A bearingless flux reversal permanent magnet motor with adjustable magnetic field and control method

Abstract

The present invention discloses a magnetically adjustable bearingless flux reversal permanent magnet motor and a control method thereof. The motor comprises a stator core, a rotor core, a suspension winding, a torque winding and a permanent magnet. The stator core is provided with stator teeth facing the rotor core, and the stator teeth are wound with windings. NdFeB permanent magnets are respectively surface-mounted on the left and right sides of the top of the tooth portion of each stator tooth, and the magnetization directions of the NdFeB permanent magnets on the tooth portion of the same stator tooth are the same, while the magnetization directions of the NdFeB permanent magnets on the tooth portions of adjacent stator teeth are opposite. An AlNiCo permanent magnet is arranged at the end of the yoke portion of each stator tooth, and NdFeB permanent magnets are arranged on both sides of each AlNiCo permanent magnet. The magnetization direction of the AlNiCo permanent magnets is radial, and a closed magnetic circuit can be formed between the NdFeB permanent magnets embedded in adjacent stator teeth and the surface-mounted NdFeB permanent magnets. The present invention achieves online regulation of the magnetic field by cleverly arranging the positions of the permanent magnets in the motor body and then controlling the zero-sequence current in the winding.

Description

Technical Field

[0001] The present invention belongs to the technical field of bearingless motors, and in particular relates to a bearingless flux reversal permanent magnet motor with adjustable magnetic field and a control method thereof. Background Art

[0002] With the rapid development of technology, high-speed and ultra-high-speed motors have been widely used in high-speed machine tools, turbomolecular pumps, compressors, and other equipment due to their high power density, compact size, strong reliability, and high efficiency. However, the rotor core of traditional high-speed motors is supported by mechanical bearings. When running at high or ultra-high speeds, the motor is subjected to significant impact, which can increase bearing wear, cause uneven air gaps, generate winding heat, reduce motor efficiency, and shorten the service life of the motor and bearings.

[0003] The introduction of magnetic bearing technology has largely solved the wear problem of mechanical bearings. Compared with traditional mechanical bearings, magnetic bearings have the advantages of long service life, no need for lubrication, and high precision. The bearingless permanent magnet synchronous motor is a new type of motor that combines rotary drive and magnetic bearing functions by applying magnetic bearings to traditional permanent magnet synchronous motors. The coils that generate radial suspension force in the magnetic bearings are installed in the stator core slots of the motor. These coils are generally called suspension windings. By controlling the magnitude and direction of the current flowing into the suspension windings, the air gap magnetic field generated by the motor's original windings is broken, thereby generating a controllable suspension force, which enables the rotor core to be stably suspended.

[0004] However, most current bearingless permanent magnet synchronous motors utilize a rotor core permanent magnet design. The permanent magnets are attached to or embedded within the rotor core, disrupting its integrity. High-speed rotation can lead to structural instability. Furthermore, since the permanent magnets are located on the rotor core, cooling conditions are poor and heat dissipation is difficult. High-speed rotation can cause demagnetization of the permanent magnets, hindering further improvements in motor performance and limiting the application of bearingless rotor core permanent magnet motors.

[0005] Currently, bearingless motors all use neodymium iron boron permanent magnets. However, due to the characteristics of these magnets, the air gap magnetic field cannot be adjusted, significantly limiting their speed regulation range and restricting their application in wide-speed regulation applications. Recently, some researchers have proposed a type of memory permanent magnet (such as alnico). By applying DC pulses, the magnetization state of these permanent magnets can be altered, allowing magnetization and demagnetization to be achieved, thereby adjusting the air gap magnetic field. However, this requires the addition of a magnetic field-regulating winding to the stator core winding, which takes up winding space and complicates the motor structure. Summary of the Invention

[0006] In order to solve the technical problems in the prior art that the air gap magnetic field of bearingless motors using NdFeB permanent magnets cannot be adjusted, and that a set of magnetic adjustment windings need to be added when adjusting the air gap magnetic field of bearingless motors using memory permanent magnets, the present invention provides a magnetically adjustable bearingless flux reversal permanent magnet motor and a control method. Specifically, by cleverly setting the positions and magnetizing directions of the NdFeB permanent magnets and the Alnico permanent magnets, a closed magnetic circuit can be formed between the NdFeB permanent magnets embedded in adjacent stator teeth and the surface-mounted NdFeB permanent magnets. Furthermore, based on the radial magnetization direction of the Alnico permanent magnets (controlling the magnetization direction to be radially inward or radially outward), the air gap magnetic field of the bearingless flux reversal permanent magnet motor can be adjusted.

