An oil-cooled air-gap armature, its fabrication method, and a motor using the armature structure.

Abstract

This application belongs to the field of motor technology, specifically relating to an oil-cooled air-gap armature, its manufacturing method, and a motor using this armature structure. The oil-cooled air-gap armature consists of stator core laminations, coil fixing teeth, stator coils, and slot wedges. Multiple coil fixing teeth with oil-cooling channels are circumferentially distributed and installed in the inner circular fixing slots of the stacked stator core laminations. The stator coil is embedded in the winding slots formed between the multiple coil fixing teeth and fixed by the slot wedges. Multiple oil-cooling channels are formed within the coil fixing teeth. This application facilitates reliable fixing of the stator coil in the winding slots, and the oil-cooling channels effectively remove heat from the stator coil, making it suitable for applications in motors operating at high frequencies, high field strengths, and high impact resistance.

Description

Technical Field

[0001] This invention belongs to the field of motor technology. Specifically, it relates to an oil-cooled air-gap armature and its preparation method, as well as a motor using the armature structure. It is suitable for applications such as high-capacity high-temperature superconducting motors for aviation or ship propulsion, and high-temperature superconducting wind turbines, which require high power, low speed, compact structure, high power density, strong impact resistance, and high heat load. Background Technology

[0002] With increasingly stringent global carbon emission controls, the shipbuilding, marine engineering, and aerospace sectors are undergoing a transformation from fuel-powered to electric propulsion. In this process, power density has become a core indicator. Traditional permanent magnet synchronous motors (PMSMs) are limited by Joule heat losses in the copper windings and magnetic saturation of the iron core, making it difficult for their power density to break through the physical bottleneck of 10-15 kW / kg.

[0003] High-temperature superconducting (HTS) technology, particularly the maturity of second-generation yttrium barium copper oxide (YBCO) coated conductors, has made it possible to break through this limit. HTS motors utilize the zero-resistance characteristic of superconducting coils at low temperatures (20K-77K), enabling them to carry current densities two orders of magnitude higher than copper wires and generate extremely strong magnetic fields, thus achieving an ultra-high power density of 20-30 kW / kg in the same volume. This makes HTS motors a key technology for future all-electric ship propulsion systems and large electric passenger aircraft (such as NASA's N3-X concept design).

[0004] To avoid excessive eddy current losses in the stator teeth caused by the rotating magnetic field, high-performance HTS motors often employ an air-gap armature structure to improve air-gap magnetic flux density and power density. For cooling the air-gap armature, conventional air cooling and water cooling methods are insufficient to meet heat dissipation requirements, necessitating more efficient cooling methods such as internal winding liquid cooling, direct immersion oil cooling, or spray cooling.

[0005] To address the heat dissipation challenge of air-gap armatures, various oil-cooled air-gap armature heat dissipation solutions exist in the prior art. For example, US Patent 6856053B2 discloses an oil-cooled air-gap armature structure; however, this solution results in poor overall stiffness and weak impact resistance. Furthermore, the open structure of the oil-cooling channel on the non-magnetic support teeth makes it prone to scratching the insulation when the coil is embedded in the winding slot, posing a manufacturing risk. Alternatively, additional pads or other protective structures may be required, reducing slot fill factor and increasing thermal resistance. US Patent 2010 / 01942232A1 discloses another air-gap armature structure combining composite materials and stainless steel. This structure relies on the impregnation varnish in the slot gap to resist impacts or Lorentz forces under conditions of strong impact or high instantaneous load. However, extreme conditions may cause insulation tearing, affecting motor safety and lifespan, and increasing thermal resistance between the coil and the flow channel. In addition, the structure composed of stainless steel teeth and composite materials is complex and has poor assembly processes. Chinese patents CN111446132B and CN110739190B disclose an air-gap armature structure composed of several composite material blocks, non-magnetic or weakly magnetic metal plates, and adhesives. Under the frequent changing operating conditions, high torque fluctuations, and thermal cycling loads of the propulsion motor, the shear strength of the organic adhesive will decrease over time, posing a significant risk of debonding and tooth ejection. Furthermore, due to the low thermal conductivity of the composite material blocks, this structure requires flow channels to be arranged within the slot to improve heat dissipation, which leads to a decrease in slot fill factor and limits the improvement of power density.

