A method for designing parameters of a heteropolar direct-current hybrid magnetic bearing

Abstract

This invention discloses a parameter design method for a heteropolar DC hybrid magnetic bearing. It includes stator and rotor cores and a shaft. The stator core contains four control poles and four permanent magnet poles of varying arc lengths. Permanent magnets are placed inside the permanent magnet poles, and control coils are wound around the control poles. The design method is as follows: first, based on the given axial thickness of the core and the maximum controllable radial levitation force... F max First, the control pole arc length is determined based on the requirements. Second, the permanent magnet pole arc length is determined based on the relationship between the inner diameter and circumference of the stator core, where the pole spacing is fixed, and the smaller the outer diameter of the rotor core, the smaller the permanent magnet pole area. Finally, a mathematical model of the uncontrollable levitation force is established. F p When the rotor offset is at its maximum, F p < F max The rotor outer diameter is determined. Based on the maximum controllable levitation force requirement and a given air gap length and magnetic pole distance, this invention enables stable buoyancy under static conditions, maximizing the maximum controllable levitation force, minimizing the permanent magnet pole arc length, and minimizing the rotor core outer diameter.

Description

Technical Field

[0001] This invention relates to the field of hybrid magnetic levitation bearing technology, specifically to a parameter design method for a heteropolar DC hybrid magnetic bearing that meets the requirements of maximum controllable levitation force, can stably float, and has the smallest rotor outer diameter. Background Technology

[0002] In hybrid magnetic bearings, when the rotor is in the equilibrium position, only the uncontrollable levitation force generated by the permanent magnet achieves stable rotor levitation, and the control coil has no current. Only when the rotor deviates from the equilibrium position does the control coil need to be energized to generate a controllable levitation force to pull the rotor back to the equilibrium position. Therefore, hybrid magnetic bearings require low-power switching amplifiers, have low power consumption, small size, and high levitation force density, making them of significant application value in high-speed or ultra-high-speed transmission fields. According to the magnetic field formed on the rotor by the bias flux, they can be divided into two types: opposite-pole and same-pole. The same-pole type often adopts a double-plate structure, with the permanent magnet axially magnetized and installed between the two plates. It has the disadvantages of long axial length and low critical speed. On the other hand, the opposite-pole DC hybrid magnetic bearing places the permanent magnet and the winding in the same space, with a short axial length and a high critical speed. However, in its design, it is often designed with the pole of the permanent magnet and the pole area of ​​the winding having the same area. As is well known, the force generated by the permanent magnet pole on the rotor is an uncontrollable levitation force, while the force generated by the winding pole is a controllable levitation force. In application requirements, it is always desirable to have a larger controllable levitation force, which better reflects the performance superiority of the magnetic bearing. Although increasing the control pole area and decreasing the permanent magnet pole area can increase the controllable levitation force, the uncontrollable levitation force will also increase accordingly. Therefore, the current design method of using equal areas of permanent magnet pole area and winding pole area is difficult to reflect the technical advantages of dissimilar DC hybrid magnetic bearings.

[0003] Therefore, in order to solve the above-mentioned technical problems, this invention proposes a parameter design method for a heteropolar DC hybrid magnetic bearing. Under the premise of meeting the maximum levitation force requirement and being able to float stably, a reasonable permanent magnet pole and control pole arc length are designed to minimize the rotor outer diameter and maximize the levitation force density. Summary of the Invention

[0004] Purpose of the invention: In view of the existing design method of using the same area for the control pole and permanent magnet pole of the heteropolar DC hybrid magnetic bearing, this invention proposes a parameter design method for heteropolar DC hybrid magnetic bearing. Under the premise of ensuring stable buoyancy, this method meets the requirement of maximum controllable levitation force by designing reasonable arc lengths for the permanent magnet pole and the control pole, so as to minimize the outer diameter of the rotor and maximize the levitation force density.

[0005] Technical solution: This invention discloses a parameter design method for a heteropolar DC hybrid magnetic bearing. The heteropolar DC hybrid magnetic bearing includes a stator core, a rotor core, and a shaft. The stator core has control poles and permanent magnet poles distributed at intervals along its inner circumference. Control coils are wound on the control poles, and permanent magnets are placed on the permanent magnet poles. The rotor core has the shaft running through it. There is a radial air gap between the stator core and the rotor core.

[0006] Set the distance l between the control pole and the permanent magnet pole. slot The polar arc length l is kept constant and controlled. c With permanent magnet pole arc length l p They are not equal, and l p ∈[0.5l c , l c ].

[0007] The parameter design method is as follows: First, based on the given axial thickness of the iron core and the maximum controllable radial levitation force F... max First, determine the control pole arc length based on the requirements; second, determine the permanent magnet pole arc length based on the relationship between the stator core inner diameter and circumference, where the distance between magnetic poles is fixed, and the smaller the rotor core outer diameter, the smaller the permanent magnet pole area; finally, establish a mathematical model F for the uncontrollable levitation force. p When the rotor offset is at its 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 pole, with K1 and K3, and K2 and K4 respectively connected in series to form floating windings in the X and Y directions, are powered by two switching power amplifiers to generate control magnetic flux in the X and Y directions.

