Constant and uninterrupted supply of electricity in the house is the key to a pleasant and comfortable pastime at any time of the year. In order to organize an autonomous power supply for a suburban area, we will have to resort to mobile installations - electric generators, which have been especially popular in recent years due to the large assortment of various capacities.
Scope of application
Many are interested in how to make an electric generator for a summer cottage? We will talk about this below. In most cases, an asynchronous alternator is applicable, which will produce energy for the operation of electrical appliances. In an asynchronous generator, the speed of rotation of the rotors than in a synchronous one and the efficiency will be higher.
However, power plants have found their application in a wider range, as an excellent means for extracting energy, namely:
- They are used in wind farms.
- Used as welding machines.
- They provide autonomous support for electricity in the house on a par with a miniature hydroelectric power station.
The unit is switched on using the input voltage. Often, the device is connected to power to start, but this is not a very logical and rational solution for a mini-station, which itself must generate electricity, and not consume it to start. Therefore, in recent years, generators with self-excitation or series switching of capacitors have been actively produced.
How an electric generator works
An asynchronous power generator produces a resource if the speed of rotation of the motor is faster than synchronous. The most common generator operates on parameters from 1500 rpm.
It produces power if the rotor at start is running faster than the synchronous speed. The difference between these figures is called slip and is calculated as a percentage of the synchronous speed. However, the stator speed is even higher than the rotor speed. Due to this, a stream of charged particles is formed that changes polarity.
Watch the video, how it works:
When energized, the connected power generator device takes control of the synchronous speed by independently controlling the slip. The energy leaving the stator passes through the rotor, however, the active power has already moved to the stator coils.
The basic principle of operation of an electric generator is to convert mechanical energy into electrical energy. To start the rotor to generate power, a strong torque is needed. The most adequate option, according to electricians, is "perpetual idling", which maintains one speed of rotation during the operation of the generator.
Why use an asynchronous generator
Unlike a synchronous generator, an asynchronous one has a huge number of advantages and benefits. The main factor in choosing the asynchronous option was the low clear factor. A high clear factor characterizes the quantitative presence of higher harmonics in the output voltage. They cause useless heating of the motor and uneven rotation. Synchronous generators have a clear factor value of 5-15%, in asynchronous generators it does not exceed 2%. It follows from this that an asynchronous power generator produces only useful energy.
A little about the asynchronous generator and its connection:
An equally significant advantage of this type of generator is the complete absence of rotating windings and electronic parts that are sensitive to damage and external factors. Therefore, this type of apparatus is not subject to active wear and tear and will last longer.
How to make a generator with your own hands
Device asynchronous alternator
The purchase of an asynchronous electric generator is a rather expensive pleasure for the average resident of our country. Therefore, many craftsmen resort to solving the issue of self-assembly of the apparatus. The principle of operation, as well as the design, is quite simple. With all the tools, assembly will not take more than 1-2 hours.
According to the above-described principle of operation of the electric generator, all equipment should be adjusted so that the rotations are faster than the engine revolutions. To do this, you must connect the engine to the network and start it. Use a tachometer or tachogenerator to calculate RPM.
After determining the value of the engine speed, add 10% to it. If the rotation speed is 1500 rpm, then the generator should be running at 1650 rpm.
Now you need to remake the asynchronous generator "for yourself", using capacitors of the required capacities. Use the following plate to determine the type and capacity:
We hope that it is already clear how to assemble an electric generator with your own hands, but please note: the capacitance of the capacitors should not be very high, otherwise the generator running on diesel fuel will get very hot.
Install the capacitors according to the calculation. Installation requires a fair amount of attention. Ensure good insulation, if necessary, use special coatings.
Based on the engine, the generator assembly process is completed. Now it can already be used as a necessary source of energy. Remember that in the case when the device has a squirrel-cage rotor and produces a rather serious voltage that exceeds 220 volts, it is necessary to install a step-down transformer that stabilizes the voltage at the required level. Remember that in order for all appliances in the house to work, there must be strict control of a home-made 220-volt electric generator in terms of voltage.
Watch the video, the stages of work:
For a generator that will run at low power, single-phase asynchronous motors from old or unwanted household appliances, such as washing machines, drain pumps, lawn mowers, chainsaws, etc., can be used to save money. Motors from such household appliances should be connected in parallel with the winding. Alternatively, phase-shifting capacitors can be used. They rarely differ in the required power, so it will need to be increased to the required performance.
Such generators show themselves very well when it is necessary to power light bulbs, modems and other small devices with a stable active voltage. With certain knowledge, you can connect an electric generator to an electric stove or heater.
The ready-to-use generator should be installed so that it is not affected by precipitation and the environment. Take care of an additional casing that will protect the installation from adverse conditions.
Almost every asynchronous generator, whether it is a brushless, electric, gasoline or diesel generator, is considered a device with a fairly high level of danger. Handle such equipment very carefully and always keep it protected from external weather and mechanical influences or make a casing for it.
Watch the video, practical advice from a specialist:
Any autonomous unit should be equipped with special measuring instruments that will record and display performance data. To do this, you can use a tachometer, voltmeter and frequency meter.
