The main purpose of any engine is the communication (transfer) of mechanical energy to the working bodies of production mechanisms, which they need to perform certain technological operations. This mechanical energy is generated by the electric motor. electrical energy consumed by it from the electrical network to which it is connected. In other words, an electric motor converts electrical energy into mechanical energy.
The amount of mechanical energy generated by the engine per unit time is called its power. The mechanical power on the motor shaft is determined by the product of the motor torque and its speed. Note that some engines have translational motion, so their mechanical power depends on the force developed by the engine and the speed of this translational motion.
Depending on the nature of the supply voltage, there are DC and alternating current. The most common DC motors include, for example, motors with independent, series and mixed excitation, and examples of AC motors are asynchronous and synchronous motors.
Despite the variety of existing electric motors (including special purpose), the action of any of them is based on the interaction magnetic field and conductor with electric current or magnetic field and ferromagnetic body or permanent magnet.
Consider the interaction of a magnetic field and a conductor with an electric current. Let us assume that in the magnetic field of a magnet with poles N-S(Fig. 1),
Rice. I. Interaction of a magnetic field and a conductor with current.
whose field lines are shown as thin lines, a conductor with drain I is placed perpendicular to these lines. Then, according to a well-known physical law, this conductor will be acted upon by a force F (Ampère force), which is proportional to the magnetic field induction B, the length of the conductor I and the current strength I:
F=BlI. (1)
The direction of the force F acting on the conductor can be determined by the so-called left hand rule: if the fingers of the left hand are extended in the direction of the current I, and the palm is positioned so that the magnetic field lines enter it, then the bent thumb will show the direction of the force F.
Note that according to the law electromagnetic induction the current passing through the conductor will create its own magnetic field with concentric lines of force around the conductor (this field is not shown in Fig. 1), and therefore the picture of the magnetic field between the poles of the magnet will change somewhat. However, this circumstance does not change the essence of the phenomenon under consideration.
Shown in fig. 1 circuit can serve the simplest model translational motion motor, since under the action of the force F, the current-carrying conductor tends to make a rectilinear movement in the direction of this force.
To explain the principle of torque generation in engines rotary motion Let us consider the behavior in the field of the same magnet of a frame with current, consisting of conductors A and B (Fig. 2a). The current to the conductors of the frame is supplied from external source direct current through two contact rings K, mounted on the axis of rotation of the frame 00 ".
When shown in Fig. 2, and the position of the frame and the directions of the current and magnetic field on the conductors of the frame A and B, forces F will act, having, in accordance with the left hand rule, the directions indicated in the figure. These forces will create a torque M relative to the axis of the frame 00 ", under the action of which the frame will begin to rotate counterclockwise.
In the course of physics, it is shown that this moment is directly proportional to the strength of the current I, the magnetic field induction B, the area of the frame with current 5 and depends on the angle a between the lines of the magnetic field and the axis of the frame aa y perpendicular to its plane:
M-BIS sin a-Mmax sin a, (2)
where Mmax=BIS is the maximum moment developed by the frame. At the position of the frame shown in Fig. 2a, the angle a is 90°, so the moment acting on the frame is maximum. 
Rice. 2. The principle of operation of the DC motor. a - moment formation at a=90°; b - the formation of a moment at a \u003d 270 ": e - the formation of a torque constant in the direction.
Let us now consider another position of the frame, when it turns half a turn and conductor A is already under pole 5, and conductor B is under pole N (Fig. 2.6). Since the direction of the current in the conductors remained the same, then, according to the same left-hand rule, it can be determined that in this position of the frame, the force F acting on its conductors changed its direction to the opposite. Accordingly, the direction of the torque M will also change to the opposite, which will tend to rotate the frame in the other direction, clockwise. The same conclusion is not difficult to draw on the basis of the analysis of formula (2): since the angle a has become equal to 270 ° (90 ° -f -) -180 °) or, what is the same, -90 °, then sin a \u003d -1 and the moment changed its sign to the opposite.
