Transfer the asynchronous one to the generator without rewinding. Homemade asynchronous generator. Difference from synchronous generator

The article describes how to build a three-phase (single-phase) 220/380 V generator based on an asynchronous electric motor alternating current. A three-phase asynchronous electric motor, invented at the end of the 19th century by the Russian electrical engineer M.O. Dolivo-Dobrovolsky, has now become predominantly widespread both in industry and in agriculture, as well as in everyday life.

Asynchronous electric motors are the simplest and most reliable to operate. Therefore, in all cases where this is permissible under the conditions of the electric drive and there is no need for reactive power compensation, asynchronous AC motors should be used.

There are two main types of asynchronous motors: with squirrel-cage rotor and with phase rotor. An asynchronous squirrel-cage electric motor consists of a stationary part - the stator and a moving part - the rotor, rotating in bearings mounted in two motor shields. The stator and rotor cores are made of separate electrical steel sheets insulated from one another. A winding made of insulated wire. A rod winding is placed into the grooves of the rotor core or molten aluminum is poured. Jumper rings short-circuit the rotor winding at the ends (hence the name short-circuited). Unlike a squirrel-cage rotor, a winding made like a stator winding is placed in the slots of a phase-wound rotor. The ends of the winding are brought to slip rings mounted on the shaft. Brushes slide along the rings, connecting the winding to a starting or control rheostat.

Asynchronous electric motors with a wound rotor are more expensive devices, require qualified maintenance, are less reliable, and therefore are used only in those industries where they cannot be done without them. For this reason, they are not very common, and we will not consider them further.

A current flows through the stator winding connected to a three-phase circuit, creating a rotating magnetic field. The magnetic field lines of the rotating stator field cross the rotor winding bars and induce in them electromotive force(EMF). Under the influence of this EMF, current flows in the short-circuited rotor rods. Magnetic fluxes arise around the rods, creating a general magnetic field of the rotor, which, interacting with the rotating magnetic field of the stator, creates a force causing the rotor to rotate in the direction of rotation magnetic field stator.

The rotor rotation frequency is slightly less than the rotation frequency of the magnetic field created by the stator winding. This indicator is characterized by slip S and is for most engines in the range from 2 to 10%.

Most commonly used in industrial installations three-phase asynchronous electric motors, which are produced in the form of unified series. These include the single 4A series with a rated power range from 0.06 to 400 kW, the machines of which are highly reliable, have good performance and meet world standards.

Autonomous asynchronous generators are three-phase machines that convert the mechanical energy of the prime mover into alternating current electrical energy. Their undoubted advantage over other types of generators is the absence of a commutator-brush mechanism and, as a consequence, greater durability and reliability.

Operation of an asynchronous electric motor in generator mode

If an asynchronous motor disconnected from the network is set into rotation from any primary motor, then, in accordance with the principle of reversibility of electrical machines, when a synchronous rotation speed is reached, a certain EMF is formed at the terminals of the stator winding under the influence of a residual magnetic field. If you now connect a battery of capacitors C to the terminals of the stator winding, then a leading current will flow in the stator windings. capacitive current, which in this case is magnetizing.

The battery capacity C must exceed a certain critical value C0, depending on the parameters of the autonomous asynchronous generator: only in this case does the generator self-excite and a three-phase symmetrical voltage system is installed on the stator windings. The voltage value ultimately depends on the characteristics of the machine and the capacitance of the capacitors. Thus, an asynchronous squirrel-cage electric motor can be converted into asynchronous generator.

Standard circuit for connecting an asynchronous electric motor as a generator.

You can select the container so that Rated voltage and the power of the asynchronous generator were equal to the voltage and power, respectively, when operating as an electric motor.

Table 1 shows the capacitances of the capacitors for excitation of asynchronous generators (U=380 V, 750...1500 rpm). Here reactive power Q is determined by the formula:

Q = 0.314 U 2 C 10 -6 ,

where C is the capacitance of the capacitors, μF.

As can be seen from the above data, the inductive load on the asynchronous generator, which reduces the power factor, causes a sharp increase in the required capacity. To maintain a constant voltage with increasing load, it is necessary to increase the capacitor capacity, that is, connect additional capacitors. This circumstance must be considered as a disadvantage of the asynchronous generator.

