The principle of its operation is based on the use of force acting on a current-carrying conductor placed in a magnetic field. A conductor carrying current can be solid or liquid. In the latter case, the supports are called

magnetohydrodynamic conduction type. Depending on the type of current, conduction suspensions are divided into suspensions direct current And alternating current(magnetic field and current must be in phase).

The conduction suspension shown in Figure 1.2.5 has simple design and at the same time has a high load capacity.

Figure 1.2.5 - Conduction suspension

A significant drawback that limits the use of conduction suspensions is the need to excite currents directly on the suspended body, which leads to a significant increase in its own weight and a decrease in the efficiency of the suspension. Another disadvantage is the need for a large current source.

A small amount of work has been devoted to conduction supports, but wide application they haven't found it yet. On this moment conduction suspension is used in metallurgy (for melting pure metals) and transport.

Active magnetic suspensions

Active magnetic suspension? it's manageable electromagnetic device, which holds the rotating part of the machine (rotor) in a given position relative to the stationary part (stator).

Active magnetic suspensions require a special electronic external feedback unit.

To explain the operating principle of an active magnetic suspension, consider Figure 1.2.6, which shows the simplest structural scheme suspension. It consists of a sensor that measures the displacement of the suspended body relative to the equilibrium position, a regulator that processes the measurement signal, a power amplifier powered by external source, which converts this signal into a control current in the electromagnet winding. This signal causes forces that hold and return the ferromagnetic body to a state of equilibrium.

An obvious advantage of active circuits is the ability to achieve more efficient control of the weighing field and, consequently, improve power characteristics. Active suspension has high load capacity, high mechanical strength, wide range of stiffness and damping, no noise and vibration, impervious to contamination, no wear, no need for lubrication, etc. The stability of the suspension, as well as the necessary rigidity and damping, is achieved by choosing a control law. The disadvantages of an active magnetic suspension include high cost, energy consumption from an external source, complexity of the electronic control unit, etc.

Figure 1.2.6 - Active magnetic suspension

Important areas of application of active magnetic bearings are space technology (vacuum turbomolecular pumps), medical equipment, technology in Food Industry, high-speed ground transportation, etc.

after watching videos of certain comrades, like these

I decided and I will check in on this topic. In my opinion, the video is quite illiterate, so it’s quite possible to whistle from the stalls.

After going through a bunch of diagrams in my head, looking at the principle of suspension in the central part in Beletsky’s video, understanding how the Levitnon toy works, I came up with a simple diagram. It is clear that there should be two supporting spikes on one axis, the spike itself is made of steel, and the rings are rigidly fixed on the axis. Instead of solid rings, it is quite possible to place not very large magnets in the shape of a prism or cylinder located around the circumference. The principle is the same as in the famous toy "Livitron". only instead of a geroscopic moment that prevents the top from tipping over, we use a “thrust” between supports rigidly fixed to the axis.

Below is a video with the toy "Livitron"

and here is the diagram that I propose. in fact, this is the toy in the video above, but as I already said, it needs something that would prevent the support spike from tipping over. In the video above, the gyroscopic moment is used, I use two stands and a spacer between them.

Let's try to justify the work of this design, as I see it:

the magnets are pushed away, which means there is a weak point - you need to stabilize these spikes along the axis. here I used the following idea: the magnet tries to push the spike into the area with the lowest field strength, because the spike has a magnetization opposite to the ring and the magnet itself is ring-shaped, where in sufficient large area located along the axis, the tension is less than at the periphery. those. tension distribution magnetic field The shape resembles a glass - the tension is maximum in the wall, and minimum on the axis.

the spike must be stabilized along the axis, while simultaneously being pushed out of the ring magnet into the area with the lowest field strength. those. if there are two such spikes on one axis and the ring magnets are rigidly fixed, the axis should “freeze”.

it turns out that being in a zone with lower field strength is the most energetically favorable.