Thus, the frame, under the action of a moment changing in direction, will oscillate about its axis of rotation 00 ". Such a device, obviously, cannot be used as the basis for an engine of rotational motion of a constant direction, from which a moment of constant direction and a constant direction of rotation are usually required.
What must be done so that the resulting torque on the frame has a constant direction? It is easy to see that there are two fundamental possibilities for this:
1) change the direction of the current in the conductors of the frame when the position of the conductors under the poles of the magnetic system changes;
2) to change the direction of the magnetic field during the rotation of the frame and the direction of the current in it remains unchanged, or, in other words, to create a rotating magnetic field.
The first of these principles is used in DC motors, the second is the basis for the operation of AC motors.
Let us first consider the formation of a torque constant in the direction by changing the direction of the current in the loop and thereby find out the principle of operation of DC motors.
To change the direction of the current in the loop conductors, it is obviously necessary to have a device that would change the direction of the current in the loop depending on the position of its conductors.
The simplest possible mechanical device of this type can be implemented by simply changing the design of sliding contacts K (Fig. 2, a, b), which serve to supply current to the frame. This transformation consists in replacing two contact rings with one, but consisting of two halves (segments) isolated from each other, to which frame conductors A and B are connected (Fig. 2, c). In this case, when the frame is rotated half a turn, the direction of the current in the conductors will change to the opposite, so the torque will retain its direction and the frame will continue to rotate in the same direction. A similar mechanical switching device, called a commutator, is used in conventional DC motors. In some special motor designs, discussed below, this switching device is made non-contact (electronic).
A real DC motor, a simplified diagram of which is shown in fig. 3, has, of course, much more complex structure compared to that shown in Fig. 2, in. To obtain a large torque, usually several dozen frames are taken, which form the winding of 1 armature. The armature winding conductors are placed in the grooves of the cylindrical ferromagnetic core 2, and their ends are connected to the corresponding number of ring segments isolated from each other, forming a collector (not shown in the figure). 
Rice. 3. Scheme of a DC motor.
Rice. 4 How it works synchronous motor. a - equilibrium position; b - the formation of torque
The core, winding and collector form the armature of the motor, which rotates in bearings mounted in the motor housing. The current to the armature conductors is supplied from the DC network using sliding brush contacts.
The magnetic field is created by the poles 3 of the magnet located in the housing 4 of the motor. This magnetic field is commonly referred to as the excitation field. For its formation, permanent magnets or electromagnets can be used.
The winding of an electromagnet is usually called the excitation winding (item 5 in Fig. 3). The excitation winding is connected to the DC network and can be switched on independently of the armature winding or in series with it. In the first case, the motor is called a motor with independent excitation, in the second case - with sequential excitation.
Some DC motors have two excitation windings - independent and series. Such motors are called mixed-excitation motors. The number of poles of the excitation magnetic field can be more than two, for example four, as shown in Fig. 3.
We now turn to the consideration of AC motors.
Let us turn again to the experiments with the frame and consider its position, shown in Fig. 4a. Note that this figure is a simplified frontal view of the circuit in Fig. 2,a, and the direction of the current in the conductor flowing into the plane of the drawing is indicated by a cross, and flowing out of the plane of the drawing is indicated by a dot.
From formula (2) it follows that in the depicted horizontal position of the frame, the torque acting on the frame is zero (a = 0), although the forces acting on conductors A and B are non-zero. The explanation for this situation is that the direction of action of these forces passes through the axis of rotation of the frame 00", therefore, the arm of the forces F relative to this axis is zero and no torque is generated.
This position of the frame is balanced, and it maintains a state of rest.
Let's turn it around somehow magnet N-S clockwise through some angle a, without changing the direction of the current in the conductors, as shown in Fig. 4.6. It is easy to see that such a rotation of the magnet will cause a change in the direction of the forces F and the appearance of a shoulder for the application of these forces relative to the axis of rotation of the frame. As a result, in accordance with formula (2), a torque will begin to act on the frame, tending to return the frame to an equilibrium position, and as a result, the frame will turn after the magnet by the same angle a.
