Parameter optimization design method for heteropole type limited rotor direct current hybrid magnetic bearing

Abstract

The invention discloses a parameter optimization design method for a heteropole limited rotor direct current hybrid magnetic bearing. Comprising a stator core, a rotor core and a rotating shaft, four control poles and four permanent magnet poles are uniformly distributed on the inner circumference of the stator core at intervals, permanent magnets are arranged on the permanent magnet poles, suspension windings are wound on the control poles, and two suspension windings on two opposite poles are respectively connected in series to form suspension windings in the X direction and the Y direction and are respectively driven by two switch power amplifiers. Firstly, an iron core and a permanent magnet material are selected, the air gap length and the magnetic pole distance are determined, and the rotor outer diameter is given; secondly, establishing a suspension force mathematical model, determining the area and arc length of a permanent magnet pole and a control pole according to the standard that controllable suspension force is greater than uncontrollable suspension force when a rotor is in a static state, and finally designing permanent magnet parameters and the ampere-turn number of a suspension winding. On the premise that the outer diameter of the rotor and the air gap length are given, the heteropole type direct-current hybrid magnetic bearing which enables the rotor to stably float in a static state and has the maximum controllable suspension force is designed.

Description

Technical Field

[0001] The invention relates to the technical field of hybrid magnetic suspension bearings, and in particular to a parameter optimization design method for a heteropolar limited-rotor direct current hybrid magnetic bearing. Background Art

[0002] The working principle of hybrid magnetic bearings is to use the uncontrollable suspension force generated by permanent magnets to achieve stable suspension of the rotor at the equilibrium position, and only when the rotor deviates from the equilibrium position, the suspension winding needs to be energized to generate controllable suspension force to pull the rotor back to the equilibrium position. Therefore, the switching amplifier required for hybrid magnetic bearings has low power consumption, low power consumption, and small size, but the suspension force density is high, which has important application value in the field of high-speed or ultra-high-speed transmission. According to the magnetic field formed by the bias flux on the rotor, hybrid magnetic bearings can be divided into heteropolar type and homopolar type. The homopolar type often adopts a double-piece structure, and the permanent magnet is axially magnetized and installed between the two pieces. However, the homopolar type has disadvantages such as long axial length and low critical speed. In contrast, heteropolar DC hybrid magnetic bearings place permanent magnets and windings in one space, with a short axial length and a high critical speed. However, the current design method of heteropolar hybrid magnetic bearings often adopts a design method in which the area of ​​the pole where the permanent magnet is located and the pole where the winding is located is equal, which limits the performance of the magnetic bearing.

[0003] As we all know, the suspension force in hybrid magnetic bearings is divided into controllable suspension force and uncontrollable suspension force. It is the controllable suspension force that affects the mechanical properties of magnetic bearings. When designing hybrid magnetic bearings, we always hope that the controllable suspension force is maximized. The current design schemes are simply to choose a balance between the controllable and uncontrollable suspension forces, that is, the control pole and permanent magnet pole area are equal. Although this can achieve the suspension function, it cannot fully reflect the technical advantages of magnetic suspension bearings in high-performance motion control systems. Summary of the invention

[0004] Purpose of the invention: In view of the existing design method of different-pole DC hybrid magnetic bearings that adopt the same area of ​​permanent magnet poles and control poles, a design method is proposed in which the area of ​​permanent magnet poles is as small as possible and the area of ​​control poles is as large as possible under the premise of ensuring stable levitation, so as to generate the maximum controllable suspension force.

[0005] Technical solution: The present invention discloses a parameter optimization design method for a heteropolar limited rotor DC hybrid magnetic bearing, comprising a stator core, a rotor core and a rotating shaft, wherein the stator core is evenly spaced with control poles and permanent magnetic poles along the inner circumference, a suspension winding is wound on the control pole, a permanent magnet is arranged on the permanent magnetic pole, and the rotor core is penetrated from the inside by the rotating shaft; there is a radial air gap between the stator core and the rotor core;

[0006] Distance between poles l dbmp The sum of the control pole and permanent magnet pole areas remains unchanged; the control pole arc length lc and permanent magnet pole arc length l Pm Not equal, and l Pm ∈[0.5l c , l c ];

[0007] When optimizing the design parameters, first select the stator core, rotor core and permanent magnet materials, determine the air gap length g, the pole distance l dbmp , given the rotor outer diameter r; secondly, establish the mathematical model of suspension force, according to the standard that the controllable suspension force is greater than the uncontrollable suspension force when the rotor is static, determine the area of ​​the permanent magnet pole and the control pole, further determine the arc length of the control pole and the permanent magnet pole, and finally design the permanent magnet parameters and the ampere-turns of the suspension winding.