The rotation frequency of an asynchronous generator in normal mode must exceed the asynchronous one by a slip value S = 2...10%, and correspond to the synchronous frequency. Not fulfilling this condition will lead to the fact that the frequency of the generated voltage may differ from the industrial frequency of 50 Hz, which will lead to unstable operation of frequency-dependent consumers of electricity: electric pumps, washing machines, devices with transformer input.

A decrease in the generated frequency is especially dangerous, since in this case the inductive resistance of the windings of electric motors and transformers decreases, which can cause their increased heating and premature failure.

An ordinary asynchronous squirrel-cage electric motor of appropriate power can be used as an asynchronous generator without any modifications. The power of the electric motor-generator is determined by the power of the connected devices. The most energy-intensive of them are:

• household welding transformers;
• electric saws, electric jointers, grain crushers (power 0.3...3 kW);
• electric furnaces of the "Rossiyanka" and "Dream" types with a power of up to 2 kW;
• electric irons (power 850…1000 W).

I would especially like to dwell on the operation of household welding transformers. Their connection to an autonomous source of electricity is most desirable, because when working from industrial network they create a number of inconveniences for other electricity consumers.

If a household welding transformer is designed to work with electrodes with a diameter of 2...3 mm, then it full power is approximately 4...6 kW, the power of the asynchronous generator to power it should be within 5...7 kW. If a household welding transformer allows working with electrodes with a diameter of 4 mm, then in the heaviest mode - “cutting” metal, the total power consumed by it can reach 10...12 kW, respectively, the power of an asynchronous generator should be within 11...13 kW.

As a three-phase bank of capacitors, it is good to use so-called reactive power compensators, designed to improve cosφ in industrial lighting networks. Their typical designation: KM1-0.22-4.5-3U3 or KM2-0.22-9-3U3, which is deciphered as follows. KM - impregnated cosine capacitors mineral oil, the first number is the size (1 or 2), then the voltage (0.22 kV), power (4.5 or 9 kvar), then the number 3 or 2 means three-phase or single-phase version, U3 (moderate climate of the third category).

When self-made batteries, you should use capacitors such as MBGO, MBGP, MBGT, K-42-4, etc. for an operating voltage of at least 600 V. Electrolytic capacitors cannot be used.

The option discussed above for connecting a three-phase electric motor as a generator can be considered classic, but not the only one. There are other methods that have proven themselves just as well in practice. For example, when a bank of capacitors is connected to one or two windings of an electric motor generator.

Two-phase mode of an asynchronous generator.

Fig.2 Two-phase mode of an asynchronous generator.

This scheme should be used when there is no need to obtain three-phase voltage. This inclusion option reduces working capacity capacitors, reduces the load on the primary mechanical engine in idle mode, etc. saves "precious" fuel.

As low-power generators that produce an alternating single-phase voltage of 220 V, you can use single-phase asynchronous squirrel-cage electric motors for household use: from washing machines such as "Oka", "Volga", watering pumps "Agidel", "BTsN", etc. Their capacitor battery can connect in parallel to the working winding, or use an existing one phase shifting capacitor, connected to starting winding. The capacity of this capacitor may need to be increased slightly. Its value will be determined by the nature of the load connected to the generator: for active loads (electric furnaces, lighting bulbs, electric soldering irons) it is required small capacity, inductive (electric motors, TVs, refrigerators) - more.

Fig. 3 Low-power single-phase generator asynchronous motor.

Now a few words about the primary mechanical engine, which will drive the generator. As you know, any transformation of energy is associated with its inevitable losses. Their value is determined by the efficiency of the device. Therefore, the power of a mechanical motor must exceed the power of an asynchronous generator by 50...100%. For example, with an asynchronous generator power of 5 kW, the power of a mechanical motor should be 7.5...10 kW. Using a transmission mechanism, the speed of the mechanical engine and the generator are matched so that the operating mode of the generator is set at the average speed of the mechanical engine. If necessary, you can briefly increase the generator power by increasing the speed of the mechanical engine.

Each autonomous power plant must contain the required minimum attachments: AC voltmeter (with a scale up to 500 V), frequency meter (preferably) and three switches. One switch connects the load to the generator, the other two switch the excitation circuit. The presence of switches in the excitation circuit makes it easier to start a mechanical engine, and also allows you to quickly reduce the temperature of the generator windings; after completion of work, the rotor of the unexcited generator is rotated for some time by the mechanical engine. This procedure extends the active life of the generator windings.

