JP2022536225A - Unlubricated centrifugal compressor - Google Patents

Abstract

A compact gas compressor comprising a) one or more centrifugal compressors and b) a high speed axial flow permanent magnet synchronous electric motor. The electric motor and the compressor are directly coupled on a single axis, supported by passive magnetic and electrodynamic bearings, and are not lubricated. The device does not use mechanical seals because the rotor is located inside a gas pressure vessel. The device does not require auxiliary systems for cooling, filtering, separating or supplying the lubricating fluid. [Selection drawing] Fig. 1

Description

CROSS-REFERENCE TO RELATED APPLICATIONS This application claims priority to U.S. Provisional Application No. 62/769,323, filed November 19, 2018, which is fully incorporated herein by reference. incorporated herein by reference.

The present invention relates to the field of gas compression devices. In particular, the present invention refers to small electrical devices or appliances that use centrifugal compressors to increase gas pressure.

Gas compression by mechanical means is currently practiced by a variety of techniques that have been widely used and tested for several years. Centrifugal, axial, reciprocating and screw compressors are among the most used methods.

A reciprocating or piston compressor is similar in construction to an internal combustion engine. The piston or plunger alternately displaces longitudinally within a cylinder in which a series of seals are arranged. A set of valves allows the inflow of gas during the expansion stage of the chamber formed by the cylinder and plunger, and the plunger returns. As the plunger advances again, it reduces the volume of the chamber in which the gas is located, thus providing the desired subsequent pressure increase. Finally, another set of valves allows the high pressure gas to escape. These compressors are widely used in small and medium-sized applications. They are of simple construction and their efficiency is relatively high. Although they have many moving parts, they move slowly relative to each other, so conventional lubricants can be used in their seals and bearings. By operating at low speeds (approximately 1,000-5,000 rpm), they are usually connected directly to electric motors or combustion engines without gear assemblies.

The main drawback of this technology is the intensive maintenance required by the lubrication system necessary to ensure the tightness between the plunger and cylinder, the integrity and watertightness of the valve, and to avoid damage to the bearings. . With proper maintenance, reciprocating compressors can serve for many years without problems. However, even when maintained at optimum lubrication conditions, all of the above mentioned parts are subject to mechanical wear and must be replaced periodically. Due to the number of mechanisms involved, reciprocating compressors are the bulkiest (and have the lowest specific power) of the four types described.

Screw compressors, like reciprocating ones, belong to a group of machines called "positive displacement machines". That is, changes in gas pressure are accomplished by changes in the volume of the chamber containing it. In a screw compressor, two screw-shaped helical shafts arranged parallel to each other rotate unitarily with respect to each other. Both helices are in chambers with walls very close to their thread edges, thus forming a mechanical seal with or without lubrication. Rotation of the screw relative to the chamber generates a hermetically isolated, gas-laden volume that progressively decreases in size while displacing from the intake port to the exhaust port.

This type of compressor is typically used in medium-sized applications and offers several advantages such as small size and high compression ratio. Mechanical parts rotate at moderate speeds (e.g., 3,000-10,000 rpm), so they typically require gear assemblies for coupling to low speed electric motors or combustion engines. Sometimes. Conversely, they have fewer moving parts than reciprocating compressors. Mechanical wear is therefore less important with respect to maintenance. The main drawback lies in the lubrication system requirement that it should be kept free of solid particles and cooled at all times. Lubricants play an important role by acting as seals between helices and as a means of transmitting torque between helices without mechanical friction. Additionally, the lubricant in the compression chamber needs to be mixed with the compressed gas (especially if they are both similar fluids such as hydrocarbons), separated and reused within a particular set of equipment. be. For these reasons, the miniaturization of screw compressors is offset by the numerous auxiliary systems that accompany them.

Centrifugal compressors belong to the group of turbomachinery together with axial compressors, turbines and centrifugal pumps. In a centrifugal compressor, increasing the gas pressure is achieved indirectly by first accelerating the gas velocity and then converting this kinetic energy into potential energy. A bladed disk, called an impeller, receives the gas at low pressure and rotationally accelerates the gas while displacing it to the surroundings. As the high velocity gases exit the rotor, another stationary component called a diffuser is responsible for gradually slowing the gases and increasing their pressure.

