A flywheel energy storage device that can reduce eddy current effects

Abstract

This utility model relates to the field of electrical energy storage technology and discloses a flywheel energy storage device that reduces eddy current effects. The device includes a housing, a stator core fixedly connected to the inner wall of the housing, and an upper end cover and a lower end cover fixedly connected to the upper and lower ends of the housing, respectively. Bearing seats are fixedly connected to opposite sides of the upper and lower end covers, and mechanical bearings are installed inside both bearing seats. This flywheel energy storage device, which reduces eddy current effects, solves the problem in existing technologies where the solid alloy steel material of the inductor leads to significant eddy current effects and severe heat generation. Furthermore, the performance of the permanent magnet magnetic levitation bearing in the flywheel energy storage device is greatly affected by ambient temperature. Current designs typically involve evacuating the flywheel housing to cut off the heat transfer medium. However, this design approach still faces challenges such as high basic complexity and high deployment costs.

Description

Technical Field

[0001] This utility model relates to the field of electrical energy storage technology, specifically a flywheel energy storage device that can reduce eddy current effects. Background Technology

[0002] With the continuous development and advancement of new energy technologies, energy storage technology has received widespread attention. Among existing energy storage technologies, flywheel energy storage devices have advantages such as good dynamic performance, high charge-discharge cycles, fast speed, long lifespan, and low maintenance frequency, making them increasingly popular. Flywheel energy storage devices include flywheel rotors, permanent magnet synchronous motors (PMSMs), and magnetic levitation bearing systems. Common flywheel energy storage motors typically use PMSMs and inductor motors as charging and discharging loads. PMSMs rely heavily on rare earth metals such as neodymium, terbium, and dysprosium, leading to high manufacturing costs. Inductor motors have solid rotors with slotted surfaces, forged from high-strength alloy steel. The rotors lack permanent magnets, windings, and any other additional components. During operation, they utilize the difference in air gap magnetic reluctance between the teeth and slots of the inductor (the slotted rotor). As the inductor rotates, the air gap magnetic reluctance between the rotor surface and the stator magnetic field changes periodically. According to the principle of minimum magnetic reluctance, magnetic lines of force tend to follow the path of least magnetic reluctance, i.e., the rotor teeth, inducing magnetic poles and generating an induced electromotive force in the stator armature windings. The magnetic field on the rotor is generated by a magnetic source on the stator through a designed magnetic circuit. The magnetic source on the stator is typically an excitation winding or a permanent magnet. The exceptionally simple and reliable rotor structure of the inductor motor makes it ideal for high energy density and high-voltage applications. However, the solid alloy steel material of the inductor also leads to significant eddy current effects within it, causing severe heat generation. Furthermore, the performance of the permanent magnet magnetic levitation bearings in flywheel energy storage devices is greatly affected by ambient temperature. Current designs typically involve evacuating the flywheel housing to cut off the heat transfer medium. However, this design approach presents challenges such as high foundational complexity and deployment costs, which remain difficult to resolve. Therefore, improving the heat dissipation of flywheel energy storage motors is also a crucial issue that warrants attention. Utility Model Content

[0003] To address the shortcomings of existing technologies, this invention provides a flywheel energy storage device that reduces eddy current effects. It offers the advantage of reducing flywheel heating, solving the problem that in existing technologies, the solid alloy steel material of the inductor also leads to significant eddy current effects and severe heating. Furthermore, the performance of the permanent magnet magnetic levitation bearing in the flywheel energy storage device is greatly affected by ambient temperature. Current designs typically involve evacuating the flywheel housing to cut off the heat transfer medium. However, this design approach still presents challenges such as high foundational complexity and high deployment costs.

[0004] The technical solution of this utility model to solve the above-mentioned technical problems is as follows: A flywheel energy storage device that can reduce eddy current effect includes a housing, a stator core fixedly connected to the inner wall of the housing, an upper end cover and a lower end cover fixedly connected to the upper and lower ends of the housing respectively, a bearing seat fixedly connected to the opposite side of the upper end cover and the lower end cover, a mechanical bearing is provided inside the two bearing seats, and the two mechanical bearings are rotatably connected to the shaft. A flywheel is fixedly connected to the outside of the shaft. The flywheel is a cylinder with a T-shaped vertical cross section. A rotor core is fixedly connected to the outside of the lower cylinder of the flywheel.

