CN115224903A - Mixed excitation type bearingless switched reluctance motor - Google Patents

Abstract

The application provides a mix excitation formula bearingless switched reluctance motor, including first stator, rotor and second stator, the inboard of first stator of second stator embedding, the rotor is located between first stator and the second stator, all be provided with the air gap between first stator and the rotor and between rotor and the second stator to make the rotor rotate between first stator and second stator, first stator adopts mixed stator pole structure, the rotor adopts cylindrical structure, the second stator adopts salient pole structure, including eight salient poles and four permanent magnet blocks, wherein the permanent magnet block sets up inside second stator core. The problems that the torque and the suspension force control performance of a traditional bearingless switched reluctance motor are reduced, the control difficulty is increased, and the efficiency is reduced due to the fact that magnetic fluxes generated by suspension force poles in different directions are mutually coupled and exciting currents are introduced into windings to generate a bias magnetic field are solved.

Description

Mixed excitation type bearingless switched reluctance motor

Technical Field

The application belongs to the technical field of motors, and particularly relates to a hybrid excitation type bearingless switched reluctance motor.

Background

With the rapid development of power electronic technology, the switched reluctance motor and the speed regulating system thereof are widely applied. The switched reluctance motor is particularly suitable for high-speed and ultrahigh-speed operation because of the advantages of simple structure, no winding of the rotor, high mechanical strength, wide speed regulation range and the like. However, the rotor of the conventional switched reluctance motor is supported by a mechanical bearing, and the mechanical bearing is abraded and heated seriously due to high-speed operation, so that the service life of the mechanical bearing is greatly reduced, and the reliability of a motor system is further reduced.

The bearingless switched reluctance motor combines the switched reluctance motor and a bearingless technology, not only keeps the advantages of simple structure, low cost, strong fault tolerance and the like of the switched reluctance motor, but also has the excellent characteristics of long service life, large output power and the like of the bearingless motor, and has wide application prospect in the field of high-speed driving. However, the torque and the levitation force of the conventional bearingless switched reluctance motor are mutually coupled, and the magnetic fluxes generated by the levitation force poles in different directions are mutually coupled, so that the torque and levitation force control performance of the motor is influenced, and the control difficulty of the motor is greatly increased. Meanwhile, in order to generate the required suspension force, the traditional bearingless switched reluctance motor needs to introduce exciting current into a winding to generate a bias magnetic field, so that the loss of the motor is increased, and the efficiency is reduced.

Disclosure of Invention

Therefore, the technical problem to be solved by the present application is to provide a hybrid excitation type bearingless switched reluctance motor, which can solve the problems of reduced control performance, increased control difficulty, and reduced efficiency of the torque and the levitation force of the motor caused by the mutual coupling of the torque and the levitation force control, the mutual coupling of magnetic fluxes generated by levitation force poles in different directions, and the generation of a bias magnetic field by passing excitation current through windings of the conventional bearingless switched reluctance motor.

In order to solve the above problems, the present application provides a hybrid excitation bearingless switched reluctance motor, including a first stator, a rotor, and a second stator, where the second stator is embedded inside the first stator, the rotor is located between the first stator and the second stator, and air gaps are provided between the first stator and the rotor and between the rotor and the second stator, so that the rotor rotates between the first stator and the second stator;

the first stator adopts a mixed stator pole structure;

the rotor adopts a cylindrical structure;

the second stator adopts a salient pole structure, wherein the salient pole structure comprises a permanent magnet block, a second stator core and a suspension winding coil, the suspension winding coil is wound on a salient pole of the second stator core, and the permanent magnet block is arranged in the second stator core;

optionally, the rotor is of a cylindrical structure, the cylindrical structure includes eight rotor blocks, rotor magnetism isolating rings and annular iron cores, the rotor blocks are uniformly embedded outside the rotor magnetism isolating rings at equal intervals along the circumferential direction of the rotor magnetism isolating rings, and the annular iron cores are embedded inside the rotor magnetism isolating rings, so that the rotor magnetism isolating rings separate magnetic fluxes circulating between the rotor and the first stator and magnetic fluxes circulating between the rotor and the second stator;

the rotor blocks are fan-shaped, the eight rotor blocks are identical in size and shape, and the inner surface and the outer surface of the rotor are smooth.

