Patent Publication Number: US-2023155449-A1

Title: Force-balancing magnetic bearing with adjustable bias magnetic field for stator permanent magnet motor

Description:
CROSS REFERENCE TO THE RELATED APPLICATIONS 
     This application is the national stage entry of International Application No. PCT/CN2021/133962, filed on Nov. 29, 2021, which is based upon and claims priority to Chinese Patent Application No. 202110435872.0 filed on Apr. 22, 2021, the entire contents of which are incorporated herein by reference. 
    
    
     TECHNICAL FIELD 
     Disclosed in the present disclosure is a force-balancing magnetic bearing with an adjustable bias magnetic field for a stator permanent magnet motor, which relates to the related technology in the field of electrical and mechanical transmission apparatuses, and belongs to the technical field of power generation, power transformation or power distribution. 
     BACKGROUND 
     The conventional stator permanent magnet motors include a doubly salient permanent magnet motor, a magnetic flux reverse permanent magnet motor and a magnetic flux switching permanent magnet motor, in which the permanent magnets are all located on the stators and no permanent magnet or winding is mounted on the rotators, so there is no risk that the permanent magnet of the conventional rotor permanent magnet motor is broken by centrifugal force and demagnetized at high temperature. However, the existing stator permanent magnet motor usually has a mechanical bearing, and the mechanical bearing is prone to high noise, high cost, fatigue failure and so on, which are often observed in the stator permanent magnet motor. Disclosed in a Chinese patent with the publication number of CN111425523A is a hybrid radial permanent magnet bias magnetic bearing, which uses a stator core of a traditional eight-pole motor as a main body structure of the magnetic bearing, with eight electromagnetic control magnetic poles and two permanent magnet bias magnetic poles, the static bearing capacity of the bearing is improved, the loss and the size are reduced, but the using effect of the bearing is likely to be influenced by the mounting angle and the mounting position, specifically, and the bearing can only be vertically mounted in the horizontal motor. Moreover, the permanent magnet bias magnetic circuit and the electromagnet magnetic circuit have a high coupling degree, and according to the principle of minimum reluctance, during practical application, the permanent magnetic field and the adjacent electromagnetic control magnetic poles are extremely likely to form a loop through the bias magnetic poles, causing the risk that the electromagnetic control magnetic poles cannot generate enough control force. 
     The axial force, a technical problem frequently faced by centrifugal fans, centrifugal impellers, etc., is closely related to apparatus manufacturing quality, liquid viscosity, rotation direction and mounting mode, the overlarge axial force can cause axial movement of the rotating shaft of the apparatus to cause bearing abrasion, motor rotor eccentricity and other problems, increasing maintenance difficulty and maintenance cost of the apparatus and reducing the service life and the production efficiency. The permanent magnet bias type radial magnetic bearing uses a permanent magnet material to generate a bias magnetic field, further generates the bias force to reduce the bias current of the conventional active type electrically-driven magnetic bearing, and is widely applied to vacuum apparatus manufacturing, compressors and other high-speed and vacuum fields because of the remarkable advantages of no contact, no lubrication and no abrasion. 
     With the emergence of permanent magnet bias type magnetic bearing products, the application research of the magnetic bearing has been firstly developed in the industries of vacuum apparatus manufacturing, compressors, etc., and a satisfactory effect has been achieved. Meanwhile, with the firm rotor structure and desirable operation performance, the stator permanent magnet motor is widely applied in the industry. Disclosed in a Chinese patent with the publication number of CN111927885A is a permanent magnet bias axial magnetic bearing. The magnetic bearing includes a first magnetic bearing stator assembly and a second magnetic bearing stator assembly symmetrically arranged on the two sides of the rotor, in this patent, separation of the electromagnetic flux and the permanent magnetic flux is achieved, power consumption of the magnetic bearing is reduced, and the dynamic response speed and the control precision of the magnetic bearing are improved. Chinese invention patents with application numbers of 201410594571.2 and 201410462477.1 provide abundant stator permanent magnet motor topological structures, widening the application field of the type of motor to a greater extent, and also providing abundant motor products for the industry. 
     Disclosed in a Chinese patent with the application number of 201910198690.9 are an axial force balancing and sealing structure and a high-power-density centrifugal fan, an axial force balancing disc and a sealing structure are integrally designed, which reduces the mass added to the output shaft, a three-layer sealing structure is designed, the axial force generated by the pressure difference counteracts part of the axial force generated by the impeller, but from the aspect of implementation, the structure still uses a passive axial force balance measure, and the system structure is complex. In the existing technology, balancing components such as a balancing disc, a wear-resisting plate and a balancing ring are commonly used in industry, a medium pumped by the apparatus generates a pressure difference on the two sides of the balancing component, part of axial force is balanced by using the pressure difference to weaken the adverse consequences caused by the axial force, however, the use of the balance component increases the complexity and axial length of the whole system, and the apparatus also faces the problems of increase of maintenance cost, reduction of system performance, etc. caused by abrasion of the balancing component. 
     In addition, the existing axial force balancing device, a permanent magnet bias type magnetic bearing and a stator permanent magnet motor are designed and machined as independent components and are assembled according to the required performance and design solution, so the compactness of the components is not high, and the size after assembly is larger. After mounted on the apparatus, the existing axial force balancing device usually cannot be adjusted according to the operation condition and the load change of the apparatus, and the balance potential of the axial force balancing device cannot be used to the maximum extent. 
     In conclusion, it is of important theoretical significance and application value to design a force-balancing magnetic bearing with an adjustable bias magnetic field for a stator permanent magnet motor for widening the use field of the stator permanent magnet motor and inspiring those skilled in the art to research into a structure compact type magnetic bearing motor system and a bias magnetic field adjustable type magnetic bearing. 
     SUMMARY 
     The objective of the present disclosure is to provide a force-balancing magnetic bearing with an adjustable bias magnetic field for a stator permanent magnet motor for overcoming the defects of the background technology, so as to improve compactness between a stator permanent magnet motor and a magnetic bearing, and to solve the technical problems that the pole number and strength of a permanent magnet bias magnetic field may not be adjusted and the structure is not compact after a conventional permanent magnet bias type magnetic bearing is mounted. 
     In order to achieve the above objective, the present invention uses the following technical solution: 
     A force-balancing magnetic bearing with an adjustable bias magnetic field for a stator permanent magnet motor is provided, a radial magnetic bearing consists of four permanent magnetic poles with adjustable bias magnetic fields and four electromagnetic poles, the eight magnetic poles are evenly distributed at an interval of 45° and are concentric with the motor, lower ends of the eight magnetic poles are arc surfaces, air gaps are reserved between the magnetic poles and a magnetic bearing rotor, the four electromagnetic poles are provided with electromagnetic pole winding coils, and the electromagnetic poles and the bias magnetic poles act together to keep the magnetic bearing rotor to suspend stably. 
