Magnetic rotating device. Electrogravity is easy
Today, permanent magnets are found useful application in many areas of human life. Sometimes we do not notice their presence, however, in almost any apartment in various electrical appliances and in mechanical devices, if you look closely, you can find . Shaver and speaker, video player and Wall Clock, mobile phone and a microwave oven, a refrigerator door, finally - you can find permanent magnets everywhere.
They are used in medical technology and in measuring equipment, in various tools and in the automotive industry, in DC motors, in acoustic systems, in household electrical appliances and in many, many other places: radio engineering, instrument making, automation, telemechanics, etc. - none of these areas can do without the use of permanent magnets.
Specific solutions using permanent magnets could be listed endlessly, however, the subject of this article will be short review several applications of permanent magnets in electrical engineering and power industry.
Since the time of Oersted and Ampère, it has been widely known that current-carrying conductors and electromagnets interact with magnetic field permanent magnet. The operation of many engines and generators is based on this principle. You don't have to look far for examples. The fan in your computer's power supply has a rotor and a stator.
The impeller with blades is a rotor with permanent magnets arranged in a circle, and the stator is the core of the electromagnet. By remagnetizing the stator, the electronic circuit creates the effect of rotation of the stator magnetic field, the magnetic field of the stator, trying to be attracted to it, is followed by a magnetic rotor - the fan rotates. Rotation is implemented in a similar way hard drive, and work similarly.
In electric generators, permanent magnets have also found their application. Synchronous generators for home windmills, for example, are one of the application areas.
Generator coils are located on the generator stator around the circumference, which, during the operation of the windmill, are crossed by an alternating magnetic field of moving (under the action of the wind blowing on the blades) permanent magnets mounted on the rotor. Obeying, the conductors of the generator coils crossed by magnets direct current into the consumer circuit.
Such generators are used not only in windmills, but also in some industrial models, where permanent magnets are installed on the rotor instead of the excitation winding. The advantage of solutions with magnets is the ability to obtain a generator with low nominal speeds.
The conductive disk rotates in the field of a permanent magnet. The current consumption, passing through the disk, interacts with the magnetic field of the permanent magnet, and the disk rotates.
The greater the current, the higher the frequency of rotation of the disk, since the torque is created by the Lorentz force acting on moving charged particles inside the disk from the magnetic field of a permanent magnet. In fact, such a counter is a small power with a magnet on the stator.
To measure low currents, they are used - very sensitive measuring instruments. Here, a horseshoe magnet interacts with a small current-carrying coil that is suspended in the gap between the poles of a permanent magnet.
The deflection of the coil during the measurement is due to the torque that is created due to the magnetic induction that occurs when current passes through the coil. Thus, the deflection of the coil turns out to be proportional to the value of the resulting magnetic induction in the gap, and, accordingly, to the current in the coil wire. For small deviations, the scale of the galvanometer is linear.
You probably have a microwave in your kitchen. And it has two permanent magnets. To generate the microwave range, it is installed in the microwave. Inside the magnetron, electrons move in vacuum from the cathode to the anode, and in the process of movement, their trajectory must be curved so that the resonators on the anode are excited powerfully enough.
To bend the electron trajectory, ring permanent magnets are installed above and below the vacuum chamber of the magnetron. The magnetic field of permanent magnets bends the trajectories of electrons so that a powerful vortex of electrons is obtained, which excites resonators, which in turn generate microwave electromagnetic waves to heat food.
In order for the hard disk head to be accurately positioned, its movements in the process of writing and reading information must be very precisely controlled and controlled. Once again, a permanent magnet comes to the rescue. Inside the hard disk, in the magnetic field of a stationary permanent magnet, a coil with current moves, connected to the head.
When a current is applied to the head coil, the magnetic field of this current, depending on its value, repels the coil from the permanent magnet stronger or weaker, in one direction or another, thus the head starts to move, and with high precision. This movement is controlled by a microcontroller.
