The device of synchronous machines, methods of excitation. Operating principle

Structural scheme of the machine. Synchronous machines are performed with a fixed or rotating armature. High-power machines for the convenience of removing electrical energy from the stator or supplying it are performed with a fixed anchor (Fig. 1.2, but)

Since the excitation power is small compared to from power removed from the armature (0.3-3%), the supply of direct current to the excitation winding using two rings does not cause any particular difficulties. Synchronous machines of small power are performed both with a fixed and with a rotating armature.

Rice. 1.2 - Structural diagram of a synchronous machine

with fixed and rotating anchor:

1 - armature, 2 - armature winding, 3 - inductor poles,

4 - excitation winding, 5 - rings and brushes

Synchronous, machine with a rotating armature and a fixed inductor (Fig. 1.2, b) called reversed.

Rice. 1.3 - Rotors of synchronous salient pole(but) and implicit(6) machines:

1 - rotor core, 2 - excitation winding

Rotor design

Rotor design. In a machine with a fixed anchor, two rotor designs are used: salient pole - with pronounced poles (Fig. 1.3, but) and implicitly polar - with implicitly expressed poles (Fig. 1.3, b). A salient pole rotor is usually used in machines with four or more poles. The excitation winding is performed in this case in the form of cylindrical coils of rectangular cross section, which are placed on the cores of the poles and strengthened with the help of pole pieces. The rotor, pole cores and pole pieces are made of steel. Two- and four-pole machines of high power, operating at a rotor speed of 1500 and 3000 rpm, are usually made with a non-salient pole rotor. The use of a salient-pole rotor in them is impossible due to the conditions for ensuring the necessary mechanical strength of the fastening of the poles and the excitation winding. The excitation winding in such a machine is placed in the grooves of the rotor core, made of massive steel forging, and reinforced with non-magnetic wedges. The frontal parts of the winding, which are affected by significant centrifugal forces, are fastened with steel massive bandages. To obtain a distribution of magnetic induction close to sinusoidal, the excitation winding is placed in grooves occupying 2/3 of each pole division.

Rice. 1.4 - The device of the salient-pole machine:

1 - housing, 2 - stator core, 3 - stator winding, 4 - rotor,

5 - fan, 6 - stator winding leads, 7 - slip rings,

8 - brushes, 9 - exciter

On fig. 1-4 shows the device of a salient-pole synchronous machine. The stator core is assembled from insulated sheets of electrical steel and has a three-phase armature winding on it. The excitation winding is located on the rotor.

Pole pieces in salient pole machines are usually profiled so that the air gap between the pole piece and the stator is minimal under the middle of the pole and maximal at its edges, due to which the induction distribution curve in the air gap approaches a sinusoid.

In synchronous motors with a salient pole rotor, rods are placed in the pole pieces starting winding(Fig. 1-5), made of a material with increased resistivity (brass, etc.). The same winding (of the "squirrel cage" type), consisting of copper rods, is also used in synchronous generators; they call her sedative or damper winding, as it provides a rapid damping of the rotor oscillations that occur during transient operation of a synchronous machine. If the synchronous machine is made with massive poles, then eddy currents arise in these poles during start-up and transient conditions, the action of which is equivalent to the action of current in short-circuited windings. The attenuation of rotor oscillations during transient processes is provided in this case by eddy currents that close in the massive rotor.

Excitation of a synchronous machine

Excitation of a synchronous machine. Depending on the method of supplying the excitation winding, systems of independent excitation and self-excitation are distinguished. With independent excitation, a DC generator (exciter) mounted on the rotor shaft of a synchronous machine serves as a source for powering the excitation winding (Fig. 1.6, but), or a separate auxiliary generator driven by a synchronous or asynchronous motor.

With self-excitation, the excitation winding is powered from the armature winding through a controlled or uncontrolled rectifier - semiconductor or ionic (Fig. 1.6, b). The power required for excitation is small and amounts to 0.3-3% of the power of a synchronous machine.