Optionally, the number of the permanent magnet blocks is four, the size and the shape of the permanent magnet blocks are the same, the second stator is provided with eight salient poles, and the size and the shape of the eight salient poles are the same; the four permanent magnet blocks are arranged in the second stator core in an orthogonal manner along the circumferential direction, each permanent magnet block is positioned on a central line between two salient poles, the four permanent magnet blocks are magnetized in the circumferential direction, the magnetizing directions of the two permanent magnet blocks with symmetrical axes are the same, and the magnetizing directions of the two adjacent permanent magnet blocks are opposite;

and a magnetic isolation bridge is arranged on a center line position between two adjacent permanent magnet blocks, and suspension winding coils on salient poles of the second stator iron core between two adjacent magnetic isolation bridges are connected to form one phase.

Optionally, the number of turns of the suspension winding coil is the same, and the suspension winding coil is a centralized winding.

Optionally, the first stator adopts a hybrid stator pole structure, the hybrid stator pole structure includes an excitation pole and an auxiliary pole, both the excitation pole and the auxiliary pole are formed by extending the inner wall of the first stator inwards along the radial direction, wherein the number of the excitation pole and the number of the auxiliary pole are six, and the excitation pole and the auxiliary pole are identical in size and shape;

six field poles and six auxiliary poles are all crossed along the circumferential direction of the first stator and are arranged on the inner side of the first stator at equal intervals, wherein the pole arc width of the field pole is larger than the pole arc width which is twice of the auxiliary poles.

Optionally, the torque winding coil I, the torque winding coil II, the torque winding coil III, the torque winding coil IV, the torque winding coil V, and the torque winding coil VI are respectively wound on the six excitation poles, and the winding directions of all the torque winding coils are the same, wherein the number of turns of the torque winding coils is the same, and the torque winding coils are all centralized windings.

Alternatively, the torque winding coils of two diametrically opposite poles of the first stator are connected to form one phase.

Optionally, the first stator, the rotor block, the annular iron core and the second stator iron core are made of materials with magnetic conductivity;

the rotor magnetism isolating ring is made of a material without magnetic conductivity;

the torque winding coil I, the torque winding coil II, the torque winding coil III, the torque winding coil IV, the torque winding coil V, the torque winding coil VI and the suspension winding coil are made of copper wires with conductive performance;

the permanent magnet blocks are made of permanent magnets with remanence.

Advantageous effects

The embodiment of the invention provides a hybrid excitation type bearingless switched reluctance motor which comprises a first stator, a rotor and a second stator, wherein eight rotor blocks and an annular iron core on the rotor and the first stator and the second stator respectively form an outer unit motor and an inner unit motor, and a rotor magnetic isolation ring and a magnetic isolation bridge are matched. In addition, the outer unit motor of this application adopts blocking rotor and mixed stator pole structure, has shortened the magnetic flux route, has improved the magnetic flux utilization ratio and has eliminated the reversal magnetic flux in the stator when the torque winding current commutation, and then has improved the output torque of motor and has reduced the iron core loss of motor, and the inner unit motor of this application adopts the permanent-magnet block to provide bias magnetic field simultaneously, has reduced the running loss of motor, so the mixed excitation formula bearingless switched reluctance motor of this application can improve the operating efficiency of motor.

Drawings

Fig. 1 is a schematic diagram of an overall structure of a hybrid excitation type bearingless switched reluctance motor according to an embodiment of the present application;

fig. 2 is a schematic structural diagram of a first stator according to an embodiment of the present application;

FIG. 3 is a schematic structural diagram of a rotor according to an embodiment of the present application;

FIG. 4 is a schematic structural diagram of a second stator according to an embodiment of the present application;

fig. 5 is a structural diagram illustrating an assembled state of the hybrid excitation type bearingless switched reluctance motor according to the embodiment of the present application;

FIG. 6 is a schematic diagram of the flux path for supplying power to the torque winding coil in accordance with an embodiment of the present application;

fig. 7 is a schematic view of the magnetic flux path for supplying power to the levitation winding coil in an embodiment of the present application.

The reference numbers are given as:

1. a first stator; 10. an exciter pole; 11. an auxiliary electrode;

2. a rotor; 20. a rotor block; 21. a rotor magnetism isolating ring; 22. an annular iron core;

3. a second stator; 30. a permanent magnet block; 31. a second stator core; 32. a suspension winding coil;

4. a torque winding coil; 4a, a torque winding coil I;4b, a torque winding coil II;4c, a torque winding coil III;4d, a torque winding coil IV;4e, a torque winding coil V;4f, torque winding coil VI;

5. and a magnetic isolation bridge.

