CN112303121B

CN112303121B - Magnetic suspension pump with three-degree-of-freedom magnetic bearing

Info

Publication number: CN112303121B
Application number: CN202011162483.7A
Authority: CN
Inventors: 阮晓东; 朱超宁; 胡亮; 付新; 苏芮
Original assignee: Zhejiang University ZJU
Current assignee: Zhejiang University ZJU
Priority date: 2020-10-27
Filing date: 2020-10-27
Publication date: 2021-09-28
Anticipated expiration: 2040-10-27
Also published as: CN112303121A

Abstract

The invention relates to a magnetic suspension pump with a three-degree-of-freedom magnetic bearing, which comprises the three-degree-of-freedom magnetic bearing and a rotary driving component, wherein the three-degree-of-freedom magnetic bearing plays a role in suspending and positioning a rotor and an impeller, and the rotary driving component has an outer rotor structure; the method is mainly used for solving the unstable phenomenon of the rotor in the axial direction when the two-degree-of-freedom bearingless motor is applied to a pump. And the coupling problem existing between the suspension winding flux linkage and the driving winding flux linkage is improved, and the control difficulty of the motor is reduced. The structure is compact, and the device is convenient to be applied to occasions with high cleanliness; the rotary driving winding is not coupled with the magnetic linkage of the suspension winding, so that the control is convenient.

Description

Magnetic suspension pump with three-degree-of-freedom magnetic bearing

Technical Field

The invention relates to the technical field of magnetic suspension pumps, in particular to a magnetic suspension pump with a three-degree-of-freedom magnetic bearing.

Background

In the fields of semiconductor manufacturing, high purity chemical industry, biomedicine, and the like, there are many cases where a high-purity fluid is required. Magnetic levitation pumps are increasingly used in various industries because of their unique principle advantages. In the field of life sciences, magnetic suspension blood pumps have been used as artificial hearts because they can prevent blood cells from being damaged to cause hemolysis, blood coagulation, and thrombosis. In biotechnology, magnetic suspension pumps are widely used in sterilization processes because they do not have any viable or small gaps for bacteria, making them ideal pumps for biochemical applications. For example, a chemical solution supply system in a lithography machine is an important functional unit of a wafer cleaning machine, and the required ultra-clean environment requires that a corresponding liquid pump has the characteristics of chemical corrosion resistance, no generation of pollution particles, small overall dimension, high output pressure, high flow rate and the like. Therefore, at present, the magnetic suspension liquid pump becomes a core flow control component of a semiconductor machine platform for immersion lithography, cleaning, glue spreading and development and the like. As a fluid power source, the magnetic suspension pump has the characteristic of less pollution, and is widely applied to a high-purity fluid system. The basic principle of the magnetic suspension pump is to combine the rotor of the motor with the pump impeller, drive the rotor to rotate by using the magnetic field, and suspend the rotor in the pump cavity without the help of bearings by using the magnetic field. Due to the non-contact driving mode and the magnetic suspension positioning mode, the rotor does not rub with a solid in rotation, can be coated with high-cleanliness materials such as high-cleanliness stainless steel or Polytetrafluoroethylene (PTFE), generates few pollutants, and is particularly suitable for high-cleanliness occasions.

At present, most of motors contained in the magnetic suspension pump are two-degree-of-freedom bearingless thin-sheet motors. For example, the permanent magnet thin-sheet motor in the magnetic suspension centrifugal pump produced by Levitronix can realize active control suspension with two degrees of freedom in the radial direction, and suspension with three degrees of freedom other than the radial degree and the rotational degree of freedom of a rotor is realized by utilizing magnetic resistance. Because the other three degrees of freedom are passively suspended and cannot realize active control, the change of the pump flow easily causes unstable operation of the motor rotor in the other three degrees of freedom. Due to the structural limitation, if the magnetic suspension pump runs, the rotor is easy to deviate at the axial position, so that the problems of unstable running of the water pump, unstable pump liquid and the like are caused.

