Why do you need a generator in a car. Scheme of a car generator: principle of operation What is a generator in a car for?
If we compare a car with a living organism, then its engine acts as a heart, and a generator acts as a nervous system. Will the car be able to move without this unit? Yes, it can, but not for long, not yet. It is the car generator that charges the battery, maintaining the overall voltage of the working network. We will tell you about the principle of operation of the generator and its main elements.
How the unit is arranged
Rotor
This part, in fact, is an electromagnet with one winding. It is located on the shaft. A special core is attached over the winding, the diameter of which is one and a half to two millimeters less than the diameter of the starter. The current supply is provided by copper rings. They are also located on the shaft and are connected to the winding with special brushes.
Winding
The starter winding is made of copper wire. It is attached to the grooves of the core. The latter is made in the form of a circle and is made of metal with enhanced magnetic properties. This material is called transformer iron. Since the generator is three-phase, the starter is equipped with three windings. They are connected to each other and together resemble a triangle.
A rectifier bridge is connected at the point of their connection. The wire from which the winding is made is provided with double heat-resistant insulation. In most cases, a special varnish is used for this.
Relay-regulator
Another important element is the relay-regulator. It is an electronic circuit and has an output to graphite brushes. The relay-regulator can be installed in the generator housing or separately from it. In the first case, it is located next to the graphite brushes, and in the second, the brushes are attached to.
Rectifier bridge
The part is formed from six diodes. The latter are located on a conductive base in pairs and are combined with each other. At the output, the AC voltage is converted to DC. The bridge is also called a "horseshoe" due to the fact that outwardly it resembles this product.
On the video - the generator device:
The principle of operation of the generator
The operation of a car generator is based on the principle of education. This happens in the stator windings. Electric voltage is generated due to the influence of a constant magnetic field formed around the core. The motor drives the generator rotor by means of a belt drive. A constant voltage is applied to the winding, which is sufficient to create a magnetic flux.
When the core rotates along the windings, an electromotive force arises in them. The relay-regulator adjusts the strength of the magnetic flux in accordance with the load that is removed from the generator terminal. At the output, a voltage is formed in the range of 13.6–14.2 (this depends on the time of year). This is enough to recharge and keep it constantly charged. The on-board network is also powered by the positive terminal and is connected in parallel with the battery. Regardless of which generator you bought, the device and principle of operation will be the same for all samples. All such units work the same way.
On the video - the principle of operation of the generator:
Not a single car generator can work without. This element ensures that the constant voltage is maintained, which the unit generates due to the change in current strength that occurs in the windings. If the rotor rotates at a high frequency without a regulator, the voltage can reach a couple of tens of volts. This will lead to burnout of lamps and breakage of windings, diodes and other devices.
Regulator types
According to their design, voltage regulators are divided into two main categories:
- hybrid;
- integral.
The first group includes regulators, in the electronic circuit of which radio elements and are simultaneously used. In modern car models, integral regulators are most often used. All components of such devices (with the exception of the output stage) are made on the basis of thin-film microelectronic technology.
Pilot lamp
In order to avoid problems with the regulator, keep an eye on the control lamp. It is located on the dashboard of the car. If the lamp is on when the generator is running, this indicates a malfunction of the voltage regulator or the unit itself.
Car alternator mount
The car generator is usually attached to the front of the engine with bolts and special brackets. Mounting paws and an eye of the device are located on the covers. If the generator is attached with two legs, they are located on two engine covers. If only one mounting foot is used, it is placed on only one cover (front). The rear leg usually has a hole in which the spacer is installed. It eliminates the gap formed between the motor bracket and the foot base.
Different operating modes of the generator set
In order to understand the car generator, you need to understand the modes of its operation. The first mode that we will consider is the operation of the car generator during engine start. When starting the engine, the starter is mainly consumed by electricity. In this mode, the current strength is very large, and this causes a significant decrease in the voltage at the battery terminal. Thus, consumers of electricity are powered only by the battery, which is intensively discharged.