Centrifugal compressors exhibit several important advantages over positive displacement technology: first, their size is much smaller than reciprocating or screw compressors for the same application (flow rate and pressure). (Centrifugal compressors have a high specific power). Second, they do not use seals to create a waterproof chamber, so internal parts such as impellers are not subject to mechanical wear. The function of lubricants used in these compressors is to reduce friction in auxiliary components such as external seals and/or bearings.

A problem faced by these compressors is related to the high speeds at which their impellers must rotate (typically between 20,000 and 100,000 rpm). Therefore, it is necessary to use a gear assembly to double the speed of a drive source such as an electric motor or combustion engine. Gear assemblies are critical components because of both the mechanical wear and energy loss associated with them. Another problem is found in the seals that keep the process gas isolated from the atmosphere. The seal provides communication between the rotor shaft and the gear assembly, thus maintaining high gas pressure inside the compressor body and low pressure outside. Seals are critical parts with respect to wear and lubrication plays an important role.

The above complications limit the use of centrifugal compressors to large scale applications. However, in recent years, with the realization of technologies such as high-speed electric engines, centrifugal compressors suitable for small and medium-sized applications have been developed. For example, the company Aerzen® offers an air compressor in which a radial flow electric motor is mounted on the same shaft as the rotor of the compressor. In this manner, the need for a gear assembly and its attendant operational difficulties are eliminated.

A major drawback found in the use of high speed radial flow motors is the large amount of ferromagnetic material present in the stator. High electrical frequencies used at high speeds mean huge energy losses in the core as parasitic currents and magnetic hysteresis. An alternative to this technology is that of axial electric motors, which have gained great interest in recent years due to a series of advantageous design features.

First, the geometry of the axial flow motor allows obtaining a machine with a higher specific power than the radial flow motor. That is, in order to obtain the same output, the motor may be smaller in size than the radial flow motor, resulting in weight reduction and cost reduction. Also, like radial motors, axial motors may be of the induction type, using wire-wound conductors equivalent to a "squirrel cage", or synchronous, using permanent magnets. . The latter exhibits the highest power density of all possible configurations.

Second, and more relevant for the application of the present invention, the placement of coils in axial motors requires the use of ferromagnetic materials in the core much less than in radial motors. . In high electrical frequency applications (high spinning speeds), reduced ferromagnetic material means reduced energy losses due to magnetic hysteresis and parasitic currents, thus significantly improving machine performance and reducing cooling requirements. The industrial use of axial synchronous electric motors in high speed applications, which is not well known in current technology, promises important improvements in terms of size reduction and energy efficiency.

The company ICR Turbine Corporation (U.S. Patent Publication No. US20140306460) uses several compression stages and A compact Brayton cycle was developed to implement the expansion stage. Each of the compression and expansion stages includes a radial compressor and a radial turbine, both mounted on a single shaft. Behind each radial compressor is a small axial motor that allows the system to start, thus driving the rotor to its minimum holding speed. These engines are of the induction type, with a wound stator and a flat cage rotor.

Additionally, several techniques have been developed to support motor-compressor rotating assemblies without the need to use lubricating oil, thus eliminating other complications associated with the high speeds of these machines. One is known as an "air foil bearing" or simply a "foil bearing" and uses the same process gas as the lubricating fluid. Foil bearings are typically used in air compressors such as those manufactured by Aerzen®.

Another more promising technology is one of magnetic bearings. In this case, the set of rotating bodies is supported by the magnetic field and not hydrodynamically as in the conventional case, thus making the system independent of the process fluid. For example, the company Danfoss® offers a “Turbocor®” compressor for cooling gas, in which the rotor is suspended by an active magnetic bearing (AMB). . Mechanical seals are also not required because the engine compressor assembly is located in a watertight chamber containing the process gases. Another example of this technology is SIEMENS® (Spanish Patent No. 2309173), a company that has developed a large centrifugal compressor in which the engine and compressor are mounted on the same shaft and housed in the same pressure vessel. It is in. In the case of SIEMENS® the bearings are also of the AMB type and the same process gas is used for motor cooling.

The complexity presented by the AMB is that it requires an axial position sensor set and an active control electronic system to externally energize and command the bearings. In the event of an interruption in the energy supply of the control system, the rotating shaft may lose support and come into contact with the fast rotating stator, causing serious and permanent damage.

The present invention includes small size centrifugal compressors for medium and small scale applications that do not use lubrication systems, speed multiplying systems and mechanical seals and typically operate at very high rotational speeds.

