Hollow conductor in an electric machine
By using hollow conductors to form continuous wave windings in the motor stator, efficient cooling fluid circulation is achieved, solving the problem of stator winding overheating and improving the motor's cooling efficiency and high power output capability.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- SCANIA CV AB
- Filing Date
- 2024-11-11
- Publication Date
- 2026-06-05
AI Technical Summary
The poor cooling characteristics of the stator windings of existing motors lead to overheating, affecting motor efficiency and lifespan, and making it difficult to achieve high power and continuous torque within a limited mechanical size.
A continuous wave winding is formed using hollow conductors. The two ends of the winding are submerged in a cooling chamber by cooling fluid, which flows through the holes in the hollow conductor for efficient cooling. The cooling fluid circulates between different sections of the winding to equalize the temperature.
It improves the motor's cooling efficiency, reduces winding temperature, extends lifespan, and enhances the motor's high power output and torque performance.
Smart Images
Figure CN122162285A_ABST
Abstract
Description
Technical Field
[0001] This document discloses a hollow conductor that forms a continuous wave winding of a stator according to the appended patent claims. This document further relates to an electric motor and a vehicle comprising the electric motor. Background Technology
[0002] Modern electric motors, such as electric motors, generators, and / or alternators, are typically based on the concept of a rotor with magnets, which is coaxially arranged to rotate within a stator to achieve the desired performance.
[0003] The stator contains windings made of conductive coils of wire. When alternating current is supplied to the windings, the magnets contained in the rotor are affected, causing the rotor to begin to rotate.
[0004] Heat is generated due to resistance in the windings (e.g., hairpin windings / continuous windings). When motors are used in vehicle propulsion systems and similar industrial applications, high power is typically desired within a limited mechanical size.
[0005] For the electrification of commercial vehicles, achieving good continuous motor performance to ensure sustained torque and power delivery under varying conditions over extended periods is crucial to meeting starting requirements. To prevent overheating, cooling fluid can be applied via cooling channels in the stator.
[0006] However, existing motors of the aforementioned types exhibit poor winding and stator cooling characteristics. Stator overheating reduces motor efficiency and affects the performance and lifespan of the components involved. For example, the insulation layer may melt.
[0007] The goal is to find a solution that addresses at least some of the aforementioned problems and improves motor cooling, thereby enhancing high continuous power capability and torque. Summary of the Invention
[0008] Therefore, the object of the present invention is to solve at least some of the above-mentioned problems and to improve the cooling capacity of the stator windings in an electric motor.
[0009] According to a first aspect of the invention, this object is achieved by forming hollow conductors in a continuous wave winding of the stator. The stator and rotor are combined to form an electric motor. The continuous wave winding is formed by uniformly distributing the hollow conductors around the periphery of the stator with a certain winding pattern, thereby forming multiple parallel paths between the axial ends of the winding.
[0010] The first axial end of the winding is submerged in a first cooling chamber by cooling fluid, and the second axial end of the winding is submerged in a second cooling chamber by cooling fluid. The first axial end of the winding includes a first set of holes, and the second axial end of the winding includes a second set of holes. Thus, when the pump acts on the cooling fluid, the cooling fluid is allowed to flow from the first cooling chamber through the first set of holes through the corresponding section of the hollow conductor, and through the second set of holes to the second cooling chamber.
[0011] Thanks to the provided solution, cooling fluid is allowed to flow from the first cooling chamber through the hollow conductor to the second cooling chamber, thereby efficiently reducing the temperature of the continuous stator windings. The submerged end windings further improve cooling efficiency.
[0012] Efficient cooling of the conductors increases the load capacity of the motor; the motor can handle increased electrical loads, i.e., higher power output, without overheating.
[0013] The resistance of a conductor depends on temperature. By lowering the temperature, the resistance also decreases, thereby improving the performance of the motor by outputting more power or using less energy to achieve the same output.
[0014] Lower temperatures also reduce the thermal expansion and stress on the windings and insulation, thus preventing deformation and structural failure over time. More efficient cooling through hollow conductors will also extend the life of the stator windings, as the aging rate of the insulation depends on temperature; that is, higher temperatures accelerate aging.
[0015] Optionally, the first set of holes in the first axial end and the second set of holes in the second axial end can be distributed to allow the hotter section of the hollow conductor to be adjacent to the colder section of the hollow conductor.
[0016] The term "proximity" should be interpreted as "within a finite physical distance." The terms "hotter section" and "cooler section" refer to the temperature of their respective sections relative to each other, i.e., the temperature of the hotter section is higher than that of the cooler section. However, the hotter section is not necessarily the hottest section of the winding, and the cooler section is not necessarily the coldest section, but this situation will bring the greatest benefit in terms of winding temperature balance.
