop can be selected as: gas / liquid nitrogen, gas / liquid helium or other low-temperature coolants.

[0038] The advantages of the present invention are:

[0039] 1. Due to the use of superconducting coils, the loss of Joule heat of copper wire is reduced, that is, the efficiency is higher. In addition, the motor can pass a large current, so that a greater torque can be obtained.

[0040] 2. At the same time, the new stator superconducting structure and potting method facilitate the installation of superconducting coils, and the combination of cooling circuits and cavities makes the cooling effect more ideal.

[0041] 3. The rotor part uses YBCO superconducting coils to replace permanent magnets, which can improve the temperature rise of the rotor part and avoid the demagnetization of the permanent magnet caused by excessive rotor temperature. Compared with traditional motors, the output torque is greater. Because in the production of prototypes, the eddy current of the permanent magnet is exponentially related to the size of the magnetic field density B, so when the motor is running, the larger excitation magnetic field will cause the local eddy current of the permanent magnet to be larger, so that the surface of the permanent magnet will produce a stronger local eddy current. This temperature imbalance characteristic will cause the local permanent demagnetization of the permanent magnet; similarly, when the rotor pole number is large or the speed is fast, resulting in a higher operating frequency, a larger rotor eddy current loss will be generated, resulting in permanent demagnetization of the permanent magnet. In the design of the present invention, since the superconducting stator can pass a very large current to generate an extremely strong magnetic field, if a conventional high-grade NdFeB permanent magnet is used, there may be a hidden danger of demagnetization. Therefore, this patent uses a superconducting coil surrounded by a constant current to replace the traditional permanent magnet, which can not only generate a stronger magnetic field, but also eliminate the risk of permanent demagnetization.

[0042] 4. At the same time, the new rotor superconducting structure has a simpler cooling circuit and uses superconducting cooling through the built-in cavity, which has a more outstanding cooling effect.

[0043] 5. In summary, compared with traditional motors, this superconducting motor has lower losses and can avoid temperature rise problems, thereby improving the overall performance of the motor. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] The present invention will be further described below in conjunction with the accompanying drawings and embodiments:

[0045] Figure 1 This is the stator and rotor assembly diagram of the superconducting disc motor;

[0046] Figure 2 Exploded diagram of the stator and rotor assembly of the superconducting disc motor;

[0047] Figure 3 This is the assembly drawing of the superconducting structure stator (without fixed components);

[0048] Figure 4 It is the structural diagram of the stator core;

[0049] Figure 5 is a front view of the stator housing;

[0050] Figure 6 It is a structural diagram of the stator fixing assembly;

[0051] Figure 7 This is an exploded view of the rotor superconducting structure;

[0052] Figure 8 This is the assembly diagram of the double-sided rotor superconducting structure;

[0053] Fig. 9It is a cross-sectional view of the double-sided rotor superconducting structure;

[0054] Fig.10 It is a cross-sectional view of the water channel arrangement on the stator housing;

[0055] Among them, 1. wedge-shaped iron core; 2. stator superconducting coil; 3. high-temperature superconducting tape protection cover; 4. stator shell; 5. stator fixing assembly; 6. wedge; 7. T-slot; 8. hollow shell; 9. end plate; 10. copper column thermal conductive structure; 11. copper terminal; 12. sealing ring; 13. hollow shaft; 14. rotor superconducting coil. DETAILED DESCRIPTION

[0056] Example 1

[0057] This solution adopts an 18-slot 12-pole structure, that is, the stator part uses 18 superconducting coils to replace the traditional copper coils, and the rotor part uses 12 superconducting coils to replace the permanent magnets.

[0058] Specifically, the stator part includes: a stator housing, a stator fixing assembly, a wedge, and a stator core.

[0059] Stator core and superconducting coil:

[0060] Due to the properties of superconducting materials, we need to wind the stator superconducting coil 2 first, then put the high-temperature superconducting tape protection cover 3 on the lower half of the iron core, put the superconducting coil outside the high-temperature superconducting tape protection cover, and finally embed or splice the upper half using mortise and tenon / gap fit.

[0061] Assembly and principle of stator housing:

[0062] 1. Insert the pole shoe of the wedge-shaped core body 1 with the stator superconducting coil 2 into the T-slot 7 on the stator fixing assembly 5. The concentricity of the stator core can be ensured by the positioning design of the stator housing 4.

[0063] 2. Place the assembled stator core and upper and lower inner positioning plates into the stator housing;

[0064] 3. Insert the wedge 6 into the gap formed by the stator assembly and the stator fixing assembly to ensure the coaxiality of the stator housing relative to the iron core;

[0065] 4. The wedge 6, the housing and the end faces of the pole shoe of the stator core are positioned with each other to complete the potting. The potting can be made of general epoxy resin or other materials, or injection molding or BMC thermal conductive materials with good thermosetting properties can be used to replace the potting process.

[0066] Cooling system in the stator superconducting structure: The stator can adopt a distributed cooling structure:

[0067] 1. The large-diameter gap reserved in the stator housing is the coolant passage, which together with the upper and lower parts of the housing constitutes a coolant circuit, or an inner and outer jacket combination constitutes a cooling circuit. The coolant gas can be selected in the form of: gaseous nitrogen → liquid nitrogen → gaseous helium.

[0068] 2. The stator can be partially potted with the air gap plane formed by the end face of the stator pole shoe or insulated and plastic-sealed with BMC material, and a part of the hollow cavity can be reserved in the stator. The hollow cavity is made of thermoplastic BMC material or epoxy resin to ensure airtightness, and the internal step-by-step cooling is used to ensure that the internal temperature of the cavity is ≤80K, and the preferred range is 30-50K.