Immediately after starting the engine, the generator becomes the main source of power. The device provides the current needed to charge the battery and operate various electrical appliances. After , the charging current level drops. The generator remains the source of electricity.
When powerful consumers of electricity, such as headlight heaters or stove fans, are turned on, the rotor begins to rotate slowly. Then the generator can not give as much current as required. In this mode, the load is transferred to the battery, which is quickly discharged.
You can replace the generator in the car, but for this you must follow some rules:
- the new unit must have the same current-speed characteristics as the standard one;
- the energy parameters of the generators must be the same;
- the dimensions of the new generator must be suitable so that it can be easily installed on the motor;
- the units must have the same gear ratios;
- the circuits of both generators must be completely identical.
Keep in mind that, in general, units installed on foreign cars are attached with only one paw. At the same time, domestic devices using two paws. Therefore, when changing a foreign unit to ours, you will have to replace the mounting bracket on the motor.
When installing the battery in a car, you need to make sure that the polarity is connected correctly. In the event of an error, the alternator rectifier will fail, and this may lead to a fire. The same danger is fraught with starting the motor with incorrect polarity determination.
During the operation of the machine, the following rules must be observed:
- control, monitor the cleanliness of the contacts and the reliability of their connection (if the wire contacts are bad, the on-board voltage is out of range);
- disconnect the wires from the car generator and battery during electric welding of structural elements;
- make sure that the alternator belt is properly tensioned (if it is loosely tensioned, the generator will not be able to work efficiently, if it is too tight, its bearings will wear out quickly);
- in case of signaling by a control lamp - immediately find out the reason for this.
On the video - generator repair:
Under no circumstances should you do the following:
- leave the car with the battery connected if you suspect that the rectifier is defective (this will lead to battery discharge and wiring fire);
- check whether the generator is working by closing its outputs to each other or disconnecting the battery when the engine is running (due to this, the voltage regulator, on-board computer, and electronic elements of the ignition system may break);
- to allow the ingress of residues of antifreeze or other liquid on the generator;
- leave the generator on if the battery terminals are removed (this leads to damage to the electrical equipment of the machine and the voltage regulator).
We told you about the main features of the generator. This knowledge will be useful to any driver who seeks to understand cars. Remember that the generator is a very complex device, so it is important to take good care of it. Constantly monitor the condition of all its parts, as well as the degree of tension of the drive belt. Then the car generator will be able to serve you as long as possible.
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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 - clamping sleeve | 14 - output "67" |
| 2 - bushing | 15 - neutral wire plug |
| 3 - buffer sleeve | 16 – a hairpin of fastening of the generator |
| 4 - back cover | 17 - fan impeller |
| 5 - screw for fastening the rectifier unit | 18 - pulley |
| 6 - rectifier block | 19 - plates |
| 7 - valve (diode) | 20 - ring |
| 8 - rear bearing | 21 - front bearing |
| 9 - contact rings | 22 - rotor winding |
| 10 - rotor shaft | 23 - rotor |
| 11 - brushes | 24 - stator winding |
| 12 - output "30" | 25 - stator |
| 13 - brush holder | 26 - front cover |
| 1 - casing | 17 - pulley |
| 2 - output "B +" for connecting consumers | 18 - nut |
| 3 - noise suppression capacitor 2.2 uF | 19 - rotor shaft |
| 4 - common output of additional diodes (connected to the “D +” output of the voltage regulator) | 20 - front bearing of the rotor shaft |
| 5 - holder of positive diodes of the rectifier unit | 21 - beak-shaped pole pieces of the rotor |
| 6 - holder of negative diodes of the rectifier unit | 22 - rotor winding |
| 7 - stator winding leads | 23 - sleeve |
| 8 - voltage regulator | 24 - coupling screw |
| 9 - brush holder | 25 - rear rotor bearing |
| 10 - back cover | 26 - bearing sleeve |
| 11 - front cover | 27 - slip rings |
| 12 - stator core | 28 - negative diode |
| 13 - stator winding | 29 - positive diode |
| 14 - remote ring | 30 - additional diode |
| 15 - washer | 31 - output "D" (common output of additional diodes) |
| 16 - conical washer |
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
The main task of the rotor- create a rotating magnetic field, for this purpose, the excitation winding is located on the rotor shaft. It is placed in two halves of the pole, each pole half has six protrusions - they are called beaks. There are also contact rings on the shaft, there are two of them, and it is through them that the excitation winding is powered. Rings, most often, are made of copper, steel rings or brass rings are quite rare. The leads of the excitation winding are soldered directly to the rings.