If now we begin to rotate the magnet N-S uniformly, then the frame will also rotate in the same direction synchronously with the rotation of the magnetic field, since when “non-synchronism” appears between the rotation of the field 12 and the frame (a = / = O), the moment immediately begins to act on the latter , seeking to synchronize this rotation. Motors using this principle are therefore called synchronous motors, and their torque, determined using formula (2), is often called the synchronizing torque.
So, for the operation of a synchronous motor, it is necessary to create a rotating magnetic field and place conductors in it, flowing around with a constant current in the direction.
Consider how a rotating magnetic field is obtained in real AC motors. The rotating magnetic field of a synchronous motor is formed using a system of windings connected to an alternating current network. Typically, synchronous motors use three-phase windings laid in the grooves of the motor stator core with a certain spatial shift around the circumference. In the theory of electrical machines, it is shown that if such a winding is connected to a three-phase AC network, then the currents form a rotating in air gap motor magnetic field, the rotational speed of which n0 is determined by the frequency of the current in the network f and the number of pairs of motor poles p formed by the stator winding: 
The interaction of this rotating magnetic field with the current in the conductors of the rotor winding will cause the rotation of the synchronous motor, which will occur synchronously with the rotation of the stator magnetic field.
In the absence of a load moment on the shaft of a synchronous motor, the axes of the magnetic fields of the stator and rotor coincide (cc=0), the motor does not develop torque and rotates with a frequency n0. When a moment of resistance (load) appears on the motor, the axis of the rotor field will begin to lag behind the axis of the stator field, and this process will continue until, at a certain angle af0, the torque (synchronizing) of the motor becomes equal to the load torque. A synchronous motor will continue to rotate at a frequency u, overcoming the moment of resistance on its own.
This position will be maintained until the value of the maximum engine torque corresponding to the angle α=90°. As the load torque increases further, the synchronous motor is said to "fall out of sync" and stop. Thus, a synchronous motor can only overcome a certain, nominal moment of resistance, which for synchronous motors corresponds to an angle a=20-30°.
A simplified diagram of a synchronous motor is shown in fig. 5. In the motor case, in the grooves of the core I, a three-phase alternating current winding 2 is laid, which, when connected to an alternating current network, forms a rotating magnetic field. The core with the winding form a fixed part of the motor - the stator.
The role of the current loop is performed by the excitation winding 3 of the motor, located on the ferromagnetic core 4. The excitation winding has several tens of turns (frames) and is connected to the DC network through slip rings and a brush contact (these parts of the motor are not shown in Fig. 5).
The excitation winding, core and slip rings together with the motor shaft form the motor rotor - its rotating part.
The synchronous motor built according to the scheme of fig. 5 is usually called salient pole, which is associated with the presence of poles at the rotor core. Along with this, there are so-called implicit-pole synchronous motors, in which the rotor core does not have pronounced poles. 
Rice. 5. Scheme of a synchronous motor with electromagnetic excitation.
The action of a synchronous motor can be based, in addition to the principle of interaction of a magnetic field and a conductor with current discussed above, also on the principle of interaction of a magnetic field with a permanent magnet or a ferromagnetic body. To illustrate this principle, consider the behavior of a permanent magnet 2 placed in the field of magnet 1, as shown in Fig. 6. From the course of physics it is known that the opposite poles of two magnets always attract, and the same poles repel. In accordance with this, magnet 2 will take a position in which its north pole will be at the south pole of magnet 1, and the south - at the north. This position will be equilibrium for the considered system of two magnets. 
Rice. 6. Scheme of a synchronous motor.
Rice. 7. The principle of operation of an asynchronous motor.
In this case, we note a very important circumstance: the equilibrium position simultaneously corresponds to the minimum magnetic resistance in the path of the magnetic flux and the minimum curvature of the magnetic field lines. In other words, the magnets tend to take such a mutual position in which the lines of the magnetic field are slightly curved, and the magnetic resistance to the magnetic flux is minimal.