- Equip the generator with an on/off button if possible. You can use manual start to start.
- Some power generators need to be grounded before use, carefully assess the area and select a site for installation.
- When converting mechanical energy into electrical energy, sometimes the efficiency can drop to 30%.
- If you are not confident in your abilities or are afraid to do something wrong, we advise you to purchase a generator in the appropriate store. Sometimes the risks can turn out to be extremely deplorable ...
- Monitor the temperature of the asynchronous generator and its thermal regime.
Results
Despite their ease of implementation, homemade power generators are very painstaking work that requires complete focus on design and proper connection. The assembly is financially feasible only if you already have a workable and unnecessary engine. Otherwise, you will pay more than half of its cost for the main element of the installation, and the total costs may significantly exceed the market value of the generator.
As a generator for a windmill, it was decided to remake an asynchronous motor. Such alteration is very simple and affordable, therefore, in home-made designs of wind turbines, you can often see generators made from asynchronous motors.
The alteration consists in turning the rotor under the magnets, then the magnets are usually glued to the rotor according to the template and filled with epoxy so that they do not fly off. It is also common to rewind the stator with a thicker wire to reduce too much voltage and increase the current. But I did not want to rewind this engine and it was decided to leave everything as it is, only to convert the rotor to magnets. A three-phase asynchronous motor with a power of 1.32 kW was found as a donor. Below is a photo of this motor.
> The rotor of the electric motor was turned on a lathe to the thickness of the magnets. This rotor does not use a metal sleeve, which is usually machined and put on the rotor under the magnets. The sleeve is needed to enhance the magnetic induction, through it the magnets close their fields, feeding each other from under the bottom and the magnetic field does not dissipate, but everything goes into the stator. In this design, fairly strong magnets with a size of 7.6 * 6 mm in the amount of 160 pieces are used, which will provide good EMF even without a sleeve.
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> First, before sticking the magnets, the rotor was marked with four poles, and the magnets were placed with a bevel. The motor was four-pole, and since the stator was not rewound, the rotor must also have four magnetic poles. Each magnetic pole alternates, one pole is conditionally "north", the second pole is "south". The magnetic poles are spaced, so the magnets are grouped more densely at the poles. After placing the magnets on the rotor, they were wrapped with adhesive tape for fixation and filled with epoxy resin.
After assembly, sticking of the rotor was felt, sticking was felt when the shaft rotated. It was decided to remake the rotor. The magnets were knocked together with the epoxy and re-placed, but now they are more or less evenly spaced throughout the rotor, below is a photo of the rotor with magnets before epoxy pouring. After filling, the sticking decreased somewhat and it was noticed that the voltage dropped slightly when the generator rotated at the same speed and the current increased slightly.
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After assembling the finished generator, it was decided to twist it with a drill and connect something to it as a load. A light bulb was connected for 220 volts 60 watts, at 800-1000 rpm it burned in full heat. Also, to check what the generator was capable of, a lamp with a power of 1 Kw was connected, it burned at full heat and the drill could not turn the generator harder.
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At idle, at maximum drill speed of 2800 rpm, the generator voltage was more than 400 volts. At about 800 rpm, the voltage is 160 volts. We also tried to connect a 500-watt boiler, after a minute of torsion, the water in the glass became hot. These are the tests passed by the generator, which was made from an induction motor.
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After the generator was welded rack with a swivel axle for attaching the generator and tail. The design is made according to the scheme with the removal of the windhead from the wind by folding the tail, so the generator is offset from the center of the axis, and the pin behind is the kingpin on which the tail is put on.
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Here is a photo of the finished wind turbine. The wind turbine was mounted on a nine-meter mast. The generator with the force of the wind gave out an open circuit voltage of up to 80 volts. They tried to connect a two kilowatt tenn to it, after a while the tenn became warm, which means that the wind generator still has some kind of power.
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Then the controller for the wind generator was assembled and the battery was connected through it for charging. Charging was good enough current, the battery quickly made noise, as if it was being charged from a charger.
So far, unfortunately, there are no detailed data on the power of the wind generator, since the user who posted his wind generator here
If the rotor of an asynchronous machine connected to the network with voltage U1 is rotated by means of the primary motor in the direction of the rotating stator field, but at a speed n2>
Why We Use Asynchronous Power Generator
An asynchronous generator is an asynchronous electric machine (el.dvigatel) operating in the generator mode. With the help of a drive motor (in our case, a wind turbine), the rotor of an asynchronous electric generator rotates in the same direction as the magnetic field. In this case, the slip of the rotor becomes negative, a braking torque appears on the shaft of the asynchronous machine, and the generator transfers energy to the network.
To excite the electromotive force in its output circuit, the residual magnetization of the rotor is used. For this, capacitors are used.
Asynchronous generators are not susceptible to short circuits.
An asynchronous generator is simpler than a synchronous one (for example, a car generator): if the latter has inductors placed on the rotor, then the rotor of the asynchronous generator looks like a conventional flywheel. Such a generator is better protected from dirt and moisture, more resistant to short circuits and overloads, and the output voltage of an asynchronous generator has a lower degree of non-linear distortion. This allows you to use asynchronous generators not only to power industrial devices that are not critical to the shape of the input voltage, but also to connect electronic equipment.