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 integrated) 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:
- 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.
- 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.
When the key is turned in the ignition lock, current is supplied to the excitation winding through the brush assembly and slip rings. A magnetic field is induced in the winding. The generator rotor begins to move with the rotation of the crankshaft. The stator windings are pierced by the magnetic field of the rotor. An alternating voltage appears on the terminals of the stator windings. When a certain speed is reached, the excitation winding is powered directly from the generator, that is, the generator goes into self-excitation mode.
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
This material is educational and informational, and is intended mainly for those who have not dealt with cars, or have just purchased their first car. Let's consider one of the important topics, or rather, answer the question of what a car starter and generator are, as well as why a generator and a starter are needed in a car, what function they perform. You will learn all this in this educational material.
So let's start with the generator. The main purpose of the generator is to provide power to the electrical consumers of the car and charge the battery (battery) while the engine is running.
Over the past years, the design of the generator has changed significantly, and DC generators, as well as vibration voltage regulators, have already become a thing of the past. Now modern generators have increased specific indicators, their output power has increased, weight and dimensions have been reduced, and reliable protection elements have appeared. Generators of past years had an output current of 45-60A, and now their power has increased significantly and reaches 90-140 Amperes and even higher. All this is due to the presence of additional devices and equipment in modern cars. This includes lighting, air conditioning, heating systems and entertainment of modern cars. All this requires additional energy resources.
For trucks and buses, as well as special equipment, high-power generators are installed, which have differences compared to cars. They have differences in their design, for example, two pole systems of the rotor are installed, mounted on one shaft, they also have 2 excitation windings, and so on. For car owners, we list below the main types of generator malfunction. I would like to note that do-it-yourself repair of a starter or generator requires certain knowledge and skills. If you do not have any, then it is recommended to contact specialists in this matter.
The main types of generator malfunction:
No battery charging - the control lamp on the dashboard lights up when the engine is running (the fuse in the generator excitation circuit is blown, the drive belt is loose or damaged, an open or short circuit in the wiring, the voltage regulator is faulty);
The battery is discharged during the operation of the car (there is no fuse contact in the sockets, the drive belt is loose, the voltage regulator is faulty);
The battery is recharged during the operation of the car (the voltage regulator is faulty, there is no additional “+” on the voltage regulator for some generator models);
A loud noise is heard during the operation of the generator (loosening of the pulley fastening nut, the rectifier unit is faulty, contamination of slip rings and brushes, lack of lubrication in the bearings or their wear, breakage of one of the stator windings);
etc.
Some of the leading generator manufacturers are such brands as VALEO, BOSCH, NIPPON DENCO, MAGNETI MARELLI, MOTORCRAFT, HITACHI, DELCO REMY, MITSUBISHI.
The principle of operation of a car generator is not at all difficult to understand if we consider the main components of this important vehicle device, which converts the mechanical energy received from the car's motor into electrical energy.
Car generator circuit - what does a car generator consist of?
This vehicle assembly is necessary for charging and providing electrical equipment with the vehicle engine with the electrical power it needs. As a rule, the generator is located in front of the car engine. To date, there are two constructive versions of the device of interest to us:
- standard;
- compact.
Both the first and second designs have a number of common elements. These include the following mechanisms:
- brush knot;
- voltage regulator;
- stator;
- rectifying device;
- frame;
- rotor.
The difference between a standard and a compact generator lies in the design of their housing, drive pulley, rectifier assembly and fan. In addition, they have different geometric dimensions, which depends not only on their device, but also on the manufacturer. At the same time, the operation of a car generator remains unchanged, no matter what form it is given by design engineers.
The principle of operation of a car generator - how exactly does it work?