If the generator is used to power equipment that is normally connected to the AC mains (for example, residential lighting, household electrical appliances), then it is necessary to provide a two-phase switch, which will disconnect this equipment from the industrial network during generator operation. It is necessary to disconnect both wires: “phase” and “zero”.

In conclusion, some general advice.

1. The alternator is a hazardous device. Use 380 V only when absolutely necessary; in all other cases, use 220 V.

2. According to safety requirements, the electric generator must be equipped with grounding.

3. Pay attention to the thermal mode of the generator. He "does not like" idling. Reduce thermal load possible by more careful selection of the capacitance of the exciting capacitors.

4. Don't go wrong with power electric current produced by the generator. If during work three-phase generator If one phase is used, its power will be 1/3 total power generator, if two phases are 2/3 of the total generator power.

5. The frequency of the alternating current produced by the generator can be indirectly controlled by the output voltage, which in the “no-load” mode should be 4...6% higher than the industrial value of 220/380 V.

Power sources are divided into synchronous and asynchronous depending on the type of generator. In electrical engineering, according to the laws of physics, there is a principle of energy reversibility: electric cars, which can convert electrical energy into mechanical energy, can also perform the reverse transformation. An asynchronous generator operates on this principle: it is capable of converting the mechanical energy of rotor rotation into electric current on the stator winding. It is used for voltages of 220 and 380 V.

Type of asynchronous generator

In the generator operating mode, the sign of the slip changes, and asynchronous motors generate electrical energy.

Application

• Generators have found application as traction electric motors at transport infrastructure facilities in machines with rheostatic and regenerative braking, as well as in agriculture in devices where there is no need for reactive power compensation and high requirements for the quality of supplied electricity (where small voltage surges are possible, i.e. there is no parameter regulator).
• For household needs asynchronous generators are used as the engine of autonomous power plants, which are driven by natural forces: the energy of falling water, wind power, etc.
• Another application is to use a generator as a battery charger.
• For power supply of welding units.
• Security uninterruptible power supply especially important objects: refrigerators with medicines, etc.

This device is used for industrial purposes

It is theoretically possible to convert an asynchronous motor into an asynchronous generator. To complete the task you need:

• clearly understand what current is;
• know the physics of transformation mechanical energy to electrical;
• create everything the necessary conditions for the appearance of electric current on the stator winding.

Asynchronous generator device

Main components of an asynchronous generator:

• A rotor is a rotating element on which an emf is generated. Type of execution – short-circuited. Conductive surfaces are made of aluminum.
• Cable input is necessary to release the received electricity.
• A temperature sensor for the generator winding is required to continuously monitor the temperature on this winding.
• Sealed flanges are designed to seal the connection of parts.
• A stator on whose windings electricity is generated during the process.
• The winding can be of two types: single-phase and three-phase (for voltages of 220 and 380 V), placed on the surface of the stator in the form of a star. 3 points are connected to each other, 3 others are connected to slip rings.
• The slip rings have no electrical connection with each other and are fixed to the rotor shaft.
• Brushes are needed as a regulator; with their help, a three-phase rheostat is started, due to which the resistance of the rotor winding can be controlled.
• The short circuit is used to force the rheostat to stop.

Principle of operation

As the rotor blades rotate, an electric current begins to appear on the conductive part. The resulting magnetic field induces two types of stator windings AC voltage– single-phase and three-phase.

The parameters of the generated energy are adjusted by changing the load on the stator. There is no regulator in the circuit, because Structurally, the device cannot be equipped with this unit: there is no electrical connection between the rotor and stator.

In what cases is it necessary to use asynchronous devices:

• difficult operating conditions for equipment – ​​dust;
• there are no special requirements for the quality of the converted energy (frequency and voltage);
• there is no possibility of installing a synchronous machine;
• limited budget of the facility;
• there is a possibility of overloads in transition process work.

Asynchronous devices do not tolerate frequent overloads during operation. When working with excessive power, protection is triggered. Restarting devices has Negative influence on the economic effect of the installation.

Because There is no parameter control, connection is required measuring instruments.

To ensure correct operation of the system and avoid premature repairs, it is necessary to calculate the generator power based on the expected load of the facility.

Operating principle in two-phase mode an asynchronous generator is used for cases that do not require the generation of three-phase voltage.

Advantages:

• small working capacity;
• low loads in idle mode, and as a result, savings in primary energy (the resource that drives the rotor).