This compressor uses, as a drive source, an axial-flow and permanent-magnet electric motor that operates synchronously at high speed and high electrical frequency. The motor operates fast and efficiently because it has fewer ferromagnetic cores in its stator than a comparable radial flow motor. In fact, this motor works efficiently without a ferromagnetic core in the stator. The compressor impeller is directly connected to the motor on a single axis and forms a single moving part of the device. The high efficiency of axial flow motors and the absence of speed increasing gears give the present invention greater reliability and overall energy efficiency than current technology.

The motor-impeller rotating assembly is supported by a combination of magnetic radial bearings and electrodynamic thrust (or axial) bearings so that there is no mechanical contact with the stator. Since the bearing uses permanent passive magnets, it does not require a control system, sensors, or external energy supply. This gives the invention greater operational simplicity and reliability than the current state of the art.

The complete rotor, formed by the motor-impeller assembly and the magnetic and electric bearings, is pressostatically linked to the stator of the compressor and placed inside a waterproof chamber filled with the same process gas. In this way, the use of mechanical seals is avoided along with the frictional wear associated with their use, which gives the present invention the characteristic of requiring less maintenance than other similar state-of-the-art equipment.

By not requiring lubrication for bearings, gears and seals, the apparatus of the present invention does not use auxiliary systems for cooling, filtering, separating and supplying lubricant. This allows the present invention to be simpler and of smaller size than other similar devices of the current state of the art.

FIG. 4 is a side view of an embodiment of the invention showing only the motor-impeller rotating assembly and stator coils of the motor; 1 is a cross-sectional side view of main components of an axial flow motor; FIG. 1 is an exploded perspective view of main components of an axial flow motor; FIG. 1 is a cross-sectional view of an embodiment of the invention including all components of the device; FIG. 1 is an overall perspective view of an embodiment of the device and two two-sided views of the same device, the two-sided views compared to an average adult silhouette for dimensional reference; FIG.

The present invention is a compact device for gas compression driven by an axial synchronous electric motor that does not use any kind of lubricant.

FIG. 1 shows a single moving piece of a motor-impeller rotating assembly (hereinafter rotor). The rotor has a centrifugal impeller 1 responsible for transferring kinetic energy to the process gas. Although only one impeller is shown in the embodiment of FIG. 1, two or more impellers may be used. The impeller is mounted on shaft 5 and fixed thereto. If more than one impeller is used, they may all be mounted and fixed on the same shaft.

The axial synchronous permanent magnet electric motor 2 is formed by a fixed stator portion and a rotating portion. The stator portion of the motor may include coils and various auxiliary components for support, and optionally a portion of the ferromagnetic core. The part may be formed by one or more assemblies arranged between the assemblies of the rotating part. In the embodiment of FIG. 1, two stator assemblies 4 are shown positioned between rotating assemblies 03 . In other embodiments, this may apply to more than two stator assemblies, or only one stator assembly may be used.

2a and 2b show an embodiment of an axial electric motor consisting of a single stator assembly 4. FIG. The assembly includes a coil 10 and different parts of a ferromagnetic core 11 . Said assembly 4 is arranged between two rotating discs 3 containing permanent magnets 12 and may optionally contain another part of a ferromagnetic core 13 . These discs form the rotating part 3 of the axial motor. The rotating part is mounted on a shaft 5 (see FIG. 1) and fixed thereto.

A magnetic flow is established between each of a pair of opposing permanent magnets 12, which are arranged in an attractive force configuration. The magnetic flow passes through the coil through the air in which the motor is immersed or any other means. If the stator assembly includes portions of ferromagnetic cores 11, the magnetic flow is concentrated through these. If the rotor assembly 3 has a ferromagnetic core 13, the magnetic flow between the facing faces of its adjacent magnets is closed therethrough. External electronics monitor the relative position of magnet 12 with respect to coil 10 and activate a series of semiconductors (eg, MOSFETs, IGBTs, SSRs, etc.) that inject current into coil 10 . The moment of the current pulse and the duration of the current pulse are so large that the interaction with the magnetic field induces a force in the permanent magnet, resulting in a torque applied to the shaft 5 (see FIG. 1). The stator portion of motor 04 may include one or more coils 10 that are electrically independent or linked together.

