Car generators characteristics and generator circuit. Auto generator. The device and how it works. Photo gallery “Main generator malfunctions”

In hybrid vehicles, the generator functions as a starter generator and is used in some other stop-start systems.

By design, car generators can be compact or traditional. They differ mainly only in the fan layout, housing design, rectifier elements and drive pulley. Almost any generator consists of: a rotor, a stator, a housing, a voltage regulator unit and a rectifier and brush assembly.

1 – clamping bushing, 2 – bushing, 3 – buffer bushing, 4 – back cover, 5 – rectifier unit fastening screw, 6 – rectifier unit, 7 – valve (rectifier diode), 8 – rear bearing, 9 – slip rings, 10 – rotor shaft, 11 – brushes, 12 – terminal “30” 13 – brush holder, 14 – terminal “67”, 15 – neutral wire plug, 16 – generator mounting pin, 17 – fan impeller, 18 – pulley, 19 – plates, 20 – ring, 21 – front bearing, 22 – rotor winding, 23 – rotor, 24 – stator winding, 25 – stator, 26 – front cover

For VAZ 2110:

1 – casing, 2 – terminal “B+” for connecting consumers? 3 – noise suppression capacitance 2.2 μF, 4 – common terminal of additional rectifiers (connected to terminal “D+” of the voltage regulator unit), 5 – holder of positive rectifier diodes, 6 – holder of negative diodes, 7 – stator winding terminals, 8 – regulator unit voltage, 9 – brush holder, 10 – back cover, 11 – front cover, 12 – stator core, 13 – stator winding, 14 – spacer ring, 15 – washer, 16 – cone washer, 17 – pulley, 18 – nut, 19 – rotor shaft, 20 – front rotor shaft bearing, 21 – beak-shaped rotor pole pieces, 22 – rotor winding, 23 – bushing, 24 – tension screw, 25 – rear rotor bearing, 26 – bearing bushing, 27 – slip rings, 28 – negative diode, 29 – positive diode, 30 – additional diode, 31 – terminal “D” (common terminal of additional diodes)

1 – battery; 2.3 – negative and additional diode; 4 – generator; 5 – positive diode; 6 – stator winding; 7 – voltage regulator; 8 – rotor winding; 9 – capacity for suppressing radio interference; 10 – mounting block; 11 – control lamp battery charge indicator; 12 – voltage meter voltmeter; 13,14 – relay and ignition switch;

For the dashboard of VAZ 2107

1 - battery; 2 - negative diode; 3 - additional diode; 4 - generator; 5 - positive diode; 6 - stator winding; 7 - voltage regulator; 8 - rotor winding; 9 - radio interference suppression capacity; 10 - mounting block; 11 - battery charge indicator lamp in the instrument cluster; 12 - voltmeter; 13 - ignition relay; 14 - ignition switch.

Connection diagram of the G-222 generator system

For VAZ 2105 car

1 – generator; 2 and 3 – negative and positive diode; 4 – stator winding; 5 – voltage regulator; 6 – rotor winding; 7 – capacity for suppressing radio interference; 8 – battery; 9 – battery charge warning lamp relay; 10 – mounting block; 11 – battery charge indicator lamp in the instrument cluster; 12 – voltmeter; 13 – ignition relay; 14 – ignition switch

For VAZ 2107 car

1 - generator;
2 - negative diode;
3 - positive diode;
4 - stator winding;
5 – voltage regulator;
6 – rotor winding;
7 – capacitor for suppressing radio interference;
8 - battery;
9 - battery charge warning lamp relay;
10 - mounting block;
11 - battery charge indicator lamp in the instrument cluster;
12 - voltmeter;
13 - ignition relay;
14 - ignition switch

Generator Basics

Rotor - creates a rotating magnetic field; for this purpose, there is an excitation winding on the shaft. It is located in two halves of the pole, each of which has six projections - they are called beaks. There are also two slip rings on the shaft, and it is through them that the field winding is powered. Rings are usually copper, but sometimes steel and brass are found. The leads of the excitation winding are connected to the rings.

The rotor shaft has one or two fan impellers and a driven driven pulley is attached. Two maintenance-free ball bearings form the rotor bearing unit. On the slip ring side of the shaft there is often a roller bearing.

The stator is used to generate alternating current; it consists of a metal core and a winding; the core is assembled from steel plates and has thirty-six slots for winding the windings; three windings are located in the slots, forming a three-phase connection. There are two methods of laying windings in the stator slots - the wave method and the loop method. The windings are connected to each other according to a star and delta circuit.

The vast majority of the generator's structural components are located in the housing. The case consists of two aluminum covers - front and back. The front is located on the drive pulley side, the rear on the slip ring side. The covers are bolted together. There are ventilation holes and fastening tabs on the surface of the covers. Depending on the number of legs, a single-leg or two-leg generator mount is distinguished.

The brush assembly is designed to ensure the transfer of exciting current to the slip rings. The unit consists of 2 graphite brushes and pressure springs, as well as a brush holder. Usually the brush holder is located with the voltage regulator in one module.

The rectifier unit is designed to convert the sinusoidal voltage generated by the generator into direct voltage for the vehicle's on-board network. The module contains 6 power semiconductor diodes, i.e. for each phase there are two rectifiers, one for the “positive” and the other for the “negative” terminal.

On most modern generators, the excitation winding is connected through a separate contact group consisting of two diodes. These diodes prevent battery discharge current from flowing through the winding when the engine is not running. If the windings are connected in a star, two additional power diodes are located at the zero terminal, providing an increase in generator power up to 15%. The rectifier unit is connected to the circuit using special contact pads using soldering, welding, or screw connections.

Voltage regulator - necessary to maintain the voltage from the generator output within the specified parameters. voltage regulators. It comes in hybrid and integral versions.

Voltage stabilization is carried out when the engine crankshaft speed changes. The voltage regulator controls the repetition rate and duration of the pulses. In addition, it changes the voltage to charge the battery with thermal compensation depending on the ambient temperature. The higher the temperature, the lower the voltage supplied to the battery.

Using a belt drive, the rotor rotates at a speed two to three times higher than the crankshaft speed. Depending on the design of the generator, a poly-V or V-belt is used.

There is also an inductor generator, that is, brushless. It consists of a rotor made of a series of compressed thin plates of transformer iron. The stator has an excitation winding. By changing the magnetic conductivity of the air gap between the rotor and stator.

If we turn the key in the car ignition switch, current flows to the excitation winding through the brush assembly and slip rings. It is created in the winding. The generator rotor begins to move along with the rotation of the crankshaft. The stator windings are penetrated by the magnetic field of the rotor. An alternating voltage appears at the terminals of the stator windings. When a given rotation speed is reached, the exciting winding is powered from the generator, that is, the generator is in self-excitation mode.

The alternating voltage is rectified into direct voltage. In this state, the generator generates the required current to charge the power supply to consumers and the battery. The voltage regulator is connected to operation when the load and shaft speed change. The switching time of the excitation winding decreases as the load decreases and the generator speed increases. The time increases with increasing load and decreasing rotation speed. When the confirmation current exceeds the capabilities of the generator, the battery begins to work. There is a warning lamp on the front instrument panel that displays the status of the generator.

After driving the first 2000 km and every subsequent 15,000-20,000 km, it is necessary to check the condition and tension of the generator drive V-belt. To do this, press firmly with your thumb on the belt approximately in the middle. At the same time, it should not bend by more than 5 mm, and if new, then no more than 2 mm. If the deflection distance is less than the V-belt must be tightened or replaced.