Flaws:

• There is no voltage regulator.

Low-power generators 220 V

Asynchronous electric motors with squirrel-cage rotors from washing machines are used as donor devices. household vacuum cleaners, electrical watering devices and similar ones, in which capacitor batteries are connected in a circuit parallel to the working winding. To increase operating efficiency, the capacitor capacity is increased: to a lesser extent for active loads (lamps, soldering irons), and to a greater extent for inductive loads (for example, refrigerators, TVs, etc.).

• The power of the primary device is selected to be 50..100% greater than the power consumed by the asynchronous generator. This is necessary to reduce losses and increase process efficiency. Increased efficiency is achieved by permanently or briefly increasing the speed of a mechanical element.
• Since the circuit does not contain a current regulator, stable operation of the installation requires constant monitoring of the parameters, i.e. the presence of a device for measuring frequency (tachometer), voltage (voltmeter) and a set of switches (for connecting the load to the generator, and two for switching the excitation circuit. This circuit simplifies the start-up and increases the stability of the electrical equipment.
• If connected to a generator household network lighting, it is necessary to provide a two-phase switch in the electrical circuit, which in this case will disconnect the electric lighting from the stationary network.

Single-phase switches for disconnecting are prohibited in this case, because it is necessary to disconnect the phase and neutral wires.

Installation efficiency

Before carrying out reconstruction, it is necessary to take into account the scale of the economic effect of the new equipment and the feasibility of the procedure.

Device advantages:

1. Low cost of electricity: conversion requires the presence of a magnetic field that generates an electric current.
2. The current contains a small number of higher harmonics: small losses due to its own heating, the formation of magnetic fields, etc.
3. High reliability.
4. No excitation circuit.
5. Cheapness of ready-made models.
6. Possibility of converting a simple asynchronous motor into a generator.
7. The absence of a commutator-brush mechanism in the device design, which increases the service life.
8. No need for maintenance of capacitor banks.

Flaws:

1. Inability to generate industrial frequency of the generated current.
2. There is no network parameter control.
3. The need to include rectifiers in the operating circuit.
4. An inductive load requires an increase in the applied capacitance requirement. Consequently, the need to connect additional capacitor elements to the device circuit increases. Which subsequently increases the cost of installation.
5. The device is no less technically complex than synchronous generators.
6. High sensitivity to load changes. Because To operate the device, a capacitor is used, which takes energy (traditional generators use batteries that have a power reserve); if the load increases, there may not be enough electricity for recharging and generation will stop. To prevent this phenomenon, batteries with variable capacity depending on the load are used. Application of this equipment economically feasible for large facilities.

Engine conversion

Principle converting the engine into a simple asynchronous generator:

1. To upgrade, you will need a motor from a washing machine.
2. Reduce the thickness of the core walls. For this it is necessary to lathe grind 2 mm over the entire surface. Make holes (non-through) no more than 5mm deep.
3. Make a strip from a thin sheet of metal or tin, the dimensions corresponding to the dimensions of the rotor.
4. Install neodymium magnets in the resulting free area in an amount of at least 8 pieces. Secure with superglue.

The magnets must be pressed against the surface until they harden completely, otherwise they will move. It is recommended to use glasses to prevent glue from getting into your eyes if the magnet slips out.

1. Cover the rotor on all sides with thick paper and secure the edges with tape.
2. Effectively seal the end part of the rotor with mastic.
3. Fill the free space between the magnetic elements epoxy resin through a hole made in the paper.
4. After the resin has hardened, remove the layer of paper.
5. Sand the surface of the rotor with sandpaper; if available, you can use a Dremel.
6. Connect the motor to the working winding with two wires. Remove all unused wires.
7. If necessary, replace the bearings with new ones.
8. Install the current rectifier and charging controller.

Testing the assembled device

When using an asynchronous generator, like other electrical devices, you must follow the safety rules:

• The device must be protected from mechanical influences and weather conditions.
• It is recommended to manufacture a special protective casing for the assembled generator.
• For correct operation, constant monitoring of device parameters (voltage, frequency) is necessary. There is no current regulator. Installing measuring instruments will allow you to monitor the effectiveness of the autonomous system.
• For safety reasons, it is recommended to use a homemade generator at a voltage of 0.23 kV.
• The device must be connected to a grounding circuit.
• Long periods of idling should be avoided.
• It is prohibited to allow the equipment to overheat.
• The generator must be equipped with an on/off button to optimize operation.