[0017] The goal is to reduce the temperature of hot spots in the system, that is, to equalize the temperature between different sections of the winding.
[0018] Regarding the proximity of sections, optimal cooling is achieved when hotter and colder sections are in direct physical contact (e.g., within the same stator slot). However, temperature equilibrium is also achieved when hotter and colder sections are positioned at a certain distance from each other; or, for example, when they are radially separated by two steps within the same stator slot, a beneficial cooling effect is also achieved on the hotter section. The cooler conductor also cools the stator core, thereby reducing the hot spot temperature of the hotter conductor.
[0019] This improves the temperature balance across different sections of the winding. Due to efficient cooling, the temperature of hot spots in the winding is effectively reduced.
[0020] Optionally, the first set of holes in the first axial end and the second set of holes in the second axial end may be distributed such that cooling fluid entering the first set of holes in the first axial end flows at least three times in the continuous wave winding between the axial ends before entering the second cooling chamber via the second set of holes.
[0021] The advantage is that the cooling efficiency of the cooling fluid is maximized, or at least significantly improved.
[0022] Optionally, the first set of holes may include one hole disposed in the first axial end for every three turns of the continuous wave winding. Similarly, the second set of holes may include one hole disposed in the second axial end for every three turns of the continuous wave winding.
[0023] This provides a uniform distribution of cooling fluid, thereby improving the heat distribution of the conductor and reducing the temperature of the conductor's hot spots.
[0024] Optionally, the flow of cooling fluid through the hollow conductor can be reversible, such that cooling fluid is drawn from the second cooling chamber via the second set of holes, passes through the hollow conductor, and reaches the first cooling chamber via the first set of holes.
[0025] This provides enhanced heat exchange.
[0026] According to a second aspect of the invention, this object is achieved by an electric motor. The electric motor includes a stator and a rotor. The stator is configured to hold a continuous wave winding. The rotor is configured to run coaxially within the stator. According to a first aspect, the electric motor further includes hollow conductors forming the continuous wave winding.
[0027] Improved cooling reduces heat generation, resulting in a smaller gap between peak and continuous performance, which enables higher continuous power density and torque in the motor.
[0028] According to a third aspect of the invention, this objective is achieved by a means of transportation. The means of transportation includes an electric motor according to a second aspect of the invention.
[0029] Other advantages and additional novel features will become apparent from the following detailed description. Attached Figure Description
[0030] Embodiments of the present invention will now be described in further detail with reference to the accompanying drawings, in which: Figure 1A An end section of a motor according to one embodiment is shown.
[0031] Figure 1B A cross-section AA of an electric motor according to one embodiment is shown.
[0032] Figure 2 The stator and windings of an electric motor according to one embodiment are shown, as well as the cross-section BB of the conductor forming the windings.
[0033] Figure 3 A stator winding of an electric motor according to one embodiment is shown, wherein the stator winding includes holes for cooling fluid to pass through a hollow conductor.
[0034] Figure 4 A stator winding of an electric motor according to one embodiment is shown, wherein the stator winding includes holes for cooling fluid to pass through a hollow conductor.
[0035] Figure 5 A side view of a cross-section of an electric motor according to one embodiment is shown.
[0036] Figure 6 A vehicle according to one embodiment is shown, the vehicle comprising a motor having stator windings formed of hollow conductors. Detailed Implementation
[0037] The embodiments of the invention described herein are defined as hollow conductors, electric motors, and vehicles comprising electric motors, which can be practiced in the embodiments described below. However, these embodiments can be illustrated and implemented in many different forms and are not limited to the examples set forth herein; rather, these illustrative examples of embodiments are provided to make this disclosure thorough and complete.
[0038] Other objects and features may become apparent from the following detailed description taken in conjunction with the accompanying drawings. However, it should be understood that the drawings are designed for illustrative purposes only and are not intended to define limitations on the embodiments disclosed herein, with reference to the appended claims. Furthermore, the drawings are not necessarily drawn to scale, and unless otherwise indicated, are intended only to conceptually illustrate the structures and processes described herein.
[0039] Figure 1A An example of an end section of a motor 100 as seen from an axial view is shown. The motor 100 includes a rotor 110 and a stator 120. The stator 120 encloses the coaxially arranged rotor 110.