To remove the belt, some car models require you to loosen the retaining screws, then use a pry bar or a heavy-duty screwdriver to move the alternator toward the engine and remove the belt. In car models with a tension roller, press the roller and, using the union head, loosen the tension and remove the belt.

To increase the belt tension, you need to loosen the fixing screws, use a screwdriver to slightly turn the generator away from the engine and tighten the screw again. In models with a tension roller, the latter independently regulates the belt tension.

When checking the V- or V-ribbed belt, make sure that the latter is not frayed and there are no cracks or breaks. If they are present, the belt needs to be replaced with a new one. If the engine is equipped with a double V-belt, the pair must be replaced together.

Generator faults. If a fairly loud, metallic noise appears, you need to check whether the pulley nuts are loose. If they are not the cause, the bearings may be damaged or an inter-screw short to ground may occur.

When connecting the battery, check that the polarity pins are connected correctly. In addition, the battery must not be disconnected from the on-board network when the engine is on and consumers are disconnected. Therefore, during any maintenance of the generator, it is necessary to check the serviceability of the battery charging circuit.

Do not allow the wires to come into contact with the voltage regulator housing. It is best to place them at a distance of 3-5 cm. Because the regulator can get very hot during operation, and the insulation of the wires can be damaged. The regulator cover should always be pressed very tightly against the body, and the gasket between the cover and the body should perfectly isolate the space under the cover.

Replacing generator brushes. The generator brushes must be checked after 50,000-60,000 km. To do this, you do not need to dismantle the generator, but simply:
Disconnect the negative cable from the battery, then unscrew the voltage regulator. If worn brushes protrude less than 5 mm from the brush holder, they must be replaced with new ones. Before installing the regulator with a new brush holder, it is necessary to clean the brush holder socket from accumulated carbon dust. To replace the brushes, unsolder the connecting wires, and if necessary, clean the contact surface and check the contact force of the contact springs.

After installing new brushes, check that they move freely in the holder. Then lightly attach the voltage regulator with the locking screw, and with pressure, but very carefully, set it to its final position and tighten it tightly. Do not forget to connect the ground cable to the battery after completing the process of replacing the generator brushes.

Sometimes in a new car the warning light on the dashboard may erroneously indicate "no battery charge". This happens because the brushes of the new generator have not yet had time to grind in.

The main source of electrical energy in any vehicle is the generator. Thanks to this unit, all electrical equipment of the car is powered, so it should always be operational. What is the generator connection diagram, what is its structure and principle of operation, and how to diagnose the unit? We will talk about this below.

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Design and principle of operation

As you know, the main purpose of a generator device is to convert mechanical energy into electrical energy. Thanks to this, the unit restores the battery capacity and also allows you to power everything. The generator device is located in the front of the power unit and is driven by the crankshaft.

More details about the main elements and principle of operation:

1. Rotary mechanism. This element is a shaft with an installed field winding. Both halves of a given winding are located in opposite pole halves of the assembly. The rotor mechanism is driven by a belt drive.
2. Slip rings are used to power the winding.
3. Stator mechanism - consists of a winding and a core. This element is designed to generate alternating current. The current generated by the mechanism is fed through the rings further along the electrical circuit.
4. In order for the generated excitation current to successfully reach the rings, brushes are used. These elements, as practice shows, often fail due to wear and tear.
5. Rectifier block. This component is designed to convert AC voltage. Structurally, this device consists of plates with installed diode elements. Depending on the pinout of the unit, the connection diagram for a car generator device may include a separate pair of winding diodes. In this case, voltage will not be able to pass through the battery when the engine is turned off.
6. Regulator relay. This element is designed to maintain a certain voltage level in the on-board network within normal limits. The regulator relay directly affects the frequency as well as the duration of the current signals. The regulator itself structurally includes controllers, as well as executive components. Their purpose is to determine the time during which the winding must be connected to the network. If the regulator relay for some reason fails, stabilization of the incoming voltage to the battery is lost.
7. The body of the device in which the main parts and components of the unit are located. The body itself is usually made of aluminum, so its weight is relatively light. The installation housing allows heat to be quickly dissipated, as a result of which the temperature does not reach a critical level. Also, the case is non-magnetic (the author of the video about the operating principle of the device is Mikhail Nesterov).

Checking a faulty generator

Let's consider the main malfunctions typical of automobile generator sets:

1. Open circuit, short circuit and other damage. To diagnose such a malfunction, you need to check the number of amperes, as well as the voltage level at the output of the device. In accordance with the data obtained, a solution to this problem is selected.
2. Often our compatriots are faced with such a problem as wear of graphite brushes, voltage regulator, and diode bridge. All worn out and failed elements can be repaired, but usually they are replaced. Separately, it should be said about the regulator - as mentioned above, it ensures optimal battery charge in accordance with the temperature in the engine compartment. Thus, the device automatically detects the number of volts for the battery under current conditions.
   Depending on the model of the generating set, a regulator with manual switching may be used in accordance with the time of year; in this case, sub-zero temperatures will not be harmful to the device. A broken relay can be indicated by unstable voltage in the system - for example, dim headlights that become brighter when you press the gas pedal.
3. Bearing failure. Failure of these elements can be indicated by increased noise, but the same sign also indicates insufficient lubrication.
4. Shui and howl. If such symptoms occur, the separator elements, raceways, and slip rings should be checked for rotation. Also, such a symptom may indicate a possible interturn short circuit in the windings of the stator mechanism or traction relay. In principle, when third-party sounds appear, you should also diagnose the state of the contacts.
5. The temperature of a working generator set can be up to 90 degrees, but if there is obvious overheating, the diode bridge should be diagnosed. You also need to make sure that there are not many additional devices and devices connected to the vehicle’s on-board network. When the temperature rises critically, the insulation winding of the stator mechanism will first darken; moreover, it may melt.
6. Worn generator set belt. If the alternator belt wears out and breaks, this will lead to incorrect operation of the unit as a whole, that is, all energy consumers in the car will be powered by the battery. If the belt breaks, the generator stops functioning, so the driver only has time to get to the nearest service station or garage to fix the problem. Voltage surges in the vehicle’s on-board network can indicate wear and tear.
   It is necessary to check the integrity of the strap and pay attention to its condition - cracks and other types of damage to the strap are not allowed. If they are present, then you need to understand that the belt will have to be changed soon.

Photo gallery “Main generator malfunctions”

Failure of the unit can also be indicated by too little battery charge or lack of voltage at its terminals. Also a sign of a device malfunction is the incorrect functioning of the display and equipment.

Possible ways to connect a node

How to install and how to connect the unit? In general, the connection diagram of the unit is similar for all passenger vehicles. Minor differences are related to the quality of manufacture of the unit, its power, as well as the location of components in the engine compartment. All vehicles are equipped with alternating current generators equipped with a voltage regulator.

Conclusion

The generator itself is a rather complex unit in design and principle of operation, the operation of which largely determines the performance of the car as a whole. Due to the fact that the unit powers all electrical equipment in the car, it is considered the main element in the vehicle’s on-board network. When the first signs of a malfunction appear in its operation, you should diagnose and troubleshoot problems as quickly as possible, since this can lead to serious consequences. You can entrust the repair to specialists or do it yourself - our website contains many articles on this topic.