     Preferably, the radial magnetic bearing is located on an inner side of an end of a stator winding coil and keeps a certain distance from a motor rotor in an axial direction, such that the bearing has the feature of being compact in structure. 
     Preferably, the radial magnetic bearing consists of permanent magnet sections axially longer than a stator core, left permanent-magnet magnetic bridges, right permanent-magnet magnetic bridges, magnetic adjusting sections, an electromagnetic pole stator, an electromagnetic pole and permanent magnetic pole isolation plate, permanent-magnet two-side magnetic pole connection sections, left permanent-magnet magnetic poles, right permanent-magnet magnetic poles, electromagnetic poles, electromagnetic pole winding coils, a first radial sensor, a second radial sensor and a magnetic bearing rotor. 
     Preferably, two sides of each permanent magnet section axially longer than a length of the stator core are provided with a set of magnetic bridges, lower portions of the set of magnetic bridges are connected to a left permanent-magnet magnetic pole and a right permanent-magnet magnetic pole respectively, each of the left permanent-magnet magnetic pole and the right permanent-magnet magnetic pole is of a two-segment structure, upper magnetic conduction sections are connected to the left permanent-magnet magnetic bridge and the right permanent-magnet magnetic bridge, and the above components are made of magnetic conduction materials and may lead out magnetic field energy of the permanent magnet sections axially longer than the length of the stator core. 
     Preferably, a magnetic adjusting section is arranged in the midd 1 e of each magnetic conduction section, is made of magnetic conduction materials, and adjusts a magnetic conductivity of the magnetic adjusting section or an embedded size of the magnetic conduction section to adjust a bias magnetic field, so as to adjust bias force. 
     Preferably, the permanent-magnet two-side magnetic pole connection section and the electromagnetic pole and permanent magnetic pole isolation plate integrally manufactured are arranged and are made of materials which are non-magnetic-conductive, low in conductivity and certain in strength and hardness, one side close to the magnetic conduction sections is provided with electromagnetic pole and permanent magnetic pole isolation plate recesses and electromagnetic pole and permanent magnetic pole isolation plate bosses, the recesses and the magnetic conduction sections have equal widths and depths, the bosses and the magnetic conduction sections have equal intervals, the magnetic conduction sections are embedded into the recesses, and the bosses are embedded between the magnetic conduction sections. One side away from the magnetic conduction sections is provided with electromagnetic pole and permanent magnetic pole isolation plate recesses, and electromagnetic pole stator bosses may be embedded therein. Meanwhile, the permanent-magnet two-side magnetic pole connection sections are embedded between the left permanent-magnet magnetic poles and the right permanent-magnet magnetic poles to form stable sandwich structures. 
     Preferably, the first radial sensor and the second radial sensor are arranged in centers of lower portions of the permanent-magnet two-side magnetic pole connection sections, are distributed at an interval of 90° and are configured to measure a radial position of the magnetic bearing rotor. 
     Preferably, electromagnetic pole stator bosses are arranged on one axial side of the electromagnetic pole stator and may be embedded into the electromagnetic pole and permanent magnetic pole isolation plate recesses, and the electromagnetic poles are provided with the electromagnetic pole winding coils. 
     An axial force and bias force-balancing axial magnetic bearing for a stator permanent magnet motor is provided, the axial magnetic bearing is of an eight-pole structure, electromagnetic force is provided by four internally grooved electromagnetic poles, and permanent magnet bias force is provided by four internally grooved permanent magnetic poles. The eight magnetic poles are evenly distributed at an interval of 45°, lower ends of the eight magnetic poles are arc surfaces, and the magnetic poles are preferably made of silicon steel sheets and other materials with desirable magnetic conductivity and low conductivity. 
     Preferably, a length d 1  of a rear air gap between the permanent magnetic pole and a thrust disc reinforcing member is equal to a length d 2  of a front air gap between the permanent magnetic pole and the thrust disc reinforcing member, and a length w 1  of a rear air gap between the permanent magnetic pole and a thrust disc and a length w 2  of a front air gap between the permanent magnetic pole and the thrust disc are adjustable and used for bias force adjustment. 
     Preferably, a length d 3  of a rear air gap between the electromagnetic pole and the thrust disc reinforcing member is equal to a length d 4  of a front air gap between the electromagnetic pole and the thrust disc reinforcing member, a length w 3  of a rear air gap between the electromagnetic pole and the thrust disc is equal to d 1 , and a length w 4  of a front air gap between the electromagnetic pole and the thrust disc is equal to d 2 . Further, d 1  is much larger than w 1 , or d 1  is much larger than w 2 , and a length h 1  of a rear air gap between the permanent magnetic pole and the thrust disc is equal to d 1 . 
     Two thrust disc reinforcing members are arranged on two sides of the thrust disc for fastening the thrust disc, the thrust disc has an outer diameter larger than that of the thrust disc reinforcing members and an inner diameter equal to an outer diameter of a motor rotating shaft, is made of silicon steel sheets and other materials with desirable magnetic conductivity and low conductivity and may serve as an independent component or an integral component. When the thrust disc has an outer diameter smaller than the outer diameter of the motor rotating shaft and a larger axial length, the thrust disc reinforcing member may be omitted. 
     Preferably, two paths of permanent magnetic pole magnetic fluxes may be changed by means of the magnetic adjusting members, the two branch magnetic fluxes of the permanent magnetic pole magnetic fluxes may be adjusted by means of the air gap lengths w 1  and w 2 , and the bias force of the axial magnetic bearing may be determined by the branch magnetic fluxes. 
     Preferably, the electromagnetic pole and permanent magnetic pole isolation plate are used to isolate the permanent magnetic pole magnetic flux and the electromagnetic pole magnetic flux, so as to reduce the coupling degree of the two magnetic fluxes. 
     Preferably, a magnetic conductivity of a magnetic adjusting member and an embedded size of the magnetic conduction sections are adjusted, relative distances between the thrust disc and a front permanent magnetic pole and a rear permanent magnetic pole are changed, then a cluster of bias force characteristic curves is obtained, and axial force of an apparatus during operation is computed according to a working mode, a load feature, a rotation direction and a mounting mode of the apparatus with the axial force, an optimal magnetic conductivity of the magnetic adjusting member, an optimal embedded size of the magnetic conduction sections and an optimal relative distance between the thrust disc and the front (or rear) permanent magnetic pole are set, the permanent magnetic poles are used to generate bias force equal to and opposite to the axial force of the apparatus, and when the bias force of the permanent magnetic poles is not enough to balance the axial force and the apparatus is disturbed by a load during dynamic operation to make the thrust disc deviate from a balance position, a current is introduced into the electromagnetic pole coils to generate electromagnetic force, and the electromagnetic force and the bias force of the permanent magnetic poles act together to balance the axial force. The present disclosure has the advantages of compact structure, high use degree of the permanent magnet bias magnetic field, low coupling degree of the permanent magnet flux and the electromagnetic flux, and convenience in control, and reduces the control current. 