If you do not have basic knowledge of electrical engineering, experts strongly recommend purchasing a factory-made generator.

Reconstruction of an asynchronous motor

The process consists of three stages:

1. Connecting capacitor banks to terminals. After this, the magnetization process begins on the winding, which is caused by the movement of the leading current.
2. Self-excitation of the device. Occurs when correct selection capacitor capacities.
3. Obtaining final voltage values. Depends on technical characteristics devices, type and capacitance of capacitors.

Modernization of an asynchronous motor

At correct execution actions, you can obtain a generator with the characteristics of an asynchronous motor.

Video

Asynchronous generators – useful thing V household. More powerful devices They may well serve as autonomous power plants that will ensure normal voltage and frequency parameters of the network.

One of the first generators with an AC exciter

It is economically feasible to re-equip an unused asynchronous electric motor that is known to be working. Only in this case will there be an economic effect, in contrast to the purchase of a new device.

Despite the rather labor-intensive principle of modernization, the missing regulator of network parameters, homemade asynchronous generators are good decision to minimize financial costs for electricity in conditions of constantly rising energy prices.

An asynchronous or induction type generator is a special type of device that uses alternating current and has the ability to generate electricity. Main feature is the making of fairly fast turns that the rotor makes; in terms of the speed of rotation of this element, it is significantly superior to the synchronous variety.

One of the main advantages is the ability to use this device without significant circuit modifications or lengthy setup.

A single-phase type of induction generator can be connected by applying the required voltage to it, this will require connecting it to a power source. However, a number of models produce self-excitation; this ability allows them to function in a mode independent of any external sources.

This is accomplished by sequentially bringing the capacitors into working condition.

Generator circuit from an asynchronous motor

In virtually any car electric type, designed as a generator, there are 2 different active windings, without which the operation of the device is impossible:

1. Field winding, which is located on a special anchor.
2. Stator winding, which is responsible for the formation of electric current, this process happens inside her.

In order to visualize and more accurately understand all the processes occurring during the operation of the generator, the most the best option Let's take a closer look at how it works:

1. Voltage, which is supplied from a battery or any other source, creates a magnetic field in the armature winding.
2. Rotating device elements together with a magnetic field it is possible to realize different ways, including manually.
3. A magnetic field, rotating at a certain speed, generates electromagnetic induction, due to which an electric current appears in the winding.
4. The vast majority of schemes used today does not have the ability to provide voltage to the armature winding, this is due to the presence of a squirrel-cage rotor in the design. Therefore, regardless of the speed and time of rotation of the shaft, the power supply devices will still be de-energized.

When converting an engine into a generator, the independent creation of a moving magnetic field is one of the main and mandatory conditions.

Generator device

Before taking any action to remodelinto the generator, you need to understand the structure of this machine, which looks like this:

1. Stator, which is equipped with a 3-phase network winding located on its working surface.
2. Winding organized in such a way that it resembles a star in shape: 3 initial elements are connected to each other, and 3 opposite sides are connected to slip rings that do not have any points of contact with each other.
3. Slip rings have reliable fastening to the rotor shaft.
4. In design There are special brushes that do not make any independent movements, but help turn on the rheostat with three phases. This allows you to change the resistance parameters of the winding located on the rotor.
5. Often, in internal structure There is such an element as an automatic short-circuiter, which is necessary to short-circuit the winding and stop the rheostat, which is in working condition.
6. One more additional element generator devices may be special device, which separates the brushes and slip rings at the moment when they go through the closing stage. This measure helps to significantly reduce friction losses.

Making a generator from an engine

In fact, any asynchronous electric motor can be with my own hands converted into a device that functions like a generator, which can then be used in everyday life. Even an engine taken from an old-style washing machine or any other household equipment may be suitable for this purpose.

