CN100406760C

CN100406760C - A design method of permanent magnetic bias axial magnetic bearing

Info

Publication number: CN100406760C
Application number: CNB2006101142700A
Authority: CN
Inventors: 房建成; 孙津济; 王曦; 杨磊
Original assignee: Beihang University
Current assignee: Beihang University
Priority date: 2006-11-03
Filing date: 2006-11-03
Publication date: 2008-07-30
Anticipated expiration: 2026-11-03
Also published as: CN1945037A

Abstract

The design method of axial magnetic bearing with permanent magnetic bias has the displacement rigidity of the magnetic bearing as main consideration, and the maximum bearing capacity, saturation magnetic induction and tankful rate as restraint conditions. Compared with available design method with optimal work point of the permanent magnet as target, the method of the present invention has the advantages of easy control of radial magnetic bearing, reasonable permanent magnet size, high accuracy, and being simple and practical. The design philosophy of the present invention may be used in design of different kinds of axial magnetic bearing with permanent magnetic bias.

Description

A design method of permanent magnetic bias axial magnetic bearing

技术领域 technical field

本发明涉及一种非接触磁悬浮轴承的设计方法，特别是一种磁悬浮飞轮、磁悬浮控制力矩陀螺等需要磁悬浮支承的装置用永磁偏置轴向磁轴承的设计方法，其设计思想可作为各类永磁偏置轴向磁轴承的设计。The invention relates to a design method of a non-contact magnetic suspension bearing, in particular to a design method of a permanent magnetic bias axial magnetic bearing for devices requiring magnetic suspension support such as a magnetic suspension flywheel and a magnetic suspension control moment gyroscope. Design of permanent magnet offset axial magnetic bearings.

背景技术 Background technique

磁悬浮轴承分纯电磁式和永磁偏置加电磁控制的混合式磁悬浮轴承，前者使用电流大、功耗大，永磁偏置加电磁控制的混合式磁悬浮轴承，永磁体产生的磁场承担主要的承载力，电磁磁场提供辅助的调节承载力，因而这种轴承可大大减小控制电流，降低损耗。常用的磁轴承控制方式采用的是传统的PID控制方式，实现该种方式的控制器参数由轴承刚度与阻尼来确定，经过大量实践证明，为使得磁轴承具有优良的特性，应使轴承刚度与其位移刚度在同一个数量级上，因此磁轴承的位移刚度对于磁轴承的控制而言至关重要。现有磁轴承的设计方法均利用永磁体最佳工作点进行设计，目的是使永磁体体积最小，但是通过这种方法计算得到的永磁体尺寸往往不太合理，而且导致加工困难，由于没有考虑位移刚度对控制系统的影响，因而现有设计方法存在准确度差、难以控制的缺陷。Magnetic suspension bearings are divided into pure electromagnetic bearings and hybrid magnetic suspension bearings with permanent magnetic bias and electromagnetic control. The former uses large current and consumes a lot of power, and the hybrid magnetic suspension bearings with permanent magnetic bias and electromagnetic control. The magnetic field generated by the permanent magnet bears the main load. Bearing capacity, the electromagnetic field provides auxiliary adjustment bearing capacity, so this kind of bearing can greatly reduce the control current and reduce the loss. The commonly used magnetic bearing control method adopts the traditional PID control method. The controller parameters to realize this method are determined by the bearing stiffness and damping. After a lot of practice, it has been proved that in order to make the magnetic bearing have excellent characteristics, the bearing stiffness should be matched with the The displacement stiffness is on the same order of magnitude, so the displacement stiffness of the magnetic bearing is crucial for the control of the magnetic bearing. The existing design methods of magnetic bearings all use the best working point of the permanent magnet to design, the purpose is to minimize the volume of the permanent magnet, but the size of the permanent magnet calculated by this method is often unreasonable, and it leads to processing difficulties. The impact of displacement stiffness on the control system, so the existing design methods have the defects of poor accuracy and difficult control.

发明内容 Contents of the invention

本发明的技术解决问题是：克服现有技术的不足，提供一种永磁偏置轴向磁轴承的设计方法，该方法准确度高，易于控制。The technical problem of the present invention is to overcome the deficiencies of the prior art and provide a design method for a permanent magnetic bias axial magnetic bearing, which has high accuracy and is easy to control.