It is an asynchronous electric generator that is an ideal current source for devices with an active (ohmic) load: electric heaters, welding converters, incandescent lamps, electronic devices, computer and radio equipment.
Benefits of an asynchronous generator
These advantages include a low clear factor (harmonic coefficient), which characterizes the quantitative presence of higher harmonics in the output voltage of the generator. Higher harmonics cause uneven rotation and useless heating of electric motors. Synchronous generators can have a clear factor of up to 15%, and the clear factor of an asynchronous generator does not exceed 2%. Thus, an asynchronous electric generator produces practically only useful energy.
Another advantage of an asynchronous generator is that it completely lacks rotating windings and electronic parts that are sensitive to external influences and are quite often prone to damage. Therefore, the asynchronous generator is not subject to wear and tear and can serve for a very long time.
At the output of our generators, there is immediately 220/380V AC, which can be used directly to household appliances (for example, heaters), to charge batteries, to connect to a sawmill, and also for parallel operation with a traditional network. In this case, you will pay for the difference consumed from the network and generated by the windmill. Because Since the voltage comes immediately to industrial parameters, then you will not need various converters (inverters) when the wind generator is directly connected to your load. For example, you can directly connect to a sawmill and, in the presence of wind, work as if you were simply connected to a 380V network.
If the rotor of an asynchronous machine connected to the network with voltage U1 is rotated by means of the primary motor in the direction of the rotating stator field, but at a speed n2>n1, then the movement of the rotor relative to the stator field will change (compared to the motor mode of this machine), since the rotor will overtake the stator field.
In this case, the slip will become negative, and the direction of the emf. E1 induced in the stator winding, and consequently, the direction of the current I1 will change to the opposite. As a result, the electromagnetic moment on the rotor will also change direction and turn from rotating (in the motor mode) into counteracting (in relation to the torque of the primary engine). Under these conditions, the asynchronous machine will switch from a motor to a generator mode, converting the mechanical energy of the prime mover into electrical energy. In the generator mode of an asynchronous machine, the slip can vary in the range
in this case, the emf frequency asynchronous generator remains unchanged, since it is determined by the rotation speed of the stator field, i.e. remains the same as the frequency of the current in the network, which is connected to the asynchronous generator.
Due to the fact that in the generator mode of the asynchronous machine the conditions for creating a rotating stator field are the same as in the motor mode (in both modes, the stator winding is connected to the network with voltage U1), and it consumes the magnetizing current I0 from the network, then the asynchronous a machine in generator mode has special properties: it consumes reactive energy from the network, which is necessary to create a rotating stator field, but gives active energy to the network, obtained as a result of converting the mechanical energy of the prime mover.
Unlike synchronous, asynchronous generators are not subject to the dangers of falling out of synchronism. However, asynchronous generators are not widely used, which is explained by a number of their disadvantages compared to synchronous generators.
An asynchronous generator can also operate in autonomous conditions, i.e. without being connected to the public network. But in this case, to obtain the reactive power necessary to magnetize the generator, a bank of capacitors is used, connected in parallel with the load on the generator outputs.
An indispensable condition for such operation of asynchronous generators is the presence of residual magnetization of the rotor steel, which is necessary for the process of self-excitation of the generator. Small emf Eres induced in the stator winding creates a small reactive current in the capacitor circuit and, consequently, in the stator winding, which enhances the residual flux Fost. In the future, the self-excitation process develops, as in a parallel excitation DC generator. By changing the capacitance of the capacitors, it is possible to change the magnitude of the magnetizing current, and, consequently, the magnitude of the voltage of the generators. Due to the excessive bulkiness and high cost of capacitor banks, asynchronous generators with self-excitation have not gained distribution. Asynchronous generators are used only in low-power auxiliary power plants, for example, in wind power plants.
DIY generator
In my power plant, the current source is an asynchronous generator driven by a gasoline two-cylinder air-cooled engine UD-25 (8 hp, 3000 rpm). As an asynchronous generator, without any alterations, you can use a conventional asynchronous electric motor with a speed of 750-1500 rpm and a power of up to 15 kW.
The frequency of rotation of the asynchronous generator in normal mode must exceed the nominal (synchronous) value of the number of revolutions of the used electric motor by 10%. This can be done in the following way. The electric motor is connected to the network and the idle speed is measured by a tachometer. The belt drive from the engine to the generator is calculated in such a way as to provide a slightly increased generator speed. For example, an electric motor with a rated speed of 900 rpm idles at 1230 rpm. In this case, the belt drive is calculated to provide a generator speed of 1353 rpm.
The windings of the asynchronous generator in my installation are connected with a “star” and produce a three-phase voltage of 380 V. To maintain the nominal voltage of the asynchronous generator, it is necessary to correctly select the capacitance of the capacitors between each phase (all three capacitances are the same). To select the desired capacity, I used the following table. Before acquiring the necessary skill in operation, you can check the heating of the generator by touch in order to avoid overheating. Heating indicates that too much capacitance is connected.