[0006] In addition, there are other technical solutions for in-slot oil cooling. For example, CN118611287A provides a method of laying foamed insulating paper in the slot to fix the coil and form a cooling channel. This solves the problems of reduced slot fill factor and complicated manufacturing process caused by the traditional solution of setting cooling channels in the stator winding slot. However, in this technical solution, the coil and core lamination do not form a well-contact whole, the overall rigidity is poor, and the impact resistance is poor. Summary of the Invention

[0007] The purpose of this invention is to overcome the shortcomings of the prior art and to propose an oil-cooled air-gap armature, its preparation method, and a motor using the armature structure, so as to solve the problems of insufficient overall stiffness, poor processing and assembly technology, and insufficient cooling efficiency of the existing air-gap armature scheme.

[0008] To achieve the above objectives, the present invention provides the following technical solution: An oil-cooled air-gap armature includes a stator core lamination, coil fixing teeth, a stator coil, and a slot wedge; wherein the stator core lamination (1) has a fixing slot punched in its inner circle, and the coil fixing teeth are installed in the fixing slot of the inner circle of the stacked stator core lamination along the circumferential direction of the stator core lamination; the stator coil is installed in the stator winding slot composed of the stator core lamination and several coil fixing teeth, and is fixed by the slot wedge.

[0009] Furthermore, the stator core laminations are either full-circle annular laminations or fan-shaped laminations. The inner circle of the stator core laminations is stamped with "dovetail" or "vertical tree" shaped fixing slots. The type of fixing slot is determined according to the impact resistance requirements. The "dovetail" structure is used for low impact resistance requirements, while the "vertical tree" structure is used for high impact resistance requirements. The number of fixing slots is the same as the number of stator slots of the motor.

[0010] Furthermore, the coil fixing teeth are either ceramic teeth or thermally conductive plastic teeth, and their number is the same as the number of stator slots of the motor. If the axial length is long, they can be formed in sections. Ceramic teeth are manufactured into green blanks using ceramic injection molding (CIM) or gel casting processes, and then sintered at high temperature. Thermally conductive plastic teeth are injection molded, with polyphenylene sulfide (PPS) or polyether ether ketone (PEEK) as the matrix material and ceramic powders such as alumina and boron nitride as the filler material. The filler ratio is selected according to the strength and thermal conductivity requirements, and the thermal conductivity is 1-10 W / mK.

[0011] There are cooling oil channels on both sides of the coil fixing teeth. The number and size of the cooling oil channels are determined according to the heat load.

[0012] This invention application also provides a method for fabricating an oil-cooled air-gap armature structure, the method comprising: S1: Separately manufacture stator core laminations, stator coils, and slot wedges, and stack the stator core laminations into a whole; S2: Select the type of coil fixing teeth according to the impact resistance requirements of different application scenarios, and select the corresponding manufacturing process according to the type of coil fixing teeth; ceramic teeth are selected for low impact resistance requirements. After sintering preparation, the salt core is filled into the cooling oil channel and a clearance fit is adopted; thermally conductive plastic teeth are selected for high impact resistance requirements. Before preparation, the salt core is placed into the mold as an insert and injection molded. After preparation, the salt core is covered inside the teeth. S3: Before the coil fixing teeth are assembled into the fixing slots on the stator core laminations, a flexible intermediate layer with a thickness of 0.15mm-0.25mm is pasted on the contact surface of the fixing slot, such as a polyimide (Kapton) film or a layer of B-grade epoxy resin glass fiber cloth. S4: Insert the coil fixing teeth into the fixing slots on the inner circle of the stator core lamination along the axial direction. S5: The stator coils are inserted into the stator winding slots, which are composed of stator core laminations and several coil fixing teeth, and fixed using an equal number of slot wedges.

[0013] S6: After the overall VPI is impregnated, hot water is circulated in the cooling oil channel to quickly dissolve and discharge the water-soluble salt core mold; the flow channel is flushed with transformer oil to remove residual moisture or particles, and a flow-pressure drop test is performed to verify the flow channel patency, thus completing the preparation of the oil-cooled air gap armature.

[0014] This invention application also provides a motor with an oil-cooled air-gap armature structure, including a stator frame, a stator shield, a drive end cover, a non-drive end cover, an oil inlet pipe, an oil outlet pipe, end leads, a rotor, and bearings. The motor stator adopts the above-mentioned oil-cooled air-gap armature structure.

[0015] Compared with the prior art, the above-described technical solutions conceived in this invention have the following technical effects: 1. The coil fixing teeth of the present invention adopt a "dovetail" or "vertical tree" structure according to the impact resistance requirements, which disperses stress. By introducing a layer of flexible medium between the non-metallic teeth and the stator core metal yoke, the point contact load of the stator yoke lamination is converted into a surface load after VPI impregnation, so that the load is evenly distributed. During impact or periodic vibration, it absorbs vibration energy, prevents wear of hard-hard contact, reduces fretting wear of coil fixing teeth, and plays a role in tolerance compensation. It significantly reduces the risk of thermal expansion mismatch between different materials and improves impact resistance.