Detailed Description

Referring to fig. 1 to 7 in combination, according to an embodiment of the present application, a hybrid excitation bearingless switched reluctance motor includes a first stator 1, a rotor 2, and a second stator 3, the second stator 3 is embedded inside the first stator 1, the rotor 2 is located between the first stator 1 and the second stator 3, and air gaps are provided between the first stator 1 and the rotor 2 and between the rotor 2 and the second stator 3, so that the rotor 2 rotates between the first stator 1 and the second stator 3;

the first stator 1 adopts a mixed stator pole structure, the mixed stator pole structure comprises an exciter pole 10 and an auxiliary pole 11, and the exciter pole 10 and the auxiliary pole 11 are both formed by extending the inner wall of the first stator 1 inwards along the radial direction;

the rotor 2 adopts a cylindrical structure, wherein the cylindrical structure comprises rotor blocks 20, rotor magnetism isolating rings 21 and annular iron cores 22, the number of the rotor blocks 20 is eight, the rotor blocks 20 are uniformly embedded outside the rotor magnetism isolating rings 21 at equal intervals along the circumferential direction of the rotor magnetism isolating rings 21, and the annular iron cores 22 are embedded inside the rotor magnetism isolating rings 21, so that the rotor magnetism isolating rings 21 separate the magnetic flux circulating between the rotor 2 and the first stator 1 and the magnetic flux circulating between the rotor 2 and the second stator 3;

the second stator 3 adopts a salient pole structure, wherein the salient pole structure comprises a permanent magnet block 30, a second stator core 31 and a suspension winding coil 32, the suspension winding coil 32 is wound on the salient pole of the second stator core 31, and the permanent magnet block 30 is embedded in the second stator core 31;

the rotor 2 is arranged between the first stator 1 and the second stator 3, the rotor 2 rotates between the first stator 1 and the second stator 3, eight rotor blocks 20 and an annular iron core 22 on the rotor 2 and the first stator 1 and the second stator 3 respectively form an outer unit motor and an inner unit motor, and a rotor magnetism isolating ring 21 and a magnetism isolating bridge 5 are matched. In addition, the outer unit motor of the hybrid excitation type bearingless switched reluctance motor adopts a structure of a block rotor and a hybrid stator pole, so that a magnetic flux path is shortened, the utilization rate of the magnetic flux is improved, reverse magnetic flux in a stator is eliminated when the current of a torque winding coil 4 is in phase commutation, the output torque of the motor is improved, and the iron core loss of the motor is reduced; meanwhile, the inner unit motor of the hybrid excitation type bearingless switched reluctance motor adopts the permanent magnet blocks 30 to provide a bias magnetic field, so that the operation loss of the motor is reduced, and the operation efficiency of the motor can be improved.

Further, the first stator 1 is located at the outermost side, the second stator 3 is located at the innermost side, the rotor 2 is located between the first stator 1 and the second stator 3, and air gaps are respectively arranged between the first stator 1 and the rotor 2 and between the rotor 2 and the second stator 3, wherein the air gaps are equal-gap air gaps, that is, the air gap between the first stator 1 and the rotor 2 is equal to the air gap between the rotor 2 and the second stator 3.

As shown in fig. 2 and 5, the first stator 1 adopts a hybrid stator pole structure, and includes six field poles 10 having the same shape and size and six auxiliary poles 11 having the same shape and size, which are distributed inside the first stator 1 at equal intervals along the circumferential direction. The pole arc width of the exciter pole 10 is greater than twice the pole arc width of the auxiliary pole 11.

Further, the torque winding coil I4a, the torque winding coil II4b, the torque winding coil III4c, the torque winding coil IV4d, the torque winding coil V4e and the torque winding coil VI4f are respectively wound on the six poles 10 in a concentrated winding form for generating the rotation torque, and the number of turns of the torque winding coils 4 on all the poles 10 is the same, and the winding directions are the same. In addition, the torque winding coil 4 of the two diametrically opposite poles 10 of the first stator 1 is connected to form one phase, for example, the torque winding coil I4a and the torque winding coil IV4d are connected to form one phase, the torque winding coil II4b and the torque winding coil V4e are connected to form one phase, and the torque winding coil III4c and the torque winding coil VI4f are connected to form one phase.