Capacitors are suitable type KBG-MN or others with an operating voltage of at least 400 V. When the generator is turned off, an electric charge remains on the capacitors, therefore, precautions must be taken against electric shock. Capacitors should be securely enclosed.
When working with a 220 V handheld power tool, I use a TSZI step-down transformer from 380 V to 220 V. When a three-phase engine is connected to a power plant, it may happen that the generator does not “master” it from the first start. Then you should give a series of short-term engine starts until it picks up speed, or spin it manually.
Stationary asynchronous generators of this kind, used for electrical heating of a residential building, can be driven by a wind turbine or a turbine installed on a small river or stream, if there are any near the house. At one time in Chuvashia, the Energozapchast plant produced a generator (micro hydroelectric power station) with a capacity of 1.5 kW based on an asynchronous electric motor. V.P. Beltyukov from Nolinsk made a wind turbine and also used an asynchronous motor as a generator. Such a generator can be set in motion using a walk-behind tractor, a minitractor, a scooter engine, a car, etc.
I installed my power plant on a small, light, single-axle trailer - a frame. For work outside the economy, I load the necessary power tools into the machine and attach my installation to it. With a rotary mower I mow hay, with an electric tractor I plow the land, harrow, plant, and spud. For such work, complete with the station, I drive a coil with a four-wire cable KRPT. When winding the cable, one thing should be taken into account. If wound in the usual way, then a solenoid is formed, in which there will be additional losses. To avoid them, the cable must be folded in half and wound on a coil, starting from the bend.
In late autumn, firewood has to be harvested from deadwood for the winter. I also use power tools. At the summer cottage, with the help of a circular saw and a planer, I process material for carpentry.
As a result of a long test of the operation of our Sailing wind generator with a traditional excitation circuit of an asynchronous motor (IM), based on the use of a magnetic starter as a switch, a number of shortcomings were revealed, which led to the creation of the Control Cabinet. Which has become a universal device for turning any Asynchronous Motor into a Generator! Now it is enough to connect the wires from the IM of the engine to our control device and the generator is ready.
How to Turn Any Induction Motor into a Generator - A House Without a Foundation
How to Turn Any Induction Motor Into a Generator - A House Without a Foundation Why We Use an Induction Power Generator An induction generator is a generator
For the needs of building a private residential building or a summer house, a home master may need an autonomous source of electrical energy, which can be bought in a store or assembled with your own hands from available parts.
Homemade generator is able to run on the energy of gasoline, gas or diesel fuel. To do this, it must be connected to the engine through a shock-absorbing clutch that ensures smooth rotation of the rotor.
If local environmental conditions allow, for example, frequent winds blow or a source of running water is nearby, then you can create a wind or hydraulic turbine and connect it to an asynchronous three-phase motor to generate electricity.
Due to such a device, you will have a constantly working alternative source of electricity. It will reduce energy consumption from public networks and allow savings on its payment.
In some cases, it is permissible to use a single-phase voltage to rotate an electric motor and transmit torque to a home-made generator to create its own three-phase symmetrical network.
How to choose an asynchronous motor for a generator by design and characteristics
Technological features
The basis of a homemade generator is a three-phase asynchronous electric motor with:
Stator device
The magnetic circuits of the stator and rotor are made of insulated plates of electrical steel, in which grooves are created to accommodate the winding wires.
The three individual stator windings can be wired in the factory as follows:
Their conclusions are connected inside the terminal box and connected by jumpers. The power cable is also installed here.
In some cases, wires and cables can be connected in other ways.
Symmetrical voltages are supplied to each phase of the induction motor, shifted in angle by a third of the circle. They form currents in the windings.
These quantities are conveniently expressed in vector form.
Design features of the rotors
Wound rotor motors
They are provided with a winding modeled on the stator, and the leads from each are connected to slip rings, which provide electrical contact with the start-up and adjustment circuit through pressure brushes.
This design is quite difficult to manufacture, expensive in cost. It requires periodic monitoring of work and qualified maintenance. For these reasons, it makes no sense to use it in this design for a home-made generator.
However, if there is a similar motor and it has no other application, then the conclusions of each winding (those ends that are connected to the rings) can be shorted to each other. In this way, the phase rotor will turn into a short-circuited one. It can be connected according to any scheme considered below.
Squirrel cage motors
Aluminum is poured inside the grooves of the rotor magnetic circuit. The winding is made in the form of a rotating squirrel cage (for which it received such an additional name) with jumper rings short-circuited at the ends.
This is the simplest motor circuit, which is devoid of moving contacts. Due to this, it works for a long time without the intervention of electricians, it is characterized by increased reliability. It is recommended to use it to create a homemade generator.
Designations on the motor housing
In order for a homemade generator to work reliably, you need to pay attention to:
- IP class, which characterizes the quality of protection of the housing from environmental influences;
- power consumption;
- speed;
- winding connection diagram;
- permissible load currents;
- Efficiency and cosine φ.
The winding connection diagram, especially for old engines that were in operation, should be called out and checked by electrical methods. This technology is described in detail in the article on connecting a three-phase motor to a single-phase network.