Now it is not difficult to figure out what will happen to magnet 2 if we start to rotate magnet I. Obviously, it will also begin to rotate together with magnet I, trying to maintain an equilibrium position, and the rotational frequencies of both magnets will be the same (synchronous). Synchronous motors whose rotors are permanent magnets are called permanent magnet synchronous motors.
The same synchronous rotation of the rotor can also be obtained if, instead of permanent magnet 2, a ferromagnetic body of the same shape is placed in the field of permanent magnet I. Being placed in a magnetic field, the ferromagnetic rotor will be magnetized, and at the north pole of the magnet a south pole is formed, and at the south pole of the magnet - the north pole of the ferromagnetic body. The ferromagnetic rotor will tend to maintain this position even during the rotation of the magnetic field, which determines the operation of a synchronous motor with a rotor in the form of a ferromagnetic body. This type of motor is called a synchronous reluctance motor. Note that for the operation of such an engine, its rotor must in principle have pronounced poles, and their number (not necessarily two) must be equal to the number of poles of the rotating magnetic field.
The formation of a rotating magnetic field of a reactive and permanent magnet synchronous motor occurs in the same way as in a conventional synchronous motor - using a stator winding connected to an alternating current network.
To explain the principle of operation of another, very common type of AC motor - an asynchronous one - we again turn to experiments with a frame placed in a magnetic field. However, this time we will not supply current to the loop, but make it closed, as shown in Fig. 7. Let's find out what will happen to such a frame if we start rotating the poles of the magnet again, for example, with a clockwise rotation frequency.
Since the frame is initially stationary, when the magnet is rotated, the magnetic flux passing through the frame will begin to change. Then, in accordance with the law of electromagnetic induction (Faraday's law), the frame will begin to be induced (induced) electromotive force(EMF) of induction, under the influence of which a current will begin to flow through the conductors of the frame. The interaction of this current with a magnetic field will lead to the appearance of a torque, under the influence of which the frame will begin to rotate. This is the principle of operation of an asynchronous motor.
To determine the direction of rotation of the frame, we apply Lenz's law, according to which the currents flowing in the frame with changes in the magnetic flux through its circuit have such a direction in which they prevent this change. And since in the experiment this change is caused by the rotation of the magnetic field, the currents in the loop will have such a direction in which the resulting torque will turn the loop in the same direction as the field, since only in this case will there be a decrease in the change in the magnetic flux through the frame. Thus, the frame will begin to rotate in the same direction as the field, but with a rotation frequency n.
In this case, we note one fundamentally important circumstance - the frequency of rotation of the frame n will always be somewhat less than the frequency of rotation of the magnetic field n0. Indeed, if we assume the opposite, i.e., that the frequencies of rotation of the loop and the field are the same, then the magnetic flux through the loop loop will not change, the EMF and currents in the loop will not be induced, respectively, and the torque will disappear.
Thus, in order to create a torque on the frame, it is fundamentally necessary to distinguish between the frequencies of rotation of the magnetic field n0 and the frame n, i.e., the asynchrony (non-synchronism) of their rotation, which is reflected in the name of this type of electric motor. The degree of difference between these frequencies, rotation is numerically characterized by the so-called slip of the asynchronous motor s, determined by the formula 
At the same time, it should be noted that when a load moment appears on the axis of the frame due to a decrease in the frequency of rotation of the frame n (the frame is braked), the motor slip will increase and the magnetic flux through the frame contour will begin to change more strongly. In this case, the EMF and currents in the loop will begin to increase and, accordingly, the motor torque. This process will take place until, at a certain frequency of rotation of the frame, the torque of the frame balances the load moment and a new steady state of operation occurs. When the load is reduced, the reverse process occurs.
So, for the operation of an asynchronous motor, it is necessary to have a rotating magnetic field and closed frames (circuits) on the rotating part of the motor - the rhetor.
The rotating magnetic field of an asynchronous motor (Fig. 8) is formed in the same way as that of a synchronous motor - with the help of windings 2 located in the grooves of the stator package I and connected to the AC network.
