Making a generator out of an asynchronous motor with your own hands is not difficult, but you will have to try and spend some money on the purchase of components. But for the work you need to know some subtleties. In particular, the operating principles of an asynchronous AC motor, to study the basic elements of its design. The main thing in generator sets is the movement of the magnetic field. It can be provided by rotating the armature using an internal combustion engine or a wind turbine. It is also possible to use alternative sources - the strength of water, steam, etc.
Induction motor design
You can select just a few elements:
- Stator with a winding.
- Front and rear covers with bearings installed.
- Squirrel cage rotor.
- Contacts for connecting to the electrical network.
If you think about it, it may seem that it is very simple to remake the engine into a generator, a photo of which you can examine in detail. But if you look more carefully, it turns out that not everything is so simple, there are plenty of pitfalls.
The stator consists of many metal plates pressed tightly to each other. They are also varnished, in some designs, to give strength, all plates are welded to each other. A wire is wound around the stator, it fits snugly to the core and is isolated from it with cardboard inserts. Bearings are located in the covers, with their help not only the rotor is rotated more easily, but also its centering.
Engine operating principle
The essence of the whole process is that a magnetic field is formed around the stator winding. It is powerful enough, but lacks the main component - the movement. The field is static, motionless, and the main condition in generator sets is rotation, a change in the direction of the lines of force. In the case of the engine, everything is quite simple - there is a rotor, which is made of metal. Inside are several turns of a very thick cable. Moreover, all turns are closed, interconnected.
It turns out the principle of a simple transformer. In short-circuited turns, an EMF is induced, which creates an alternating magnetic field in the surrounding space. It turns out that now everything is there in order for the movement to appear. Under the influence of forces, the rotor of the electric motor rotates. This type of machine has good characteristics, and the design is simple and reliable, there is nothing to break. For this reason, induction motors are widely used in industry. More than 95% of all motors in factories are asynchronous. Everyone can make a generator with their own hands, the circuit of which is not very complicated, with minimal knowledge.
Connection to a single-phase network
The true problem is connecting a three-phase electric motor to one. The principle of the generator is slightly different, but to understand it you need to consider the process of the motor. It is necessary to use a tank that will allow you to make a phase shift in the right direction. Moreover, there are several schemes used in practice. In some, the capacitor is used only at the time of startup, in others and during operation. The starting capacity is turned on for a short period of time, until the required speed is reached. It contacts through a switch parallel to one of the windings connected by a triangle circuit.
Such connection options have one significant drawback - a decrease in electric motor power. You can get from him as a maximum 50 percent return. Therefore, with a motor power of 1.5 kW, in the case of power from a single-phase network, you can only get half - 0.75 kW. This imposes certain inconveniences, since it is necessary to use more powerful electric motors.
How to get three phases from one
For more convenient use of electric induction motors, three-phase power is required. But not everyone can conduct such a network to their home, and there are also difficulties with electricity. Therefore, you have to get out, as it turns out. The easiest way to install a frequency converter. But its cost is high, not everyone is able to allocate such an amount for their own garage or workshop. Therefore, you have to use improvised means. You will need an induction motor, capacitor and autotransformer. As the latter, you can use a homemade device made from the core of an electric motor. You can even make a generator drawing to simplify the assembly work.
About 400 turns of wire are required to be wound on it. Its diameter is about 6 square meters. mm For accuracy, ten taps are required to make phase adjustments. You can even say that this is a self-made generator made of an asynchronous motor. Only its main function is transformation, phase shift. One winding is connected to the phase, a capacitor is connected between the other two. The second winding is connected to zero, the third is connected there, only through an autotransformer. Its average output is one phase, the other two are the conclusions of the outlet.
What to consider for conversion to a generator
To make a wind generator out of an (asynchronous!) Motor, you need to consider one main feature. Namely, to create a magnetic field that will make a movement. There are two ways to achieve this. The first is the installation of permanent magnets on the rotor. The second is to make the field winding at anchor. Both methods have both advantages and disadvantages.
You need to decide before starting work what type of current generator you need. If you need a constant, then you need to use diodes for rectification. This will provide light to a small house, as well as power almost any household equipment. Homemade current generators can even be driven by wind. It is only necessary to calculate the windings so that the output does not exceed the voltage. Although stabilization can be done by using the regulators used in automotive technology.
Permanent magnets or field winding?
As mentioned earlier, you can make an excitation winding or carry out the installation of permanent magnets. The disadvantage of the latter method is the high cost of magnets. And the minus of the first is the need to use a brush assembly to provide power. He needs care and timely replacement. The reason is friction, which gradually eats up the surface of the graphite brush. Any car generator, the instructions of which are always attached, has just such a drawback.
