A method for designing parameters of a heteropolar AC hybrid magnetic bearing and an auxiliary bearing

Abstract

The present invention discloses a heteropolar AC hybrid magnetic bearing and an auxiliary bearing parameter design method, comprising a stator and a rotor, wherein three control poles and three permanent magnetic poles are evenly spaced on the inner circumference of the stator, the area of ​​the permanent magnetic pole is half of the area of ​​the control pole, the three permanent magnetic poles are built with permanent magnets, auxiliary bearings are attached to the inner sides of the permanent magnetic poles and the control poles, and a control coil is wound on the control pole; the rotor comprises a rotor core. Given the rotor outer diameter, air gap length, saturated air gap flux density, magnetic pole spacing and axial length, a mathematical model of the radial maximum controllable suspension force and the maximum uncontrollable suspension force is derived, and the control flux density and bias flux density generated by the suspension winding and the permanent magnet under the control pole are equal to 0.5 times the air gap saturation flux density, and the minimum controllable suspension force is greater than the maximum uncontrollable suspension force as a design basis, and the maximum thickness of the auxiliary bearing is calculated. The magnetic bearing designed by the present invention has the largest controllable suspension force and can ensure that the rotor can float stably in a stationary state.

Description

Technical Field

[0001] The invention relates to the technical field of magnetic suspension, and in particular to a heteropolar AC hybrid magnetic bearing which has the largest controllable suspension force and can stably float in a static state, and a parameter design method for an auxiliary bearing. Background Art

[0002] Hybrid magnetic bearings are high-performance bearings that use electromagnetic force to achieve non-contact suspension support of stators and rotors. Due to their friction-free and wear-free technical characteristics, they can support motor rotors to operate at high speeds, with high precision and low energy consumption, thus improving the service life and reliability of bearings. Therefore, hybrid magnetic bearings have extremely high application value in high-speed mechanical equipment, precision instruments and meters, aerospace, electric power industry, petrochemical industry and other fields.

[0003] Homopolar hybrid magnetic bearings and heteropolar hybrid magnetic bearings are two common types of hybrid magnetic bearings. Homopolar hybrid magnetic bearings refer to the bias magnetic field on the rotor with the same polarity. Heterpolar hybrid magnetic bearings refer to the bias flux on the rotor with opposite polarity. According to the characteristics of the bias flux, there are obvious differences in the structure of the two hybrid magnetic bearings, that is, homopolar hybrid magnetic bearings often use axially magnetized permanent magnets, and the stator core is a double-piece structure, and the permanent magnet is located between the double-piece stator core. The permanent magnets and stator poles of heteropolar hybrid magnetic bearings are located in the same space. Therefore, the axial length of heteropolar hybrid magnetic bearings is shorter and the critical speed is higher.

[0004] The general heteropolar hybrid magnetic bearings often adopt the design method of the same area of ​​permanent magnetic poles and control poles. When the inner diameter of the stator is determined, when the area of ​​the permanent magnetic poles increases, the area of ​​the control poles decreases, resulting in a decrease in the controllable suspension force generated by the control poles. Therefore, the design of the traditional heteropolar hybrid magnetic bearings results in a low density of controllable suspension force, and it is difficult to ensure that the rotor can float stably in a static state. On the contrary, the reduction of the area of ​​the permanent magnetic poles leads to an increase in the air gap magnetic density under the permanent magnetic poles. The suction force of the permanent magnetic poles on the rotor is an uncontrollable suspension force. This force is proportional to the product of the square of the air gap air density and the magnetic density area. Therefore, reducing the area of ​​the permanent magnetic poles will lead to an increase in the uncontrollable suspension force. Therefore, how to design the main parameters of the heteropolar AC hybrid magnetic bearings with a larger controllable suspension force and stable floating in a static state is of great value to improving the dynamic and static performance of heteropolar hybrid magnetic bearings. Summary of the invention

[0005] Purpose of the invention: In view of the problems pointed out in the background technology, the present invention proposes a method for designing parameters of a heteropolar AC hybrid magnetic bearing and an auxiliary bearing. First, according to given conditions, the main parameters of the heteropolar AC hybrid magnetic bearing are designed, and then the mathematical model of controllable and uncontrollable suspension force is derived according to the equivalent magnetic circuit. Then, based on the design basis that the minimum controllable suspension force is greater than the maximum uncontrollable suspension force, the thickness of the auxiliary bearing is determined. The designed heteropolar AC hybrid magnetic bearing has a larger controllable suspension force, and can float stably under the designed auxiliary bearing thickness, and also has the advantage of fully utilizing materials.