The principle of operation of an induction motor as a generator
Its implementation is based on the method of electric machine reversibility. If the motor is disconnected from the mains voltage, the rotor is forced to rotate at the calculated speed, then EMF will be induced in the stator winding due to the presence of residual energy of the magnetic field.
It remains only to connect a capacitor bank of the appropriate rating to the windings and a capacitive leading current will flow through them, which has the character of a magnetizing one.
In order for the generator to self-excite, and a symmetrical system of three-phase voltages to form on the windings, it is necessary to select the capacitance of the capacitors, which is greater than a certain, critical value. In addition to its value, the design of the engine naturally affects the output power.
For the normal generation of three-phase energy with a frequency of 50 Hz, it is necessary to maintain the rotor speed exceeding the asynchronous component by the amount of slip S, which lies within S=2÷10%. It needs to be kept at the synchronous frequency level.
The deviation of the sinusoid from the standard frequency value will adversely affect the operation of equipment with electric motors: saws, planers, various machine tools and transformers. This has practically no effect on resistive loads with heating elements and incandescent lamps.
Wiring diagrams
In practice, all common methods of connecting the stator windings of an induction motor are used. Choosing one of them creates different conditions for the operation of the equipment and generates a voltage of certain values.
Star schemes
A popular option for connecting capacitors
The connection diagram of an asynchronous motor with star-connected windings for operation as a three-phase network generator has a standard form.
Scheme of an asynchronous generator with connection of capacitors to two windings
This option is quite popular. It allows you to power three groups of consumers from two windings:
The working and starting capacitors are connected to the circuit by separate switches.
Based on the same circuit, you can create a home-made generator with capacitors connected to one winding of an induction motor.
triangle diagram
When assembling the stator windings according to the star circuit, the generator will produce a three-phase voltage of 380 volts. If you switch them to a triangle, then - 220.
The three schemes shown above in the pictures are basic, but not the only ones. Based on them, other connection methods can be created.
How to calculate the characteristics of the generator by engine power and capacitor capacitance
To create normal operating conditions for an electric machine, it is necessary to observe the equality of its rated voltage and power in the generator and electric motor modes.
For this purpose, the capacitance of the capacitors is selected taking into account the reactive power Q generated by them at various loads. Its value is calculated by the expression:
From this formula, knowing the power of the engine, to ensure full load, you can calculate the capacity of the capacitor bank:
However, the mode of operation of the generator should be taken into account. At idle, the capacitors will unnecessarily load the windings and heat them up. This leads to large energy losses, overheating of the structure.
To eliminate this phenomenon, capacitors are connected in steps, determining their number depending on the applied load. To simplify the selection of capacitors for starting an asynchronous motor in generator mode, a special table has been created.
Starting capacitors of the K78-17 series and the like with an operating voltage of 400 volts or more are well suited for use as part of a capacitive battery. It is quite acceptable to replace them with metal-paper counterparts with the corresponding denominations. They will have to be connected in parallel.
It is not worth using models of electrolytic capacitors to work in the circuits of an asynchronous home-made generator. They are designed for DC circuits, and when passing a sinusoid that changes in direction, they quickly fail.
There is a special scheme for connecting them for such purposes, when each half-wave is directed by diodes to its assembly. But it's pretty complicated.
Design
The autonomous device of the power plant must fully meet the requirements for the safe operation of operating equipment and be carried out by a single module, including a mounted electrical panel with devices:
- measurements - with a voltmeter up to 500 volts and a frequency meter;
- switching loads - three switches (one general supplies voltage from the generator to the consumer circuit, and the other two connect capacitors);
- protection - an automatic switch that eliminates the consequences of short circuits or overloads and an RCD (residual current device) that saves workers from insulation breakdown and phase potential entering the case.
Main power redundancy
When creating a home-made generator, it is necessary to provide for its compatibility with the grounding circuit of the working equipment, and for autonomous operation, it must be reliably connected to the ground loop.
If the power plant is created for backup power supply of devices operating from the state network, then it should be used when the voltage is disconnected from the line, and when restored, it should be stopped. To this end, it is enough to install a switch that controls all phases simultaneously or connect a complex automatic system for switching on backup power.
Voltage selection
The 380 volt circuit has an increased risk of human injury. It is used in extreme cases, when it is not possible to get by with a phase value of 220.
Generator overload
Such modes create excessive heating of the windings with subsequent destruction of the insulation. They occur when the currents passing through the windings are exceeded due to:
- improper selection of capacitor capacitance;
- connection of high power consumers.
In the first case, it is necessary to carefully monitor the thermal regime during idling. With excessive heating, it is necessary to adjust the capacitance of the capacitors.
Features of connecting consumers
The total power of a three-phase generator consists of three parts generated in each phase, which is 1/3 of the total. The current passing through one winding must not exceed the rated value. This must be taken into account when connecting consumers, distribute them evenly over the phases.
When a homemade generator is designed to operate on two phases, then it cannot safely generate electricity more than 2/3 of the total value, and if only one phase is involved, then only 1/3.
