Do-it-yourself electric generator: assembly procedure. How to make a generator from an induction motor How to make a generator from an AC motor

Not all existing electrical networks (especially those operating in regions remote from cities) can provide the consumer with a full-fledged power supply suitable for the operation of modern household equipment. Due to the low quality of the voltage coming from substations and its frequent outages, many users are forced to think about how to make a home-made electricity generator. How such an asynchronous generator looks externally can be found in Fig. below.

The indicated approach to solving the problem of power supply outside the city allows significant savings in comparison with the situation when generating equipment is purchased through the distribution network in finished form.

Reversibility effect

It is known that the principle of operation of any device generating electric current is based on the conversion of one form of energy (heat, for example) into the form necessary for powering the equipment. You can use the so-called alternative (they are also called renewable) sources of energy supply, however, this method is associated with even greater material and production costs.

It is much easier and more economical to make a home-made current generator, taking advantage of the potential capabilities of the old asynchronous electric motor available to the user.

The basis for such manufacture is the well-known principle in electrical engineering of the reversibility of the processes of interaction of electromagnetic fields, which is explained by the specifics of the electrical processes occurring in this case. If in the engine three-phase current energy is used to turn it into mechanical rotation of the shaft, then in the generator everything happens exactly the opposite. In these units, the forced rotation of the armature is transformed into an electric current flowing through the phase windings, the power of which is spent on servicing the consumer (see the figure below).

Thus, before you make a sample of a home-made electric generator from a used induction motor, in the most general case, you need to do the following manipulations:

• The terminals to which a three-phase (or single-phase - for collector product samples) voltage is supplied must be turned into output contacts of the generator;
• To the moving part of the generator, from which one or another mechanism worked (machine, for example), a drive from an external source of a mechanical rotational impulse should be adapted;

Additional Information. As such a source, any propeller suitable for specific conditions can be used, rotating under the influence of the energy of a burning fuel (gasoline, gas or diesel fuel). If there is a windmill or a home-made water mill in a private household, the solution to the problem with the drive is greatly simplified.

• Due to the high cost of gasoline in a country economy, the only acceptable option is to manufacture a small power plant powered by a diesel engine or gas.

In this case, the engine running on relatively cheap fuel is connected through a special drive coupling to the shaft of the structure under construction, which, after a little modification, turns into an alternating current generator.

Design choice

It is possible to make a generator from an asynchronous motor quite successfully if you carefully study the design and structure of each of these mechanisms. Let us first consider a typical asynchronous motor operating on the principle of rotor slip in a stator electromagnetic field lagging in phase. The fixed part of this unit (the stator) is equipped, as you know, with three coils displaced relative to each other in space by 120 geometric degrees.

Due to the interaction of the moving and stationary fields, an alternating voltage is induced in the stator coils, represented by a sequence of three working phases (A, B and C).

A simpler version of the manufacture of a synchronous machine (generator) involves the use of a second-hand commutator single-phase motor, which incorporates a phase shift device on a fixed capacitor.

The manufacture of a single-phase system greatly simplifies the design of the future generator, but the power of such a product is relatively small. This circumstance does not allow using it to power some samples of single-phase power units (a borehole pump, for example).

Note! A single-phase device assembled on the basis of a collector engine can only be enough in terms of power to supply the home lighting network.

In cases where it becomes necessary to connect more powerful power equipment to the supply line, the only right decision is to make a generator from an asynchronous mechanism (figure below).

Let's consider how this mechanism can be converted into a three-phase generator in more detail.

The procedure for finalizing the windings

Before making a generator from an asynchronous motor, you should deal with its stator coils, interconnected and included in the supply line according to a certain scheme.

Additional Information. For the classic connection of asynchronous mechanisms, two types of stator windings are used: according to the so-called "star" or "triangle" scheme.

In the first case, all three linear coils (A, B and C) on the one hand are combined into a common neutral wire, while their second ends are connected to three phase lines. When turned on by a “triangle”, the end of one coil is connected to the beginning of the second, and its end, in turn, to the beginning of the third winding, and so on until the chain closes.

As a result of such a connection, a regular geometric figure is formed, the vertices of which correspond to three phase wires, and there is no neutral wire at all.