In powerful generators, sometimes, in addition to the exciter, a sub-exciter is used - a small DC generator that serves to excite the main exciter. In this case, a synchronous generator together with a semiconductor rectifier can be used as the main exciter. At present, the supply of the excitation winding through a semiconductor rectifier assembled on diodes or on thyristors is increasingly used both in engines and generators of small and medium power, and in powerful turbo and hydro generators (thyristor excitation system). Excitation current control I c is carried out automatically by special excitation regulators, although in machines of small power, regulation is also used manually by a rheostat included in the excitation winding circuit.

Recently, in powerful synchronous generators, the so-called brushless excitation system has begun to be used (Fig. 8-6, in). With this system, a synchronous generator is used as an exciter, in which the armature winding is located on the rotor, and the rectifier is mounted directly on the shaft.

Rice. 1.5 - Placement of the starting winding in synchronous motors:

1 - rotor poles, 2 - short circuit rings, 3 - squirrel cage rods,

4 - pole pieces

The field winding of the exciter is powered by the subexciter through a voltage regulator. With this method of excitation, there are no sliding contacts in the supply circuit of the excitation winding of the generator, which significantly increases the reliability of the excitation system. If it is necessary to force the excitation of the generator, increase the voltage of the exciter and increase the output voltage of the rectifier.

The characteristics of the excitation system are determined by a combination of the properties of the field winding power supply and automatic control devices. Excitation systems must provide:

1) reliable power supply of the rotor winding of a synchronous machine in all modes, including in case of accidents;

2) stable regulation of the excitation current when the load changes within the nominal;

3) sufficient performance;

4) forcing excitation.

Excitation systems are classified depending on the power source-excitation winding into dependent (self-excited) and independent. W dependent - powered by the main or additional winding of the armature of the excited generator. Independent powered by other sources (from the plant's auxiliary buses, from an exciter or an auxiliary generator).

Among independent excitation systems, there are:

a) direct excitation systems, in which the exciter or auxiliary generator rotor is on the same shaft as the rotor
synchronous machine or interfaced with it by a speed reducer;

b) indirect excitation systems, in which the rotor of the exciter or auxiliary generator is driven by a synchronous or asynchronous motor specially installed for that purpose.

Until the 1960s, direct electrical excitation systems, in which the excitation winding of the synchronous machine is powered by a collector DC generator - the exciter (Fig. 24.26, a).

In accordance with GOST 533-76, GOST 5616-81 and GOST 609-75, turbo and hydro generators and synchronous compensators can only have the most reliable direct excitation system or self-excitation system. But electric machine excitation systems, according to switching conditions, cannot be used in turbogenerators with a capacity of 200 MW and higher, in which the excitation power exceeds 800-1000 kW.

V. is now becoming more common valve excitation systems. They are used for synchronous motors and small power generators, as well as for large turbogenerators, hydro generators and synchronous compensators, including for power limiting installations.

There are three main types of valve excitation systems.

1. Independent valve excitation system(Fig. 24.26, b) in which the excitation winding is powered by an auxiliary synchronous generator, the rotor of which is mounted on the main generator shaft. In the rectifier circuits, in this case, semiconductor valves (silicon diodes or thyristors) are used, assembled according to a three-phase bridge circuit. When regulating the excitation of the generator, both the control capabilities of the rectifiers and the possibility of changing the voltage of the auxiliary generator are used.

2. Brushless excitation system, which differs from an independent valve system (Fig. 24.26, b) by the fact that it has an inverted auxiliary synchronous generator, in which the alternating current winding 3 placed on the rotor. Rectifier 5, powered by this winding, is located on the main generator shaft. The advantage of this system is the absence of sliding contacts, which in powerful turbogenerators must be designed for thousands of amperes.

3 . Self-excitation system(Fig. 24.26, in), in which the field winding is powered from the main or additional armature winding. Rectification of alternating current is carried out using thyristors. Energy extraction is carried out with the help of transformers 9 And 7, connected respectively in parallel and in series with the stator winding. Transformer 7 allows for forcing excitation in case of close short circuits, when the voltage on the armature winding is significantly reduced. The self-excitation system has a higher reliability and lower cost compared to other systems due to the absence of an exciter or an auxiliary generator in it.

Important parameters of excitation systems are the nominal rate of rise of the excitation voltage, the nominal excitation voltage, the excitation forcing ratio.