[0005] The beneficial effects of this utility model are: 1. This flywheel energy storage device, which reduces eddy current effects, designs the flywheel as a cylindrical structure with a T-shaped vertical cross section, and fixes the rotor core to the outside of the lower cylinder, forming a stacked rotor core. This effectively optimizes the mechanical structure and magnetic circuit distribution of the rotor, reduces the generation of eddy current effects, thereby reducing the heat generation phenomenon during flywheel operation and improving energy conversion efficiency.

[0006] 2. This flywheel energy storage device, which reduces eddy current effects, achieves non-contact suspension support of the flywheel by setting a magnetic levitation flange ring and a permanent magnet bearing on the top of the lower end cover, which cooperates with the second annular groove at the bottom of the flywheel. This reduces mechanical friction and wear, further reduces temperature rise, and extends the service life of the device.

[0007] Based on the above technical solution, the present invention can be further improved as follows.

[0008] Furthermore, a magnetic levitation flange ring is provided on the top of the lower end cover, and a first annular groove is provided on the top of the magnetic levitation flange ring. A permanent magnet bearing is embedded in the annular groove. A second annular groove adapted to the permanent magnet bearing is provided on the bottom of the flywheel, and the upper half of the permanent magnet bearing is embedded in the second annular groove.

[0009] The beneficial effect of adopting the above-mentioned further solution is that, through the combined design of the magnetic levitation flange ring and the permanent magnet bearing, not only is stable radial and axial support provided, but also the friction loss of traditional mechanical bearings is reduced by using magnetic levitation technology, thereby significantly reducing the heat generation during operation.

[0010] Furthermore, a central slot is provided on each of the two bearing housings on opposite sides, and the two mechanical bearings are respectively embedded in the two central slots.

[0011] The beneficial effect of adopting the above-mentioned further solution is that by opening a central slot on the opposite side of the bearing housing and embedding a mechanical bearing, the positioning accuracy and operational stability of the bearing are enhanced, and the additional energy loss and heat generation caused by vibration and misalignment are reduced.

[0012] Furthermore, sealing rings are provided at the interfaces between the housing and the upper and lower end covers.

[0013] The beneficial effect of adopting the above-mentioned further solution is that by setting a sealing ring at the interface between the housing and the upper and lower end covers, the intrusion of external impurities and moisture is effectively prevented, ensuring the stability of the internal environment of the device and facilitating heat dissipation and temperature control.

[0014] Furthermore, the outer side of the rotor core is provided with a plurality of toothed slots arranged in a circular array, the number of which is a multiple of the number of rotor pole pairs.

[0015] The beneficial effect of adopting the above-mentioned further scheme is that by setting a number of slots on the outside of the rotor core that are multiples of the number of rotor pole pairs, the magnetic field distribution is optimized, the eddy current loss and heat generation caused by magnetic reluctance changes are reduced, and the operating efficiency of the motor is improved.

[0016] Furthermore, an excitation winding located above the stator core is fixedly connected to the inner wall of the housing. The stator core has several through holes arranged in a ring array, and an armature winding passes through each of the through holes.

[0017] The beneficial effect of adopting the above-mentioned further scheme is that by setting the excitation winding on the inner wall of the housing and opening through holes in the stator core to pass through the armature winding, efficient electromagnetic energy conversion is achieved. At the same time, the reasonable winding layout reduces copper loss and iron loss, further reducing the temperature rise of the device.

[0018] Furthermore, both the upper and lower end covers are ferromagnetic end covers, the housing is a ferromagnetic housing, the flywheel is a ferromagnetic wheel, and the bearing seat is a non-ferromagnetic seat.

[0019] The beneficial effects of adopting the above-mentioned further solutions are that by using a combination of ferromagnetic and non-ferromagnetic materials, the magnetic circuit conduction and shielding effects are optimized, the eddy current heating caused by stray magnetic fields is reduced, and the interference of magnetic fields on the bearing system is avoided, thereby improving the system's stability and heat dissipation performance. Attached Figure Description

