Most technological processes proceed with the release or absorption of heat. Therefore, metering and regulation is the most important task for automation services.

The following devices are mainly used in factories and ships: potentiometers with thermocouples(), balanced bridges with resistance thermometers and.

Electronic thermometers are widely used as temperature meters. You can get acquainted with contact and non-contact digital thermometers on the website http://mera-tek.ru/termometry/termometry-elektronnye. These devices mainly provide temperature measurement at technological installations due to the high measurement accuracy and high registration speed.

In electronic potentiometers, both indicating and recording, automatic stabilization of the current in the potentiometer circuit and continuous compensation of the thermocouple are used.

Connection of conductive cores- part of the technological process of connecting the cable. Multi-wire conductive cores with a cross-sectional area of ​​0.35 to 1.5 mm 2 are connected by soldering after twisting individual wires (Fig. 1). If they are restored with insulating tubes 3, then before twisting the wires, they must be put on the core and moved to the cut of the sheath 4.

Rice. 1. Connection of cores by twisting: 1 - conductive core; 2 - conductor insulation; 3 - insulating tube; 4 - cable sheath; 5 - tinned wires; 6 - soldered surface

Solid cores connect with an overlap, fastening before soldering with two bands of two or three turns of tinned copper wire 0.3 mm in diameter (Fig. 2). You can also use the special wago 222 415 terminals, which have become very popular today due to their ease of use and reliability of operation.

When installing electrical actuators, their housing must be grounded with a wire with a cross section of at least 4 mm 2 through the grounding screw. The place of connection of the grounding conductor is thoroughly cleaned, and after connection, a layer of CIATIM-201 grease is applied to it to protect it from corrosion. At the end of the installation, check the value

At power plants, several synchronous generators are usually installed, connected in parallel to work together (Fig.21.1). There are advantages to having multiple generators instead of a single total capacity, for the same reasons that have been outlined for the parallel operation of transformers (see § 2.2).

When connecting a synchronous generator to the network for parallel operation, the following conditions must be observed: EMF of the generator at the moment of connecting it to the network, it must be equal and opposite in phase to the voltage of the network (
), generator EMF frequency must be equal to the frequency of the alternating voltage in the network ; the order of the phases on the generator terminals must be the same as on the mains terminals.

Bringing the generator to a state that satisfies all the specified conditions is called synchronization. Failure to comply with any of the synchronization conditions leads to the appearance of large equalizing currents in the stator winding, an excessive value of which can cause an accident.

It is possible to connect the generator to the network with parallel operating generators either by means of precise synchronization, or by means of self-synchronization.

Precise synchronization method. The essence of this method is that, before turning on the generator to the network, it is brought into a state that satisfies all of the above conditions. The moment these conditions are met, that is, the moment of synchronization, is determined by a device called synchroscope. By design, synchroscopes are divided into arrow and lamp. Consider the process of synchronizing generators using a lamp synchroscope, which consists of three lamps 1, 2, 3, located at the vertices of an equilateral triangle.

When the lamps are switched on according to the "extinction" scheme (Fig. 21.2, a) the moment of synchronization corresponds to the simultaneous extinction of all lamps. Suppose that the star EMF of the generator
rotates at angular frequency exceeding the angular frequency

rotation mains voltage stars
. In this case, the voltage across the lamps is determined by the geometric sum +; +; +(fig.21.2, b).

Rice. 21.1. Turning on synchronous generators

for parallel work:

G 1 - G 4 - synchronous generators, PD 1 -PD 4 - drive motors

At the moment of coincidence of the vectors of the EMF star with the vectors of the voltage star, this sum reaches the highest value, while the lamps burn with the greatest glow (the voltage across the lamps is equal to twice the voltage of the network). At subsequent moments in time, the EMF star overtakes the voltage star, and the voltage across the lamps decreases. At the moment of synchronization, the vectors of EMF and voltages occupy a position at which, i.e.
= 0, and all three lamps go out simultaneously (Fig. 21.2, c). With a large difference in angular frequencies and lamps flash frequently. By changing the speed of the prime mover, equality is achieved
, ochem will indicate the extinction of the lamps for a long time. At this moment, the switch should be closed, after which the generator will be connected to the network.