The functioning of the device of interest to us is based on the phenomenon of electromagnetic induction. Its essence is as follows. When the magnetic flux passes through the copper coil, a voltage is generated at its terminals. It is in its magnitude proportional to the speed with which this same flow changes.
And in order for the magnetic flux to be formed, according to the effect of induction, an electric current must be passed through the coil. In fact, if you need to get an electrical alternating current, it is enough to have on hand:
- coil (alternating voltage will be removed from it);
- source of magnetic alternating field.
The specified source in a modern vehicle is a rotating rotor, consisting of a shaft, a pole system and slip rings. But another important element - the stator - is needed to form an electric current (alternating). The stator consists of a core, which is recruited from steel plates, and a winding.
The principle of operation of a car generator - a circuit diagram of a node
It is not enough to know how a car generator works in general if you want to fully understand the principle of its operation. In addition, it is necessary to study the electrical circuit of the generator unit, which includes the following components:
- ignition switch;
- "mass";
- brush knot;
- a capacitor designed to suppress interference;
- winding diodes;
- positive output of the mechanism;
- rectifier diodes (power) - negative and positive;
- winding power;
- voltage regulator;
- stator windings;
- signal lamp (it gives a signal about the malfunction of the described device).
A constant voltage is obtained from an alternating one due to the operation of the rectifier unit, which makes it possible for the generator device to supply the battery with current. When the speed and load of the crankshaft change, the voltage regulator begins to act. Its task is to start the excitation winding in time. As you can see, the principle of operation of the generator is quite simple and understandable.
Two current sources are provided to power the on-board network of the vehicle. And it is very important for the driver to understand the principles of operation of the car generator, which, along with the battery, is designed to provide energy to the electrical equipment of the car.
Strict requirements are imposed on the reliability and stability of devices of this kind.
In the Russian Federation, electrical equipment manufactured and used must comply with GOST R 52230-2004. The document establishes general technical conditions that apply to car starter batteries. The mentioned national standard fully complies with international standards, which allows the use of foreign-made components on domestic machines.
At the dawn of the automotive industry and up to the 60s of the last century, direct current generators were used in on-board networks - capricious and low-power. With the advent of semiconductor (selenium and silicon) rectifiers, AC units began to be installed on machines. They are three times smaller in weight and at the same load provide a higher stability of the output current.
Why does a car need a generator?
The generator is used to maintain a certain voltage and current in the on-board network. The main purpose of a car generator is to provide a stable power supply to electrical equipment when the engine is running - in particular, for:
- Battery charge.
- Supply of all consumers of electric current under normal conditions.
- Power supply of consumers together with the battery during extreme operation.
The use of a car generator allows you to restore the battery charge, which is spent on starting the engine using a starter. At the same time, the voltage in the on-board network remains within strictly established limits, exceeding the electrochemical potential of the battery plates.
Having understood the question of why a generator is needed in a car, it is necessary to understand that in the event of a failure of the unit, the engine will work for some more time due to the battery. You can extend this period by turning off all secondary consumers: heater fan, air conditioner, audio system. When the battery runs out, the engine will shut down.
The device and design of the automobile generator
Three-phase alternating current generating sets installed on modern machines can be of 2 types: standard and compact. The general arrangement of automobile generators of 2 types is the same - they consist of the following elements:
- Pulley with shaft and bearings.
- Rotor with slip rings.
- Stator winding.
- Generator housings.
- Voltage regulator.
- rectifying device.
- Brush knot.
The designs of automotive generators differ only in layout features. With the same electrical parameters, standard units are much larger than small ones. Compactness is ensured through the use of modern materials and technologies.
Here is what the generator consists of and what functions its components perform:
- The pulley transmits rotation from the crankshaft to the rotor using a belt.
- The generator housing has two covers (front, rear) and is needed to connect the elements into a single structure. Brackets are placed on the outer surface, with the help of which the device is mounted on the engine.
- The rotor is a shaft on which excitation windings and slip rings made of electrotechnical copper are installed.
