What is a generator? Scheme of a car generator: principle of operation What is a generator in a car for?

When it comes to powering a car with electrical energy, many car owners, for some reason, only remember the battery (battery), here, we read - how to choose a battery. But after all, the main detail, due to which the transformation of the energy coming from the engine, from mechanical to electrical, is the generator. It is he who feeds all the electrical equipment in the car (when running) and charges the battery.

The device of the automobile generator.

Consider what it consists of, as well as how this automotive unit works. True, I will immediately make a reservation that we will be talking about a car alternator, since it is this type of them that is installed on modern vehicles.

What is a generator made of?

The car generator, as a rule, has the following components:

1. a pulley is a kind of entry point (using a belt) for mechanical energy into the generator;
2. the body of the generator, which is formed by two covers, front and rear, almost all other components of the part we are considering are actually attached to them;
3. rotor - is attached to the front cover of the generator housing and consists of a steel shaft with 2 steel bushings (they are beak-shaped) and an excitation winding between them, to which, as a rule, copper cylindrical slip rings are attached;
4. stator - responsible for the power of the generator and consists of a metal core with 36 grooves and a winding;
5. rectifier shield - with the help of 6 powerful diodes (3 positive and 3 negative) it converts the voltage that the stator creates into the DC voltage of the car's on-board network;
6. voltage regulator - monitors that, i.e. regulates so that the voltage of the on-board network of the machine is always within the specified limits, regardless of the load, ambient temperature and rotor operation.

Diagram of a car generator.

The principle of operation of the generator.

This means that when the driver turns the key in the ignition, voltage is supplied to the winding (there is a magnetic field in it) in the rotor from the battery through the brush assembly. And as soon as the engine crankshaft starts to rotate, as you remember, thanks to the pulley, the generator rotor also starts to rotate. The magnetic field that is created in the latter starts the stator windings, thereby creating an alternating voltage at their terminals. At a certain speed, the generator stops being powered by mechanical energy and begins to create the voltage it needs on its own (the excitation winding is powered inside the generator).

The resulting voltage is sent to the rectifier board, where it is converted into direct current, which charges the battery and powers the car's electrical appliances.

Moreover, if the crankshaft changes its speed of rotation, then a voltage regulator is also included in this system. Depending on the external load, it regulates the turn-on time of the field winding: with a decrease in load and / or an increase in the speed of rotation of the crankshaft, the turn-on time of the field winding is reduced, and with an increase in load and / or a decrease in crankshaft speed, it increases. That is the job of a car generator. In addition, I recommend that you read two articles:

An electrical machine that converts mechanical energy into electrical current is called a car generator. The function of the alternator in the car is to charge the battery and power the electrical equipment while the engine is running. An alternator is used as a car generator.

The generator is located in the engine, most often in its front part, driven from the crankshaft. On hybrid vehicles, the generator performs the work of a starter-generator, a similar scheme is used in some other designs of the stop-start system. Denso, Delphe and Bosch are currently the world's leading manufacturers of alternators.

There are two types of car generator designs: compact and traditional. The differences that characterize these types consist of a difference in the layout of the fan, they differ in the design of the housing, the rectifier unit and the drive pulley, and geometric dimensions. The general parameters available in both types of automotive generators are:

• Rotor;
• stator;
• Frame;
• Voltage regulator;
• Rectifier block;
• Brush knot.

1 - generator; 2 - negative diode; 3 - additional diode; 4 - positive diode; 5 - control lamp of the battery discharge; 6 - instrument cluster; 7 - voltmeter; 8 - mounting block; 9 - additional resistors of 100 Ohm, 2 W; 10 - ignition relay; 11 - ignition switch; 12 - battery; 13 - capacitor; 14 - rotor winding; 15 - voltage regulator

One or two fan impellers are placed on the rotor shaft (their number depends on the design) and a driven drive pulley is fixed. Two maintenance-free ball bearings make up the rotor bearing assembly. A roller bearing can also be located on the side of the slip rings on the shaft.