Having rummaged around on the Internet I found a similar design:

here, too, a zone with lower tension is formed, it is also located along the axis between the magnets, and the angle is also used. In general, the ideology is very similar, but if we talk about a compact bearing, the option above looks better, but requires specially shaped magnets. those. The difference between the schemes is that I squeeze the supporting part into a zone with less tension, and in the scheme above, the very formation of such a zone ensures the position on the axis.
To make the comparison clearer, I redrawn my diagram:

they are essentially mirror images. In general, the idea is not new - they all revolve around the same thing, I even have suspicions that the author of the video above simply did not look for the proposed solutions

here it’s almost one to one, if the conical stops are made not solid, but composite - magnetic core + ring magnet, then you’ll get my circuit. I would even say the initial unoptimized idea - the picture below. only the picture above works to “attract” the rotor, but I initially planned “repulsion”


For those who are especially gifted, I want to note that this suspension does not violate Earnshaw’s theorem (prohibition). The fact is that we're talking about This is not about a purely magnetic suspension, without rigidly fixing the centers on the axis, i.e. one axis is rigidly fixed, nothing will work. those. It's about choosing a fulcrum and nothing more.

in fact, if you watch Beletsky’s video, you can see that approximately the same configuration of fields is already used in some places, only the final touch is missing. the conical magnetic circuit distributes the “repulsion” along two axes, but Earnshaw ordered the third axis to be fixed differently, I did not argue and fixed it rigidly mechanically. I don’t know why Beletsky didn’t try this option. in fact, he needs two “livitrons” - the stands are fixed on the axis, and connected to the tops with a copper tube.

You can also note that you can use tips from any sufficiently strong diamegnetic material in place of a magnet with a polarity opposite to the magnetic support ring. those. replace the magnet + conical magnetic core combination, simply with a diamagnetic cone. fixation on the axis will be more reliable, but diamagnets are not characterized by strong interaction and high field strengths and a large “volume” of this field are needed in order to apply this in any way. Due to the fact that the field is axially uniform relative to the axis of rotation, changes in the magnetic field will not occur during rotation, i.e. such a bearing does not create resistance to rotation.

According to the logic of things, this principle should also be applicable for plasma suspension - a patched “magnetic bottle” (corktron), so wait and see.

Why am I so confident in the result? well, because it cannot help but exist :) the only thing that is possible is to make magnetic cores in the shape of a cone and a cup for a more “hard” field configuration.
Well, you can also find a video with a similar suspension:

here the author does not use any magnetic circuits and uses a focus on the needle, as is generally necessary, understanding Earnshaw’s theorem. but the rings are already rigidly fixed to the axis, which means you can spread the axis between them, which can be easily achieved using conical magnetic cores on magnets on the axis. those. Until the “bottom” of the “magnetic cup” is penetrated, it becomes increasingly difficult to push the magnetic circuit into the ring because the magnetic permeability of air is less than that of the magnetic circuit - a decrease in the air gap will lead to an increase in field strength. those. one axis is rigidly fixed mechanically - then there will be no need for support on the needle. those. see the very first picture.

P.S.
Here's what I found. from the series, the bad head won’t let go of his hands yet - the author is still Beletsky - it’s screwed up there, mother, don’t worry - the configuration of the field is quite complex, moreover, it is not uniform along the axis of rotation, i.e. when rotating, there will be a change in the magnetic induction in the axis with all the sticking out... pay attention to the ball in the ring magnet, on the other hand there is a cylinder in the ring magnet. those. the person stupidly ruined the principle of suspension described here.

Well, or soldered the suspension in the photo, i.e. the peppers in the photo use a support for the needle, and he hung a ball in place of the needle - oh shaitan - it worked - who would have thought (I remember they proved to me that I did not understand Earnshaw's theorem correctly), but hanging two balls and using only two rings apparently is not smart enough. those. the number of magnets in the device in the video can easily be reduced to 4, and possibly to 3, i.e. a configuration with a cylinder in one ring and a ball in the other can be considered experimentally proven to work, see the picture of the original idea. there I used two simitric stops and a cylinder + cone, although I think that the cone and part of the sphere from the pole to the diameter work the same.

therefore, the stop itself looks like this - it’s a magnetic circuit (i.e. iron, nickel, etc.) it’s just

a ring magnet is installed. the counter part is the same, only in reverse :) and two stops in the spacer work - comrade Earnshaw forbade working on one stop.