- The stator includes a magnetic circuit from a package of steel plates, in which curly grooves are cut. They contain three-phase windings from a single-core copper wire, where the current is generated.
- The voltage regulator is made as a separate unit or combined with a brush assembly. The main purpose is to control the operation of the generator by changing the current in the field winding.
- The rectifier according to the Larionov scheme consists of two parts: aluminum heat sinks, each of which has three power diodes pressed into it. The valves provide the conversion of alternating voltage to direct voltage, which is used in the on-board network to power electrical equipment.
- The voltage is transmitted to the excitation winding through a special unit and cylindrical slip rings. The brushes are made from special grades of graphite and are mounted in a holder with dielectric guides. To ensure tight contact, they are spring-loaded, and voltage is applied to them through a wire pressed into the base.
Dealing with the device of the generator of a modern car, it is necessary to single out the mechanical and electrical parts in it. The first (which includes a pulley and two rotor bearings) ensures its rotation in the housing. The second part actually generates electric current to power the on-board network. The described scheme of an automobile generator was first used in the products of the American company Neuville in 1946. Such devices were equipped with military vehicles and buses.
Main parameters of the generator
The main nominal parameters are determined based on the technical requirements for the design of a particular vehicle model:
- Voltage. In accordance with GOST 52230-2004, it is selected from the range from 7.14 to 28 V.
- Recoil current.
- The frequency of excitation and self-excitation.
The current-speed characteristic determines the dependence of the rated current of the generator on the frequency of its rotation. The voltage in the on-board network of cars and commercial vehicles, as well as buses is 12 V, especially powerful and special vehicles - 24 V. The maximum recoil current is determined at a rotor speed of 6,000 min-1.
Another important characteristic of this unit is efficiency. For modern models, this figure is at the level of 50-60%.
How does a car generator work?
The device begins to function only after the engine is started by a starter, which is powered directly from the battery. The key principle of the car generator is to convert mechanical energy into electrical energy. A pulley is installed on the crankshaft of the power unit, which spins the rotor mounted on maintenance-free bearings through a belt drive.
The excitation winding located on the rotating armature is powered from the battery through the brush assembly and slip rings. To protect the battery from self-discharge, the connection is made through a special rectifier consisting of three diodes. The voltage value in this circuit is regulated by an electronic or electromechanical stabilizer, integrated or made as a separate device.
The rotating armature creates electromagnetic fields that induce an alternating current in the stator windings. It goes to the rectifier, which is a block of diodes. It includes six valves: three negative and three positive. They provide the conversion of phase voltage to linear. The connection of the generator windings is carried out according to the "triangle" or "star" scheme. In the first case, the current is 1.7 times lower than in the second. The triangle is used on high-power car models.
The described principle of operation of the automobile generator ensures that the voltage in the on-board network is maintained in the range from 13.9 to 14.5 V. The exact value depends on the crankshaft speed and load level. Consumers (for example, a battery) are connected to the generating set through the “B+” output.
What is the purpose of a voltage regulator in a generator?
When changing the speed of the crankshaft and, accordingly, the rotor, power surges can occur in the on-board network, which adversely affect the operation of consumers. Jumps are eliminated by limiting the excitation current transmitted through the brushes from the voltage regulator to the rotor. The control is carried out by changing the time of connecting the armature winding depending on the load on the on-board network.
If the regulator malfunctions or the brush assembly and slip rings are damaged, the battery may be undercharged or overcharged. Long-term operation of the machine with such a defect will lead to battery failure.
A generator malfunction can be identified by an indicator on the instrument panel. The battery charge light on after starting indicates insufficient voltage in the network, and blinking indicates an excess.
Conclusion
Even the most general idea of the device and principles of operation of a car generator can help to avoid electrical equipment malfunctions. The generator starts working after starting the engine and acts as the main source of current in the car.
During the operation of the car, it is necessary to carefully monitor the tension of the drive belt, which affects the position of the generator. On a number of modern cars, the unit is firmly fixed, and a worn V-belt or V-ribbed belt must be changed immediately. Maintaining the generator in good condition will avoid large expenses for major repairs of the car.