Rice. 21.2. Lamp synchroscope

Self-Synchronization Method... The rotor of the unexcited generator is driven into rotation by the prime mover to a rotation frequency that differs from the synchronous one by no more than 2-5%, then the generator is connected to the network. In order to avoid overvoltages in the rotor winding at the moment the generator is connected to the network, it is closed to some active resistance. Since at the moment the generator is connected to the network, its EMF is zero (the generator is not excited), then under the action of the network voltage in the stator winding, a sharp current rush is observed that exceeds the rated value of the generator current. After switching on the stator winding, the excitation winding is connected to the network to a direct current source and the synchronous generator, under the influence of an electromagnetic moment acting on its rotor, is drawn into synchronism, i.e., the rotor speed becomes synchronous. In this case, the stator current decreases rapidly.

During self-synchronization, complex electromechanical transients occur in the generator, causing significant mechanical stress on the windings, bearings and the coupling connecting the generator to the turbine. The influence of these influences on generator reliability is taken into account when designing synchronous generators. The self-synchronization method (coarse synchronization) is usually used in generators with frequent switching on. This method is simple and easily automated.

The need for this device arises when connecting a generator in parallel to an alternating current network or to another generator. This process is called synchronization.

In order for the switching on to pass without harm to the generator, three conditions are achieved simultaneously:

• Voltage in the network and on the generator are the same in size;
• Frequency generation is equal to the frequency of the voltage in the network;
• Phase angle between the voltages of the same phases of the mains and the generator is zero.

Generator voltage before synchronization, set equal to the mains voltage using control voltmeters. The output voltage is regulated by changing the current in the rotor.

For fit generation frequency(fg) to the value of the frequency of the network (fc) change the speed of rotation of the generator. For this in power plants, the amount of steam (water) supplied to the turbine blades is regulated.

WITH phase angle much more difficult. It is impossible to achieve exact equality of the generation frequency with the mains frequency. But even if this condition is met, equality is rarely achieved. The process is further complicated by the fact that the speed of rotation of the turbine unit shaft is changed to adjust. With a multi-ton mass of industrial apparatus shafts, the change in speed occurs with inertia, which is difficult to take into account.

As a result, after equalizing the frequencies, there is still a difference, called slip frequency:

The consequence of the slip frequency is a constant cyclical change in the angle between the mains and generator voltages from zero to 360 degrees. The higher the slip frequency, the faster the angle changes, and vice versa.

To visually display the angle between the mains and generator voltages, you need synchroscope... The voltages of the same-named phases of the network and the generator are supplied to it. The zero position of the arrow on it occurs at an angle equal to zero, the opposite value at 180 degrees.

The synchroscope arrow constantly rotates during synchronization. In the direction of rotation, it is determined whether the frequency of generating the frequency in the network is greater or less. At the moment the arrow passes through the zero position, the generator is switched on to the network.

Turning on the generator at the moment when the arrow points to 180 degrees leads to the occurrence of currents through the stator winding, exceeding the rated short-circuit current... During the time the protection is in effect, this current will have time to destroy the stator winding. The generator will have to be sent for overhaul.

If the generator is connected to the network at smaller angles, but not equal to zero, a short-term current surge will occur through the stator winding. This is also an emergency mode of its operation. Damage to the winding will not occur, but the systematic asynchronous connection of the unit to the network will eventually lead to breakdown. So asynchronous activation is prohibited.

Column sync

For visual control of parameters when the generators are connected to the network, a synchronization column is installed on the main control panel of the power plants. Devices are placed on it:

• Voltmeter for monitoring the voltage in the network.
• Generator voltage control voltmeter.
• Network frequency counter.
• Generator frequency counter.
• Synchronoscope.

Sometimes a test lamp is additionally placed on the column, connected between one of the phases of the network and the generator. The lamp changes the brightness of the glow simultaneously with the movement of the synchroscope arrow. At the angle between the voltages equal to zero, it goes out, at 180 degrees - it burns in full brightness. In mobile power plants, such lamps are sometimes installed on all three phases together (or instead of) a synchroscope.

Since there are many generators at the stations, it is possible to connect them one by one to the synchronization column.

Automatic synchronizers

Since the synchronization process is difficult to control manually, it is carried out automatically. To do this, power plants install devices called autosynchronizers.

The regulation of the generator speed in manual mode is performed by keys that give an impulse to the regulating device. In thermal power plants, this is an electric motor of a steam valve at the turbine inlet. By briefly turning the key to the "More" or "Less" position, the operating personnel opens or closes the valve. This ensures the regulation of the turbine speed. The same operation is performed by an auto-synchronizer operating in automatic mode.

