What type of generators are installed on modern cars? Why do you need a generator in a car?
Have you ever thought about such a simple question that a modern car practically resembles a “home on wheels”? It has everything: lighting, refrigerator, vacuum cleaner, air conditioning, coffee maker, etc. And, nevertheless, none of us is afraid of “automotive electricity,” that is, there is no fear of “shying out.” This is because the source of electricity in a car is the battery when the engine is not running, or the generator when the engine is running. And the supply voltage is only 12V. And it, as is known from school course physics, is not dangerous to human life. Let's strain our memory and remember a simple formula:
U-voltage
I-current strength
From this formula it follows that
It is the magnitude of the current that is dangerous to human life. The human body has a certain electrical resistance, for each of us it has its own value, for some it is less, for others it is more, but in a general approximation this value can be considered constant. When the power supply voltage is 12V, the amount of current flowing through the human body is insufficient to damage it, that is, our body is able to resist it. IN best case scenario, this can be compared with mosquito bite, or even less. Therefore, we boldly pick up exposed wires in the car, without fear of being “knocked.”
Now let's see what happens if we increase the voltage of the power supply. Since the electrical resistance of our body is a constant value (again, I repeat, this is only conditional; in fact, the value of the resistance of the human body depends on many factors), then as the voltage of the power source increases, the current flowing through it will increase. As soon as it reaches a value at which our body is no longer able to resist it, at that moment we will “shudder”. It was experimentally determined that the human body can resist electric current up to an increase in the voltage of the power supply to 36V (although under certain circumstances this value can be dangerous). All power sources above this value are dangerous to human life. And in our homes the supply voltage is 220V, that is, about 6 times the maximum permissible safe voltage for human life! How is it possible, you ask, was it really impossible to use the same voltage in our homes as in a car? After all, the number of people affected by electric current in everyday life could be reduced to almost zero! Don't rush, it's not that simple. The fact is that both the battery and the generator in the car are sources of direct current, and our homes are connected to an alternating current source, which is power plants. These two types of electric current have different properties. If a direct current does not change its magnitude and direction over time, then alternating current changes over a certain time in magnitude and direction, in fact, that’s why it is called variable.
Now let’s compare the distance from the current source (battery or generator) to the devices in the car (headlights, refrigerator, radio, etc.) with the distance from the power plant to our house. In the first case it is meters, and in the second it is tens or even hundreds of kilometers. And this is where it lies main reason why we use alternating current in our homes. The fact is that direct current cannot be transmitted over long distances without noticeable losses. In other words, if power plants supplied our homes with 12V DC voltage, like in a car, then electricity could not overcome the resistance of wires of such a long length, and there would be no benefit from our sockets. If you use alternating current, the situation is much better. It can be transmitted over vast distances without significant losses. In addition, since losses do exist (where would we be without them!), we have found a way to minimize them during long-distance transmission. And this method follows from the formula:
P-power
U-voltage
I - current strength
Since the higher the current strength, the greater the losses, in the case of using alternating current with the same power, it is enough to increase the voltage many times (up to tens of thousands of volts), the current strength will decrease, which means the losses will also decrease. At the right point, just before being supplied to consumers, the alternating current is again reduced to the required value (220 volts), and it enters our homes. That is, the main advantage of alternating current is that its voltage is quite easy to increase or decrease using a transformer. In the case of direct current, it would be necessary to increase the power of the power source (power station), and most of it would be spent on overcoming the resistance of the wires.
Everywhere in our yards we can see transformers (substations). A group of houses is connected to each of them, and it is they who ensure the stability of the voltage in our outlets. But after you insert the cord plug of your household appliance (TV, mobile phone charger, etc.), interesting things happen. High voltage alternating current 220V, which we are all so afraid of, is converted into low voltage DC, completely harmless to human life. By the way, it is during this transformation that very large losses of electricity occur. As the most simple example I'll give you the next one. Touch the charger with your hands while charging your mobile phone. It's warm. That is, in the process of converting alternating current with a voltage of 220V to direct current with a voltage of 5V lion's share electricity is dissipated as heat into the surrounding space. Now imagine the number of such chargers in the world, and you will understand the amount of electricity losses. And you and I, that is, the end consumers, pay for all these losses. From all that has been said above, it suggests interest Ask: Is it possible to equip our houses with one common large AC-to-DC converter? Electricity losses in one such converter would be much less than the total losses of our devices (wholesale, as they say, is cheaper). I think that many people are asking this question, and it’s only a matter of time. Today, unfortunately, this issue is quite difficult to solve, but sooner or later we will come to the conclusion that such a wasteful attitude towards resources threatens our very existence. Today, as they say, “we have what we have,” which means we will proceed from this.
To make it more clear where electricity comes from in our sockets, let’s consider this simple diagram:
Of course, it is greatly simplified (in practice, three phase wires and a neutral are suitable from the power plant to the electrical switchboard in the house), but, nevertheless, it clearly helps to see that “bread does not grow on trees.” As you can see, from the source of electricity to the sockets in our apartments, the electric current passes through several intermediate points, and in each of them, in the process of conversion and further supply, losses occur, for which, alas, you and I, dear consumer of electricity, pay! And this is only for losses, so to speak, during the “transportation” process! And then losses in the converters of our household appliances are inevitable. It’s scary to even imagine what price we pay for such a benefit of civilization as electricity in our homes. However, since in the near future, with the exception of a small group of enthusiasts, the bulk of humanity is not going to abandon it, but rather, on the contrary, the amount of electricity generated in the world will only increase, let’s move on directly to the wiring in our apartments. And let’s immediately talk about such a concept as “grounding”. Well, for those who are interested, I can say that at the dawn of the electrification of America, a real war broke out between two outstanding personalities, T. Edison and N. Tesla, which went down in history as the “war of currents.” T. Edison was an ardent supporter of direct current, and N. Tesla was a supporter (and “father” at the same time) of alternating current. I think it’s clear which of them won.
