Modularized five-degree-of-freedom magnetic suspension compressor rotor system

Abstract

The invention discloses a modular five-degree-of-freedom magnetic suspension compressor rotor system and a control method, and belongs to the field of compressor rotors, the modular five-degree-of-freedom magnetic suspension compressor rotor system comprises a magnetic suspension rotor main shaft and a driving motor arranged in the middle of the magnetic suspension rotor main shaft, and a centrifugal impeller and a cooling impeller are installed at the two ends of the magnetic suspension rotor main shaft correspondingly; the magnetic suspension rotor main shaft between the driving motor and the centrifugal impeller and the magnetic suspension rotor main shaft between the driving motor and the cooling impeller are respectively and sequentially provided with an axial magnetic bearing assembly and a radial magnetic bearing assembly; the axial magnetic bearing assembly is of a non-thrust disc structure in which a magnetic field is directly coupled; the radial magnetic bearing assembly is of a modular structure with partitioned magnetic poles. According to the modularized five-degree-of-freedom magnetic suspension compressor rotor system and the control method, the axial magnetic bearing assembly directly coupled with the magnetic field is adopted, a thrust disc is omitted, the assembly process of the axial magnetic bearing is simplified, meanwhile, the partitioned magnetic poles are adopted, redundancy control is achieved, and stability is higher.

Description

Technical Field

[0001] The invention relates to the technical field of compressor rotors, and in particular to a modular five-degree-of-freedom magnetic suspension compressor rotor system. Background Art

[0002] Compressors are widely used in air conditioning, refrigeration equipment and hydrogen production equipment. They are also widely used in textile, metallurgy, chemical, fermentation, glass, pharmaceutical and paper industries. Magnetic levitation compressors use magnetic levitation technology and magnetic bearings to suspend the compressor rotor in a magnetic field, thereby achieving contactless operation. This design reduces the energy loss and noise caused by mechanical bearing friction in traditional compressors, and improves the efficiency and reliability of the system.

[0003] Existing magnetic levitation compressors usually use an axial thrust magnetic bearing and two radial magnetic levitation bearings to achieve stable suspension of the rotor. The axial thrust magnetic bearing consists of two stators and a thrust plate. The above structure requires that during the assembly process, one of the stators is installed first, and then the thrust plate is installed on the shaft using a thermal assembly process, and finally the other stator is installed. It can be seen that assembly is difficult and it is not easy to disassemble when a fault occurs. In addition, the existence of the thrust plate limits the maximum speed of the rotor, which will cause greater losses during operation.

[0004] Although radial magnetic bearings have been proven to have sufficient reliability, there have been many cases of bearing system failure, resulting in rotor falls. In order to improve the reliability of radial magnetic bearings, two types of redundant designs are usually adopted: one is an independent redundant structure design, that is, an independent spare bearing is designed. If the original bearing fails, the spare bearing will start to continue to provide support. This design method increases the difficulty of assembly, maintenance and manufacturing costs due to the increased structural complexity. The other is an analytical redundant structure, that is, according to the different pole failure characteristics, the useful parts of the remaining structure are selected and configured to reconstruct the support. This design requires each pole to be independent, and each pole must be equipped with a power amplifier, which increases the power consumption and manufacturing cost of the magnetic bearing system. Summary of the invention

[0005] The purpose of the present invention is to provide a modular five-degree-of-freedom magnetic suspension compressor rotor system and a control method to solve the above-mentioned technical problems.

[0006] To achieve the above-mentioned objectives, the present invention provides a modular five-degree-of-freedom magnetic levitation compressor rotor system, including a magnetic levitation rotor main shaft and a drive motor arranged in the middle of the magnetic levitation rotor main shaft, a centrifugal impeller and a cooling impeller are respectively installed at both ends of the magnetic levitation rotor main shaft, and an axial magnetic bearing assembly and a radial magnetic bearing assembly are sequentially arranged on the magnetic levitation rotor main shaft between the drive motor and the centrifugal impeller and on the magnetic levitation rotor main shaft between the drive motor and the cooling impeller. The axial magnetic bearing assembly is a thrust plate-free structure with direct magnetic field coupling; the radial magnetic bearing assembly is a modular structure with block-type magnetic poles.