[0007] To this end, the technical solution of the present invention provides a bearingless flux reversal permanent magnet motor with adjustable magnetic field, which includes at least a stator core, a rotor core, a winding, a neodymium iron boron permanent magnet, and an alnico permanent magnet; an air gap is provided between the stator core and the rotor core, the stator core is a salient pole structure, the stator core is provided with stator teeth facing the rotor core, and the winding is wound around the stator teeth;

[0008] Among them, NdFeB permanent magnets are respectively attached to the left and right sides of the top of the tooth portion of each stator tooth, and the magnetization directions of the NdFeB permanent magnets on the tooth portion of the same stator tooth are the same, and the magnetization directions of the NdFeB permanent magnets on the tooth portions of adjacent stator teeth are opposite; an AlNiCo permanent magnet is arranged at the end of the yoke of each stator tooth, and NdFeB permanent magnets are arranged on both sides of each AlNiCo permanent magnet, and the magnetization direction of the AlNiCo permanent magnet is radial magnetization, and a closed magnetic circuit can be formed between the NdFeB permanent magnets embedded in the yoke ends of adjacent stator teeth and the NdFeB permanent magnets attached to the top of the tooth portion.

[0009] Further optionally, the NdFeB permanent magnet at the end of the yoke is arranged at an angle to the AlNiCo permanent magnet.

[0010] Further optionally, the included angle between the NdFeB permanent magnet embedded in the end of the yoke and the AlNiCo permanent magnet is 120°.

[0011] Further optionally, the magnetizing direction of the NdFeB permanent magnet embedded in the yoke end is parallel to the lower edge line of the stator slot, and the magnetizing directions of the NdFeB permanent magnet embedded in the yoke end on adjacent stator teeth are relatively inward and away from each other.

[0012] Further optionally, the stator core is provided with two sets of windings, serving as a torque winding and a suspension winding respectively, and the two sets of windings are wound separately; wherein, the six sets of coils in the set of windings embedded in the stator core are sequentially wound on the stator teeth in the order of A1-C2-B1-A2-C1-B2 to form the torque winding, the A1-A2 coils are connected in series to form the A-phase torque winding, the B1-B2 coils are connected in series to form the B-phase torque winding, and the C1-C2 coils are connected in series to form the C-phase torque winding, and AC current is injected into the A, B, and C three-phase torque windings to generate electromagnetic torque;

[0013] The six sets of coils in the other set of windings embedded on the stator core are arranged counterclockwise along the circumference of the stator core as a1-c2-b1-a2-c1-b2, among which the a1 and a2 coils are connected in reverse to form the a-phase suspension winding, the b1 and b2 coils are connected in reverse to form the b-phase suspension winding, and the c1 and c2 coils are connected in reverse to form the c-phase suspension winding, and suspension current is injected into the three-phase suspension windings a, b, and c.

[0014] The present invention's technical solution preferentially controls the torque winding and suspension winding independently, achieving a natural decoupling of suspension force and torque, simplifying their control. Based on the required suspension force, the current flowing into the three-phase suspension windings (a, b, and c) can be rationally controlled to achieve stable suspension of the rotor core.

[0015] Further optionally, the stator core has a 6-slot structure, the rotor core has a 10-pole structure, the 10 modulation slots on the rotor core are evenly distributed along the circumference, the central angle corresponding to the arc of each modulation slot is 18°, and the central angle corresponding to the arc of each convex large tooth on the stator core is 50°.

[0016] Further optionally, the central angle corresponding to the NdFeB permanent magnet attached to the top of the tooth portion of the stator tooth is 19°.

[0017] Further optionally, the stator core and the rotor core are both formed by laminating silicon steel sheets.

[0018] In another aspect, the technical solution of the present invention provides a control method based on the bearingless flux reversal permanent magnet motor, comprising:

[0019] By controlling the zero-sequence current pulse in the winding, the magnetization direction of the AlNiCo permanent magnet is adjusted to be radially inward or radially outward, thereby achieving magnetization and demagnetization adjustment of the air gap magnetic field;

[0020] Among them, the magnetic flux generated by the Alnico permanent magnet has the same direction as the magnetic flux generated by the closed magnetic circuit of the NdFeB permanent magnet, superimposes on each other, and is in a magnetization state; otherwise, it is in a demagnetization state.