If the three-degree-of-freedom magnetic suspension motor is applied to the magnetic suspension pump, the defect that the two-degree-of-freedom magnetic suspension motor cannot provide stable axial force can be improved to a great extent, but the relative position between the motor or the driving winding and the three-degree-of-freedom magnetic bearing greatly influences the performance of the motor. For example, chinese patent publication No. CN107547010A discloses an electromagnetic bearing switched reluctance motor system and a control method, which are not suitable for a motor of a magnetic suspension pump due to the problems of the three-degree-of-freedom bearing and the motor, such as the incompact structure, the redundant structure of the rotor, and the like. Another patent, for example, chinese patent publication No. CN101207310A, discloses an axial active suspension three-degree-of-freedom bearingless alternating-pole permanent magnet motor, in which the mathematical models of the suspension force and the driving force are complex, and the suspension winding of the magnetic bearing and the driving winding of the motor are integrated in the same closed magnetic circuit, so that the magnetic linkage of the suspension winding and the magnetic linkage of the driving winding are coupled, and when the load of the motor is large and the current in the driving winding is large, strong coupling exists between the torque control and the suspension control, thereby greatly increasing the difficulty of the control.

Disclosure of Invention

In order to overcome the defects of the prior art, the invention provides a magnetic suspension pump with a three-degree-of-freedom magnetic bearing, which comprises the three-degree-of-freedom magnetic bearing and an outer rotor permanent magnet synchronous motor. The method is mainly used for solving the unstable phenomenon of the rotor in the axial direction when the two-degree-of-freedom bearingless motor is applied to a pump. And the coupling problem existing between the suspension winding flux linkage and the driving winding flux linkage is improved, and the control difficulty of the motor is reduced. And provides a reasonable and compact three-freedom-degree magnetic suspension motor structure which can be applied to a magnetic suspension centrifugal pump.

The invention comprises a pump head, a three-degree-of-freedom magnetic bearing and a rotary driving component;

the pump head is a cavity for containing and transferring pumped fluid, the pump head is provided with a liquid inlet and a liquid outlet, and an impeller is arranged in the pump head;

the three-degree-of-freedom magnetic bearing comprises an outer iron core, an axial suspension winding, a radial magnetizing permanent magnet ring, an annular stator iron core and an annular rotor iron core; the annular rotor iron core is positioned inside the pump head; the outer iron core is an annular component with a C-shaped section, and two opening end surfaces of the outer iron core are adjacent to and opposite to two axial end surfaces of the annular rotor iron core; the inner part of the outer iron core contains an axial suspension winding, a radial magnetizing permanent magnet ring and an annular stator iron core, the annular stator iron core and the annular rotor iron core are concentrically arranged, and the radial inner side surface of the annular stator iron core is adjacent to and opposite to the radial outer side surface of the annular rotor iron core; a radial magnetizing permanent magnet ring is arranged between the annular stator iron core and the outer iron core; the axial suspension windings are annular and are arranged concentrically with the outer iron core, and two or more axial suspension windings are respectively arranged on the outer sides of the two axial ends of the radial magnetizing permanent magnet ring; the radial suspension windings are wound on the protruding parts on the radial inner sides of the annular stator cores, and a plurality of radial suspension windings are arranged in a centrosymmetric manner;

the annular rotor iron core of the three-degree-of-freedom magnetic bearing is also used as a rotor magnetic yoke of the rotary driving assembly, and the rotary driving assembly further comprises a rotor permanent magnet and a central stator; the rotor permanent magnet is positioned inside the pump head; the central stator is positioned at the radial inner side of the annular rotor iron core and positioned outside the pump head; the central stator is in a gear-shaped structure, and a plurality of gear teeth are respectively wound with stator windings; the rotor permanent magnets are arranged on the radial outer side of the central stator in an annular uniform distribution mode;

the impeller, the annular rotor iron core and the rotor permanent magnet are connected into a whole.

Furthermore, each gear tooth of the central stator is wound into a stator winding by a conducting wire, the stator windings which are mutually connected in series are combined into a phase stator winding, and all the stator windings on the central stator are combined into a three-phase stator winding; the phase axes of each phase are spatially separated by 120 electrical degrees and have the same number of coil turns effective.

Preferably, the annular stator core and the annular rotor core are formed by laminating annular silicon steel sheets.

Furthermore, the rotor permanent magnet is attached to the inner side surface of the annular rotor iron core.

Further, the number of slots of the central stator is not equal to the number of pole pairs of the rotor permanent magnet.

Further, at least 4 radial suspension windings are included.

Preferably, the internal surface of the pump head is of high cleanliness stainless steel or polytetrafluoroethylene or meltable polytetrafluoroethylene material.

Preferably, the impeller, the annular rotor core and the rotor permanent magnet are embedded in high-cleanliness stainless steel or polytetrafluoroethylene or fusible polytetrafluoroethylene material.