In FIG. 1 it can be seen that the rotating part of the first magnetic radial bearing 6 is formed by one or more permanent magnets having a ring shape and is mounted at or near one end of the shaft 5. . The rotating part of the second magnetic radial bearing 7 is formed by one or more magnets having a ring shape and is mounted at or near the opposite end of the shaft 5 . The rotating part of the radial bearing is part of the rotor. For each bearing, the second stator portion is formed by a permanent magnet having a ring or cylinder shape that circumferentially surrounds the rotating portion and is fixed in a housing (not shown). The magnets are of the same polarity and have a large magnetic field strength, and the magnetic interaction between each rotating part and its mating stator part creates a magnetic repulsion force that radially supports the rotor. to avoid mechanical contact with the rest. In the embodiment of FIG. 1, two magnetic radial bearings are shown, one bearing at each end, but three or more bearings may be used on different shafts 5 to make the rotor support more robust. Can be installed in areas. Radial bearings 6 and 7 are passive and operate without intervening control systems, sensors and external energy sources. Materials for the manufacture of magnetic bearings based on high strength passive magnets such as AlNiCo, SmCo or NdFeB are well known in the art and commercially available.

The concept in mechanics of stiffness refers to the ability of a body to resist deformation or displacement due to external forces. The stiffer the object, the higher the force it produces for the same degree of deformation. This concept, which is usually applied to elastic systems such as springs and bearings, is also frequently used to describe the mechanical properties of active and passive magnetic bearings. An object is said to have negative stiffness if the forces due to the stiffness of the body mentioned above are large and tend to compensate for the deformation or displacement that causes these forces. In the case of magnetic bearings, positive stiffness refers to the particular property that forces due to displacement tend to increase the displacement instead of decreasing it. As this will be used below to explain the functioning of several elements of the invention, it is useful to note the concept of positive stiffness.

The rotor assembly shown in FIG. 1 is supported and stabilized by passive radial bearings to provide negative radial stiffness. That is, when the shaft 5 is displaced laterally (radially), the bearing responds by generating an opposite elastic force that returns the shaft to its centered position. However, as stated in the Earnshaw Theorem, this type of bearing provides a positive stiffness in the axial direction. That is, if the shaft 5 is displaced along its axial direction, the bearings react by generating a force in the same direction, trying to increase the displacement, and thus these bearings force the shaft 5 along its axis. The problem arises that it tends to push axially out of position. Thus, the great advantage of these bearings, due to their completely passive nature, is the drawback of exhibiting a positive axial stiffness, so they cannot be used as the single rotating link of the assembly. To counteract this effect, an additional mechanism should be implemented which works by a different physical principle than the interaction between permanent magnets and which fixes the axial position of shaft 5 . After various tests with different types of axial limiting links, the best results were obtained using electrodynamic thrust bearings.

In FIG. 1 it will be seen that the rotating part of the electrodynamic thrust bearing 8 is formed by two discs with permanent magnets and a ferromagnetic core. The rotating part is mounted on and fixed to the shaft 5 and thus forms part of the rotor. Solid or perforated conductor discs 9 are arranged between the rotating discs and form the stator portion of a thrust bearing connected to a housing (not shown). Relative movement between the magnets of the rotating part and the conductor material of the stator part induces currents in the latter, which generate repulsive forces on the magnets. In the arrangement shown in Figure 1, the repulsive force provides a negative stiffness in the axial direction. Thus, when the shaft 5 is axially displaced, the electrodynamic thrust bearing generates an opposing force tending to reestablish its original position.

Electrodynamic thrust bearings operate in a completely passive manner and do not require auxiliary control systems. However, this function only occurs if there is relative motion between the parts, ie the rotor is rotating. Above a minimum rotational speed, the electrodynamic thrust bearing provides the rotor with sufficient negative axial stiffness to counteract the positive axial stiffness of the magnetic radial bearing. It is possible to arrange the magnet-bearing disk 8 as the rotating part and the conductor disk 9 as the stationary part, or vice versa. Although only one thrust bearing is shown in the embodiment of FIG. 1, two or more can be stacked to provide higher axial stiffness to the rotor. In applications where the rotor is not horizontally oriented, some or all of that axial component of weight may be offset by the same positive stiffness of the magnetic bearing. As such, the electrodynamic thrust bearing must provide only negative stiffness to the assembly and is not used to support its weight.

The combination of electrodynamic thrust bearings and magnetic radial bearings allows the rotor to be fully supported in its axial and radial positions above a certain minimum rotational speed and thus the rest of the machine. avoid mechanical contact. In contrast to active magnetic bearings (AMB), the combination of passive components in the present invention guarantees its function without external energy or control requirements, even if the electrical supply is completely interrupted. This novel combination allows the device to be rotated at the required speed by the impeller of the centrifugal compressor without suffering wear due to the absence of frictional forces that can generate large amounts of thermal and stopping energy.