[0021] Further optionally, if a positive zero-sequence current pulse is applied so that the magnetization direction of the AlNiCo permanent magnet is radially inward, so that the magnetic flux generated by the AlNiCo permanent magnet is in the same direction as the magnetic flux generated by the closed magnetic circuit of the NdFeB permanent magnet, the bearingless flux reversal permanent magnet motor is in a magnetization state;

[0022] If a negative zero-sequence current pulse is applied, the magnetization direction of the AlNiCo permanent magnet is radially outward, so that the magnetic flux generated by the AlNiCo permanent magnet deviates from the direction of the magnetic flux generated by the closed magnetic circuit of the NdFeB permanent magnet, and the bearingless flux reversal permanent magnet motor is in a demagnetized state.

[0023] Beneficial effects

[0024] The technical solution of the present invention provides a magnetically adjustable bearingless flux reversal permanent magnet motor, which overcomes the technical barriers of the prior art that the air gap magnetic field of bearingless motors using NdFeB permanent magnets cannot be adjusted, and that bearingless motors using memory permanent magnets require an additional set of magnetic adjustment windings to adjust the air gap magnetic field. The technical solution of the present invention simultaneously arranges NdFeB permanent magnets and AlNiCo permanent magnets on the stator core. By cleverly setting the positions and magnetization directions of the NdFeB permanent magnets and AlNiCo permanent magnets, the motor can achieve air gap magnetic field adjustment even without the addition of magnetic adjustment windings. That is, by controlling the zero-sequence current in the existing windings, the magnetization direction of the AlNiCo permanent magnets is controlled to be radially inward or radially outward, thereby adjusting the directional relationship between the magnetic flux generated by the AlNiCo permanent magnet and the magnetic flux generated by the closed magnetic circuit of the NdFeB permanent magnet to achieve magnetization or demagnetization, eliminating the magnetic adjustment winding, maximizing the use of slot space, and improving the performance of the motor. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 A three-dimensional structural diagram of the bearingless flux reversal stator permanent magnet motor with adjustable magnetic field according to the present invention;

[0026] Figure 2 A two-dimensional plan view of the bearingless flux reversal stator permanent magnet motor with adjustable magnetic field according to the present invention;

[0027] Figure 3 This is the magnetic flux diagram of the motor in the magnetized state of the AlNiCo permanent magnet of the present invention;

[0028] Figure 4 This is the magnetic flux diagram of the motor in the demagnetized state of the AlNiCo permanent magnet of the present invention;

[0029] Figure 5 This is a diagram of the suspension principle of the present invention.

[0030] The accompanying drawings are numerals as follows:

[0031] 1 is the stator core, 2 is the rotor core, 3 is the winding, 4 is the NdFeB permanent magnet, and 5 is the AlNiCo permanent magnet. DETAILED DESCRIPTION

[0032] In order to solve the technical problems in the prior art that the air gap magnetic field of a bearingless motor using NdFeB permanent magnets cannot be adjusted, and that a bearingless motor using memory permanent magnets needs to add a set of magnetic adjustment windings when adjusting the air gap magnetic field, the present invention fully utilizes the respective advantages of NdFeB permanent magnets and AlNiCo permanent magnets, and creatively proposes a magnetically adjustable bearingless flux reversing permanent magnet motor that simultaneously uses NdFeB permanent magnets and AlNiCo permanent magnets, thereby solving the above technical problems by improving the motor body structure. Specifically, by cleverly arranging the positions and magnetization directions of NdFeB permanent magnets and AlNiCo permanent magnets on the stator core, and controlling the magnetization direction of the AlNiCo permanent magnets by controlling the zero-sequence current in the existing torque winding, the magnetic adjustment winding is eliminated, the slot space is maximized, and the performance of the motor is improved. The present invention will be further described below in conjunction with the embodiments.