For reasons of ease of installation and safety of operation in household circuits, a star connection is usually selected, which makes it possible to organize local (repeated) protective grounding.

When modifying the engine, remove the cover of the junction box and gain access to the terminals, which, under normal conditions, receive a three-phase supply voltage. In generator mode, these contacts should be connected to the supply line with three-phase household consumers connected to it.

To organize a single-phase power supply (outlet lines and lighting circuits, in particular), they will need to be connected at one end to the selected phase contact A, B or C, and at the other - to a common neutral wire. The order of connecting wires to an asynchronous motor is shown in the following figure.

Important! In the case of several linear (single-phase) loads, it is necessary to distribute them among the phases in such a way that they are loaded more or less evenly.

Thus, a do-it-yourself generator assembled from a three-phase motor will be loaded on all supply circuits, and end consumers will receive the standard power they are entitled to.

Organization of the drive part

In domestic conditions, as a rule, standard gas generators are used as a mechanical drive, from which the torque is transmitted directly to the working shaft. The main problem with such a connection is the organization of a reliable coupling clutch that fully transmits torque to the generator armature axis (in this situation, its function is performed by the engine rotor).

When arranging it, the best option is to seek help from professional mechanics who will help organize a coupling connection of the required quality and reliability.

Note! The rotor of the reworked mechanism resembles in its design the stator winding with three windings shifted by 120 degrees (in this case it is called phase winding).

Linear outputs of each of the windings are connected to removable contact rings, through which the starting voltage was applied to the motor mechanism through graphite brushes. If you leave everything as it was, you get a design that is very difficult to manufacture and maintain, and it does not make sense to use it as part of a future generator.

For the convenience of rework, it is best to use the circuit of a short-circuited moving part, which can be obtained by shorting the working leads of each of the phase rotor coils.

Permanent magnet generator

Another way of arranging household generators is known, which consists in using powerful permanent magnets and a number of additional devices in the manufacture (in some media they are also called "eternal").

The principle of operation of such an energy source on magnets is the interaction of electromagnetic fields created by permanent magnetic blanks rigidly fixed on the stator and rotor parts of the device (see figure below).

The main advantage of such engines, which perform the function of a generator, is that there is no need for an external energy source or fuel. However, in this case, it is not without drawbacks, which are manifested, first of all, in the fact that strong magnetic fields can adversely affect the health of the attendants.

Given this shortcoming, in all other situations, such an electric motor is widely used in various drive units, often installed on industrial equipment. As an example, a generator known among specialists, under the designation "g 303", can be given.

In conclusion of the review of home-made generators, it should be noted that in order to convert them from asynchronous motors, a whole set of special removable tools may be required, reminiscent of automotive equipment in their composition.

Video

The idea of ​​having an autonomous source of electrical energy and not being dependent on a stationary state network excites the minds of many rural residents.

Implementing it is quite simple: you need a three-phase asynchronous electric motor that can be used even from old, decommissioned industrial equipment.

A do-it-yourself generator from an asynchronous motor is made according to one of the three schemes published in this article. It will convert mechanical energy into electricity for free and reliably.

How to choose an electric motor

To eliminate errors at the design 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 work in the mode:

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 into account their features when creating a generator.

What you need to know about the design of the stator

It has three isolated windings wound on a common core of the magnetic circuit for power supply from each phase of the voltage.

They are connected in one of two ways:

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

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

This information is described in more detail in the article of my site about connecting a three-phase motor to a household single-phase 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 phase rotor;

2. short-circuited with an aluminum insert in the squirrel wheel structure - asynchronous machines.

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

The design of the phase rotor can also be used as a generator. But it will have to be redone: we simply shunt all the outputs between ourselves with short circuits.

How to take into account the electrical characteristics of the motor

The operation of the generator will be affected by:

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

2. Calculated rotor speed, indicated by the number of revolutions.

3. The method of connecting the windings into a star or delta.

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

We look at the plate or calculate them by indirect methods.

How to make an electric motor go into 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 capacitor bank to the windings, creating a capacitive load of a certain value.

Several schemes have been developed for this issue.

full star

Capacitors are connected between each pair of windings.