[0007] Preferably, the axial magnetic bearing assembly comprises an axial rotor assembly sleeved on the outside of the magnetic suspension rotor main shaft and an axial stator assembly sleeved on the outside of the axial rotor assembly, and an air gap is left between the axial rotor assembly and the axial stator assembly; The axial stator assembly comprises an axial stator core and an axial coil winding, wherein the axial coil winding is wound between two axial stator magnetic poles on the axial stator core; The axial rotor assembly includes an axial rotor core and an axial rotor magnetic pole integrally formed with the surface of the axial rotor core; The axial stator poles overlap with the axial rotor poles in the axial part, and the overlapping width is 1 / 5 of the width of the axial rotor poles or the axial stator poles, and the overlapping directions of the two axial magnetic bearing assemblies located on both sides of the drive motor are opposite.

[0008] Preferably, the radial magnetic bearing assembly comprises retaining frames at both ends and a modular radial magnetic pole assembly, a radial coil winding and a radial rotor core lamination arranged in an installation cavity surrounded by the retaining frames at both ends from outside to inside, wherein the modular radial magnetic pole assembly comprises a plurality of E-shaped magnetic poles uniformly arranged in a circular array on the inner wall of one of the retaining frames, an intermediate pole is arranged at the middle position of the inner arc side of each E-shaped magnetic pole, side poles are axially symmetrically arranged on both sides of the intermediate pole, the width of the intermediate pole is twice the width of the side pole, and radial coil windings are wound around the intermediate pole and the side pole; After the radial coil winding is energized, an SNS magnetic pole is formed to form an electromagnetic circuit from the middle pole, the radial rotor core laminations, the side poles to the return middle pole.

[0009] Preferably, two magnetic pole grooves are opened on the outer arc side of one of the E-shaped magnetic poles, and the two magnetic pole grooves are respectively located between the two side poles and the middle pole, and permanent magnets are arranged in the magnetic pole grooves, and the N pole of the permanent magnet faces the middle pole to form a permanent magnetic circuit of the permanent magnet N pole, the middle pole, the radial rotor core laminations, the side poles and the permanent magnet S pole.

[0010] Preferably, the radial coil windings on the side poles on both sides of the same E-shaped magnetic pole are connected in series and then connected to a two-input and four-output terminal together with the radial coil windings wound on the middle pole. The two-input and four-output terminal is connected to a power amplifier to enable the three radial coil windings on the same E-shaped magnetic pole to share one power amplifier.

[0011] Preferably, the side poles and the middle poles are both wound with fault detection coils, and the fault detection coils are electrically connected to the operational amplifier; In order to realize that when the current passes through the radial coil winding under normal conditions, a magnetic field is generated under the action of electromagnetic induction. At this time, when the radial coil winding changes, the generated magnetic flux changes. According to Faraday's law of electromagnetic induction and Oersted's law, the magnetic flux passing through the fault detection coil changes accordingly, and an electromotive force is induced, thereby forming a voltage difference at both ends of the radial coil winding. The voltage difference signal is output to the operational amplifier after being processed by the operational amplifier, and the voltage difference signal amplified by the operational amplifier is used to determine whether the radial coil winding is normal; When a fault occurs in the radial coil winding, a change in the current flowing into the radial coil winding will not cause a change in the voltage difference signal amplified by the operational amplifier, thereby determining that the radial coil winding has a fault.

[0012] Preferably, an inductive radial displacement sensor is further provided on the magnetic suspension rotor main shaft between the radial magnetic bearing assembly and the centrifugal impeller or the cooling impeller, and the radial displacement sensor is electrically connected to the radial coil winding of the radial magnetic bearing assembly via a controller, so as to detect the radial displacement signal of the magnetic suspension rotor main shaft according to the inductive radial displacement sensor, control the current passing through the radial coil winding, and ensure the balance and stability of the magnetic suspension rotor main shaft; A protective bearing is provided between the inductive radial displacement sensor and the centrifugal impeller or the cooling impeller; The centrifugal impeller and the cooling impeller are both provided with splitter blades, and the diameter and height of the centrifugal impeller are respectively larger than the diameter and height of the cooling impeller.

[0013] Preferably, the inductive radial displacement sensor includes a sensor measuring ring mounted on the main shaft of the magnetic levitation rotor and a sensor stator core mounted outside the sensor measuring ring, an air gap is left between the sensor stator core and the sensor measuring ring, and an even number of sensor poles are evenly arranged on the inner side of the sensor stator core, each sensor pole is wound with a sensor coil winding, the relative sensor coil windings are connected in series and have opposite winding directions, one of the two adjacent sensor coil windings is energized and the other is de-energized.

[0014] Preferably, the axial stator core, axial rotor core, radial rotor core laminations, E-shaped magnetic poles, and sensor stator core are all made of silicon steel; the permanent magnet is made of rare earth permanent magnet material; and the sensor measuring ring is made of Permalloy.