Further, the auxiliary pole 11 is wound with neither the winding coil 4 nor the permanent magnet, and they provide a return path only for the magnetic flux generated by the torque winding coil 4.

As shown in fig. 3 and 5, the rotor 2 has a cylindrical structure, and includes eight rotor blocks 20, rotor magnetism isolating rings 21 and annular iron cores 22. Eight rotor blocks 20 are embedded at equal intervals outside the rotor magnetism isolating ring 21, and the annular iron core 22 is embedded inside the rotor magnetism isolating ring 21. The rotor magnetism isolating ring 21 not only plays a role of fixing the rotor block 20 and the annular iron core 22, but also can separate magnetic flux generated by the torque winding coil 4 from magnetic flux generated by the suspension winding coil 32, thereby realizing natural decoupling of torque and suspension force control, further reducing the control difficulty of the motor and improving the control performance of the motor torque and the suspension force. In addition, the inner and outer surfaces of the rotor 2 are smooth without any bulge, so that the rotor can generate stable suspension force at any rotating position, and the suspension force control performance can be further improved. Meanwhile, when the motor rotates at a high speed, the structure of the rotor 2 is beneficial to reducing wind friction loss and improving the working efficiency of the motor.

Furthermore, the eight rotor blocks 20 are adopted in the rotor 2, so that the motor has lower operation frequency, and further, the motor generates smaller iron core loss when running at high speed, and the operation efficiency of the whole motor system is improved. In addition, the eight rotor blocks 20 of the rotor 2 can make the torque waveforms generated by two adjacent rotor blocks 20 overlapped with the same field pole 10 inconsistent and cross and overlapped with each other, thereby being beneficial to reducing the torque pulsation of the motor.

As shown in fig. 4 and 5, the second stator 3 has a salient pole structure and includes permanent magnet blocks 30, a second stator core 31, and a levitation winding coil 32.

Further, the number of the permanent magnet blocks 30 is four, the size and the shape of the permanent magnet blocks 30 are the same, and the second stator 3 is provided with eight magnetic poles.

Further, eight salient poles on the second stator core 31 are uniformly distributed on the outer side of the second stator core 31, the eight salient poles are equal in size and shape, a suspension winding coil 32 with the same number of turns is wound on each salient pole to control suspension force, and the winding directions of the eight salient poles on each salient pole are the same.

Further, four permanent magnet blocks 30 having the same shape and size are embedded in the second stator core 31 to provide a bias magnetic field. Four permanent magnet blocks 30 are orthogonally distributed in the circumferential direction inside the second stator core 31, and each permanent magnet block 30 is located on the center line between two salient poles. The four permanent magnet blocks 30 are magnetized in the circumferential direction, the magnetizing directions of the two axially symmetric permanent magnet blocks 30 are the same, and the magnetizing directions of the two adjacent permanent magnet blocks 30 are opposite. And a magnetic isolation bridge 5 is arranged at the central line position between two adjacent permanent magnet blocks 30 and is used for separating the magnetic fields generated by the two permanent magnet blocks 30. In addition, the levitation winding coil 32 on the salient pole of the second stator core 31 between the adjacent two magnetic bridges 5 is connected to constitute one phase.

Furthermore, the permanent magnet block 30 is adopted to replace the exciting current in the traditional bearingless switched reluctance motor to generate a bias magnetic field, so that the copper consumption of the motor can be effectively reduced, and the working efficiency of the whole motor system is further improved.

As shown in fig. 6, the torque winding coil I4a and the torque winding coil IV4d are connected to form a phase, and when power is supplied to the torque winding coil I4a and the torque winding coil IV4d, the magnetic flux generated by the phase starts from the field pole 10, passes through the air gap, and forms a closed loop through the rotor block 20 and the auxiliary pole 11. The magnetic flux path is short, leakage magnetic flux can be effectively reduced, the utilization rate of the magnetic flux is improved, and the output torque of the motor is further improved. Meanwhile, due to the rotor magnetism isolating ring 21, the magnetic fluxes generated by the torque winding coil I4a and the torque winding coil IV4d do not enter the toroidal core 22 and the second stator 3. In addition, when the torque winding current is switched from one phase to another phase, no reverse magnetic flux exists in the first stator 1, which is beneficial to reducing the core loss and further improving the motor efficiency.

