A natural magnetic levitation switched reluctance energy storage flywheel motor for extreme environments

Abstract

This invention relates to the field of motors and relates to a natural magnetic levitation switched reluctance energy storage flywheel motor for extreme environments. The invention aims to address the problems of large size and difficult control of magnetic levitation motors used in existing energy storage systems for extreme environments. The natural magnetic levitation switched reluctance energy storage flywheel motor for extreme environments described in this invention includes a coaxially arranged shaft, stator, and rotor. The stator comprises three coaxial segments arranged axially. Each segment includes a stator core and stator windings. The stator core has an even number of stator slots, and each slot contains two conductors. The two conductors in one slot are connected in series with one conductor in each of the two adjacent slots, forming two branches. All branches are evenly distributed circumferentially around the stator core. One end of each branch is connected in parallel to form one phase of a three-phase winding, and the other ends of each branch are connected in parallel to form the midpoint of the three-phase winding.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of electric machines. BACKGROUND

[0002] Flywheel energy storage system stores energy through high-speed rotating flywheel, realizes the cyclic conversion of electric energy and kinetic energy. It is a pure physical energy storage method. The latest technical development direction of flywheel energy storage system is to adopt magnetic suspension technology. In the flywheel energy storage system, the shaft system is an important device for power transmission and is also the main part of flywheel energy self-loss, which affects the stability, efficiency and service life of the flywheel system.

[0003] Extreme environment also needs flywheel energy storage system. For example, the motor used in space needs to operate at high speed under low temperature conditions, which shortens the service life of mechanical bearings. Therefore, a motor with suspension capability is required. The diurnal temperature difference on the surface of the moon can reach-180℃ to +150℃. A servo drive assembly that can directly operate in such an extreme environment is needed. For example, power generation system and energy storage system used in space extreme environment and so on. Similarly, the earth also has extreme environments, such as nuclear radiation environment, extreme temperature difference environment, sudden danger environment and so on. The key to breaking through the extreme temperature difference environment is that the traditional bearing adopts negative clearance to improve the precision, and the thermal expansion and cold contraction of the mechanical bearing will inevitably lead to the damage, jamming or wear of the bearing clearance. Therefore, the design of bearingless is usually chosen to solve this problem. However, the cost of making the motor rotor suspended is very high. In a magnetic suspension motor, the volume of the magnetic suspension bearing accounts for 60%, and the controller of the magnetic suspension bearing is high in cost and complex. SUMMARY

[0004] The present application is to solve the problem of large volume and difficult control of the energy storage system magnetic suspension motor used in the existing extreme environment, and provides a kind of extreme environment natural magnetic suspension switched reluctance energy storage flywheel motor.

[0005] A kind of extreme environment natural magnetic suspension switched reluctance energy storage flywheel motor, including coaxial setting shaft, stator and rotor, stator includes three sections coaxially and along axial arrangement, each section includes stator core and stator winding, stator core is opened with even number of stator slots, each stator slot has 2 wire rods, two wire rods in a stator slot are respectively connected in series with a wire rod in the adjacent slot on both sides to form two branches, all branches are evenly arranged along the circumference of stator core, one end of all branches is connected in parallel to form one phase of three-phase winding, and the other end of all branches is connected in parallel as the midpoint of three-phase winding.

[0006] Further, the above-mentioned kind of extreme environment natural magnetic suspension switched reluctance energy storage flywheel motor further includes a shell, the shell is a vacuum cavity structure, the shaft, the stator and the rotor are located in the vacuum cavity of the shell.

[0007] Furthermore, both ends of the aforementioned rotating shaft are connected to the housing via bearings.

[0008] Furthermore, the bearing clearance of the aforementioned bearing is 0.1mm to 0.5mm.

[0009] Furthermore, a gasket is provided between the bearing and the housing.

[0010] Furthermore, the aforementioned casing is equipped with electrical interfaces.

[0011] Furthermore, the stator is coaxially sleeved outside the rotor, or the rotor is coaxially sleeved outside the stator.

[0012] The beneficial effects of this invention are as follows:

[0013] (1) The motor has a simple and robust structure and a simple manufacturing process. It is low in cost. The rotor is made of silicon steel sheets and can operate at extremely high speeds. The stator coil is a concentrated winding, which is easy to install. The ends are short and firm, and the operation is reliable. It can be used in various harsh, high-temperature and strong vibration environments.

[0014] (2) The main losses occur in the stator, and the motor is easy to cool; the rotor has no permanent magnets, which allows for a higher temperature rise.

[0015] (3) The direction of torque is independent of the direction of phase current, which can reduce the number of switching devices in the power converter and reduce system cost.

[0016] (4) The power converter will not experience shoot-through failure and has high reliability.

[0017] (5) It has a large starting torque, good low-speed performance, and no inrush current phenomenon that occurs when an asynchronous motor starts.

[0018] (6) Wide speed range, flexible control, and easy to achieve torque-speed characteristics for various special requirements.

[0019] (7) It has high efficiency over a wide range of speeds and power.

[0020] (8) It can operate in four quadrants and has strong regenerative braking capability.