Rated excitation voltage- voltage at the terminals of the excitation winding when it is supplied with the rated excitation current and the resistance of the winding, reduced to the calculated operating temperature.

Excitation forcing ratio- the ratio of the highest steady value of the excitation voltage to the rated excitation voltage.

A special device is provided in the excitation circuit, with the help of which it is possible to quickly reduce the excitation current to zero in an emergency ( extinguish the magnetic field). For example, in case of internal short circuits in the stator winding, the field is quenched using a field quenching machine, which closes the excitation winding to a special quenching resistor.

To keep the synchronous machine in synchronism with a decrease in the mains voltage during remote short circuits, they resort to forcing its excitation current. Forcing is carried out automatically by the relay protection of the machine. The efficiency of forcing is characterized by the multiplicity of excitation forcing.

Dmitry Levkin

Construction of a synchronous electric motor with excitation winding

A synchronous electric motor with an excitation winding, like any rotating one, consists of a rotor and a stator. The stator is the fixed part, the rotor is the rotating part. The stator usually has a standard three-phase winding, while the rotor is made with an excitation winding. The excitation winding is connected to slip rings to which power is supplied through the brushes.

Synchronous motor with excitation winding (brushes not shown)

Principle of operation

The constant speed of rotation of a synchronous motor is achieved due to the interaction between the constant and rotating magnetic field. The rotor of a synchronous motor creates a constant magnetic field, and the stator creates a rotating magnetic field.

The operation of a synchronous electric motor is based on the interaction of the rotating magnetic field of the stator and the constant magnetic field of the rotor

Stator: rotating magnetic field

A three-phase alternating voltage is applied to the windings of the stator coils. As a result, a rotating magnetic field is created, which rotates at a speed proportional to the frequency of the supply voltage. You can read more about how a three-phase supply voltage is formed in the article "".

Interaction between rotating (at the stator) and constant (at the rotor) magnetic fields

Rotor: permanent magnetic field

The rotor winding is excited by a direct current source through slip rings. The magnetic field created around the rotor excited by direct current is shown below. It is obvious that the rotor behaves like a permanent magnet, since it has the same magnetic field (alternatively, one can imagine that the rotor is made of permanent magnets). Consider the interaction of a rotor and a rotating magnetic field. Suppose you give the rotor initial rotation in the same direction as the rotating magnetic field. The opposite poles of the rotating magnetic field and the rotor will be attracted to each other and they will interlock with the help of magnetic forces. This means that the rotor will rotate at the same speed as the rotating magnetic field, i.e. the rotor will rotate at synchronous speed.

The magnetic fields of the rotor and stator coupled to each other

Synchronous speed

The speed at which the magnetic field rotates can be calculated from the following equation:

• where N s is the frequency of rotation of the magnetic field, rpm,
• f is the stator current frequency, Hz,
• p is the number of pairs of poles.

This means that the speed of a synchronous motor can be very accurately controlled by changing the frequency of the supply current. Therefore, these motors are suitable for high precision applications.

Direct start of a synchronous motor from the mains

Why are synchronous motors not started from the mains?

If the rotor has no initial rotation, the situation is different from that described above. The north pole of the rotor's magnetic field will be attracted to the south pole of the rotating magnetic field, and will begin to move in the same direction. But since the rotor has a certain moment of inertia, its starting speed will be very low. During this time, the south pole of the rotating magnetic field will be replaced by the north pole. Thus, repulsive forces will appear. As a result, the rotor will begin to rotate in the opposite direction. Thus the rotor will not be able to start.

Damper winding - direct start of a synchronous motor from the mains

In order to realize self-starting of a synchronous electric motor without a control system, a "squirrel cage" is placed between the tips of the rotor, which is also called a damper winding. When starting the electric motor, the rotor coils are not excited. Under the action of a rotating magnetic field, a current is induced in the turns of the "squirrel cage" and the rotor begins to rotate in the same way as they start.

When the rotor reaches its maximum speed, the rotor field winding is energized. As a result, as mentioned earlier, the poles of the rotor interlock with the poles of the rotating magnetic field and the rotor begins to rotate at a synchronous speed. When the rotor rotates at synchronous speed, the relative motion between the squirrel cage and the rotating magnetic field is zero. This means that there is no current in short-circuited turns, and therefore the "squirrel cage" does not affect the synchronous operation of the electric motor.