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Active magnetic bearings

Active magnetic bearings (AMP)
(produced by S2M Société de Mécanique Magnétique SA, 2, rue des Champs, F-27950 St. Marcel, France)

The main areas of application of active magnetic bearings are as part of turbomachines. The concept of no oil in compressors and turboexpanders makes it possible to achieve the highest reliability also due to the absence of wear on machine components. Active magnetic bearings (AMP) find everything greater application in many industries. To improve dynamic characteristics, increase reliability and efficiency, non-contact active magnetic bearings are used.

The operating principle of magnetic bearings is based on the effect of levitation in a magnetic field. The shaft in such bearings is literally words hanging in a powerful magnetic field. The sensor system constantly monitors the position of the shaft and sends signals to the stator position magnets, adjusting the force of attraction on one side or another.

1 . general description AMP systems

The active magnetic suspension consists of 2 separate parts:

Bearing;

Electronic control system

The magnetic suspension consists of electromagnets (power coils 1 and 3) that attract the rotor (2).

AMP components

1. Radial bearing

The radial bearing rotor, equipped with ferromagnetic plates, is supported by magnetic fields created by electromagnets located on the stator.

The rotor is placed in a suspended state in the center, without contacting the stator. Rotor position is controlled inductive sensors. They detect any deviation from the nominal position and provide signals that control the current in the electromagnets to return the rotor to its nominal position.

4 coils placed along the axes V and W , and shifted at an angle of 45° from the axes X and Y , keep the rotor in the center of the stator. There is no contact between the rotor and stator. Radial clearance 0.5-1mm; axial clearance 0.6-1.8 mm.

2. Thrust bearing

A thrust bearing works on the same principle. Electromagnets in the form of a permanent ring are located on both sides of the thrust disc mounted on the shaft. Electromagnets are fixed to the stator. The thrust disc is mounted on the rotor (for example, using the shrink fit method). Axial position sensors are usually located at the ends of the shaft.

3. Auxiliary (insurance)

bearings

Auxiliary bearings are used to support the rotor while the machine is stopped and in the event of failure of the AMS control system. During normal operation, these bearings remain stationary. The distance between the auxiliary bearings and the rotor is usually equal to half the air gap, however, if necessary, it can be reduced. Auxiliary bearings are mainly solid lubricated ball bearings, but other types of bearings such as plain bearings can also be used.

4. Electronic control system

An electronic control system controls the position of the rotor by modulating the current that passes through the electromagnets depending on the signal values ​​of the position sensors.

5. Electronic processing system signals

The signal sent by the position sensor is compared with a reference signal, which corresponds to the nominal rotor position. If the reference signal is zero, the nominal position corresponds to the center of the stator. When changing the reference signal, you can move the nominal position by half the air gap. The deviation signal is proportional to the difference between the nominal position and the current position of the rotor. This signal is transmitted to the processor, which in turn sends a correction signal to the power amplifier.

Ratio of output signal to deviation signaldetermined by the transfer function. The transfer function is selected to maintain the rotor as accurately as possible in its nominal position and to return it quickly and smoothly to this position in the event of disturbances. The transfer function determines the stiffness and damping of the magnetic suspension.

6. Power amplifier

This device supplies the bearing electromagnets with the current necessary to create a magnetic field that acts on the rotor. The power of the amplifiers depends on the maximum strength of the electromagnet, the air gap and the response time of the system automatic control(i.e. the speed at which this force must be changed when it encounters a disturbance). The physical dimensions of the electronic system do not have a direct relationship with the weight of the machine's rotor; they are most likely related to the ratio of the indicator between the magnitude of the interference and the weight of the rotor. Therefore, a small shell will be sufficient for a large mechanism equipped with a relatively heavy rotor subject to little disturbance. At the same time, a mechanism subject to greater interference must be equipped with a large electrical cabinet.

2. Some characteristics of AMP

Air gap

The air gap is the space between the rotor and stator. The amount of gap indicated e, depends on diameter D rotor or bearing.