The stator is necessary to create an alternating electric current, it combines a metal core and windings, the core is made of plates, they are made of steel. It has 36 grooves for winding windings, windings are laid in these grooves, there are three of them, they form a three-phase connection. There are two ways to lay the windings in the grooves - the wave method and the loop method. The windings are connected to each other according to the "star" and "triangle" schemes.

What are these schemes?

• "Star" - one ends of the windings are connected at one point, and the other ends are conclusions;
• "Triangle" - an annular connection of the ends of the windings in a sequence, the conclusions come from the connection points.

The brush assembly serves to ensure the transfer of excitation current to the contact rings. It consists of two graphite brushes, springs that press them, and a brush holder. In the generators of modern machines, the brush holder is located with a voltage regulator in a single non-separable unit.

The rectifier unit performs the function of converting the sinusoidal voltage generated by the generator into the DC voltage of the car's on-board network. These are plates that act as heat sinks, with mounted diodes. There are six power semiconductor diodes in the block, two diodes for each phase, one for the “positive” and the other for the “negative” output of the generator.

On many generators, the excitation winding is connected through a separate group, which consists of two diodes. These rectifiers prevent the battery discharge current from flowing through the coil when the engine is not running. When the windings are connected according to the "star" principle, two additional power diodes are installed on the zero terminal, allowing you to increase the generator power by up to 15 percent. The rectifier unit is connected to the generator circuit at special mounting sites by soldering, welding, or bolting.

Voltage regulator- its purpose is to maintain the generator voltage within certain limits. Currently, generators are equipped with semiconductor electronic (or integral) voltage regulators.

Voltage regulator designs:

• hybrid design - the use of radio elements and electronic devices in an electronic circuit together;
• integrated design - all components of the regulator (not counting the output stage) are made using thin-film microelectronic technology.

The voltage regulator produces a change in the voltage supplied to charge the battery by temperature compensation of the voltage (depending on t air). The higher the air temperature, the less voltage goes to the battery.

The generator is driven by a belt drive, it ensures the rotation of the rotor at a speed exceeding the crankshaft speed by two to three times. In different designs of the generator, a poly-V-belt or a V-belt can be used:

1. V-belt has the prerequisites for rapid wear (depending on the specific pulley diameter) since the scope of the V-belt is limited by the size of the driven pulley.
2. V-ribbed belt is considered more universal, applicable for small diameters of the driven pulley, with its help a larger gear ratio is realized. Modern models of generators have a V-ribbed belt in their designs.

The alternating voltage is converted by the rectifier unit into a constant one. In this state, the generator is engaged in providing the required current to charge the power supply to consumers and the battery.

The voltage regulator is activated when the load and crankshaft speed change. He is engaged in adjusting the turn-on time of the excitation winding. The turn-on time of the field winding decreases with a decrease in the external load and an increase in the generator speed. Time increases with increasing load and decreasing speed. When the current consumed exceeds the capabilities of the generator, the battery is switched on. On the instrument panel there is a control lamp that controls the operable state of the generator.

The main parameters of the generator:

• Rated voltage;
• rated excitation frequency;
• rated current;
• frequency of self-excitation;
• Efficiency (coefficient of performance).

Current-speed characteristic- this is the dependence of the current strength on the frequency of rotation of the generator.

In addition to the nominal values, the current-speed characteristic has other points:

• minimum current and minimum operating speed (40-50% of the rated current is the minimum current);
• maximum current and maximum speed (no more than 10% maximum current exceeds the rated current).

Video

The most basic generator function – battery charge battery and power supply to the electrical equipment of the engine.

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

Generator device

The device of a car generator implies the presence of its own rectifier and control circuit. The generating part of the generator, using a fixed winding (stator), generates a 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). Further, the current through the brushes and slip rings is fed to the electronic circuit.