The most basic generator function – battery charge battery and power supply for engine electrical equipment.

Therefore, let's take a closer look generator circuit, how to connect it correctly, and also give some tips on how to check it yourself.

Generator- a mechanism that converts mechanical energy into electrical energy. The generator has a shaft on which a pulley is mounted, through which it receives rotation from the engine crankshaft.

A car generator is used to power electrical consumers, such as the ignition system, on-board computer, car lighting, diagnostic system, and it is also possible to charge a car battery. The power of a passenger car generator is approximately 1 kW. Car generators are quite reliable in operation because they ensure uninterrupted operation of many devices in the car, and therefore the requirements for them are appropriate.

Generator device

The design of a car generator implies the presence of its own rectifier and control circuit. The generating part of the generator, using a stationary winding (stator), generates three-phase alternating current, which is then rectified by a series of six large diodes and the direct current charges the battery. Alternating current is induced by the rotating magnetic field of the winding (around the field winding or rotor). Next, the current is supplied to the electronic circuit through the brushes and slip rings.

Generator structure: 1.Nut. 2. Washer. 3.Pulley 4.Front cover. 5. Distance ring. 6.Rotor. 7.Stator. 8.Back cover. 9.Casing. 10. Gasket. 11.Protective sleeve. 12. Rectifier unit with capacitor. 13.Latch holder with voltage regulator.

The generator is located at the front of the car engine and is started using the crankshaft. The connection diagram and operating principle of a car generator are the same for any car. There are, of course, some differences, but they are usually associated with the quality of the manufactured product, the power and the layout of the components in the motor. All modern cars are equipped with alternating current generator sets, which include not only the generator itself, but also a voltage regulator. The regulator equally distributes the current in the excitation winding, and it is due to this that the power of the generator set itself fluctuates at a time when the voltage at the power output terminals remains unchanged.

New cars are most often equipped with an electronic unit on the voltage regulator, so the on-board computer can control the amount of load on the generator set. In turn, on hybrid cars the generator performs the work of the starter-generator; a similar circuit is used in other designs of the stop-start system.

The principle of operation of a car generator

Connection diagram for the VAZ 2110-2115 generator

Generator connection diagram AC includes the following components:

1. Battery.
2. Generator.
3. Fuse block.
4. Ignition.
5. Dashboard.
6. Rectifier block and additional diodes.

The principle of operation is quite simple: when the ignition is turned on plus through the lock, the ignition goes through the fuse box, light bulb, diode bridge and goes through a resistor to minus. When the light on the dashboard lights up, then the plus goes to the generator (to the excitation winding), then during the process of starting the engine, the pulley begins to rotate, the armature also rotates, due to electromagnetic induction, electromotive force is generated and alternating current appears.

The most dangerous thing for the generator is the short circuit of the heat sink plates connected to the “ground” and the “+” terminal of the generator by metal objects accidentally falling between them or conductive bridges formed by contamination.

Next, the diode passes plus into the rectifier block through a sine wave into the left arm, and minus into the right arm. Additional diodes on the light bulb cut off the negatives and only positives are obtained, then it goes to the dashboard assembly, and the diode that is there allows only the negative to pass through, as a result the light goes out and the positive then goes through the resistor and goes to the negative.

The principle of operation of a car DC generator can be explained as follows: a small direct current begins to flow through the excitation winding, which is regulated by the control unit and is maintained by it at a level of slightly more than 14 V. Most generators in a car are capable of generating at least 45 amperes. The generator operates at 3000 rpm and above - if you look at the ratio of the size of the fan belts for the pulleys, it will be two or three to one in relation to the engine frequency.

To avoid this, the plates and other parts of the generator rectifier are partially or completely covered with an insulating layer. The heat sinks are combined into a monolithic design of the rectifier unit mainly by mounting plates made of insulating material, reinforced with connecting bars.

Generator connection diagram for VAZ 2107

The VAZ 2107 charging scheme depends on what type of generator is used. To recharge the battery on cars such as VAZ-2107, VAZ-2104, VAZ-2105, which have a carburetor engine, you will need a G-222 type generator or its equivalent with a maximum output current of 55A. In turn, VAZ-2107 cars with an injection engine use a generator 5142.3771 or its prototype, which is called a high-energy generator, with a maximum output current of 80-90A. It is also possible to install more powerful generators with an output current of up to 100A. Absolutely all types of alternating current generators have built-in rectifier units and voltage regulators; they are usually made in the same housing with brushes or are removable and mounted on the housing itself.

The VAZ 2107 charging circuit has minor differences depending on the year of manufacture of the car. The most important difference is the presence or absence of a charge indicator lamp, which is located on the instrument panel, as well as the method of connecting it and the presence or absence of a voltmeter. Such circuits are mainly used on carburetor cars, while on cars with injection engines the circuit does not change, it is identical to those cars that were manufactured previously.

Generator set designations:

1. “Plus” of the power rectifier: “+”, V, 30, V+, WAT.
2. “Ground”: “-”, D-, 31, B-, M, E, GRD.
3. Excitation winding output: Ш, 67, DF, F, EXC, E, FLD.
4. Output for connection to the serviceability lamp: D, D+, 61, L, WL, IND.
5. Phase output: ~, W, R, STA.
6. Output of the stator winding zero point: 0, MP.
7. Output of the voltage regulator for connecting it to the on-board network, usually to the “+” of the battery: B, 15, S.
8. Voltage regulator output for powering it from the ignition switch: IG.
9. Voltage regulator output for connecting it to the on-board computer: FR, F.

Generator circuit VAZ-2107 type 37.3701

1. Accumulator battery.
2. Generator.
3. Voltage regulator.
4. Mounting block.
5. Ignition switch.
6. Voltmeter.
7. Battery charge indicator lamp.

When the ignition is turned on, the plus from the lock goes to fuse No. 10, and then goes to the battery charge indicator lamp relay, then goes to the contact and to the coil output. The second terminal of the coil interacts with the central terminal of the starter, where all three windings are connected. If the relay contacts close, then the control lamp lights up. When the engine starts, the generator generates current and an alternating voltage of 7V appears on the windings. A current passes through the relay coil and the armature begins to attract, and the contacts open. Generator No. 15 passes current through fuse No. 9. Similarly, the excitation winding receives power through the brush voltage generator.

Charging diagram for VAZ with injection engines

This scheme is identical to the schemes on other VAZ models. It differs from the previous ones in the method of exciting and monitoring the serviceability of the generator. It can be carried out using a special control lamp and a voltmeter on the instrument panel. Also, through the charge lamp, the generator is initially excited at the moment it starts working. During operation, the generator operates “anonymously,” that is, excitation comes directly from pin 30. When the ignition is turned on, power through fuse No. 10 goes to the charging lamp in the instrument panel. Then it goes through the mounting block to pin 61. Three additional diodes provide power to the voltage regulator, which in turn transmits it to the excitation winding of the generator. In this case, the indicator lamp will light up. It is at that moment when the generator operates on the plates of the rectifier bridge that the voltage will be much higher than that of the battery. In this case, the control lamp will not light up, because the voltage on its side on the additional diodes will be lower than on the side of the stator winding and the diodes will close. If the control lamp lights up while the generator is running, this may mean that additional diodes are broken.

Checking generator operation

There are several ways to use certain methods, for example: you can check the output current of the generator, the voltage drop on the wire that connects the current output of the generator to the battery, or check the regulated voltage.

