What to do if there is no light in the house? A power generator can help solve the problem. But if this equipment also fails, checking the generator with a multimeter will help determine the malfunction. Regardless of the type and brand, with the help of this device, having learned the cause of the malfunction, you can carry out simple repairs yourself.
There are a lot of varieties of generators, from large and powerful industrial ones to small automotive appliances. But the verification algorithm using the tester is the same for any generator.
What components and parts are checked with a multimeter
This operation provides for the diagnosis of the electrical part, while checking the following parts:
The performance of each of the listed operations requires special knowledge and skills for making measurements, so each check should be considered in more detail.
Output voltage level measurement
For each individual unit, this value will be different. Let's take a closer look at checking the car generator. We set the voltage measurement mode on the multimeter scale. First you need to check the voltage with the engine turned off. To do this, measure the voltage value at the battery terminals.
We connect the red probe to the positive terminal, we fix the black one to the minus. A charged serviceable battery will give a value of up to 12.8 V. We start the engine. Then we take a measurement.
Now this value should be no more than 14.8V, but not less than 13.5 V. If the voltage level is higher or lower, the generator is faulty.
Checking the rotor winding
To perform this operation, it is necessary to dismantle and disassemble the unit. When performing a self-test, do not forget to set the device to the circuit resistance measurement mode.
Additionally, a value of no higher than 200 Ohm is set. These routine works are carried out in 2 stages:
- Measurement of the resistance value of the rotor windings. To do this, we attach the probes to the rings of the moving part of the engine, determine the value. This will make it possible to determine the likelihood of a break in the winding circuit at a value above 5 ohms. If the device showed less than 1.9 ohms, a turn short circuit occurred. Most often, the circuit breaks at the junction of the output of the rotor winding to the ring. You can determine the defect by moving the wire at the soldering points with a probe, as well as when detecting darkened and crumbling wire insulation. In the event of a break and a short circuit (short circuit), the wires get very hot, so a breakdown can be detected by visual inspection.
- The continuity is performed to detect a short circuit to the case. The generator rotor is conveniently located for work. Then we bring one probe to the rotor shaft, and attach the second to any ring. With a good winding, the resistance reading will go off scale. If it shows low resistance, this part should be sent for rewinding. When rewinding the rotor, it is important to maintain perfect balance.
Checking the stator windings
The stator test begins with a visual inspection. We pay attention to external damage to the case and insulation, places of burning wires during a short circuit.
The defective assembly should be rewound or replaced. With the external integrity of the wires, we begin to explore with a tester.
Before starting work, make sure that the unit is disconnected from the network, that there is no contact between the stator winding leads.
Performing work on checking the normal state of the node, we make sure:
- In the integrity of the winding circuit. To do this, set the device to the resistance measurement mode. We fix the probes on the first pair of conclusions, then we check the 1st winding and the 3rd, 3rd and 2nd conclusions. If, during a break, the arrow of the analog device goes beyond the scale, the windings should be rewound.
- In the absence of an interturn short circuit and to the case. To do this, we connect one of the tips to the output, the second - to the body. If the windings are closed, there will be a lower resistance value on the scale than on healthy ones.
Voltage Regulator Troubleshooting
Remove and disconnect the wires from the part. We inspect the condition of the brushes. They should not have significant defects and chips. In the guide channels of the brush holder, the generator brushes must move freely. If they protrude beyond the edge by less than 5 mm, the generator regulator should be changed.
The test is carried out using batteries and a 12-volt light bulb. The voltage of the second power source must be at least 15 V. Therefore, we connect the batteries in series to the car battery and bring the value to the desired one. Plus from the 1st power source we attach to the output contact, we fix the minus to ground.
The light bulb is installed between the brushes. When connecting a source of 16 V., it should not burn. With a weaker battery, it burns. In case of violation of proper combustion, the regulator should be replaced.
Checking the diode bridge and capacitor
The purpose of this node is to prevent the passage of electricity to the generator. He must direct it from the generator to the consumer. In this case, any deviation is a malfunction of the diode bridge.
To check, we dismantle it and solder the conclusions on the generator. We expose the device to "ringing".