[0006] Technical solution: The present invention discloses a method for designing auxiliary bearing parameters of a heteropolar AC hybrid magnetic bearing. The heteropolar AC hybrid magnetic bearing includes a stator part and a rotor part. The stator part includes a stator yoke, three permanent magnet poles and three control poles. The three permanent magnets are embedded in the permanent magnet poles. Control coils with the same number of turns are wound on the three control poles. The control coils are star-connected as a three-phase suspension winding. Auxiliary bearings are attached to the inner sides of the permanent magnet poles and the control poles. The rotor part includes a rotor core. The area S of the control pole is c Equal to 2 times the area of ​​the permanent magnet pole S p ; An average air gap is set between the control pole, the permanent magnet pole and the rotor core, and a radial air gap is set between the auxiliary bearing and the rotor core;

[0007] Given the rotor outer diameter r, average air gap length g, saturated air gap flux density B s 、Inter-pole arc spacing l slot and the axial thickness of the bearing l z , the control flux density and bias flux density under the control pole are both equal to 0.5B s As a prerequisite, the minimum controllable suspension force is greater than the maximum uncontrollable suspension force as the design basis, and the auxiliary bearing thickness is designed under the condition that the rotor can float under the maximum eccentricity.

[0008] Furthermore, the specific auxiliary bearing design process is as follows:

[0009] Step 1: Select the permanent magnet material and determine the air gap saturation flux density B s , average air gap length g, rotor outer diameter r, axial thickness of the bearing l z , arc spacing between magnetic poles l slot ;

[0010] Step 2: Calculate the winding ampere-turns Ni max The magnetomotive force F provided by the permanent magnet m :

[0011]

[0012] Step 3: Assume that the rotor is subjected to a slight disturbance and produces radial displacement, and the displacement is recorded as x and y respectively. The air gap expression under each magnetic pole can be obtained as follows:

[0013] Right now:

[0014] Among them, g a -g C They are the air gaps between each magnetic pole and the rotor, both smaller than gl s ;

[0015] Step 4: The expression of air gap reluctance under each magnetic pole is:

[0016]

[0017] Among them, S p and S c represents the magnetic pole area of ​​the corresponding permanent magnet pole and control pole, l c and l z They represent the control pole arc length and the axial thickness of the bearing, respectively. p is the permanent magnet pole arc length;

[0018] Step 5: Calculate the air gap bias flux under the permanent magnet pole and control pole:

[0019]

[0020] Among them, Φ a is the magnetic flux generated by the permanent magnet on pole a at the air gap between pole a and the rotor, Φ aC is the magnetic flux generated by the permanent magnet on pole a at pole C and the rotor air gap, Φ aB is the magnetic flux generated by the permanent magnet on pole a at pole B and the rotor air gap, and the other formulas are the same;

[0021] Step 6: To facilitate calculation on the oxy surface, the three-phase control current on the magnetic poles A, B, and C of the three control poles 5 is transformed into two phases using Clark transformation:

[0022]

[0023] where i A 、i B 、i C are the original three-phase currents, i x and i y is the equivalent current in the x-direction and y-direction after conversion, that is:

[0024]

[0025] Step 7: The magnetomotive force generated by the winding is:

[0026]

[0027] Step 8: Calculate the suspension flux generated by the control winding:

[0028]

[0029] Step 9: From the above formula, we can get the total flux expression of the three control poles:

[0030]

[0031] Step 10: Based on the above expression of magnetic flux, the expressions of suspension force in the x and y directions are obtained respectively:

[0032]

[0033] Among them, F x and F y are the resultant forces of the controllable suspension force and the uncontrollable suspension force in the x-direction and y-direction respectively;

[0034] Step 11: Linearize the suspension force expression to obtain:

[0035]

[0036] Then, F x and F y The displacement and control current in the equation are calculated, and the partial derivative is calculated. c Expression and l p and l c The equation of the relationship:

[0037]

[0038] The relationship between the controllable suspension force and the uncontrollable suspension force in the x-direction and y-direction is obtained respectively:

[0039]

[0040] Among them, F xp and F yp is the uncontrollable suspension force in the x and y directions, F xc and F yc is the controllable suspension force in the x and y directions; the mathematical models of the maximum controllable suspension force and the maximum uncontrollable suspension force are as follows:

[0041]

[0042] Step 12: By comparison, it can be seen that when the control current is the same, the controllable suspension force in the x direction is smaller than the controllable suspension force in the y direction; when the displacement of the rotor in the x and y directions is the same, the uncontrollable suspension force in the x direction is larger than the controllable suspension force in the y direction;

[0043] Combined with the design principle that the minimum controllable suspension force should be greater than the maximum uncontrollable suspension force, the required auxiliary bearing thickness l is obtained while ensuring that the rotor can be stably suspended. s ,Right now:

[0044]

[0045] i xmax is the maximum current in the x direction; we get l s The expression is:

[0046] l s =0.83g

[0047] In this way, under the design basis that the minimum controllable suspension force is greater than the maximum uncontrollable suspension force, the movement range of the rotor is limited by adding auxiliary bearings so as to achieve stable floating of the rotor.

[0048] Furthermore, the permanent magnets are all magnetized radially.

[0049] Furthermore, three permanent magnets provide bias flux for the radial air gap under the control pole, and the bias flux has a bias flux density of 0.5B. s , the radial air gap flux density under the three permanent magnet poles is B s The bias flux generated by the three permanent magnets starts from the S pole of the permanent magnet on its corresponding permanent magnet pole, passes through the stator yoke, its adjacent control pole, auxiliary bearing, radial air gap, rotor core, radial air gap, auxiliary bearing and finally returns to the N pole of the permanent magnet on its corresponding permanent magnet pole to form a closed loop; the three-phase suspension winding is energized to generate control flux, and the control flux generated on the three control poles passes through its corresponding control pole, stator yoke, its adjacent control pole, auxiliary bearing, radial air gap, rotor core and radial air gap to form a closed path, and the maximum flux density of the control flux under the radial air gap is 0.5B s .

[0050] Furthermore, the stator yoke, three permanent magnet poles, three control poles and the rotor core part are all made of laminated silicon steel sheets.

[0051] Beneficial effects:

[0052] The present invention can compensate for the difference between the radial controllable suspension force and the uncontrollable suspension force through the intervention of the auxiliary bearing when the control pole magnetic pole area is larger than the permanent magnet pole area. Since the designed control pole magnetic pole area is larger than the permanent magnet pole area, the radial maximum controllable suspension force that can be achieved is larger than that of the traditional radial hybrid magnetic bearing with the same control pole magnetic pole area and permanent magnet pole magnetic pole area. According to this method, the thickness requirement of the required auxiliary bearing can be quickly obtained, so that the internal space of the hybrid magnetic bearing can be fully utilized without applying a larger control current, and the linear relationship between force and current can be ensured while achieving stable suspension of the rotor. The design method has the characteristics of simple control and easy implementation.

[0053] The present invention designs the control pole area to be twice the control pole area, solves the mathematical models of the controllable suspension force and the uncontrollable suspension force in the x and y directions respectively, takes the radial minimum controllable suspension force being greater than the maximum uncontrollable suspension as the design basis, and the ultimate goal is to design the thickness of the auxiliary bearing, thereby limiting the mechanical movement range of the rotor under static conditions, thereby reducing the radial uncontrollable suspension force of the rotor. The controllable suspension force of the heteropolar AC hybrid magnetic bearing designed according to this method is greater than that of the traditional heteropolar hybrid magnetic bearing with the same magnetic pole area of ​​the permanent magnet pole and the control pole, and can stably float under static conditions. BRIEF DESCRIPTION OF THE DRAWINGS

[0054] Figure 1 A radial structural schematic diagram of a heteropolar AC hybrid magnetic bearing and an auxiliary bearing parameter design method of the present invention;

[0055] Figure 2 It is a schematic diagram of the axial structure of a heteropolar AC hybrid magnetic bearing and an auxiliary bearing parameter design method of the present invention;

[0056] Figure 3 The invention discloses an equivalent magnetic circuit diagram of a heteropolar AC hybrid magnetic bearing and an auxiliary bearing parameter design method.