To check, you will need a multimeter, a car battery and a lamp with soldered wires, wires for connecting between the generator and the battery, and you can also take a drill with a suitable head, since you may have to twist the rotor by the nut on the pulley.

Basic check with a light bulb and multimeter

Connection diagram: output terminal (B+) and rotor (D+). The lamp must be connected between the main output of the generator B+ and contact D+. After this, we take the power wires and connect the “minus” to the negative terminal of the battery and to the generator ground, the “plus”, respectively, to the plus of the generator and to the B+ output of the generator. We fix it on a vice and connect it.

“Ground” must be connected very last so as not to short-circuit the battery.

We turn on the tester in DC mode, attach one probe to the battery to “plus”, and the second one too, but to “minus”. Next, if everything is in working order, then the light should light up, the voltage in this case will be 12.4V. Then we take a drill and start turning the generator, accordingly, the light bulb will stop burning at this moment, and the voltage will already be 14.9V. Then we add a load, take an H4 hologen lamp and hang it on the battery terminal, it should light up. Then we connect the drill in the same order and the voltage on the voltmeter will show 13.9V. In passive mode, the battery under the light bulb gives 12.2V, and when we turn it with a drill, it gives 13.9V.

Generator test circuit

1. Check the functionality of the generator by short circuit, that is, “to spark”.
2. It is also undesirable to allow the generator to operate without consumers turned on; it is also undesirable to operate with the battery disconnected.
3. Connect terminal “30” (in some cases B+) to ground or terminal “67” (in some cases D+).
4. Carry out welding work on the car body with the generator and battery wires connected.

The generator is the main source of electricity for the machine. We'll tell you how it works, what its structure consists of.

How does he work?

When starting the engine, the main consumer of electricity is the starter; the current reaches hundreds of amperes, which causes a significant drop in battery voltage. In this mode, consumers are powered only by the battery, which is rapidly discharged. Immediately after starting the engine, the generator becomes the main source of power supply.

The generator is a source of constant recharging of the battery while the engine is running. If it doesn't work, the battery will drain quickly. It provides the required current to charge the battery and operate electrical appliances. After recharging the battery, the generator reduces the charging current and operates normally.

When turning on powerful consumers (for example, a rear window defroster, headlights) and low engine speeds, the total current consumption may be greater than the generator is capable of delivering. In this case, the load will fall on the battery and it will begin to discharge.

Drive and mounting

The drive is carried out from the crankshaft pulley by a belt drive. The larger the diameter of the pulley on the crankshaft and the smaller the diameter of the pulley, the higher the speed of the generator, and accordingly, it is able to deliver more current to consumers.

On modern machines, the drive is carried out by a poly-V-belt. Due to its greater flexibility, it allows the generator to be fitted with a small diameter pulley and hence high gear ratios. V-belt tension carried out by tension rollers with the generator stationary.

What is the device and what does it consist of?

Any generator contains a stator with a winding, sandwiched between two covers - the front, on the drive side, and the rear, on the slip ring side. The generators are bolted to the front of the engine on special brackets. The mounting feet and tension eye are located on the covers.

The covers, cast from aluminum alloys, have ventilation windows through which air is blown by a fan. Generators of a traditional design are equipped with ventilation windows only in the end part, while those of a “compact” design are equipped with ventilation windows on the cylindrical part above the frontal sides of the stator winding.

A brush assembly, which is combined with a voltage regulator, and a rectifier assembly are attached to the cover on the slip ring side. The covers are usually tightened together with three or four screws, and the stator is sandwiched between the covers, the seating surfaces of which cover the stator along the outer surface.

Generator stator: 1 - core, 2 - winding, 3 - slot wedge, 4 - slot, 5 - terminal for connection to the rectifier

The stator is made from steel sheets with a thickness of 0.8...1 mm, but more often it is wound “on edge”. When making a stator package by winding, the stator yoke above the grooves usually has projections along which the position of the layers relative to each other is fixed during winding. These protrusions improve stator cooling due to a more developed outer surface.

The need to save metal led to the creation of a stator package design made up of individual horseshoe-shaped segments. The individual sheets of the stator package are fastened together into a monolithic structure by welding or rivets. Almost all mass-produced car generators have 36 slots in which the stator winding is located. The grooves are insulated with film insulation or sprayed with epoxy compound.

Car generator rotor: a - assembled; b - disassembled pole system; 1,3 - pole halves; 2 - excitation winding; 4 - slip rings; 5 - shaft

A special feature of automobile generators is the type of rotor pole system. It contains two pole halves with protrusions - beak-shaped poles, six on each half. The pole halves are stamped and may have projections. If there are no protrusions when pressed onto the shaft, a bushing with an excitation winding wound on the frame is installed between the pole halves, and winding is carried out after installing the bushing inside the frame.

The rotor shafts are made of mild automatic steel. But when using a roller bearing, the rollers of which operate directly at the end of the shaft on the side of the slip rings, the shaft is made of alloy steel, and the shaft journal is hardened. At the threaded end of the shaft, a groove is cut for the key to attach the pulley.

Many modern designs do not have a key. In this case, the end part of the shaft has a recess or protrusion in the form of a hexagon. This allows you to keep the shaft from turning when tightening the pulley fastening nut, or when disassembling the generator, when it is necessary to remove the pulley and fan.

Brush unit- this is the structure in which the brushes are placed i.e. sliding contacts. There are two types of brushes used in automobile generators - copper-graphite and electrographite. The latter have an increased voltage drop in contact with the ring compared to copper-graphite ones. They provide significantly less wear on the slip rings. The brushes are pressed against the rings by spring force.

Rectifier units Two types are used. These are either heat sink plates into which the power rectifier diodes are pressed, or structures with highly developed fins and the diodes are soldered to the heat sinks. The diodes of the additional rectifier usually have a cylindrical or pea-shaped plastic housing or are made in the form of a separate sealed block, the inclusion of which is carried out in the circuit by busbars.

The most dangerous is the short circuit of the heat sink plates connected to the “ground” and the “+” terminal of the generator by metal objects accidentally falling between them or conductive bridges formed by contamination, because In this case, a short circuit occurs in the battery circuit and a fire is possible. To avoid this, the plates and other parts of the generator rectifier are partially or completely covered with an insulating layer. The heat sinks are combined into a monolithic design of the rectifier unit mainly by mounting plates made of insulating material, reinforced with connecting bars.

Generator bearing units These are typically deep groove ball bearings with one-time grease for life and one or two-way seals built into the bearing. Roller bearings are used only on the slip ring side and quite rarely, mainly by American companies. The fit of ball bearings on the shaft on the side of the slip rings is usually tight, on the drive side - sliding, in the cover seat, on the contrary - on the side of the slip rings - sliding, on the drive side - tight.

The generator is cooled by one or two fans mounted on its shaft. In this case, in the traditional design of generators, air is sucked by a centrifugal fan into the cover from the side of the slip rings. For generators that have a brush assembly, a voltage regulator and a rectifier outside the internal cavity and are protected by a casing, air is sucked through the slots of this casing, directing the air to the hottest places - to the rectifier and voltage regulator.


Cooling system: a - devices of conventional design; b - for increased temperature in the engine compartment; c - devices of compact design. Arrows show the direction of air flows
On cars with a dense engine compartment, generators with a special casing are used, through which cold outside air enters. For generators of a “compact” design, cooling air is taken in from both the rear and front covers.

What is a voltage regulator used for?