To check the power diode, we bring the black probe to the bridge plate, and attach the red probe to the output. When the multimeter reads 400-800 ohms, the diode is good, other numbers require replacement of the diode or bridge.
When checking the auxiliary diode, the operation is carried out similarly. But when changing the probes in places, the device should show the resistance value tending to infinity.
To detect a faulty capacitor, you can check it with the "old-fashioned method". To do this, you need to apply voltage to it for a short time. It must recharge.
When its contacts are closed, a spark should pierce between them. This means that the capacitor is good.
When checking a polar capacitor, you need to remove the remaining charge. Then, on the scale, set the resistance measurement. The contacts must be attached with the correct polarity. When measuring a serviceable part, the resistance gradually increases. Otherwise, when the screen shows 0, it should be replaced.
If a non-polar capacitor is being tested, the MΩ is set on the value scale. We place the probes on the contacts, regardless of polarity. Then, you need to measure the resistance value. If the number on the screen is less than 2 ohms, this is a faulty part.
In conclusion, it must be recalled that all measurements when checking the generator's performance with a multimeter are carried out by measuring the resistance value of the electric current.
Only to measure the voltage at the output of the generator, the device is configured to measure this value. Any beginner can check the generator with a multimeter. You just need to work with full responsibility and follow the instructions.
The modern car is literally stuffed with various electrical systems. The power of these systems is directly dependent on the generator, which consists of several components. The most important part of the generator is the generator stator. The operation of the generator and the power supply of the vehicle's on-board system directly depend on its condition. In the event of a generator breakdown, many are in a hurry to change it for a new one, although the generator is easy to sort out and restore almost any part of it. For example, it is quite possible to rewind the generator stator with your own hands.
What elements does the stator of a synchronous generator consist of and the principle of operation
Stator elements:
- Stator winding package;
- Stator core or package;
- Wires for connection output.
The stator itself is made of three windings, three different current values \u200b\u200bare formed in them, this circuit is a three-phase output. The ends of each winding depart from the generator body (they are connected to it), the second end is connected to the rectifier. To concentrate and amplify the magnetic field in the generator, a core made of metal plates is used.
The stator winding of a synchronous generator is located in special grooves, usually there are 36 such grooves. In each groove, the winding is held by a wedge. This wedge is made of insulating materials.
Reasons for the violation of the stable operation of the generator stator
Before you check, you need to find out exactly which generator is installed on your car. This can be found in the manual, but the best way to find out the model and parameters of the generator is by looking under the hood to find the factory tag. On it you will find all the necessary values. If you do not take into account differences in generator models, then the result of the check will be inaccurate. Knowing the basics of electrics, it is easy to identify various problems in the operation of the generator, and other systems of the electrical system.
All stator failures can be divided into two groups:
- Breakage of winding wires;
- Shorting the wire to ground.
If the vehicle is operated in conditions of high humidity or with sudden changes in temperature, the insulation may crack and delaminate. This can provoke an interturn short circuit and even failure of the entire generator, which will cause a sudden discharge of the battery, since the generator will not be able to fully charge it.
Checking the generator stator with a multimeter, how to check with a test light
The generator stator is checked for either an open or a short circuit. To check the resistance, a multimeter is used, in extreme cases, you can use a test light.
The multimeter should be switched to ohmmeter mode, after which its probes are connected to the terminals of the windings. In the absence of a break, the tester will show a resistance of 10 ohms. In the presence of a break, the resistance will show a value tending to infinity. With this result, three conclusions are checked. To obtain more accurate test results, it is better to compare the received data with passport data. You should be aware that inexpensive Chinese multimeters are not able to accurately show the resistance being removed (accuracy is sometimes required up to tenths of an ohm), so you should get a good branded device.
If it is not possible to get any multimeter, but you need to check, you can use a control light (control). It will not show the exact resistance, but it will help to find the gap. Using an insulated wire, a negative charge from the battery is applied to the winding contact. A positive charge should be applied through a light bulb to another contact. If the light is on, then the gap is not found, and the device is functioning properly. This procedure is repeated for all outputs.
Diagnostics for a short circuit is also carried out using a multimeter or test light. The positive probe must be connected to any winding contact, and the negative probe to the stator. This should be repeated with each output. The interturn short circuit is determined by the control lamp in a similar way. Call all conclusions.