Frequency control
The frequency meter allows you to monitor this indicator. When it was not installed in the design of a home-made generator, then you can use the indirect method: at idle, the output voltage exceeds the nominal 380/220 by 4 ÷ 6% at a frequency of 50 Hz.
How to make a homemade generator from an asynchronous motor, Design and repair of apartments with your own hands
Tips for a home craftsman on making a do-it-yourself home-made generator from an asynchronous three-phase electric motor with diagrams. pictures and videos
How to make a homemade generator from an induction motor
Hello! Today we will consider how to make a homemade generator from an asynchronous motor with your own hands. This question has been of interest to me for a long time, but somehow there was no time to take up its implementation. Now let's do some theory.
If you take and spin an asynchronous electric motor from some prime mover, then following the principle of reversibility of electrical machines, you can make it produce electric current. To do this, you need to rotate the shaft of an asynchronous motor with a frequency equal to or slightly more than the asynchronous frequency of its rotation. As a result of residual magnetism in the magnetic circuit of the electric motor, some EMF will be induced at the terminals of the stator winding.
Now let's take and connect to the terminals of the stator winding, as shown in the figure below, non-polar capacitors C.
In this case, a leading capacitive current will begin to flow through the stator winding. It will be called magnetizing. Those. self-excitation of the asynchronous generator will occur and the EMF will increase. The value of the EMF will depend on the characteristics of both the electrical machine itself and the capacitance of the capacitors. Thus, we have turned an ordinary asynchronous electric motor into a generator.
Now let's talk about how to choose the right capacitors for a homemade generator from an induction motor. The capacity must be selected so that the generated voltage and output power of the asynchronous generator correspond to the power and voltage when it is used as an electric motor. See the data in the table below. They are relevant for excitation of asynchronous generators with a voltage of 380 volts and with a speed of rotation from 750 to 1500 rpm.
With an increase in the load on the asynchronous generator, the voltage at its terminals will tend to fall (the inductive load on the generator will increase). To maintain the voltage at a given level, it is necessary to connect additional capacitors. To do this, you can use a special voltage regulator, which, when the voltage drops at the generator stator terminals, will connect additional capacitor banks with the help of contacts.
The frequency of rotation of the generator in normal mode should exceed the synchronous one by 5-10 percent. That is, if the rotational speed is 1000 rpm, then you need to spin it at a frequency of 1050-1100 rpm.
One big plus of an asynchronous generator is that you can use a conventional asynchronous electric motor as it without alterations. But it is not recommended to get carried away and make generators from electric motors with a power of more than 15-20 kV * A. A homemade generator from an asynchronous motor is an excellent solution for those who do not have the opportunity to use a classic kronotex laminate generator. Good luck with everything and bye!
How to make a homemade generator from an asynchronous motor, DIY repair
How to make a homemade generator from an asynchronous motor Hello everyone! Today we will consider how to make a homemade generator from an asynchronous motor with your own hands. This question has long
Often there is a need to provide an autonomous power supply in a country house. In such a situation, a do-it-yourself generator from an asynchronous motor will help out. It is easy to make it yourself, having certain skills in handling electrical engineering.
Principle of operation
Due to their simple structure and efficient operation, asynchronous motors are widely used in industry. They make up a significant proportion of all engines. The principle of their operation is to create a magnetic field by the action of an alternating electric current.
Experiments have shown that by rotating a metal frame in a magnetic field, it is possible to induce an electric current in it, the appearance of which is confirmed by the glow of a light bulb. This phenomenon is called electromagnetic induction.
Engine device
An asynchronous motor consists of a metal case, inside of which are:
- winding stator, through which an alternating electric current is passed;
- winding rotor, through which current flows in the opposite direction.
Both elements are on the same axis. The steel plates of the stator fit snugly together, in some modifications they are firmly welded. The copper winding of the stator is insulated from the core with cardboard spacers. In the rotor, the winding is made of aluminum rods closed on both sides. The magnetic fields generated by the passage of an alternating current act on each other. An EMF occurs between the windings, which rotates the rotor, since the stator is stationary.
The generator from an asynchronous motor consists of the same components, however, in this case, the reverse action occurs, that is, the transition of mechanical or thermal energy into electrical energy. When operating in the motor mode, it retains residual magnetization, which induces an electric field in the stator.
The speed of rotation of the rotor must be higher than the change in the magnetic field of the stator. It can be slowed down by the reactive power of the capacitors. The charge accumulated by them is opposite in phase and gives a "braking effect". Rotation can be provided with the energy of wind, water, steam.
Generator circuit
The generator from an asynchronous motor has a simple circuit. After reaching the synchronous speed of rotation, the process of formation of electrical energy in the stator winding takes place.
If a capacitor bank is connected to the winding, a leading electric current occurs, which forms a magnetic field. In this case, the capacitors must have a capacitance higher than the critical one, which is determined by the technical parameters of the mechanism. The strength of the generated current will depend on the capacity of the capacitor bank and the characteristics of the motor.
Manufacturing technology
The work of converting an asynchronous electric motor into a generator is quite simple if you have the necessary parts.