本发明的技术解决方案是：一种永磁偏置轴向磁轴承的设计方法，需要确定：轴承体长度L、槽口宽度L_c、永磁体轴向长度h_pm、内导磁环内径D_nn、内导磁环外径D_nw(即永磁体外径D_pm1)、外导磁环外径D_ww、外导磁环内径D_wn、推力盘内径D_t2、推力盘外径D_t1、推力盘轴向长度L_t、永磁体外径D_pm1、导磁轭厚度h以及线圈匝数N，The technical solution of the present invention is: a design method of a permanent magnet bias axial magnetic bearing, which needs to be determined: the length L of the bearing body, the width L _c of the notch, the axial length h _pm of the permanent magnet, and the inner diameter D of the inner magnetic ring _nn , the outer diameter of the inner magnetic ring D _nw (that is, the outer diameter of the permanent magnet D _pm1 ), the outer diameter of the outer magnetic ring D _ww , the inner diameter of the outer magnetic ring D _wn , the inner diameter of the thrust disc D _t2 , the outer diameter of the thrust disc D _t1 , Thrust disk axial length L _t , permanent magnet outer diameter D _pm1 , magnetic yoke thickness h and coil turns N,

其特征在于：该方法基于磁轴承的位移刚度K_x，其具体步骤如下：It is characterized in that: the method is based on the displacement stiffness K _x of the magnetic bearing, and its specific steps are as follows:

(1)根据所需磁悬浮支承的装置的指标要求设定转子转速n和最大承载力F_max、根据功耗要求设定静态悬浮电流i，根据现有加工水平设定气隙长度δ、根据现有磁轴承控制器的要求设定磁轴承的位移刚度K_x、根据磁场分析设定漏磁系数σ、根据所选轴承体材料的磁化特性设定饱和磁密B_s (1) Set the rotor speed n and the maximum bearing capacity F _max according to the index requirements of the required magnetic suspension support device, set the static levitation current i according to the power consumption requirements, set the air gap length δ according to the existing processing level, and set According to the requirements of the magnetic bearing controller, set the displacement stiffness K _x of the magnetic bearing, set the magnetic leakage coefficient σ according to the magnetic field analysis, and set the saturation flux density B _s according to the magnetization characteristics of the selected bearing body material

(2)根据转子转速n和材料强度确定推力盘内径D_t2，考虑到气隙边缘效应确定轴向磁轴承内导磁环内径D_nn；(2) Determine the inner diameter D _t2 of the thrust disc according to the rotor speed n and the material strength, and determine the inner diameter D _nn of the inner magnetic ring of the axial magnetic bearing in consideration of the edge effect of the air gap;

(3)令轴向磁轴承内导磁环沿径向的截面积与外导磁环沿径向的截面积相等，根据最大承载力F_max和饱和磁密B_s确定该截面积A；(3) Let the radial cross-sectional area of the inner magnetic conduction ring of the axial magnetic bearing be equal to the radial cross-sectional area of the outer magnetic conduction ring, and determine the cross-sectional area A according to the maximum bearing capacity F _max and the saturation flux density B _s ;

(4)计算内导磁环外径D_nw，也即永磁体外径D_pm1；(4) Calculate the outer diameter D _nw of the inner magnetic ring, that is, the outer diameter D _pm1 of the permanent magnet;

(5)根据气隙长度δ确定永磁体轴向长度h_pm、导磁轭厚度h以及槽口宽度L_c；(5) Determine the axial length h _pm of the permanent magnet, the thickness h of the magnetic yoke and the slot width L _c according to the air gap length δ;

(6)根据位移刚度K_x以及转子重力G确定电流刚度K_i，由电流密度J以及静态悬浮电流i确定线圈导线的直径d_c；(6) The current stiffness K _i is determined according to the displacement stiffness K _x and the rotor gravity G, and the diameter d _c of the coil wire is determined by the current density J and the static levitation current i;

(7)由位移刚度K_x计算永磁体内径D_pm2；(7) Calculate the inner diameter of the permanent magnet D _pm2 by the displacement stiffness K _x ;