[0015] Preferably, a control method for a modular five-degree-of-freedom magnetically suspended compressor rotor system includes axial displacement control and radial displacement control; The axial displacement control steps are as follows: currents of equal magnitude and opposite directions are supplied to the axial coil windings of the two axial magnetic bearing assemblies located on both sides of the drive motor, so that the axial resultant force on the main shaft of the magnetic suspension rotor is zero, and the suspension balance is maintained; when the main shaft of the magnetic suspension rotor drives the axial rotor assembly to undergo axial displacement, the overlap between the axial stator magnetic poles and the axial rotor magnetic poles changes, and at this time, the current supplied to the axial coil winding on the side with increased overlap is reduced, and the current supplied to the axial coil winding on the side with reduced overlap is increased, so as to generate a reverse axial electromagnetic force until the main shaft of the magnetic suspension rotor regains balance; The radial displacement control includes a variable bias current control strategy based on the speed and a redundant control strategy under a fault state, wherein the variable bias current control strategy based on the speed is as follows: when the speed of the magnetic suspension rotor main shaft is 0 or the speed is lower than the set first threshold, the permanent magnetic force provided by the permanent magnet is used to suspend the magnetic suspension rotor main shaft; when the magnetic suspension rotor main shaft rotates at the second threshold, a first bias current is introduced into the radial coil winding to generate an electromagnetic magnetic circuit, at which time the electromagnetic magnetic circuit is superimposed on the permanent magnetic magnetic circuit generated by the permanent magnet, thereby enhancing the radial stiffness and suspending the magnetic suspension rotor main shaft; when the magnetic suspension rotor main shaft rotates at the third threshold, a second bias current is introduced into the radial coil winding to increase the radial stiffness and suspend the magnetic suspension rotor main shaft; wherein the third threshold, the second threshold, and the first threshold are successively reduced, and the second bias current is greater than the first bias current; The redundant control strategy is as follows: when a fault occurs in the radial coil winding on the side pole, the current of the radial coil winding on the middle pole is increased to compensate for the electromagnetic flux, thereby keeping the radial displacement stiffness in the direction of the E-shaped magnetic pole unchanged; when a fault occurs in the radial coil winding on the middle pole, the current of the radial coil winding on the two side poles is increased to compensate for the electromagnetic flux, thereby keeping the radial displacement stiffness in the direction of the E-shaped magnetic pole unchanged.

[0016] Therefore, the present invention adopts the above modular five-degree-of-freedom magnetic suspension compressor rotor system and control method, which has the following beneficial effects: 1. The use of an axial magnetic bearing assembly without a thrust plate simplifies the assembly process of the axial magnetic bearing, reduces the loss during the operation of the equipment, and is conducive to improving the rotor's limit speed; at the same time, the axial magnetic bearing assembly also additionally improves the radial stiffness of the rotor system and improves the system stability; that is, the reliability of the radial magnetic bearing is improved and the energy consumption and manufacturing cost of the radial magnetic bearing assembly are reduced; 2. The radial magnetic bearing assembly adopts a modular design. When the magnetic bearing system fails, it can be quickly disassembled, which is convenient for quickly and accurately locating the problem and repairing it; 3. A permanent magnet is introduced into one of the poles of the radial magnetic bearing assembly, which reduces the current demand in the electromagnetic coil and only requires four power amplifiers to achieve analytical redundancy, making it easier to quickly and accurately locate the problem and repair it.

[0017] The technical solution of the present invention is further described in detail below through the accompanying drawings and embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 A side view of a modular five-degree-of-freedom magnetic suspension compressor rotor system according to the present invention; Figure 2 A cross-sectional view of a modular five-degree-of-freedom magnetic suspension compressor rotor system according to the present invention; Figure 3 It is a structural schematic diagram of an axial magnetic bearing assembly of a modular five-degree-of-freedom magnetic suspension compressor rotor system according to the present invention; Figure 4 This is a Maxwell simulated magnetic flux distribution diagram of the axial magnetic bearing assembly of a modular five-degree-of-freedom magnetic suspension compressor rotor system described in the present invention; Figure 5 An exploded view of a radial magnetic bearing assembly of a modular five-degree-of-freedom magnetic suspension compressor rotor system according to the present invention; Figure 6 A magnetic circuit diagram of a radial magnetic bearing assembly of a modular five-degree-of-freedom magnetic suspension compressor rotor system according to the present invention; Figure 7 This is a Maxwell simulated magnetic flux distribution diagram of a radial magnetic bearing assembly of a modular five-degree-of-freedom magnetic suspension compressor rotor system described in the present invention; Figure 8 A schematic diagram of radial coil winding connection of a modular five-degree-of-freedom magnetic suspension compressor rotor system according to the present invention; Fig. 9 A schematic diagram of the circuit connection between a fault detection coil and an operational amplifier of a modular five-degree-of-freedom magnetic suspension compressor rotor system according to the present invention; Fig.10 This is a schematic structural diagram of an inductive radial displacement sensor for a modular five-degree-of-freedom magnetically suspended compressor rotor system according to the present invention.