The regulators maintain the generator voltage within certain limits for optimal operation of electrical appliances included in the vehicle's on-board network. The generators are equipped with semiconductor electronic voltage regulators built inside the housing. Their execution patterns and design may vary, but the principle of operation is the same.

Voltage regulators have the property of thermal compensation - changing the voltage supplied to the battery, depending on the air temperature in the engine compartment for optimal battery charging. The lower the air temperature, the greater the voltage must be supplied to the battery and vice versa. The thermal compensation value reaches up to 0.01 V per 1°C. Some models of remote regulators have manual voltage level switches (winter/summer).

The device of a car generator

By design Generating sets can be divided into two groups:

• generators of traditional design with a fan at the drive pulley,
• generators of compact design with two fans in the internal cavity of the generator.

Typically, “compact” generators are equipped with a drive with an increased gear ratio through a poly-V-belt and therefore, according to the terminology adopted by some companies, are called high-speed generators.

According to the layout of the brush assembly, they are distinguished:

• generators in which the brush assembly is located in the internal cavity of the generator between the rotor pole system and the rear cover,
• generators, where slip rings and brushes are located outside the internal cavity (Fig. 1). In this case, the generator has a casing, under which there is a brush assembly, a rectifier and, as a rule, a voltage regulator.

Rice. 1. Alternator

The alternator contains stator With windings, sandwiched between two lids- front, on the drive side, and rear, on the side slip rings. The covers, cast from aluminum alloys, have ventilation windows through which air is blown by a fan through the generator.

Basic requirements for car generators

1. The generator must provide an uninterrupted supply of current and have sufficient power to:

• simultaneously supply electricity to working consumers and charge the battery;
• when all regular electricity consumers were turned on at low engine speeds, the battery was not severely discharged;
• the voltage in the on-board network was within specified limits throughout the entire range of electrical loads and rotor speeds.

2. The generator must have sufficient strength, long service life, small weight and dimensions, low noise level and radio interference.

Operating principle of the generator

The operation of the generator is based on the effect of electromagnetic induction. If a coil, for example, made of copper wire, is penetrated by a magnetic flux, then when it changes, an alternating electrical voltage appears at the coil terminals. Conversely, to generate a magnetic flux, it is enough to pass an electric current through the coil.

• Thus, to produce an alternating electric current, a coil is required through which a direct electric current flows, forming a magnetic flux, called the field winding, and a steel pole system, the purpose of which is to supply the magnetic flux to the coils, called the stator winding, in which an alternating voltage is induced.

These coils placed in the grooves of the steel structure, magnetic circuit(iron package) stator. The stator winding with its magnetic core forms generator stator (Fig. 3, item 1) - a stationary part in which an electric current is generated, and field winding With pole system and some other details ( shaft, slip rings) - rotor , rotating part.

The field winding can be powered from the generator itself. In this case, the generator operates at self-excitation. In this case, the residual magnetic flux in the generator, i.e., the flux that is formed by the steel parts of the magnetic circuit in the absence of current in the field winding, is small and ensures self-excitation of the generator only at too high rotation speeds. Therefore, such an external connection is introduced into the generator set circuit, where the field windings are not connected to the battery, usually through a generator set health lamp.

• The current flowing through this lamp into the excitation winding after turning on the ignition switch provides the initial excitation of the generator. The strength of this current should not be too high so as not to discharge the battery, but not too low, because in this case the generator is excited at too high speeds, so manufacturers stipulate the required power warning lamp- usually 2...3 W.

When the rotor rotates opposite the stator winding coils, the “north” and “south” poles of the rotor appear alternately, i.e., the direction of the magnetic flux passing through the coil changes, which causes the appearance of an alternating voltage in it. The frequency of this voltage f depends on the generator rotor speed n and the number of its pairs of poles R :

f=p*n/ 60

With rare exceptions, generators from foreign companies, as well as domestic ones, have six “south” and six “north” poles in the rotor magnetic system. In this case the frequency f 10 times less than the rotation speed of the generator rotor.

Since the generator rotor receives its rotation from the engine crankshaft, the frequency of the engine crankshaft can be measured by the frequency of the alternating voltage of the generator.

• To do this, a stator winding is made at the generator, to which the tachometer is connected. In this case, the voltage at the tachometer input has a pulsating character, since it turns out to be connected in parallel with the diode of the generator power rectifier.

Taking into account the gear ratio i belt drive from the engine to the generator signal frequency at the tachometer input f t related to engine speed n doors ratio:

f t =p*n dv (i)/ 60

Of course, if the drive belt slips, this ratio is slightly disrupted and therefore care must be taken to ensure that the belt is always sufficiently tensioned.

At R =6 , (in most cases) the above relation is simplified f t =n dv (i) /10 . The on-board network requires constant voltage to be supplied to it. Therefore, the stator winding powers the vehicle’s on-board network through rectifier , built into the generator.

Stator winding generators of foreign companies, as well as domestic ones - three-phase. It consists of three parts, called phase windings or simply phases, the voltage and currents in which are shifted relative to each other by a third of the period, i.e. by 120 0 (Fig. 2). The phases can be connected in star or delta. In this case, phase and linear voltages and currents are distinguished. Phase voltages U f act between the ends of the phase windings, and the currents I f flow in these windings, the linear voltages U l act between the wires connecting the stator winding to the rectifier. Linear currents flow in these wires J l . Naturally, the rectifier rectifies the values ​​that are supplied to it, i.e. linear.

Rice. 2. Circuit diagram of an alternating current generator with a rectifier

The generator stator (Fig. 3) is made of steel sheets with a thickness of 0.8...1 mm, but is more often done by winding “on edge”. This design ensures less waste during processing and high manufacturability. When making a stator package by winding, the stator yoke above the grooves usually has projections along which the position of the layers relative to each other is fixed during winding. These protrusions improve stator cooling due to its more developed outer surface. The need to save metal also led to the creation of a stator package design made up of individual horseshoe-shaped segments. The individual sheets of the stator package are fastened together into a monolithic structure by welding or rivets.

Rice. 3. Generator stator:
1 - core, 2 - winding, 3 - slot wedge, 4 - slot, 5 - terminal for connection to the rectifier

Almost all mass-produced car generators have 36 slots in which the stator winding is located. The grooves are insulated with film insulation or sprayed with epoxy compound.

Rice. 4. Generator stator winding diagram:
A - loop distributed, B - wave concentrated, C - wave distributed
------- 1st phase, - - - - - - 2nd phase, -..-..-..- 3rd phase

The slots contain the stator winding, made according to the circuits (Fig. 4) in the form of distributed loop (Fig. 4,A) or concentrated wave (Fig. 4,B), distributed wave (Fig. 4,C) windings. The loop winding is distinguished by the fact that its sections (or half-sections) are made in the form of coils with end-to-end connections on both sides of the stator package opposite each other. The wave winding really resembles a wave, since its frontal connections between the sides of the section (or half-section) are located alternately on one or the other side of the stator package. In a distributed winding, the section is divided into two half-sections emanating from the same slot, with one half-section emanating to the left and the other to the right. The distance between the sides of the section (or half-section) of each phase winding is 3 slot divisions, i.e. if one side of the section lies in the groove conventionally accepted as the first, then the second side fits into the fourth groove. The winding is secured in the groove with a groove wedge made of insulating material. It is mandatory to impregnate the stator with varnish after laying the winding.