Like the synchroscope, it is connected to the voltage from the generator output and from the network. It constantly monitors their values ​​and issues an impulse to turn on only at the moment the conditions listed at the beginning of this article are met. But with one difference: the command to turn on the generator to the network is issued in advance, with the delay set when setting up the synchronizer.

What is it for? The fact is that the switch that connects the generator to the network is characterized by own turn-on time... It is small (tenths of a second), but this is enough for the synchronoscope needle to leave the zero position during the triggering time. Therefore, a time delay is added to the synchronizer settings, called the lead time. For each type of switch (oil, vacuum, SF6) it has a different meaning.

Autosynchronizer does not connect the generator to the network at a slip frequency of zero... The process of adjusting the speed of the turbine is so unstable that the speed can change at any time. Therefore, switching on occurs at a low slip frequency other than zero.

Synchronization process

The inclusion of generators in the network at power plants is as follows.

1. After the turbine unit reaches its rated speed, its control is transferred to the operating personnel of the Main Control Panel. After the transfer of control, the staff of the turbine shop does not interfere with its work.
2. Using the frequency meters on the synchronization column, the personnel equalizes the generation frequency with the mains frequency, changing the turbine rotation speed.
3. According to the voltmeters on the synchronization column, by changing the current in the rotor, the voltage on the generator stator is set equal to the mains voltage. This is done only after equalizing the frequencies, since the output voltage of the stator also changes with a change in frequency.
4. The speed of rotation of the turbine changes up or down by the amount required for the normal operation of the auto-synchronizer.
5. The autosynchronizer goes into operation. Analyzing the value of the slip frequency, it gives out pulses to change the speed of the turbine, achieving the required speed of its rotation.
6. Having adjusted the slip value, the auto-synchronizer automatically switches to the mode of measuring the angle between voltages and calculates the moment when to give an impulse to turn on, so that it occurs at its zero value. As soon as this moment is reached, the switch is closed.

The process differs in different power plants and when using different types of synchronizers. They, like relay protection devices, have gone through three stages of development.

To enable the generators to run in parallel, they must be synchronized. There are two fundamentally different methods of synchronization: the method of precise synchronization and the method of self-synchronization.

Precise synchronization method consists in the fact that the included generator is preliminarily brought into rotation and excited. At the moment of switching it on for parallel operation with a working generator, it is impossible to provide the following synchronization conditions:

1) the order of the phases of the switched-on generator must coincide with the order of the phases of the operating generator (or the network that the generator turns on);

2) the voltages of the switched-on and operating generators must be equal in value and coincide in phase; equality of voltages is achieved by changing the current in the excitation winding;

3) the frequency of the current of the switched-on generator must be equal to the frequency of the operating generator; this is achieved by changing the rotational speed of the generator being switched on.

If all these conditions are met, the switched-on generator can be connected to the working one with a switch or switch.

Interaction between rotating magnetic fields F c1, and F c2 stator windings of parallel operating generators and magnetic fields F p1 and F p2 rotor electromagnets are shown in Figure 10.4. Vectors F c1 and F c1 rotate synchronously with the angular frequency ω and are in phase at every moment in time. Vectors F p1 and F p2 also rotate synchronously with each other and with vectors F With... But the corners ψ 1 , and ψ 2 phase displacement of the magnetic field of the stator and rotor can vary within different limits depending on the load. If these angles are equal to each other, this means that both generators carry the same resistive load (if their power ratings are equal). In order for one of the generators to accept a large load, it is necessary to act on the speed controller of the prime mover of this generator, to increase the torque on its shaft.

Subsequent increase in angle ψ will indicate that the generator has taken additional load. So, angle ψ 2 (Figure 10.4, b) more than an angle ψ 1 , (Fig. 10.4, a), since this generator (Fig. 10.4, b) is loaded more.

In order for one of the generators to take over part of the reactive power, it is necessary to increase the excitation current of the generator. Simultaneously with the increase in the load of the newly switched on generator, it is necessary to reduce the load of the running generators, since otherwise the frequency will increase.

In order to prevent an increase in voltage with an increase in the excitation current of a newly turned on generator, it is necessary to reduce the excitation current of previously operated generators.

Accurate synchronization is achieved using a device specially designed for this - synchroscope ... To control the equality of voltages, two voltmeters are used, one of which measures the voltage of the operating generator, and the other, of the connected one. Frequency equality is established by two frequency meters.