(8)根据槽满率要求确定外导磁环内径D_wn，再由外导磁环沿径向的截面积A计算外导磁环外径D_ww；(8) Determine the inner diameter D _wn of the outer magnetic ring according to the slot fullness requirement, and then calculate the outer diameter D _ww of the outer magnetic ring from the cross-sectional area A of the outer magnetic ring along the radial direction;

(9)由电流刚度K_i确定线圈匝数N；(9) Determine the number of coil turns N by the current stiffness K _i ;

(10)由磁路各部分磁密相等原则，确定轴承体长度L。(10) Determine the length L of the bearing body based on the principle that the magnetic density of each part of the magnetic circuit is equal.

所述的气隙长度δ取为0.15～0.35mm；所述的第二气隙长度δ₁大于2倍气隙长度δ，取为0.4～1mm；所述的位移刚度取值范围由控制器决定，取为-0.5N/um～-2N/um；所述的漏磁系数σ取为1.1～3；所述的槽满率取为40％～60％。The air-gap length δ is 0.15-0.35mm; the second air-gap length _δ1 is greater than twice the air-gap length δ, and is 0.4-1mm; the value range of the displacement stiffness is determined by the controller , is taken as -0.5N/um～-2N/um; the magnetic leakage coefficient σ is taken as 1.1～3; the slot fullness rate is taken as 40%～60%.

本发明的原理是：本发明以轴向磁轴承的位移刚度入手进行设计，根据要求设定各个参数，通过轴向磁轴承的磁路分析与计算，即可得到磁轴承的其它结构尺寸。根据设定的转子转速n和材料强度可确定推力盘内径D_t2，考虑到气隙边缘效应可确定轴向磁轴承内导磁环内径D_nn为：The principle of the present invention is: the present invention starts with the displacement stiffness of the axial magnetic bearing for design, sets various parameters according to requirements, and through the magnetic circuit analysis and calculation of the axial magnetic bearing, other structural dimensions of the magnetic bearing can be obtained. The inner diameter D _t2 of the thrust disc can be determined according to the set rotor speed n and material strength, and the inner diameter D _nn of the inner magnetic ring of the axial magnetic bearing can be determined considering the edge effect of the air gap as:

D_nn＝D_t2+δ (1)D _nn =D _t2 +δ (1)

令轴向磁轴承内导磁环沿径向的截面积与外导磁环沿径向的截面积相等，根据最大承载力F_max和饱和磁密B_s由下式确定该截面积A：Let the radial cross-sectional area of the inner magnetic ring of the axial magnetic bearing be equal to the radial cross-sectional area of the outer magnetic ring, and determine the cross-sectional area A according to the maximum bearing capacity F _max and the saturation magnetic density B _s by the following formula:

$A A = = \frac{{F f}_{max max} \cdot &Center Dot; {μ μ}_{00}}{{B B}_{s the s}^{22}} - - - - - - - - ((22))$

式中μ₀＝4π×10^-7H/m，为空气的磁导率。In the formula, μ ₀ =4π×10 ^-7 H/m, which is the magnetic permeability of air.

根据设定的定转子之间的磁气隙长度δ，可以得到永磁体轴向长度h_pm、导磁轭厚度h以及槽口宽度L_c为：According to the set magnetic air gap length δ between the stator and rotor, the axial length h _pm of the permanent magnet, the thickness h of the magnetic yoke and the slot width L _c can be obtained as:

h_pm＝K₁·δ (3)h _pm =K ₁ ·δ (3)

h＝K₂·h_pm (4)h＝K ₂ ·h _pm (4)

L_c＝K₃·h_pm (5)L _c =K ₃ ·h _pm (5)

式中K₁、K₂、K₃为常数，根据经验取得。In the formula, K ₁ , K ₂ , and K ₃ are constants, obtained according to experience.