A special feature of automobile generators is the type of rotor pole system (Fig. 5). It contains two pole halves with protrusions—beak-shaped poles, six on each half. The pole halves are made by stamping and may have protrusions - half-bushes. If there are no protrusions when pressed onto the shaft, a bushing with an excitation winding wound on the frame is installed between the pole halves, and winding is carried out after installing the bushing inside the frame.

Rice. 5. Car generator rotor: a - assembled; b - disassembled pole system; 1,3 - pole halves; 2 - excitation winding; 4 - slip rings; 5 - shaft

If the pole halves have half-bushings, then the excitation winding is pre-wound on the frame and installed when the pole halves are pressed on so that the half-bushings fit inside the frame. The end cheeks of the frame have retaining protrusions that fit into the interpolar spaces at the ends of the pole halves and prevent the frame from rotating on the bushing. Pressing the pole halves onto the shaft is accompanied by their caulking, which reduces the air gaps between the bushing and the pole halves or half-bushings, and has a positive effect on the output characteristics of the generator. When caulking, the metal flows into the grooves of the shaft, which makes it difficult to rewind the field winding if it burns out or breaks, since the rotor pole system becomes difficult to disassemble. The field winding assembled with the rotor is impregnated with varnish. The pole beaks at the edges are usually beveled on one or both sides to reduce magnetic noise from generators. In some designs, for the same purpose, an anti-noise non-magnetic ring is placed under the sharp cones of the beaks, located above the excitation winding. This ring prevents the beaks from oscillating when the magnetic flux changes and, therefore, emitting magnetic noise.

After assembly, the rotor is dynamically balanced, which is carried out by drilling out excess material at the pole halves. On the rotor shaft there are also slip rings, most often made of copper, crimped with plastic. The leads of the excitation winding are soldered or welded to the rings. Sometimes the rings are made of brass or stainless steel, which reduces wear and oxidation, especially when working in a humid environment. The diameter of the rings when the brush contact unit is located outside the internal cavity of the generator cannot exceed the internal diameter of the bearing installed in the cover from the side of the slip rings, since during assembly the bearing passes over the rings. The small diameter of the rings also helps reduce brush wear. It is precisely for the installation conditions that some companies use roller bearings as the rear rotor support, because ball ones of the same diameter have a shorter service life.

Rotor shafts are made, as a rule, of mild free-cut steel, however, when using a roller bearing, the rollers of which operate directly at the end of the shaft from the side of the slip rings, the shaft is made of alloy steel, and the shaft journal is cemented and hardened. At the threaded end of the shaft, a groove is cut for the key to attach the pulley. However, in many modern designs the key is missing. In this case, the end part of the shaft has a recess or protrusion in the form of a hexagon. This allows you to keep the shaft from turning when tightening the pulley fastening nut, or during disassembly, when it is necessary to remove the pulley and fan.

Brush unit- this is a plastic structure in which brushes are placed i.e. sliding contacts. There are two types of brushes used in automobile generators: copper-graphite and electrographite. The latter have an increased voltage drop in contact with the ring compared to copper-graphite ones, which adversely affects the output characteristics of the generator, but they provide significantly less wear on the slip rings. The brushes are pressed against the rings by spring force. Typically, brushes are installed along the radius of the slip rings, but there are also so-called reactive brush holders, where the axis of the brushes forms an angle with the radius of the ring at the point of contact of the brush. This reduces the friction of the brush in the guides of the brush holder and thereby ensures more reliable contact of the brush with the ring. Often the brush holder and voltage regulator form a non-separable unit.

Rectifier units are used in two types - either these are heat sink plates into which power rectifier diodes are pressed (or soldered) or on which the silicon junctions of these diodes are soldered and sealed, or these are structures with highly developed fins in which diodes, usually of the tablet type, are soldered to heat sinks. The diodes of the additional rectifier usually have a cylindrical or pea-shaped plastic housing or are made in the form of a separate sealed block, the inclusion of which is carried out in the circuit by busbars. The inclusion of rectifier units in the generator circuit is carried out by unsoldering or welding the phase terminals on special rectifier mounting pads or with screws. The most dangerous thing for the generator and especially for the wiring of the vehicle on-board network is the bridging of the heat sink plates connected to the “ground” and the “+” terminal of the generator by metal objects accidentally falling between them or conductive bridges formed by contamination, because In this case, a short circuit occurs in the battery circuit and a fire is possible. To avoid this, the plates and other parts of the rectifier of generators from some companies are partially or completely covered with an insulating layer. The heat sinks are combined into a monolithic design of the rectifier unit mainly by mounting plates made of insulating material, reinforced with connecting bars.

Generator bearing assemblies are usually deep groove ball bearings with a one-time grease for life and one or two-way seals built into the bearing. Roller bearings are used only on the slip ring side and quite rarely, mainly by American companies. The fit of ball bearings on the shaft on the side of the slip rings is usually tight, on the drive side - sliding, in the cover seat, on the contrary - on the side of the slip rings - sliding, on the drive side - tight. Since the outer race of the bearing on the side of the slip rings has the ability to rotate in the seat of the cover, the bearing and cover may soon fail, causing the rotor to touch the stator. To prevent the bearing from rotating, various devices are placed in the cover seat - rubber rings, plastic cups, corrugated steel springs, etc.

The design of voltage regulators is largely determined by their manufacturing technology. When making a circuit using discrete elements, the regulator usually has a printed circuit board on which these elements are located. At the same time, some elements, for example, tuning resistors, can be made using thick film technology. Hybrid technology assumes that resistors are made on a ceramic plate and connected to semiconductor elements - diodes, zener diodes, transistors, which in unpackaged or packaged form are soldered on a metal substrate. In a regulator made on a single crystal of silicon, the entire regulator circuitry is located in this crystal. Hybrid voltage regulators and single-chip voltage regulators cannot be disassembled or repaired.

The generator is cooled by one or two fans mounted on its shaft. In this case, in the traditional design of generators (Fig. 7, a), air is sucked into the cover by a centrifugal fan from the side of the slip rings. For generators that have a brush assembly, a voltage regulator and a rectifier outside the internal cavity and are protected by a casing, air is sucked through the slots of this casing, directing the air to the hottest places - to the rectifier and voltage regulator. On cars with a dense layout of the engine compartment, in which the air temperature is too high, generators are used with a special casing (Fig. 7, b) attached to the rear cover and equipped with a pipe with a hose through which cold and clean outside air enters the generator. Such designs are used, for example, on BMW cars. For generators of a “compact” design, cooling air is taken in from both the rear and front covers.

Rice. 7. Generator cooling system.
a - generators of conventional design; b - generators for elevated temperatures in the engine compartment; c - generators of compact design.

Arrows show the direction of air flows

High-power generators installed on special vehicles, trucks and buses have some differences. In particular, they contain two pole rotor systems mounted on one shaft and, consequently, two excitation windings, 72 slots on the stator, etc. However, there are no fundamental differences in the design of these generators from the designs considered.

Generator drive

The generators are driven from the crankshaft pulley by a belt drive. The larger the diameter of the pulley on the crankshaft and the smaller the diameter of the generator pulley (the ratio of the diameters is called the gear ratio), the higher the generator speed, and accordingly, it is able to deliver more current to consumers.

V-belt drive is not used for gear ratios greater than 1.7-3. First of all, this is due to the fact that with small pulley diameters, the V-belt wears out more.