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

[0010] Step 1: Perform magnetic circuit analysis and construct a magnetic circuit model. The control poles are A to D, and the permanent magnet poles are a to d. Control coils K1 to K4 are wound around the control poles A to D respectively. A ~R D To control the air gap reluctance at the control pole; R a ~R d The air gap reluctance under the permanent magnet pole; φ A ~φ D The bias flux under the control pole; φ a ~φ d The bias flux under the permanent magnet pole; φ x1 φ x2 φ y1 φ y2 To control the control magnetic flux at the air gap below poles A to D;

[0011] Step 2: Select the stator core, rotor core, permanent magnet materials, radial air gap length, and axial length l of the stator core and rotor core. z According to the maximum controllable levitation force requirement F max Determine the control electrode area: B s Let μ0 be the air gap saturation magnetic flux density and μ0 be the free permeability; further, the control pole arc length l is obtained. c :

[0012] Step 3: Based on the control arc length l c Distance between magnetic 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 an uncontrollable levitation force model: Where F n The magnetomotive force generated by the permanent magnet;

[0014] Step 5: When the offset reaches its maximum value, i.e., x = g0, the uncontrollable levitation force F p <F max The outer diameter r of the rotor core is obtained as follows:

[0015] Furthermore, control the coil parameters Permanent magnet 7 parameters F b =H p T p H p For the coercivity of permanent magnet 7, T p The radial magnetization length of permanent magnet 7.

[0016] Beneficial effects:

[0017] This invention addresses the issue of heteropole DC hybrid magnetic bearings with unequal arc lengths of control poles and permanent magnet poles. It proposes a method that, while ensuring stable buoyancy, satisfies the requirement for maximum controllable levitation force by designing reasonable arc lengths of permanent magnet poles and control poles. This minimizes the rotor's outer diameter, maximizes the controllable levitation force and levitation force density, fully utilizes materials, and effectively improves the performance of the magnetic bearing.

[0018] This invention sets the distance between magnetic poles to a constant value. Since the formula for determining the arc length of the permanent magnet pole includes two variables—the rotor outer diameter and the distance between magnetic poles—keeping the distance constant allows for the calculation of the rotor outer diameter. Furthermore, setting the arc lengths of the control stage and the permanent magnet poles to be unequal increases the maximum controllable levitation force. The arc length of the permanent magnet pole is set between 0.5 and 1 control pole length. The conventional 1:1 ratio of permanent magnet pole to control pole arc lengths makes it difficult to demonstrate the technical advantages of the dissimilar DC hybrid magnetic bearing. Therefore, in this invention, the arc length of the permanent magnet pole is smaller than the arc length of the control pole, but not less than 0.5 times, otherwise, the problem of unsaturated air gap magnetic flux density will occur. Attached Figure Description

[0019] Figure 1 This is a structural diagram of a parameter design method for a heteropolar DC hybrid magnetic bearing according to the present invention;

[0020] Figure 2 This is a bias magnetic circuit diagram of a parameter design method for a heteropolar DC hybrid magnetic bearing according to the present invention;

[0021] Figure 3 This is the X-direction control magnetic circuit diagram of the parameter design method for a heteropolar DC hybrid magnetic bearing of the present invention;

[0022] Figure 4 This is a Y-direction control magnetic circuit diagram for a parameter design method of a heteropolar DC hybrid magnetic bearing according to the present invention.

[0023] Figure 5 The bias flux equivalent magnetic circuit diagram is provided for the parameter design method of a heteropolar DC hybrid magnetic bearing of the present invention.

[0024] Figure 6 This invention provides an equivalent magnetic circuit diagram of the control flux for a parameter design method of a heteropolar DC hybrid magnetic bearing. Detailed Implementation

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

[0026] This invention discloses a parameter design method for a heteropolar DC hybrid magnetic bearing. Specifically, the heteropolar DC hybrid magnetic bearing includes a stator core 1, a rotor core 2, and a shaft 3. The stator core 1 has control poles 4 and permanent magnet poles 5 spaced along its inner circumference. Control coils 6 are wound on the control poles 4, and permanent magnets 7 are mounted on the permanent magnet poles 5. The rotor core 2 penetrates the shaft 3. A radial air gap 8 exists 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 unchanging.

[0028] Control pole 4 arc length lc With permanent magnet pole 5 arc length l p They are not equal, and l p ∈[0.5l c , l c ].

[0029] The control coils 6K1-K4 wound on the control pole 4 are connected in series with K1 and K3, and K2 and K4 respectively to form floating windings in the X and Y directions. They are powered by two switching power amplifiers to generate control magnetic fluxes 10 and 12 in the X and Y directions.

[0030] The design steps are as follows:

[0031] Step 1: Perform magnetic circuit analysis and construct a magnetic circuit model. Control poles 4 are designated A to D, and permanent magnet poles 5 are designated a to d. Control coils 6K1 to K4 are wound around control poles 4A to D respectively. A ~R D To control the air gap reluctance under pole 4; R a ~R d The air gap reluctance under permanent magnet pole 5; φ A ~φ D To control the bias flux under pole 4; φ a ~φ d The bias flux under permanent magnet pole 5; φ x1 φ x2 φ y1 φ y2 This is the control magnetic flux at the air gap below control poles 4A to D.