[0020] Figure 1 This is a cross-sectional view of the structure of this utility model; Figure 2 This is a schematic diagram of the connection structure between the flywheel and the rotor core of this utility model; Figure 3 This is a schematic diagram of the rotor core structure of this utility model; Figure 4 This is a schematic diagram of the connection structure between the stator core and the armature winding of this utility model; Figure 5 This is the main magnetic flux path diagram provided in this utility model; In the diagram: 1. Flywheel; 2. Housing; 301. Upper end cover; 302. Lower end cover; 4. Bearing housing; 5. Mechanical bearing; 6. Magnetic levitation flange ring; 7. Permanent magnet bearing; 8. Excitation winding; 9. Stator core; 10. Rotor core; 11. Armature winding; 12. Shaft; 13. Sealing ring. Detailed Implementation

[0021] The technical solutions of the present utility model will be clearly and completely described below with reference to the accompanying drawings of the embodiments. Obviously, the described embodiments are only some embodiments of the present utility model, and not all embodiments. Based on the embodiments of the present utility model, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the protection scope of the present utility model.

[0022] Example 1, by Figure 1-4This invention discloses a flywheel energy storage device that reduces eddy current effects. The device includes a housing 2 made of Q235 steel. A stator core 9 is fixedly connected to the inner wall of the housing 2. An excitation winding 8, located above the stator core 9, is also fixedly connected to the inner wall of the housing 2. The stator core 9 has several through holes arranged in a ring array, and armature windings 11 are longitudinally inserted into each of these through holes. The levitation force generated by the excitation current produced by the flywheel stator excitation winding 11 can offset part of the weight of the rotor core 10. An upper end cover 301 and a lower end cover 301 are fixedly connected to the upper and lower ends of the housing 2, respectively. End cap 302, upper end cap 301, and lower end cap 302 are all Q235 steel end caps. Sealing rings 13 are provided at the interfaces between the housing 2 and the upper and lower end caps 301 and 302. Bearing seats 4, made of 304 stainless steel, are fixedly connected to opposite sides of the upper and lower end caps 301 and 302. Mechanical bearings 5 ​​are installed inside each of the two bearing seats 4. Central slots are opened on opposite sides of each of the two bearing seats 4, and the two mechanical bearings 5 ​​are respectively embedded in the two central slots. A magnetic levitation flange ring 6 is provided on the top of the lower end cap 302. The flywheel 1 has a first annular groove, in which a permanent magnet bearing 7 is embedded. The bottom of the flywheel 1 has a second annular groove adapted to the permanent magnet bearing 7, with the upper half of the permanent magnet bearing 7 embedded in the second annular groove, forming an axial permanent magnet repulsive magnetic levitation bearing. The axial permanent magnet repulsive magnetic levitation bearing of the flywheel 1 generates levitation force due to the repulsion between the like poles of the upper and lower permanent magnets, thus forming a levitation gap to support the weight of the flywheel 1. The flywheel and the magnetic levitation flange ring 6 form an air gap due to magnetic force, supporting the flywheel's levitation and reducing friction, thereby reducing the axial load on the mechanical bearing. Both mechanical bearings 5 ​​are internally connected to the rotating shaft 1. 2. Rotary connection: An air gap is left between the flywheel shaft 12 and the mechanical bearing 5. The flywheel 1 is fixedly connected to the outside of the shaft 12. The flywheel shaft 12 and the flywheel 1 are connected by an interference fit. The flywheel 1 is a 40Cr steel flywheel. The flywheel 1 is a cylinder with a T-shaped vertical cross section. The rotor core 10 is fixedly connected to the outside of the lower cylinder of the flywheel 1. The flywheel 1 and the rotor core 10 together form a stacked rotor core. The rotor core 10 is made of high-strength silicon steel sheets. The outer side of the rotor core 10 is provided with several toothed slots arranged in a circular array. The number of toothed slots is a multiple of the number of rotor pole pairs.

[0023] In this embodiment, during the energy storage standby period, the permanent magnet bearing 7 provides an axial upward levitation force to the flywheel 1 to partially or completely offset the gravity of the flywheel 1, thereby reducing the load borne by the mechanical bearing 5. When the excitation winding 8 is not energized, there is no magnetic flux in the stator core 9, flywheel 1, and rotor core 10. Therefore, the motor has no no-load standby loss, thereby improving the energy conversion efficiency of the motor.

[0024] During charging and discharging, the main magnetic flux path of the motor is: flywheel 1 → rotor core → main air gap → stator core → housing → upper end cover → axial air gap → flywheel. The magnetic levitation flange ring 6 is made of non-ferromagnetic material, so the magnetic flux generated by the excitation winding 8 will hardly pass through the axial repulsive magnetic levitation flange ring 6, that is, it will not affect the stability of the axial levitation force provided by the permanent magnet bearing 7 on the flywheel rotor. This allows the axial upward levitation force provided by the permanent magnet bearing 7 to partially or completely offset the weight of the flywheel rotor core, still achieving the effect of unloading the mechanical bearing 5 and reducing bearing wear.