[0040] The rotor 110 is rotatably mounted inside the stator 120, wherein there is an air gap between the rotor surface and the stator 120, and a radial clearance between the rotor 110 and the stator 120. Therefore, the rotor 110 forms the rotating part of the motor 100, while the stator 120 forms its stationary part.
[0041] The rotor 110 may include multiple magnets that form a magnetic field. When the motor 100 operates in generator mode, the magnetic field generates an electric current due to electromagnetic induction as the rotor 110 rotates. Alternatively, the rotor 110 may include windings. When a current is generated in the rotor windings by a power source rather than a magnet in the rotor 110, the windings form a magnetic field. This can be referred to as a field-wound rotor.
[0042] The motor 100 can be configured to convert electrical energy into mechanical energy, thereby operating as an electric motor. The motor 100 may also, or alternatively, include a generator having the same configuration as the electric motor but operating with the opposite power flow, converting mechanical energy into electrical energy.
[0043] The motor 100 can be included in the vehicle and configured to propel the vehicle as an electric motor when driven. Conversely, when the vehicle is traveling downhill and / or braking, the motor 100 can operate as a generator, producing electricity that can be stored in a battery.
[0044] The stator 120 includes a plurality of radially extending stator slots 130 arranged radially around a common central axis of the stator 120, wherein the stator slots 130 are equidistant from each other. In the illustrated embodiment, there are eight stator slots, but this is merely a non-limiting example. The portion of the stator 120 located between the stator slots 130 may be referred to as a tooth. The stator slots 130 contain windings, for example in the form of hairpin windings, which are sometimes referred to as molded coils. Other possible alternatives may be so-called positive toroidal windings and / or concentrated windings.
[0045] In different embodiments, stator slot 130 can be open, closed, or semi-closed. An open stator slot 130 can have substantially flat walls extending to a radially inner defining surface of the stator 120. In other embodiments, the walls of the open stator slot 130 can have other configurations, such as convex / concave profiles, elliptical profiles, etc. Open stator slot 130 is easy to implement. With open stator slot 130, winding assembly and repair are easy.
[0046] The stator slot 130 is configured to house a hollow conductor forming a continuous wave winding in the axial direction of the motor 100. Figure 1B The cross-section AA of motor 100 is shown.
[0047] Figure 2 The stator 120 and winding 210 of an electric motor 100 according to one embodiment are shown, as well as the cross-section BB of the hollow conductor 200 forming the winding 210.
[0048] The hollow conductor 200 is hollow to allow cooling fluid to pass through, thereby cooling the conductor 200. The hollow conductor 200 can be made of copper, a copper alloy, or another metal or metal alloy that has similar physical properties to copper in terms of thermal conductivity. In some embodiments, the hollow cross-section of the conductor 200 can be circular or substantially circular, but in alternative embodiments, it can have another cross-sectional shape such as square, octagonal, hexagonal, etc. The outer diameter of the conductor 200 can be circular, but it can have another cross-sectional shape such as square, octagonal, hexagonal, etc.
[0049] The ratio between the outer and inner diameters of the hollow conductor 200 can be selected to avoid excessive pressure drop as the cooling fluid passes through the windings, while still allowing sufficient thermal conductivity. This ratio can be selected based on several factors, such as the material of the conductor 200, the length of the stator 120, the number of layers in the conductor section forming the continuous wave winding of the stator 120, the outer diameter of the conductor 200, the physical properties of the selected cooling fluid, and the pump's capacity. A non-limiting example of this ratio could be, for example, about 1 / 2 to 1 / 3.
[0050] Cooling fluids can be, for example, oil, water, or a mixture of water and ethylene glycol. Oil offers several advantages over water as a cooling fluid. Oil has a higher boiling point than water and can be used to cool motors 100°C, even though water cooling can exceed 100°C under pressure. Oil is also an electrical insulator, so accidental leakage of the cooling fluid poses no danger except for cooling interruptions / interference.
[0051] Figure 3The stator winding 210 is shown prior to its installation into the stator slot 130 of the stator 120. The stator winding 210 includes a first set of holes 310 in a first axial end 301 and a second set of holes 320 in a second axial end 302.
[0052] Holes 310 and 320 can be drilled in the respective axial ends 301 and 302. Therefore, the diameters of holes 310 and 320 are typically circular. However, in alternative embodiments, holes 310 and 320 can be square, rectangular, hexagonal, octagonal, etc. The diameters of holes 310 and 320 can, for example, be approximately similar to the inner diameter of the hollow conductor 200, or may be slightly larger (e.g., 10%-30%) to avoid or at least reduce voltage drop.