     Compared with the prior art, the present disclosure has the significant advantages: 
     (1) A radial magnetic bearing with a compact structure and an adjustable bias magnetic field for a stator permanent magnet motor is designed, the radial magnetic bearing includes four permanent magnetic poles including permanent magnet sections axially longer than a stator core, left permanent-magnet magnetic bridges, right permanent-magnet magnetic bridges, magnetic adjusting sections, an electromagnetic pole stator, an electromagnetic pole and permanent magnetic pole isolation plate, permanent-magnet two-side magnetic pole connection sections, left permanent-magnet magnetic poles, right permanent-magnet magnetic poles, electromagnetic poles, electromagnetic pole winding coils, a first radial sensor, a second radial sensor and a magnetic bearing rotor, and four electromagnetic pole, where a magnetic flux of the permanent magnetic poles is adjusted by the magnetic adjusting sections, and the electromagnetic poles are adjusted by a current introduced into the electromagnetic pole winding coils; the recess and boss structures are reasonably arranged, and all components are reliably connected and have compact structures; and a common path of a permanent magnet bias magnetic flux and a electromagnetic pole magnetic flux is only the magnetic bearing rotor, and the permanent magnetic poles and the electromagnetic poles are isolated from each other by the permanent-magnet two-side magnetic pole connection sections and the electromagnetic pole and permanent magnetic pole isolation plate, that is, a coupling degree of the permanent magnet bias magnetic flux and the electromagnetic pole magnetic flux is low, such that the magnetic bearing can be controlled, and a compact structure and an adjustable bias magnetic field are achieved. 
     (2) A stator magnetic field of a stator permanent magnet motor is introduced into a magnetic suspension bearing, such that the feature of compact structure is achieved, an axial magnetic bearing formed by permanent magnetic poles and stator magnetic poles is designed, a magnetic conductivity of a magnetic adjusting member and an embedded size of the magnetic conduction sections are adjusted, relative distances (lengths of air gaps) between the thrust disc and the front permanent magnetic pole and the rear permanent magnetic pole are changed, then a cluster of bias force characteristic curves which may be looked up is obtained, an optimal magnetic conductivity of the magnetic adjusting member, an optimal embedded size of the magnetic conduction sections and an optimal relative distance between the thrust disc and the front (or rear) magnetic pole are set according to different working modes, load features, rotation directions and mounting modes of an apparatus with axial force, bias force of the permanent magnetic poles and electromagnetic force of the electromagnetic magnetic poles balance the axial force together, the feature of high use degree of a permanent magnet bias magnetic field is achieved, moreover, the permanent magnetic pole magnetic flux and the electromagnetic pole magnetic flux flow through different paths, and decoupling isolation of the permanent magnetic pole magnetic flux and the electromagnetic pole magnetic flux is achieved by means of the electromagnetic pole and permanent magnetic pole isolation plate, such that the present disclosure has the advantage of being convenient to control. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG.  1 A  is a structural diagram of a force-balancing radial magnetic bearing with an adjustable bias magnetic field for a stator permanent magnet motor mounted on the stator permanent magnet motor in Embodiment 1 of the present disclosure,  FIG.  1 B  is a front view of  FIG.  1 A , and  FIG.  1 C  is an axial half and circumferential one-third sectional view of  FIG.  1 A . 
         FIG.  2 A  is a structural diagram of the radial magnetic bearing in Embodiment 1 of the present disclosure,  FIG.  2 B  is a front view of  FIG.  2 A ,  FIG.  2 C  is a side view of  FIG.  2 A , and  FIG.  2 D  is an exploded view of various components of  FIG.  2 A . 
         FIG.  3 A  is a schematic diagram of a permanent magnet bias magnetic flux and an electromagnetic pole magnetic flux in Embodiment 1 of the present disclosure, and  FIG.  3 B  is a front view of  FIG.  3 A . 
         FIG.  4 A  is a structural diagram of a force-balancing axial magnetic bearing with an adjustable bias magnetic field for a stator permanent magnet motor mounted on the stator permanent magnet motor in Embodiment 2 of the present disclosure, and  FIG.  4 B  is a front view of  FIG.  4 A . 
         FIG.  5    is an exploded view of various components of the axial magnetic bearing in Embodiment 2 of the present disclosure. 
         FIG.  6    is a partial sectional view and an enlarged partial view of the axial magnetic bearing in Embodiment 2 of the present disclosure. 
         FIG.  7 A  is a schematic diagram of a permanent magnet bias pole of the axial magnetic bearing in Embodiment 2 of the present disclosure, and  FIGS.  7 B and  7 C  are a front view and a side view of a permanent magnet bias magnetic pole magnetic flux respectively. 
         FIG.  8 A  is a schematic diagram of an electromagnetic pole of the axial magnetic bearing in Embodiment 2 of the present disclosure, and  FIGS.  8 B and  8 C  are a front view and a sectional view of an electromagnetic pole magnetic flux respectively. 
         FIG.  9    is a relation diagram of bias force and distance d obtained in Embodiment 2 of the present disclosure. 
     
    
    
     DESCRIPTION OF THE REFERENCE NUMERALS 
       1 . stator winding coil end,  2 . stator core,  3 . permanent magnet axially longer than stator core,  301 ,  302 ,  303  and  304 . permanent magnet section axially longer than stator core,  4 . permanent magnet axially equal to stator core,  5 . motor rotor,  6 . left permanent-magnet magnetic bridge,  7 . right permanent-magnet magnetic bridge,  8 . magnetic adjusting section,  9 . radial electromagnetic pole stator,  9   a . electromagnetic pole stator boss,  10 . electromagnetic pole and permanent magnetic pole isolation plate,  10   a ,  10   c  and  10   d . electromagnetic pole and permanent magnetic pole isolation plate recess,  10   b . electromagnetic pole and permanent magnetic pole isolation plate boss,  11 . permanent-magnet two-side magnetic pole connection section,  12 . left permanent-magnet magnetic pole,  13 . right permanent-magnet magnetic pole,  12   a  and  13   a . magnetic conduction section,  14 . radial electromagnetic pole,  1401  and  1402 . radial electromagnetic pole,  15 . radial electromagnetic pole winding coil,  1501  and  1502 . radial electromagnetic pole winding coil,  16 . first radial sensor,  17 . second radial sensor,  18 . radial magnetic bearing rotor,  19 . motor rotating shaft,  20 . axial electromagnetic pole stator,  21 . axial electromagnetic pole and permanent magnetic pole isolation plate,  22   a . rear axial permanent-magnet two-side magnetic pole connector,  22   b . front axial permanent-magnet two-side magnetic pole connector,  23 . left permanent-magnet grooved magnetic pole,  24 . right permanent-magnet grooved magnetic pole,  23   a  and  24   a . magnetic conduction section,  25 . first axial sensor,  26 . second axial sensor,  27 . axial electromagnetic pole winding coil,  28 . axial electromagnetic pole,  28   a  and  28   b . rear axial electromagnetic pole and front axial electromagnetic pole,  29 . thrust disc reinforcing member,  30 . thrust disc,  23   b  and  24   b . rear axial permanent magnetic pole, and  23   c  and  24   c . front axial permanent magnetic pole. 