In order to increase the efficiency of energy consumption, in some countries, mechanical energy storage devices are being built for enterprises. These are electromechanical converters operating on the principle of inertial energy storage in the form of the kinetic energy of a rotating flywheel, called.
For example, in Germany, ATZ has developed a 20 MJ kinetic energy storage device with a capacity of 250 kW, with a specific energy content of approximately 100 Wh/kg. With a flywheel weighing 100 kg, rotating at 6000 rpm, a cylindrical structure with a diameter of 1.5 meters, high-quality bearings were needed. As a result, the lower bearing was made, of course, on the basis of permanent magnets.
Today is another experiment for you, which, we hope, will make you think. This is dynamic levitation in a magnetic field. In this case, one ring magnet is located above the same, but larger. Magnets are sold cheaper in this Chinese store.
This is a typical levitron, which has already been shown before (material). Large magnet and small. They are directed towards each other by the poles of the same name, respectively, they repel each other, due to this, levitation occurs. There is, of course, a magnetic cavity, or potential well, in which the upper magnet sits. Another point is that it rotates due to the gyroscopic moment, it does not turn over for some time until its speed decreases.
What is the purpose of the experiment?
If we spin the top just to keep it from flipping over, a question arises. What for? If you can take some kind of knitting needle, for example, a wooden one. Attach the upper magnet rigidly to it, and hang the loader from below and position this structure above the second one. Thus, in theory, it should also hang, and the lower weight will not allow it to roll over.
It will be necessary to set the mass balance of this spinning top very accurately. It would turn out magnetic levitation without energy costs.
How does it work?
Here is a ring magnet, a wooden needle is rigidly inserted into it. Next is a plastic plate with a hole for stabilizing the spokes. And at the end - a weight. A piece of plasticine for more convenient adjustment of the selection of mass. You can bite off a little bit and pick up such a mass of this whole structure so that the small ring magnet falls clearly into the levitation zone.
Let's carefully place it inside the bottom magnet, it kind of hangs. With a piece of plexiglass, you can try to stabilize its position. But for some reason this does not give him horizontal stabilization.
If you remove the plate and return everything back, then the magnet, together with the axis on which it rests, will fall sideways. When it rotates, for some reason it stabilizes in the magnetic pit. Although, pay attention, during this rotation it moves from side to side, probably by five millimeters. In the same way, it oscillates in a vertical position from top to bottom. It seems that this magnetic well has a certain backlash. As soon as the upper magnet falls into the pit, it captures and holds it. It remains only a gyroscopic moment to ensure that this magnet does not turn over.
What was the point of the experiment?
Check, if we make the shown construction with the axis, it actually does the same thing, preventing the magnet from flipping over. It brings it to the zone of the potential hole, we select the weight of this structure. The magnet is in a hole, but, getting into it, for some reason it does not stabilize horizontally. Still, this structure is falling to the side.
After this experiment, there is main question: why is it so unfair, when this magnet spins like a top, it hangs in a potential well, everything is perfectly stabilized and captured; and when the same conditions are created, everything is the same, that is, mass and height, the pit seems to disappear. It just pops out.
Why is there no stabilization of the upper magnet?
Presumably this is because it is impossible to make magnets perfect. Both in shape and magnetization. The field has some flaws, distortions, and therefore our two magnets cannot find an equilibrium state in it. They will definitely slide off, because there is no friction between them. And when the Levitron rotates, the fields seem to be smoothed out, the upper part of the structure does not have time to go to the side during rotation.
This is understandable, but what motivated the author of the video to do this experiment was the presence of a potential well. It was hoped that this pit had some margin of safety to hold the structure. But, alas, for some reason this did not happen. I would like to read your opinion about this riddle.
There is more material on this topic.
Studying the Faraday disk and the so-called. "Faraday's paradox", spent several simple experiments and made some interesting findings. First of all, about what should be paid the most attention in order to better understand the processes occurring in this (and similar) unipolar machine.