[0008] Furthermore, the inner and outer polarities of each permanent magnet are the same, N on the outside and S on the inside, and the generated bias magnetic circuit passes through the permanent magnet, the stator core, the radial air gap, the control pole and the rotor core.

[0009] Furthermore, the number of the permanent magnetic poles and control poles is 4, the suspension windings Q1-Q4 are wound on the control poles, and the permanent magnetic poles with embedded permanent magnets G1-G4 are between the adjacent control poles. Q2 and Q4 are connected in series to form an X-direction suspension winding, and Q1 and Q3 are connected in series to form a Y-direction suspension winding. They are powered by two switching power amplifiers to generate a control magnetic circuit in the X direction and a control magnetic circuit in the Y direction, and are all composed of a stator core, a control pole, a radial air gap, and a rotor core.

[0010] Furthermore, the design steps are as follows:

[0011] Step 1: Analyze the magnetic circuit and build a magnetic circuit model. The control poles are A~D, the permanent magnetic poles are a~d, and the control poles A~D are wound with suspension windings Q1~Q4 respectively. R A ~R D is the air gap reluctance under the corresponding control pole A~D; R a ~R d is the air gap reluctance under the corresponding permanent magnet poles a~d; φ A ~φ D is the bias flux under the corresponding control pole A~D; φ a ~φ d is the bias flux under the corresponding permanent magnet poles a~d; φ x1 ,φ x2 ,φ y1 ,φ y2 is the control flux of the air gap corresponding to the control poles B, D, C, and A; F n is the magnetomotive force generated by the permanent magnet, NI is the ampere-turns of the suspension winding;

[0012] Step 2: Select the stator core, rotor core, permanent magnet material and radial air gap length;

[0013] Step 3: Under the condition that the outer diameter of the rotor is determined, the outer circumference of the rotor is a known quantity. Then, the virtual circle of the magnetic pole is outward through the radial air gap. Adding the radial air gap length g, which is equivalent to the known inner diameter of the magnetic pole and the virtual circumference, the distance between the magnetic poles is set to l dbmp The parameters are known, according to the permanent magnet pole arc length l Pm and the distance between the poles l dbmp Calculate the control pole arc length l c : R = r + g, r is the outer diameter of the rotor, and R is the inner diameter of the stator;

[0014] Calculate the control electrode area S c : l z is the axial thickness of the stator pole;

[0015] Calculate the permanent magnet pole area S Pm :

[0016] Step 4: Use Kirchhoff's law to find the bias flux and control flux at the air gap under the magnetic pole:

[0017]

[0018] φ n Represents the total magnetic flux generated by the permanent magnet, F n is the magnetomotive force generated by the permanent magnet, R n Represents the magnetic resistance of the permanent magnet, N x I x 、N y I y Respectively represent the ampere-turns of the suspension winding in the radial x and y directions;

[0019] Step 6: Based on Maxwell's equations, derive the suspension forces in the x and y directions:

[0020]

[0021] Step 7: Linearize the suspension force at the equilibrium position using Taylor's formula to obtain:

[0022]

[0023] Same reason

[0024] Step 8: When the current reaches the maximum value, i x =i y =I max , let the critical condition:

[0025]

[0026] Step 9: When the offset reaches the maximum value, that is, x = g, the control pole arc length l can be obtained c and permanent magnet pole arc length l Pm ,Right now:

[0027]

[0028] Furthermore, the magnetomotive force provided by the permanent magnet is determined:

[0029] F b =H p ·T p , H p is the coercive force of the permanent magnet, T p is the thickness of the permanent magnet along the magnetization direction;