[0032] Step 2: Select the materials for stator core 1, rotor core 2, and permanent magnet 7; the length of radial air gap 8; and the axial length l of stator core 1 and rotor core 2. z According to the maximum controllable levitation force requirement F max Determine the area of ​​control electrode 4: B s denoted as air gap saturation magnetic flux density, and μ0 as vacuum permeability.

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

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

[0035]

[0036] φ n It is the total magnetic flux generated by the permanent magnet, used only to illustrate the formula for calculating magnetic flux.

[0037] And the control flux at the air gap below control poles 4A to D:

[0038]

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

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

[0041]

[0042] Step 5: Without considering gravity, the mathematical models for levitation force in the X and Y directions are consistent. Taking the X direction as an example, the levitation force F... x Linearization using Taylor's formula at the equilibrium position yields:

[0043]

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

[0045] The levitation force F in the Y direction y Similarly.

[0046] Step 6: Based on the arc length l of control electrode 4 c Distance between magnetic poles 11l slot Calculate the arc length l of the permanent magnet pole 5 p :

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

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

[0049]

[0050] Step 8: When the offset reaches its maximum value, i.e., x = g0, the uncontrollable levitation force F p <F max The outer diameter of rotor core 2 can be obtained as follows:

[0051]

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

[0053] Determine the 7 parameters F of the permanent magnet b =H p T p H p For the coercivity of permanent magnet 7, T p The radial magnetization length of permanent magnet 7.

[0054] The above embodiments are only for illustrating the technical concept and features of the present invention, and are intended to enable those skilled in the art to understand the content of the present invention and implement it accordingly. They should not be construed as limiting the scope of protection of the present invention. All equivalent transformations or modifications made in accordance with the spirit and essence of the present invention should be covered within the scope of protection 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 includes a stator core (1), a rotor core (2), and a shaft (3). The stator core (1) has control poles (4) and permanent magnet poles (5) spaced along its inner circumference. Control coils (6) are wound on the control poles (4), and permanent magnets (7) are placed on the permanent magnet poles (5). The rotor core (2) passes through the shaft (3). There is a radial air gap (8) between the stator core (1) and the rotor core (2). Set the distance (11) between the control pole (4) and the permanent magnet pole (5). slot The control pole (4) arc length l remains constant. c Arc length l of permanent magnet pole (5) p They are not equal, and l p ∈[0.5l c , l c ]; The parameter design method is as follows: First, based on the given axial thickness of the iron core and the maximum controllable radial levitation force F... max First, determine the arc length of the control pole (4) according to the requirements; second, determine the arc length of the permanent magnet pole (5) according to the relationship between the inner diameter and circumference of the stator core (1), where 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, establish the mathematical model F of the uncontrollable levitation force. p When the rotor offset is at its maximum, F p <F max Determine the outer diameter r of the rotor core (2); The specific steps of the parameter design method are as follows: Step 1: Perform magnetic circuit analysis and construct a magnetic circuit model. The control poles (4) are A~D, and the permanent magnet poles (5) are a~d. Control coils (6) K1~K4 are wound around the control poles (4) A~D respectively. A ~R D The air gap reluctance is controlled by the pole (4); R a ~R d The air gap reluctance under the permanent magnet pole (5); The bias flux under the control pole (4); The bias flux under the permanent magnet pole (5); , , , The control flux at the air gap below the control pole (4) A~D; Step 2: Select the materials for the stator core (1), rotor core (2), and permanent magnet (7), the length of the radial air gap (8), and the axial length l of the stator core (1) and rotor core (2). z According to the maximum controllable levitation force requirement F max Determine the area S of the control electrode (4) c : Among them, B s denoted as air gap saturation magnetic flux density, and μ0 as vacuum permeability; Further, the arc length l of the control electrode (4) is obtained ｃ : ; Step 3: Based on the arc length l of the control pole (4) c Distance between magnetic poles (11) l slot The arc length l of the permanent magnet pole (5) was calculated. p : r is the outer diameter of the rotor core; Fourth step: when winding is not added current, only under the action of permanent magnet, establish uncontrolled suspension force model: Wherein The magnetic motive force generated by the permanent magnet; Fifth step: when the offset reaches the maximum value, i.e. x = g0, the uncontrolled suspension force F p <F max , the rotor core (2) outer diameter r: .

2. The parameter design method of the heteropolar DC hybrid magnetic bearing according to claim 1, characterized in that, The control coils (6) K1-K4 wound on the control pole (4) are connected in series with K1 and K3, and K2 and K4 respectively to form floating windings in the X and Y directions. They are powered by two switching power amplifiers to generate control magnetic flux in the X and Y directions respectively.

3. The method of claim 1, wherein the method further comprises: Controlling the parameters of the coil (6) Controlling the parameters of the permanent magnet (7) H p is the coercive force of the permanent magnet (7), T p is the radial magnetization length of the permanent magnet (7).

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