[0053] During the operation of motor 100, the stator winding 210 applies pressure to the stator. In 120, cooling fluid is immersed in a first cavity surrounding the first end winding. Cooling fluid is allowed to enter the hollow conductor 200 through a first set of holes 310, pass through the stator winding 210, and exit into a second cavity through a second set of holes 320 in the second axial end 302, in which the second end winding is cooled by the cooling fluid.
[0054] Figure 4 The stator winding 210, and especially the distribution of its axially extending sections, are also schematically shown, along with the distribution of the first set of holes 310 and the second set of holes 320. These distributions of the corresponding sets of holes 310 and 320 can be arranged to allow the hotter section t3 of the hollow conductor 200 to be adjacent to the colder section t1 of the hollow conductor 200.
[0055] Figure 4 The vertical extension of the stator winding 210 will be distributed in the stator slot 130 in the circumferential direction of the stator 120.
[0056] The hollow conductor 200 is formed into a continuous wave winding 210 by uniformly distributing it around the stator periphery in the stator slots 130 with a certain winding pattern, thereby forming multiple parallel paths between the axial ends 301 and 302 of the winding 210. The wave winding 210 can be distributed in several layers in each stator slot 130, for example, 5-10 layers or 6-8 layers.
[0057] The cooler section t1 of the hollow conductor 200 will thus absorb at least some heat from the hotter section t3. In some embodiments, the flow direction of the cooling fluid in the cooler section t1 and the hotter section t3 of the hollow conductor 200 can be the same, i.e., they can form a co-current heat exchange. In other embodiments, the flow direction of the cooling fluid in the cooler section t1 and the hotter section t3 of the hollow conductor 200 can be opposite to each other, i.e., they can form a counter-current heat exchanger. The counter-current design is the most efficient because it can transfer the most heat per unit mass of heat (transfer) medium due to the higher average temperature difference along any unit length.
[0058] Figure 5 An electric motor 100 according to one embodiment is schematically shown. A first end 301 of the stator winding 210 is submerged in cooling fluid within a first cooling chamber 510. The first cooling chamber 510 may be formed from a stator housing. The first end 301 of the winding 210 is thus immersed in the cooling fluid to achieve efficient cooling of the first end 301. In addition to efficient cooling of the respective end winding, the immersion / submersion of the end winding also allows the cooling fluid to easily flow into the holes 310, 320 in the end winding.
[0059] An integrated sealing element can be applied to form a seal, thereby preventing coolant leakage into the air gap between the stator 120 and the rotor 110. Allowing coolant into the air gap could increase friction between the rotor 110 and the stator 120, potentially affecting the efficiency of the motor 100. The integrated sealing element 310 may comprise, for example, rubber, silicone, nitrile, thermoplastic and / or elastomer materials, or similar materials. Excess coolant can be drained from the first cooling chamber 510 via orifices and transported to a reservoir.
[0060] On opposite sides of the stator 120 in the axial direction, the second end 302 of the stator winding 210 is submerged in cooling fluid in the second cooling chamber 520. The second cooling chamber 520 may also be formed from the stator housing. The second end 302 of the winding 210 is thus immersed in cooling fluid to achieve efficient cooling of it.
[0061] During certain load conditions of the motor 100, the corresponding end windings 301 and 302 may be exposed to most, or even the majority, of stator losses. Efficient cooling can be achieved by immersing the end windings 301 and 302 in a cooling fluid.
[0062] The motor 100 may also include a pump 530. The pump 530 may be arranged to continuously circulate cooling fluid from the first cooling chamber 510 through a first set of holes 310 at the first axial end 301 of the winding 210, through the hollow conductor 200, through a second set of holes 320 in the second axial end of the winding 210 to the second cooling chamber 520.
[0063] The cooling fluid can then be transported to a heat exchanger 540 or similar arrangement, where the heat from the heating fluid is dissipated before the cooling fluid is transported to the first cooling chamber 510.
[0064] In some embodiments, the flow direction of the pump 530 can be reversed. This allows cooling fluid to be drawn from the second cooling chamber 520 via the second set of holes 320, passing through the hollow conductor 200 and reaching the first cooling chamber 510 via the first set of holes 310.
[0065] The cooling fluid will immediately reach its lowest temperature after passing through heat exchanger 540 and its highest temperature after passing through winding 210. If the circulation continues in the same direction; for example, from the first cooling chamber 510 to the second cooling chamber 520, the first axial end 301 of winding 210 will be cooled more efficiently than the second axial end 302 of winding 210, because the lower temperature of the cooling fluid in the first cooling chamber 510 will cool the first axial end 301 more efficiently. By occasionally reversing the flow direction of the cooling fluid through motor 100, the temperature of hot spots in winding 210 will be reduced more efficiently due to a more uniform heat distribution.