Do-it-yourself generator repair
Stator repair usually refers to rewinding the generator stator. For this procedure, you will need an impressive set of tools:
- winding machine;
- Copper wire (may need about 8 spools);
- Rammer;
- Drilling machine;
- Device for drying varnished stator;
- Hammer, a set of screwdrivers and wrenches.
Winding the stator of a car generator is the repair of the stator. First you need to remove the stator itself from the generator. The old winding is scorched, but before that, the generator stator winding must be drawn up, identical to the old three-phase or single-phase winding. When singeing, the magnetic properties of the metal package of the stator do not deteriorate, so you don’t have to worry. When the winding is completely burned, a complete cleaning of the seat should be carried out. Sintoflex insulating gaskets are cut and installed in the grooves.
The winding should be rewound according to a pre-drawn scheme. The linear principle is used in a single-phase generator, and a three-phase stator winding involves a star or delta connection. When rewinding, the wire from the first groove should go immediately to the fourth. First, half of the turns are wound in one direction, then the second half in the opposite direction. The grooves are sealed with the protruding parts of the gaskets, after which the coils must be tapped with a hammer. In order not to damage the winding, you need to use a spacer.
Before checking the operability of the stator with currents, you should make sure that there is no short circuit. If there is a short circuit, then the insulation was laid poorly. You should find the problem area and, using the gasket, eliminate the breakdown.
Before impregnation with varnish, you need to check the dimensions of the rewound assembly; it should not protrude beyond the edges when assembling the generator. The contacts are connected with a thread that will not melt during drying and is placed in a container with varnish. After impregnation of the stator, it is placed in an oven for drying, after allowing the element to flow around. If a suitable furnace is not available, the stator can simply be suspended by installing a heating element from below. When the varnish stops sticking, drying will be completed. When using heat, drying usually takes about 2-3 hours.
With unstable operation of the generator, for many, the solution to the problem is to replace the entire assembly. But if you know how to check all the elements of the generator, then even the stator winding procedure will be up to you.
If you have any questions - leave them in the comments below the article. We or our visitors will be happy to answer them.
The generator is the main power source for the car's on-board network. The car generator is obliged to produce a strictly normalized voltage value, regardless of the load on the on-board network (meaning a regular load, without powerful external consumers). The voltage of the generator during operation in the car in the vast majority should be 13 ... 14.5 V. Its design has been developed for a long time and there have been no fundamental changes since then, therefore a single diagnostic technique allows you to identify malfunctions of any generators.
Appearance of the car generator
Some of the subtleties of checking at home may vary depending on the model, but the basics are the same everywhere.
Vehicle generator device
Any generator consists of the following parts:
Automobile generator device
The stationary part of the generator, the stator, has a multi-phase winding (4) and serves as a source of voltage in the car. As a rule, it has three windings connected by a star. Inside the stator, the rotor (2) rotates, on which the excitation winding is wound. By changing the voltage on this winding, you can adjust the output voltage of the generator. This is done by a special device, a relay - a regulator.
Most modern generators have a built-in voltage regulator (5) that is mounted on the stator and has terminals for connecting voltage and graphite brushes for contact with current collectors of the field winding. Bearings (1) and (3) are designed to provide ease of rotation and centering of the rotor inside the stator. During operation, the stator windings produce alternating voltage, so the car's generator is equipped with rectifier diodes, which are made on a separate panel and are attached to the stator housing. Since there are three windings, six diodes are used for rectification (three-phase rectification bridge circuit).
A pulley is attached to the shaft of the automobile generator to transmit torque from the engine. The stator, together with the side covers, forms a single structure and is attached to the motor housing with the possibility of adjusting the position.
Main malfunctions
The main faults are listed below in order of frequency of occurrence:
- weakening the tension of the alternator belt;
- failure of the voltage regulator;
- wear or sticking of brushes;
- breakage or short circuit of the windings;
- breakdown of the rectifier diodes.