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

The generator is located in front of the car engine and is started using the crankshaft. The connection diagram and the principle of operation of the car generator are the same for any car. Of course, there are some differences, but they are usually associated with the quality of the manufactured goods, the power and layout of the components in the motor. In all modern cars, alternating current generator sets are installed, which include not only the generator itself, but also a voltage regulator. The regulator equally distributes the current strength in the field winding, it is due to this that the power of the generator set itself fluctuates at the moment when the voltage at the output power 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 vehicles, the generator performs the work of a starter-generator, a similar scheme is used in other designs of the stop-start system.

The principle of operation of the auto generator

Connection diagram of the generator VAZ 2110-2115

Generator connection diagram alternating current 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 the resistor to minus. When the light on the dashboard lights up, then the plus goes to the generator (to the excitation winding), then in the process of starting the engine, the pulley starts to rotate, the armature also rotates, due to electromagnetic induction, an electromotive force is generated and alternating current appears.

The most dangerous for the generator is the closure of the heat sink plates connected to the “mass” and the “+” terminal of the generator with metal objects accidentally caught between them or conductive bridges formed by pollution.

Further, the diode passes plus into the rectifier unit through the sinusoid into the left shoulder, and minus into the right shoulder. Additional diodes on the light bulb cut off the minuses and only pluses are obtained, then it goes to the dashboard node, and the diode that is there it passes only the minus, as a result, the light goes out and the plus then goes through the resistor and goes to minus.

The principle of operation of a DC car generator can be explained as follows: a small DC current begins to flow through the excitation winding, which is regulated by the control unit and maintained at a level of just over 14 V. Most generators in a car are capable of producing at least 45 amperes. The alternator is running at 3000 rpm and above - if you look at the ratio of the fan belts to 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. In a monolithic design of the rectifier unit, heat sinks are mainly combined with mounting plates made of insulating material, reinforced with connecting bars.

Wiring diagram for a generator on a VAZ 2107

The VAZ 2107 charging scheme depends on the type of generator used. To recharge the battery on cars such as: VAZ-2107, VAZ-2104, VAZ-2105, which are on 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 an increased energy generator, with a maximum output current of 80-90A. You can also install more powerful generators with a return current of up to 100A. Rectifier units and voltage regulators are built into absolutely all types of alternators; they are usually made in one housing with brushes or removable and mounted on the housing itself.

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

Generator set designations:

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

Scheme generator VAZ-2107 type 37.3701

1. Accumulator battery.
2. Generator.
3. Voltage regulator.
4. Mounting block.
5. Ignition switch.
6. Voltmeter.
7. Control lamp of a charge of the rechargeable battery.

When the ignition is turned on, the plus from the lock goes to fuse No. 10, and then it goes to the battery charge control lamp relay, then goes to the contact and to the coil output. The second output of the coil interacts with the central output of the starter, where all three windings are connected. If the relay contacts are closed, then the control lamp is on. When the engine is started, 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, while the contacts open. Generator No. 15 passes current through fuse No. 9. Similarly, the excitation winding receives power through the brush voltage generator.

VAZ charging scheme with injection engines

Such a scheme is identical to the schemes on other VAZ models. It differs from the previous ones in the way of excitation and control for 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 initial excitation of the generator occurs at the time of the start of work. During operation, the generator operates “anonymously”, that is, excitation comes directly from the 30th output. When the ignition is turned on, power through fuse No. 10 goes to the charging lamp in the instrument panel. Then, through the mounting block, it enters the 61st output. 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 control lamp will light up. It is at the very moment when the generator will work 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 burn, 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 during the operation of the generator the control lamp lights up to the floor, this may mean that additional diodes are broken.

Checking the operation of the generator

You can use certain methods in several ways, for example: you can check the recoil 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, as you may have to turn the rotor by the nut on the pulley.

Elementary test with a light bulb and a multimeter

Wiring diagram: output terminal (B+) and rotor (D+). The lamp must be connected between the main generator output B + and the D + contact. After that, we take the power wires and connect the “minus” to the negative terminal of the battery and to the generator ground, “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.