Preferably, the impeller is made of high-cleanliness stainless steel or polytetrafluoroethylene or meltable polytetrafluoroethylene materials by using an injection molding process, and wraps the annular rotor iron core and the rotor permanent magnet.

The invention provides a magnetic suspension pump with a three-degree-of-freedom magnetic bearing, which comprises the three-degree-of-freedom magnetic bearing and a rotary driving component. The rotary driving component has an outer rotor structure, the flywheel has obvious filtering effect, the fluctuation of the running torque is small, and the magnet on the rotor is not easy to fall off under the action of centrifugal force, so that the rotor structure is more stable; the magnetic bearing rotor and the motor rotor share one magnetic steel, so that the structure is compact; the rotor has simple structure, is beneficial to injection molding and packaging so as to be applied to high-cleanliness use occasions; the magnetic bearing plays a role in positioning the rotor in the xyz direction, and the rotor of the rotary driving component is combined with the rotor of the magnetic bearing and is integrated with the pump impeller in an injection molding manner, so that the rotation angle, the angular velocity and the displacement in the xyz direction of the rotor, the rotation angle, the angular velocity and the displacement in the xyz direction of the rotor are kept consistent, and the rotor is more beneficial to the accurate control of the whole rotor; the rotary driving winding and the suspension winding are separated from each other in the magnetic circuit, so that the mutual coupling of the magnetic chains of the rotary driving winding and the suspension winding during control is avoided, the control difficulty is reduced, and the control accuracy is improved; the rotary driving winding is decoupled from the suspension winding, so that the heat dissipation area of a winding coil is increased, and the long-term stable use of the winding is facilitated; the central stator adopts a fractional slot structure to effectively reduce the fluctuation amplitude of the cogging torque.

Drawings

FIG. 1 is a schematic axial view of a magnetic levitation pump

FIG. 2 is a schematic cross-sectional view of a magnetic levitation pump;

FIG. 3 is a schematic view of a rotor impeller of a magnetic suspension pump

FIG. 4 is an axial cross-sectional schematic view of a three-degree-of-freedom magnetic bearing;

FIG. 5 is a schematic view of an axial magnetic circuit of the three-degree-of-freedom magnetic bearing;

fig. 6 is a schematic view of a radial magnetic circuit of the three-degree-of-freedom magnetic bearing.

Detailed Description

The invention is further described below with reference to the accompanying drawings.

As shown in fig. 1, 2, 3 and 4, the present invention relates to a magnetic suspension pump, which includes a pump head PH, a three-degree-of-freedom magnetic bearing MB and a rotary drive assembly MT.

The pump head PH is composed of a cavity and contents thereof, wherein the cavity is formed by the surrounding of a pump cover 1A and a pump shell 1B; a rotor 20 is arranged in the pump head PH, the rotor 20 comprises an impeller 2, an annular rotor core 8 and a rotor permanent magnet 9, the impeller 2 is used for driving water to rotate so that the water can be pumped to the outside of the pump due to centrifugal force, the impeller 2 can be arranged in a manner of referring to the existing centrifugal pump scheme, and the annular rotor core 8 and the rotor permanent magnet 9 are arranged as described in the following rotary driving component MT; the pump head PH contains fluid therein, and in order to meet the requirements of corrosion resistance, high cleanliness and the like for fluid transportation, the inner surface of the pump head PH and the outer surface of the rotor 20 may be made of materials such as high cleanliness stainless steel, Polytetrafluoroethylene (PTFE), or fusible Polytetrafluoroethylene (PFA); the materials can be covered on the inner surface of the pump head PH and the outer surface of the rotor 20 by the technology of surface coating, etc., or the materials can be directly adopted to obtain the materials of the pump cover 1A, the pump shell 1B, the impeller 2, etc. by the direct forming of the processes of injection molding, etc., and the annular rotor iron core 8 and the rotor permanent magnet 9 are embedded and wrapped; the pump head also includes a fluid inlet 101 and a fluid outlet 102.