[0019] Reference numerals 1. Magnetic suspension rotor main shaft; 11. Shaft section; 2. Drive motor; 21. Motor stator; 22. Motor rotor core; 3. Axial magnetic bearing assembly; 31. Axial stator core; 32. Axial coil winding; 33. Axial rotor core; 34. Stator pole; 35. Rotor pole; 4. Radial magnetic bearing assembly; 41. Cage; 42. E-shaped pole; 43. Permanent magnet; 44. Radial coil winding; 45. Radial rotor core lamination; 46. Two-input and four-output terminal; 47. Power amplifier amplifier; 48. fault detection coil; 49. operational amplifier; 410. permanent magnetic circuit; 411. electromagnetic magnetic circuit; 412. mounting groove; 413. mounting hole; 414. middle pole; 415. side pole; 415. magnetic pole groove; 5. inductive radial displacement sensor; 51. sensor stator core; 502. sensor coil winding; 53. sensor measuring ring; 54. sensor magnetic pole; 6. protective bearing; 7. cooling impeller; 8. centrifugal impeller; 9. sleeve; 10. air gap. DETAILED DESCRIPTION

[0020] In order to make the purpose, technical scheme and advantages disclosed in the embodiments of the present invention clearer, the embodiments of the present invention are further described in detail in combination with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the embodiments of the present invention and are not used to limit the embodiments of the present invention. Based on the embodiments in the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of this application. Examples of the embodiments are shown in the accompanying drawings, where the same or similar reference numerals throughout represent the same or similar elements or elements with the same or similar functions.

[0021] It should be noted that the terms "including" and "having" and any variations thereof are intended to cover non-exclusive inclusions. For example, a process, method, system, product or server that includes a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units that are not explicitly listed or inherent to these processes, methods, products or devices.

[0022] The embodiments of the present invention are described in detail below in conjunction with the accompanying drawings.

[0023] like Figure 1-Figure 10As shown, a modular five-degree-of-freedom magnetic levitation compressor rotor system includes a magnetic levitation rotor main shaft 1 and a drive motor 2 arranged in the middle of the magnetic levitation rotor main shaft 1. In this embodiment, the motor rotor core 22 of the drive motor 2 is fixed to the middle of the magnetic levitation rotor main shaft 1 through the shaft section 11, and the motor stator 21 is sleeved on the outside of the motor rotor core 22. The two ends of the magnetic levitation rotor main shaft 1 are respectively installed with a centrifugal impeller 8 and a cooling impeller 7. The magnetic levitation rotor main shaft 1 between the drive motor 2 and the centrifugal impeller 8 and the magnetic levitation rotor main shaft 1 between the drive motor 2 and the cooling impeller 7 are sequentially provided with an axial magnetic bearing assembly 3 and a radial magnetic bearing assembly 4. The axial magnetic bearing assembly 3 is a thrust disk-free structure with direct magnetic field coupling; the radial magnetic bearing assembly 4 is a modular structure with block-type magnetic poles, and the remaining two adjacent components on the magnetic levitation rotor main shaft 1 are positioned by a sleeve 9.

[0024] Specifically, the axial magnetic bearing assembly 3 includes an axial rotor assembly sleeved on the outside of the magnetic suspension rotor main shaft 1 and an axial stator assembly sleeved on the outside of the axial rotor assembly, and an air gap 10 is left between the axial rotor assembly and the axial stator assembly; the axial stator assembly includes an axial stator core 31 and an axial coil winding 32, and the axial coil winding 32 is wound between two axial stator poles 34 on the axial stator core 31; the axial rotor assembly includes an axial rotor core 33 and an axial rotor pole 35 integrally formed with the axial rotor core 33; the axial stator pole 34 overlaps with the axial rotor pole 35 in the axial part, and the overlapping width is 1 / 5 of the width of the axial rotor pole 35 or the axial stator pole 34, and the overlapping directions of the two axial magnetic bearing assemblies 3 located on both sides of the drive motor 2 are opposite.