As a rule, the following values ​​are usually used:

D (mm)	e(mm)
< 100	0,3 - 0,6
100 - 1 000	0,6 - 1,0

Rotational speed

The maximum rotation speed of a radial magnetic bearing depends only on the characteristics of the electromagnetic rotor plates, namely the resistance of the plates to centrifugal force. When using standard inserts, peripheral speeds of up to 200 m/s can be achieved. The rotation speed of the axial magnetic bearing is limited by the resistance of the cast steel thrust disk. A peripheral speed of 350 m/s can be achieved using standard equipment.

The AMP load depends on the ferromagnetic material used, the rotor diameter and the longitudinal length of the suspension stator. Maximum specific load of AMP made from standard material, is 0.9 N/cm². This maximum load is smaller compared to the corresponding values ​​of classical bearings, however, the high permissible peripheral speed allows the shaft diameter to be increased so as to obtain the largest possible contact surface and therefore the same load limit as for a classical bearing without the need to increase its length.

Power consumption

Active magnetic bearings have very low energy consumption. This energy consumption comes from losses due to hysteresis, eddy currents (Foucault currents) in the bearing (power taken from the shaft) and heat losses in the electronic shell. AMPs consume 10-100 times less energy than classic mechanisms of comparable sizes. Power consumption electronic system control, which requires an external current source, is also very low. Batteries are used to maintain the operating condition of the gimbal in the event of a network failure - in this case they turn on automatically.

Ambient conditions

AMPs can be installed directly in the operating environment, completely eliminating the need for appropriate couplings and devices, as well as barriers for thermal insulation. Today, active magnetic bearings operate in the most various conditions: vacuum, air, helium, hydrocarbon, oxygen, sea ​​water and uranium hexafluoride, as well as at temperatures from - 253° From to + 450 ° WITH.

3. Advantages of magnetic bearings

• Non-contact/liquidless
  - no mechanical friction
  - no oil
  - increased peripheral speed
  
• Increased reliability
  - operational reliability of the control cabinet > 52,000 hours.
  - operational reliability of EM bearings > 200,000 hours.
  - almost complete lack of preventative maintenance
  
• Smaller turbomachinery dimensions
  - lack of lubrication system
  - smaller dimensions (P = K*L*D²*N)
  - less weight
  
• Monitoring
  - bearing load
  - turbomachine load
• Adjustable Parameters
  - active magnetic bearing control system
  - rigidity (varies depending on the dynamics of the rotor)
  - damping (varies depending on the dynamics of the rotor)
  
• Sealless operation (compressor and drive in one housing)
  - bearings in process gas
  - wide operating temperature range
  - optimization of rotor dynamics by shortening it

The undeniable advantage of magnetic bearings is the complete absence of rubbing surfaces, and, consequently, wear, friction, and most importantly the absence of departure from working area particles generated during the operation of conventional bearings.

Active magnetic bearings are characterized by high load capacity and mechanical strength. They can be used when high speeds rotation, as well as in airless space and at different temperatures.

Materials provided by “S2M” company, France ( www.s2m.fr).