Getting out of sync

Synchronous motors have a constant speed independent of the load (provided that the load does not exceed the maximum allowable). If the load moment is greater than the moment created by the electric motor itself, then it will go out of synchronism and stop. Low supply voltage and low excitation voltage can also cause the motor to go out of sync.

Synchronous compensator

Synchronous motors can also be used to improve system power factor. When the sole purpose of using synchronous motors is to improve power factor they are called synchronous compensators. In this case, the motor shaft is not connected to a mechanical load and rotates freely.

Synchronous motors for industrial use receive electromagnetic excitation from an independent DC source. The following sources are used as such sources: DC generators (exciters), which can be located on the same shaft with a synchronous motor (Fig. 7.6.6) or driven by a separate motor (Fig. 7.6, i); thyristor controlled rectifiers that can be powered from an industrial network (Fig. 7.6, in), or from a special alternator located on the same shaft with a synchronous motor. In the latter case (Fig. 7.6, d), semiconductor rectifiers are located on the rotor of a synchronous machine (a system with rotating rectifiers), therefore, brushes and rings are not required to supply current to the excitation winding, i.e. synchronous machine becomes contactless.

During acceleration, when the motor is running in asynchronous mode, the exciter can be connected to the rotor winding with the exciter de-energized (scheme with a blindly connected exciter), and it can be disconnected from the excitation winding by the KM contactor (see diagrams in Fig. 7.1 and 7.6). In the latter case, the excitation winding is short-circuited or short-circuited. It is impossible to leave the ends of the excitation winding open during acceleration, since a significant slip EMF is induced in the winding at large slips.

When using a thyristor converter or rotary rectifiers as exciter, the field winding is short-circuited through the shunt thyristors during start-up.

Rice.but- from a separate motor-generator; 6 - from a generator located on the shaft of a synchronous motor; in- from thyristor exciter; d- from the built-in generator

Consider the circuit in Fig. 7.6, c. When starting the engine in asynchronous mode, the voltage of the thyristor converter UD equals zero. In the excitation winding, a variable slip emf is induced, under the action of which through the zener diodes VD auxiliary thyristors open VS, and the excitation winding closes on the discharge resistance R. When the motor reaches subsynchronous speed, the slip emf becomes low, the zener diodes turn off, and the thyristors VS turn off the discharge resistance, after which a direct current is supplied to the excitation winding from the converter UD.

In recent years, exciters built into the design of a synchronous machine have become widespread (see Fig. 7.6, d). The exciter consists of a synchronous generator G, the rotor of which is located on the shaft of the synchronous motor D, an uncontrolled rectifier, auxiliary thyristors VS and discharge resistances R2 And R3, also placed on the shaft of a synchronous motor. The excitation current is controlled by changing the excitation current of the generator G. Upon reaching the subsynchronous speed, the circuits that shunt the excitation winding open, and a direct current is supplied to the winding, after which the motor is drawn into synchronism, its speed reaches synchronous, and then it operates in synchronous mode.

Regulation of the motor excitation current during operation in synchronous mode is carried out, as a rule, by the excitation ACS. It performs two main functions. The first is to ensure stable operation in synchronous mode. When the load surges or when the supply voltage decreases, the excitation ACS forces (increases) the excitation current, thereby increasing the maximum motor torque in synchronous mode (see Fig. 7.4). The second is the implementation of automatic control of reactive power circulating in the stator circuit of the engine.

The block diagram of the excitation current is usually built double-circuit (Fig. 7.7). The internal excitation current circuit serves to stabilize the set excitation current. The excitation current regulator p () is taken proportional or proportional-integral. Ensuring that the specified f is maintained constant is achieved by generating an excitation current setting signal with positive feedback based on the value of the real f of the stator circuits:

If the excitation current corresponding to U B insufficient to obtain a given power factor at a given load, then the compounding feedback increases the excitation current. Increasing the coefficient increases the accuracy of maintaining the given f, but causes fluctuations in the stator current when the load is applied. To reduce the fluctuation of the stator current, the circuit provides flexible feedback on the effective value of the stator current. Flexible feedback is formed as a differentiating link with a filter.