[0025] The radial magnetic bearing assembly 4 includes a retaining frame 41 at both ends and a modular radial magnetic pole assembly, a radial coil winding 44 and a radial rotor core lamination 45 arranged in a mounting cavity surrounded by the retaining frames 41 at both ends from outside to inside, wherein the modular radial magnetic pole assembly includes a plurality of E-shaped magnetic poles 42 uniformly arranged in a circular array on the inner wall of one of the retaining frames 41, and an intermediate pole 414 is arranged at the middle position of the inner arc side of each E-shaped magnetic pole 42, and the two sides of the intermediate pole 414 are symmetrically arranged There is a side pole 415, the width of the middle pole 414 is twice the width of the side pole 415, the number of turns of the radial coil winding wound on the middle pole is twice the number of turns of the radial coil winding wound on the side pole, and radial coil windings 44 are wound on both the middle pole 414 and the side pole 415; after the radial coil winding 44 is energized, an SNS magnetic pole is formed to form an electromagnetic circuit from the middle pole 414, the radial rotor core laminations 45, the side pole 415 to the return middle pole 414.

[0026] In this embodiment, four E-shaped magnetic poles 42 are provided, and the E-shaped magnetic poles 42 are clamped on the inner wall of one of the retaining frames 41 through the mounting groove 412, and the end surface of the other retaining frame 41 is provided with a mounting hole 413 for maintaining a stable connection between the two retaining frames 41.

[0027] Two magnetic pole grooves 415 are provided on the outer arc side of one of the E-shaped magnetic poles 42, and the two magnetic pole grooves 415 are respectively located between the two side poles 415 and the middle pole 414, and a permanent magnet 43 is arranged in the magnetic pole groove 415, and the N pole of the permanent magnet 43 faces the middle pole 414 to form a permanent magnetic circuit 410 of the permanent magnet 43 N pole, the middle pole 414, the radial rotor core laminations 45, the side poles 415 and the permanent magnet 43 S pole.

[0028] The radial coil windings 44 on the side poles 415 on both sides of the same E-shaped magnetic pole 42 are connected in series and then connected to a two-input and four-output terminal 46 together with the radial coil windings 44 wound on the middle pole 414. The two-input and four-output terminal 46 is connected to a power amplifier 47 to enable the three radial coil windings 44 on the same E-shaped magnetic pole 42 to share one power amplifier 47.

[0029] A fault detection coil 48 is wound around both the side pole 415 and the middle pole 414, and the fault detection coil 48 is electrically connected to the operational amplifier 49; so that when current passes through the radial coil winding 44 under normal conditions, a magnetic field is generated under the action of electromagnetic induction. At this time, when the radial coil winding 44 changes, the generated magnetic flux changes. According to Faraday's law of electromagnetic induction and Oersted's law, the magnetic flux passing through the fault detection coil 48 changes accordingly, and an electromotive force is induced, thereby forming a voltage difference across the radial coil winding 44. The voltage difference signal is output to the operational amplifier 49 after being processed by the operational amplifier 49, and the voltage difference signal amplified by the operational amplifier 49 is used to determine that the radial coil winding 44 is normal; when the radial coil winding 44 fails, the change in the current passing through the radial coil winding 44 will not cause the voltage difference signal amplified by the operational amplifier 49 to change, thereby determining that the radial coil winding 44 has a fault.

[0030] An inductive radial displacement sensor 5 is also provided on the magnetic suspension rotor main shaft 1 between the radial magnetic bearing assembly 4 and the centrifugal impeller 8 or the cooling impeller 7. The radial displacement sensor is electrically connected to the radial coil winding 44 of the radial magnetic bearing assembly 4 through a controller, so as to detect the radial displacement signal of the magnetic suspension rotor main shaft 1 according to the inductive radial displacement sensor 5, control the current to pass through the radial coil winding 44, and ensure the balance and stability of the magnetic suspension rotor main shaft 1; a protective bearing 6 is provided between the inductive radial displacement sensor 5 and the centrifugal impeller 8 or the cooling impeller 7; the centrifugal impeller 8 and the cooling impeller 7 are both provided with splitter blades, and the diameter and height of the centrifugal impeller 8 are respectively greater than the diameter and height of the cooling impeller 7.