FIG. 3 shows an embodiment of the invention in which the rotor described above is arranged horizontally and placed inside a body (hereafter stator) forming the stationary structure of the device. The orientation of the rotors can be horizontal, vertical, or any other orientation different from that shown in this embodiment. By means of a flange connection or any other type of connection 15, the low pressure process gas is formed by the main stator wall 16 and other parts sealed against them, such as the high pressure collector 17 or shaft end caps 21. flow into a sealed watertight chamber. The number and arrangement of the parts forming the watertight chamber may differ from that shown in FIG. 3, but they always contain the entire rotor inside and are therefore secured by stationary seals such as gaskets, O-rings, etc. Ensure gas tightness properties.

The area where the axial flow motor 2 is located and is shown in FIG. 3 as a stack of four stator assemblies is the area corresponding to the rotating part and traversed by the low pressure cold gas. This gas flow can remove the heat generated by the motor and acts as a coolant. The gas then enters the first compression stage formed by the impeller 1 and its corresponding diffuser. In the embodiment of FIG. 3, the rotor includes a second impeller 14 traversed by the gas immediately after the first impeller. At each compression stage, the gas increases its pressure and temperature until it enters the high pressure collector 17 and is guided to the discharge connection of the stator. Other embodiments of the invention may include more or fewer impellers and more or fewer assemblies forming an axial flow motor, depending on each particular application.

In the embodiment shown in FIG. 3, the inlet gas temperature is low enough to act as a coolant for the power electronics responsible for commanding the electric motor. A series of power electronics 19 are located outside the gas pressure vessel 16 and are thermally linked thereto. The electronic component takes advantage of the thermal conductivity of metals forming a pressure vessel cooled by the same process gas. Finally, a cap 18 externally covers the power electronics to protect them from dust and ambient moisture. Other embodiments of the present invention may place the electronic component directly inside a pressure vessel flooded with process gas. Other different embodiments may use other conventional and independent methods for cooling the power electronics when the compressor inlet gas temperature is extremely high.

FIG. 4 shows an isometric view of an embodiment of the invention with the rotor oriented horizontally. The figure shows a flanged inlet connection for the gas arranged coaxially with the rotor, which is inside the pressure vessel and not visible. In this embodiment, the high pressure gas discharge is arranged transversely and perpendicularly to said rotor axis. Figure 4 also shows a side view and another front view of the compressor along with an average figure to visualize the typical size of the device. Other embodiments of the present invention can vary in size and proportions and orient the gas inlet and outlet connections in other orientations, for example both coaxial with the rotor axis or both laterally. can do.

The innovative technical features of this device include the following features:
1. An axial synchronous electric motor with permanent magnets is used as the driving force mounted on the same shaft as the impeller of the centrifugal compressor. This type of motor is more efficient and has higher power density than high speed radial flow motors, giving the device superior overall performance and smaller physical size than current technology.
2. It uses passive magnetic bearings and passive electrodynamic bearings that do not require energy supply, auxiliary systems, monitoring and control systems. This property gives the device high operational reliability even in the event of a sudden electrical supply failure. Furthermore, the absence of control assistance systems contributes to its compact size.
3. No mechanical seals are used as the rotor assembly is located entirely inside the same pressure vessel as the process gas. Mechanical seals are subject to frictional wear and require frequent maintenance, especially in high speed applications. Its absence gives the device the characteristic of requiring less maintenance than other prior art devices. Additionally, the lack of mechanical seals contributes to the overall energy efficiency of the device.
4. Seals, gears and bearings do not use any kind of lubricant. This characteristic contributes to the low maintenance requirements of the device as it does not require auxiliary systems for handling the lubricant, such as coolers, filters, separators or pumps, and also contributes to its compactness.
5. Under normal conditions, the novel and contactless rotary support system allows the assembly to rotate at the same speed as the compressor impeller without undergoing mechanical wear.