     DETAILED DESCRIPTION OF THE EMBODIMENTS 
     In order to facilitate a detailed explanation of the present disclosure, an x-y-z reference coordinate system is established without loss of generality, an origin is o, a plane x-y is parallel to an end face of a cylindrical electric motor (that is, a cylinder bottom surface), a radius direction in the plane x-y is a radial direction, each end face circle is a circumferential direction, and z is an axial direction; meanwhile, one side of a component in the radial direction outward is defined as an “outer side”, one side of the component in the radial direction inward is defined as an “inner side”, one side of the component in the axial positive direction is defined as a “front side”, and one side of the component in the axial negative direction is defined as a “rear side”; and the “left” and “right” of a reader define the “left” and “right” of the component when the reader faces the plane x-y. 
     The technical solution of the present disclosure will now be described in detail with reference to the accompanying drawings. 
     Embodiment 1: Force-balancing radial magnetic bearing with adjustable bias magnetic field for stator permanent magnet motor 
     As shown in  FIGS.  1 A and  1 B , a force-balancing radial magnetic bearing with an adjustable bias magnetic field for a stator permanent magnet motor in Embodiment 1 of the present disclosure is mounted on a stator permanent magnet motor. A stator winding coil end  1 , stator cores  2 , a permanent magnet  3  axially longer than the stator cores, permanent magnets  4  axially equal to the stator cores, a motor rotor  5  and a motor rotating shaft  19  are components of the stator permanent magnet motor, and except for the permanent magnet  3  axially longer than the stator core, other components have dimensions, materials, and structures known to those skilled in the art. The stator cores  2  are evenly arranged in a circumferential direction of the motor, the permanent magnet  3  axially longer than the stator cores or the permanent magnet  4  axially equal to the stator cores is embedded between two adjacent stator cores  2 , a coil is wound around each stator core  2 , the coil wound around each stator core penetrates a motor groove to form the stator winding coil end  1 , the motor rotor  5  is assembled on the motor rotating shaft  19  in an interference mode or a key groove mode, and an annular stator structure composed of the stator cores and the permanent magnets is assembled on an outer side of the motor rotor  5 . 
     As shown in  FIGS.  1 A,  1 B and  1 C , the stator permanent magnet motor is totally provided with twelve stator permanent magnets which are evenly distributed at an interval of  30 °, the stator permanent magnets may be made of one or more of ferrite, neodymium iron boron, samarium cobalt and other existing magnetic materials, a magnetizing direction (also called magnetization direction and polarization direction) is tangential, the magnetizing directions of two adjacent stator permanent magnets are opposite; the stator permanent magnets include four permanent magnets  3  axially longer than the stator cores and eight permanent magnets  4  axially equal to the stator cores, axial lengths of the permanent magnets  3  axially longer than the stator cores are larger than that of the stator cores  2 , a single-side extension length is about 5% of the length of the stator cores, and the four permanent magnets are arranged on an upper side, a lower side, a left side and a right side separately and are symmetrically distributed at an interval of 90°; and axial lengths of the permanent magnets  4  axially equal to the stator cores are equal to that of the stator cores  2 , and the permanent magnets are symmetrically distributed in four areas divided by the four permanent magnets  3  axially longer than the stator cores. Permanent magnet sections axially longer than the stator cores, left permanent-magnet magnetic bridges  6 , right permanent-magnet magnetic bridges  7 , the magnetic adjusting sections  8 , a radial electromagnetic pole stator  9 , an electromagnetic pole and permanent magnetic pole isolation plate  10 , permanent-magnet two-side magnetic pole connection sections  11 , left permanent-magnet magnetic poles  12 , right permanent-magnet magnetic poles  13 , radial electromagnetic poles  14 , radial electromagnetic pole winding coils  15 , a first radial sensor  16 , a second radial sensor  17  and a radial magnetic bearing rotor  18  belong to the radial magnetic bearing, and the radial magnetic bearing is located on an inner side of the stator winding coil end  1  and keeps a certain distance from the motor rotor  5  in the axial direction. 
     The radial magnetic bearing is shown in  FIGS.  2 A,  2 B,  2 C and  2 D , and two sides of each of the permanent magnet section  301  axially longer than the stator cores, the permanent magnet section  302  axially longer than the stator cores, the permanent magnet section  303  axially longer than the stator cores and the permanent magnet section  304  axially longer than the stator cores are provided with a set of magnetic bridges, that is, the left permanent-magnet magnetic bridge  6  and the right permanent-magnet magnetic bridge  7 , and the axial lengths of the components are identical. Lower portions of the left permanent-magnet magnetic bridges  6  and the right permanent-magnet magnetic bridges  7  are connected to the left permanent-magnet magnetic poles  12  and the right permanent-magnet magnetic poles  13  respectively, and each permanent magnet section axially longer than the stator cores, the left permanent-magnet magnetic bridges  6 , the right permanent-magnet magnetic bridges  7 , the left permanent-magnet magnetic poles  12  and the right permanent-magnet magnetic poles  13  are all made of materials with desirable magnetic conductivity. The left permanent-magnet magnetic poles  12  and the right permanent-magnet magnetic poles  13  are each of a two-section structure, upper ends of the left permanent-magnet magnetic poles  12  and the right permanent-magnet magnetic poles  13  are magnetic conduction sections  12   a  and  13   a  respectively, which are connected to the left permanent-magnet magnetic bridges  6  and the right permanent-magnet magnetic bridges  7 . The magnetic adjusting sections  8  are arranged between the magnetic conduction sections  12   a  and the magnetic conduction sections  13   a , the magnetic adjusting sections  8  are preferably made of magnetic conductive materials, and a bias magnetic field is adjusted by adjusting a magnetic conductivity of the magnetic adjusting sections  8  or an embedded size of the magnetic conduction sections  12   a  and  13   a.    