On modern models, as a rule, the drive is carried out by a poly-V-belt. Due to its greater flexibility, it allows the installation of a small diameter pulley on the generator and, therefore, higher gear ratios, i.e. the use of high-speed generators. The tension of the poly V-belt is carried out, as a rule, by tension rollers when the generator is stationary.

Generator mounting

The generators are bolted to the front of the engine on special brackets. The mounting feet and tension eye of the generator are located on the covers. If fastening is carried out with two paws, then they are located on both covers; if there is only one paw, it is located on the front cover. In the hole of the rear paw (if there are two mounting paws) there is usually a spacer sleeve that eliminates the gap between the engine bracket and the paw seat.

Rectifier 1 contains six diodes VD1 - VD6, forming two arms: in one, the anodes of three diodes VD1 - VD3 are connected to the “+” terminal of the generator, and in the other, the cathodes of the diodes VD4 - VD6 are connected to the “-” terminal. In the single-wire circuit adopted on cars, the negative terminal is connected to ground. The leads of the phase windings of the generator stator are connected to the rectifier (the figure shows a star connection). The alternating voltages ip1 - ipz induced in the phase windings are shifted by 1/3 of the period, which is typical for a three-phase system.

AC rectifier

When the three-phase voltage changes over time, the rectifier diodes move from a closed state to an open state; as a result, the load current has only one direction - from the “+” terminal of the generator to the “-” terminal.

Rice. 8. Generator set diagram (a) and voltage diagrams (b):

1-phase bridge rectifier; 2-additional rectifier; 3-voltage regulator

As can be seen from Figure 8 b, at time 0, there is no voltage in winding L1; in winding L3 is positive, and in winding L2 is negative. The direction of the arrow towards the midpoint 0 of the stator winding is taken as positive voltage. The rectified current is supplied to consumers in the direction of the arrows through the diodes VD3 and VD4 that are in the open state.

At time t1 there is no voltage in winding L2, in winding L1 it is positive, and in winding L3 it is negative. The rectified current is supplied to consumers through diodes VD1 and VD5. In each arm of the rectifier, one diode is open for approximately 1/3 of the period.

The line voltage for a star connection is 1.73 times greater than for a delta connection. Therefore, when connecting in a triangle, there must be more turns in the stator winding than when connecting in a star. However, the phase current when connected in a delta is 1.73 times less than when connected in a star. Connecting the stator winding into a triangle for high-power generators allows it to be made from thinner wire.

The rectifiers of some generators have an additional arm connected to the midpoint 0 of the stator winding. This scheme allows you to increase the generator power by 15...20% due to the action of the third harmonic components of the phase voltage.

The rectified voltage Ud has a pulsating character. The GB battery serves as a kind of filter that smoothes the rectified voltage of the generator, while the battery current turns out to be pulsating.

In a valve generator, the rectifier diodes do not conduct current from the battery to the stator winding, and therefore there is no need for a reverse current relay. This significantly simplifies the generator set circuit. When parking the car for a long time, the battery may discharge to the excitation winding. Therefore, in some models of automobile generators, the excitation winding is connected to an additional rectifier 2. The additional rectifier is made of three diodes VD7-VD9, the anodes of which are connected to terminal D. In this case, only the voltage from the generator is supplied to the excitation winding through the additional rectifier 2 and rectifier arm 1 with diodes VD4-VD6.

The use of an additional rectifier also has a negative side associated with self-excitation of the generator. The generator can self-excite if there is a residual magnetic flux in it and a sufficiently low resistance of the excitation circuit. Therefore, to produce voltage in the operating range of rotation speeds of its rotor, the circuit uses a control lamp HL, which ensures reliable excitation of the generator.

A significant disadvantage of brush generators is the presence of a contact unit consisting of electric brushes and rings, through which current is supplied to the rotating excitation winding. This unit is subject to wear. Dust, dirt, fuel and oil getting on the contact unit quickly damage it.

Voltage regulators

The regulators maintain the generator voltage within certain limits for optimal operation of electrical appliances included in the vehicle's on-board network. All voltage regulators have measuring elements, which are voltage sensors, and actuators that regulate it.

In vibration controllers, the measuring and actuating element is an electromagnetic relay. For contact-transistor regulators, the electromagnetic relay is located in the measuring part, and the electronic elements are in the actuating part. These two types of regulators have now been completely replaced by electronic ones.

Semiconductor contactless electronic controllers are usually built into the generator and combined with the brush assembly. They change the excitation current by changing the time the rotor winding is switched on to the supply network. These regulators are not subject to misadjustment and do not require any maintenance other than monitoring the reliability of the contacts.

Voltage regulators have the property of thermal compensation - changing the voltage supplied to the battery, depending on the air temperature in the engine compartment for optimal battery charging. The lower the air temperature, the greater the voltage must be supplied to the battery and vice versa. The thermal compensation value reaches up to 0.01 V per 1°C. Some models of remote regulators (2702.3702, PP-132A, 1902.3702 and 131.3702) have stepped manual voltage level switches (winter/summer).

Operating principle of the voltage regulator

Currently, all generator sets are equipped with semiconductor electronic voltage regulators, usually built inside the generator. Their designs and design may be different, but the operating principle of all regulators is the same. The voltage of a generator without a regulator depends on the rotation speed of its rotor, the magnetic flux created by the field winding, and, consequently, on the current strength in this winding and the amount of current supplied by the generator to consumers. The higher the rotation speed and the excitation current, the greater the generator voltage; the greater the current of its load, the lower this voltage.

The function of the voltage regulator is to stabilize the voltage when the rotation speed and load changes by influencing the excitation current. Of course, you can change the current in the excitation circuit by introducing an additional resistor into this circuit, as was done in previous vibration voltage regulators, but this method is associated with a loss of power in this resistor and is not used in electronic regulators. Electronic regulators change the excitation current by turning on and off the excitation winding from the supply network, while changing the relative duration of the on-time of the excitation winding. If to stabilize the voltage it is necessary to reduce the excitation current, the switching time of the excitation winding is reduced; if it is necessary to increase it, it is increased.

It is convenient to demonstrate the operating principle of the electronic regulator using a fairly simple diagram of an EE 14V3 type regulator from Bosch, shown in Fig. 9:

Rice. 9. Diagram of the voltage regulator EE14V3 from BOSCH:
1 - generator, 2 - voltage regulator, SA - ignition switch, HL - warning lamp on the instrument panel

To understand the operation of the circuit, we should remember that, as shown above, the zener diode does not pass current through itself at voltages below the stabilization voltage. When the voltage reaches this value, the zener diode “breaks through” and current begins to flow through it. Thus, the zener diode in the regulator is the voltage standard with which the generator voltage is compared. In addition, it is known that transistors pass current between the collector and emitter, i.e. open if current flows in the base-emitter circuit, and do not allow this current to pass through, i.e. closed if the base current is interrupted. The voltage to the zener diode VD2 is supplied from the output of the generator "D+" through a voltage divider on resistors R1 (R3 and diode VD1, which performs temperature compensation. While the generator voltage is low and the voltage on the zener diode is lower than its stabilization voltage, the zener diode is closed, through it, and, therefore, and no current flows in the base circuit of transistor VT1, transistor VT1 is also closed. In this case, the current through resistor R6 from the “D+” terminal enters the base circuit of transistor VT2, which opens, and current begins to flow through its emitter-collector junction in the base of transistor VT3 , which also opens.In this case, the excitation winding of the generator is connected to the power circuit through the emitter-collector junction VT3.