Simplified star

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

triangle diagram

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

What are the capacitor ratings

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

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

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

The desire to develop an autonomous source for the production of electricity made it possible to build a generator from a conventional asynchronous motor. The development is reliable and relatively simple.

Types and description of an induction motor

There are two types of motors:

1. squirrel-cage rotor. It includes a stator (fixed element) and a rotor (rotating element) driven by bearings attached to two motor shields. The cores are made of steel, and they are also insulated from each other. An insulated wire is located along the grooves of the stator core, and a rod winding is installed along the grooves of the rotor core or melted aluminum is poured. Special jumper rings play the role of the closing element of the rotor winding. Independent developments transform the mechanical movements of the motor and create alternating voltage electricity. Their advantage is that they do not have a collector-alkaline mechanism, which makes them more reliable and durable.
2. phase rotor- an expensive device that requires specialized service. The composition is the same as that of the short circuit rotor. The only exception is the rotor and stator winding of the core is made of insulated wire, and its ends are connected to rings attached to the shaft. Special brushes pass through them, which combine the wires with an adjusting or starting rheostat. Due to the low level of reliability, it is used only for those industries for which it is intended.

Application area

The device is used in various industries:

1. Like a conventional wind power plant engine.
2. For own independent food of an apartment or house.
3. Like small hydroelectric power stations.
4. As an alternative inverter type of generator (welding).
5. To create an uninterrupted AC power system.

Advantages and disadvantages of the generator

The positive qualities of the development include:

1. Simple and fast assembly with the ability to avoid dismantling the motor and rewinding the winding.
2. The ability to carry out the rotation of electric current using a wind or hydro turbine.
3. Application of the device in motor-generator systems to convert a single-phase network (220V) to a three-phase network (380V).
4. The ability to use the development in places where there is no electricity, using an internal combustion engine to spin up.

Minuses:

1. The problem of calculating the capacitance of the condensate that is connected to the windings.
2. It is difficult to reach the maximum power mark that self-development is capable of.

Principle of operation

The generator generates electrical energy, provided that the number of revolutions of the rotor is slightly higher than the synchronous speed. The simplest type produces about 1800 rpm, given that its synchronous speed level becomes 1500 rpm.

Its principle of operation is based on the conversion of mechanical energy into electricity. It is possible to make the rotor rotate and produce electricity with the help of a strong torque. Ideally, a constant idling, which is able to maintain the same speed.

All types of motors operating on non-constant current are called asynchronous. They have the stator magnetic field spinning faster than the rotor field, respectively directing it in the direction of its movement. To change the electric motor to a functioning generator, you will need to increase the speed of the rotor so that it does not follow the magnetic field of the stator, but begins to move in the other direction.

You can get a similar result by connecting the device to the mains, with a large capacity or a whole group of capacitors. They charge and store energy from magnetic fields. The capacitor phase has a charge that is opposite to the current source of the motor, due to which the rotor slows down, and current is generated by the stator winding.

Generator circuit

The scheme is very simple and does not require special knowledge and skills. If you start the development without connecting it to the network, rotation will begin and, after reaching the synchronous frequency, the stator winding will begin to generate electrical energy.

By attaching a special battery of several capacitors (C) to its clamps, you can get a leading capacitive current that will create magnetization. The capacitance of the capacitors must be higher than the critical designation C 0, which depends on the dimensions and characteristics of the generator.

In this situation, the process of self-starting takes place, and a system with a symmetrical three-phase voltage is mounted on the stator winding. The indicator of the generated current directly depends on the capacitance for the capacitors, as well as the characteristics of the machine.

Do it yourself

To convert an electric motor into a workable generator, you will need to use non-polar capacitor banks, so it is better not to use electrolytic capacitors.

In a three-phase motor, you can connect a capacitor according to the following schemes:

• "Star"- makes it possible to carry out generation at a smaller number of revolutions, but with a lower output voltage;
• "Triangle"- comes into operation at a large number of revolutions, respectively, produces more voltage.

You can create your own device from a single-phase motor, but provided that it is equipped with a short circuit rotor. To start the development, you should use a phase-shifting capacitor. A single-phase collector-type motor is not suitable for rework.