At the end of the installation of a generator intended for parallel operation, before putting it into operation, check the order of the phases (Fig.10.5). Between the terminals of the generator (on the switch P 1 ) and the buses of the network, with which the generator will operate in parallel, include two series-connected electric lamps. Each lamp is designed for line phase voltage. Then the generator is turned on and the switch is turned on. R 2 (with disabled R 1 ).

If the voltage vectors of the mains and the generator are not in phase, and there is also a difference in the frequencies of the mains and the generator, but the phase sequence turned out to be the same, then all three pairs of lamps will go out and light up at the same time.

If the alternation of phases in the generator and the network is not the same, then the lighting and extinguishing of the lamps in different phases do not coincide in time. In this case, the two linear wires leaving the generator are interchanged (having previously stopped the generator) and the phase coincidence is again checked. Then the terminals of the generator are marked according to the phases of the network, and the lamps are removed.

At a power plant where generators are turned on for parallel operation, devices designed for synchronization are installed on special sync columns ... Some fine timing schemes are discussed below.

Scheme 1 ... Column sync SC (fig.10.6) consists of two parallel circuits: one is connected in series with two lamps L , and in the other - a voltmeter V 0 and lamp L ... From each of the generators to the synchronization column, one wire goes from the phases of the same name. The synchronization circuits are closed along the neutral wire to the phase windings of the generator. Sockets 1, 2, 3 are mounted between the wires from the phases of the generators and the synchronization device.

Suppose that generator No. 1 is synchronized with the network. It is put into operation and, changing the rotational speed of the prime mover and the excitation current of the generator, is set according to the frequency meter Hz and voltmeter V frequency and voltage equal to the mains. After that, contacts 1 and 3 are closed with two plugs. Continuing to change the rotational speed of the switched-on generator within small limits and the excitation current, synchronism is achieved. Its onset is recorded by the extinction of the lamps. L and zero voltmeter reading V 0 ... When the voltmeter needle approaches zero, turn on the switch R 1 ... The generator is synchronized. The sync column is turned off immediately (turn off pins 1 and 3). Leaving the plugs in the sockets is unacceptable, because when the generators are turned off, the mains voltage will appear on their terminals, which will pose a danger to the service personnel.

In the considered circuit, you can do without a zero voltmeter. However, in this case, the accuracy of the method is significantly reduced, since the lamps give a visible glow only at a voltage of 25 ... 30% of the nominal and it is difficult to catch the moment of the actual coincidence of the voltage vectors. Lamps connected in parallel with the voltmeter circuit monitor the health of this circuit. Two consecutively include because at some moments the circuit may be under double phase voltage.

If high-voltage generators are synchronized according to this scheme, then the synchronization column is switched on through voltage transformers.

Scheme 2 ... Figure 10.7, a shows a diagram of switching on a lamp synchroscope. Lamps 1 connected to the same phase, and the lamps 2 and 3 connected to different phases. With lamp sync 1 will go out, and lamps 2 and 3 will be at full incandescence. At different frequencies of rotation of the generators, lamps 1, 2, 3, located in a circle (Fig. 10.7, b), light up and go out at the same time, creating the impression of the so-called rotation of light. By the direction of rotation, one can judge whether it is necessary to increase (B) or decrease (M) the rotational speed of the generator being switched on.

The generator according to this scheme is switched on for parallel operation at the moment when the rotation of the light spot has stopped.

The methods of accurate synchronization discussed above are relatively complex, and complex and expensive equipment is required to automate the processes of accurate synchronization. Therefore, in practice, it is widely used self-synchronization method , which is as follows.

An unexcited generator, in which the magnetic field is extinguished by a field suppression resistance specially included in the excitation circuit of the exciter R gp(Figure 10.8), accelerate the prime mover to a speed close to the nominal. When sliding about 2 ... 3%, the generator is switched on to the mains with a circuit breaker R... At the same time, excitation is supplied by shunting the field quenching resistance with block contacts Bl... The generator is then gradually pulled into synchronism.

At the moment the generator is connected to the network for parallel operation, short-term current surges occur, which are the result of connecting an unexcited generator to the network. However, these shocks do not interfere with the normal operation of previously operated generators and consumers.

This method of self-synchronization is considered basic and mandatory for all multi-unit rural power plants.

The method of exact synchronization is used only in cases where, due to the heavy workload of previously working generators, the self-synchronization method cannot be applied.