In order for this process to be successfully implemented, it is recommended to adhere to the following algorithm of actions:

1. Remove the engine core layer, due to which a depression will be formed in its structure. This can be done on a lathe; it is recommended to remove 2 mm. throughout the core and make additional holes with a depth of about 5 mm.
2. Take dimensions from the resulting rotor, after which a template in the form of a strip is made from tin material, which will correspond to the dimensions of the device.
3. Install in the resulting free space there are neodymium magnets, which must be purchased in advance. Each pole will require at least 8 magnetic elements.
4. Fixation of magnets can be done using universal superglue, but it must be taken into account that when approaching the surface of the rotor they will change their position, so they must be held firmly with your hands until each element is glued. Additionally, it is recommended to use safety glasses during this process to avoid any glue splashing into your eyes.
5. Wrap the rotor plain paper and the tape that will be needed to secure it.
6. The end part of the rotor cover with plasticine, which will ensure sealing of the device.
7. After completed actions it is necessary to process the free cavities between the magnetic elements. To do this, the remaining between the magnets free space must be filled with epoxy resin. The most convenient way would be to cut a special hole in the shell, transform it into a neck and seal the borders with plasticine. You can pour resin inside.
8. Wait until it hardens completely filled with resin, after which the protective paper shell can be removed.
9. The rotor must be fixed using a machine or a vice so that it can be processed, which consists of grinding the surface. For these purposes, you can use sandpaper with a medium grit setting.
10. Determine state and the purpose of the wires coming out of the engine. Two should lead to the working winding, the rest can be cut off so as not to get confused in the future.
11. Sometimes the rotation process is quite poor, most often the cause is old worn out and tight bearings, in which case they can be replaced with new ones.
12. Rectifier for generator can be assembled from special silicon, which are designed specifically for these purposes. You also don’t need a controller for charging; virtually all modern models are suitable.

After all the above steps have been completed, the process can be considered complete; the asynchronous motor has been converted into a generator of the same type.

Assessing the level of efficiency - is it profitable?

The generation of electric current by an electric motor is quite real and feasible in practice, the main question is how profitable is it?

The comparison is made primarily with a synchronous version of a similar device, which is missing electrical circuit excitation, but despite this fact, its structure and design are not simpler.

This is due to the presence of a capacitor bank, which is extremely difficult to technically an element that is missing from an asynchronous generator.

Main advantage asynchronous device is that the available capacitors do not require any maintenance, since all the energy is transferred from the magnetic field of the rotor and the current that is generated during the operation of the generator.

The electric current created during operation virtually does not have higher harmonics, which is another significant advantage.

Asynchronous devices do not have any other advantages besides those mentioned, but they do have a number of significant disadvantages:

1. During their operation there is no possibility of ensuring the nominal industrial parameters of the electric current generated by the generator.
2. High degree of sensitivity even to the slightest differences in workload parameters.
3. If the parameters are exceeded permissible loads to the generator, a lack of electricity will be detected, after which recharging will become impossible and the generation process will be stopped. To eliminate this drawback, batteries with significant capacity are often used, which have the ability to change their volume depending on the magnitude of the loads applied.

The electric current produced by an asynchronous generator is subject to frequent changes, the nature of which is unknown, it is random and cannot be explained in any way by scientific arguments.

The impossibility of taking into account and appropriate compensation for such changes explains the fact that such devices have not gained popularity and have not become particularly widespread in the most serious industries or household affairs.

Functioning of an asynchronous motor as a generator

In accordance with the principles on which all such machines operate, the operation of an induction motor after conversion into a generator occurs as follows:

1. After connecting the capacitors to the terminals, a number of processes occur on the stator windings. In particular, a leading current begins to move in the winding, which creates a magnetization effect.
2. Only if the capacitors match parameters of the required capacity, the device self-excites. This promotes a symmetrical 3-phase voltage system on the stator winding.
3. Final voltage value will depend on technical capabilities the machine used, as well as the capabilities of the capacitors used.

Thanks to the described actions, the process of converting a squirrel-cage asynchronous motor into a generator with similar characteristics occurs.

Application

In everyday life and in production, such generators are widely used in various fields and areas, but they are most in demand to perform the following functions:

1. Use as engines for , this is one of the most popular features. Many people make their own asynchronous generators to use them for these purposes.
2. Work as a hydroelectric power station with little output.
3. Providing food and electricity in a city apartment, private country house or separate household equipment.
4. Perform basic functions welding generator.
5. Uninterrupted equipment alternating current of individual consumers.

