Parameter design method for heteropole type direct current hybrid magnetic bearing

Abstract

The invention discloses a parameter design method for a heteropole type direct current hybrid magnetic bearing. Comprising a stator core, a rotor core and a rotating shaft, four control poles and four permanent magnet poles with different arc lengths are uniformly distributed in the stator core, permanent magnets are arranged in the permanent magnet poles, and control coils are wound on the control poles. The design method comprises the following steps: firstly, determining the arc length of a control pole according to the requirements of the given axial thickness of the iron core and the maximum radial controllable suspension force Fmax; secondly, the arc length of a permanent magnet pole is determined according to the inner diameter and perimeter relation of the stator core, the magnetic pole distance is fixed, and the smaller the outer diameter of the rotor core is, the smaller the area of the permanent magnet pole is; finally, an uncontrollable suspension force mathematical model Fp is established, and when the rotor offset is maximum, Fplt; and Fmax, determining the outer diameter of the rotor. According to the maximum controllable suspension force requirement, the given air gap length and the magnetic pole distance, the permanent magnet rotor can stably float in a static state, the maximum controllable suspension force is maximum, the arc length of the permanent magnet pole is minimum, and the outer diameter of the rotor core is minimum.

Description

Technical Field

[0001] The invention relates to the technical field of hybrid magnetic suspension bearings, and specifically refers to a method for designing parameters of a heteropolar DC hybrid magnetic bearing which meets the requirements of maximum controllable suspension force, can stably float, and has a minimum rotor outer diameter. Background Art

[0002] In hybrid magnetic bearings, when the rotor is in the equilibrium position, there is only the uncontrollable suspension force generated by the permanent magnet to achieve stable suspension of the rotor, and the control coil has no current; only when the rotor deviates from the equilibrium position, the control coil needs to be energized to generate a controllable suspension force to pull the rotor back to the equilibrium position. Therefore, the hybrid magnetic bearing requires a small switching amplifier, low power consumption, small size, and high suspension force density, 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, it can be divided into two types: heteropolar type and homopolar type. Among them, the homopolar type often adopts a double-piece structure, the permanent magnet is axially magnetized and installed between the two pieces, and has the disadvantages of long axial length and low critical speed. The heteropolar DC hybrid magnetic bearing is to place the permanent magnet and the winding in the same space, with a short axial length and a high critical speed. However, when designing it, the design method of using the same pole area of ​​the permanent magnet and the winding is often adopted. As we all know, the force generated by the pole where the permanent magnet is located on the rotor is an uncontrollable suspension force, while the pole where the winding is located generates a controllable suspension force. In application requirements, it is always hoped that the larger the controllable suspension force is, the more the performance superiority of the magnetic bearing can be reflected. Although increasing the control pole area and reducing the permanent magnet pole area can increase the controllable suspension force, the uncontrollable suspension force will also increase accordingly. Therefore, the current design method of using the pole area of ​​the permanent magnet to be equal to the pole area of ​​the winding is difficult to reflect the technical advantages of the heteropolar DC hybrid magnetic bearing.

[0003] Therefore, in order to solve the above technical problems, the present invention proposes a parameter design method for a heteropolar DC hybrid magnetic bearing. On the premise of meeting the maximum suspension force requirements and being able to float stably, a reasonable arc length of the permanent magnet pole and the control pole is designed to minimize the rotor outer diameter and maximize the suspension force density. Summary of the invention

[0004] Purpose of the invention: In view of the existing design method of heteropolar DC hybrid magnetic bearings that adopts the same area of ​​control poles and permanent magnet poles, a parameter design method for heteropolar DC hybrid magnetic bearings is proposed. Under the premise of ensuring stable levitation, the maximum controllable suspension force requirements are met, and reasonable arc lengths of permanent magnet poles and control poles are designed to minimize the outer diameter of the rotor and maximize the suspension force density.

