The Universe has provided mankind with a trillion ways to generate electricity, each stage of development is characterized by its own technologies. Suppose, historically, the first considered a generator of constant charge Van de Graaff. Wrong point of view. People used before other species. Today we consider the device, the principle of operation of the alternator. Let's get started
. Work of the
electric current generators The principle is intended to create a potential relative to the Earth, which is considered to be zero. Wrong, but everything in the world is relative. Although the ground surface carries a charge, the potential difference between the generator terminals and the soil plays a role. The object standing on the ground is enveloped by the field of the planet, we consider the postulate to be correct. The first invented DC generator. Rather voltage. The voltage turned out fantastic, the device gave a little current. The principle of operation is simple:
- Tape rubs, a charge is formed locally.
- By the conveyor mechanism, the section reaches the current collector.
- The conductivity of the ball-type terminal block is equalized.
As a result, the sphere acquires a charge with a density equal to the local tape. It is clear that such generators are not very convenient, in 1831, Michael Faraday creates something new. Using a magnetized horseshoe horseshoe, a rotating copper disk received electricity in a different way: the phenomenon of magnetic induction. Current out alternating. Consequently, the field has ceased to be static, becoming electromagnetic. Let us explain:
- In nature, electricity charges of a positive or negative sign are often encountered, no one has been able to track down the poles of a magnet separately.
- The alternating electric field causes the corresponding response of the ether. Expressed by the production of a variable magnetic component in the plane perpendicular to the original.
The process continues uninterruptedly, called an electromagnetic wave. Develops free space in a straight line, until the energy dies out. As for the wires, the electricity is relatively simple. But! As long as the cable is braided. The screen is gone, zeroing( grounding) is absent - the wave begins to radiate. The effect is exploited by wireless screwdriver indicators, help to establish( localize) sources of industrial frequency interference 50 Hz. And if the computer system unit is not grounded, with the help of things you can easily fix the defect.
Helps check harmful radiation of displays. The frequency of 50 Hz is easily radiated by wires. Aspect increases power plant costs( losses), harms the health of citizens. How does energy arise in the Faraday generator? School teachers were explained: when the frame rotates in the field of a magnet, the induction through the area changes, an electric current is induced.
The mechanical energy of the movement is converted into electrical energy. We guessed, humanity exploits:
- Fall from the dam down the mass of water.
- Energy steam thermal, nuclear power plants.
The two main mechanisms for obtaining energy. Electricity becomes the motion of the turbine blade of the generator. Nature gave birth to devices that burn diesel fuel, kerosene, the principle of operation is slightly different. The difference is limited by mobility, the speed of rotation of the blade.
Generation of electric energy of cities
Let's look at the device of the generator of hydroelectric power station. For the accumulation of potential energy driven by the river channel waters erect a dam. Level upstream quickly begins to rise. To avoid a breakthrough( of any type), part of the multi-ton mass is etched( in some places special gateways are set up to allow fish to spawn).The useful part of the flow passes through the guide vane. Familiar with the device jet engines, understood it. The guiding apparatus is called the configuration of the valves, the change in position is governed by the number of passing medium( leading).
They said in the reviews that the strict requirements for the frequency of generated electricity are regulated. Scientists have calculated: you can achieve at the current level of development, using massive blades, which are not affected by small wave hits. The average mass of the passing water is taken into account, small jumps are concealed by the utter mass of the screw. Obviously, having weighty dimensions, the rotation speed is powerless to make 50 Hz( 3000 rpm).The blade does 1-2 rev / min.
The screw rotates the generator rotor. Moving axle seated by field windings. Coils through which direct current is passed to create a stable magnetic field. Radiation does not occur, the value of tension is constant( see above).Implicit fluctuations are observed, the result does not affect the essence of the process: the shaft is formed by several rotating magnets.