Required Tools

Creating your own generator is easy, the main thing is to have all the necessary elements:

1. asynchronous motor.
2. Tachogenerator (a device for measuring current) or a tachometer.
3. Capacitor for capacitors.
4. Capacitor.
5. Tools.

Walkthrough

1. Since it will be necessary to reconfigure the generator in such a way that the rotation speed exceeds the engine speed, it is first necessary to connect the engine to the mains and start it. Then, using a tachometer, determine the speed of its rotation.
2. Having learned the speed, you should add another 10% to the resulting designation. For example, the technical indicator of the motor is 1000 rpm, then the generator should have about 1100 rpm (1000*0.1%=100, 1000+100=1100 rpm).
3. It is necessary to choose a capacitance for capacitors. Please refer to the table for sizing.

Table of capacitor capacities

Generator power KVA	Idling
	CapacityMKF	Reactive power Kvar	COS=1		COS=0.8
			Capacity uF	Reactive powerkvar	CapacityMKF	Reactive power Kvar
2,0	28	1,27	36	1,63	60	2,72
3,5	45	2,04	56	2,54	100	4,53
5,0	60	2,72	75	3,4	138	6,25
7,0	74	3,36	98	4,44	182	8,25
10,0	92	4,18	130	5,9	245	11,1
15,0	120	5,44	172	7,8	342	15,5

Important! If the capacity is large, the generator will start to heat up.

Choose appropriate capacitors that can provide the required rotation speed. Be careful when installing.

Important! All capacitors must be insulated with a special coating.

The device is ready and can be used as a source of electricity.

Important! A device with a squirrel-cage rotor creates a high voltage, so if you need an indicator of 220V, you should additionally install a step-down transformer.

Magnetic generator

The magnetic generator has several differences. For example, it does not need to install capacitor banks. The magnetic field that will create electricity in the stator winding is created by neodymium magnets.

Features of creating a generator:

1. It is necessary to unscrew both engine covers.
2. You need to remove the rotor.
3. The rotor must be machined by removing the top layer of the desired thickness(magnet thickness + 2mm). It is extremely difficult to perform this procedure on your own without turning equipment, so you should contact a turning service.
4. Make a template for round magnets on a sheet of paper, based on the parameters, the diameter is 10-20 mm, the thickness is about 10 mm, and the swearing force is about 5-9 kg per cm 2. The size should be selected depending on the dimensions of the rotor. Then attach the created template to the rotor and place the magnets with the poles and at an angle of 15-20 0 to the rotor axis. The approximate number of magnets in one strip is about 8 pieces.
5. You should have 4 groups of stripes, each with 5 stripes. Between groups, a distance of 2 magnet diameters should be maintained, and between strips in a group - 0.5-1 magnet diameter. Due to this arrangement, the rotor will not stick to the stator.
6. Having installed all the magnets, you should fill the rotor with a special epoxy resin. Once dry, cover the cylindrical element with fiberglass and re-impregnate with resin. Such a mount will prevent the magnets from flying out during movement. Make sure that the diameter of the rotor is the same as before the groove, so that during installation it does not rub against the stator winding.
7. After drying the rotor, it can be installed into place and screw both engine covers.
8. Conduct tests. To start the generator, you will need to turn the rotor with an electric drill, and at the output measure the received current with a tachometer.

Remodel or not

To determine whether the operation of a self-made generator is effective, one should calculate how justified the efforts to convert the device are.

It cannot be said that the device is very simple. The motor of an asynchronous motor is not inferior in complexity to a synchronous generator. The only difference is the absence of an electrical circuit to excite the work, but it is replaced by a capacitor bank, which does not simplify the device in any way.

The advantage of capacitors is that they do not require additional maintenance, and energy is obtained from the magnetic field of the rotor or the electric current produced. From this we can say that the only plus from this development is the lack of need for maintenance.

Another positive quality is the clear factor effect. It consists in the absence of higher harmonics in the generated current, that is, the lower its indicator, the less energy is spent on heating, a magnetic field and other moments. For a three-phase electric motor, this figure is about 2%, while for synchronous machines it is at least 15%. Unfortunately, taking into account the indicator in everyday life, when various types of electrical appliances are connected to the network, is unrealistic.