The windings 3 of the rotor of an induction motor usually consist of several dozen closed frames (circuits) and have two main designs: short-circuited and phase.
When performing a short-circuited winding, the conductors laid in the grooves of the ferromagnetic package 4 of the rotor are short-circuited. Typically, such a winding is obtained by pouring molten aluminum into the grooves of the package and is called the "squirrel cage".
In the manufacture of a "phase" winding, the ends of the phases of the winding are brought out through sliding contacts (rings), which makes it possible to include various additional resistors in the rotor circuit, which are necessary, for example, to start the engine or regulate its speed. 
Rice. 8. Scheme of an asynchronous motor.
It should be noted that in order to obtain the torque of an induction motor, it is not necessary to place a winding of electrical conductors on the rotor. It is possible to make the rotor simply in the form of a solid ferromagnetic cylinder and place it in a conventional induction motor stator. Then, when the stator windings are connected to the network and a rotating magnetic field appears in the massive body of the rotor, so-called eddy currents (Foucault currents) will be induced, the direction of which is also determined by Lenz's law. When these currents interact with a magnetic field, a torque is created, under the influence of which a solid rotor begins to rotate in the direction of rotation of the magnetic field, like a conventional rotor with a winding. Such engines are called induction motors with massive rotor.
Note that eddy currents also occur, of course, in the core of a conventional winding rotor, but in this case they are harmful, since they cause additional heating of the rotor. Usually, they try to weaken their action, for which the rotor core is assembled (mixed) from separate sheets of electrical steel isolated from each other, thereby creating a large electrical resistance for eddy currents. In this case, the core is often referred to as a package.
Considered in this section general principles the work of AC and DC motors is physical basis work and engines for special purposes.
Electric motors of both general and special purposes are characterized by nominal data, which include the power on the motor shaft, voltage, current, speed, efficiency and some other quantities. The main nominal data are regulated state standards(GOST) on electric cars and indicated in the passport.
The nominal data of the engine corresponds to the normal thermal mode of its operation, in which the temperature of all parts of the engine does not exceed acceptable level. To ensure this mode, the engine is calculated accordingly and has a cooling (ventilation) system.
According to the method of cooling, they distinguish:
engines with natural cooling, in which there are no special devices for ventilation;
motors with internal and external self-ventilation, the cooling of which is carried out by a fan located on the motor shaft and ventilating, respectively, the internal cavity or outer surface engine;
motors with independent cooling, which are cooled by a separate fan ("rider"), which has its own drive.
The operation of the motors is also characterized by some other quantities that are not directly indicated in its passport - the rated torque corresponding to the rated data of the motor, and the starting torque and current, which correspond to the moment of starting (connecting to the network) of the motor. When analyzing the operation of a motor, the values of the starting torque and current are usually compared with the corresponding nominal values. The torque and current of the motor during start-up should not exceed certain permissible values determined by the conditions of motor heating and normal operation of its collector-brush assembly.
An electric motor is a device whose principle of operation is the conversion of electrical energy into mechanical energy. Such a transformation is used to launch all kinds of equipment, from the simplest work equipment to cars. However, with all the usefulness and productivity of such a transformation of energies, there is a small difference in this property. by-effect, which manifests itself in increased heat generation. That is why electric motors are equipped with additional equipment, which is able to cool it and allow it to work smoothly.
Any electric motor consists of two main elements, one of which is fixed, such an element is called a stator. The second element is movable, this part of the engine is called the rotor. The rotor of an electric motor can be made in two versions, namely, it can be short-circuited and with a winding. Although the latter type is quite rare today, since devices such as .
The principle of operation of the electric motor is based on the following stages of work. During inclusion in the network, the resulting magnetic field begins to rotate in the stator. It acts on the stator winding, in which an induction-type current arises. According to Ampere's law, the current begins to act on the rotor, which, under this action, begins its rotation. Directly, the rotor speed directly depends on what force of action the current arises, as well as on how many poles this occurs.