Manual self-synchronization are used only when the generators are equipped with a cut-off switch (at low-power stations) or switches without remote control. In order to judge the frequency difference, turn on, as shown in Figure 10.8, a lamp L with a voltage of 6 ... 36 V (depending on the value of the residual voltage of the generator). The lamp has a noticeable glow with a frequency difference of at least 2 Hz. However, the most perfect way to measure the frequency difference is to turn on special relays such as HDI(induction frequency difference relays).

The order of operations is as follows. The generator is accelerated by the prime mover with the switch off R and open block contacts Bl... Resistance is included in the exciter field winding circuit R gp zero blanking. When the starting generator reaches a speed close to synchronous speed, the light L goes out. At the same time, the switch is turned on R, block contacts are closed Bl and the field quenching resistance is shunted R gp... Normal excitation is restored, the generator is pulled into synchronism.

At semi-automatic self-synchronization the units are started by manual action on the control of the prime mover, and the generator is switched on to the network and the excitation is applied automatically.

Automatic self-synchronization assumes full automation of the processes of starting the unit, connecting generators to the network and supplying excitation.

It must be remembered that the shunt rheostat R in the excitation circuit, the exciter must be installed so that when the excitation winding is bridged at the generator terminals during no-load operation, the voltage is increased to the nominal value equal to the operating voltage on the power plant buses.

It so happens that it becomes necessary to connect a second generator for parallel operation. For example, in ship power systems, two or more generators are installed to increase survivability. The total power of the generators is always slightly higher than the total power of all consumers. Installation of several generators increases the survivability and efficiency of the installation, makes it possible to carry out scheduled inspections and repairs of generators, taking them out of action one by one.

Marine generators can work separately, without electrical connection to each other, or together, in parallel connection. Distinguish between short-term and long-term parallel operation of generators. Short-term parallel operation is intended for smooth transfer of the load from one generator to another, followed by disconnection of the first generator or their separate operation. Cooperative parallel operation of generators has several advantages:

1) transfer of the load from one generator to another is carried out smoothly, without interruption of power supply;

2) uninterrupted power supply to consumers is ensured in the event of failure of one of the generators;

3) higher power quality is ensured (less voltage fluctuations);

4) the possibility of alternating technical inspections and repairs of generators.

The disadvantages of parallel operation of generators include:

1) complication of the circuit for switching on and controlling generators;

2) a significant increase in current during short circuits in the electric power system.

Consider the parallel operation of DC generators of parallel and mixed excitation, since generators of series excitation in this mode are usually not used, and there are practically no differences in parallel operation of generators of parallel and independent excitation.

Fig. 1 - Scheme of parallel operation of parallel excitation generators

Parallel operation of generators of parallel excitation.

A schematic diagram of the parallel operation of generators is shown in Fig. 1. Suppose that the first generator G 1 is connected to the buses and operates with a certain load, creating a voltage U on the buses. The generator G 2, which is idling, needs to be switched on so that the mode of the first generator G 1 does not change, and the current of the generator G 2 when turned on was equal to zero.

Hence it follows that the EMF of the generators should be directed oppositely to each other. Consequently, the conditions for switching on generators of parallel excitation for parallel operation can be formulated as follows:

1. The polarity of the terminals of the operating and connected generator must be the same.

2. EMF of the connected generator must be equal to the voltage of the network to which it is connected.

When these conditions are met, the current of the generator G 2 will be equal to zero, and the mode of the generator G 1 will not change, since

If you turn on the generator G 2 with the wrong polarity, then in a closed circuit formed by the armatures of both generators and the buses, their EMF will add up, and since the resistance of this circuit is very small, a very large current arises, which can lead to an accident of the generators.

Translation and load balancing. After connecting the generator G 2 to the network, you can take the load on it. For two generators operating in parallel, the equilibrium equations for the armature circuit voltages can be represented as

whence the ratios for the load currents are obtained

It can be seen from the system of equations that in order to accept the load on the generators, it is necessary to increase the EMF, which can be changed either by changing the number of revolutions of the generator, or by changing the excitation current. Typically, the rotational speed of the generators is kept constant by an automatic speed controller (APC) and in practice the EMF of the generators is controlled by varying the excitation current.