Other development indicators and properties are negative. It is not capable of providing the rated industrial frequency of the voltage produced. Therefore, the devices are used together with straightening machines, as well as for charging the battery.

The generator is sensitive to the slightest drops in electricity. In industrial developments, a battery is used for excitation, and in a home-made version, part of the energy goes to a capacitor bank. In the event that the load on the generator is higher than the nominal value, it does not have enough electricity to recharge, and it stops. In some cases, capacitive batteries are used, which change their dynamic volume depending on the load.

1. The device is very dangerous, therefore it is not recommended to use a voltage of 380 V unless absolutely necessary.
2. According to precautions and safety regulations additional grounding is required.
3. Watch the thermal regime of development. It is not inherent to it to work at idle. To reduce the thermal effect, it is necessary to choose a capacitor capacitance well.
4. Correctly calculate the power of the produced electrical voltage. For example, when only one phase functions in a three-phase generator, then the power is 1/3 of the total, and if two phases work, respectively, 2/3.
5. It is possible to indirectly control the frequency of the intermittent current. When the device is idling, the output voltage begins to increase, and exceeds the industrial (220 / 380V) by 4-6%.
6. It's best to isolate development.
7. It is necessary to equip a home-made invention with a tachometer and a voltmeter to capture its work.
8. It is desirable to provide special buttons to turn the mechanism on and off.
9. The level of efficiency will decrease by 30-50%, this phenomenon is inevitable.

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.

(AG) is the most common AC electric machine, used primarily as a motor.
Only low-voltage AGs (up to 500 V supply voltage) with a power of 0.12 to 400 kW consume more than 40% of all electricity generated in the world, and their annual output is hundreds of millions, covering the most diverse needs of industrial and agricultural production, ship, aviation and transport systems, automation systems, military and special equipment.

These engines are relatively simple in design, very reliable in operation, have sufficiently high energy performance and low cost. That is why the scope of the use of asynchronous motors is constantly expanding both in new areas of technology and instead of more complex electrical machines of various designs.

For example, there has been considerable interest in recent years application of asynchronous motors in generator mode to provide power to both three-phase current consumers and direct current consumers through rectifier devices. In automatic control systems, in a servo drive, in computing devices, asynchronous tachogenerators with a squirrel-cage rotor are widely used to convert the angular velocity into an electrical signal.

Applying Asynchronous Generator Mode

Under certain operating conditions of autonomous power sources, the use of asynchronous generator mode turns out to be the preferred or even the only possible solution, as, for example, in high-speed mobile power plants with a gearless gas turbine drive with a rotation speed n = (9…15)10 3 rpm. The paper describes an AG with a massive ferromagnetic rotor with a power of 1500 kW at n = 12000 rpm, designed for the autonomous welding complex "Sever". In this case, a massive rotor with longitudinal slots of rectangular cross section does not contain windings and is made of a solid steel forging, which makes it possible to directly articulate the engine rotor in generator mode with a gas turbine drive at peripheral speeds on the rotor surface up to 400 m/s. For a rotor with a laminated core and short circuit with a squirrel cage winding, the permissible circumferential speed does not exceed 200 - 220 m / s.

Another example of the effective use of an asynchronous motor in the generator mode is their long-term use in mini-hydro power plants with a stable load mode.

They are distinguished by ease of operation and maintenance, they are easily switched on for parallel operation, and the shape of the output voltage curve is closer to sinusoidal than that of SG when operating on the same load. In addition, the mass of the AG with a power of 5-100 kW is approximately 1.3-1.5 times less than the mass of the SG of the same power, and they carry a smaller amount of winding materials. At the same time, in a constructive sense, they are no different from conventional IMs and their mass production is possible at electric machine-building plants that produce asynchronous machines.

Disadvantages of the asynchronous mode of the generator, asynchronous motor (HELL)

One of the disadvantages of AD is that they are consumers of significant reactive power (50% or more of the total power) necessary to create a magnetic field in the machine, which must come from the parallel operation of an asynchronous motor in generator mode with a network or from another reactive power source (capacitor bank (BC) or synchronous compensator (SC)) during autonomous operation of the AG. In the latter case, the inclusion of a capacitor bank in the stator circuit in parallel with the load is most effective, although in principle it can be included in the rotor circuit. To improve the operational properties of the asynchronous mode of the generator, capacitors can additionally be included in the stator circuit in series or in parallel with the load.