[0031] The inductive radial displacement sensor 5 includes a sensor measuring ring 53 sleeved on the magnetic suspension rotor main shaft 1 and a sensor stator core 51 sleeved outside the sensor measuring ring 53. An air gap 10 is left between the sensor stator core 51 and the sensor measuring ring 53, and an even number of sensor magnetic poles 54 are evenly arranged on the inner side of the sensor stator core 51. A sensor coil winding 502 is wound around each sensor magnetic pole 54. The relative sensor coil windings 502 are connected in series and have opposite winding directions. One of the two adjacent sensor coil windings 502 is energized and the other is de-energized.

[0032] The axial stator core 31, the axial rotor core 33, the radial rotor core laminations 45, the E-shaped magnetic poles 42, and the sensor stator core 51 are all made of silicon steel; the permanent magnet 43 is made of rare earth permanent magnet material; and the sensor measuring ring 53 is made of Permalloy.

[0033] A control method for a modular five-degree-of-freedom magnetically suspended compressor rotor system, including axial displacement control and radial displacement control; The axial displacement control steps are as follows: currents of equal magnitude and opposite directions are supplied to the axial coil windings 32 of the two axial magnetic bearing assemblies 3 located on both sides of the drive motor 2, so that the axial resultant force on the magnetic suspension rotor main shaft 1 is zero, and the suspension balance is maintained; when the magnetic suspension rotor main shaft 1 drives the axial rotor assembly to undergo axial displacement, the overlap between the axial stator magnetic poles 34 and the axial rotor magnetic poles 35 changes, and at this time, the current supplied to the axial coil windings 32 on the side with increased overlap is reduced, and the current supplied to the axial coil windings 32 on the side with reduced overlap is increased, so as to generate a reverse axial electromagnetic force until the magnetic suspension rotor main shaft 1 regains balance; The radial displacement control includes a variable bias current control strategy based on the speed and a redundant control strategy under a fault state, wherein the variable bias current control strategy based on the speed is as follows: when the speed of the magnetic suspension rotor main shaft 1 is 0 or the speed is lower than the set first threshold, the permanent magnetic force provided by the permanent magnet 43 is used to suspend the magnetic suspension rotor main shaft 1; when the magnetic suspension rotor main shaft 1 rotates at the second threshold, a first bias current is introduced into the radial coil winding 44 to generate an electromagnetic magnetic circuit 411, at which time the electromagnetic magnetic circuit 411 is superimposed on the permanent magnetic magnetic circuit 410 generated by the permanent magnet, thereby enhancing the radial stiffness and suspending the magnetic suspension rotor main shaft 1; when the magnetic suspension rotor main shaft 1 rotates at the third threshold, a second bias current is introduced into the radial coil winding 44 to increase the radial stiffness and suspend the magnetic suspension rotor main shaft 1; wherein the third threshold, the second threshold, and the first threshold are successively reduced, and the second bias current is greater than the first bias current; It should be noted that the first threshold, the second threshold, the third threshold, the first bias current and the second bias current set above all need to be determined according to the size of the device. In this embodiment, the first threshold is 1 / 3 of the rotor's limit speed, the second threshold is 2 / 3 of the rotor's limit speed, and the third threshold is the rotor's limit speed; the first bias current is 1 / 4 of the maximum coil current, and the second bias current is 1 / 2 of the maximum coil current.

[0034] In the present embodiment, when the middle pole 414 and the side pole 415 fail at the same time, the retaining frame 41 at one end can be opened, and the faulty E-shaped magnetic pole 42 can be removed and replaced. Since the entire radial magnetic bearing assembly 4 adopts a modular design, the entire radial magnetic bearing assembly 4 does not need to be completely disassembled during the replacement process, and quick disassembly and assembly can be achieved, thereby improving maintenance efficiency and thus improving the reliability of the radial magnetic bearing assembly 4.

[0035] The redundant control strategy is as follows: when the radial coil winding 44 on the side pole 415 fails, the current of the radial coil winding 44 on the middle pole 414 is increased to compensate for the electromagnetic flux (under the experimental environment, the current in the radial coil winding 44 on the middle pole 414 is increased to twice the original value; under the actual environment, it is adjusted according to the rotor vibration amplitude detected by the displacement sensor, that is, the current is increased until the difference between the rotor vibration and the vibration amplitude before the coil failure is less than the set value), thereby maintaining the radial displacement stiffness in the direction of the E-shaped magnetic pole 42 unchanged; when the radial coil winding 44 on the middle pole 414 fails, the current of the radial coil winding 44 on the two side poles 415 is increased to compensate for the electromagnetic flux, thereby maintaining the radial displacement stiffness in the direction of the E-shaped magnetic pole 42 unchanged.