[0066] Figure 6 A vehicle 600 including an electric motor 100 is shown, the electric motor having a rotor 110, a stator 120 and a hollow conductor 200 forming a continuous wave winding 210 according to any of the above embodiments.
[0067] In different embodiments, the vehicle 600 may be controlled by a driver or autonomously controlled by an unmanned vehicle. The vehicle 600 may include, in a broad sense, means of transportation such as trucks, cars, motorcycles, trailers, buses, bicycles, trains, trams, airplanes, ships, unmanned underwater vehicles, unmanned aircraft, humanoid service robots, spacecraft, or other similar manned or unmanned transport devices that operate on wheels, tracks, air, water, or similar media.
[0068] The vehicle 600 can be an electric vehicle, a hybrid vehicle, a plug-in hybrid vehicle, etc., wherein the motor 100 is configured to propel the vehicle 600 and / or to generate electrical energy for use by the vehicle 600, depending on the mode: electric motor mode or generator mode.
[0069] As used herein, the term “and / or” includes any and all combinations of one or more of the associated listed items. As used herein, unless expressly stated otherwise, the term “or” should be interpreted as mathematical OR, i.e., as inclusive disjunction, not as mathematical XOR. Additionally, unless expressly stated otherwise, the singular forms “a / an” and “described” should be interpreted as “at least one / a,” and thus may also include multiple entities of the same class. It will be further understood that the terms “includes,” “comprises,” “including,” and / or “comprising” specify the presence of the stated features, actions, integers, steps, operations, elements, and / or components, but do not exclude the presence or addition of one or more other features, actions, integers, steps, operations, elements, components, and / or groups thereof. The fact that certain measures are stated in dissimilar dependent claims does not imply that combinations of these measures cannot be advantageously used.
Claims
1. A hollow conductor (200) forming a continuous wave winding (210) of a stator (120), wherein the stator (120) and a rotor (110) are combined to form a motor (100); and wherein the continuous wave winding (210) is formed by uniformly distributing the hollow conductor (200) around the periphery of the stator with a certain winding pattern, thereby forming multiple parallel paths between the axial ends (301, 302) of the winding (210); wherein the first axial end (301) of the winding (210) is submerged in a first cooling chamber (510) by a cooling fluid, and the second axial end (302) of the winding (210) is submerged in a second cooling chamber (520) by a cooling fluid; And among them The first axial end (301) of the winding (210) includes a first set of holes (310); and The second axial end (302) of the winding (210) includes a second set of holes (320). Thus, when the pump (530) acts on the cooling fluid, the cooling fluid is allowed to flow from the first cooling chamber (510) through the first set of holes (310) through the corresponding section of the hollow conductor (210) and through the second set of holes (320) to the second cooling chamber (520).
2. The hollow conductor (200) according to claim 1, wherein the first set of holes (310) in the first axial end (301) and the second set of holes (320) in the second axial end (302) are distributed to allow the hotter section (t3) of the hollow conductor (200) to be adjacent to the colder section (t1) of the hollow conductor (200).
3. The hollow conductor (200) according to any one of the preceding claims, wherein the first set of holes (310) in the first axial end (301) and the second set of holes (320) in the second axial end (302) are distributed to allow cooling fluid entering the first set of holes (310) in the first axial end (301) to flow at least three times in the continuous wave winding (210) between the axial ends (301, 302) before entering the second cooling chamber (520) via the second set of holes (320).
4. The hollow conductor (200) according to any one of the preceding claims, wherein the first set of holes (310) comprises a hole provided in the first axial end (301) for every three turns of the continuous wave winding (210); and wherein the second set of holes (320) comprises a hole provided in the second axial end (302) for every three turns of the continuous wave winding (210).
5. The hollow conductor (200) according to any of the preceding claims, wherein the flow of cooling fluid through the hollow conductor (200) is reversible, such that cooling fluid is drawn from the second cooling chamber (520) through the second set of holes (320) and passes through the hollow conductor (200) through the first set of holes (310) to the first cooling chamber (510).
6. An electric motor (100) comprising: Stator (120), the stator being configured to hold a continuous wave winding (210). Rotor (110), the rotor being configured to run coaxially within the stator (120); and The hollow conductor (200) according to any one of claims 1 to 5 forms the continuous wave winding (210).
7. A vehicle (600) comprising an electric motor (100) according to claim 6.