The need to diagnose the generator arises in the event of a mismatch between the voltage of the on-board network in the car to the required value, or its complete absence. It often happens that with a small load, the voltage is normal, and with an increase in the current consumption, the voltage drops. Before checking the car's alternator, the first step is to check the tension of the alternator belt. To check, it is enough to press the belt with your finger and measure the amount of deflection. It should be no more than 10 ... 15 mm.
A larger deflection will cause that when the load on the generator increases, the friction force between the belt and the pulley will not be enough to fully transfer torque from the engine, and the belt will slip. Use the adjusting screw to move the generator stator away from the engine. If the belt tension is normal, then the car generator requires a deeper check.
An increase in voltage while the engine is running may indicate a malfunction of the voltage regulator.
Checking the car generator
To check the generator in a car at home, you need a measuring device - a tester, which has the functions of measuring voltage and resistance. Now the most common and low cost digital testers (Figure below).
Digital tester for measurements in electrical equipment
Such a device is sufficient for carrying out almost any measurement in the electrical equipment of a car. In addition, the performance of the devices is carried out without observing the polarity of connecting the probes.
Some measurements are taken with the engine running.
In this case, the operation of the generator is checked only with the battery connected. Without a battery, the voltage regulator will not function normally, and an overvoltage will be supplied to the car's on-board network, which will most likely lead to failure of the on-board controller and other electronics.
Below will be described how to check the generator with a multimeter. First of all, you need to measure the voltage at the battery terminals with a tester with the engine off. After the engine is started, the voltage should increase and reach the nominal value, which means the battery is charging. Otherwise, the generator must be dismantled and completely checked. It is possible to check the car alternator without removing it from the car, but this technique varies significantly depending on the brand of car and generator.
Checking the dismantled generator includes:
- visual inspection for rubbing of insulation, burning of wires, condition of brushes;
- checking the resistance of the stator and rotor windings;
- performance of rectifier diodes;
- performance of the voltage regulator (relay - regulator).
When examining the removed generator, first of all, it is necessary to make sure that there are no mechanical damage to the windings, the reliability of the terminal connections, and the integrity of the diode leads. The brushes of the relay-regulator must move freely in their guides and not be chipped.
The field winding slip rings on the rotor shaft must not have burrs or burn marks. Strong soot and traces of burnt metal on the rings indicate a short circuit between the turns of the rotor winding.
The stator and rotor windings are checked with an ohmmeter. The winding resistance should be a few ohms. The field winding is checked by measuring the resistance between slip rings on the rotor shaft. Normal resistance should be 5 ... 10 ohms. The stator winding is checked only after disconnecting all terminals. There should be three free wires on the winding (on new generators) or four (terminal from the winding connection point on old generators). The automotive stator must have winding resistance within 5-15 ohms between the beginning of the winding and the connection point and 10..30 ohms between the ends of adjacent windings. The main thing here is that the stator has the same value when measuring all three windings. A difference of more than 20% indicates a malfunction of one of the windings.
When measuring small resistance values, the probes of the device introduce an error. For accuracy, you must first connect the probes to each other and determine their resistance. Usually it is 0.2 ... 1 ohm. This value should be taken into account in further measurements.
Next, you should check the condition of the rectifier bridge diodes. Most car alternators use two types of diodes. Some of them have a negative terminal on the body and a positive free one. Others are done the other way around. This is done for the convenience of mounting diodes on cooling plates - radiators (Fig. below).
Car alternator diode bridge
It doesn't matter for measurements. Diodes are measured when the ohmmeter switch is set to measure diodes. If there is no such provision or a pointer instrument is used, then the measurement limit is set for resistance measurements of 200 ... 1000 kOhm.
The rectifier bridge must be disconnected from the stator. The operation of the diodes is checked by comparing the resistances with direct and reverse polarity of the probes of the device. The values must differ by several times. The ideal case is when the device shows a complete break in one polarity and the measured values \u200b\u200bare the same for all diodes. If in both positions of the probes the device shows zero resistance or its complete absence, then such an automobile diode bridge needs to be replaced.
In addition to checking the resistance, it is also necessary to check the condition of the insulation of the windings. To do this, the measurement limit of the device is set to measure the maximum resistance, then one of the probes is applied to the generator housing (on the stator), and the other probe to the winding under test. The readings of the device should show a very high resistance (the arrow should not deviate on the arrows).