[0021] In summary, this invention overcomes the challenges of applications in extreme temperature difference environments, eliminating the problems of bearing clearance damage, jamming, or wear caused by thermal expansion and contraction in mechanical bearings under extreme conditions. This invention can be used in large-scale mechanical equipment in extreme space environments, particularly in energy storage flywheel systems within such environments. It can also be used in extreme Earth environments such as nuclear radiation environments, extreme temperature difference environments, and sudden hazardous environments. Attached Figure Description

[0022] Figure 1This is a schematic diagram of an internal rotor switched reluctance motor.

[0023] Figure 2 This is a schematic diagram of an external rotor switched reluctance motor.

[0024] Figure 3 The image shows a magnetic field simulation diagram of a traditional switched reluctance motor, where (a) indicates that the teeth and slots of the stator and rotor are aligned, and (b) indicates that the teeth and slots of the stator and rotor are misaligned.

[0025] Figure 4 This is a magnetic field simulation diagram of the switched reluctance motor of the present invention, wherein (a) indicates that the teeth and slots of the stator and rotor are aligned, and (b) indicates that the teeth and slots of the stator and rotor are misaligned;

[0026] Figure 5 The graph shows the rate of change of inductance of a switched reluctance motor.

[0027] Figure 6 This is a schematic diagram of the connection structure of the stator windings.

[0028] Figure 7 This is a radial sectional view of a switched reluctance motor.

[0029] Figure 8 This is an axial sectional view of a switched reluctance motor. Detailed Implementation

[0030] 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, and 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. It should be noted that, unless otherwise specified, the embodiments and features in the embodiments of the present invention can be combined with each other.

[0031] Specific implementation method one: Refer to Figures 1 to 8 This embodiment describes a natural magnetic levitation switched reluctance energy storage flywheel motor for extreme environments, comprising a rotating shaft, a stator, a rotor 3, and a housing 5 arranged coaxially.

[0032] The outer casing 5 is a vacuum chamber structure, and the rotating shaft, stator, and rotor 3 are all located within the vacuum chamber 6 of the outer casing 5. The natural magnetic levitation flywheel motor is surrounded by an outer vacuum chamber, which is located outside the flywheel motor and seals it within. The flywheel motor is an internal rotor flywheel motor, whose rotor can provide momentum. Both ends of the rotating shaft are connected to the outer casing 5 via bearings 4. The outer casing 5 is provided with an electrical interface 8. A washer 7 is provided between the bearing 4 and the outer casing 5.

[0033] The bearing clearance of the bearing 4 is 0.1mm to 0.5mm, which can effectively eliminate the problems of bearing clearance damage, jamming, or wear caused by thermal expansion and contraction of the additional bearing 4 in extreme environments. This embodiment can be used in large mechanical equipment in extreme space environments, with a motor operating temperature of ±180℃. The stator includes three coaxial sections arranged along the axial direction, with each phase winding having a dedicated core section, and the winding method of the windings is consistent. Specifically, each section includes a stator core 1 and a stator winding 2. The stator core 1 has 16 stator slots, and each phase winding can generate restoring force against the radial offset of the motor from 16 directions. Therefore, each phase winding can form a winding symmetrically distributed along the circumference center and can generate a centrally symmetrical torque couple. The three stator core sections are offset by 120° electrical angles from each other. The specific circuit structure is as follows: There are 2 wires in each stator slot. The two wires in one stator slot are connected in series with one wire in the two adjacent slots to form two branches. All branches are evenly distributed along the circumference of the stator core. One end of all branches is connected in parallel to form one phase of the three-phase winding. The other end of all branches is connected in parallel to form the midpoint of the three-phase winding.

[0034] In this embodiment, the stator is divided into three axial sections, which correspond to the UVW three phases of the flywheel motor. For example... Figure 6 As shown, slots 1, 3, 5, 7, 9, 11, 13, and 15 are connected in parallel to form the three-phase winding ports for U, V, and W respectively. Slots 2, 4, 6, 8, 10, 12, 14, and 16 are connected in parallel to form the midpoint port O of the three-phase windings for U, V, and W respectively. Each independent winding of the U, V, and W three-phase windings has 8 pairs of mutually mirror-symmetrically distributed windings connected in parallel; then, the midpoint ports O of the three-phase windings are connected in parallel to ultimately form the U, V, and W three-phase windings.

[0035] There is an attractive force between the stator core and the rotor core. Due to the function of bearing 4, the air gap between the stator and rotor is kept equal, and the attractive force is equal everywhere along the circumference. The bearing makes the radial attractive force in the air gap of the motor equal everywhere and cancels each other out. If there is a deviation in the air gap at both ends of the same diameter, the rotor body will be attracted to the side with the smaller air gap. The back electromotive force (or transformer electromotive force) of the parallel branch on the side with the smaller air gap will inevitably increase, and the current will decrease. Conversely, the back electromotive force (or transformer electromotive force) of the parallel branch on the side with the larger air gap will decrease, and the current will increase. Thus, the radial tension on the side with the larger air gap increases, and the radial tension on the side with the smaller air gap decreases, which will inevitably cause the air gap to change in the direction of reducing the deviation and stabilize the air gap deviation. For switched reluctance motors, even when the motor is in the starting state and has not yet started rotating, the transformer electromotive force, i.e., the induced electromotive force, already exists. Therefore, this embodiment has a complete radial natural magnetic levitation realignment capability. Since switched reluctance motors do not have permanent magnet interference force, it is more conducive to achieving high-precision natural electromagnetic levitation. With the addition of bearings, it can adapt to high loads and extreme all-weather environments. The maximum inductance / minimum inductance ratio is 21.25 (much larger than traditional inductance), reducing the rate of change of inductance at the ends, lowering noise, and significantly improving the motor's power density, outperforming permanent magnet motors.