[0030] Determine the ampere-turns of the suspension winding:

[0031] Beneficial effects:

[0032] The present invention proposes a method for optimizing the design of parameters of a heteropolar rotor-limited DC hybrid magnetic bearing. Under the condition that the outer diameter of the rotor is given, a method of calculating the arc length of the control pole and the permanent magnet pole according to a mathematical model is used to replace a design scheme with the same pole area. Sufficient controllable suspension force can be generated to achieve stable levitation of the rotor under static conditions. The designed heteropolar rotor-limited DC hybrid magnetic bearing has a maximum controllable maximum suspension force and good dynamic mechanical characteristics. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 The radially split structure diagram of a parameter optimization design method for a heteropolar rotor-limited DC hybrid magnetic bearing;

[0034] Figure 2 The radial bias magnetic circuit diagram of a parameter optimization design method for a heteropolar rotor-limited DC hybrid magnetic bearing;

[0035] Figure 3 The radial X-direction control magnetic circuit diagram of a parameter optimization design method for a heteropolar rotor-limited DC hybrid magnetic bearing;

[0036] Figure 4 The radial Y-direction control magnetic circuit diagram of a parameter optimization design method for a heteropolar rotor-limited DC hybrid magnetic bearing;

[0037] Figure 5 It is a specific flow chart of a parameter optimization design method for a heteropolar limited rotor DC hybrid magnetic bearing;

[0038] Figure 6 The bias flux equivalent magnetic circuit diagram of a parameter optimization design method for a heteropolar limited rotor DC hybrid magnetic bearing;

[0039] Figure 7 This is the control flux equivalent magnetic circuit diagram of a parameter optimization design method for a heteropolar limited rotor DC hybrid magnetic bearing.

[0040] Among them, 1-stator core, 2-rotor core, 3-rotating shaft, 4-control pole, 5-permanent magnet pole, 6-suspension winding, 7-permanent magnet, 8-radial air gap, 9-bias magnetic circuit, 10-X direction control magnetic circuit, 11-Y direction control magnetic circuit. DETAILED DESCRIPTION

[0041] The following is combined with Figure 1 To Attachment Figure 7 The technical solution of the present invention is further described.

[0042] The present invention discloses a parameter optimization design method for a heteropolar limited rotor DC hybrid magnetic bearing, comprising a stator core 1, a rotor core 2 and a rotating shaft 3, wherein the stator core 1 is evenly spaced with control poles 4 and permanent magnetic poles 5 along the inner circumference, a suspension winding 6 is wound on the control pole 4, and a permanent magnet 7 is arranged on the permanent magnetic pole 5. The rotor core 2 is penetrated from the inside by the rotating shaft 3; and a radial air gap 8 is provided between the stator core 1 and the rotor core 2.

[0043] The present invention sets the distance between the magnetic poles l dbmp The sum of the areas of the control pole 4 and the permanent magnet pole 5 remains unchanged. The arc length of the control pole 4 is l c Arc length l with permanent magnet pole 5 Pm Not equal, and l Pm ∈[0.5l c , l c ].

[0044] The inner and outer polarities of each permanent magnet 7 are the same, N on the outside and S on the inside. The generated bias magnetic circuit 9 passes through the permanent magnet 7, the stator core 1, the radial air gap 8, the control pole 4 and the rotor core 2.

[0045] The number of permanent magnet poles 5 and control poles 4 are both 4, the control poles 4 are wound with suspension windings 6Q1-Q4, and between each two adjacent control poles is a permanent magnet pole 5 with embedded permanent magnets 7G1-G4. Q2 and Q4 are connected in series to form an X-direction suspension winding, and Q1 and Q3 are connected in series to form a Y-direction suspension winding. They are powered by two switching power amplifiers to generate a control magnetic circuit 10 in the X direction and a control magnetic circuit 11 in the Y direction, which are all composed of a stator core 1, a control pole 4, a radial air gap 8, and a rotor core 2.