"Mass" must be connected to the last very, so as not to short-circuit the battery.

We turn on the tester in the (DC) direct current mode, we hook one probe to the battery to the “plus”, the second also, but to the “minus”. Further, 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 begin to turn the generator, respectively, the light at this moment will stop burning, 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, in the same order, we connect the drill and the voltage on the voltmeter will already show 13.9V. In passive mode, the battery under the light bulb gives 12.2V, and when we turn the drill, then 13.9V.

Generator test circuit

1. Check the generator for operability by short circuit, that is, “for a spark”.
2. It is also undesirable to allow the generator to work without consumers turned on, while operation with the battery disconnected is undesirable.
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 wires of the generator and battery connected.

An automobile generator, which is certainly part of the equipment of any vehicle, can be compared with the role of a power plant in supplying energy to the needs of the national economy.

It is the main (when the engine is running) source of electricity in the car and is designed to maintain a predetermined and stabilized voltage of the car's electrical network through electrical wires that entangle the entire car from the inside. The principle of operation of a car generator is based on the theoretical representation of the operation of a classical electric generator that transforms non-electric types of energy into electrical energy.

In the specific case of a car generator, the generation of electrical energy occurs through the transformation of the mechanical rotational movement of the crankshaft of the motor unit.

General principle of operation

The theoretical prerequisites underlying the operation of electric generators are based on the well-known case of electromagnetic induction, which transforms one type of energy (mechanical) into another (electrical). The action of this effect is manifested when placing copper wires laid in the form of a coil and placed in a magnetic field of variable magnitude.

This contributes to the appearance of an electromotive force in the wires, which sets the electrons in motion. This movement of electrical particles generates in, and an electrical voltage arises at the terminal contacts of the wires, the level directly dependent on the rate at which the magnetic field changes. The alternating voltage generated in this way must be fed into the external network.

In an automobile generator, stator windings are used to create a magnetic phenomenon, in which the rotor armature rotates under the influence of the field. On the armature shaft there are current-carrying windings connected to special contacts in the form of rings. These ring contacts are also attached to the shaft and rotate with it. From the rings with the help of conductive brushes, the electrical voltage is removed and the generated energy is supplied to the electrical consumers of the vehicle.

The generator is started by means of a drive belt from the friction wheel of the crankshaft of the engine unit, which is started from a battery source to start work. To ensure efficient transformation of the produced energy, the diameter of the generator pulley must be noticeably inferior in diameter to the crankshaft friction wheel. This provides higher revolutions of the shaft of the generating set. Under these conditions, it functions with an increase in its efficiency and provides increased current characteristics.

Requirements

To ensure safe operation in a given range of characteristics of the entire complex of electrical devices, the operation of an automobile generator must meet high technical parameters and guarantee the generation of a stable voltage level over time.

The main requirement for automotive generators is stable current generation with the required power characteristics. These parameters are designed to provide:

• recharging;
• simultaneous operation of all involved electrical equipment;
• stable mains voltage in a wide range of rotor shaft speeds and dynamically connected loads;

In addition to the above parameters, the generator is designed taking into account its operation under critical loads and must have a strong case, at the same time have a small mass and acceptable overall dimensions, and have a low and acceptable level of industrial radio interference.

The device and design of the automobile generator

Fastening

The car's generator can be easily found in the engine compartment by lifting the hood cover. There it is fixed with bolts and special corners to the front of the engine. Mounting paws and a tension eye of the device are placed on the generator case.

Frame

Almost all units of the unit are installed in the generator case. It is manufactured using light alloy metals based on aluminum, which is excellent for the task of dissipating heat. The body structure is a combination of two main parts:

• front cover from the side of slip rings;
• end cap on the drive side;

Brushes, a voltage regulator and a rectifier bridge are fixed on the front cover. The covers are combined into a single body structure by means of special bolts.

The inner surfaces of the covers fix the outer surface of the stator, securing its position. Also important structural components of the housing structure are the front and rear bearings, which provide the proper conditions for the functioning of the rotor and fix it on the cover.