Understanding the principle of operation of the Faraday disk also helps to understand how all transformers, coils, generators, electric motors (including a unipolar generator and a unipolar motor), etc., work in general.
In the note, drawings and detailed video with different experiences illustrating all conclusions without formulas and calculations, "on the fingers."
All of the following is an attempt to comprehend without pretensions to academic reliability.
Direction of magnetic field lines
The main conclusion that I made for myself: the first thing you should always pay attention to in such systems is magnetic field geometry, direction and configuration lines of force.
Only the geometry of the magnetic field lines, their direction and configuration can bring some clarity to the understanding of the processes occurring in a unipolar generator or unipolar motor, Faraday disk, as well as any transformer, coil, electric motor, generator, etc.
For myself, I distributed the degree of importance as follows - 10% physics, 90% geometry(magnetic field) to understand what is happening in these systems.
Everything is described in more detail in the video (see below).
It must be understood that the Faraday disk and the external circuit with sliding contacts somehow form the well-known since school times frame- it is formed by a section of the disk from its center to the junction with a sliding contact at its edge, as well as the entire outer circuit(suitable conductors).
Direction of the Lorentz force, Ampère
The Ampère force is a special case of the Lorentz force (see Wikipedia).
The two pictures below show the Lorentz force acting on positive charges in the entire circuit ("frame") in the field of a donut-type magnet for the case when the external circuit is rigidly connected to the copper disk(i.e. when there are no sliding contacts and the external circuit is directly soldered to the disk).
1 rice. - for the case when the entire circuit is rotated by an external mechanical force ("generator").
2 rice. - for the case when a direct current is supplied through the circuit from an external source ("motor").
Click on one of the pictures to enlarge.
The Lorentz force is manifested (current is generated) only in sections of the circuit MOVING in a magnetic field
Unipolar generator
So, since the Lorentz force acting on the charged particles of the Faraday disk or a unipolar generator will act oppositely on different sections of the circuit and the disk, then in order to obtain current from this machine, only those sections of the circuit (if possible) should be set in motion (rotate), direction the Lorentz forces in which will coincide. The remaining sections must either be fixed or excluded from the circuit, or rotate to opposite side .
The rotation of the magnet does not change the uniformity of the magnetic field around the axis of rotation (see the last section), therefore, whether the magnet is standing or rotating does not matter (although there are no ideal magnets, and field inhomogeneity around axis of magnetization caused by insufficient magnet quality, also has some effect on the result).
Here an important role is played by which part of the entire circuit (including the lead wires and contacts) rotates and which is stationary (since the Lorentz force occurs only in the moving part). And most importantly - in what part of the magnetic field the rotating part is located, and from which part of the disk the current is taken.
For example, if the disk protrudes far beyond the magnet, then in the part of the disk protruding beyond the edge of the magnet, the current of the direction opposite to the current can be removed, which can be removed in the part of the disk located directly above the magnet.
Unipolar motor
All of the above about the generator is also true for the "engine" mode.
It is necessary to apply current, if possible, to those parts of the disk in which the Lorentz force will be directed in one direction. It is these sections that must be released, allowing them to rotate freely and "break" the circuit in the appropriate places by placing sliding contacts (see the figures below).
The remaining areas should, if possible, be either excluded or minimized.
Video - experiments and conclusions
Time different stages this video:
3 min 34 sec- first experiences
7 min 08 sec- what to pay the main attention and continuation of experiments
16 min 43 sec- key explanation
22 min 53 sec- MAIN EXPERIENCE
28 min 51 sec- Part 2, interesting observations and more experiments
37 min 17 sec- erroneous conclusion of one of the experiments
41 min 01 sec- about Faraday's paradox
What repels what?
A fellow electronics engineer and I discussed this topic for a long time and he expressed an idea built around the word " repelled".
The idea with which I agree is that if something starts moving, then it must be repelled from something. If something is moving, then it is moving relative to something.