[0033] Figure 1 This is a three-dimensional structural diagram of the bearingless flux reversal stator permanent magnet motor of the present invention. The motor adopts a stator core with 6 slots / rotor core with 10 poles, including a stator core 1, a rotor core 2, a winding 3, a neodymium iron boron permanent magnet 4 and an alnico permanent magnet 5. The stator core 1 is a salient pole structure with 6 salient large teeth. The arc of each salient large tooth has a central angle of 50°. The rotor core 2 is a salient pole structure with a total of 10 modulated teeth. The ten modulated teeth are evenly distributed along the circumference of the rotor core. The arc of each modulated tooth has a central angle of 18°. There are no permanent magnets on the rotor core 2, and the entire rotor core is made of laminated silicon steel sheets. Two NdFeB permanent magnets are attached to the surface of each stator core large tooth. The central angle of each NdFeB permanent magnet is 19°. The magnetization direction of the NdFeB permanent magnets is radial. The NdFeB permanent magnets on the same large tooth have the same magnetization direction, while the NdFeB permanent magnets on adjacent large teeth have opposite magnetization directions. The yoke of the stator core 1 is arranged with NdFeB permanent magnets 4 and AlNiCo permanent magnets 5. The two permanent magnet arrangements are as follows: Figure 2 As shown, the magnetization direction of the NdFeB permanent magnet 4 is parallel to the lower edge of the stator slot, and the angle between it and the AlNiCo permanent magnet 5 is 120°. The magnetization direction of the AlNiCo permanent magnet 5 is radial magnetization. A closed magnetic circuit can be formed between the NdFeB permanent magnets embedded in adjacent stator teeth and the surface-mounted NdFeB permanent magnets. The air gap between the stator core 1 and the rotor core 2 is 2mm. Figure 2 shown.

[0034] It should be understood that the above-mentioned central angle and air gap size are preferred parameters of this embodiment. In other feasible embodiments, they can be adaptively adjusted according to the accuracy.

[0035] The technical solution of the present invention preferably adopts a dual winding structure, that is, two sets of windings are provided on the stator core, serving as torque winding and suspension winding respectively, and the two sets of windings are wound separately. Figure 2As shown, the A1 coil and the A2 coil are connected in series in a forward direction to form the A phase torque winding, the B1 coil and the B2 coil are connected in series in a forward direction to form the B phase torque winding, and the C1 coil and the C2 coil are connected in series in a forward direction to form the C phase torque winding. The current flowing into the A phase torque terminal is Phases B and C lag behind phase A by 120 degrees, respectively. t is the torque current amplitude, ω is the electrical frequency of the torque current, θ r The phase of the torque current. Phase A, B, and C are controlled independently and do not affect each other.

[0036] Similarly, a set of suspension windings is wound around the stator core. The six sets of coils are arranged counterclockwise along the circumference of the stator core as a1-c2-b1-a2-c1-b2. The a1 and a2 coils are connected in reverse to form the a-phase suspension winding, the b1 and b2 coils are connected in reverse to form the b-phase suspension winding, and the c1 and c2 coils are connected in reverse to form the c-phase suspension winding. The a, b, and c three-phase suspension windings are controlled separately. According to the required suspension force, the current flowing into the a, b, and c three-phase suspension windings can be reasonably controlled to achieve stable suspension of the rotor core and generate a stable suspension force.

[0037] Therefore, based on the dual-winding structure, by controlling the current in the stator core torque winding, the motor rotor core can be rotated stably; by controlling the suspension current in the stator core suspension winding, the motor rotor core can be suspended in the XY directions. The suspension winding and the torque winding are wound separately on the stator core, which realizes the natural decoupling of the suspension force and the torque, making the control method simpler. It should be understood that on the basis of meeting the core technical ideas of the present invention (while providing NdFeB permanent magnets and AlNiCo permanent magnets on the stator core, by cleverly setting the position and magnetization direction of NdFeB permanent magnets and AlNiCo permanent magnets, so that the motor can achieve air gap magnetic field regulation even without adding a magnetic adjustment winding), the use of other feasible ways of setting the suspension winding and the torque winding also meets the requirements of the present invention and falls within the scope of protection of the present invention.

[0038] exist Figure 3 The magnetizing direction of the bearingless flux reversal permanent magnet motor is shown in the figure. Figure 3The bearingless flux-reversing permanent magnet motor is in an overall magnetization state. The NdFeB permanent magnet attached to the large tooth of stator tooth No. 1 is magnetized radially inward, while the corresponding NdFeB permanent magnet within stator core No. 1 is magnetized from right to left, parallel to the bottom line of the stator slot. The permanent magnet attached to the large tooth of stator core No. 2 is magnetized radially outward, while the corresponding NdFeB permanent magnet within it is magnetized outward, parallel to the bottom line of the stator slot. At this time, the zero-sequence current pulse in the torque winding causes the AlNiCo permanent magnet under stator tooth No. 1 to magnetize radially inward, while the AlNiCo permanent magnet under stator tooth No. 2 to magnetize radially outward. The magnetic flux generated by the AlNiCo permanent magnet and the NdFeB permanent magnet have the same direction and overlap, resulting in a magnetization state.