Rotor

The design of the rotor assembly consists of an electromagnet circuit with an excitation winding mounted on a carrier shaft. The shaft itself is made of alloy steel supplemented with lead additives.

Copper slip rings and special spring-loaded brush contacts are also fixed to the rotor shaft. Slip rings are responsible for supplying current to the rotor.

stator

The stator assembly is a structure consisting of a core with numerous grooves (in most used cases, their number is 36), in which the turns of three windings are laid, having electrical contact with each other either according to the "star" or "triangle" scheme. The core, also called a magnetic circuit, is made in the form of a hollow spherical circle from metal plates, riveted together or welded into a single monolithic block.

To increase the level of magnetic field strength on the stator windings, transformer iron with enhanced magnetic parameters is used during the production of these plates.

Voltage regulator

This electronic unit is designed to compensate for the instability of the rotation of the rotor shaft, which is connected to the crankshaft of the vehicle's power unit, which operates in a wide range of speed changes. The voltage regulator is connected to graphite current collectors and contributes to the stabilization of the given constant output voltage supplied to the electrical network of the machine. In this way, he guarantees uninterrupted operation of electrical equipment.

According to their design solution, regulators are divided into two groups:

• discrete;
• integral;

The first type includes electronic units, on the structural board of which radioelements are mounted, developed using a discrete (case) technology, characterized by a non-optimal density of the elements.

The second type includes the majority of modern electronic voltage regulation units, developed taking into account the integral method of arranging radio elements, made on the basis of thin-film microelectronic technology.

Rectifier

Due to the fact that a constant voltage is required for the correct functioning of on-board devices, the generator output feeds the car network through an electronic assembly assembled on powerful rectifier diodes.

This 3-phase rectifier, consisting of six semiconductor diodes, three of which are connected to the negative terminal ("ground"), and the other three are connected to the positive terminal of the generator, is designed to transform AC voltage into DC. Physically, the rectifier unit consists of a horseshoe-shaped metal heat sink with rectifier diodes placed on it.

brush knot

This assembly has the appearance of a plastic construction and is designed to transmit voltage to the slip rings. It contains several elements inside the case, the main of which are spring-loaded brush sliding contacts. They come in two modifications:

• electrographite;
• copper-graphite (more wear-resistant).

Structurally, the brush assembly is often manufactured in one block with a voltage regulator.

Cooling system

The removal of excess heat, which is formed inside the generator housing, is provided by fans mounted on its rotor shaft. Generators, in which the brushes, voltage regulator and rectifier unit are moved outside, outside of its housing and protected by a special casing, take fresh air through special cooling slots in it.

The device of a classical design, with the placement of the above-mentioned nodes inside the generator housing, provides a fresh air flow from the side of the slip rings.

Operating modes

To understand the principle of operation of a car generator, it is necessary to present its operating modes.

• the initial period of starting the engine;
• operating mode of the engine.

At the initial moment of starting the engine, the main and only consumer that consumes electrical energy is the starter. The generator is not yet involved in the process of generating energy, and the supply of electricity at this moment is provided only by the battery. Due to the fact that the strength of the current consumed in this circuit is very large and can reach hundreds of amperes, it is intensive to consume the previously stored electrical energy.

After the start process is completed, the engine enters the operating mode, and the generator becomes a full power supplier. It generates the current necessary for the functioning of various electrical equipment that is connected to work. Together with this function, the alternator charges the battery while the engine is running.

After the battery has set the required amount, the need for the recharging process decreases, the current consumption drops noticeably, and the generator continues to support the operation of only electrical equipment. As other resource-intensive consumers of electricity are connected to work, the power of the generator at some points in time may not be enough to provide the total load, and then the battery is included in the overall operation, the operation of which in this mode is characterized by a rapid loss of charge.

Conclusion

The automobile generator is designed and designed for power supply of standard electrical appliances and the transformation of the mechanical energy of the crankshaft of the power unit into electrical energy.