[0016] 2. By using ceramic teeth (170-220 W / mK) or thermally conductive plastic teeth (1-10 W / mK) with certain thermal conductivity, and through the integrated molding process of the flow channel and coil fixing teeth, the problems of high thermal resistance of closed flow channels, insulation damage of open flow channels, and reduced slot fill factor caused by setting flow channels or insulation protection layers in the slot are avoided in traditional non-metallic teeth. At the same time, it has good electrical insulation performance. The integrated molding process allows for the design of various microstructures such as longitudinal microribs, transverse turbulence ribs or corrugated flow channels inside the flow channel, which enhances turbulent heat transfer at low Reynolds numbers. The heat transfer area and efficiency can be greatly improved, which is conducive to the application of second-generation high-temperature superconducting tape YBCO in motors and can further promote the improvement of power density of high-temperature superconducting air-gap armature motors.

[0017] 3. Before winding and VPI impregnation, a solid mandrel is pre-filled inside the cooling channel. This mandrel acts as a solid support during the VPI process, completely blocking resin from entering. After VPI curing, the mandrel is dissolved and drained using a specific solvent, resulting in a clean, hollow channel. This soluble mandrel solution solves the problem of narrow channels easily clogging during VPI impregnation, reducing the process complexity. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of the assembly of the "dovetail" yoke core lamination and coil fixing teeth in Embodiment 1 of the present invention; Figure 2 This is a partial structural schematic diagram of the yoke core lamination of Embodiment 1 of the present invention; Figure 3 This is a three-dimensional structural diagram of the coil fixing teeth according to Embodiment 1 of the present invention; Figure 4This is a partial structural cross-sectional view of the oil-cooled air-gap armature in the assembled state according to Embodiment 1 of the present invention; Figure 5 This is a partial structural diagram of the "vertical tree-shaped" yoke core lamination of Embodiment 2 of the present invention; Figure 6 A partial structural schematic diagram of a motor employing an oil-cooled air-gap armature in Embodiment 3 of the present invention.

[0019] The labels on the attached drawings are as follows: 1—stator core lamination, 10—fixing slot, 100—"dovetail" slot, 101—"vertical tree" slot, 2—coil fixing tooth, 20—ceramic tooth, 21—thermally conductive plastic tooth, 22—cooling oil channel, 3—stator coil, 4—slot wedge, 5—water-soluble salt core mold, 6—flexible intermediate layer, A1—outer frame, A2—inner frame, A3—non-drive end cover, A4—drive end cover, A5—outer sealing cover, A6—stator shield, A7—end lead, A8—oil inlet pipe, A9—oil outlet pipe. Detailed Implementation

[0020] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0021] Example 1: Refer to the instruction manual appendix Figure 1-4 A stator oil-cooled air gap armature includes stator core laminations, coil fixing teeth, stator coils, and slot wedges.

[0022] The stator core laminations are either full-circle annular or fan-shaped, depending on the stator dimensions. The inner circle of each lamination has 96 dovetail-shaped slots, the same number as the stator slots. After lamination stacking, the axial length is 630mm. The stator coil fixing teeth are made of ceramic and sintered at high temperature. One end has a dovetail structure to match the dovetail slots of the stator laminations, thus fixing the stator coil. Unlike traditional dovetail slots, this invention changes the traditional three-plane slot to a five-plane slot, achieving stress dispersion. The assembly gap between the coil fixing teeth and the stator laminations is 0.15mm, used to fill a flexible intermediate layer. The coil fixing teeth are segmented along the axial direction, with three segments, each 210mm long. A cooling oil channel is designed in the middle of the ceramic tooth, with a channel width of 2mm and a height of 30mm. Method for fabricating oil-cooled air-gap armature according to Embodiment 1 of the invention: S1: Separately manufacture stator core laminations, stator coils, and slot wedges, and stack the stator core laminations into a whole; S2: The "dovetail" ceramic teeth are prepared by sintering process. After the sintering process is completed, the salt core is filled into the cooling oil channel and a clearance fit is used. S3: Coat the contact surface of the fixing groove with a 0.15mm thick layer of B-grade epoxy resin glass fiber cloth; S4: Insert the coil fixing teeth into the stator core lamination "dovetail" fixing slots along the axial direction; S5: The stator coils are inserted into the stator winding slots, which are composed of stator core laminations and several coil fixing teeth, and fixed using an equal number of slot wedges.