If all power supply to the electrical consumers in the car is provided only from the battery, then due to the high current consumption, its discharge occurs quite quickly. To keep the battery charged, it is charged from a generator driven, usually by a belt drive from the engine crankshaft through pulleys.
The generator in cars is equipped with alternating current. If you intend to install additional electrical equipment, check that the generator power (Watts) is sufficient to power it. The elements that make up the basis of the generator are the stator, rotor, rectifier, commutator brushes, bearings, belt pulley and electronic voltage regulator.
The generator itself produces a three-phase alternating voltage current, which is unacceptable for use in the vehicle’s on-board networks, as well as for charging battery. For this purpose, diode rectifiers are installed in the generator for each phase (three windings in the generator), which convert three-phase alternating current into pulsed direct current. The voltage is then adjusted by a built-in electronic regulator.
When the generator rotor rotates, the electric current passing through the field winding creates magnetic fluxes around the rotor poles. When the rotor is displaced, either the north or the south pole of the rotor passes under each stator tooth - a magnetic flux is created, which, passing through the stator teeth, fluctuates in magnitude and voltage. The alternating magnetic flux created in this way transmits electromotive force to the stator winding. The wedge-shaped shape of the rotor pole pieces was selected in such a way as to obtain a curve shape close to sinusoidal for the electromotive force.
Since the voltage generated by the generator depends on the rotation speed, pulleys of different diameters are used for engines with different crankshaft speeds. But this does not completely solve the problem with overvoltage at high speeds. There is a voltage regulator for this.
At high rotation speeds of the generator rotor, when the generator voltage exceeds 13.6–14.6 V, the voltage regulator blocks the current through the rotor field winding. The generator voltage decreases, the regulator unlocks when the speed drops and again passes current to the field winding. The higher the rotation speed of the generator rotor, the more the regulator is in a locked state, therefore, the more the voltage at the generator output decreases, and, accordingly, the load on the stator windings. The process of unlocking and locking the regulator occurs with a high frequency and voltage fluctuations at the generator output are almost imperceptible, and it can be considered constant, maintained within 13.6–14.6 V.
The generator produces about 14 V of constant voltage, and 12 V is sufficient for the electrical equipment of the car, so the voltage difference is used to recharge the battery. The gear ratio of the generator pulleys and the crankshaft is selected in such a way that the battery should be charged even at idle speed of the engine crankshaft.
When diagnosing a generator and when operating a vehicle in general, it is necessary to observe simple rules so that the generator does not fail:
– do not allow the battery clamp to be disconnected from the generator. Without a battery, dangerous overvoltage impulses are created in the vehicle's electrical network when any electrical equipment is disconnected. This surge voltage can damage the vehicle's electronic equipment, including the diodes of the rectifier unit or the generator voltage regulator;
– you cannot check the operation of the generator “for spark”, even by briefly connecting the “plus” terminal of the generator to “ground”. Since a significant current begins to flow through the diodes, they fail. You can only check the voltage coming from the generator with a voltmeter;
– the negative terminal of the battery should always be connected to the vehicle ground, and the positive terminal should always be connected to the generator terminal. Reversing the battery polarity immediately causes current to flow great strength through the generator diodes, and they fail;
– it is unacceptable to check the integrity of diodes with a voltage of more than 12 V or with a megger, since the megger has a voltage that is too high for them (more than 1000 V) - a breakdown (short circuit) will occur during testing. While checking the insulation of the electrical wiring with a megger, be sure to disconnect all wires connected to the generator;
– it is also necessary to disconnect all wires connected to the generator and battery when electric welding body parts;
– work on checking circuits and electrical equipment components and troubleshooting must be carried out with the engine not running and the battery disconnected. Possible faults charging systems are given in table. 1
Malfunctions of the power supply system, their possible reasons and methods of elimination.
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 important topics, or rather, we will answer the question of what a car starter and generator are, as well as why a generator and 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 vehicle's electrical consumers and charge the 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 become a thing of the past. Now modern generators have increased specific indicators, their output power has increased, their weight and dimensions have been reduced, and reliable protection elements have appeared. Generators of previous years had an output current of 45-60A, but now their power has increased significantly and reaches 90-140 Amperes and even higher. All this is explained by the presence of additional devices and equipment in modern cars. This includes lighting, air conditioning, heating systems and entertainment in modern cars. All this requires additional energy resources.
For trucks and buses, as well as special equipment, high-power generators are installed, which are different compared to passenger cars. They differ in their design, for example, they install two pole rotor systems mounted on one shaft, they also have 2 excitation windings, etc. For car owners, we list below the main types of generator malfunction. I would like to note that repairing a starter or generator with your own hands requires certain knowledge and skills. If you don’t have any, then it is recommended to contact specialists in this matter.
Main types of generator malfunction:
No battery charging - the warning light 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, there is a break or short circuit in the wiring, the voltage regulator is faulty);
The battery is discharged during the operation of the car (there is no contact between the fuses in the sockets, the drive belt is loose, the voltage regulator is faulty);
The battery is recharged while the vehicle is in use (the voltage regulator is faulty, there is no additional “+” on the voltage regulator for some generator models);
You can hear a lot of noise when the generator is running (the pulley fastening nut is loose, the rectifier unit is faulty, the slip rings and brushes are dirty, the bearings lack lubrication or are worn out, one of the stator windings is broken);
and so on.
Some of the leading generator manufacturers are such brands as VALEO, BOSCH, NIPPON DENCO, MAGNETI MARELLI, MOTORCRAFT, HITACHI, DELCO REMY, MITSUBISHI.