[0057] In the figure: (1) is the stator part, (2) is the rotor part, (3) is the stator yoke, (4) is the permanent magnet pole, (5) is the control pole, (6) is the permanent magnet, (7) is the control coil, (8) is the rotor core, (9) is the permanent magnet pole arc length, (10) is the control pole arc length, (11) is the arc spacing between the poles, (12) is the average air gap, (13) is the bias flux, (14) is the control flux, (15) is the axial thickness of the bearing, (16) is the rotor radius, (17) is the auxiliary bearing, (18) is the auxiliary bearing thickness, and (19) is the radial air gap. DETAILED DESCRIPTION

[0058] The technical solution of the present invention will be described clearly and completely below in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0059] The present invention discloses a heteropolar AC hybrid magnetic bearing and an auxiliary bearing parameter design method, see Figure 1 and Figure 2 The heteropolar AC hybrid magnetic bearing includes a stator part 1 and a rotor part 2. The stator part 1 is composed of a stator yoke 3, three permanent magnetic poles 4, three control poles 5, three permanent magnets 6, and a control coil 7. The rotor part is composed of a rotor core 8 and an auxiliary bearing 17. The three permanent magnetic poles 4 and the three control poles 5 are evenly spaced and arranged on the inner circumference of the stator yoke 3. The three permanent magnets 6 are respectively embedded in their corresponding three permanent magnetic poles (a, b, c). The control coils 7 with the same number of turns are wound on the three control poles (A, B, C). The control coils 7 are star-connected as a three-phase suspension winding. The outer wall of the auxiliary bearing 17 is attached to the inner side of the permanent magnetic poles 4 and the control poles 5.

[0060] There is an average air gap 12 between the control pole 5 and the permanent magnet pole 4 and the rotor core 8. There is a radial air gap 19 between the auxiliary bearing 17 and the rotor core 8.

[0061] Control electrode 5 area S c Equal to 2 times the area of ​​permanent magnet pole 4 S p .

[0062] The permanent magnet 6 is radially magnetized, and the stator yoke 3, the permanent magnet pole 4, the control pole 5 and the rotor core 8 are all made of laminated silicon steel sheets.

[0063] The three permanent magnets 6 provide a bias flux 13 for the radial air gap under the control pole 5. The bias flux 13 has a bias flux density of 0.5B. s , the radial air gap flux density under permanent magnet pole 4 is B s .

[0064] The bias magnetic flux 13 provided by the three permanent magnets 6 located on the three permanent magnet poles (a, b, c) starts from the S pole of the permanent magnet located on the permanent magnet pole, passes through the stator yoke, the adjacent control pole, the auxiliary bearing 17, the radial air gap 19, the rotor core 8, the radial air gap 19, the auxiliary bearing 17, and finally returns to the N pole of the permanent magnet located on the permanent magnet pole.

[0065] The three-phase suspension winding is energized to generate a control magnetic flux 14, which forms a closed path between the radial air gap 19, the three control poles, the stator yoke 3, the auxiliary bearing 17 and the radial air gap 19, and the maximum magnetic flux density of the control magnetic flux 14 under the air gap is 0.5B.s .

[0066] The specific steps of the auxiliary bearing parameter design method of the above-mentioned heteropolar AC hybrid magnetic bearing are as follows:

[0067] Step 1: Select the permanent magnet material and determine the air gap saturation flux density B s , average air gap length g, rotor outer diameter r, pole width l z , arc spacing between magnetic poles l slot .

[0068] Step 2: Calculate the winding ampere-turns Ni max The magnetomotive force F provided by the permanent magnet m :

[0069] Step 3: Assume that the rotor is subjected to a slight disturbance and produces radial displacement, and the displacement is recorded as x and y respectively, and the air gap expression under each magnetic pole can be obtained as follows:

[0070] Right now:

[0071] where g a -g C They are the air gaps between the magnetic poles and the rotor, both smaller than gl s .

[0072] Step 4: The expression of air gap reluctance under each magnetic pole is:

[0073]

[0074] Among them, S p and S c represents the magnetic pole area of ​​the corresponding permanent magnet pole and control pole, l c and l z They represent the arc length of the controlled magnetic pole and the axial thickness of the bearing, respectively. p is the permanent magnet pole arc length.

[0075] Step 5: Calculate the air gap bias flux under the permanent magnet pole and control pole:

[0076]

[0077] Among them, Φ a is the magnetic flux generated by the permanent magnet on pole a at the air gap between pole a and the rotor, Φ aC is the magnetic flux generated by the permanent magnet on pole a at pole C and the rotor air gap, Φ aB is the magnetic flux generated by the permanent magnet on pole a at pole B and the rotor air gap, and the other formulas are similar.