To accept the load on the generator G 2, you need to increase the current I in 2 by reducing the resistance r in 2 in the excitation circuit. EMF E a 2 becomes greater than the voltage U, as a result of which a current I 2 arises in the armature of the generator G 2. If the load current does not change, then with the appearance of the current I 2, the current I 1 decreases. If E a 1 is not changed at the same time, then E a 1 -I 1 r a 1 becomes larger and the voltage on the tires begins to rise. Therefore, to maintain U = const, simultaneously with an increase in E a 2, it is necessary to decrease E a 1 by decreasing the excitation current I in 1 in the excitation circuit of the generator G 1. Thus, you can transfer part or all of the load from the G 1 generator to the G 2 generator. It should be noted that when the load is transferred, the currents of the generators change, and therefore, their powers also change. In this case, the balance of the power of the generators and their prime movers is disturbed, as a result of which the rotational speeds of the generators change. To maintain the number of revolutions constant, APCs are included in the work, which change the supply of fuel, steam, etc. into the prime mover and restore the previous speed.

Rice. 2 - External characteristics of generators

As a rule, machines of equal power, the external characteristics of which are the same, are selected as generators for parallel operation. Then it is possible to load the generators evenly with the same excitation current. If the external characteristics do not match, then the generators in parallel operation are loaded with different currents. Figure 2 shows the external characteristics of two generators with different slopes. Suppose that both generators are connected in parallel and operate at no load with a voltage U 0. When the rated load is turned on on them equal to 2I n, the rated voltage U n is set on the buses.

According to external characteristics, this voltage corresponds to the load currents of the generators I 1 and I 2, and I 1 + I 2 = 2I n. As you can see, a generator with a "softer" characteristic (1) turns out to be underloaded, and with a "harder" characteristic (2) it is overloaded. In this case, for a uniform load of both generators, it is necessary to increase the excitation current of the first generator and decrease it at the second generator until the currents I 1 and I 2 become equal.

If the generators have different powers and are intended for parallel operation, then for proportional distribution of the load according to their powers without regulation of the excitation current, it is necessary that their relative characteristics coincide. In this case, the load will be distributed in proportion to the rated power of the generators.

Features of parallel operation of generators of mixed excitation. A schematic diagram of the inclusion of mixed-excitation generators in parallel operation is shown in Fig. 3.

Rice. 3 - Scheme of parallel operation of mixed excitation generators

Its distinctive feature is that points (I) and (2), in which successive field windings are connected to the armature terminals of the same name, are interconnected by an equalizing wire.

Equalizing wire allows for stable parallel operation of generators. To understand the need for an equalizing wire, consider the parallel operation of mixed-excitation generators without an equalizing wire. Suppose that two generators of the same power, with the same rotational speed, the same internal resistance r a 1 = r a 2 are operating, the loads, EMF and their magnetic fluxes are also equal.

If for some reason the speed of one, for example, the first generator, increases, then this will cause an increase in its EMF E a 1, and hence an increase in the load current for this generator. Due to the presence of a series winding, an increase in the load entails an increase in the resulting magnetic flux of this generator, which leads to an even greater increase in the EMF, and therefore the current, etc. As a result, the load of this generator will increase, and the load of the second generator will decrease, up to its transition to the motor mode, which is dangerous for both generators.

In the future, an excessive increase in the load on the first generator causes a decrease in its rotational speed, and hence the EMF. The load starts to transfer to the second generator, i.e. its turnover will tend to increase. Thus, an oscillatory process of transfer of the load from one generator to another occurs and the parallel operation turns out to be unstable.

In the presence of an equalizing wire 1-2 (Fig. 3), the series windings are connected in parallel. Consequently, their currents are always in the same ratio, determined by the resistances of these windings.

If now for some reason the EMF E a1 of the generator Г 1 becomes more than the EMF E a 2 of the generator Г 2, then an equalizing current arises in the circuit between the armatures, the value of which is determined by the expression

Thus, with an increase in the EMF, and therefore the current in the series winding of one generator, the current in the series winding of the other generator will also increase in the same ratio. In accordance with this, the EMF and load currents of both generators will simultaneously increase and the oscillatory process will not occur. This equality of currents in series windings will be maintained at any load. If generators of different power operate in parallel, then the resistances of their series windings will not be equal, therefore, the currents in these windings will be distributed inversely proportional to their resistances. However, in any case, a change in the current in one generator will lead to a change in the current in the other, and the oscillatory process will not occur. Under these conditions, the parallel operation of mixed-excitation generators becomes quite stable.

Reception and distribution of the load in mixed-excitation generators is carried out as in parallel-excitation generators by changing the current in the parallel excitation windings.