The generator is located under the hood on the front of the engine. The design of the generator contains the main components - a housing, a stator, a rotor, bearings, a voltage regulator, a rectifier bridge, a brush assembly and fans.

The generator is one of the main elements of the electrical equipment of the car, providing simultaneous power to consumers and recharging the battery.

The principle of operation of the device is based on the conversion of mechanical energy that comes from the motor into voltage.

In combination with a voltage regulator, the unit is called a generator set.

In modern cars, an AC unit is provided that fully meets all the stated requirements.

Generator device

The elements of the AC source are hidden in one housing, which is also the basis for the stator winding.

In the process of manufacturing the casing, light alloys are used (most often aluminum and duralumin), and holes are provided for cooling, ensuring timely removal of heat from the winding.

Bearings are provided in the front and rear of the casing, to which the rotor is attached - the main element of the power source.

Almost all elements of the device are placed in the casing. At the same time, the housing itself consists of two covers located on the left and right sides - near the drive shaft and control rings, respectively.

Two covers are combined with each other using special bolts made of aluminum alloy. This metal is characterized by low weight and the ability to dissipate heat.

An equally important role is played by the brush assembly, which transmits voltage to the slip rings and ensures the operation of the assembly.

The product consists of a pair of graphite brushes, two springs and a brush holder.

Also pay attention to the elements located inside the casing:

What are the requirements for a car generator?

There are a number of requirements for a car generator set:

• The voltage at the output of the device and, accordingly, in the on-board network must be maintained within a certain range, regardless of the load or crankshaft speed.
• The output parameters must have such indicators that in any of the operating modes of the machine, the battery receives sufficient charge voltage.

In addition, each car owner should pay special attention to the level and stability of the output voltage. This requirement is due to the fact that the battery is sensitive to such changes.

For example, if the voltage drops below the norm, the battery does not charge to the required level. As a result, problems are possible in the process of starting the motor.

In the opposite situation, when the installation produces an increased voltage, the battery is recharged and breaks faster.

The principle of operation of a car generator, circuit features

The principle of operation of the generator unit is based on the effect of electromagnetic induction.

In the case of the passage of a magnetic flux through the coil and its change, voltage appears and changes on the terminals (depending on the rate of flux change). The reverse process works the same way.

So, to obtain a magnetic flux, it is necessary to apply voltage to the coil.

It turns out that two components are required to create an alternating voltage:

• Coil (it is from it that the voltage is removed).
• The source of the magnetic field.

An equally important element, as noted above, is the rotor, which acts as a source of the magnetic field.

The pole system of the node has a residual magnetic flux (even in the absence of current in the winding).

This parameter is small, therefore, it can cause self-excitation only at increased speeds. For this reason, a small current is first passed through the rotor winding, which ensures the magnetization of the device.

The circuit mentioned above implies the passage of current from the battery through the control lamp.

The main parameter here is the current strength, which should be within the normal range. If the current is overestimated, the battery will quickly discharge, and if it is underestimated, the risk of excitation of the generator at the twentieth motor (idling) will increase.

Taking into account these parameters, the power of the light bulb is also selected, which should be 2-3 watts.

As soon as the voltage reaches the required parameter, the light goes out, and the excitation windings are powered by the car generator itself. In this case, the power supply switches to self-excitation mode.

The voltage is removed from the stator winding, which is made in a three-phase version.

The node consists of 3 individual (phase) windings, wound according to a certain principle on the magnetic core.

The currents and voltages in the windings are offset by 120 degrees. At the same time, the windings themselves can be assembled in two versions - a “star” or a “triangle”.

If the delta circuit is selected, the phase currents in the 3 windings will be 1.73 times less than the total current supplied by the generator set.

That is why the “triangle” scheme is most often used in high power automotive generators.

This is just due to the lower currents, due to which it is possible to wind the winding with a wire of a smaller cross section.

The same wire can also be used in star connections.