[0078] Step 6: To facilitate the calculation on the oxy surface, the three-phase control current located on the magnetic poles A, B, and C is transformed into two phases using Clark transformation (where i A 、i B 、i C are the original three-phase suspension winding currents, i x and i y is the equivalent current in the x-direction and y-direction after conversion):

[0079]

[0080] Right now:

[0081]

[0082] Step 7: The magnetomotive force generated by the suspension winding is:

[0083]

[0084] Step 8: Calculate the suspension flux generated by the control winding:

[0085]

[0086] Step 9: From the above formula, we can get the total flux expression of the three control poles:

[0087]

[0088] Step 10: Based on the above expression of magnetic flux, the expressions of suspension force in the x and y directions are obtained respectively:

[0089]

[0090] Step 11: Linearize the above suspension force expression to obtain:

[0091]

[0092] Then, F x and F y The displacement and control current in the equation are calculated, and the partial derivative is calculated. c Expression and l p and l c The equation of the relationship (where F x and F y are the combined forces of the controllable suspension force and the uncontrollable suspension force in the x-direction and y-direction in step nine, respectively);

[0093]

[0094] The relationship between the controllable suspension force and the uncontrollable suspension force in the x-direction and y-direction is obtained respectively:

[0095]

[0096] where F xp and F yp is the uncontrollable suspension force in the x and y directions, F xc and F yc is the controllable suspension force in the x and y directions. The mathematical models of the maximum controllable suspension force and the maximum uncontrollable suspension force are as follows:

[0097]

[0098] Step 12: By comparison, it can be seen that when the control current is the same, the controllable suspension force in the x direction is smaller than the controllable suspension force in the y direction; when the rotor has the same displacement in the x and y directions, the uncontrollable suspension force in the x direction is greater than the controllable suspension force in the y direction.

[0099] Combined with the design principle that the minimum controllable suspension force should be greater than the maximum uncontrollable suspension force, the required auxiliary bearing thickness l is obtained while ensuring that the rotor can be stably suspended. s ,Right now:

[0100]

[0101] Finally, we get l s The expression is:

[0102] l s =0.83g

[0103] Therefore, under the design basis that the minimum controllable suspension force is greater than the maximum uncontrollable suspension force, the movement range of the rotor can be limited by adding auxiliary bearings to achieve stable floating of the rotor.

[0104] The above embodiments are only for illustrating the technical concept and features of the present invention, and their purpose is to enable people familiar with the technology to understand the content of the present invention and implement it accordingly, and they cannot be used to limit the protection scope of the present invention. Any equivalent transformation or modification made according to the spirit of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for designing auxiliary bearing parameters of a heteropolar AC hybrid magnetic bearing, characterized in that: The heteropolar AC hybrid magnetic bearing comprises a stator part (1) and a rotor part (2), wherein the stator part (1) comprises a stator yoke (3), three permanent magnetic poles (4) and three control poles (5), three permanent magnets (6) are embedded in the permanent magnetic poles (4), control coils (7) with the same number of turns are wound on the three control poles (5), the control coils (7) are star-connected to form a three-phase suspension winding, and auxiliary bearings (17) are attached to the inner sides of the permanent magnetic poles (4) and the control poles (5); the rotor part comprises a rotor core (8); the area S of the control poles (5) is c Equal to twice the area S of the permanent magnet pole (4) p ; An average air gap (12) is provided between the control pole (5), the permanent magnet pole (4) and the rotor core (8), and a radial air gap (19) is provided between the auxiliary bearing (17) and the rotor core (8); Given the rotor outer diameter r, average air gap length g, saturated air gap flux density B s 、Inter-pole arc spacing l slot (11) and the axial thickness of the bearing l z (15), the control flux density and bias flux density under the control pole (5) are both equal to 0.5B s As a prerequisite, the thickness of the auxiliary bearing (17) is designed based on the minimum controllable suspension force being greater than the maximum uncontrollable suspension force, under the condition that the rotor can float under the maximum eccentricity; The permanent magnets (6) are all magnetized radially; The three permanent magnets (6) provide a bias magnetic flux (13) for the radial air gap under the control pole (5), and the bias magnetic flux (13) has a bias magnetic flux density of 0.5B. s , the radial air gap flux density under the three permanent magnet poles (4) is B s The bias magnetic flux (13) generated by the three permanent magnets respectively starts from the S pole of the permanent magnet located on the corresponding permanent magnetic pole, passes through the stator yoke, its adjacent control pole, the auxiliary bearing (17), the radial air gap (19), the rotor core (8), the radial air gap (19), the auxiliary bearing (17), and finally returns to the N pole of the permanent magnet on the corresponding permanent magnetic pole to form a closed loop; the three-phase suspension winding is energized to generate control magnetic flux, and the control magnetic flux generated on the three control poles (5) passes through its corresponding control pole, the stator yoke (3), its adjacent control pole, the auxiliary bearing (17), the radial air gap (19), the rotor core (8), and the radial air gap (19) to form a closed path, and the maximum magnetic flux density of the control magnetic flux (14) under the radial air gap is 0.5B s .