[0025] The magnetic field generated on the excitation coil is reused, serving both to counteract the gravity of the flywheel 1 as a permanent magnet bearing 7 and to excite the rotor core 10. The excitation current is adjustable; when the flywheel 1 experiences upward or downward displacement due to precession, the magnitude of the excitation current can be varied according to the operating conditions, ensuring that the mechanical bearing 5 is almost unaffected by axial force. During flywheel standby, the excitation coil current can be reduced or disconnected, minimizing standby losses. Compared to induction flywheel energy storage motors with directly slotted alloy steel flywheels 1, the rotor core 10 is made of high-strength silicon steel sheets, with a slotted outer contour, resulting in lower operating losses, higher system efficiency, and lower rotor heat generation. Furthermore, the motor experiences no electromagnetic losses during energy storage standby, leading to a high energy conversion rate. The flywheel 1 experiences stable levitation force throughout the entire charging and discharging process, reducing bearing load and losses and extending bearing life. The rotor core 10, made of high-strength silicon steel sheets, effectively reduces the temperature rise of various motor components. The motor has a simple, compact, and low-cost overall structure, good rotor dynamics characteristics, and is easy to manufacture, making it very suitable for flywheel energy storage applications.

[0026] This application achieves the goal of reducing flywheel heating, solving the problem that in existing technologies, the solid alloy steel material of the inductor also leads to a large eddy current effect inside, causing severe heating. Furthermore, the performance of the permanent magnet magnetic levitation bearing in the flywheel energy storage device is greatly affected by ambient temperature. Current designs typically involve evacuating the flywheel housing to cut off the heat transfer medium. However, the high fundamental complexity and deployment cost of this design remain unresolved.

[0027] It should be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0028] Although embodiments of the present invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the present invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A flywheel energy storage device that reduces eddy current effects, comprising a housing (2), a stator core (9) fixedly connected to the inner wall of the housing (2), an upper end cover (301) and a lower end cover (302) fixedly connected to the upper and lower ends of the housing (2), bearing seats (4) fixedly connected to opposite sides of the upper end cover (301) and the lower end cover (302), mechanical bearings (5) being provided inside the two bearing seats (4), and the two mechanical bearings (5) being rotatably connected to a rotating shaft (12), and a flywheel (1) fixedly connected to the outside of the rotating shaft (12), characterized in that: The flywheel (1) is a cylinder with a T-shaped vertical cross section, and a rotor core (10) is fixedly connected to the outside of the lower cylinder of the flywheel (1).

2. The flywheel energy storage device of claim 1, wherein: The lower end cover (302) is provided with a magnetic levitation flange ring (6) at the top. The magnetic levitation flange ring (6) has a first annular groove at the top. A permanent magnet bearing (7) is embedded in the annular groove. The flywheel (1) has a second annular groove at the bottom that is compatible with the permanent magnet bearing (7). The upper part of the permanent magnet bearing (7) is embedded in the second annular groove.

3. The flywheel energy storage device of claim 1, wherein: The two bearing seats (4) each have a central slot on one side, and the two mechanical bearings (5) are respectively embedded in the two central slots.

4. The flywheel energy storage device of claim 1, wherein: Sealing rings (13) are provided at the interfaces between the housing (2) and the upper end cover (301) and the lower end cover (302).

5. The flywheel energy storage device of claim 1, wherein: The outer side of the rotor core (10) is provided with a number of toothed slots arranged in a circular array, the number of which is a multiple of the number of rotor pole pairs.

6. The flywheel energy storage device of claim 1, wherein: The inner wall of the housing (2) is fixedly connected to an excitation winding (8) located above the stator core (9). The stator core (9) has several through holes arranged in a ring array inside, and an armature winding (11) passes through each of the through holes.

7. The flywheel energy storage device of claim 3, wherein: The upper end cover (301) and the lower end cover (302) are both ferromagnetic end covers, the housing (2) is a ferromagnetic housing, the flywheel (1) is a ferromagnetic wheel, and the bearing seat (4) is a non-ferromagnetic seat.

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