由(1)式以及内导磁环内径D_nn计算内导磁环外径D_nw(即永磁体外径D_pm1)为：Calculate the outer diameter D _nw of the inner magnetic ring (that is, the outer diameter of the permanent magnet D _pm1 ) from the formula (1 ₎ and the inner diameter D nn of the inner magnetic ring:

${D D.}_{nw nw} = = \sqrt{\frac{44 \cdot &Center Dot; A A}{π π} + + {D D.}_{nn n}^{22}} - - - - - - ((66))$

根据位移刚度K_x以及转子重力G可得电流刚度K_i：According to the displacement stiffness K _x and the rotor gravity G, the current stiffness K _i can be obtained:

${K K}_{i i} = = \frac{G G - - {K K}_{x x} \cdot &Center Dot; x x}{i i} - - - - - - ((77))$

式中x为静态悬浮时转子中心距离磁中心的偏移量。In the formula, x is the offset between the rotor center and the magnetic center during static levitation.

由电流密度J以及静态悬浮电流i确定线圈导线的直径d_c为：The diameter d _c of the coil wire is determined by the current density J and the static levitation current i as:

${d d}_{c c} = = \sqrt{\frac{44 \cdot &Center Dot; i i}{π π \cdot &Center Dot; J J}} - - - - - - - - ((88))$

然后根据国家标准取值。Then take the value according to the national standard.

由位移刚度K_x根据式(9)～(13)确定永磁体内径D_pm2：Determine the permanent magnet inner diameter D _pm2 from the displacement stiffness K _x according to formulas (9) to (13):

${C C}_{11} = = \frac{11}{\frac{11}{{R R}_{11}} + + \frac{11}{{R R}_{pm pm}}} - - - - - - ((99))$

${C C}_{22} = = \frac{11}{{μ μ}_{00} \cdot &Center Dot; {A A}_{w w}} + + \frac{11}{{μ μ}_{00} \cdot &Center Dot; {A A}_{n no}} - - - - - - ((1010))$

C₃＝(R_pm+R₁)·δ·C₂+R_pm·R₁ (11)C ₃ =(R _pm +R ₁ )·δ·C ₂ +R _pm ·R ₁ (11)

${K K}_{x x} = = - - \frac{22 \cdot &Center Dot; {F f}_{pm pm}^{22} \cdot &Center Dot; {R R}_{11}^{22} \cdot &Center Dot; (({R R}_{pm pm} + + {R R}_{11})) \cdot \cdot {C C}_{22}}{{μ μ}_{00} \cdot &Center Dot; {σ σ}^{22} \cdot &Center Dot; {C C}_{33}^{33}} ((\frac{11}{{A A}_{n no}} + + \frac{11}{{A A}_{w w}})) - - - - - - ((1212))$

式中A_n为内导磁环面积，A_w为外导磁环面积，且A_n＝A_w＝A，其中F_pm＝H_pm·h_pm为永磁体的磁动势，H_pm为永磁体的矫顽力，一般取为760kA/m～790kA/m；μ_pm为永磁体的相对磁导率，一般取为1.03～1.05，R₁为第二气隙的磁阻，为：In the formula, A _n is the area of the inner magnetic ring, A _w is the area of the outer magnetic ring, and _An = A _w = A, where F _pm = H _pm · h _pm is the magnetomotive force of the permanent magnet, and H _pm is the permanent magnet The coercive force of the magnet is generally taken as 760kA/m～790kA/m; μ _pm is the relative permeability of the permanent magnet, generally taken as 1.03～1.05, and _R1 is the reluctance of the second air gap, which is:

${R R}_{11} = = \frac{{δ δ}_{11}}{{μ μ}_{00} \cdot &Center Dot; π π \cdot &Center Dot; \frac{{D D.}_{}^{pm pm 22} - - {D D.}_{}^{nn n}}{44}} - - - - - - - - ((1313))$

根据槽满率要求确定外导磁环内径D_wn，再由外导磁环沿径向的截面积A计算外导磁环外径D_ww为：Determine the inner diameter D _wn of the outer magnetic ring according to the slot full rate requirements, and then calculate the outer diameter D _ww of the outer magnetic ring from the radial cross-sectional area A of the outer magnetic ring as:

${D D.}_{ww ww} = = \sqrt{\frac{44 \cdot &Center Dot; A A}{π π} + + {D D.}_{wn wn}^{22}} - - - - - - ((1414))$

考虑到气隙边缘效应，可得到推力盘外径D_t1为：Considering the edge effect of the air gap, the outer diameter D _t1 of the thrust disc can be obtained as:

D_t1＝D_ww+δ (15)D _t1 =D _ww +δ (15)

由电流刚度K_i计算线圈匝数N为：Calculate the number of coil turns N from the current stiffness K _i as:

$N N = = \frac{{K K}_{11} \cdot &Center Dot; {μ μ}_{00} \cdot &Center Dot; σ σ \cdot &Center Dot; {C C}_{33} \cdot &Center Dot; ((δ δ \cdot &Center Dot; {C C}_{22} + + {C C}_{11}))}{22 \cdot &Center Dot; {F f}_{pm pm} \cdot &Center Dot; {R R}_{11} \cdot \cdot ((\frac{11}{{A A}_{n no}} + + \frac{11}{{A A}_{w w}}))} - - - - - - ((1616))$

根据轴承体各个部分磁密基本相等的原则确定轴承体长度L为：According to the principle that the magnetic density of each part of the bearing body is basically equal, the length L of the bearing body is determined as:

$L L = = \frac{22 \cdot &Center Dot; A A}{π π \cdot &Center Dot; (({D D.}_{wn wn} + + {D D.}_{nw nw}))} + + {L L}_{c c} - - - - - - ((1717))$

推力盘轴向长度L_t同样可根据轴承体各部分磁密基本相等的原则确定：The axial length L _t of the thrust plate can also be determined according to the principle that the magnetic density of each part of the bearing body is basically equal:

${L L}_{t t} = = \frac{A A}{π π \cdot &Center Dot; \frac{{D D.}_{t t 11} + + {D D.}_{t t 22}}{22}} - - - - - - ((1818))$

至此，整个永磁偏置轴向磁轴承设计完毕。So far, the design of the entire permanent magnet bias axial magnetic bearing is completed.

本发明与现有技术相比的优点在于：本发明由于采用以轴向磁轴承位移刚度为出发点的设计方法，与现有轴向磁轴承以永磁体最佳工作点为出发点的设计方法相比，更加利于控制，得到的结构参数更加合理。Compared with the prior art, the present invention has the advantages that: the present invention uses the design method based on the axial magnetic bearing displacement stiffness as the starting point, compared with the existing axial magnetic bearing design method based on the permanent magnet optimal working point , which is more conducive to control, and the obtained structural parameters are more reasonable.

附图说明 Description of drawings

图1为本发明针对的永磁偏置轴向磁轴承结构图；Fig. 1 is the structural diagram of the permanent magnet bias axial magnetic bearing aimed at by the present invention;

图2为本发明的设计流程图；Fig. 2 is the design flowchart of the present invention;

图3为按照本发明设计的永磁偏置轴向磁轴承定子组件实物图；Fig. 3 is the actual figure of the permanent magnet bias axial magnetic bearing stator assembly designed according to the present invention;