As shown in fig. 7, when the levitation winding coil 32 is not energized, the magnetic flux generated by the permanent magnet blocks 30 starts from the permanent magnet blocks 30, passes through one salient pole of the second stator core 31, passes through the air gap, and forms a closed loop through the annular core 22 and the adjacent salient pole of the second stator core 31, as shown by the long dashed line in the figure, when the magnetic field in the air gap of the motor is uniformly and symmetrically distributed, the motor does not generate levitation force. When the levitation winding coil 32 is energized, it produces a magnetic flux as shown by the dotted line in the figure. The magnetic flux generated by the levitation winding coil 32 interacts with the magnetic flux generated by the permanent magnet blocks 30 to cause an asymmetric magnetic field distribution in the motor air gap, thereby generating a levitation force. Therefore, by controlling the magnitude and direction of the current in the different levitation winding coils 32, the desired levitation force can be generated.

Further, as shown in fig. 7, due to the rotor magnetism isolating ring 21 and the magnetism isolating bridge 5, the magnetic fluxes generated by the permanent magnet block 30 and the suspension winding coil 32 do not enter the rotor block 20 and the first stator 1, nor enter the adjacent suspension force poles, so that the magnetic flux coupling between the suspension force poles in different directions in the conventional bearingless switched reluctance motor is eliminated, and the control difficulty of the suspension force of the motor can be reduced.

Furthermore, the first stator 1, the rotor block 20, the annular iron core 22 and the second stator iron core 31 are made of electrical thin steel plates with good magnetic conductivity, such as electrical pure iron, electrical silicon steel sheets DW350, DR470, DR510, 35PN440, 35PN210 and M19, which are punched and laminated;

the rotor magnetism isolating ring 21 is made of non-magnetic materials such as aluminum, steel and titanium alloy;

the torque winding coil I4a, the torque winding coil II4b, the torque winding coil III4c, the torque winding coil IV4d, the torque winding coil V4e, the torque winding coil VI4f and the suspension winding coil 32 are made of copper wires with good electric conductivity which are wound and then dipped in paint and dried;

the permanent magnet block 30 is made of a permanent magnet of neodymium iron boron NdFeB, samarium cobalt (SmCo) or AlNiCo with high remanence.

The utility model provides a mixed excitation formula bearingless switched reluctance motor, including first stator 1, rotor 2 and second stator 3, eight rotor blocks 20 and annular iron core 22 on the rotor 2 constitute outer unit motor and interior unit motor respectively with first stator 1 and second stator 3, add the cooperation of rotor magnetic isolation ring 21 and magnetic isolation bridge 5 in addition, compare with traditional bearingless switched reluctance motor, this motor thoroughly separates the magnetic flux that torque winding coil 4 and suspension winding coil 32 produced, and separate the magnetic flux that the suspension force pole of equidirectional not produced, the natural decoupling zero of torque and suspension force control has been realized, the natural decoupling zero of the suspension force control of different directions has been realized, and then the control degree of difficulty of motor has been reduced, the torque and the suspension force control performance of motor have been improved. In addition, the outer unit motor adopts a structure of a block rotor and a mixed stator pole, so that a magnetic flux path is shortened, the utilization rate of magnetic flux is improved, and reverse magnetic flux in a stator is eliminated when the current of the torque winding coil 4 is in phase commutation, so that the output torque of the motor is improved, and the iron core loss of the motor is reduced; meanwhile, the inner unit motor adopts the permanent magnet blocks 30 to provide a bias magnetic field, so that the running loss of the motor is reduced, and the running efficiency of the motor can be improved by the hybrid excitation type bearing-free switched reluctance motor.

It is readily understood by a person skilled in the art that the advantageous ways described above can be freely combined, superimposed without conflict.

Claims (9)

1. A hybrid excitation type bearingless switched reluctance motor is characterized by comprising a first stator (1), a rotor (2) and a second stator (3), wherein the second stator (3) is embedded into the inner side of the first stator (1), the rotor (2) is positioned between the first stator (1) and the second stator (3), and air gaps are respectively arranged between the first stator (1) and the rotor (2) and between the rotor (2) and the second stator (3) so that the rotor (2) can rotate between the first stator (1) and the second stator (3);

the first stator (1) adopts a mixed stator pole structure;

the rotor (2) adopts a cylindrical structure;

the second stator (3) adopts a salient pole structure, wherein the salient pole structure comprises a permanent magnet block (30), a second stator core (31) and a suspension winding coil (32), the suspension winding coil (32) is wound on the salient pole of the second stator core (31), and the permanent magnet block (30) is arranged inside the second stator core (31).