Simply put, we can say that part of the conductor (the outer circuit or disk) is repelled by the magnet! Accordingly, repulsive forces act on the magnet (through the field). Otherwise, the whole picture collapses and loses logic. About the rotation of the magnet - see the section below.
In the pictures (you can click to enlarge) - options for the "engine" mode.
For the "generator" mode, the same principles work.
Here the action-reaction occurs between the two main "participants":
Accordingly, when the disk rotates, and the magnet is stationary, then the action-reaction occurs between magnet and part of the disk .
And when magnet rotates together with the disk, then the action-reaction occurs between magnet and outer part of the chain (fixed lead wires). The fact is that the rotation of a magnet relative to the outer section of the circuit is the same as the rotation of the outer section of the circuit relative to a fixed magnet (but in the opposite direction). In this case, the copper disk almost does not participate in the "repulsion" process.
It turns out that, unlike the charged particles of a conductor (which can move inside it), the magnetic field is rigidly connected to the magnet. Incl. along a circle around the axis of magnetization.
And one more conclusion: the force that attracts two permanent magnets is not some mysterious force perpendicular to the Lorentz force, but this is the Lorentz force. It's all about the "rotation" of electrons and the very " geometry". But that is another story...
Rotation of a bare magnet
There is a funny experience at the end of the video and a conclusion as to why part the electric circuit can be made to rotate, but it is not possible to make the "donut" magnet rotate around the axis of magnetization (with a stationary DC electric circuit).
The conductor can be broken in places of the opposite direction of the Lorentz force, but the magnet cannot be broken.
The fact is that the magnet and the entire conductor (the external circuit and the disk itself) form a connected pair - two interacting systems, each of which closed inside yourself . In the case of a conductor - closed electrical circuit, in the case of a magnet - "closed" lines of force magnetic field.
At the same time, in an electrical circuit, the conductor can be physically break, without breaking the circuit itself (by placing the disk and sliding contacts), in those places where the Lorentz force "unfolds" in the opposite direction, "released" different sections of the electric circuit to move (rotate) each in its own opposite direction to each other, and break the "chain" of magnetic field or magnet lines of force, so that different sections of the magnetic field "did not interfere" with each other - apparently impossible (?). No similarities of "sliding contacts" for a magnetic field or a magnet seem to have been invented yet.
Therefore, there is a problem with the rotation of the magnet - its magnetic field is an integral system, which is always closed in itself and inseparable in the body of the magnet. In it, opposite forces in areas where the magnetic field is in different directions are mutually compensated, leaving the magnet motionless.
Wherein, Job Lorentz force, Ampere in a fixed conductor in the field of a magnet, apparently goes not only to heat the conductor, but also to distortion of magnetic field lines magnet.
BY THE WAY! It would be interesting to conduct an experiment in which, through a fixed conductor located in the field of a magnet, pass huge current, and see how the magnet will react. Will the magnet heat up, demagnetize, or maybe it will just break into pieces (and then it’s interesting - in what places?).
All of the above is an attempt to comprehend without pretensions to academic reliability.
Questions
What remains not completely clear and needs to be checked:
1. Is it still possible to make the magnet rotate separately from the disk?
If you give the opportunity to both the disk and the magnet, freely rotate independently, and apply current to the disk through the sliding contacts, will both the disk and the magnet rotate? And if so, in which direction will the magnet rotate? For the experiment, you need a large Neodymium magnet- I don't have it yet. With an ordinary magnet, there is not enough strength of the magnetic field.
2. Rotation of different parts of the disk in different directions
If done freely rotating independently of each other and from a stationary magnet - the central part of the disk (above the "donut hole" of the magnet), the middle part of the disk, as well as the part of the disk protruding beyond the edge of the magnet, and apply current through sliding contacts (including sliding contacts between these rotating parts of the disk ) - will the central and extreme parts of the disk rotate in one direction, and the middle one - in the opposite direction?
3. Lorentz force inside a magnet
Does the Lorentz force act on particles inside a magnet whose magnetic field is distorted by external forces?