     The permanent-magnet two-side magnetic pole connection sections  11  and the electromagnetic pole and permanent magnetic pole isolation plate  10  are integrated, and are preferably made of non-magnetic, low-conductivity materials with certain strength and hardness. Electromagnetic pole and permanent magnetic pole isolation plate recesses  10   a , electromagnetic pole and permanent magnetic pole isolation plate recesses  10   c  and electromagnetic pole and permanent magnetic pole isolation plate bosses  10   b  are arranged on one side, close to the magnetic conduction sections  12   a  and  13   a , of the electromagnetic pole and permanent magnetic pole isolation plate  10 , the electromagnetic pole and permanent magnetic pole isolation plate recesses  10   a , the electromagnetic pole and permanent magnetic pole isolation plate recesses  10   c , the magnetic conduction sections  12   a  and  13   a  have equal widths and depths, a radian distance of the electromagnetic pole and permanent magnetic pole isolation plate bosses  10   b  in a circumferential direction is equal to a distance between the magnetic conduction sections  12   a  and  13   a , the magnetic conduction sections  12   a  and  13   a  are embedded into the electromagnetic pole and permanent magnetic pole isolation plate recesses  10   a  and the electromagnetic pole and permanent magnetic pole isolation plate recesses  10   c  respectively, and the electromagnetic pole and permanent magnetic pole isolation plate bosses  10   b  are embedded between the magnetic conduction sections  12   a  and the magnetic conduction sections  13   a . An electromagnetic pole and permanent magnetic pole isolation plate recess  10   a , an electromagnetic pole and permanent magnetic pole isolation plate recess  10   c  and an electromagnetic pole and permanent magnetic pole isolation plate boss  10   b  form a mounting structure for a pair of magnetic conduction sections (magnetic conduction section  12   a  and magnetic conduction section  13   a ), the mounting structures for all pairs of magnetic conduction sections form the annular electromagnetic pole and permanent magnetic pole isolation plate  10 , one permanent-magnet two-side magnetic pole connection section  11  is mounted on an axial rear side of the mounting structure for each pair of magnetic conduction sections, the permanent-magnet two-side magnetic pole connection sections  11  and the electromagnetic pole and permanent magnetic pole isolation plate  10  can be integrally formed, two permanent-magnet two-side magnetic pole connection sections  11  is an arc T-shaped permanent magnet, an electromagnetic pole and permanent magnetic pole isolation plate recess  10   d  is arranged between the adjacent permanent-magnet two-side magnetic pole connection sections  11 , and electromagnetic pole stator bosses  9   a  may be embedded into the electromagnetic pole and permanent magnetic pole isolation plate recesses  10   d . Meanwhile, the left permanent-magnet magnetic poles  12  and the right permanent-magnet magnetic poles  13  are embedded in the electromagnetic pole and permanent magnetic pole isolation plate recesses  10   a  and the electromagnetic pole and permanent magnetic pole isolation plate recesses  10   c , then the permanent-magnet two-side magnetic pole connection sections  11  are embedded between the left permanent-magnet magnetic poles  12  and the right permanent-magnet magnetic poles  13  to form stable sandwich structures. By means of the above components and the preferable recess and boss structures, reliable connection between the components may be achieved. 
     As shown in  FIGS.  2 A- 2 D , the first radial sensor  16  and the second radial sensor  17  are arranged in centers of lower portions of the permanent-magnet two-side magnetic pole connection sections  11 , the first radial sensor  16  and the second radial sensor  17  are distributed at an interval of 90°, are the prior art or existing products, and are configured to measure a radial position of the radial magnetic bearing rotor  18 . The radial electromagnetic pole stator  9  and the radial electromagnetic poles  14  are integrated and made of materials with desirable magnetic conductivity, the four radial electromagnetic poles  14  are symmetrically distributed at an interval of 90°, electromagnetic pole stator bosses  9   a  are arranged on an axial front side of the radial electromagnetic pole stator  9 , and the electromagnetic pole stator bosses  9   a  may be embedded in the electromagnetic pole and permanent magnetic pole isolation plate recesses  10   d . A radial electromagnetic pole winding coil  15  is wound around each radial electromagnetic pole  14 . It can be seen that the four radial electromagnetic poles  14  form a radial magnetic bearing electromagnetic pole with a compact structure and an adjustable bias magnetic field, the four permanent magnet sections axially longer than the stator cores, the magnetic bridges, the magnetic adjusting sections  8 , the permanent-magnet two-side magnetic pole connection sections  11 , the left permanent-magnet magnetic poles  12  and the right permanent-magnet magnetic poles  13  form a radial bias magnetic pole, the radial bias magnetic pole is of an eight-pole structure, the eight magnetic poles are evenly distributed at an interval of 45° and are concentric with the motor, lower ends of the eight magnetic poles are arc surfaces, and air gaps are reserved between the magnetic poles and the radial magnetic bearing rotor  18 . 
     Distribution of a permanent magnet bias magnetic flux and a radial electromagnetic pole magnetic flux is described in detail below in combination with  FIGS.  3 A- 3 B . For the permanent magnet section  301  axially longer than the stator cores, the permanent magnet bias magnetic flux  11  sequentially passes through the permanent magnet section  301  axially longer than the stator cores, the right permanent-magnet magnetic bridge  7 , the magnetic conduction section  13   a , the magnetic adjusting section  8 , the magnetic conduction section  12   a  and the left permanent-magnet magnetic bridge  6 , and the magnetic flux is essentially a short-circuit magnetic flux and does not generate bias force; and the permanent magnet bias magnetic flux  12  sequentially passes through the permanent magnet section  301  axially longer than the stator cores, the right permanent-magnet magnetic bridge  7 , the magnetic conduction section  13   a , the right permanent-magnet magnetic pole  13 , an air gap between the right permanent-magnet magnetic pole  13  and the radial magnetic bearing rotor  18 , the radial magnetic bearing rotor  18 , an air gap between the left permanent-magnet magnetic pole  12  and the magnetic bearing rotor  18 , the magnetic conduction section  12   a  and the left permanent-magnet magnetic bridge  6 , the magnetic flux may generate bias force, such that the magnitude of the permanent magnet bias magnetic flux  11  and the magnitude of the permanent magnet bias magnetic flux  12  may be adjusted by adjusting the magnetic conductivity of the magnetic adjusting section  8  or an embedded size of the magnetic conduction sections  12   a  and  13   a , so as to adjust the magnitude of the bias force. The bias force generated by the permanent magnet section  301  axially longer than the stator cores is in a positive direction of an Y axis, when the radial magnetic bearing rotor  18  is disturbed and moves towards a negative direction of the Y axis, the air gap between the left permanent-magnet magnetic pole  12  and the radial magnetic bearing rotor  18  and the air gap between the right permanent-magnet magnetic pole  13  and the radial magnetic bearing rotor  18  are increased, in order to make the radial magnetic bearing rotor  18  return to an original position anew, currents in opposite directions are introduced into the radial electromagnetic pole winding coil  1501  and the radial electromagnetic pole winding coil  1502 , the radial electromagnetic pole  1401  and the radial electromagnetic pole  1402  jointly generate an electromagnetic pole magnetic flux  13 , electromagnetic force generated by the electromagnetic pole magnetic flux  13  is forward and reverse along the Y axis, and the electromagnetic force and the bias force act together. Analysis of bias force and electromagnetic force in other directions is similar to the process, such that the compact structure may overcome external disturbance, keep the magnetic bearing rotor  18  at a set position, and achieve stable suspension of the radial magnetic bearing rotor  18 . 