More precisely, the insulation resistance can be checked using a special device (megger) used to measure electrical cables or cable communication lines.
Two wires are removed from the lamp socket, one of which is connected to the generator case, since the stator has a metal case, and the second is connected to a regular household outlet. The second terminal of the socket is connected to the tested winding. The absence of the glow of the lamp indicates the normal state of the insulation.
Checking the voltage regulator
You can check the voltage regulator (relay-regulator) using an external regulated power supply 12 ... 16 V (Fig. below).
Scheme for checking the relay-regulator
To check, an adjustable source is connected to the relay with a plus to the output terminal, and a minus to ground. A 12 V car lamp is connected to the brushes. If the power supply voltage is more than 14.5 V, the lamp should go out. A faulty voltage regulator needs to be replaced. Relay - the old type of regulator is subject to adjustment.
Video. Quick check
Quite often it happens that malfunctions occur in a car with a warm engine. This can be due both to the linear expansion of the metal with temperature (short circuit of the windings), and to the properties of semiconductors (faults in the rectifier diodes). In this case, it is recommended to check the operation of the generator directly on the car. The question of how to check the generator after heating is solved by warming up with a building hair dryer to the possible operating temperature.
Repairing a car generator at home requires a lot of skill and, in most cases, is impractical. Much easier to replace it completely. The exceptions are the automotive relay-regulator and the diode bridge.
During the operation of the car, sooner or later, it becomes necessary to check the correct operation of the generator. The best way to test the alternator and troubleshoot is to visit an auto electrician. However, any motorist is able to diagnose the simplest malfunctions on their own. To do this, you need a simple tester, also known as a “multimeter”.
First of all, we check the relay-regulator of the generator, in automotive slang - a “pill”. The stability of the voltage in the vehicle's on-board network depends on the correctness of its operation. We transfer the tester to the “Measuring DC voltage” mode and start the engine. By connecting the tester to the battery terminals, we measure the voltage at idle. It should be in the range of 4-14.2 volts. Gradually increasing the engine speed, we monitor the change in voltage. Fluctuations should not exceed +\- 0.5 volts. If the measured values go beyond the specified limit, the regulator relay is not working properly and must be replaced. It is also necessary to check the rectifier bridge of the generator. It consists of six semiconductor diodes. Check the DC conductance of each diode. We transfer the multimeter to the “Continuity” position and, in turn, touch the probes to the contacts of each diode. If the tester beeps, the diode passes current through itself, if not, it does not pass. Those. the diode in one position of the polarity of the probes should pass, in the other it should not. If at least one diode “rings” in both directions or does not “ring” in either direction, then the diode bridge must be replaced as an assembly.
As you know, the generator unit is an integral part of any modern car. Thanks to this device, the battery is charged while driving, as well as powering all electrical equipment. But like any other mechanism, the generator can fail for various reasons. In this article we will tell you in which cases it is necessary to repair the generator armature and how it is diagnosed.
[ Hide ]
Description of the generator armature
Before you test a node, read the basic information. The anchor consists of the following elements:
- contact rings;
- brush knot;
- collector;
- excitation winding;
- core.
The core of the device includes several sheets made of electrical steel, their thickness should be 0.5 mm. The core is mounted in the shaft, but if the armature diameter is very large, then in a cylindrical sleeve. As for the collector, it consists of copper plates, the number of which may vary depending on the design. The collector is assembled separately, after which it is pressed into the shaft by means of an insulating sleeve.
The winding is made in the form of several sections, their ends are mounted in special protrusions on the collector plates. With the help of the last section, the windings are connected to each other in series, forming a closed circuit. Windings can be wave or loop. In the first, the conclusions of the sections are connected to the collector node, and they are connected to each other in a wave-like manner. In loop devices, the leads are connected to the collector plates, and they are connected to each other directly on the collector.
Operating principle
The armature of the generator unit rotates as a result of the impact of the bearing shields, as well as the bearings themselves, mounted on the shaft. The shield itself, which is located next to the collector, is called the front. Behind this shield, on the shaft, there is a winglet designed to cool the device. To ensure the flow of air, as well as to remove heat, there are special openings in the shields, which are closed with protective covers with grids. There are also holes in the front shield, but they are necessary for servicing the constituent elements of the device.