The problem of inventing a perpetual motion machine began to worry designers and mechanics for a long time. The presence of such a device on a large scale could greatly change life in all its manifestations and accelerate the development of most areas of science and industry.
From the history of the invention of the magnetic motor
The history of the first appearance of a magnetic motor begins in 1969. It was in this year that the ball was invented and constructed the first prototype of this mechanism, which consisted of a wooden case and several magnets.
The strength of these magnets was so weak that its energy was only enough to rotate the rotor. This magnetic motor was created by designer Michael Brady with his own hands. The inventor devoted most of his life to the design of engines. And in the 90s of the last century, he created a completely new model, for which he received a patent.
The first steps
Taking a magnetic motor as a basis, with his own hands and with the participation of an assistant, Brady designed an electric generator that had a small power of 6 kW. The power source was a power motor, which worked exclusively on permanent magnets.
But this model had its drawback - the engine speed and power remained invariably constant.
This emerging difficulty prompted scientists to create a model of a device in which it was possible to change the force of the torque and the speed of rotation of the rotor. To do this, along with permanent magnets, it was necessary to add magnetic coils to the design to enhance the magnetic field.
So is it possible now, when science has stepped far forward, and we are surrounded by a large number of things unique in nature, to design a permanent magnet motor with our own hands? Such an engine can be constructed, but its efficiency will be quite low, and the invention itself will look more like a demonstration model than a serious unit.
What will be needed?
To create a simplified prototype of a magnetic motor, you will need neodymium magnets, a plastic or other dielectric rim, a shaft with the least rotational resistance, some tools and other little things that can always be at hand.
Assembly process
You should start assembling a magnetic motor with your own hands by firmly fixing neodymium magnets around the entire circumference of the existing rim. Magnets should be flat and have a maximum area. You can fix the magnets with glue, they should be located as close as possible to each other in order to create a continuous single magnetic field. Moreover, all magnets must be turned outward with the same pole.
A rim with magnets firmly fixed on it should be fixed on a horizontal plane, for example, on a sheet of plywood or a board. In the center of this design, you need to place a rotating shaft, a little higher than the height of the rim.
A strip or tube of non-conductive material should extend from the top of the shaft, slightly longer than the radius of the rim, on which the magnet will also be fixed parallel to the magnetic ring. Moreover, this magnet should be located with the same pole to the other magnets as those fixed on the rim.
Thus, by giving a slight acceleration to the magnet located on the shaft, one can observe its rotation around the axis. In this case, the rotation will be constant if a continuous magnetic field is formed around the rim. Such rotation is achieved by the interaction of magnetic fields of the same sign, namely their repulsion. The magnetic field created around the rim is stronger and tries to push the single magnet out of its limits, which causes it to rotate.
Even if you use more strong magnets, then the potential of this device will be very small and cannot carry any practical function. If you try to recreate it on a large scale, then the generated magnetic field will be so powerful that it will be very dangerous for a person to be in the zone of its action. In addition, the strength of huge magnets can be enough to cause insoluble problems during their transportation associated with the attraction of equipment, rails and other metal objects.
Into the future with perpetual motion
The possibility of inventing a perpetual motion machine has been repeatedly refuted over many decades by many physicists, designers and other scientists. The impossibility of its creation was proved theoretically and stimulated the emergence of various laws and postulates.
Hope always remains, because in the world there are a huge number of inexplicable phenomena, the secret of which can serve as a new impetus in the development of science. After all, having the opportunity to design a perpetual motion machine and use it rationally, you can forget once and for all about in large numbers problems that engulf civilizations on a global scale.
One can forget once and for all about the problem of extracting fuel resources and, as a result, about the environmental problem arising from their use. The creation of a perpetual magnetic motor will save forests, water resources and never return to issues related to energy instability. The names of the inventors of this masterpiece can rise to the peak of fame and reverence and be inscribed in history for many centuries. After all, these people will be worthy of the highest wealth, awards and honors for their achievements.