It is necessary to have certain skills and knowledge not only in the manufacture, but also in the operation of such machines; the following tips can help with this:

1. Any type of asynchronous generators Regardless of the area in which they are used, it is a dangerous device, for this reason it is recommended to isolate it.
2. During the manufacturing process of the device it is necessary to consider the installation of measuring instruments, since it will be necessary to obtain data on its functioning and operating parameters.
3. Availability of special buttons, with which you can control the device, greatly facilitates the operation process.
4. Grounding is mandatory requirement, which must be implemented before operating the generator.
5. During work, The efficiency of an asynchronous device can periodically decrease by 30-50%; it is not possible to overcome the occurrence of this problem, since this process is an integral part of energy conversion.

In order for an asynchronous motor to become an alternating current generator, a magnetic field must be formed inside it; this can be done by placing it on the motor rotor permanent magnets. The whole alteration is both simple and complex at the same time.

First you need to select a suitable engine that is most suitable for working as a low-speed generator. These are multi-pole asynchronous motors, 6 and 8-pole, low-speed motors are well suited, with maximum speed in engine mode no more than 1350 rpm. Such engines have greatest number poles and teeth on the stator.

Next, you need to disassemble the engine and remove the armature-rotor, which must be ground on a machine to a certain size for gluing magnets. Neodymium magnets, usually small round magnets are glued. Now I will try to tell you how and how many magnets to glue.

First you need to find out how many poles your motor has, but it is quite difficult to understand this from the winding without the appropriate experience, so it is better to read the number of poles on the motor marking, if of course it is available, although in most cases it is. Below is an example of engine markings and a description of the markings.

By engine brand. For 3-phase: Motor type Power, kW Voltage, V Rotation speed, (sync.), rpm Efficiency, % Weight, kg

For example: DAF3 400-6-10 UHL1 400 6000 600 93.7 4580 Engine designation: D - engine; A - asynchronous; F - with wound rotor; 3 - closed version; 400 - power, kW; b - voltage, kV; 10 - number of poles; UHL - Climatic performance; 1 - accommodation category.

It happens that engines are not of our production, as in the photo above, and the markings are unclear, or the markings are simply not readable. Then there is only one method left, this is to count how many teeth you have on the stator and how many teeth one coil occupies. If, for example, the coil takes up 4 teeth, and there are only 24 of them, then your motor is six-pole.

The number of stator poles needs to be known in order to determine the number of poles when gluing magnets to the rotor. This quantity is usually equal, that is, if there are 6 stator poles, then the magnets must be glued with alternating poles in the amount of 6, SNSNSN.

Now that the number of poles is known, we need to calculate the number of magnets for the rotor. To do this, you need to calculate the circumference of the rotor using the simple formula 2nR where n=3.14. That is, we multiply 3.14 by 2 and by the radius of the rotor, we get the circumference. Next, we measure our rotor along the length of the iron, which is in an aluminum mandrel. Afterwards, you can draw the resulting strip with its length and width, you can do it on a computer and then print it out.

You need to decide on the thickness of the magnets, it is approximately equal to 10-15% of the rotor diameter, for example, if the rotor is 60mm, then magnets need to be 5-7mm thick. For this purpose, magnets are usually bought round. If the rotor is approximately 6 cm in diameter, then the magnets can be 6-10 mm high. Having decided which magnets to use, on the template the length of which is equal to the length of the circle

An example of calculating magnets for a rotor, for example, the diameter of the rotor is 60 cm, we calculate the circumference = 188 cm. We divide the length by the number of poles, in this case by 6, and we get 6 sections, in each section the magnets are glued with the same pole. But that is not all. Now you need to calculate how many magnets will fit into one pole in order to evenly distribute them along the pole. For example width round magnet 1cm, the distance between the magnets is about 2-3mm, which means 10mm +3=13mm.

We divide the length of the circle into 6 parts = 31mm, this is the width of one pole along the length of the rotor circumference, and the width of the pole along the iron, let’s say 60mm. This means the pole area is 60 by 31 mm. This turns out to be 8 in 2 rows of magnets per pole with a distance of 5mm between them. In this case, it is necessary to recalculate the number of magnets so that they fit as tightly as possible on the pole.

Here is an example with magnets 10mm wide, so the distance between them is 5mm. If you reduce the diameter of the magnets, for example, by 2 times, that is, 5 mm, then they will fill the pole more densely, as a result of which the magnetic field will increase due to the greater amount of the total mass of the magnet. There are already 5 rows of such magnets (5mm) and 10 in length, that is, 50 magnets per pole, and the total number per rotor is 300 pcs.

In order to reduce sticking, the template must be marked so that the displacement of the magnets when sticking is the width of one magnet; if the width of the magnet is 5mm, then the displacement is 5mm.