     Embodiment 2: Force-balancing axial magnetic bearing with adjustable bias magnetic field for stator permanent magnet motor 
     As shown in  FIGS.  4 A and  4 B , a force-balancing axial magnetic bearing with an adjustable bias magnetic field for a stator permanent magnet motor in Embodiment 2 of the present disclosure is mounted on a stator permanent magnet motor. A stator winding coil end  1 , stator cores  2 , a permanent magnet  3  axially longer than the stator cores, permanent magnets  4  axially equal to the stator cores, a motor rotor  5  and a motor rotating shaft  19  are basic components of the stator permanent magnet motor, and except for the permanent magnet  3  axially longer than the stator core, other components have dimensions, materials, and structures known to those skilled in the art. A structure of the stator permanent magnet motor is identical to that in Embodiment 1 and is not repeated herein. 
     What is different from Embodiment 1 is: permanent magnet sections axially longer than the stator cores, left permanent-magnet magnetic conduction members  6 , right permanent-magnet magnetic conduction members  7 , magnetic adjusting sections  8 , an axial electromagnetic pole stator  20 , an electromagnetic pole and permanent magnetic pole isolation plate  10 , permanent-magnet two-side magnetic pole grooved connection sections, left permanent-magnet grooved magnetic poles  23 , right permanent-magnet grooved magnetic poles  24 , a first axial sensor  25 , a second axial sensor  26 , axial electromagnetic pole winding coils  27 , axial electromagnetic poles  28 , thrust disc reinforcing members  29  and a thrust disc  30  belong to the axial magnetic bearing, the axial magnetic bearing is wholly located on an inner side of a stator winding coil end  1  and keeps a certain distance from the motor rotor  5  in an axial direction, and an exploded view of the components is shown in  FIG.  5   . 
     The axial magnetic bearing is shown in  FIG.  5   , two sides of each permanent magnet section  301  axially longer than the stator cores are provided with a set of magnetic conduction members which are respectively a left permanent-magnet magnetic conduction member  6  and a right permanent-magnet magnetic conduction member  7 , and axial lengths of the components are identical. Lower portions of the left permanent-magnet magnetic conduction members  6  and the right permanent-magnet magnetic conduction members  7  are connected to the left permanent-magnet grooved magnetic poles  23  and the right permanent-magnet grooved magnetic poles  24  respectively, all of which are all made of materials with desirable magnetic conductivity. The left permanent-magnet grooved magnetic poles  23  and the right permanent-magnet grooved magnetic poles  24  are each of a two-section structure and are provided with magnetic conduction sections  23   a  and magnetic conduction sections  24   a  as upper ends respectively, the magnetic conduction sections  23   a  and the magnetic conduction sections  24   a  are connected to the left permanent-magnet magnetic bridges  6  and the right permanent-magnet magnetic bridges  7 , lower ends of the left permanent-magnet grooved magnetic poles and the right permanent-magnet grooved magnetic poles are provided with groove structures for the thrust disc  30  to be embedded in, and the grooves divide the left permanent-magnet grooved magnetic poles  23  and the right permanent-magnet grooved magnetic poles  24  into rear axial permanent magnetic poles  23   b  and  24   b  and front axial permanent magnetic poles  23   c  and  24   c . One magnetic adjusting section  8  is arranged between the magnetic conduction sections  23   a  and  24   a  and is preferably made of magnetic conductive materials, and a bias magnetic field of the permanent magnetic poles is adjusted by adjusting the magnetic conductivity of the magnetic adjusting sections  8  or an embedded size of the magnetic conduction sections  23   a  and  24   a . The permanent-magnet two-side magnetic pole grooved connection sections and the electromagnetic pole and permanent magnetic pole isolation plate  10  are an integral component and preferably made of materials which are non-magnetic-conductive, low in conductivity and certain in strength and hardness, one side, close to the magnetic conduction sections  23   a  and  24   a , of the electromagnetic pole and permanent magnetic pole isolation plate  10  is provided with electromagnetic pole and permanent magnetic pole isolation plate recesses  10   a , electromagnetic pole and permanent magnetic pole isolation plate recesses  10   c , and electromagnetic pole and permanent magnetic pole isolation plate bosses  10   b . Preferably, the electromagnetic pole and permanent magnetic pole isolation plate recesses  10   a , the electromagnetic pole and permanent magnetic pole isolation plate recesses  10   c  and the magnetic conduction sections  23   a  and  24   a  have equal widths and depths, a radian distance of the electromagnetic pole and permanent magnetic pole isolation plate bosses  10   b  in a circumferential direction is equal to a distance between the magnetic conduction sections  23   a  and  24   a , a front axial permanent-magnet two-side magnetic pole connector  22   b  and a rear axial permanent-magnet two-side magnetic pole connector  22   a  form a permanent-magnet two-side magnetic pole grooved connection section, the electromagnetic pole and permanent magnetic pole isolation plate recesses  10   a , the electromagnetic pole and permanent magnetic pole isolation plate recesses  10   c  and the electromagnetic pole and permanent magnetic pole isolation plate bosses  10   b  are formed by grooving the front axial permanent-magnet two-side magnetic pole connectors  22   b , the magnetic conduction sections  23   a  and  24   a  are embedded in the electromagnetic pole and permanent magnetic pole isolation plate recesses  10   a  and the electromagnetic pole and permanent magnetic pole isolation plate recesses  10   c , and then the electromagnetic pole and permanent magnetic pole isolation plate bosses  10   b  are embedded between the magnetic conduction sections  23   a  and  24   a . Meanwhile, the rear axial permanent-magnet two-side magnetic pole connectors  22   a  are embedded between the left permanent-magnet grooved magnetic poles  23  and the right permanent-magnet grooved magnetic poles  24  to form stable sandwich structures. By means of the above components and the preferable recess and boss structures, reliable connection between the components may be achieved. Four permanent-magnet two-side magnetic pole grooved connection sections are symmetrically distributed at an interval of 90°, a groove provided in each permanent-magnet two-side magnetic pole grooved connection section along a center is used for the thrust disc  30  to be arranged, and according to a principle of minimum reluctance, the rear axial permanent magnetic poles  23   b  and  24   b  and the thrust disc  30  form a closed path of the permanent magnetic flux, the front axial permanent magnetic poles  23   c  and  24   c  and the thrust disc  30  form a closed path of the permanent magnetic flux. 