具体实施方式 Detailed ways

如图1所示，本发明的设计对象为一种磁悬浮飞轮用永磁偏置轴向磁轴承，图中1为导磁轭，2为第二气隙，3为永磁体，4为线圈，5为轴承体，6为轴承体(也称为定子)与推力盘之间的磁气隙，7为推力盘。根据现有磁轴承控制器的要求设定该轴向磁轴承的位移刚度K_x为-0.7N/um，根据现有加工水平设定气隙长度δ取为0.25mm，为了使磁轴承电励磁磁路经过第二气隙构成回路而不经过永磁体，同时避免永磁体在第二气隙损失过多的磁动势，因而第二气隙的长度应稍大于2倍气隙长度，在此取第二气隙δ₁为0.6mm，根据该磁轴承的磁场分析设定漏磁系数σ为1.3，根据磁悬浮飞轮的指标要求设定最大承载力F_max为1230N，转子转速n为5000r/min，根据磁悬浮飞轮的功耗要求设定静态悬浮电流i为0.2A，该实施例中轴向磁轴承的轴承体以及导磁轭选用电工纯铁DT4，根据DT4的磁化曲线设定各导磁部分材料的饱和磁密B_s为1.2T，根据现有线圈的下线水平设定槽满率为40％。由转子转速n以及材料强度设定推力盘内径D_t2＝63mm。As shown in Figure 1, the design object of the present invention is a permanent magnetic bias axial magnetic bearing for a magnetic levitation flywheel. Among the figures, 1 is a magnetic yoke, 2 is a second air gap, 3 is a permanent magnet, and 4 is a coil. 5 is the bearing body, 6 is the magnetic air gap between the bearing body (also known as the stator) and the thrust disc, and 7 is the thrust disc. According to the requirements of the existing magnetic bearing controller, the displacement stiffness K _x of the axial magnetic bearing is set to be -0.7N/um, and the air gap length δ is set to be 0.25mm according to the existing processing level. In order to make the magnetic bearing electrically excited The magnetic circuit passes through the second air gap to form a circuit without passing through the permanent magnet, and at the same time prevents the permanent magnet from losing too much magnetomotive force in the second air gap, so the length of the second air gap should be slightly greater than twice the length of the air gap, here Take the second air gap δ ₁ as 0.6mm, set the magnetic leakage coefficient σ as 1.3 according to the magnetic field analysis of the magnetic bearing, set the maximum bearing capacity F _max as 1230N according to the index requirements of the magnetic levitation flywheel, and set the rotor speed n as 5000r/min According to the power consumption requirements of the magnetic levitation flywheel, the static levitation current i is set to be 0.2A. In this embodiment, the bearing body and the magnetic yoke of the axial magnetic bearing are selected from electrician pure iron DT4, and the magnetic conduction parts are set according to the magnetization curve of DT4 The saturation magnetic density B _s of the material is 1.2T, and the slot fill rate is set to 40% according to the off-line level of the existing coil. The inner diameter of the thrust disc D _t2 =63mm is set according to the rotor speed n and the material strength.

根据以上条件，由式(1)可得内导磁环内径D_nn＝63.25mm。由式(2)可以得出轴向磁轴承定子内、外导磁环沿径向的截面积A＝1100mm²，设K₁＝10，K₂＝1，K₃＝4，由(3)～(5)式可得到永磁体轴向长度h_pm＝2.5mm，导磁轭厚度h＝2.5mm，槽口宽度L_c＝10mm，由式(6)计算出内导磁环外径D_nw＝73.9mm，由式(7)和(8)可得电流刚度K_i＝374.3N/A，线圈导线的直径d_c＝0.35mm，由(9)～(13)式可以看出，很难得到由位移刚度K_x直接表示出的永磁体内径D_pm2的表达式，为了计算出永磁体内径D_pm2，本实施例中采用从大到小设定永磁体内径D_pm2的值，代入位移刚度K_x表达式(12)，求出位移刚度K_x，当计算得到的K_x与给定值相差小于1％时，认为此时永磁体内径的值D_pm2即为设计值。通过该方法可以计算出永磁体内径D_pm2＝66.8mm，根据槽满率要求确定外导磁环内径D_wn＝95.9mm，由外导磁环沿径向的截面积A根据式(14)计算外导磁环外径D_ww＝102.8mm，考虑气隙边缘效应，由式(15)可得推力盘外径D_t1＝103.05mm，由式(16)可以计算出线圈匝数N＝355，根据轴承体各部分磁密基本相等原则由式(17)计算轴承体长度L＝14mm，由式(18)可得推力盘轴向长度为：L_t＝4.2mm，至此，该永磁偏置轴向磁轴承设计完毕。According to the above conditions, the inner diameter of the inner magnetic permeable ring D _nn =63.25mm can be obtained from formula (1). From formula (2), it can be obtained that the cross-sectional area of the inner and outer magnetic rings of the axial magnetic bearing stator along the radial direction is A=1100mm ² , assuming K ₁ =10, K ₂ =1, K ₃ =4, from (3) ~ Formula (5) can obtain the axial length of the permanent magnet h _pm = 2.5mm, the thickness of the magnetic yoke h = 2.5mm, the slot width L _c = 10mm, and calculate the outer diameter of the inner magnetic ring D _nw from the formula (6) = 73.9mm, from equations (7) and (8), the current stiffness K _i = 374.3N/A, the diameter of the coil wire _dc = 0.35mm, it can be seen from equations (9) ~ (13), it is difficult Obtain the expression of the permanent magnet inner diameter D _pm2 directly represented by the displacement stiffness K _x , in order to calculate the permanent magnet inner diameter D _pm2 , in this embodiment, the value of the permanent magnet inner diameter D _pm2 is set from large to small, and the displacement stiffness is substituted K _x expression (12), calculate the displacement stiffness K _x , when the difference between the calculated K _x and the given value is less than 1%, it is considered that the value D _pm2 of the inner diameter of the permanent magnet at this time is the design value. Through this method, the inner diameter of the permanent magnet D _pm2 = 66.8mm can be calculated, and the inner diameter of the outer magnetic ring D _wn = 95.9mm is determined according to the slot fullness ratio, and the cross-sectional area A of the outer magnetic ring along the radial direction is calculated according to formula (14) The outer diameter of the outer magnetic ring D _ww = 102.8mm, considering the edge effect of the air gap, the outer diameter of the thrust disc D _t1 = 103.05mm can be obtained from the formula (15), and the number of coil turns N = 355 can be calculated from the formula (16). According to the principle that the magnetic density of each part of the bearing body is basically equal, the length of the bearing body is calculated by formula (17) L = 14mm, and the axial length of the thrust plate can be obtained from formula (18): L _t = 4.2mm, so far, the permanent magnetic bias The design of the axial magnetic bearing is completed.