Claims (19)

A compact gas compression device comprising a motor-impeller rotating assembly formed by one or more centrifugal compressor impellers (1) and an electric motor (2),
said one or more compressor impellers are coupled directly and on a single axis (5) to said electric motor (2);
A compact gas compressor, wherein said electric motor (2) is an axial synchronous permanent magnet motor. The shaft (5) of the motor-impeller rotating assembly includes two or more magnetic radial bearings (6, 7) for fixing the radial position of the shaft (5) and the axial position of the shaft. one or more passive electrodynamic thrust bearings (8, 9) for fixing;
Compact according to claim 1, wherein said magnetic radial bearings (6, 7) and said one or more electrodynamic thrust bearings (8, 9) operate entirely without the use of lubricants and auxiliary control systems. gas compressor. Each of said one or more electric motors (2) is connected to one or more stator assemblies (4) arranged between one or more rotating assemblies (3) fixed to said shaft (5). ), formed by
the stator assembly (4) includes one or more coils (10),
2. Miniature gas compression device according to claim 1, wherein the rotating assembly (3) comprises one or more pairs of permanent magnets (12). 5. Miniature gas compression device according to claim 4, wherein the one or more stator assemblies (4) further comprise a portion of a ferromagnetic core (11). 4. Miniature gas compression device according to claim 3, wherein some of said one or more rotating assemblies (3) have a ferromagnetic core (11). 4. Miniature gas compression device according to claim 3, wherein the one or more coils receive current pulses activated by control electronics (19) that monitor the position of the magnet (12). 4. Miniature gas compression device according to claim 3, wherein the controller (19) comprises semiconductors of the group comprising MOSFETs, IGBTs, SSRs among others. Each of said magnetic radial bearings (6, 7):
a rotating part fixed to said shaft (5) and comprising one or more permanent magnets having a ring shape;
a stator portion circumferentially surrounding the rotating portion and formed by one or more permanent magnets having a ring shape or a cylinder shape;
formed by
3. The miniature gas compression device of claim 2, wherein the two parts are separated by the elastic force of magnetic repulsion. each of said electrodynamic thrust bearings (8, 9):
a rotating part fixed to said shaft (5) and formed by two or more discs (8) containing permanent magnets and a ferromagnetic core;
a stationary part fixed to the housing of said device and arranged between both rotating discs (8) and formed by a solid or perforated conductive disc (9) containing a conductive material;
formed by
3. Miniature gas compression device according to claim 2, wherein the relative movement between the rotating disc (8) and the electrically conductive material induces a current that creates a repelling force on the magnet. each of said electrodynamic thrust bearings comprising:
a stationary part fixed to the housing of the device and formed by two or more discs containing permanent magnets and a ferromagnetic core;
a rotating part fixed to the rotating shaft of the device, the rotating part being positioned between the stationary discs and formed by solid or perforated conductive discs containing conductive material;
formed by
3. The miniature gas compression device of claim 2, wherein relative motion between said stationary disk and said conductive material induces a current that creates a repulsive force against said magnet. Said motor-impeller rotating assembly, said magnetic radial bearings (6, 7) and said electrodynamic thrust bearings (9, 10) are mounted in a completely watertight vessel without mechanical seals under the pressure of process gas (16). 3. Miniature gas compression device according to claim 1 or 2, arranged in a container. 3. Claim 1 or 2, wherein the same process gas is used as coolant for the electric motor (2) and the magnetic radial bearings (6, 7) and the electrodynamic thrust bearings (8, 9). The compact gas compression device according to . 2. Miniature gas compression device according to claim 1, wherein the same said process gas is used as a coolant for said power electronics (19) driving said electric motor. 2. Miniature gas compression apparatus according to claim 1, wherein the apparatus does not include auxiliary systems for cooling, filtering, separating or supplying lubricant of any kind. Miniature gas compression device according to claim 1, wherein said device comprises a compressor impeller (1) and an electric motor (2). Miniature gas compression device according to claim 1, wherein the device comprises two or more compressor impellers (1) and one electric motor (2). The motor-impeller rotating assembly is mounted on a shaft (5) supported by two magnetic radial bearings (6,7) and passive electrodynamic thrust bearings (9,10). 3. The compact gas compression device according to 2. Said motor-impeller rotating assembly is mounted on a shaft (5) supported by two magnetic radial bearings (6,7) and two or more passive electrodynamic thrust bearings (9,10). 3. The compact gas compression device of claim 2, wherein Said motor-impeller rotating assembly is on a shaft (5) supported by three or more magnetic radial bearings (6,7) and two or more passive electrodynamic thrust bearings (9,10). 3. A compact gas compression device according to claim 2, attached.

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