To start the process of alteration, the following mechanisms and materials are required:
- induction motor- a single-phase motor from an old washing machine is suitable;
- instrument for measuring rotor speed- tachometer or tachogenerator;
- non-polar capacitors- models of the type KBG-MN with an operating voltage of 400 V are suitable;
- a set of hand tools- drills, hacksaws, keys.
Step-by-step instruction
Making a generator with your own hands from an asynchronous motor is carried out according to the presented algorithm.
- The generator must be adjusted so that its speed is greater than the engine speed. The value of the rotation speed is measured by a tachometer or other device when the engine is turned on in the mains.
- The resulting value should be increased by 10% of the existing indicator.
- The capacity for the capacitor bank is selected - it should not be too large, otherwise the equipment will get very hot. To calculate it, you can use the table of the relationship between the capacitance of the capacitor and reactive power.
- A capacitor bank is installed on the equipment, which will provide the design rotation speed for the generator. Its installation requires special attention - all capacitors must be securely isolated.
For 3-phase motors, capacitors are connected in a star or delta connection. The first type of connection makes it possible to generate electricity at a lower rotor speed, but the output voltage will be lower. To reduce it to 220 V, a step-down transformer is used.
Making a magnetic generator
The magnetic generator does not require the use of a capacitor bank. This design uses neodymium magnets. To get the job done:
- arrange the magnets on the rotor according to the scheme, observing the poles - each of them must have at least 8 elements;
- the rotor must first be machined on a lathe to the thickness of the magnets;
- fix the magnets firmly with glue;
- fill the rest of the free space between the magnetic elements with epoxy;
- after installing the magnets, you need to check the diameter of the rotor - it should not increase.
Advantages of a homemade electric generator
A do-it-yourself generator made from an asynchronous motor will become an economical current source that will reduce the consumption of centralized electricity. With it, you can provide power to household electrical appliances, computer equipment, heaters. A homemade generator from an asynchronous motor has undoubted advantages:
- simple and reliable design;
- effective protection of internal parts from dust or moisture;
- overload resistance;
- long service life;
- the ability to connect devices without inverters.
When working with a generator, you should also take into account the possibility of random changes in electric current.
A power source is needed to power household appliances and industrial equipment. There are several ways to generate electricity. But the most promising and cost-effective, today, is the generation of current by electric machines. The easiest to manufacture, cheap and reliable in operation turned out to be an asynchronous generator that generates the lion's share of the electricity we consume.
The use of electric machines of this type is dictated by their advantages. Asynchronous power generators, unlike, provide:
- a higher degree of reliability;
- long service life;
- profitability;
- minimum maintenance costs.
These and other properties of asynchronous generators are inherent in their design.
Device and principle of operation
The main working parts of an asynchronous generator are the rotor (moving part) and the stator (stationary). In Figure 1, the rotor is on the right and the stator is on the left. Pay attention to the rotor device. It does not show windings of copper wire. In fact, windings exist, but they consist of aluminum rods short-circuited into rings located on both sides. In the photo, the rods are visible in the form of oblique lines.
The design of short-circuited windings forms the so-called "squirrel cage". The space inside this cage is filled with steel plates. To be precise, aluminum rods are pressed into grooves made in the rotor core.
Rice. 1. Rotor and stator of an asynchronous generator
The asynchronous machine, the device of which is described above, is called a squirrel-cage generator. Anyone who is familiar with the design of an asynchronous electric motor must have noticed the similarity in the structure of these two machines. In fact, they are no different, since the induction generator and the squirrel-cage motor are almost identical, with the exception of additional excitation capacitors used in generator mode.
The rotor is located on a shaft, which sits on bearings clamped on both sides by covers. The whole structure is protected by a metal case. Generators of medium and high power require cooling, so a fan is additionally installed on the shaft, and the case itself is made ribbed (see Fig. 2).
Rice. 2. Asynchronous generator assembly Operating principle
By definition, a generator is a device that converts mechanical energy into electrical current. It does not matter what energy is used to rotate the rotor: wind, potential energy of water or internal energy converted by a turbine or internal combustion engine into mechanical energy.
As a result of the rotation of the rotor, the magnetic lines of force formed by the residual magnetization of the steel plates cross the stator windings. EMF is formed in the coils, which, when active loads are connected, leads to the formation of current in their circuits.
At the same time, it is important that the synchronous speed of rotation of the shaft slightly (by about 2 - 10%) exceeds the synchronous frequency of the alternating current (set by the number of stator poles). In other words, it is necessary to ensure the asynchrony (mismatch) of the rotational speed by the amount of rotor slip.
It should be noted that the current thus obtained will be small. To increase the output power, it is necessary to increase the magnetic induction. They achieve an increase in the efficiency of the device by connecting capacitors to the terminals of the stator coils.
Figure 3 shows a diagram of a welding asynchronous alternator with capacitor excitation (left side of the diagram). Please note that the excitation capacitors are connected in delta. The right side of the figure is the actual diagram of the inverter welding machine itself.
Rice. 3. Scheme of welding asynchronous generator There are other, more complex excitation schemes, for example, using inductors and a capacitor bank. An example of such a circuit is shown in Figure 4.