[0036] The stator is coaxially sleeved outside the rotor 3, or the rotor 3 is coaxially sleeved outside the stator. Figure 1 It is an internal rotor motor, with the outer stator divided into three sections. Figure 2 It is an external rotor motor, with the inner stator divided into three sections.

[0037] In this embodiment, the ratio of the maximum inductance Lmax to the minimum inductance Lmin is as high as 6-8, while traditional switched reluctance motors can only achieve around 2.5. Due to the high inductance ratio of the switched reluctance motor, the motor's output torque is large, meaning its power density is high. The principle of the switched reluctance motor not only allows it to operate in four quadrants, but also enables very simple voltage regulation of the output voltage in generator mode by adjusting the conduction angle. Furthermore, the switched reluctance motor has the most robust structure, making it an ideal motor for energy storage flywheels operating in extreme space environments.

[0038] This embodiment, with its stator segmentation and tooth-coiling ratio matching, significantly shortens the magnetic circuit length compared to traditional switched reluctance motors. The torque range is significantly reduced, allowing this embodiment to substantially increase motor power density and improve efficiency. The torque fluctuation and noise levels of this embodiment are comparable to those of permanent magnet motors and induction motors. The motor and its driver are simple, reducing manufacturing costs by more than 30%. This embodiment features segmented independent stator windings, increasing the number of motor segments by three times, the number of conductor turns per slot by three times, and the magnetic levitation restoring force by nine times.

[0039] The efficiency curve of the switched reluctance motor is as follows: within the range of 125-50% of rated speed and 50-300% of rated torque, the efficiency is not less than 82%, with a maximum efficiency of 92%. The efficiency of a permanent magnet brushless motor generally drops to 50% or below when the speed decreases to 50% of the rated speed. The switched reluctance motor of this invention can achieve 150% of the rated torque at 30% of the rated current.

[0040] While the invention has been described herein with reference to specific embodiments, it should be understood that these embodiments are merely examples of the principles and applications of the invention. Therefore, it should be understood that many modifications can be made to the exemplary embodiments, and other arrangements can be designed without departing from the spirit and scope of the invention as defined by the appended claims. It should be understood that different dependent claims and features described herein can be combined in ways different from those described in the original claims. It is also understood that features described in conjunction with individual embodiments can be used in other described embodiments.

Claims

1. A natural magnetic suspension switch reluctance energy storage flywheel motor in extreme environment, comprising a rotating shaft, a stator and a rotor (3) arranged coaxially, characterized in that, the stator comprises three sections arranged coaxially and along the axial direction, and the three sections correspond to U, V and W three phases of the motor respectively, each section comprises a stator core (1) and a stator winding (2), the stator core (1) is provided with an even number of stator slots, and each stator slot has two wire rods, the two wire rods in one stator slot are respectively connected in series with one wire rod in the adjacent slot on both sides to form two branches, all the branches are uniformly arranged along the circumference of the stator core (1), one end of all the branches are connected in parallel to form one phase of the three-phase winding, and the other end of all the branches are connected in parallel as the midpoint of the three-phase winding.

2. The extreme environment natural magnetic suspension switched reluctance energy storage flywheel motor of claim 1, wherein, Further comprising a shell (5), the shell (5) is a vacuum cavity structure, and the rotating shaft, the stator and the rotor (3) are located in the vacuum cavity (6) of the shell (5).

3. The extreme environment natural magnetic suspension switched reluctance energy storage flywheel motor of claim 2, wherein, The rotating shaft is connected with the shell (5) through bearings (4) at both ends.

4. The extreme environment natural magnetic suspension switched reluctance energy storage flywheel motor of claim 3, wherein, The bearing gap of the bearing (4) is 0.1 mm ~0.5mm.

5. A magnetic levitation switched reluctance energy storage flywheel motor in extreme environment according to claim 3 or 4, characterized in that, A gasket (7) is arranged between the bearing (4) and the shell (5).

6. The extreme environment natural magnetic suspension switched reluctance energy storage flywheel motor of claim 2, wherein, An electrical interface (8) is arranged on the shell (5).

7. The extreme environment natural magnetic suspension switched reluctance energy storage flywheel motor of claim 1, wherein, The stator is coaxially sleeved outside the rotor (3).

8. The extreme environment natural magnetic suspension switched reluctance energy storage flywheel motor of claim 1, wherein, The rotor (3) is coaxially sleeved outside the stator.

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