[0023] S6: After the overall VPI is impregnated, hot water is circulated in the cooling oil channel to quickly dissolve and discharge the water-soluble salt core mold; the flow channel is flushed with transformer oil to remove residual moisture or particles, and a flow-pressure drop test is performed to verify the flow channel patency, thus completing the preparation of the oil-cooled air gap armature.

[0024] The structure described in this embodiment exhibits excellent thermal conductivity in the stator coil fixing teeth, completely resolving the failure problem associated with traditional non-metallic tooth adhesive bonding. Furthermore, the ceramic material boasts high thermal conductivity and eliminates eddy current generation. By employing a flexible interlayer, this embodiment transforms rigid mechanical extrusion into distributed flexible load-bearing, effectively offsetting shear stresses caused by thermal expansion mismatch. This significantly enhances the mechanical stability of the structure under high-frequency vibration environments of the motor, completely replacing the high-risk adhesive bonding process.

[0025] Example 2: See the attached instruction manual. Figure 5This embodiment provides a stator core lamination with a "vertical tree-shaped" slot, suitable for scenarios requiring high impact resistance. The corresponding coil fixing teeth are made of thermally conductive plastic, and the assembly gap between the stator core lamination and the thermally conductive plastic teeth is 0.25mm. The multi-tooth "vertical tree-shaped" design distributes the tangential load, primarily from electromagnetic torque, and the radial load from centrifugal force in the rotating motor to multiple contact tooth surfaces, reducing the stress amplitude of a single tooth root and significantly improving the high-cycle fatigue life of the connection. Compared to single planar adhesive bonding, dovetail grooves, or straight tenon structures, it can withstand more shear loads. For HTS motors, the air gap magnetic flux density is extremely high, exceeding 2T, resulting in enormous electromagnetic forces acting on the stator teeth. For high-speed HTS motors used in aerospace, the non-metallic teeth themselves and the embedded HTS coils are also subjected to huge centrifugal forces, and the vertical tree-shaped connection is suitable for such high-load and high-speed maneuvering scenarios. By designing the inclination angle, size, and clearance of the "vertical tree-shaped" teeth, the non-metallic teeth can have a certain degree of freedom in radial thermal expansion relative to the metal yoke. This allows for the release of thermal stress caused by the difference in expansion / contraction between the stator teeth and the yoke due to heat generation during HTS motor operation, preventing cracking at the connection or damage to the teeth and greatly improving the long-term reliability of the connection. Furthermore, the multi-tooth contact surfaces fit tightly under preload (possibly through interference fit or subsequent centrifugal force), improving the overall stiffness and modal frequency of the teeth and preventing harmful resonance; the multiple contact interfaces themselves provide a certain degree of interfacial damping, helping to attenuate electromagnetic or mechanical vibrations.

[0026] Method for fabricating oil-cooled air-gap armature in Embodiment 2 of the Invention: S1: Separately manufacture stator core laminations, stator coils, and slot wedges, and stack the stator core laminations into a whole; S2: Prepare "vertical tree-shaped" thermally conductive plastic teeth; before preparation, place the water-soluble salt core mold as an insert into the mold, and after preparation, the water-soluble salt core mold is embedded in the cooling oil flow channel; S3: Before the coil fixing teeth are assembled into the fixing slots on the stator core laminations, a flexible intermediate layer with a thickness of 0.15mm-0.25mm is pasted on the contact surface of the fixing slots; S4: Insert the coil fixing teeth into the stator core lamination "vertical tree-shaped" fixing slots along the axial direction; S5: The stator coils are inserted into the stator winding slots, which are composed of stator core laminations and several coil fixing teeth, and fixed using an equal number of slot wedges.

[0027] S6: After the overall VPI is impregnated, hot water is circulated in the cooling oil channel to quickly dissolve and discharge the water-soluble salt core mold; the flow channel is flushed with transformer oil to remove residual moisture or particles, and a flow-pressure drop test is performed to verify the flow channel patency, thus completing the preparation of the oil-cooled air gap armature.