The most common generator excitation system is with a DC generator located on the same axis as a synchronous generator (Fig. 8.8).

The DC generator usually operates in self-excitation mode with the excitation winding connected in parallel with the armature winding. Voltage from the DC generator terminals through slip rings K 1 And K 2 is applied to the excitation winding of the generator.

To excite high-power generators, a three-phase alternating current exciter and a three-phase rectifier are mounted (Fig. 8.9).

In this case, the three-phase exciter winding is located on the rotating part of the excited generator. A three-phase rectifier is mounted on the same part. It is enough just to power the anchor of the main generator. The exciter armature can be powered by an external DC source or by an additional DC exciter mounted on the same axle.

To excite a three-phase generator, the principle of self-excitation can be used (Fig. 8.10). The conditions for self-excitation of the generator are the same as for DC generators.

The direct excitation current is obtained from the excitation transformer, since in most cases the excitation voltage is less than the mains and rectifier voltage. An excitation resistor is used to control the excitation current. To maintain a constant generator voltage, excitation can be used in electronic installations for automatic control of the excitation current.

Conclusion

The main purpose of writing the manual was to present the material of the theory and practice of operating electromechanical devices in a simple accessible language without losing the information content of the content. The study of the physical foundations of the functioning of electrical machines is a solid basis for understanding the principles of construction of other electromechanical devices that are used in enterprises of various profiles.

The rapid development of new technologies poses a number of complex scientific and technological problems for production. Energy plays a key role in solving these problems. In the conditions of the scientific and technological revolution, the pace of development of the machine-building complex and, in particular, electrical engineering, largely determines the technical progress in the field of energy, the fuel industry, transport and communications, metallurgy, machine tool building and instrument making, construction, the agro-industrial complex, etc.

This tutorial outlines the fundamentals of the theory, design features and modes of operation of the main types of electrical machines used in industry. At the same time, modern trends in the development of these machines are noted, aimed at increasing their reliability, energy performance, and improving performance.

In general, at present, the following trends are observed in the development of domestic electrical engineering:

Improving the design of magnetic systems, windings and cooling systems in order to reduce the weight, overall dimensions of machines, energy losses in them; increase in unit power of machines, rotational speed and rated voltage, increase in reliability by improving the quality of winding insulation, eliminating, if possible, brush contacts and improving commutation in collector machines; creation of new circuits of electrical machines that combine an electromagnetic system with elements of semiconductor technology (diodes, thyristors, transistors) to increase reliability, improve performance and expand the range of regulation of output parameters (current, voltage, speed, etc.), creation of linear electric motors and reciprocating motion engines;

Development of more technological designs of machines of small and medium power and micromachines adapted for mass and serial production; improvement of methods for calculating electrical machines based on the use of computers, physical and mathematical modeling; widespread use of standardization for the main parameters of machines, their design elements, installation dimensions, cooling methods, and protection from environmental influences.

In solving the tasks set, the leading role belongs to the employees of branch research and design institutes. Scientists and teachers of higher educational institutions also provide significant assistance to workers in the electrical industry.

Electric machines used in automation and telemechanics schemes are very diverse in design, principle of operation, and in the functions they perform in various, sometimes very different automatic control, regulation and control schemes.

It is practically impossible to give a description of all the electrical machines used in one book, limited in volume by the curricula of universities. That is why the authors of this manual did not set themselves such a task, limiting themselves only to describing the device, the principle of operation, the fundamentals of the theory and the main characteristics of electrical machines that have received the most widespread use.

If you wish to become more deeply acquainted with the electrical machines presented in this tutorial, concisely, the reader can refer to the specialized literature.

Bibliography

1.Alekseev,A. E. Design of electrical machines / A. E. Alekseev. - M., 1958.

2.Armenian,E.V. Electrical micromachines / E. V. Armensky,G. B. Falk. - M., 1984.

3.Bertinov,A.I. Electrical Machines for Aviation Automation / A. I. Bertinov. - M., 1961.

4.Bruskin,D. E. Electrical Machines and Micromachines /
D. E. Bruskin,A. E. Zarokhovich,V. S. Khvostov. - M., 1981.