PREFACE

The main element of many machines is a rotor that rotates in bearings. The increase in rotation speeds and powers of rotary machines with a simultaneous tendency to reduce mass and overall dimensions puts forward the problem of increasing the durability of bearing units as a priority. Moreover, in a number of areas modern technology bearings are required that can operate reliably in extreme conditions: in vacuum, at high and low temperatures, ultra-clean technologies, in aggressive environments etc. The creation of such bearings is also a pressing technical problem.
The solution to these problems can be achieved by improving traditional rolling and sliding bearings. and the creation of non-traditional bearings that use different physical principles of operation.
Traditional rolling and sliding bearings (liquid and gas) have now reached a high technical level. However, the nature of the processes occurring in them limits and sometimes makes it fundamentally impossible to use these bearings to achieve the above goals. Thus, significant disadvantages of rolling bearings are the presence of mechanical contact between moving and stationary parts and the need to lubricate the raceways. In sliding bearings there is no mechanical contact, but an iodine system is required. lubricant to create a lubricating layer and seal this layer. It is obvious that improving sealing units can only reduce, but not completely eliminate, the mutual penetration of lubricant and external environment.
Bearings that use magnetic and electric fields to create support reactions are free from these disadvantages. Among them, active magnetic bearings (AMP) are of greatest practical interest. The work of the AMS is based on the well-known principle of active magnetic suspension of a ferromagnetic body: stabilization of the body in a given position is determined by the forces of magnetic attraction acting on the body from controlled electromagnets. Currents in the windings of electromagnets are generated using an automatic control system consisting of body movement sensors, an electronic controller and power amplifiers powered from an external source electrical energy.
First examples practical use active magnetic suspensions in measuring instruments date back to the 40s of the 20th century. They are associated with the names of D. Beams and D. Hriesinger (USA) and O. G. Katsnelson and A. S. Edelstein (USSR). The first active magnetic bearing was proposed and experimentally studied in 1960 by R. Sixsmith (USA). Wide practical use AMS in our country and abroad began in the early 70s of the 20th century.
The absence of mechanical contact and the need for lubrication in AMPs makes them very promising in many fields of technology. These are, first of all: turbines and pumps in vacuum and cryogenic technology; machines for ultra-clean technologies and for working in aggressive environments; machines and instruments for nuclear and space installations; horoscopes; inertial energy storage devices; as well as products for general mechanical engineering and instrument making - grinding and milling high-speed spindles, textile machines. centrifuges, turbines, balancing machines, vibration stands, robots, precision measuring instruments etc.
However, despite these successes, AMJIs are being implemented much more slowly than expected from predictions made in the early 1970s. First of all, this is explained by the industry’s slow acceptance of innovations, including AMP. Like any innovation, in order to be in demand, AMPs need to be popularized.
Unfortunately, at the time of writing these lines, only one book is devoted to active magnetic bearings: G. Schweitzer. N. Bleulerand A. Traxler “Active magnetic bearings”, ETH Zurich, 1994, 244 p., published in English and German. Small in volume, this book is aimed primarily at the reader who is taking the first steps in understanding the problems that arise when creating an AMP. Making very modest demands on the reader's engineering and mathematical background, the authors arrange the main ideas and concepts in such a thoughtful sequence that allows a beginner to easily get up to speed and conceptually master a new area. Undoubtedly, this book is a notable phenomenon, and its popularizing role can hardly be overestimated.
The reader may ask whether it was worth writing a real monograph, and not limiting ourselves to a translation of either the Russian language of the book cited above. Firstly, starting in 1992, I was invited to give lectures on AMS at Russian universities. Finland and Sweden. From these lectures a book grew. Secondly, many of my colleagues expressed a desire to receive a book about LMP, written for developers of machines with AMP. Third, I also realized that many engineers who do not specialize in the field of AMP need a book that explores the control object of an electromagnet.
The purpose of this book is to equip engineers with techniques mathematical modeling, synthesis and analysis of AMPs and thereby contribute to the arousal of interest in this new field of technology. I have no doubt that the book will also be useful for students of many technical specialties, especially during coursework and diploma design. When writing the book, I relied on 20 years of experience in the field of AMP as a scientific director of the research laboratory of magnetic supports at the Pskov Polytechnic Institute of St. Petersburg State technical university.
The book contains 10 chapters. Chapter 1 gives short description everyone possible types electromagnetic suspensions, the purpose of which is to broaden the reader’s horizons. Chapter 2, aimed at users of AMPs, introduces the reader to the technology of active magnetic bearings - the history of development, designs, characteristics, development problems and several examples of practical applications. Chapters 3 and 4 provide a methodology for calculating bearing magnetic circuits. An electromagnet as a control object is studied in Chapter 5. In Chapter 6, problems of controller synthesis and analysis of the dynamics of a single-power magnetic suspension are solved. This is a chapter about how to control the gimbal and what can prevent you from achieving the required dynamic qualities. The central place is occupied by Chapter 7, which examines the problems of controlling the suspension of a rigid rotor having five degrees of freedom, examines the interaction of the suspension and the drive motor, and also touches on the issue of creating unsupported rotors. electric machines. The effect of elastic bending deformations of the rotor on the dynamics of the gimbal is discussed in Chapter 8. Chapter 9 is devoted to digital control of the gimbal. The final chapter 10 examines a number of dynamic aspects associated with the implementation of rotor hangers in AMPs.
Regarding the list of references at the end of the book, I have not attempted to include all historically notable articles on AMP, and I apologize to those researchers whose contributions to this field are not mentioned.
Since the range of issues is very wide, it turned out to be impossible to maintain one system symbols throughout the book. However, each chapter uses a consistent notation.
I am grateful to my teachers, professors David Rakhmilevich Merknn and Anatoly Saulovnch Kelzon - they greatly contributed to the appearance of this book. I would like to thank my colleagues at the laboratory of magnetic supports and the university, especially Fedor Georgievich Kochevin, Mikhail Vadimovich Afanasyev. Valentin Vasilievich Andreen, Sergei Vladimirovich Smirnov, Sergei Gennadievich Stebikhov and Igor Ivanovich Morozov, through whose efforts many machines with AMP were created. Conversations and joint work with Professor Kamil Shamsuddnovich Khodzhaen and associate professors Vladimir Aleksandrovich Andreev, Valery Georgievich Bogov and Vyacheslav Grigorievich Matsevich were also useful to me. I would also like to acknowledge the contribution of graduate students and graduate students who worked with me with great enthusiasm in the field of AMP - these are Grigory Mikhailovich Kraizman, Nikolai Vadimovich Khmylko, Arkady Grigorievich Khrostitsky, Nikolai Mikhailovich Ilyin, Alexander Mikhailovich Vetlntsyn and Pavel Vasilievich Kiselev. The technical assistance provided by Elena Vladimirovna Zhuravleva and Andrei Semenovich Leontiev in preparing the manuscript for publication deserves special mention.
I would like to thank the Pskov Engineering Company and the Pskov Polytechnic Institute for their help in financing the publication of the book.