[0005] Technical solution: The present invention discloses a method for designing parameters of a heteropolar DC hybrid magnetic bearing, which comprises a stator core, a rotor core and a rotating shaft. The stator core is provided with control poles and permanent magnetic poles at intervals along the inner circumference, a control coil is wound on the control pole, and a permanent magnet is arranged on the permanent magnetic pole; the rotating shaft runs through the rotor core; and a radial air gap is provided between the stator core and the rotor core;

[0006] Set the distance l between the control pole and the permanent magnet pole slot Fixed and controlled pole arc length l c and permanent magnet pole arc length l p Not equal, and l p ∈[0.5l c , l c ].

[0007] The parameter design method is: first, according to the given core axial thickness and radial maximum controllable suspension force F max The demand is to determine the control pole arc length; secondly, the permanent magnet pole arc length is determined according to the relationship between the inner diameter and circumference of the stator core, where the distance between the poles is fixed, and the smaller the outer diameter of the rotor core, the smaller the permanent magnet pole area; finally, the mathematical model of the uncontrollable suspension force F is established p , when the rotor displacement is maximum, F p <F max , determine the outer diameter r of the rotor core.

[0008] Furthermore, the control coils K1-K4 wound on the control poles, K1 and K3, K2 and K4 are connected in series to form suspension windings in the X and Y directions respectively, and are powered by two switching amplifiers to generate control magnetic fluxes in the X and Y directions.

[0009] Further, the parameter design steps are as follows:

[0010] 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 coils K1~K4 are wound around the control poles A~D respectively. A ~R D is the air gap reluctance under the control pole; R a ~R d is the air gap reluctance under the permanent magnet pole; φ A ~φ D is the bias flux under the control pole; φ a ~φ d is the bias flux under the permanent magnet pole; φ x1 ,φ x2 ,φ y1 ,φ y2 It is the control magnetic flux at the air gap under the control poles A~D;

[0011] Step 2: Select the stator core, rotor core, permanent magnet material, radial air gap length and axial length l of the stator core and rotor core z , according to the maximum controllable suspension force requirement F max , determine the control pole area: B s is the air gap saturation flux density, μ0 is the vacuum permeability; further obtain the control pole arc length l c :

[0012] Step 3: According to the control pole arc length l c and the distance between the poles l slot Calculate the permanent magnet pole arc length l p : r is the outer diameter of the rotor core;

[0013] Step 4: Establish uncontrollable suspension force model: Among them, F n is the magnetomotive force generated by the permanent magnet;

[0014] Step 5: When the offset reaches the maximum value, that is, x = g0, the uncontrollable suspension force F p <F max , the outer diameter r of the rotor core is obtained:

[0015] Furthermore, the coil parameters are controlled Permanent magnet 7 parameter F b =H p T p , H p is the coercive force of the permanent magnet 7, T p is the radial magnetization length of the permanent magnet 7.

[0016] Beneficial effects:

[0017] The present invention is aimed at a heteropolar DC hybrid magnetic bearing with unequal arc lengths of control poles and permanent magnet poles, and proposes a method to meet the maximum controllable suspension force requirement under the premise of ensuring stable levitation, design reasonable arc lengths of permanent magnet poles and control poles, minimize the outer diameter of the rotor, maximize the controllable suspension force, maximize the suspension force density, fully utilize materials, and effectively improve the performance of the magnetic bearing.

[0018] The present invention sets the distance between magnetic poles to be fixed, because the formula for determining the arc length of the permanent magnetic poles contains two variables, the outer diameter of the rotor and the distance between magnetic poles. By setting the distance between magnetic poles to be fixed, the outer diameter of the rotor can be calculated. In addition, the arc lengths of the control pole and the permanent magnetic pole are set to be unequal, so that the maximum controllable suspension force is greater. The arc length of the permanent magnetic pole is set between 0.5 and 1 control pole. The conventional permanent magnetic pole and control pole arc length are in a 1:1 relationship, which makes it difficult to reflect the technical advantages of heteropolar DC hybrid magnetic bearings. Therefore, the arc length of the permanent magnetic pole of the present invention is less than the arc length of the control pole, but cannot be less than 0.5 times, otherwise the problem of unsaturated air gap magnetic density will occur. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 A structural diagram of a method for designing parameters of a heteropolar DC hybrid magnetic bearing according to the present invention;