As shown earlier, one of the most important advantages of polyphase systems is the production of a rotating magnetic field using fixed coils, which is the basis for the operation of AC motors. Consideration of this issue will begin with an analysis of the magnetic field of a coil with a sinusoidal current.
The magnetic field of a coil with a sinusoidal current
When a sinusoidal current is passed through the coil winding, it creates a magnetic field, the induction vector of which changes (pulsates) along this coil also according to a sinusoidal law. The instantaneous orientation of the magnetic induction vector in space depends on the winding of the coil and the instantaneous direction of the current in it and is determined by the rule of the right gimlet. So for the case shown in Fig. 1, the magnetic induction vector is directed upward along the coil axis. After half a period, when with the same module the current changes its sign to the opposite, the magnetic induction vector with the same absolute value will change its orientation in space by 1800. In view of the foregoing, the magnetic field of a coil with a sinusoidal current is called pulsating.
Circular rotating magnetic field of two- and three-phase windings
A circular rotating magnetic field is a field whose magnetic induction vector, without changing in absolute value, rotates in space with a constant angular frequency.
To create a circular rotating field, two conditions must be met:
The axes of the coils must be shifted in space relative to each other by a certain angle (for a two-phase system - by 90 0, for a three-phase system - by 120 0).
The currents feeding the coils must be shifted in phase according to the spatial displacement of the coils.
Let us consider obtaining a circular rotating magnetic field in the case of a two-phase Tesla system (Fig. 2a).
When passing harmonic currents through the coils, each of them, in accordance with the above, will create a pulsating magnetic field. The vectors and characterizing these fields are directed along the axes of the corresponding coils, and their amplitudes also change according to the harmonic law. If the current in coil B lags behind the current in coil A by 90 0 (see Fig. 2, b), then.
Let us find the projections of the resulting vector of magnetic induction on the x and y axes of the Cartesian coordinate system associated with the axes of the coils:
The module of the resulting vector of magnetic induction in accordance with fig. 2, in is equal to
The obtained relations (1) and (2) show that the vector of the resulting magnetic field is unchanged in absolute value and rotates in space with a constant angular frequency , describing a circle, which corresponds to a circular rotating field.
Let us show that a symmetrical three-phase system of coils (see Fig. 3a) also makes it possible to obtain a circular rotating magnetic field.
Each of the coils A, B and C, when passing harmonic currents through them, creates a pulsating magnetic field. The vector diagram in space for these fields is shown in fig. 3b. For the projections of the resulting vector of magnetic induction on
axes of the Cartesian coordinate system, the y-axis of which is aligned with the magnetic axis of phase A, can be written
The above relations take into account the spatial arrangement of the coils, but they are also fed by a three-phase system of currents with a temporary phase shift of 1200. Therefore, for the instantaneous values of the coil inductions, the relations
;
;.
Substituting these expressions into (3) and (4), we get:
|
|
In accordance with (5) and (6) and fig. 2,c for the modulus of the magnetic induction vector of the resulting field of three coils with current, we can write:
,
and the vector itself makes an angle a with the x-axis, for which
,
Thus, in this case, there is also a magnetic induction vector that is constant in absolute value and rotates in space with a constant angular frequency , which corresponds to a circular field.
Magnetic field in an electric car
In order to amplify and concentrate the magnetic field in an electric machine, a magnetic circuit is created for it. The electric machine consists of two main parts (see Fig. 4): a fixed stator and a rotating rotor, made respectively in the form of hollow and solid cylinders.
Three identical windings are located on the stator, the magnetic axes of which are shifted along the bore of the magnetic circuit by 2/3 of the pole division, the value of which is determined by the expression
,
where is the radius of the bore of the magnetic circuit, and p is the number of pairs of poles (the number of equivalent rotating permanent magnets that create a magnetic field, in the case shown in Fig. 4, p = 1).
On fig. 4 solid lines (A, B and C) mark the positive directions of pulsating magnetic fields along the axes of the windings A, B and C.