The connection of transistors VT2 and VT3, in which their collector terminals are combined, and the base circuit of one transistor is powered from the emitter of the other, is called a Darlington circuit. With this connection, both transistors can be considered as one composite transistor with a high gain. Typically, such a transistor is made on a single silicon crystal. If the voltage of the generator has increased, for example, due to an increase in the rotation speed of its rotor, then the voltage on the zener diode VD2 also increases, when this voltage reaches the value of the stabilization voltage, the zener diode VD2 “breaks through”, the current through it begins to flow into the base circuit of the transistor VT1, which The emitter-collector transition opens and short-circuits the base output of the composite transistor VT2, VT3 to ground. The composite transistor closes, breaking the power supply circuit of the field winding. The excitation current drops, the generator voltage decreases, the zener diode VT2 and transistor VT1 close, the composite transistor VT2,VT3 opens, the excitation winding is reconnected to the power circuit, the generator voltage increases and the process repeats. Thus, the generator voltage is regulated by the regulator discretely by changing the relative time of inclusion of the excitation winding in the power circuit. In this case, the current in the excitation winding changes as shown in Fig. 10. If the generator rotation speed has increased or its load has decreased, the winding turn-on time decreases; if the rotation speed decreases or the load increases, it increases. The regulator circuit (see Fig. 9) contains elements characteristic of the circuits of all voltage regulators used on cars. Diode VD3, when closing the composite transistor VT2, VT3, prevents dangerous voltage surges arising from an open circuit of the excitation winding with significant inductance. In this case, the field winding current can be closed through this diode and dangerous voltage surges do not occur. Therefore, the VD3 diode is called a quenching diode. Resistance R7 is the hard feedback resistance.

Rice. 10. Change in current strength in the field winding JB over time t during operation of the voltage regulator:

ton, toff - respectively, the time of turning on and off the excitation winding of the voltage regulator; n1 n2 - generator rotor speed, with n2 greater than n1; JB1 and JB2 - average current values ​​in the field winding

When the composite transistor VT2, VT3 is opened, it is connected in parallel to the resistance R3 of the voltage divider, while the voltage on the zener diode VT2 decreases sharply, this speeds up the switching of the regulator circuit and increases the frequency of this switching, which has a beneficial effect on the quality of the generator set voltage. Capacitor C1 is a kind of filter that protects the regulator from the influence of voltage pulses at its input. In general, capacitors in the regulator circuit either prevent the circuit from going into oscillatory mode and the possibility of extraneous high-frequency interference influencing the operation of the regulator, or they speed up the switching of transistors. In the latter case, the capacitor, charging at one moment in time, is discharged onto the base circuit of the transistor at another moment, accelerating the switching of the transistor with the inrush of discharge current and, therefore, reducing its heating and energy loss in it.

From Fig. 9 the role of the HL lamp for monitoring the operating condition of the generator set (charge monitoring lamp on the car’s instrument panel) is clearly visible. When the car engine is not running, closing the contacts of the ignition switch SA allows current from the battery GA to flow through this lamp into the excitation winding of the generator. This ensures the initial excitation of the generator. At the same time, the lamp lights up, signaling that there is no break in the excitation winding circuit. After starting the engine, almost the same voltage appears at the generator terminals “D+” and “B+” and the lamp goes out. If the generator does not develop voltage while the car engine is running, the HL lamp continues to light in this mode, which is a signal of a generator failure or a broken drive belt. The introduction of resistor R into the generator set helps to expand the diagnostic capabilities of the HL lamp. If this resistor is present, in the event of an open circuit in the field winding while the car engine is running, the HL lamp lights up. Currently, more and more companies are switching to the production of generator sets without an additional excitation winding rectifier. In this case, the generator phase output is fed into the regulator. When the car engine is not running, there is no voltage at the generator phase output and the voltage regulator in this case goes into a mode that prevents the battery from discharging to the excitation winding. For example, when the ignition switch is turned on, the regulator circuit switches its output transistor into an oscillatory mode, in which the current in the field winding is small and amounts to fractions of an ampere. After starting the engine, the signal from the generator phase output switches the regulator circuit to normal operation. In this case, the regulator circuit also controls the lamp for monitoring the operating condition of the generator set.

Rice. 11. Temperature dependence of the voltage maintained by the Bosch EE14V3 regulator at a rotation speed of 6000 min-1 and a load current of 5A

For its reliable operation, the battery requires that as the temperature of the electrolyte decreases, the voltage supplied to the battery from the generator set increases slightly, and as the temperature rises, it decreases. To automate the process of changing the level of the maintained voltage, a sensor is used, placed in the battery electrolyte and included in the voltage regulator circuit. But this is only for advanced cars. In the simplest case, thermal compensation in the regulator is selected in such a way that, depending on the temperature of the cooling air entering the generator, the generator set voltage changes within specified limits. Figure 11 shows the temperature dependence of the voltage supported by the Bosch EE14V3 regulator in one of the operating modes. The graph also shows the tolerance range for this voltage. The falling nature of the dependence ensures a good charge of the battery at negative temperatures and prevents increased boiling of its electrolyte at high temperatures. For the same reason, on cars designed specifically for use in the tropics, voltage regulators are installed with a deliberately lower setting voltage than for temperate and cold climates.

Operation of the generator set in different modes

When starting the engine, the main consumer of electricity is the starter; the current reaches hundreds of amperes, which causes a significant voltage drop at the battery terminals. In this mode, electricity consumers are powered only by the battery, which is intensively discharged. Immediately after starting the engine, the generator becomes the main source of power supply. It provides the required current to charge the battery and operate electrical appliances. After recharging the battery, the difference between its voltage and the generator becomes small, which leads to a decrease in the charging current. The power source is still the generator, and the battery smoothes out the generator voltage ripples.

When powerful consumers of electricity are turned on (for example, a rear window defroster, headlights, heater fan, etc.) and a low rotor speed (low engine speed), the total current consumption may be greater than the generator is capable of delivering. In this case, the load will fall on the battery and it will begin to discharge, which can be monitored by readings from an additional voltage indicator or voltmeter.

When installing the battery into the vehicle, make sure the connection polarity is correct. An error will lead to immediate failure of the generator rectifier and a fire may occur. The same consequences are possible when starting the engine from an external current source (lighting up) if the connection polarity is incorrect.

When operating a vehicle you must:

• monitor the condition of the electrical wiring, especially the cleanliness and reliability of the connection of the contacts of the wires suitable for the generator and voltage regulator. If the contacts are poor, the on-board voltage may exceed permissible limits;
• disconnect all wires from the generator and from the battery when electrically welding car body parts;
• Make sure the alternator belt is properly tensioned. A belt that is loosely tensioned does not ensure efficient operation of the generator; a belt that is tensioned too tightly leads to the destruction of its bearings;
• Immediately find out the reason for the generator warning lamp to come on.

The following actions are unacceptable:

• leave the car with the battery connected if you suspect a malfunction of the generator rectifier. This can lead to a complete discharge of the battery and even a fire in the electrical wiring;
• check the functionality of the generator by shorting its terminals to ground and to each other;
• check the serviceability of the generator by disconnecting the battery while the engine is running due to the possibility of failure of the voltage regulator, electronic elements of injection systems, ignition, on-board computer, etc.;
• do not allow electrolyte, antifreeze, etc. to come into contact with the generator.