[0028] Example 3: See the attached instruction manual. Figure 6 This embodiment provides a motor structure using an oil-cooled air-gap armature, including an outer frame A1, an inner frame A2, a non-drive end cover A3, a drive end cover A4, an outer sealing cover A5, a stator shield A6, end leads A7, an oil inlet pipe A8, and an oil outlet pipe A9. The oil-cooled air-gap armature of embodiment 1 or 2 is radially assembled with the inner frame A2 and the outer frame A1, forming a closed oil-cooled cavity through the non-drive end cover A3, the drive end cover A4, the outer sealing cover A5, and the stator shield A6. The oil-cooled air-gap armature is located within the cavity. The outer sealing cover A5 has end leads A7 on its wall surface, with sealed connections. End leads A7 are connected to the stator coil 3, forming an electrical connection. The non-drive end cover A3 and the drive end cover A4 respectively fix the oil inlet pipe A8 and the oil outlet pipe A9, realizing oil inlet and outlet.

[0029] In the oil-cooled air-gap armature of this invention, under rated operating conditions, the stator coil 3 generates heat due to losses. This heat is transferred to the coil fixing teeth 2 via heat conduction, and is ultimately carried away by the cooling oil in the cooling oil channels on the coil fixing teeth 2. The use of ceramic or thermally conductive plastic teeth with a certain thermal conductivity reduces thermal resistance during heat transfer and improves heat dissipation efficiency. The closed flow channel design reduces damage during coil insulation assembly and improves insulation reliability. The flow channel and coil fixing teeth are integrally molded, integrating functions and improving slot fill factor. Furthermore, the flow channel can be designed with various microstructures such as longitudinal microribs, transverse turbulence ribs, or corrugated flow channels to enhance heat transfer intensity. In addition, the use of a water-soluble salt core mold within the flow channel solves the problem of VPI varnish blockage in narrow flow channels, and the process is simple, ensuring unobstructed oil cooling channels. This invention's technical solution contributes to further increasing electromagnetic load and is highly beneficial for achieving higher power and torque densities in HTS motors, further expanding the absolute advantages of HTS motors.

[0030] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the various embodiments of the present invention.

Claims

1. An oil-cooled air-gap armature, comprising stator core laminations (1), coil fixing teeth (2), stator coils (3), and slot wedges (4); characterized in that, The stator core lamination (1) has a fixing groove (10) punched in its inner circle. The coil fixing teeth (2) are installed in the fixing groove (10) of the stacked stator core lamination (1) along the circumferential direction of the stator core lamination (1). The stator coil (3) is installed in the stator winding groove composed of the stator core lamination (1) and several coil fixing teeth (2), and is fixed by the slot wedge (4).

2. The oil-cooled air-gap armature according to claim 1, characterized in that, The stator core lamination (1) is a round ring lamination or a fan-shaped lamination, and the inner circle of the stator core lamination (1) is punched with a fixing groove (10) of "dovetail type" (100) or "vertical tree type" (101) structure.

3. The oil-cooled air-gap armature according to claim 1, characterized in that, The coil fixing teeth (2) are ceramic teeth (20) or thermally conductive plastic teeth (21), and the number of coil fixing teeth (2) is the same as the number of motor stator slots.

4. The oil-cooled air-gap armature according to claim 1, characterized in that, Cooling oil channels (22) are provided inside the coil fixing teeth (2).

5. A method for preparing an oil-cooled air-gap armature, characterized in that, The method for preparing the oil-cooled air-gap armature structure as described in any one of claims 1-4 includes: S1: Stator core laminations (1), stator coils (3) and slot wedges (4) are manufactured separately, and the stator core laminations (1) are stacked into a whole; S2: Select the type of coil fixing teeth (2) according to the impact resistance requirements of different application scenarios, and select the corresponding preparation process according to the type of coil fixing teeth (2); S3: Before assembling the coil fixing teeth (2) into the fixing groove (10) of the stator core lamination (1), attach a flexible intermediate layer (6) with a thickness of 0.15mm-0.25mm to the groove contact surface. S4: The coil fixing teeth (2) are sequentially inserted into the fixing slots (10) on the stator core lamination (1) along the axial direction. S5: The stator coil (3) is inserted into the stator winding slots composed of the stator core lamination (1) and several coil fixing teeth (2) one by one, and fixed by using the same number of slot wedges (4); S6: After the overall VPI is impregnated, hot water is circulated into the cooling oil channel (22) to quickly dissolve and discharge the water-soluble salt core mold (5); the flow channel is flushed with transformer oil to remove residual moisture or particles, and the flow-pressure drop test is performed to verify the flow channel patency, thus completing the preparation of the oil-cooled air gap armature.

6. A motor employing an oil-cooled air-gap armature structure, comprising a stator frame, a stator shield, a drive end cover, a non-drive end cover, an oil inlet pipe, an oil outlet pipe, end leads, a rotor, and bearings; characterized in that, The motor includes, as claimed in claim 1 4. The oil-cooled air-gap armature as described in any one of the following.

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