     Two permanent-magnet two-side magnetic pole grooved connection sections are selected and the first axial sensor  25  and the second axial sensor  26  are implanted into lower portions of the rear axial permanent-magnet two-side magnetic pole connector  22   a  and the front axial permanent-magnet two-side magnetic pole connector  22   b , the first axial sensor  25  (or the second axial sensor  26 ) includes two sensors to detect axial displacement or distance of the thrust disc  30  respectively, the first axial sensor  25  and the second axial sensor  26  form a fault-tolerant set, and axial displacement or distance detection errors caused by local deformation of the thrust disc or failure of part of the sensors are prevented. The first axial sensor  25  and the second axial sensor  26  are in the prior art or products in the prior art. 
     The axial electromagnetic pole stator  20  and the axial electromagnetic poles  28  are integrated and made of materials with desirable magnetic conductivity, and the four axial electromagnetic poles  28  are symmetrically distributed at an interval of 90° . A groove is provided in each axial electromagnetic pole  28  along a center position, the thrust disc  30  is arranged in the grooves, each groove divides the corresponding axial electromagnetic pole  28  into two magnetic poles, that is, a rear axial electromagnetic pole  28   a  and a front axial electromagnetic pole  28   b , and an axial electromagnetic pole winding coil  27   b  and an axial electromagnetic pole winding coil  27   a  are wound around the rear axial electromagnetic pole  28   a  and the front axial electromagnetic pole  28   b  respectively. 
     It can be seen that four axial electromagnetic poles  28  form an electromagnetic pole of the axial force and bias force-balancing axial magnetic bearing of a stator permanent magnet motor, four permanent magnet sections axially longer than the stator cores and the magnetic bridges thereof, the magnetic adjusting sections  8 , the permanent-magnet two-side magnetic pole grooved connection sections  22 , the left permanent-magnet grooved magnetic poles  23  and the right permanent-magnet grooved magnetic poles  24  form the permanent magnetic pole, the axial magnetic bearing is of an eight-pole structure, the eight magnetic poles are evenly distributed at an interval of 45°, and lower ends of the eight magnetic poles are arc surfaces. 
     As shown in  FIG.  6   , as for the permanent magnetic pole, preferably, a length d 1  of a rear air gap between the permanent magnetic pole and a thrust disc reinforcing member is equal to a length d 2  of a front air gap between the permanent magnetic pole and the thrust disc reinforcing member, that is, d 1 =d 2 ; and a length w 1  of a rear air gap between the permanent magnetic pole and a thrust disc and a length w 2  of a front air gap between the permanent magnetic pole and the thrust disc are set as adjustable values for bias force adjustment. 
     As for the axial electromagnetic pole, preferably, a length d 3  of a rear air gap between the axial electromagnetic pole and the thrust disc reinforcing member is equal to a length d 4  of a front air gap between the axial electromagnetic pole and the thrust disc reinforcing member, that is, d 3 =d 4 ; a length w 3  of a rear air gap between the axial electromagnetic pole and the thrust disc is equal to d 1 , that is, w 3 =d 1 ; and a length w 4  of a front air gap between the axial electromagnetic pole and the thrust disc is equal to d 2 , that is, w 4 =d 2 . 
     Preferably, d 1 »w 1  , or d 1 »w 2 , and a length h 1  of a rear air gap between the permanent magnetic pole and the thrust disc=d 1 . 
     The thrust disc  30  and the two thrust disc reinforcing members  29  arranged on two sides are all of annular structures, the two thrust disc reinforcing members  29  may fasten the thrust disc  30 , the thrust disc  30  has an outer diameter larger than that of the thrust disc reinforcing members  29  and an inner diameter equal to that of the thrust disc reinforcing member and further equal to an outer diameter of a motor rotating shaft  19 . 
     Preferably, the thrust disc  30  and the thrust disc reinforcing members  29  are made of silicon steel sheets and other materials with desirable magnetic conductivity and low conductivity and may serve as independent components or an integral component. Under the condition that the thrust disc  30  has an outer diameter smaller than the outer diameter of the motor rotating shaft  19  and a larger axial length, the thrust disc reinforcing member  29  may be omitted. 
       FIG.  7 A  is a schematic diagram of a permanent magnet bias magnetic pole and magnetic flux of the axial magnetic bearing in Embodiment 2 of the present disclosure. As shown in  FIG.  7 B , a permanent magnetic pole magnetic flux  14  passes through the permanent magnet section  301  axially longer than the stator cores, the left permanent-magnet magnetic bridge  6 , the magnetic adjusting section  8  and the right permanent-magnet magnetic bridge  7  to form a loop, and the magnetic flux does not pass through the thrust disc  30 . As shown in  FIGS.  7 B and  7 C , a permanent magnetic pole magnetic flux  15  passes through the permanent magnet section  301  axially longer than the stator cores, the left permanent-magnet magnetic bridge  6 , the left permanent-magnet grooved magnetic pole  23 , the thrust disc  30 , the right permanent-magnet grooved magnetic pole  24  and the right permanent-magnet magnetic bridge  7  to form a loop, the magnetic flux passes through the thrust disc  30 , and more specifically, the permanent magnetic pole magnetic flux is divided into two branches of magnetic flux, where one path passes through the rear axial permanent magnetic poles  23   b  and  24   b , and the other path passes through the front axial permanent magnetic poles  23   c  and  24   c.    
     Obviously, by adjusting the magnetic conductivity of the magnetic adjusting sections  8  or the embedded size of the magnetic conduction sections  23   a  and  24   a , the magnitude of the permanent magnetic pole magnetic flux  14  and the permanent magnetic pole magnetic flux  15  may be changed; and the length w 1  of the rear air gap between the permanent magnetic pole and the thrust disc and the length w 2  of the front air gap between the permanent magnetic pole and the thrust disc are adjusted by changing a position of the thrust disc mounted on the motor rotating shaft, and the magnitude of the axial bias force is determined by the magnitude of two branch magnetic fluxes of the permanent magnetic pole magnetic flux  14 . 
       FIGS.  8 A,  8 B and  8 C  are schematic diagrams of an electromagnetic pole and a magnetic flux loop of the axial force and bias force-balancing axial magnetic bearing of a stator permanent magnet motor. When currents are introduced into the axial electromagnetic pole winding coils  27 , an axial electromagnetic pole magnetic flux  16  passes through the rear axial electromagnetic pole  28   a , the thrust disc  30 , the front axial electromagnetic pole  28   b  and the axial electromagnetic pole stator  20  to form a loop. 