[0039] exist Figure 4 The magnetizing direction of the bearingless flux reversal permanent magnet motor is shown in the figure. Figure 4 In the overall demagnetized state, the NdFeB permanent magnet attached to the large tooth of stator tooth No. 1 is magnetized radially inward, while the corresponding NdFeB permanent magnet within stator core No. 1 is magnetized along the interior of the stator core, parallel to the bottom line of the stator slot. The permanent magnet attached to the large tooth of stator core No. 2 is magnetized radially outward, while the corresponding NdFeB permanent magnet within it is magnetized outward, parallel to the bottom line of the stator slot. At this time, the zero-sequence current pulse in the torque winding causes the AlNiCo permanent magnet under stator tooth No. 1 to magnetize radially outward, while the AlFeB permanent magnet under stator tooth No. 2 is magnetized radially inward. The magnetic flux generated by the AlNiCo permanent magnet and the magnetic flux generated by the NdFeB permanent magnet form a short circuit in the stator core yoke, reducing the magnetic flux within the stator core and causing the overall demagnetization state.

[0040] It should be noted that Figure 3 as well as Figure 4 This is a schematic illustration to explain the magnetization and demagnetization states. The identification of magnetization or demagnetization is determined by the increase or decrease of the magnetic flux inside the stator core. The corresponding control methods include:

[0041] By controlling the zero-sequence current pulse in the winding, the magnetization direction of the AlNiCo permanent magnet is adjusted to radially inward or radially outward, thereby realizing magnetization and demagnetization adjustment of the air gap magnetic field; wherein, the magnetic flux generated by the AlNiCo permanent magnet has the same direction as the magnetic flux generated by the closed magnetic circuit of the NdFeB permanent magnet, superimposes on each other, and is in a magnetization state; otherwise, it is in a demagnetization state.

[0042] If a positive zero-sequence current pulse is applied, the magnetization direction of the AlNiCo permanent magnet is radially inward, so that the magnetic flux generated by the AlNiCo permanent magnet is in the same direction as the magnetic flux generated by the closed magnetic circuit of the NdFeB permanent magnet, the bearingless flux reversal permanent magnet motor is in a magnetizing state; if a negative zero-sequence current pulse is applied, the magnetization direction of the AlNiCo permanent magnet is radially outward, so that the magnetic flux generated by the AlNiCo permanent magnet is in the same direction as the magnetic flux generated by the closed magnetic circuit of the NdFeB permanent magnet, the bearingless flux reversal permanent magnet motor is in a demagnetizing state.

[0043] It should also be noted that the technical solution of the present invention provides a suspension winding, and stable suspension is achieved by controlling the suspension current injected into the suspension winding. It should be understood that achieving suspension control by controlling the suspension current is a conventional method in the art, and therefore, a detailed description thereof will not be given. Figure 5 The following example illustrates the suspension control. Figure 5 The magnetic flux generated by the permanent magnets on the stator teeth housing the A1 and A2 windings runs from right to left. When a current flows through the floating end of the A1 winding, the generated magnetic flux has the same direction as the permanent magnet on the A1 stator tooth, from right to left, thus increasing magnetization. When a current flows through the floating end of the A2 winding, the generated magnetic flux has the opposite direction, from left to right, thus demagnetizing. This generates a radial force along the negative X-axis, causing the rotor core to displace in that direction. The same principle also generates a radial force along the Y-axis, causing the rotor core to displace in that direction.

[0044] It should be emphasized that the examples described in the present invention are illustrative rather than restrictive. Therefore, the present invention is not limited to the examples described in the specific embodiments. Any other embodiments derived by those skilled in the art based on the technical solution of the present invention that do not depart from the purpose and scope of the present invention, whether modified or replaced, also fall within the scope of protection of the present invention.

Claims

1. A bearingless flux reversal permanent magnet motor with adjustable magnetic field, characterized by: The invention comprises at least a stator core, a rotor core, windings, NdFeB permanent magnets and AlNiCo permanent magnets; an air gap is provided between the stator core and the rotor core; the stator core is a salient pole structure, the stator core is provided with stator teeth facing the rotor core, and the windings are wound around the stator teeth; Among them, NdFeB permanent magnets are respectively attached to the left and right sides of the top of the tooth portion of each stator tooth, and the magnetization directions of the NdFeB permanent magnets on the tooth portion of the same stator tooth are the same, and the magnetization directions of the NdFeB permanent magnets on the tooth portions of adjacent stator teeth are opposite; an AlNiCo permanent magnet is arranged at the end of the yoke of each stator tooth, and NdFeB permanent magnets are arranged on both sides of each AlNiCo permanent magnet, and the magnetization direction of the AlNiCo permanent magnet is radial magnetization, and a closed magnetic circuit can be formed between the NdFeB permanent magnets embedded in the yoke ends of adjacent stator teeth and the NdFeB permanent magnets attached to the top of the tooth portion.

