The constant increase in the cost of electricity makes many think about the need to organize an independent system of their own energy supply. In addition, sometimes this is the only way to equip with electricity of good quality. The search for solutions to the problem of self-supply with voltage leads to the need to understand how the generator is made.
Although now there are quite a few revolutionary solutions that allow you to get electricity practically “from nothing”, they do not find practical application, being not always functional, giving way to the time-tested version with an electric motor.
Prerequisites for creating a generating device
To learn how to make an electricity generator, you should remember the basics of electrical engineering. In the section devoted to engines, it is clearly indicated that any of them can work not only as a consumer, converting the work of charge into mechanical energy of rotation of the shaft, but also in the opposite mode, converting the mechanical moment into potential at the terminals. This feature is called the law of reversibility of electrical machines. Actually, this is the basis of how the generator is made.
Engines
When choosing an electric motor, you should know that they can be direct or alternating current. Since when considering how the generator is made, most often they mean precisely “change”, then we will not talk about “constant”.
AC machines exist in variations with a phase and squirrel-cage rotor. In the first case, the ends of the windings are displayed on a special device with a set of contact pads, the power supply to which is performed using graphite “brushes”. Using such solutions as a generator is more complicated.
Principle of operation
To understand how the generator is made, it is necessary to represent the processes occurring in the engine during operation. Consider a three-phase model. When power is applied to the terminals of the stator winding (fixed part), a magnetic field appears in it, the tension lines of which intersect the closed rotor winding (rotating "drum"). Due to this, a current is induced in the latter, which generates its own magnetic field. The interaction of these two fields creates a torque. So simple.
Therefore, based on the law of reversibility, it is necessary to unscrew the rotor by external action, and to remove voltage from the stator windings. In generators sold in retail chains, torque creates a gasoline engine. Although the efficiency of such a system is small, it works.
A few nuances
People who have already studied how the generator is made know that there are a number of features of the connected circuits. Having unwound the shaft and connecting the load to the terminals, it will not be possible to fully reveal the potential of the device. The reason for this lies in the fact that no current arises in the turns of the rotor winding (the magnetization is small and fades). To solve this problem, an effective solution is used: a block of capacitors connected by a triangle is placed between the three terminals of the three-phase motor under consideration. That is, a wire from the terminal of the stator winding is connected to each corner, and three leads to the load depart from here. Non-electrolytic type capacitors should be used, such as MBGT, MBGO, etc. Their voltage should be at least 600 V. The capacity depends on the load (the more powerful it is, the higher the class of capacitors) and the characteristics of the motor. For example, for a 2 kVA generator, the battery capacity is at least 28 μF.
It is not recommended to use a generator without load due to the resulting heating. It should also be noted that for a three-phase electric motor, from which 220 V is removed in the generator mode, the power will be one third of the passport.
The shaft rotation speed should not be lower than synchronous. Otherwise, a decrease in frequency and / or voltage is observed.
Most often, the question arises in people: "How to make a wind generator?" Everything is logical: the wind is a free resource that is always available. The composition of such a solution includes: an engine; blades on the shaft, tuned to a certain angle; block capacitors. If it is initially planned to generate low voltage, then an additional inverter and battery will be required.