In order for the created magnetic flux to go to its intended purpose and be directed to the stator winding, the coils are located in special grooves of the magnetic circuit.

Due to the appearance of a magnetic field in the windings and in the stator magnetic circuit, eddy currents appear.

The action of the latter leads to heating of the stator and a decrease in the power of the generator. To reduce this effect, steel plates are used in the manufacture of the magnetic circuit.

The generated voltage enters the on-board network through a group of diodes (rectifier bridge), which was mentioned above.

After opening, the diodes do not create resistance, and allow the current to flow freely into the on-board network.

But with a reverse voltage, I is not skipped. In fact, only the positive half-wave remains.

Some car manufacturers are replacing diodes with zener diodes to protect electronics.

The main feature of the parts is the ability not to pass current up to a certain voltage parameter (25-30 Volts).

After passing this limit, the zener diode "breaks through" and passes the reverse current. At the same time, the voltage on the “positive” wire of the generator remains unchanged, which does not pose risks to the device.

By the way, the ability of a zener diode to maintain a constant U at the terminals even after a “breakdown” is used in regulators.

As a result, after passing through the diode bridge (zener diodes), the voltage is rectified and becomes constant.

For many types of generator sets, the field winding has its own rectifier, assembled from 3 diodes.

Thanks to this connection, the discharge current from the battery is excluded.

Diodes related to the excitation winding work on a similar principle and feed the winding with a constant voltage.

Here, the rectifier device consists of six diodes, three of which are negative.

During the operation of the generator, the excitation current is lower than the parameter that the car generator gives.

Therefore, to rectify the current on the field winding, diodes with a rated current of up to two Amperes are sufficient.

For comparison, power rectifiers have a rated current of up to 20-25 Amperes. If you want to increase the power of the generator, put another shoulder with diodes.

Operating modes

To understand the features of the functioning of a car generator, it is important to understand the features of each of the modes:

• In the process of starting the engine, the main consumer of electrical energy is the starter. A feature of the mode is the creation of an increased load, which leads to a decrease in the voltage at the battery output. As a result, consumers take current only from the battery. That is why in this mode the battery is discharged with the greatest activity.
• After starting the engine, the car alternator switches to power source mode. From that moment on, the device provides the current that is necessary to power the load in the car and recharge the battery. As soon as the battery reaches the required capacity, the charging current level decreases. At the same time, the generator continues to play the role of the main power source.
• After connecting a powerful load, for example, an air conditioner, interior heating, and others, the rotor speed slows down. In this case, the car generator is no longer able to cover the current needs of the car. Part of the load is transferred to the battery, which operates in parallel with the power source and begins to gradually discharge.

Voltage regulator - functions, types, control lamp

The key element of the generator set is the voltage regulator - a device that maintains a safe U level at the stator output.

These products are of two types:

• Hybrid - regulators, the electrical circuit of which includes both electronic devices and radio components.
• Integral - devices based on thin-film microelectronic technology. In modern cars, this option is most widely used.

An equally important element is a control lamp mounted on the dashboard, which can be used to conclude that there are problems with the regulator.

The ignition of the light bulb at the time of starting the engine should be short-term. If it burns constantly (when the generator set is in operation), this indicates a breakdown of the regulator or the assembly itself, as well as the need for repair.

The subtleties of fastening

The generator set is fixed using a special bracket and bolted connection.

The assembly itself is attached to the front of the engine, thanks to special paws and eyes.

If special paws are provided on the automobile generator, the latter are located on the motor covers.

In the case of using only one fixing foot, the latter is placed only on the front cover.

As a rule, a hole is provided in the paw installed in the rear part with a distance sleeve installed in it.

The task of the latter is to eliminate the gap created between the stop and the mount.

Alternator mounting Audi A8.

And so the unit is mounted on the VAZ 21124.

Generator Faults and How to Eliminate Them

The electrical equipment of the car tends to break down. In this case, the greatest problems arise with the battery and the generator.