[0020] Figure 2 A bias magnetic circuit diagram of a method for designing parameters of a heteropolar DC hybrid magnetic bearing according to the present invention;

[0021] Figure 3 It is an X-direction control magnetic circuit diagram of a method for designing parameters of a heteropolar DC hybrid magnetic bearing according to the present invention;

[0022] Figure 4 A Y-direction control magnetic circuit diagram of a method for designing parameters of a heteropolar DC hybrid magnetic bearing according to the present invention;

[0023] Figure 5 It is a bias flux equivalent magnetic circuit diagram of a method for designing parameters of a heteropolar DC hybrid magnetic bearing according to the present invention;

[0024] Figure 6 This is an equivalent magnetic circuit diagram of the controlled magnetic flux of a method for designing parameters of a heteropolar DC hybrid magnetic bearing according to the present invention. DETAILED DESCRIPTION

[0025] The present invention will be further described below in conjunction with the accompanying drawings. The following embodiments are only used to more clearly illustrate the technical solution of the present invention, and cannot be used to limit the protection scope of the present invention.

[0026] The present invention discloses a parameter design method for a heteropolar DC hybrid magnetic bearing. Specifically, the heteropolar DC hybrid magnetic bearing 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 at intervals along the inner circumference. A control coil 6 is wound on the control pole 4, and a permanent magnet 7 is arranged on the permanent magnetic pole 5. The rotating shaft 3 is penetrated inside the rotor core 2; and a radial air gap 8 is provided between the stator core 1 and the rotor core 2.

[0027] The distance l between the control pole 4 and the permanent magnet pole 5 slot Fixed and unchanged.

[0028] Control electrode 4 arc length lc Arc length l with permanent magnet pole 5 p Not equal, and l p ∈[0.5l c , l c ].

[0029] The control coils 6K1-K4 wound on the control pole 4, the relative K1 and K3, K2 and K4 are connected in series to form X and Y direction suspension windings, which are powered by two switching power amplifiers to generate X and Y direction control fluxes 10 and 12.

[0030] The design steps are as follows:

[0031] Step 1: Analyze the magnetic circuit and build a magnetic circuit model. The control pole 4 is A~D, the permanent magnet pole 5 is a~d, and the control pole 4A~D is wound with control coils 6K1~K4 respectively. A ~R D is the air gap reluctance under the control pole 4; R a ~R d is the air gap reluctance under the permanent magnet pole 5; φ A ~φ D is the bias flux under the control pole 4; φ a ~φ d is the bias flux under the permanent magnet pole 5; φ x1 ,φ x2 ,φ y1 ,φ y2 It is the control magnetic flux at the air gap under the control poles 4A~D.

[0032] Step 2: Select the stator core 1, rotor core 2, permanent magnet 7 material, radial air gap 8 length and axial length l of stator core 1 and rotor core 2 z , according to the maximum controllable suspension force requirement F max , determine the area of ​​control electrode 4: B s is the air gap saturation flux density, μ0 is the vacuum permeability.

[0033] The arc length l of the control electrode 4 can be further obtained c :

[0034] Step 3: Use Kirchhoff's law to find the bias flux at the air gap under each magnetic pole:

[0035]

[0036] φ n is the total magnetic flux generated by the permanent magnet, just to show the calculation formula of magnetic flux.

[0037] And the control magnetic flux at the air gap under the control poles 4A~D:

[0038]

[0039] Ni x 、Ni y are the ampere-turns of the control coil in the X and Y directions respectively.

[0040] Step 4: Based on Maxwell's equations, derive the suspension forces in the X and Y directions:

[0041]

[0042] Step 5: Without considering gravity, the mathematical models of the suspension forces in the X and Y directions are the same. Taking the X direction as an example, the suspension force F x Using Taylor's formula to linearize the equilibrium position, we can get:

[0043]

[0044] F n is the magnetomotive force of the permanent magnet, and N is the number of coil turns.

[0045] Suspension force F in the Y direction y Same reason.