本发明说明书中未作详细描述的内容属于本领域专业技术人员公知的现有技术。The contents not described in detail in the description of the present invention belong to the prior art known to those skilled in the art.

Claims

1. the design method of a permanent-magnetic biased axial magnetic bearing is characterized in that: this method is based on the displacement rigidity K that at first determines magnetic bearing _x, its concrete steps are as follows:

(1) at first sets the displacement rigidity K of magnetic bearing _x, rotor speed n, gap length δ, interstice length δ ₁, leakage coefficient σ, maximum load capacity F _Max, static suspension current i and saturation magnetic induction B unshakable in one's determination _s

(2) determine the thrust disc inside diameter D according to the rotor speed n and the strength of materials _T2, consider that the air gap edge edge effect determines magnetic guiding loop inside diameter D in the axial magnetic bearing _Nn

(3) make the interior magnetic guiding loop sectional area radially of axial magnetic bearing equate, according to maximum load capacity F with outer magnetic guiding loop sectional area radially _MaxWith saturation magnetic induction B _sDetermine this sectional area A;

(4) calculate interior magnetic guiding loop outer diameter D _Nw, also be the permanent magnet outer diameter D _Pm1

(5) determine permanent magnet axial length h according to gap length δ _Pm, conductive magnetic yoke thickness h and width of rebate L _c

(6) according to displacement rigidity K _xAnd rotor gravity G determines current stiffness K _i, determine the diameter d of winding wire by current density, J and static suspension current i _c

(7) by displacement rigidity K _xCalculate the permanent magnet inside diameter D _Pm2

(8) require to determine outer magnetic guiding loop inside diameter D according to copper factor _Wn, calculate outer magnetic guiding loop outer diameter D by outer magnetic guiding loop sectional area A radially again _Ww, consider that the thrust disc outer diameter D is determined in the edge effect of air gap _T1

(9) by current stiffness K _iDetermine turn number N;

(10 by the close equal principle of magnetic circuit each several part magnetic, determines bearing support length L and thrust disc axial length L _t

2. the design method of a kind of permanent-magnetic biased axial magnetic bearing according to claim 1, it is characterized in that: described gap length δ is taken as 0.15～0.35mm.

3. the design method of a kind of permanent-magnetic biased axial magnetic bearing according to claim 1 is characterized in that: described interstice length δ ₁Greater than 2 times of gap length δ, be taken as 0.4～1mm.

4. the design method of a kind of permanent-magnetic biased axial magnetic bearing according to claim 1 is characterized in that: described displacement rigidity span determines by controller, be taken as-0.5N/um～-2N/um.

5. the design method of a kind of permanent-magnetic biased axial magnetic bearing according to claim 1, it is characterized in that: described leakage coefficient σ is taken as 1.1～3.

6. the design method of a kind of permanent-magnetic biased axial magnetic bearing according to claim 1, it is characterized in that: described copper factor is taken as 40%～60%.