[0069] 3. If Fig.10 The stator housing includes a structural hole penetrating in the axial direction thereof, and the structural hole can form a cooling cavity. An external water channel is arranged on the axial end surface of the stator housing to connect adjacent structural holes, and every two adjacent structural holes are connected through an external water channel to form a cooling water channel in the stator.

[0070] Specifically, the rotor part includes: a hollow shell 8 , an end plate 9 , a copper column heat-conducting structure 10 (for cooling and fixing the rotor superconducting coil) and a sealing ring 12 which are sleeved on the hollow shaft 13 .

[0071] First, the copper column heat-conducting structure 10 (i.e., the copper heat-conducting component) is placed in the rotor back iron shell, and the copper terminal 11 extends out of the rotor back iron shell, and then the sealing ring 12 and the end plate 9 are installed, so that a cavity is formed inside the rotor back iron shell to accommodate the step-by-step cooling gas / liquid circuit. The upper and lower surfaces of the formed cavity are composed of materials with strong structure and low magnetic permeability such as austenitic steel / duralumin / titanium alloy, so the formed cavity has a high structural strength.

[0072] A constant direct current is passed through the rotor superconducting coil 14, and the superconducting low resistance state causes the current to continuously circle in the racetrack winding, so as to generate a constant electromagnetic field under an ideal state to replace the permanent magnet steel.

[0073] The rotating shaft adopts a hollow shaft structure, and the rotor part can be maintained through the hollow shaft 7 (such as passing liquid nitrogen or passing current to the rotor superconducting coil).

[0074] Cooling system in the structure of superconducting rotor:

[0075] The distributed cooling gas / liquid loop can also directly and effectively cool the superconducting coils 6 of the rotor. Since the cavity can ensure its airtightness, the rotor part can transfer heat through the copper terminals.

[0076] The embodiments of the present invention are only illustrative of the principles and effects of the present invention, and are not intended to limit the present invention. Anyone familiar with the technology may modify or change the above embodiments without violating the spirit and scope of the present invention. Therefore, all equivalent modifications or changes made by those with ordinary knowledge in the technical field without departing from the spirit and technical ideas disclosed in the present invention should still be covered by the claims of the present invention.

Claims

1. A superconducting disc motor, comprising: stator and rotor; The stator comprises: a stator housing and a stator core embedded in the stator housing; the rotor comprises: a rotor shaft passing through the axial direction of the stator; and the characteristics are: The stator core comprises a wedge-shaped core body formed by stacking oriented silicon steel layers; a superconducting coil is wound between the pole shoes at both ends of the wedge-shaped core body; A plurality of stator cores are distributed and rotated about an axis parallel to the direction of the magnetic field and arranged in a disc shape; the stator cores arranged in a disc shape are coaxially embedded in the stator housing; A rotor back iron shell is coaxially sleeved on the hollow rotor shaft, and the hollow rotor back iron shell includes a copper heat conducting component; The copper heat-conducting component comprises a columnar end parallel to the rotor axis, the columnar ends are arranged in a circular ring along the rotor rotation direction; and an annular bottom located at the root of the columnar end for connecting a plurality of columnar ends in series; a superconducting coil is wound on the columnar end extending from the rotor back iron shell to the outside of the rotor back iron shell; The housing is used to pot the stator in the housing, the potted stator includes a hollow cavity, and a part of the hollow cavity is reserved in the stator superconducting structure; the housing includes a cooling gas / liquid circuit, and the cooling circuit cools the hollow cavity; A cooling gas / liquid circuit is included in a cavity formed in the rotor back iron housing; The stator housing comprises a disc-shaped bracket body which penetrates axially, and comprises: an embedding groove for embedding the stator core and a wedge groove for embedding the wedge on the inner ring of the bracket body; The stator fixing assembly includes wedge grooves distributed in the rotation circumferential direction thereof; Between adjacent stator cores are included: wedges for tightening the stator housing and the stator fixing assembly along the stator radial direction and realizing the positioning and separation of adjacent stator cores; The cooling gas / liquid used in the cooling circuit includes: gas / liquid nitrogen, gas / liquid helium.

2. A superconducting disc motor according to claim 1, characterized in that: The cooling circuit includes a distributed cooling circuit and an inner and outer jacket combined cooling circuit.

3. A superconducting disc motor according to claim 1, characterized in that: The stator is potted based on the air gap plane formed by the end faces of the stator core pole shoes, and the potting materials of the stator include: epoxy resin and BMC thermal conductive material.

4. The superconducting disc motor according to claim 1, characterized in that: A superconducting tape protective sleeve is sleeved between the pole shoes at both ends of the wedge-shaped iron core body, and a yttrium barium copper oxide superconducting coil, a barium series superconducting coil, a lanthanide series superconducting coil, or an actinide series superconducting coil is wound on the surface of the superconducting tape protective sleeve.

5. The superconducting disc motor according to claim 1, characterized in that: The rotor back iron shell comprises a disc-shaped hollow shell and an end plate sealably mounted on the rear end of the hollow shell; both the hollow shell and the end plate comprise shaft holes for sealably mounting the rotor shaft.

6. The superconducting disc motor according to claim 1, characterized in that: The surface material of the cavity formed in the rotor back iron shell includes austenitic steel, hard aluminum, and titanium alloy.

7. The superconducting disc motor according to claim 1, characterized in that: The stator housing includes a structural hole penetrating in the axial direction thereof, and an external water channel is arranged on the axial end surface of the stator housing to connect adjacent structural holes; every two adjacent structural holes are connected by an external water channel to form a cooling water channel in the stator.

8. The superconducting disc motor according to claim 7, characterized in that: The external water channel includes a flow channel opened on the plate.

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