There is a subtle point: how to get a frequency of 50 Hz. Quickly came to the conclusion: to rectify the alternating current, after putting the inversion inverter unprofitable. A multitude of wire coils( frame from Faraday experiments) were placed along the stator, in which induction would be induced. By correct switching from the generator it is possible to remove the necessary 230 volts( in fact, there are also step-down transformers) with a frequency of 50 Hz. Generators give three phases shifted by 120 degrees. There is a new question - to ensure stability. Serve a dosed amount of water while the blade picks up speed? It is practically impossible to do the following:
- In addition to the collector coils, the stator contains exciters.
- There is a voltage applied to the frequency allowing the blade to pick up the desired speed.
- The result is actually a huge synchronous motor.
The initial acceleration is overtaken by the flow of water, the auxiliary voltage keeps the screw trying to exceed the specified speed. Water actually pushes the engine, the excitation voltage will serve as regulation( of course, an alternating current is applied to the stator).It is required to get more power, the dam guide device slightly opens. The mass of water becomes more solid, would certainly have frustrated. It is necessary to increase the excitation current of the stator, the control field becomes stronger, the situation remains within normal limits.
Generator power increases. And the voltage maintained level? According to the Faraday electromagnetic EMF voltage, the voltage is determined by the rate of change of the magnetic field, the number of turns. It turns out, constructively choosing the area of the coils, the cable length, set the output voltage of the generator. Of course, everyone should have their own speed of rotation of the blade. It is sustained by rotor excitation currentWith increasing power increases the emf. The growth of the excitation current increases the rate of change of the magnetic field strength.
Need a way to maintain the previous settings. Often become decoupling transformers with variable transmission coefficient. The consumer changes the current, the voltage remains constant. Parameters specified by the standards are provided. The device of the alternator is based on the excitation of the stator windings, the rest is reduced to the methods of regulation parameters.
Adjusting the parameter of alternators
In the simplest case, the power can not be changed. In household( small generators) the circuit monitors the voltage, the value of the excitation current changes. Rarely, the situation on the hand of the consumer. Consumed diesel fuel. It turns out that the previous energy is wasted, a part is dissipated by space. It's not scary when we return part of the speed of the river to the Earth, a rare miser wants to burn fuel for nothing.
Readers understood: revolutions will break down, if not reduce the flow of water, gas, steam - in general, the driving force. Keeps track of a separate regulation chain, equipped with adjusting mechanisms. It is better for a private house to create a battery system; today, it is possible to supply lighting, laptops, and many other devices with 12 volts of direct current. The network can be equipped with a tap to periodically charge the batteries. As we remember, there are two methods:
- With a constant current. Voltage varies, one-tenth of capacity is charged every hour. The duration of the process is 600 minutes.
- With constant voltage. The current drops exponentially, at first it will be relatively large values. The main drawback of the technique.
The principle of operation of the alternator will allow charging batteries, guided by necessity. It is clear that an isolation circuit is needed before a cascade of batteries. You can guess from the read, HES use devices with adjustable transformation ratio. Techniques for implementing an undertaking may be different:
- Transformers with switched windings have become widespread. The number of turns can be changed by switching the contactors of the circuits.
- A smoother coefficient provides a sliding contact. Here the turns of one coil are cleaned, the current collector runs back and forth, changing the number of working turns. Clearly, it is difficult to miss a large current, a spark will arise, in the case of a hydroelectric station it will become an arc. Rather, the control device is relatively low power.
It follows from the above: it is logical to change the excitation current of the hydroelectric station rotor in steps to the switching time of the control transformer. Then there is a smooth adjustment, the voltage parameters return to normal. They told in general how the alternator works. It should be noted: the construction of the manifold is not exhausted. The described type of devices constitutes the backbone of a family called synchronous alternators. Provide cities, for the most part, with energy.
Asynchronous generators are characterized by the absence of electrical connection between the stator and the rotor. The speed is regulated by the guide vane. In accordance with the frequency stability decreases, the voltage amplitude is also variable. As a result, the relative simplicity of the design of an asynchronous alternator can be noted, the stability of the parameters does not shine with good performance.
A distinctive feature is the ability of asynchronous motor deficiencies to smoothly migrate, infecting new devices. Obviously, to supply consumers with energy regulate the frequency of the current, the power is random. Although, if the generator is in a relatively constant environment, this will not be a big problem.