[0046] In view of the above structure, the present invention, when optimizing the parameters, calculates the arc length of the control pole 4 and the permanent magnet pole 5 according to the mathematical model when the rotor outer diameter is given. The parameter design steps are as follows:

[0047] Step 1: Analyze the magnetic circuit and build a magnetic circuit model. The control poles 4 are A to D, the permanent magnet poles 5 are a to d, and the control poles 4A to D are wound with suspension windings 6Q1 to Q4, R A ~R D is the air gap magnetic resistance under the corresponding control pole 4A~D; R a ~R d is the air gap reluctance under the corresponding permanent magnet poles 5a~d; φ A ~φ D is the bias flux under the corresponding control pole 4A~D; φ a ~φ d is the bias flux under the corresponding permanent magnet poles 5a~d; φ x1 ,φ x2 ,φ y1 ,φ y2 is the control flux of the air gap corresponding to the control poles B, D, C, and A; F n is the magnetomotive force generated by the permanent magnet 7, and NI is the ampere-turns of the suspension winding.

[0048] Step 2: Select the stator core 1, the rotor core 2, the material of the permanent magnet 6, and the length of the radial air gap 8.

[0049] Step 3: According to the arc length l of permanent magnet pole 5 Pm and the distance between the poles l dbmp Calculate the arc length l of the control electrode 4 c :

[0050] R=r+g, r is the outer diameter of the rotor, and R is the inner diameter of the stator.

[0051] Further calculate the control electrode (4) area S c :

[0052] l z is the axial thickness of the stator pole.

[0053] Permanent magnet pole (5) area S Pm :

[0054]

[0055] Step 4: Use Kirchhoff's law to calculate the bias flux and control flux at the air gap under the magnetic pole

[0056]

[0057] φ n Represents the total magnetic flux generated by the permanent magnet, F n is the magnetomotive force generated by the permanent magnet, R n Represents the magnetic resistance of the permanent magnet, N x Ix 、N y I y Respectively represent the ampere-turns of the suspension winding in the radial x and y directions.

[0058] Step 6: Based on Maxwell's equations, derive the suspension forces in the x and y directions

[0059]

[0060] Step 7: Linearize the suspension force at the equilibrium position using Taylor's formula to obtain

[0061]

[0062] Same reason

[0063] Step 8: When the current reaches the maximum value, i x =i y =I max , let the critical condition:

[0064]

[0065] Step 9: When the offset reaches the maximum value, that is, x = g, the arc length l of the control electrode 4 can be obtained c and permanent magnet pole 5 arc length l Pm ,Right now:

[0066]

[0067] Step 10: Determine the magnetomotive force provided by the permanent magnet

[0068] F b =H p ·T p , H p is the coercive force of the permanent magnet 7, T p is the thickness of the permanent magnet 7 along the magnetization direction.

[0069] Step 11: Determine the ampere-turns of the suspension winding:

[0070] 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 optimizing the design of parameters of a heteropolar rotor-limited DC hybrid magnetic bearing, characterized in that: The invention comprises a stator core (1), a rotor core (2) and a rotating shaft (3); the stator core (1) is provided with control poles (4) and permanent magnetic poles (5) uniformly spaced along the inner circumference; a suspension winding (6) is wound on the control pole (4); a permanent magnet (7) is arranged on the permanent magnetic pole (5); the rotor core (2) is penetrated from the inside by the rotating shaft (3); and a radial air gap (8) is provided between the stator core (1) and the rotor core (2); Set the distance between the poles l dbmp The sum of the magnetic pole areas of the control pole (4) and the permanent magnet pole (5) is set to be fixed, and the arc length of the control pole (4) is l c The arc length l with the permanent magnet pole (5) Pm Not equal, and l Pm ∈[0.5l c , l c ]; When optimizing the parameters, first select the materials of the stator core (1), the rotor core (2) and the permanent magnet (7), determine the radial air gap length g, the distance between the magnetic poles l dbmp , given the rotor outer diameter r; Secondly, a mathematical model of the suspension force is established. According to the standard that the controllable suspension force is greater than the uncontrollable suspension force when the rotor is static, the areas of the permanent magnet pole (5) and the control pole (4) are determined, and the arc lengths of the control pole (4) and the permanent magnet pole (5) are further determined. Finally, the permanent magnet parameters and the ampere-turns of the suspension winding are designed.