Now that you have decided on the magnets, you need to grind the rotor so that the magnets fit. If the height of the magnets is 6mm, then the diameter is ground down to 12+1mm, 1mm is a margin for hand bending. Magnets can be placed on the rotor in two ways.

The first method is to first make a mandrel in which holes for the magnets are drilled according to a template, after which the mandrel is put on the rotor, and the magnets are glued into the drilled holes. On the rotor, after grooving, you need to additionally grind down the separating aluminum strips between the iron to a depth equal to the height of the magnets. And fill the resulting grooves with annealed sawdust mixed with epoxy glue. This will significantly increase efficiency; the sawdust will serve as an additional magnetic circuit between the rotor iron. A sample can be made cutting machine or on a machine.

The mandrel for gluing magnets is done like this: the machined shaft is wrapped in polyintel, then a bandage soaked in epoxy glue is wound layer by layer, then ground to size on a machine and removed from the rotor, a template is glued and holes are drilled for the magnets. Then the mandrel is put back on the rotor and glued magnets are usually glued with epoxy glue. Below in the photo there are two examples of sticking magnets, the first example in 2 photos is sticking magnets using a mandrel, and the second on the next page directly through the template. In the first two photos you can clearly see and I think it’s clear how the magnets are glued.

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The idea of ​​having an autonomous source electrical energy and not depending on the fixed state network worries the minds of many rural residents.

It is quite simple to implement: you need a three-phase asynchronous electric motor, which can be used even from old, decommissioned industrial equipment.

A generator from an asynchronous motor is made with your own hands according to one of the three schemes published in this article. It will convert mechanical energy into electricity freely and reliably.

How to choose an electric motor

To eliminate errors at the project stage, it is necessary to pay attention to the design of the purchased motor, as well as its electrical characteristics: power consumption, supply voltage, rotor speed.

Asynchronous machines are reversible. They are able to operate in the following modes:

· electric motor when external voltage is applied to them;

· or a generator, if their rotor rotates a source of mechanical energy, for example, a water or wind wheel, an internal combustion engine.

We pay attention to the nameplate, the design of the rotor and stator. We take their features into account when creating a generator.

What you need to know about stator design

It has three insulated windings wound on a common magnetic core for power supply from each voltage phase.

They are connected in one of two ways:

1. A star, when all the ends are collected at one point. Voltage is supplied to the 3 beginnings and the common terminal of the ends via four wires.

2. Triangle - the end of one winding is connected to the beginning of the other so that the circuit is assembled into a ring and only three wires come out of it.

This information is presented in more detail in the article on my website aboutconnecting a three-phase motor to a single-phase household network .

Rotor design features

It also has a magnetic circuit and three windings. They are connected in one of two ways:

1. through the contact terminals of a motor with a wound rotor;

2. short-circuited with an aluminum insert into the squirrel wheel design - asynchronous machines.

We need a squirrel-cage rotor. All circuits are designed for him.

The wound rotor design can also be used as a generator. But it will have to be redone: we simply short-circuit all the outputs to each other.

How to take into account the electrical characteristics of the engine

The operation of the generator will be affected by:

1. Winding wire diameter. The heating of the structure and the amount of applied power directly depend on it.

2. The design speed of the rotor, indicated by the number of revolutions.

3. Method of connecting windings in a star or triangle.

4. The amount of energy loss determined by the efficiency and cosine φ.

We look at them on a plate or calculate them using indirect methods.

How to make an electric motor switch to generator mode

You need to do two things:

1. Spin the rotor from a source of extraneous mechanical power.

2. Excite an electromagnetic field in the windings.

If everything is clear with the first point, then for the second it is enough to connect a bank of capacitors to the windings, creating a capacitive load of a certain size.

Several variants of schemes have been developed for this issue.

Full star

Capacitors are included between each pair of windings.

Simplified star

In this circuit, the starting and running capacitors are connected by their own switches.

Triangle diagram

Capacitors are connected in parallel to each winding. A linear voltage of 220 volts is created at the output terminals.

What capacitor ratings are needed?

The easiest way is to use paper capacitors with voltages of 500 volts and above. It is better not to use electrolytic models: they can boil and explode.

The formula for determining capacity is:С=Q/2π∙f∙U2.

In it, Q is reactive power, f is frequency, U is voltage.