The three-degree-of-freedom magnetic bearing MB comprises an outer iron core 3, an axial suspension winding 4, a radial suspension winding 5, a radial magnetizing permanent magnet ring 6, an annular stator iron core 7 and an annular rotor iron core 8; the outer iron core 3 is an annular component with a C-shaped section, and two opening end surfaces 31 of the outer iron core 3 are adjacent to and opposite to two axial end surfaces of the annular rotor iron core 8; the axial suspension winding 4, the radial suspension winding 5, the radial magnetizing permanent magnet ring 6 and the annular stator core 7 are accommodated in the outer core 3, the annular stator core 7 and the annular rotor core 8 are concentrically arranged, and the radial inner side surface of the annular stator core 7 is adjacent to and opposite to the radial outer side surface of the annular rotor core 8; a radial magnetizing permanent magnet ring 6 is arranged between the annular stator iron core 7 and the outer iron core 3; the axial suspension windings 4A and 4B are annular and are arranged concentrically with the outer iron core 3, and the axial suspension windings 4A and 4B are respectively arranged on the outer sides of the two axial ends of the radial magnetizing permanent magnet ring 6; the radial levitation winding 5 is wound on a projection portion on the radially inner side of the annular stator core 7, and a plurality of radial levitation windings 5 are arranged in a central symmetry, and as shown in fig. 4, 4

radial levitation windings

5A, 5B, 5C, and 5D may be arranged in a central symmetry. The radial suspension function is realized by the outer iron core 3, the radial magnetizing permanent magnet ring 6, the annular stator iron core 7, the radial suspension winding 5 and the annular rotor iron core 8, and the axial suspension function is realized by the outer iron core 3, the axial suspension winding 4A, the axial suspension winding 4B, the radial magnetizing permanent magnet ring 6 and the annular rotor iron core 8. The annular stator core 7 and the annular rotor core 8 are formed by laminating annular silicon steel sheets.

The rotary driving component MT comprises an annular rotor iron core 8, a rotor permanent magnet 9 and a central stator 10; the annular rotor iron core 8 is used as a rotor magnetic yoke of the rotary driving component MT, the plurality of rotor permanent magnets 9 are annularly and uniformly distributed on the radial outer side of the central stator 10, the more the number of the set rotor poles is, the more the number of the rotor permanent magnets 9 is, so that the stress on the inner surface of the annular rotor iron core 8 is smaller when the rotor 20 rotates at a high speed, and the long-term reliable use of the rotor 20 is more facilitated; the rotor permanent magnet 9 is attached to the inner side surface of the annular rotor core 8, and when the rotor 20 rotates at a high speed, the rotor permanent magnet 9 tends to be attached to the annular stator core 8 under the action of centrifugal force, so that the rotor permanent magnet 9 is prevented from shifting, and the long-term reliable use of the rotor 20 is facilitated. The central stator 10 is positioned at the radial inner side of the annular rotor iron core 8 and the rotor permanent magnet 9 and is positioned outside the pump head PH; the shape of the central stator 10 is gear-shaped, each gear tooth (coil slot) is wound into a stator winding by a conducting wire, the mutually-connected stator windings are combined into a one-phase stator winding, and all the stator windings on the central stator 10 are combined into a three-phase stator winding; the phase axes of each phase have an electrical angle difference of 120 degrees in space, and the phase axes have the same effective number of turns of the coil, so that the electromotive force and the magnetomotive force of each phase are symmetrical; in the embodiment shown in fig. 4, the number of slots of the central stator 10 is 12, the number of pole pairs of the rotor permanent magnets 9 is 14, the number of slots of each pole and each phase is 2/7, and fractional slot windings are adopted, so that the fluctuation amplitude of the cogging torque is effectively reduced by using the fractional slot windings, and more stable torque characteristics can be obtained.

Principle of axial levitation control of the rotor referring to fig. 5, Φ PM is the static bias flux generated by the radially magnetized permanent magnet ring 6, Φ ZEM is the control flux generated by the current in the axial control coils 4A and 4B, and the air gap flux is composed of these two parts of flux. Φ PMz1 and Φ PMz2 are the magnetic fluxes of the permanent magnet 6 at the air gap z1 and at the air gap z2, respectively. The magnetic field generates surface tension, maxwell force, at the boundary of magnetic substances with different magnetic permeability. The relationship between maxwell force and flux can be found as:

in the formula, Fz1 and Fz2 are respectively electromagnetic attraction force applied to the upper surface and the lower surface of the suction disc; phi z1 and phi z2 are respectively composite magnetic fluxes generated at the upper air gap and the lower air gap; sz is the area of the axial magnetic pole; mu.s₀Is the permeability of air. When the permanent magnet is suspended stably in the axial direction, the upper attraction force generated by the permanent magnet at the upper air gap z1 of the rotor and the lower air gap z2 of the rotor is balanced with the sum of the lower attraction force and the gravity, namely Fz1 is equal to Fz2+ mg; if the rotor is subjected to a downward external disturbance force in the balance position, the rotor moves downwards from the reference position to cause the change of the magnetic fluxes of the upper and lower air gaps generated by the permanent magnet, namely the lower air gap is reduced, the magnetic flux phi PMz2 generated by the permanent magnet is increased, the upper air gap is increased, and the magnetic flux phi PMz1 generated by the permanent magnet is reduced; before the control magnetic flux Φ ZEM is not generated, Fz1<Fz2+ mg. The rotor moves downwards due to external disturbance, the displacement of the rotor from the balance position is detected by using a sensor at the moment, a controller converts a displacement signal into a control signal, a power amplifier converts the control signal into a control current i, and the control current flows through the axial suspension windings 4A and 4B to generate an electromagnetic magnetic flux phi ZEM in the iron core; at the upper air gap Z1, the flow directions of the excitation magnetic flux and the permanent magnetic flux are the same, and the excitation magnetic flux Φ ZEM is overlapped with the permanent magnetic flux Φ PMz1, so that the total magnetic flux at the air gap Z1 is increased, namely Φ Z1 is Φ PMz1+ Φ ZEM; the excitation magnetic flux Φ ZEM is opposite to the flow direction of the permanent magnetic flux Φ PMz1 at the lower air gap Z2, so the total magnetic flux at the air gap Z2 is reduced to Φ Z2 — Φ PMz2 — Φ ZEM. With increasing flux at the upper gap, and with the lower gapAnd the magnetic flux at the gap is reduced, and the whole rotor receives an upward resultant force, and the rotor moves upwards and returns to a stable suspension position. If the rotor is subjected to an upward external disturbance force, analysis can be carried out by a similar method, the upward external disturbance force enables the upper air gap to be reduced, the lower air gap to be increased, the sensor detects the offset of the position of the rotor, and the controller sets a control current i to be led into the axial suspension windings 4A and 4B in a direction opposite to the situation that the rotor is subjected to the downward external disturbance force, so that an electromagnetic flux phi ZEM resisting the upward movement of the rotor is generated in the iron core, and the rotor is urged to return to the balance position. Therefore, no matter the rotor is disturbed upwards or downwards, the rotor of the permanent magnet biased axial magnetic bearing system with position negative feedback can always keep the rotor at a balanced position by controlling the current in the excitation windings 4A and 4B through the controller and adjusting the magnitude of the upper air gap flux and the lower air gap flux.

The radial levitation control principle of the rotor is shown in fig. 6, where the path of the magnetic flux in the X direction is indicated, Φ PM is the static bias magnetic flux generated by the radially magnetized permanent magnet ring 6, Φ XEM is the control magnetic flux in the X direction, and the path of the magnetic flux in the Y direction can be indicated by the same method. When the magnetic bearing rotor is axially stabilized in suspension, the magnetic bearing rotor is in a suspended intermediate position under the static magnetic field attraction force generated by the permanent magnets, which is also referred to as a reference position. Due to the structural symmetry, the magnetic flux generated by the radial magnetizing permanent magnet ring 6 is equal at the air gap on the left side of the rotor and the air gap on the right side of the rotor, namely phi PMx1 and phi PMx2, and the left and right suction forces are equal at the moment. If the rotor is subjected to a rightward external disturbance force in the balance position, the rotor deviates from the reference position and moves rightward, so that the magnetic flux of left and right air gaps generated by the permanent magnet is changed, namely the left air gap is increased, the magnetic flux phi PMx1 generated by the permanent magnet is reduced, the right air gap is reduced, and the magnetic flux phi PMx2 generated by the permanent magnet is increased; at this time, the amount of displacement of the rotor from its reference position is detected by the sensor, and the excitation magnetic flux Φ XEM is generated by controlling the current to flow through the

electromagnet coil windings

5A and 5B. The excitation magnetic flux Φ XEM coincides with the magnetic flux direction at the left air gap, and the magnetic flux Φ x1 at the left air gap is increased after superposition. And the excitation magnetic flux phi XEM has the opposite direction to the magnetic flux phi x2 at the right air gap, and the magnetic flux phi x2 at the right air gap is reduced after superposition. Therefore, the rotor is subjected to resultant force in the left direction, and is expressed as leftward movement, and finally returns to the reference position; if the rotor is subjected to an external disturbance force towards the left, the analysis can be carried out by a similar method, current is introduced to the

radial suspension windings

5A and 5B in the direction opposite to the condition that the rotor is subjected to the disturbance force towards the right, and electromagnetic force resisting the leftward movement of the rotor is generated to urge the rotor to return to the reference position; thus, the rotor is maintained at the reference position in the x-axis direction by controlling the currents in the

radial levitation windings

5A, 5B; similarly, the rotor is maintained at the reference position in the y-axis direction by controlling the

radial levitation windings

5C and 5D; by controlling the

radial levitation windings

5A, 5B, 5C and 5D, the rotor can be maintained in a reference position regardless of the direction of the radial force to which the rotor is subjected.