     With further reference to  FIGS.  7 A- 7 C and  8 A- 8 C , it can be seen that the permanent magnetic pole magnetic flux and the axial electromagnetic pole magnetic flux flow through different paths, and decoupling isolation of the permanent magnetic pole magnetic flux and the electromagnetic pole magnetic flux is achieved by means of the electromagnetic pole and permanent magnetic pole isolation plate  10 , such that the two magnetic fluxes have the advantages of being low in coupling degree and beneficial to control. 
     In conjunction with  FIGS.  6  and  9   , a basic principle for balancing axial force and bias force when Embodiment 2 is used in a device with the axial force is described in detail. According to the analysis, the magnetic adjusting sections  8  may change the magnitude of the permanent magnetic pole magnetic flux  14  and the magnitude of the permanent magnetic pole magnetic flux  15 , the air gap lengths w 1  and w 2  may be used for adjusting the magnitude of two branch magnetic fluxes of the permanent magnetic pole magnetic flux, and the magnitude of the branch magnetic fluxes may determine the bias force of the axial magnetic bearing. In  FIG.  9   , an abscissa d (unit: mm) represents a distance from the thrust disc  30  to the rear axial permanent magnetic poles  23   b  and  24   b  (or the front axial permanent magnetic poles  23   c  and  24   c ), an ordinate represents the magnitude of the bias force F (unit: kN), and characteristic curves  1 ,  2 ,  3  are the bias force characteristic curves when the magnetic adjusting sections  8  are adjusted. The characteristic curve  1  represents the bias force when the magnetic conductivity of the magnetic adjusting sections  8  is zero (or the embedded size of the magnetic conduction sections  23   a  and  24   a  is zero), the characteristic curve  2  represents the bias force when the magnetic conductivity of the magnetic adjusting sections  8  is increased to be equal to that of the magnetic conduction sections  23   a  and  24   a  and the embedded size of the magnetic conduction sections  23   a  and  24   a  is one third of that of the magnetic conduction sections, and the characteristic curve  3  represents the bias force when the magnetic conductivity of the magnetic adjusting sections  8  is increased to be equal to that of the magnetic conduction sections  23   a  and  24   a  and the embedded size of the magnetic conduction sections  12   a  and  13   a  is half of that of the magnetic conduction sections. Obviously, by changing the magnetic conductivity of the magnetic adjusting sections  8  and the embedded size of the magnetic conduction sections  23   a  and  24   a , a cluster of bias force characteristic curves may be obtained. 
     Without loss of generality, d is set to range from 0 mm to 2 mm. It can be seen that the bias force presents a regular distribution trend with different d or adjustment of the magnetic adjusting sections  8 : (1) when a distance between the thrust disc  30  and the rear axial permanent magnetic poles  23   b  and  24   b  (or the front axial permanent magnetic poles  23   c  and  24   c ) is smaller, that is, d≈ 0  (or d≈ 2 ), an absolute value of the bias force F is larger; (2) the absolute values of a maximum value and a minimum value of the bias force F are not equal due to different reluctances of two branches of the permanent magnetic pole magnetic flux; (3) when the thrust disc  30  is located at the center of the rear axial permanent magnetic poles  23   b  and  24   b  and the front axial permanent magnetic poles  23   c  and  24   c , that is, d=1, the bias force is not equal to zero, the magnitude of the bias force depends on a difference of the reluctances of the two branches, and the larger the difference is, the larger the absolute value of the bias force is; and ( 4 ) plus and minus signs of the bias force indicate the directions of the bias force. 
     According to the distribution features, when the axial force and bias force-balancing axial magnetic bearing of a stator permanent magnet motor is used for an apparatus, with axial force, for example, a centrifugal fan, a centrifugal impeller, etc. in the background technology, the stator permanent magnet motor serves as a power motor, the axial force of the apparatus during operation may be computed according to a working mode, a load feature, a rotation direction and a mounting mode of the apparatus, then the bias force most suitable for the working mode, the load feature, the rotation direction and the mounted mode is selected by looking up a bias force characteristic curve cluster similar to that in FIG.  FIG.  9   , then, a magnetic conductivity of the magnetic adjusting sections, an embedded size of the magnetic conduction sections and relative distances between the thrust disc and the front permanent magnetic pole and between the thrust disc and the rear permanent magnetic pole are adjusted according to the bias force, so as to generate the selected bias force, the bias force is balanced with the axial force generated during operation without the bias force, and magnetic field potential of the permanent magnetic poles is exerted to the maximum extent. When the bias force is not enough to balance the axial force, currents are introduced into the electromagnetic pole coils, and electromagnetic force and the bias force of the permanent magnetic poles act together to balance the axial force. During actual operation, when an axial position deviates from a balance position, external disturbance may be overcome only by controlling the magnitude of the currents in the rear axial electromagnetic poles  28   a  and the front axial electromagnetic poles  28   b , and the thrust disc  30  is kept at a set position, such that stability of the thrust disc  30  of the magnetic bearing is achieved. 
     In the description of the present disclosure, the terms, “front”, “rear”, “left”, “right”, “inner”, “outer”, “upper”, “lower”, etc. indicate azimuthal or positional relations based on those shown in the drawings only for ease of description of the present disclosure, and are not intended to indicate or imply that the referenced device or element must have a particular orientation, and thus may not be construed as a limitation on the present disclosure. 
     The above description is not intended to limit the present disclosure, as long as the magnetic field energy of the permanent magnets of the stator permanent magnet motor is introduced into the radial magnetic bearing, any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present disclosure, for example, the number of stator permanent magnets is modified to be other reasonable numbers, or the number of permanent magnet bias magnetic poles are set to be one, two and three, should fall within the scope of protection of the present disclosure. 
     In addition, it should be noted that in order to facilitate the description of the present disclosure and help those skilled in the art to understand the specific embodiment of the present disclosure, only a stator, a rotor and a magnetic bearing of a stator permanent magnet motor are given in the accompanying drawings, parts and structures of a motor housing, a motor end cover, a mechanical protection bearing, a cooling structure, etc. which are necessary for constituting such products as the magnetic bearing motor are not mentioned, but the above are not intended to limit the present disclosure, and typical features of such products are emphatically and clearly given. As long as the magnetic field energy of the permanent magnets of the stator permanent magnet motor is introduced into the magnetic bearing and a bias magnetic flux is generated by means of introduced permanent magnet energy, any modification, equivalent replacement, improvement, etc. made within the spirit and principles of the present disclosure, for example, the number of stator permanent magnets is modified into other reasonable numbers, or the axial magnetic bearing in the present disclosure is modified into an axial and radial hybrid magnetic bearing by adjusting d 1 , d 2 , d 3 , d 4 , w 1 , w 2 , w 3 , w 4  and h 1 , should fall within the scope of protection of the present disclosure. 
     The above description of the disclosed embodiments make those skilled in the art implement or use the present disclosure. Various modifications to these embodiments will be readily apparent to those skilled in the art, and generic principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present disclosure. Thus, the present disclosure is not to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.