Figure 4. Diagram of a device with inductors Difference from synchronous generator
The main difference between a synchronous alternator and an asynchronous generator is in the design of the rotor. In a synchronous machine, the rotor consists of wire windings. To create magnetic induction, an autonomous power source is used (often an additional low-power DC generator located on the same axis as the rotor).
The advantage of a synchronous generator is that it generates a higher quality current and is easily synchronized with other alternators of this type. However, synchronous alternators are more sensitive to overloads and short circuits. They are more expensive than their asynchronous counterparts and more demanding to maintain - you need to monitor the condition of the brushes.
The harmonic distortion or clear factor of induction generators is lower than that of synchronous alternators. That is, they generate almost clean electricity. On such currents they work more stable:
- adjustable chargers;
- modern television receivers.
Asynchronous generators provide reliable start of electric motors that require high starting currents. According to this indicator, they are, in fact, not inferior to synchronous machines. They have less reactive loads, which has a positive effect on the thermal regime, since less energy is spent on reactive power. The asynchronous alternator has better output frequency stability at different rotor speeds.
Classification
Squirrel-cage generators are most widely used due to the simplicity of their design. However, there are other types of asynchronous machines: alternators with a phase rotor and devices using permanent magnets that form an excitation circuit.
In Figure 5, for comparison, two types of generators are shown: on the left, on the base, and on the right, an asynchronous machine based on IM with a phase rotor. Even a cursory glance at the schematic images shows the complicated design of the phase rotor. Attention is drawn to the presence of slip rings (4) and the brush holder mechanism (5). The number 3 indicates the grooves for the wire winding, to which it is necessary to apply current to excite it.
Rice. 5. Types of asynchronous generators The presence of excitation windings in the rotor of an asynchronous generator improves the quality of the generated electric current, but at the same time such advantages as simplicity and reliability are lost. Therefore, such devices are used as an autonomous power source only in those areas where it is difficult to do without them. Permanent magnets in rotors are used mainly for the production of low-power generators.
Application area
The most common use of generator sets with a squirrel-cage rotor. They are inexpensive and require virtually no maintenance. Devices equipped with starting capacitors have decent efficiency indicators.
Asynchronous alternators are often used as an independent or backup power source. They work with them, they are used for powerful mobile and.
Alternators with a three-phase winding confidently start a three-phase electric motor, therefore they are often used in industrial power plants. They can also power equipment in single-phase networks. The two-phase mode allows you to save ICE fuel, since the unused windings are in idle mode.
The scope of application is quite extensive:
- transport industry;
- Agriculture;
- domestic sphere;
- medical institutions;
Asynchronous alternators are convenient for the construction of local wind and hydraulic power plants.
DIY asynchronous generator
Let's make a reservation right away: we are not talking about making a generator from scratch, but about converting an asynchronous motor into an alternator. Some craftsmen use a ready-made stator from a motor and experiment with a rotor. The idea is to use neodymium magnets to make the rotor poles. A blank with glued magnets may look something like this (see Fig. 6):
Rice. 6. Blank with glued magnets You stick magnets on a specially machined workpiece, planted on the motor shaft, observing their polarity and shift angle. This will require at least 128 magnets.
The finished structure must be adjusted to the stator and at the same time ensure a minimum gap between the teeth and the magnetic poles of the manufactured rotor. Since the magnets are flat, they will have to be ground or turned, while constantly cooling the structure, since neodymium loses its magnetic properties at high temperatures. If you do everything right, the generator will work.
The problem is that in artisanal conditions it is very difficult to make an ideal rotor. But if you have a lathe and are willing to spend a few weeks tweaking and tweaking, you can experiment.
I propose a more practical option - turning an induction motor into a generator (see the video below). To do this, you need an electric motor with suitable power and an acceptable rotor speed. Engine power must be at least 50% higher than the required alternator power. If such an electric motor is at your disposal, proceed to processing. Otherwise, it is better to buy a ready-made generator.
For processing, you will need 3 capacitors of the brand KBG-MN, MBGO, MBGT (you can take other brands, but not electrolytic). Select capacitors for a voltage of at least 600 V (for a three-phase motor). The reactive power of the generator Q is related to the capacitance of the capacitor by the following relationship: Q = 0.314·U 2 ·C·10 -6 .
With an increase in load, reactive power increases, which means that in order to maintain a stable voltage U, it is necessary to increase the capacitance of the capacitors by adding new capacitances by switching.
Video: making an asynchronous generator from a single-phase motor - Part 1
Part 2
In practice, the average value is usually chosen, assuming that the load will not be maximum.
Having selected the parameters of the capacitors, connect them to the terminals of the stator windings as shown in the diagram (Fig. 7). The generator is ready.
Rice. 7. Capacitor connection diagram Asynchronous generator does not require special care. Its maintenance consists in monitoring the condition of the bearings. At nominal modes, the device is able to work for years without operator intervention.
The weak link is the capacitors. They can fail, especially when their ratings are incorrectly selected.
The generator heats up during operation. If you often connect high loads, monitor the temperature of the device or take care of additional cooling.