5.Booth,YES. Non-contact electrical machines / D. A. But. - M., 1985.

6.Vinogradov,N.V. Design of electrical machines / N. V. Vinogradov,F. A. Goryainov,P. S. Sergeev. - M., 1969.

7.Important,A.I. Electric cars / A. I. Important. - L .: Energy, 1969.

8.Vinokurov,V.A. Electric cars of railway transport / V. A. Vinokurov,D. A. Popov. - M., 1986.

9. woldek, A.I. Electric cars / A. I. Voldek. - L .: Energy, 1966.

10.Goldberg,O.D. Design of electrical machines /
O. D. Goldberg,Ya. S. Gurin,I. S. Sviridenko. - M., 1982.

11.Yermolin,N.P. Low Power Electric Machines / N. P. Ermolin.- M., 1975.

12.Ivanov-Smolensky,A.V. Electric cars / A. V. Ivanov-Smolensky. - M., 1980.

13.Katzman,MM. Electric cars / M. M. Katsman. - M., 1983.

14.Katzman,MM. Electrical machines automatic devices / M. M. Katsman,F. M. Yuferov. - M., 1979.

15.Kopylov,I.P. Electric cars / I. P. Kopylov. - M., 1986.

16.Kopylov,I.P. Electromechanical energy conversion / I. P. Kopylov. - M., 1973.

17.Kostenko,M.P. Electric cars. Part 1 / M. P. Kostenko,L. M. Piotrovsky. - L., 1973.

18.Kostenko,M.P. Electric cars. Part 1. - Ed. 2nd /
M. P. Kostenko,L. M. Piotrovsky.- L.: Energy, 1964.

19.Kostenko,M.P. Electric cars. Part 2. - Ed. 2nd /
M. P. Kostenko,L. M. Piotrovsky. - L.: Energy, 1965.

20. Petrov,G. N. Electric cars / G. N. PETROV - M., Gosenergoizdat, 1956. - Part I.

21.Petrov,G. N. Electric cars / G. N. Petrov. - M., 1963. - Part II; 1968. - Part III.

22. Special electrical machines / ed. A. I. Bertinova.- 1982.

23.Khrushchev,V.V. Electric machines of automation systems / V. V. Khrushchev. - L., 1985.

Preface. 3

Introduction. 4

Chapter 1. Basic physical laws of functioning
electrical machines. nine

Chapter 2. General questions of DC machines. 13

2.1. The principle of operation of DC machines. 13

2.2. Design of DC machines. 17

2.3. Armature windings of DC machines. eighteen

2.4. Equipotential connections of armature windings. 31

2.5. Methods for creating a magnetic field or methods of excitation
DC machines. 34

2.6. EMF of the armature winding of DC machines. 36

2.7. Mechanical torque on the shaft of a DC machine. 39

2.8. The magnetic field of a DC machine running
in idle mode. 41

2.9. The magnetic field of a loaded DC machine.
anchor reaction. 42

2.10. Switching of the armature winding of DC machines. 45

Chapter 3. DC motors. 49

3.1. The principle of operation of DC motors. 49

3.2. Basic equations of a DC motor. 51

3.3. Losses and efficiency of engines
direct current. 51

3.4. Characteristics of DC motors. 54

3.5. Starting DC motors. 65

3.6. Speed ​​control of DC motors. 71

Chapter 4. DC generators. 80

4.1. Classification of DC generators according to the method of excitation. 80

4.2. Energy diagram of DC generators. 81

4.3. The main characteristics of DC generators. 86

4.4. Characteristics of the generator with independent excitation.. 86

4.5. Working point of the loaded generator. 94

4.6. Characteristics of the generator with parallel excitation.. 95

4.7. Generators with serial excitation.. 100

4.8. DC generators with mixed excitation.. 101

4.9. Use of DC generators. 105

4.10. Parallel operation of generators. 106

Chapter 5. Transformers .. 109

5.1. The principle of operation of transformers. 110

5.2. Design of single-phase transformers. 112

5.3. Losses of electrical energy in the transformer and the efficiency of the transformer. 114

5.4. Transformer idle mode. 118

5.5. The operation of the transformer in load mode. 121

5.6. The reduced transformer and its equivalent circuit. 124

5.7. Experimental determination of transformer parameters. 129

5.8. Changing the output voltage of the transformer
when the load current changes. External characteristic
transformer. 132