In a variety of modern electromechanical products and technical products, the magnetic bearing is the main component that determines the technical and economic characteristics and increases trouble-free operational period. Compared to traditional bearings, magnetic bearings completely eliminate the friction force between stationary and moving parts. The presence of this property makes it possible to implement increased speeds in designs magnetic systems. Magnetic bearings are made of high-temperature superconducting materials, which rationally influence their properties. These properties include a significant reduction in costs for model designs cooling systems and such important parameter, as long-term maintenance of a magnetic bearing in working condition.

Operating principle of magnetic suspensions

The operating principle of magnetic suspensions is based on the use of free levitation, which is created by magnetic and electric fields. A rotating shaft using such suspensions, without the use of physical contact, is literally suspended in a powerful magnetic field. Its relative revolutions pass without friction and wear, while achieving highest reliability. The fundamental component of a magnetic suspension is the magnetic system. Its main purpose is to create a magnetic field of the required shape, providing the required traction characteristics in work area at a certain control displacement of the rotor and the rigidity of the bearing itself. Such parameters of magnetic bearings are directly dependent on the design of the magnetic system, which must be developed and calculated based on its weight and size component - an expensive cryogenic cooling system. What the electromagnetic field of magnetic suspensions are capable of can be clearly seen in the operation of the children's toy Levitron. In practice, magnetic and electric suspensions exist in nine types, differing in their operating principle:

• magnetic and hydrodynamic suspensions;
• suspensions working on permanent magnets;
• active magnetic bearings;
• conditioning hangers;
• LC - resonant types of suspensions;
• induction bearings;
• diamagnetic types of suspensions;
• superconducting bearings;
• electrostatic suspensions.

If we test all these types of suspensions in terms of popularity, then in the current realities, active magnetic bearings (AMP) have taken the leading position. In appearance, they represent a mechatronic device system in which the stable state of the rotor is achieved by the forces of magnetic attraction present. These forces act on the rotor from the side of the electromagnets, electricity in which it is adjusted by an automatic control system based on sensor signals from the electronic control unit. Such control units can use either a traditional analogue or a more innovative digital signal processing system. Active magnetic bearings have excellent dynamic characteristics, reliability and high efficiency. Unique features active magnetic bearings contribute to their widespread adoption. AMPs are effectively used, for example, in the following equipment:
- gas turbine units;
- high-speed rotor systems;
- electric motors;
- turboexpanders;
- inertial energy storage devices, etc.
Currently, active magnetic bearings require an external current source and expensive and complex control equipment. At the moment, AMP developers are conducting active work to create a passive type of magnetic bearings.