2. The method for optimizing the parameters of a heteropolar rotor-limited DC hybrid magnetic bearing according to claim 1 is characterized in that: The inner and outer polarities of each permanent magnet (7) are the same, with N on the outside and S on the inside. The generated bias magnetic circuit (9) passes through the permanent magnet (7), the stator core (1), the radial air gap (8), the control pole (4) and the rotor core (2).

3. The method for optimizing the parameters of a heteropolar rotor-limited DC hybrid magnetic bearing according to claim 2 is characterized in that: The number of the permanent magnetic poles (5) and the control poles (4) is 4, the control poles (4) are wound with suspension windings (6) Q1-Q4, between two adjacent control poles is a permanent magnetic pole (5) with embedded permanent magnets (7) G1-G4, Q2 and Q4 are connected in series to form an X-direction suspension winding, and Q1 and Q3 are connected in series to form a Y-direction suspension winding, which are powered by two switching power amplifiers to generate an X-direction control magnetic circuit (10) and a Y-direction control magnetic circuit (11), and are all composed of a stator core (1), a control pole (4), a radial air gap (8), and a rotor core (2).

4. A method for optimizing the parameters of a heteropolar rotor-limited DC hybrid magnetic bearing according to any one of claims 1 to 3, characterized in that: The steps of parameter optimization design method are as follows: Step 1: Analyze the magnetic circuit and build a magnetic circuit model. The control poles (4) are A to D, the permanent magnet poles (5) are a to d, and the control poles (4) A to D are respectively wound with suspension windings (6) Q1 to Q4, R A ~R D is the air gap reluctance under the corresponding control pole (4) A~D; R a ~R d is the air gap reluctance under the corresponding permanent magnetic poles (5) a~d; φ A ~φ D is the bias flux under the corresponding control pole (4) A~D; φ a ~φ d is the bias flux under the corresponding permanent magnet pole (5) a~d; φ x1 ,φ x2 ,φ y1 ,φ y2 is the control flux of the air gap corresponding to the control poles B, D, C, and A; F n is the magnetomotive force generated by the permanent magnet (7), NI is the ampere-turns of the suspension winding; Step 2: Select the materials of the stator core (1), the rotor core (2), the permanent magnet (7) and the length of the radial air gap (8); Step 3: Under the condition that the rotor outer diameter r is determined, the outer circumference of the rotor is a known quantity. Then, the virtual circle of the magnetic pole is outward through the radial air gap (8). Adding the length g of the radial air gap (8), it is equivalent to the known inner diameter of the magnetic pole and the virtual circumference. Then, the distance l between the magnetic poles is set. dbmp The parameters are known, according to the arc length l of the permanent magnet pole (5) Pm and the distance between the poles l dbmp Calculate the arc length l of the control electrode (4) c : R = r + g, r is the outer diameter of the rotor, and R is the inner diameter of the stator; Calculate the area S of the control electrode (4) c : l z is the axial thickness of the stator pole; Calculate the area S of the permanent magnet pole (5) Pm : Step 4: Use Kirchhoff's law to find the bias flux and control flux at the air gap under the magnetic pole: Among them, φ n Represents the total magnetic flux generated by the permanent magnet, R n Represents the magnetic resistance of the permanent magnet, N x I x 、N y I y Respectively represent the ampere-turns of the suspension winding in the radial x and y directions; Step 6: Based on Maxwell's equations, derive the suspension forces in the x and y directions: Step 7: Linearize the suspension force at the equilibrium position using Taylor's formula to obtain: Same reason Step 8: When the current reaches the maximum value, i x =i y =I max , let the critical condition: Step 9: When the offset reaches the maximum value, that is, x = g, the arc length l of the control pole (4) can be obtained c and the arc length l of the permanent magnet pole (5) Pm ,Right now:

5. The method for optimizing the parameters of a heteropolar rotor-limited DC hybrid magnetic bearing according to claim 4 is characterized in that: Determine the magnetomotive force provided by the permanent magnet: F b =H p ·T p , H p is the coercive force of the permanent magnet (7), T p is the thickness of the permanent magnet (7) along the magnetization direction; Determine the ampere-turns of the suspension winding:

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