5.9. External characteristics of transformers. 135

5.10. Three-phase transformers. The principle of operation of three-phase transformers 137

5.11. Schemes and groups for connecting three-phase windings
transformers. 141

5.12. Special transformers.. 145

5.13. Parallel operation of transformers. 150

Chapter 6. Asynchronous machines .. 154

6.1. Magnetic fields of asynchronous motors. rotating
a magnetic field. 154

6.2. Elliptical and pulsating magnetic fields. 160

6.3. The principle of operation of an asynchronous motor. 165

6.4. Construction of an asynchronous motor. 168

6.5. Windings of asynchronous machines. 170

6.6. Electromotive forces of the stator and rotor windings. 177

6.7. Magnetic flux of asynchronous machines. 178

6.8. Vector diagram of an induction motor. 181

6.9. Electrical equivalent circuit of an asynchronous motor. 184

6.10. Energy processes of an asynchronous machine.. 186

6.11. Energy diagram of an induction motor. 188

6.12. The general equation of the torque of an asynchronous machine.. 189

6.13. The equation of the mechanical characteristic of the asynchronous
engine. 191

6.14. Kloss formula. 194

6.15. Equivalent equivalent circuit of an asynchronous machine
with magnetizing circuit connected to mains terminals.. 196

6.16. Pie diagram of an asynchronous machine. Building a chart.. 198

6.17. Pie chart analysis.. 202

6.18. Starting three-phase asynchronous motors. 207

6.19. Starting motors with a phase rotor .. 207

6.20. Starting a squirrel-cage motor .. 210

6.21. Motors with special rotor winding and improved starting characteristics. 214

6.22. Ways to control the speed of a three-phase asynchronous motor 216

6.23. Performance characteristics of asynchronous motors. 222

6.24. The operation of an asynchronous motor in various modes. 226

6.25. The operation of an asynchronous machine with a phase rotor in the mode
three-phase voltage regulator. 227

6.26. Single-phase asynchronous motors. 228

6.27. Marking the conclusions of an asynchronous motor. 232

Chapter 7. Synchronous generators .. 234

7.1. The principle of operation of synchronous machines. 234

7.2. The design of the synchronous machine.. 237

7.3. Generator idle mode. 238

7.4. Armature reaction of a synchronous machine.. 240

7.5. Vector voltage diagrams of a three-phase synchronous generator 245

7.6. Change in voltage at the output of a synchronous generator. 249

7.7. Main characteristics of a synchronous generator. 253

7.8. Inclusion in the network of three-phase generators or parallel
operation of alternators. 257

7.9. Angular characteristics of synchronous generators. 261

7.10. Synchronization power and synchronization torque. 264

7.11. Influence of the excitation current on the mode of operation of the synchronous
generator. 264

7.12. Energy loss and efficiency
synchronous generator. 266

Chapter 8. Synchronous motors. 269

8.1. The principle of operation of synchronous motors. 269

8.2. Vector voltage diagram of a synchronous motor. 270

8.3. Power and mechanical torque of a synchronous motor. 271

8.4. V-shaped characteristics of synchronous motors. 272

8.5. Characteristics of a synchronous motor. 274

8.6. Starting methods for synchronous motors. 275

8.7. Synchronous compensators.. 277

8.8. Ways of excitation of synchronous machines. 277

Conclusion. 280

References.. 282

Educational edition

Goryachev Vladimir Yakovlevich

Jazz Nikolai Borisovich

Nikolaev Elena Vladimirovna

Electromechanics

Editor V. V. Chuvashova

Technical editor N. A. Vyalkova

Corrector N. A. Sidelnikova

Computer layout N. V. Ivanova

Put into production 07.12.09. Format 60x841/16.

Conv. oven l. 16.74. Uch.-ed. l. 19.98.

Circulation 100. Order No. 643. "C" 164.

_______________________________________________________

PSU publishing house

440026, Penza, Red, 40.