[0046] Step 6: According to the arc length l of the control electrode 4 c The distance between the poles is 11l slot Calculate the arc length l of permanent magnet pole 5 p :

[0047] r is the outer diameter of the rotor core.

[0048] Step 7: Combining the previous two steps, we get the uncontrollable suspension force model:

[0049]

[0050] Step 8: When the offset reaches the maximum value, that is, x = g0, the uncontrollable suspension force F p <F max , we can get the outer diameter of rotor core 2:

[0051]

[0052] Step 9: Determine the parameters of control coil 6

[0053] Determine the permanent magnet 7 parameter F b =H p T p , H p is the coercive force of the permanent magnet 7, T p is the radial magnetization length of the permanent magnet 7.

[0054] 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 parameters of a heteropolar DC hybrid magnetic bearing, characterized in that: The heteropolar DC hybrid magnetic bearing 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) spaced apart along the inner circumference; a control coil (6) is wound around the control pole (4); and a permanent magnet (7) is arranged on the permanent magnetic pole (5); the rotating shaft (3) is passed through the rotor core (2); and a radial air gap (8) is provided between the stator core (1) and the rotor core (2); The distance (11) between the control pole (4) and the permanent magnet pole (5) is set to l slot Fixed, and the arc length of the control pole (4) l c The arc length l with the permanent magnet pole (5) p Not equal, and l p ∈[0.5l c , l c ]; The parameter design method is: first, according to the given core axial thickness and radial maximum controllable suspension force F max The arc length of the control pole (4) is determined according to the demand; secondly, the arc length of the permanent magnet pole (5) is determined according to the relationship between the inner diameter and the circumference of the stator core (1), wherein the distance between the magnetic poles (11) is fixed, and the smaller the outer diameter of the rotor core (2), the smaller the area of ​​the permanent magnet pole (5); finally, the mathematical model of the uncontrollable suspension force F is established. p , when the rotor displacement is maximum, F p <F max , determine the outer diameter r of the rotor core (2).

2. A method for designing parameters of a heteropolar DC hybrid magnetic bearing according to claim 1, characterized in that: The control coils (6) K1-K4 wound on the control pole (4), K1 and K3, K2 and K4 are connected in series to form suspension windings in the X and Y directions respectively, and are powered by two switching power amplifiers to generate control magnetic fluxes in the X and Y directions respectively.

3. A method for designing parameters of a heteropolar DC hybrid magnetic bearing according to claim 1 or 2, characterized in that: The specific steps of parameter 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 control coils (6) K1 to K4, R A ~R D is the air gap reluctance under the control pole (4); R a ~R d is the air gap reluctance under the permanent magnet pole (5); A ~φ D is the bias flux under the control pole (4); φ a ~φ d is the bias flux under the permanent magnet pole (5); φ x1 ,φ x2 ,φ y1 ,φ y2 is the control magnetic flux at the air gap under the control poles (4) A to D; Step 2: Select the materials of the stator core (1), the rotor core (2), the permanent magnet (7), the length of the radial air gap (8), and the axial length l of the stator core (1) and the rotor core (2). z , according to the maximum controllable suspension force requirement F max , determine the control electrode (4) area S c : Among them, B s is the air gap saturation flux density, μ0 is the vacuum permeability; Further obtain the arc length l of the control electrode (4) c : Step 3: According to the arc length l of the control electrode (4) c and the distance between the poles (11) l slot , calculate the arc length l of the permanent magnet pole (5) p : r is the outer diameter of the rotor core; Step 4: When no current is applied to the winding and only the permanent magnet acts, an uncontrollable suspension force model is established: where F n is the magnetomotive force generated by the permanent magnet; Step 5: When the offset reaches the maximum value, that is, x = g0, the uncontrollable suspension force F p <F max , the outer diameter r of the rotor core (2) is obtained as:

4. A method for designing parameters of a heteropolar DC hybrid magnetic bearing according to claim 3, characterized in that: Control coil (6) parameters Permanent magnet (7) parameter F b =H p T p , H p is the coercive force of the permanent magnet (7), T p is the radial magnetization length of the permanent magnet (7).

Images