To make the field winding, it is enough to change the design of the armature. It should be metal, a wire in varnish insulation must be wound on it. It will also be necessary to establish contacts on one edge of the rotor that are used for power supply. But the plus is that it is possible to stabilize the voltage at the output of the generator. It will be easier to make anchors in the anchor for mounting niode magnets. They create a very strong field, which is enough to generate large values of voltage and current.
How many phases do you need to output?
The easiest way, of course, is to make a generator, the photo of which is shown if the output should be only one phase. But there is a snag - not every design allows this. A home-made generator from an induction motor of this type can be made if all the windings are brought out and not interconnected. Many models of motors have only three outputs, the rest are already connected internally, so to implement the idea you need to completely disassemble it and bring the necessary wires out.
Then they are connected in series and a single-phase voltage can be obtained at the output. But if you need a three-phase, it does not cost to do anything, modernization of the windings is not required. But you still need to take into account the features. It is necessary that a generator made of an asynchronous motor, made by oneself, have a connection of windings according to the star scheme. Here is a slight difference from the option when the machine works as a source of movement. Efficient power generation is only possible when the star is turned on.
How to rectify the current?
But if there is a need for direct current, you will need knowledge of circuitry. Need 12 or 24 volts voltage? Nothing is simpler; automotive electronics come to the rescue. But only if the field winding is used as a magnetic field generator. When using permanent magnets, the stabilization procedure is complicated.
The rectifier option is selected based on the number of phases at the generator output. If there is one, then a bridge circuit is sufficient, or even on a single diode (a half-wave rectifier). If there are three phases at the output, then there will be a need to use six semiconductors for rectification. Also, three pieces (one for each phase) - to protect against reverse voltage.
How to make one phase out of three
This action does not need to be carried out, since it is simply meaningless. If the generator generates a three-phase alternating voltage, then to power consumers (TV, incandescent lamps, refrigerators, etc.), it is necessary to use only one output. The second is the common, connection point of the windings. As mentioned earlier, it is required to connect them in a star pattern.
Therefore, you have the opportunity to connect consumers to one of the phases. The question is, does it make sense, is it rational to do so? If it is necessary to provide the house exclusively with light, you do not plan to connect any consumers, then it is more reasonable to use low-power LED lamps. They consume a small amount of electricity, so the current generator, which delivers stably 12 Volts, is able to provide the house not only with light. You can easily turn on household appliances that require just such voltage to work.
Wire winding rules
Such information is not always needed, since, in order to simplify the design, the stator winding that is already available is used. But she does not always satisfy the conditions that confront you. For example, if you are constructing a wind generator from a (asynchronous) motor, it is not possible to obtain a minimum number of rotor revolutions. Therefore, the output voltage will be small and insufficient for the operation of household appliances. Therefore, there is a need for small alterations.
The winding must be carried out with a thicker wire in order to obtain a higher value of the output current. To do this, get rid of the old wire. The winding is close to the cardboard frame. When it is carried out, it is required to apply a layer of varnish, soak the wire with it. Just do not forget to dry thoroughly before using the device. To do this, install a 25 or 40 W incandescent lamp in the middle of the stator and leave it for 1-2 days. Do not leave unattended only.
Experimental determination of the required number of turns
To determine how many turns you need for normal operation of the generator, you will need to use many formulas. But you need to know the cross section of the core, the material from which it is made. But this is often simply impossible to determine. Therefore, you have to do experiments. Depending on whether one or three phases you need, the algorithm of the experiment changes. A home-made generator from an induction motor can be made by various methods.
If you plan to make one phase at the output, then reel 10-20 turns of wire evenly around the entire core. Assemble the entire structure and connect to the drive that you will use in the future. Measure the output voltage, divide by the number of turns that are wound. And you get the voltage taken from one turn. To calculate the length of the winding, you need to apply a simple calculation - divide the voltage (necessary) by the obtained value. The calculation of a three-phase generator is carried out similarly .
Making a generator from an asynchronous motor with your own hands is not difficult. The most important thing is to decide which drive you plan to use. If this is a regular gasoline engine, then no problems will arise. Great difficulties will arise if you use a windmill as a drive. The reason is the engine speed, as well as the output voltage, are directly dependent on the strength of the wind, its speed. Therefore, such generators must be calculated in such a way that even at minimum speed, a rated voltage is generated. But at the output it is desirable to have no more than 12 volts. This will prove to be a simpler solution.