In all cases Autonomous operation of an asynchronous motor in generator mode Reactive power sources(BC or SC) must provide reactive power to both the AG and the load, which, as a rule, has a reactive (inductive) component (cosφ n< 1, соsφ н > 0).

The mass and dimensions of a capacitor bank or a synchronous compensator can exceed the mass of an asynchronous generator, and only when cosφ n =1 (purely active load) are the dimensions of the SC and the mass of the BC comparable to the size and mass of the AG.

Another, most difficult problem is the problem of stabilizing the voltage and frequency of an autonomously operating AG, which has a "soft" external characteristic.

Using asynchronous generator mode as part of an autonomous system, this problem is further complicated by the instability of the rotor speed. Possible and currently used methods of voltage regulation in the asynchronous mode of the generator.

When designing an AG for optimization calculations, it is necessary to conduct maximum efficiency in a wide range of speed and load changes, as well as to minimize costs, taking into account the entire control and regulation scheme. The design of generators must take into account the climatic conditions of operation of wind turbines, constantly acting mechanical forces on structural elements, and especially powerful electrodynamic and thermal effects during transients that occur during start-ups, power outages, loss of synchronism, short circuits and others, as well as significant gusts wind.

The device of an asynchronous machine, an asynchronous generator

The device of an asynchronous machine with a squirrel-cage rotor is shown on the example of an AM series motor (Fig. 5.1).

The main parts of the IM are a fixed stator 10 and a rotor rotating inside it, separated from the stator by an air gap. To reduce eddy currents, the rotor and stator cores are assembled from separate sheets stamped from electrical steel with a thickness of 0.35 or 0.5 mm. Sheets are oxidized (subjected to heat treatment), which increases their surface resistance.
The stator core is built into the frame 12, which is the outer part of the machine. On the inner surface of the core there are grooves in which the winding 14 is laid. The stator winding is most often made of three-phase two-layer of individual coils with a shortened pitch of insulated copper wire. The beginnings and ends of the phases of the winding are output to the terminals of the terminal box and are designated as follows:

start - CC2, C 3;

ends - C 4, C5, Sat.

The stator winding can be connected with a star (U) or a delta (D). This makes it possible to use the same motor at two different linear voltages, which are in relation to, for example, 127/220 V or 220/380 V. In this case, the U connection corresponds to the inclusion of HELL at a higher voltage.

The assembled rotor core is pressed onto the shaft 15 by a hot fit and is protected from turning with a key. On the outer surface, the rotor core has grooves for laying the winding 13. The rotor winding in the most common IM is a series of copper or aluminum rods located in the grooves and closed at the ends with rings. In engines with a power of up to 100 kW and more, the rotor winding is performed by filling the grooves with molten aluminum under pressure. Simultaneously with the winding, the closing rings are cast along with the ventilation winglets 9. In shape, such a winding resembles a “squirrel cage”.

Phase rotor motor. Asynchronous mode generator a.

For special asynchronous motors, the rotor winding can be performed similarly to the stator winding. A rotor with such a winding, in addition to the indicated parts, has three slip rings mounted on the shaft, designed to connect the winding to an external circuit. HELL in this case is called a motor with a phase rotor or with slip rings.

The rotor shaft 15 combines all elements of the rotor and serves to connect the asynchronous motor with the actuator.

The air gap between the rotor and the stator is from 0.4 - 0.6 mm for low power machines and up to 1.5 mm for high power machines. Bearing shields 4 and 16 of the engine serve as a support for the rotor bearings. Cooling of an asynchronous motor is carried out according to the principle of self-blowing by a fan 5. Bearings 2 and 3 are closed from the outside with covers 1 having labyrinth seals. A box 21 with leads 20 of the stator winding is installed on the stator housing. A plate 17 is fixed on the body, on which the main data of blood pressure are indicated. Figure 5.1 also shows: 6 - shield seat; 7 - casing; 8 - body; 18 - paw; 19 - ventilation duct.