To date, the most common are engines that have a magnetoelectric type. There is another type of electric motors, which are called hysteresis, but they are not common. The first type of electric motors, the magnetoelectric type, can be subdivided into two more subtypes, namely DC motors and AC motors.
The first type of motors carries out its work from direct current, these types of electric motors are used when it becomes necessary to adjust the speeds. These adjustments are carried out by changing the voltage in the armature. However, there is now big choice all kinds of frequency converters, so such motors are used less and less.
AC motors, respectively, work by means of the action of current variable type. It also has its own classification, and the motors are divided into synchronous and asynchronous. Their main difference is the difference in the rotation of the necessary elements; in synchronous, the driving harmonic of the magnets moves at the same speed as the rotor. On the contrary, the current arises due to the difference in the speeds of movement of the magnetic elements and the rotor.
Thanks to their unique characteristics and the principles of operation of electric motors today are much more common than, say, internal combustion engines, since they have a number of advantages over them. So the efficiency of electric motors is very high, and can reach almost 98%. The motors are also different. high quality and a very long working life, they do not make a lot of noise, and practically do not vibrate during operation. The big advantage of this type of engine is that it does not need fuel and as a result does not emit any pollutants into the atmosphere. In addition, their use is much more economical than internal combustion engines.
An electric motor is an electrical device for converting electrical energy into mechanical energy. Today, electric motors are widely used in industry to drive various machines and mechanisms. IN household they are installed in washing machine, refrigerator, juicer, food processor, fans, electric shavers, etc. Electric motors set in motion devices and mechanisms connected to it.
In this article, I will talk about the most common types and principles of operation of AC electric motors, widely used in the garage, household or workshop.
The engine works based on the effect discovered by Michael Faraday in 1821. He made the discovery that when interacting electric current a continuous rotation can occur in the conductor and the magnet.
If in a uniform magnetic field place the frame in a vertical position and pass current through it, then an electromagnetic field will arise around the conductor, which will interact with the poles of the magnets. The frame will be repelled from one, and attracted to the other.
As a result, the frame will turn to a horizontal position, in which there will be zero effect of the magnetic field on the conductor. In order for the rotation to continue, you need to add another frame at an angle or change the direction of the current in the frame at the right time.
In the figure, this is done using two half-rings, to which the contact plates from the battery adjoin. As a result, after a half-turn is completed, the polarity changes and the rotation continues.
In modern electric motors instead of permanent magnets, inductors or electromagnets are used to create a magnetic field. If you disassemble any motor, you will see coiled coils of wire coated with insulating varnish. These turns are an electromagnet or, as they are also called, an excitation winding.
At home permanent magnets are used in battery-powered children's toys.
In other more powerful motors use only electromagnets or windings. The rotating part with them is called the rotor, and the fixed part is called the stator.
Today there are quite a few electric motors different designs and types. They can be divided by type of power supply:
According to the principle of work:
A synchronous motor rotates synchronously with the magnetic field that rotates it, while for an asynchronous motor, the rotor rotates more slowly than the rotating magnetic field in the stator.
The principle of operation and the device of an asynchronous electric motor
In an asynchronous package motor, stator windings are laid (for 380 volts there will be 3 of them), which create a rotating magnetic field. Their ends for connection are brought out to a special terminal block. The windings are cooled thanks to a fan mounted on the shaft at the end of the motor.
Rotor, which are one with the shaft, is made of metal rods that are closed to each other on both sides, which is why it is called short-circuited.
Thanks to this design, there is no need for frequent periodic maintenance and replacement of current-feeding brushes, reliability, durability and reliability are greatly increased.
Usually, main cause of failure asynchronous motor is the wear of the bearings in which the shaft rotates.
Principle of operation. In order for an asynchronous motor to work, it is necessary that the rotor rotates more slowly. electromagnetic field stator, as a result of which an EMF is induced (an electric current occurs) in the rotor. Here important condition, if the rotor rotated at the same speed as the magnetic field, then, according to the law of electromagnetic induction, no EMF would be induced in it and, therefore, there would be no rotation. But in reality, due to bearing friction or shaft load, the rotor will always turn slower.