2. The bearingless flux reversal permanent magnet motor according to claim 1, characterized in that: The NdFeB permanent magnet at the end of the yoke is arranged at an angle to the AlNiCo permanent magnet.

3. The bearingless flux reversal permanent magnet motor according to claim 2, characterized in that: The included angle between the NdFeB permanent magnet embedded in the end of the yoke and the AlNiCo permanent magnet is 120°.

4. The bearingless flux reversal permanent magnet motor according to claim 1, characterized in that: The magnetization direction of the NdFeB permanent magnet embedded in the end of the yoke is parallel to the lower edge line of the stator slot, and the magnetization direction of the NdFeB permanent magnet embedded in the end of the yoke on adjacent stator teeth is relatively inward and away from outward.

5. The bearingless flux reversal permanent magnet motor according to claim 1, characterized in that: The stator core is provided with two sets of windings, serving as a torque winding and a suspension winding respectively, and the two sets of windings are wound separately; wherein, the six sets of coils in one set of windings embedded in the stator core are wound on the stator teeth in the order of A1-C2-B1-A2-C1-B2 to form the torque winding, wherein the A1-A2 coils are connected in series to form the A-phase torque winding, the B1-B2 coils are connected in series to form the B-phase torque winding, and the C1-C2 coils are connected in series to form the C-phase torque winding, and AC current is injected into the A, B, and C three-phase torque windings to generate electromagnetic torque; The six sets of coils in the other set of windings embedded on the stator core are arranged counterclockwise along the circumference of the stator core as a1-c2-b1-a2-c1-b2, among which the a1 and a2 coils are connected in reverse to form the a-phase suspension winding, the b1 and b2 coils are connected in reverse to form the b-phase suspension winding, and the c1 and c2 coils are connected in reverse to form the c-phase suspension winding, and suspension current is injected into the three-phase suspension windings a, b, and c.

6. The bearingless flux reversal permanent magnet motor according to claim 1, characterized in that: The stator core has a 6-slot structure, the rotor core has a 10-pole structure, the 10 modulation slots on the rotor core are evenly distributed along the circumference, the central angle corresponding to the arc of each modulation slot is 18°, and the central angle corresponding to the arc of each convex large tooth on the stator core is 50°.

7. The bearingless flux reversal permanent magnet motor according to claim 1, characterized in that: The central angle of the NdFeB permanent magnet attached to the top of the stator tooth is 19°.

8. The bearingless flux reversal permanent magnet motor according to claim 1, characterized in that: The stator core and the rotor core are both formed by laminating silicon steel sheets.

9. A control method for a bearingless flux reversal permanent magnet motor according to any one of claims 1 to 8, characterized in that: include: By controlling the zero-sequence current pulse in the winding, the magnetization direction of the AlNiCo permanent magnet is adjusted to be radially inward or radially outward, thereby achieving magnetization and demagnetization adjustment of the air gap magnetic field; Among them, the magnetic flux generated by the Alnico permanent magnet has the same direction as the magnetic flux generated by the closed magnetic circuit of the NdFeB permanent magnet, superimposes on each other, and is in a magnetization state; otherwise, it is in a demagnetization state.

10. The control method according to claim 9, characterized in that: If a positive zero-sequence current pulse is applied so that the magnetization direction of the AlNiCo permanent magnet is radially inward, and the magnetic flux generated by the AlNiCo permanent magnet is in the same direction as the magnetic flux generated by the closed magnetic circuit of the NdFeB permanent magnet, the bearingless flux reversal permanent magnet motor is in a magnetizing state; If a negative zero-sequence current pulse is applied, the magnetization direction of the AlNiCo permanent magnet is radially outward, so that the magnetic flux generated by the AlNiCo permanent magnet deviates from the direction of the magnetic flux generated by the closed magnetic circuit of the NdFeB permanent magnet, and the bearingless flux reversal permanent magnet motor is in a demagnetized state.

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