The armature of the device is connected to the network through a brush assembly. The elements themselves are located on special holders, which are fixed on the so-called fingers. These fingers are located on a traverse, which, in turn, is fixed to the front shield or frame, depending on the design. The pressure of the brush elements can be adjusted, special springs are provided for this.
The number of so-called brush fingers corresponds to the number of poles, with one half of them having positive polarity and the other half negative. In general, the brush assembly divides the winding into several parallel branches, their number may also vary depending on the type of winding (the author of the video is Volodymyr Zagryvyi / Vladimir Zagryvyi).
The on-board network of the vehicle is connected to the generator unit through a special terminal box, where there is a board with terminal marks on the windings. To ensure the lifting or movement of the generator unit, there is a corresponding bolt on the upper part of the bed. A plate is installed on its body, where the manufacturer is indicated, as well as the main technical data about the device. One of the main disadvantages of the generator device is the rather high complexity, as well as the too weak strength of the brush assembly, as a result of which the device needs periodic diagnostics and maintenance.
Typical malfunctions
There is an opinion among our compatriots that one of the main malfunctions of the anchor is the lack of resistance. It should be noted that the resistance is checked on the rotor winding, and the rotor, in turn, can be installed instead of the inductor, and the stator will stand instead of the armature. This is done in order to provide higher power, so the resistance can only be diagnosed on the rotor.
As for the anchor, it is characterized by such malfunctions:
- most often do-it-yourself repair of the generator armature is carried out as a result of slip rings wear;
- also, the need to repair the assembly may appear as a result of failure of the shaft bearing;
- not so often, but still the problem of a short circuit of the winding occurs.
It should also be noted that there are breakdowns that cannot be repaired:
- collector wear up to a diameter of 8.6 cm;
- keyway wear.
Self-diagnosis
So we smoothly approached the issue of verification. If you do not know how to check the performance of the node in your car, then first of all make a visual diagnosis of the state of the device. If the check showed that there is no external damage, then a more thorough diagnosis is needed. Initially, you should check the winding for insulation failure; for dialing, you will need a multimeter or a test lamp.
Before checking, one wire from the lamp must be connected to the armature shaft, and the other in turn to touch the collector plates. At the same time, please note that when checking, the wire lugs must be securely insulated. In the event that the armature winding is shorted to ground, the light should flash.
To test the turn-to-turn circuit, you will need a special inductive device. The core of the device in this case is made of metal, and the coil is powered by the use of industrial alternating voltage. The anchor is installed in the prism of the core, after which it must be rotated around the axis, and an iron plate is connected to the metal. In the absence of short circuits, there will be no current in the winding (the author of the video is the Ramanych channel).
If there is a short circuit, then an electromotive force will be fixed in the closed turns. In this case, the alternating voltage will contribute to the formation of another magnetic field, so if it is, then vibration will appear in the iron plates connected to the armature. The presence of vibration may indicate that there is a short circuit in the turns, if this is the case, then the only option to solve the problem is to rewind the armature.
Ways to eliminate breakdowns and defects of the anchor
If the surface of the shaft of the mechanism is worn, then the knurling procedure will correct such a problem. The mechanism itself is mounted in a lathe, and the worn necks are processed. Their diameter will increase due to the iron that comes out of the formed depressions. When the processing is completed, the harnesses must be sanded so that their dimensions correspond to those to be used.
When the collector is worn, its defective elements must also be eliminated. This component is subject to turning, after which the insulation is cut into the plates to a distance of 0.8 mm. In this case, the groove width should be no more than 0.6 mm; a milling machine is used to cut through the insulation.
After milling, the steel of the anchor must be treated with a special nitroglyphthalic varnish, and the winding with insulating one. In this case, the drying of these elements should be carried out at a temperature of about 110 degrees for 10 hours. Not every service station will provide such conditions for repair, so it will not work to repair the anchor at home.
Video "How to repair an anchor using a lathe"
A visual instruction for repairing an anchor element using special equipment is shown in the video below (the author of the video is Volodymyr Zagryvyi / Vladimir Zagryvyi).