The magnetic poles are constantly rotating in the motor windings, and the direction of the current in the rotor is constantly changing. At one point in time, for example, the direction of currents in the stator and rotor windings is shown schematically in the form of crosses (current flows from us) and dots (current to us). The rotating magnetic field is shown as a dotted line.
For example, How does it work a circular saw . She has the highest speed without load. But as soon as we start cutting the board, the rotation speed decreases and at the same time the rotor begins to rotate more slowly relative to the electromagnetic field and, according to the laws of electrical engineering, it begins to induce even more EMF values. The current consumed by the motor increases and it starts to work at full power. If the load on the shaft is so great that it stalls, then damage to the squirrel-cage rotor may occur due to the maximum value of the EMF induced in it. That is why it is important to select an engine of suitable power. If you take more, then energy costs will be unjustified.
Rotor speed depends on the number of poles. With 2 poles, the rotation speed will be equal to the rotation speed of the magnetic field, equal to a maximum of 3000 revolutions per second at a mains frequency of 50 Hz. To reduce the speed by half, it is necessary to increase the number of poles in the stator to four.
A significant disadvantage of asynchronous motors is that they are served by adjusting the speed of rotation of the shaft only by changing the frequency of the electric current. And so it is not possible to achieve a constant shaft speed.
This type of electric motor is used in everyday life where a constant rotation speed is required, the possibility of its adjustment, as well as if a rotation speed of more than 3000 rpm is required (this is the maximum for asynchronous).
Synchronous motors are installed in power tools, vacuum cleaners, washing machines, etc.
In the case of a synchronous AC motor windings are located (3 in the figure), which are also wound on the rotor or armature (1). Their conclusions are soldered to the sectors of the slip ring or collector (5), which are energized with the help of graphite brushes (4). Moreover, the conclusions are arranged so that the brushes always supply voltage to only one pair.
Most frequent breakdowns collector motors is:
Principle of operation. The torque in the electric motor is created as a result of the interaction between the armature current and the magnetic flux in the field winding. With a change in the direction of the alternating current, the direction of the magnetic flux will also change simultaneously in the body and armature, due to which the rotation will always be in the same direction.
An electric motor is a device that converts electrical energy into mechanical energy. Electric motors are widely used in almost all areas. Everyday life. Before considering the types of electric motors, we should briefly dwell on the principle of their operation. All action takes place according to Ampère's law, when a magnetic field is formed around the wire, where the electric current flows. As this wire rotates inside the magnet, each side of it will be attracted to the poles in turn. Thus, the wire loop will rotate. Electric motors are divided among themselves, depending on the applied current, which can be alternating or direct.
A feature of alternating current is the change of its direction a certain number of times within a second. As a rule, alternating current with a frequency of 50 hertz is used.
When connected, the current first begins to flow in one direction, and then its direction is reversed. Thus, the sides of the loop, receiving a push, are attracted in turn to different poles. That is, in fact, there is their ordered attraction and repulsion. Therefore, when changing direction, the wire loop will rotate around its axis. With these circular motions energy is converted from electrical to mechanical.
AC motors come in many designs and come in a wide variety of models. This allows them to be widely used not only in industry, but also in everyday life.
The first motors invented were still DC devices. Alternating current at that time was still unknown. Unlike alternating current, direct current always moves in the same direction. The rotation of the rotor stops after a rotation of 90 degrees. The direction of the magnetic field coincides with the direction of the electric current.
Therefore, a metal ring connected to a direct current source is cut into two parts and is called a ring switch. At the start of rotation, current flows through the first side of the commutator and through the wires. An electric current flowing through a wire loop creates a magnetic field in it. With further rotation of the loop, the commutator also rotates. After the ring passes through the empty space, it moves to another part of the commutator. Further, the effect of an alternating electric current occurs, due to which the rotation of the loop continues.
All DC motors are used in conjunction with AC devices in production and transport.