Assuming the magnetic permeability of the steel to be infinitely large, we plot the distribution curve of magnetic induction in the air gap of the machine, created by the winding of phase A, for a certain moment of time t (Fig. 5). When constructing, we take into account that the curve changes abruptly at the locations of the coil sides, and in sections devoid of current, there are horizontal sections.
Z 
Let us replace this curve with a sinusoid (it should be pointed out that for real machines, due to the appropriate design of the phase windings for the resulting field, such a replacement is associated with very small errors). Taking the amplitude of this sinusoid for the selected time t equal to VA, we write
|
|
;|
|
.Summing relations (10)…(12), taking into account the fact that the sum of the last terms in their right parts is identically equal to zero, we obtain the expression for the resulting field along the air gap of the machine
which is the traveling wave equation.
The magnetic induction is constant if 
. Thus, if we mentally select a certain point in the air gap and move it along the magnetic core bore at a speed
,
then the magnetic induction for this point will remain unchanged. This means that over time, the magnetic induction distribution curve, without changing its shape, moves along the stator circumference. Therefore, the resulting magnetic field rotates at a constant speed. This speed is usually defined in revolutions per minute:
.
The principle of operation of asynchronous and synchronous motors
Device induction motor corresponds to the image in fig. 4. The rotating magnetic field created by current-carrying windings located on the stator interacts with the currents of the rotor, causing it to rotate. The squirrel-cage induction motor is currently the most widely used due to its simplicity and reliability. Current-carrying copper or aluminum rods are placed in the grooves of the rotor of such a machine. The ends of all rods from both ends of the rotor are connected by copper or aluminum rings, which short-circuit the rods. Hence the name of the rotor.
In the short-circuited winding of the rotor, under the action of the EMF caused by the rotating field of the stator, eddy currents arise. Interacting with the field, they involve the rotor in rotation at a speed fundamentally lower than the field rotation speed 0 . Hence the name of the motor - asynchronous.
Value
called relative slip. For motors of normal execution S=0.02…0.07. The inequality of the velocities of the magnetic field and the rotor becomes obvious if we take into account that at , the rotating magnetic field will not cross the current-carrying rods of the rotor and, therefore, the currents involved in the creation of the torque will not be induced in them.
The fundamental difference between a synchronous motor and an asynchronous motor is the design of the rotor. The latter in a synchronous motor is a magnet made (at relatively low power) on the basis of a permanent magnet or on the basis of an electromagnet. Since the opposite poles of the magnets are attracted, the rotating magnetic field of the stator, which can be interpreted as a rotating magnet, drags the magnetic rotor along with it, and their speeds are equal. This explains the name of the motor - synchronous.
In conclusion, we note that, unlike an asynchronous motor, which usually does not exceed 0.8 ... 0.85, a synchronous motor can achieve a larger value and even make the current lead the voltage in phase. In this case, like capacitor banks, a synchronous machine is used to improve the power factor.
Literature
Basics circuit theory: Proc. for universities /G.V.Zeveke, P.A.Ionkin, A.V.Netushil, S.V.Strakhov. –5th ed., revised. -M.: Energoatomizdat, 1989. -528s.
Bessonov L.A. Theoretical basis electrical engineering: Electrical circuits. Proc. for students of electrical, energy and instrument-making specialties of universities. –7th ed., revised. and additional –M.: Higher. school, 1978. -528s.
Theoretical fundamentals of electrical engineering. Proc. for universities. In three tons. Under the total. ed. K.M. Polivanova. T.1. K.M. Polivanov. Linear electrical circuits with lumped constants. -M.: Energy - 1972. -240s.
test questions
What field is called pulsating?
What field is called a rotating circular field?
What conditions are necessary to create a circular rotating magnetic field?
What is the principle of operation of a squirrel-cage induction motor?
What is the principle of operation of a synchronous motor?
At what synchronous speeds are AC motors of general industrial design produced in our country?