In the event of failure of any of these elements, the operation of the vehicle in normal operation becomes impossible, or the car is completely immobilized.

All generator breakdowns are conditionally divided into two categories:

• Mechanical. In this case, problems arise with the integrity of the housing, springs, belt drive and other elements that are not related to the electrical component.
• Electrical. This includes malfunctions of the diode bridge, wear of the brushes, short circuits in the windings, breakdowns of the regulator relay, and others.

Now consider the list of faults and symptoms in more detail.

1. Insufficient charging current output:

2. The second situation.

When the car generator produces the required level of current, but the battery still does not charge.

The reasons may be different:

• Poor quality of the ground contact between the regulator and the main assembly. In this case, check the quality of the contact connection.
• Failure of the voltage relay - check and change it.
• Worn or stuck brushes - replace or clean from dirt.
• The protective relay of the regulator has tripped due to a short to ground. The solution is to find the place of damage and remove the problem.
• Other reasons are oiling of the contacts, breakdown of the voltage regulator, coil short circuit in the stator windings, poor belt tension.

3. Generator is running but making excessive noise.

Possible faults:

• Short circuit between stator turns.
• Wear of the bearing seat.
• Loosening the pulley nut.
• Bearing destruction.

Repair of a car generator should always begin with an accurate diagnosis of the problem, after which the cause is eliminated through preventive measures or by replacing the failed unit.

Operational practice shows that it is not difficult to change a car generator, but to solve the problem, a number of rules must be observed:

• The new device must have the same current-speed parameters as the factory unit.
• Energy indicators should be identical.
• The gear ratios of the old and new power supply must match.
• The unit to be installed must be suitable in size and easily attached to the motor.
• The schemes of the new and old car generator should be the same.

Please note that devices mounted on foreign-made cars are fixed differently than domestic ones, for example, like on a TOYOTA COROLLA generator
and Lada Granta
.Consequently, if you change a foreign unit with a domestic product, you will have to install a new mount.

At the end of the story about car generators, it is worth highlighting a number of tips on what is necessary and what car owners should not do during operation.

The main point is the installation, during which it is important to approach the polarity connection with utmost attention.

If you make a mistake in this matter, the rectifier device will break down and the risk of fire increases.

Starting the engine with incorrectly connected wires carries a similar danger.

To avoid problems during operation, it is worth adhering to a number of rules:

• Keep the contacts clean and check the condition of the car's electrical wiring. Pay special attention to the reliability of the connection. In the case of using bad contact wires, the on-board voltage level will go beyond the permissible limit.
• Keep an eye on the alternator. In the event of a weak tension, the power supply will not be able to perform its tasks. If you tighten the belt, it is fraught with rapid wear of the bearings.
• Discard the wires from the generator and battery when performing electric welding.
• If the control lamp lights up and continues to burn after starting the engine, find out and eliminate the cause.

Special attention should be paid to the relay-regulator, as well as checking the voltage at the output of the power source. In charge mode, this parameter should be at the level of 13.9-14.5 volts.

In addition, from time to time check the wear and sufficiency of the generator brushes, the condition of the bearings and slip rings.

The height of the brushes must be measured with the holder removed. If the latter has worn out to 8-10 mm, a replacement is required.

As for the force of the springs holding the brushes, it should be at the level of 4.2 N (for VAZ). At the same time, inspect the contact rings - they should not have traces of oil.

Also, the car owner must remember a number of prohibitions, namely:

• Do not leave the car with the battery connected if there is a suspicion of a broken diode bridge. Otherwise, the battery will quickly discharge, and the risk of ignition of the wiring increases.
• Do not test the alternator for proper operation by jumpering its leads or disconnecting the battery while the engine is running. In this case, damage to electronic components, on-board computer or voltage regulator is possible.
• Do not allow technical fluids to come into contact with the generator.
• Do not leave the unit on if the battery terminals have been removed. Otherwise, this can lead to damage to the voltage regulator and electrical equipment of the car.