2. The hybrid excitation bearingless switched reluctance motor according to claim 1, wherein the rotor (2) has a cylindrical structure including rotor blocks (20), rotor nonmagnetic rings (21), and annular cores (22), the number of the rotor blocks (20) being eight, the rotor blocks (20) being embedded at equal intervals in the circumferential direction of the rotor nonmagnetic rings (21) on the outer side of the rotor nonmagnetic rings (21), and the annular cores (22) being embedded on the inner side of the rotor nonmagnetic rings (21), so that the rotor nonmagnetic rings (21) separate the magnetic flux circulating between the rotor (2) and the first stator (1) and the magnetic flux circulating between the rotor (2) and the second stator (3);

the rotor blocks (20) are fan-shaped, the eight rotor blocks (20) are identical in size and shape, and the inner surface and the outer surface of the rotor (2) are smooth.

3. The hybrid excitation bearingless switched reluctance motor according to claim 1, wherein the number of the permanent magnet blocks (30) is four, the size and shape of the permanent magnet blocks (30) are the same, the second stator (3) is provided with eight salient poles, and the size and shape of the eight salient poles provided on the second stator core (31) are the same.

4. The hybrid excitation bearingless switched reluctance motor according to claim 1, wherein four permanent magnet blocks (30) are embedded inside the second stator core (31), the four permanent magnet blocks (30) are distributed inside the second stator core (31) orthogonally along a circumferential direction, each permanent magnet block (30) is located on a center line between two salient poles, the four permanent magnet blocks (30) are circumferentially magnetized, the magnetizing directions of two axially symmetric permanent magnet blocks (30) are the same, and the magnetizing directions of two adjacent permanent magnet blocks (30) are opposite;

and magnetic isolation bridges (5) are arranged on the central line position between two adjacent permanent magnet blocks (30), and suspension winding coils (32) on salient poles of the second stator iron core (31) between two adjacent magnetic isolation bridges (5) are connected to form one phase.

5. The hybrid excitation bearingless switched reluctance machine according to claim 1, wherein the levitation winding coils (32) have the same number of turns and are all concentrated windings.

6. The hybrid excitation bearingless switched reluctance motor according to claim 1, wherein the first stator (1) adopts a hybrid stator pole structure comprising an excitation pole (10) and an auxiliary pole (11), both the excitation pole (10) and the auxiliary pole (11) are formed by extending the inner wall of the first stator (1) to the inner side in the radial direction, wherein the number of the excitation pole (10) and the auxiliary pole (11) is six and the size and shape are the same;

six excitation poles (10) and six auxiliary poles (11) are arranged on the inner side of the first stator (1) at equal intervals along the circumferential direction of the first stator (1), wherein the pole arc width of the excitation pole (10) is larger than the pole arc width which is twice of the auxiliary pole (11).

7. The hybrid excitation bearingless switched reluctance machine according to claim 6, wherein the six poles (10) are wound with a torque winding coil I (4 a), a torque winding coil II (4 b), a torque winding coil III (4 c), a torque winding coil IV (4 d), a torque winding coil V (4 e) and a torque winding coil VI (4 f), respectively, and the winding directions of all the torque winding coils (4) are the same, wherein the number of turns of the torque winding coils (4) is the same and the torque winding coils are all concentrated windings.

8. The hybrid excitation bearingless switched reluctance machine according to claim 7, wherein the torque winding coils (4) of the two diametrically opposite poles (10) of the first stator (1) are connected to form one phase.

9. The hybrid excitation bearingless switched reluctance machine according to claim 1, wherein the first stator (1), the rotor block (20), the annular core (22) and the second stator core (31) are made of materials having magnetic permeability;

the rotor magnetism isolating ring (21) is made of a material without magnetic conductivity;

the torque winding coil I (4 a), the torque winding coil II (4 b), the torque winding coil III (4 c), the torque winding coil IV (4 d), the torque winding coil V (4 e), the torque winding coil VI (4 f) and the suspension winding coil (32) are all made of copper wires with electric conductivity;

the permanent magnet block (30) is made of permanent magnets with remanence.

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