2. The auxiliary bearing parameter design method of a heteropolar AC hybrid magnetic bearing according to claim 1 is characterized in that: The specific auxiliary bearing design process is as follows: Step 1: Select the permanent magnet (6) material and determine the air gap saturation flux density B s , average air gap length g, rotor outer diameter r, axial thickness of the bearing l z , arc spacing between magnetic poles l slot ; Step 2: Calculate the winding ampere-turns Ni xmax The magnetomotive force F provided by the permanent magnet (6) m : Step 3: Assume that the rotor is subjected to a slight disturbance and produces radial displacement, and the displacement is recorded as x and y respectively. The air gap expression under each magnetic pole can be obtained as follows: Right now: Among them, g a -g C They are the air gaps between each magnetic pole and the rotor, both smaller than gl s ; Step 4: The air gap reluctance expression under each magnetic pole is: Among them, S p and S c represents the magnetic pole area of ​​the corresponding permanent magnet pole (4) and control pole (5), l c and l z They represent the control pole arc length (10) and the axial thickness of the bearing, respectively. p is the arc length of the permanent magnet pole (9), μ0 is the vacuum permeability, μ0=4π×10 -7 H / m; Step 5: Calculate the air gap bias flux under the permanent magnet pole (4) and the control pole (5): Among them, Φ a is the magnetic flux generated by the permanent magnet on pole a at the air gap between pole a and the rotor, Φ aC is the magnetic flux generated by the permanent magnet on pole a at pole C and the rotor air gap, Φ aB is the magnetic flux generated by the permanent magnet on pole a at pole B and the rotor air gap, and the other formulas are the same; Step 6: To facilitate calculation on the oxy surface, the three-phase control current on the magnetic poles A, B, and C of the three control poles 5 is transformed into two phases using Clark transformation: where i A 、i B 、i C are the original three-phase currents, i x and i y is the equivalent current in the x-direction and y-direction after conversion, that is: Step 7: The magnetomotive force generated by the winding is: Step 8: Calculate the suspension flux generated by the control winding: Step 9: From the above formula, we can get the total flux expression of the three control poles: Step 10: Based on the above expression of magnetic flux, the expressions of suspension force in the x and y directions are obtained respectively: where F x and F y are the resultant forces of the controllable suspension force and the uncontrollable suspension force in the x-direction and y-direction respectively; Step 11: Linearize the suspension force expression to obtain: Then, F x and F y The displacement and control current in the equation are calculated, and the partial derivative is calculated. c Expression and l p and l c The equation of the relationship: The relationship between the controllable suspension force and the uncontrollable suspension force in the x-direction and y-direction is obtained respectively: where F xp and F yp is the uncontrollable suspension force in the x and y directions, F xc and F yc is the controllable suspension force in the x and y directions; the mathematical models of the maximum controllable suspension force and the maximum uncontrollable suspension force are as follows: Step 12: By comparison, it can be seen that when the control current is the same, the controllable suspension force in the x direction is smaller than the controllable suspension force in the y direction; when the displacement of the rotor in the x and y directions is the same, the uncontrollable suspension force in the x direction is larger than the controllable suspension force in the y direction; Combined with the design principle that the minimum controllable suspension force should be greater than the maximum uncontrollable suspension force, the required auxiliary bearing thickness l is obtained while ensuring that the rotor can be stably suspended. s ,Right now: i xmax is the maximum current in the x direction; we get l s The expression is: l s ＝0.83g In this way, under the design basis that the minimum controllable suspension force is greater than the maximum uncontrollable suspension force, the movement range of the rotor is limited by adding auxiliary bearings so as to achieve stable floating of the rotor.

3. The auxiliary bearing parameter design method of a heteropolar AC hybrid magnetic bearing according to claim 1 or 2, characterized in that: The stator yoke (3), three permanent magnet poles (4), three control poles and the rotor core (8) are all made of laminated silicon steel sheets.

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