[0036] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that they can still modify or replace the technical solution of the present invention with equivalents, and these modifications or equivalent replacements cannot cause the modified technical solution to deviate from the spirit and scope of the technical solution of the present invention.

Claims

1. A modular five-degree-of-freedom magnetic suspension compressor rotor system, comprising a magnetic suspension rotor main shaft and a drive motor arranged in the middle of the magnetic suspension rotor main shaft, a centrifugal impeller and a cooling impeller are respectively installed at both ends of the magnetic suspension rotor main shaft, an axial magnetic bearing assembly and a radial magnetic bearing assembly are sequentially arranged on the magnetic suspension rotor main shaft between the drive motor and the centrifugal impeller and on the magnetic suspension rotor main shaft between the drive motor and the cooling impeller, characterized in that: The axial magnetic bearing assembly is a thrust-disk-free structure with direct magnetic field coupling; the radial magnetic bearing assembly is a modular structure with segmented magnetic poles.

2. A modular five-degree-of-freedom magnetically suspended compressor rotor system according to claim 1, characterized in that: The axial magnetic bearing assembly comprises an axial rotor assembly sleeved on the outside of the magnetic suspension rotor main shaft and an axial stator assembly sleeved on the outside of the axial rotor assembly, with an air gap between the axial rotor assembly and the axial stator assembly; The axial stator assembly comprises an axial stator core and an axial coil winding, wherein the axial coil winding is wound between two axial stator magnetic poles on the axial stator core; The axial rotor assembly includes an axial rotor core and an axial rotor magnetic pole integrally formed with the surface of the axial rotor core; The axial stator poles overlap with the axial rotor poles in the axial part, and the overlapping width is 1 / 5 of the width of the axial rotor poles or the axial stator poles, and the overlapping directions of the two axial magnetic bearing assemblies located on both sides of the drive motor are opposite.

3. A modular five-degree-of-freedom magnetically suspended compressor rotor system according to claim 2, characterized in that: The radial magnetic bearing assembly comprises retaining frames at both ends and a modular radial magnetic pole assembly, a radial coil winding and a radial rotor core lamination arranged in an installation cavity surrounded by the retaining frames at both ends from outside to inside, wherein the modular radial magnetic pole assembly comprises a plurality of E-shaped magnetic poles uniformly arranged in a circumferential array on the inner wall of one of the retaining frames, an intermediate pole is arranged at the middle position of the inner arc side of each E-shaped magnetic pole, side poles are axially symmetrically arranged on both sides of the intermediate pole, the width of the intermediate pole is twice the width of the side pole, and radial coil windings are wound on both the intermediate pole and the side pole, and the number of turns of the radial coil winding wound on the intermediate pole is twice the number of turns of the radial coil winding wound on the side pole; After the radial coil winding is energized, an SNS magnetic pole is formed to form an electromagnetic circuit from the middle pole, the radial rotor core laminations, the side poles to the return middle pole.

4. A modular five-degree-of-freedom magnetically suspended compressor rotor system according to claim 3, characterized in that: Two magnetic pole grooves are provided on the outer arc side of one of the E-shaped magnetic poles, and the two magnetic pole grooves are respectively located between the two side poles and the middle pole, and permanent magnets are arranged in the magnetic pole grooves, with the N pole of the permanent magnet facing the middle pole to form a permanent magnetic circuit of the permanent magnet N pole, the middle pole, the radial rotor core laminations, the side poles and the permanent magnet S pole.

5. A modular five-degree-of-freedom magnetically suspended compressor rotor system according to claim 4, characterized in that: The radial coil windings on the side poles on both sides of the same E-shaped magnetic pole are connected in series and then connected to the two-input and four-output terminal together with the radial coil winding wound on the middle pole. The two-input and four-output terminal is connected to the power amplifier to achieve the sharing of one power amplifier by the three radial coil windings on the same E-shaped magnetic pole.

6. A modular five-degree-of-freedom magnetically suspended compressor rotor system according to claim 5, characterized in that: The side poles and the middle poles are both wound with fault detection coils, which are electrically connected to the operational amplifier; In order to realize that when the current passes through the radial coil winding under normal conditions, a magnetic field is generated under the action of electromagnetic induction. At this time, when the radial coil winding changes, the magnetic flux generated changes. According to Faraday's law of electromagnetic induction and Oersted's law, the magnetic flux passing through the fault detection coil changes accordingly, and an electromotive force is induced, thereby forming a voltage difference at both ends of the radial coil winding. The voltage difference signal is processed by the operational amplifier and then output to the operational amplifier. The voltage difference signal amplified by the operational amplifier is used to determine whether the radial coil winding is normal. When a fault occurs in the radial coil winding, a change in the current flowing into the radial coil winding will not cause a change in the voltage difference signal amplified by the operational amplifier, thereby determining that the radial coil winding has a fault.