When the axis of the rotor deviates, the x-axis suspension is realized by controlling the

coil windings

5A and 5B, and the y-axis suspension is realized by controlling the

coil windings

5C and 5D; when the rotor deviates in the axial direction, the coil windings 4A and 4B can be controlled to control the rotor to realize the suspension of the z axis; in this way, a three-degree-of-freedom magnetic bearing, i.e. a three-degree-of-freedom magnetic bearing MB, is formed.

After the magnetic suspension pump is started, the rotor 20 is suspended in the pump head PH by using a three-degree-of-freedom magnetic bearing MB; by utilizing control methods such as Space Vector Pulse Width Modulation (SVPWM), sinusoidal current generated by an inverter is introduced into a three-phase winding of the central stator 10, and after the central stator 10 is introduced with driving current, a rotating magnetic field is generated to drive the annular rotor iron core 8 and the rotor permanent magnet 9 to rotate so as to drive the impeller 2 to rotate; when the impeller 2 rotates rapidly, the fluid in the pump obtains a linear velocity, and then the fluid is pumped out of the outlet 102 of the pump, and new fluid flows in from the inlet 101 of the pump, and finally the function of pumping fluid is realized.

In the positional relationship description of the present invention, the appearance of terms such as "inner", "outer", "upper", "lower", "left", "right", etc., indicating the orientation or positional relationship based on the orientation or positional relationship shown in the drawings is merely for convenience of describing the embodiments and simplifying the description, and does not indicate or imply that the device or element referred to must have a specific orientation, be constructed in a specific orientation and operation, and thus, is not to be construed as limiting the present invention.

The foregoing summary and structure are provided to explain the principles, general features, and advantages of the product and to enable others skilled in the art to understand the invention. The foregoing examples and description have been presented to illustrate the principles of the invention and are intended to provide various changes and modifications within the spirit and scope of the invention as claimed. The scope of the invention is defined by the appended claims and equivalents thereof.

Claims

1. A magnetic suspension pump with a magnetic bearing with three degrees of freedom is characterized in that: the three-degree-of-freedom magnetic bearing comprises a pump head, a three-degree-of-freedom magnetic bearing and a rotary driving component;

2. A magnetic suspension pump having magnetic bearings with three degrees of freedom according to claim 1, wherein: each gear tooth of the central stator is wound into a stator winding by a conducting wire, the stator windings which are mutually connected in series are combined into a one-phase stator winding, and all the stator windings on the central stator are combined into a three-phase stator winding; the phase axes of each phase are spatially separated by 120 electrical degrees and have the same number of coil turns effective.

3. A magnetic suspension pump having magnetic bearings with three degrees of freedom according to claim 1, wherein: the annular stator iron core and the annular rotor iron core are formed by laminating annular silicon steel sheets.

4. A magnetic suspension pump having magnetic bearings with three degrees of freedom according to claim 1, wherein: the rotor permanent magnet is attached to the inner side surface of the annular rotor iron core.

5. A magnetic suspension pump having magnetic bearings with three degrees of freedom according to claim 1, wherein: the number of slots of the central stator is not equal to the number of pole pairs of the rotor permanent magnet.

6. A magnetic suspension pump having magnetic bearings with three degrees of freedom according to claim 1, wherein: at least 4 radial suspension windings are included.

7. A magnetic suspension pump having magnetic bearings with three degrees of freedom according to claim 1, wherein: the internal surface of the pump head is of a high cleanliness stainless steel or polytetrafluoroethylene material.

8. A magnetic suspension pump having magnetic bearings with three degrees of freedom according to claim 1, wherein: the impeller, the annular rotor iron core and the rotor permanent magnet are embedded in high-cleanliness stainless steel or polytetrafluoroethylene materials.

9. A magnetic suspension pump having magnetic bearings with three degrees of freedom according to claim 8, wherein: the impeller is made of high-cleanliness stainless steel or polytetrafluoroethylene materials by using an injection molding process and wraps the annular rotor iron core and the rotor permanent magnet.