7. A modular five-degree-of-freedom magnetically suspended compressor rotor system according to claim 6, characterized in that: An inductive radial displacement sensor is also provided on the magnetic suspension rotor main shaft between the radial magnetic bearing assembly and the centrifugal impeller or the cooling impeller. The radial displacement sensor is electrically connected to the radial coil winding of the radial magnetic bearing assembly via a controller, so as to detect the radial displacement signal of the magnetic suspension rotor main shaft according to the inductive radial displacement sensor, control the current passing through the radial coil winding, and ensure the balance and stability of the magnetic suspension rotor main shaft; A protective bearing is provided between the inductive radial displacement sensor and the centrifugal impeller or the cooling impeller; The centrifugal impeller and the cooling impeller are both provided with splitter blades, and the diameter and height of the centrifugal impeller are respectively larger than the diameter and height of the cooling impeller.

8. A modular five-degree-of-freedom magnetically suspended compressor rotor system according to claim 7, characterized in that: The inductive radial displacement sensor includes a sensor measuring ring sleeved on the main shaft of the magnetic suspension rotor and a sensor stator core sleeved outside the sensor measuring ring. An air gap is left between the sensor stator core and the sensor measuring ring, and an even number of sensor magnetic poles are evenly arranged on the inner side of the sensor stator core. A sensor coil winding is wound around each sensor magnetic pole. The relative sensor coil windings are connected in series and have opposite winding directions. One of the two adjacent sensor coil windings is energized and the other is de-energized.

9. A modular five-degree-of-freedom magnetically suspended compressor rotor system according to claim 8, characterized in that: The axial stator core, axial rotor core, radial rotor core laminations, E-shaped magnetic poles, and sensor stator core are all made of silicon steel; the permanent magnet is made of rare earth permanent magnet material; and the sensor measuring ring is made of Permalloy.

10. A control method for a modular five-degree-of-freedom magnetically suspended compressor rotor system according to claim 8 or 9, characterized in that: Including axial displacement control and radial displacement control; The axial displacement control steps are as follows: currents of equal magnitude and opposite directions are supplied to the axial coil windings of the two axial magnetic bearing assemblies located on both sides of the drive motor, so that the axial resultant force on the main shaft of the magnetic suspension rotor is zero, and the suspension balance is maintained; when the main shaft of the magnetic suspension rotor drives the axial rotor assembly to undergo axial displacement, the overlap between the axial stator magnetic poles and the axial rotor magnetic poles changes, and at this time, the current supplied to the axial coil winding on the side with increased overlap is reduced, and the current supplied to the axial coil winding on the side with reduced overlap is increased, so as to generate a reverse axial electromagnetic force until the main shaft of the magnetic suspension rotor regains balance; The radial displacement control includes a variable bias current control strategy based on the speed and a redundant control strategy under a fault state, wherein the variable bias current control strategy based on the speed is as follows: when the speed of the magnetic suspension rotor main shaft is 0 or the speed is lower than the set first threshold, the permanent magnetic force provided by the permanent magnet is used to suspend the magnetic suspension rotor main shaft; when the magnetic suspension rotor main shaft rotates at the second threshold, a first bias current is introduced into the radial coil winding to generate an electromagnetic magnetic circuit, at which time the electromagnetic magnetic circuit is superimposed on the permanent magnetic magnetic circuit generated by the permanent magnet, thereby enhancing the radial stiffness and suspending the magnetic suspension rotor main shaft; when the magnetic suspension rotor main shaft rotates at the third threshold, a second bias current is introduced into the radial coil winding to increase the radial stiffness and suspend the magnetic suspension rotor main shaft; wherein the third threshold, the second threshold, and the first threshold are successively reduced, and the second bias current is greater than the first bias current; The redundant control strategy is as follows: when the radial coil winding on the side pole fails, the current of the radial coil winding on the middle pole is increased to compensate the electromagnetic flux, thereby keeping the radial displacement stiffness in the direction of the E-shaped magnetic pole unchanged; When a fault occurs in the radial coil winding on the middle pole, the current of the radial coil winding on the two side poles is increased to compensate for the electromagnetic flux, thereby keeping the radial displacement stiffness in the direction of the E-shaped magnetic pole unchanged.

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