Scheme, features, operating principle and the device of the generator of a direct current

The era of electrification began not so long ago and for a couple of centuries completely changed our way of life. Look around, everywhere, where only the eye falls, you will definitely see some electrical appliance. People are so used to different machines that do almost all the work for them, that there is an illusion, as if it were always like this. But let us look beyond the veil, hiding from us the process of vital activity of electric friends. Let's analyze the principle of operation and the device of the generator of direct current.

A bit of history

Electricity was observed by the ancient Greeks. It was noted the property of amber to attract different particles to itself. People considered this to be the magnetism inherent in resin. But later they noticed the ability of other materials to acquire magnetism. For example, glass when rubbing, too, began to attract small light elements: particles of paper, hairs and dust. So it became clear that the magnetic effect occurs by some law.

Subsequently, in the XVIII century, a prototype of a modern capacitor was created, baptized by the name of the inventor "Leiden bank." This simple mechanism was able to accumulate a charge, which at that time was considered a kind of fluid, saturating solids and capable of flowing from one body to another with astonishing speed - several miles in fractions of seconds.

When the atom and its constituent nucleus and electron were discovered, everything fell into place. People realized that it was the electrons that were the charges that created such inexplicable phenomena as electrical discharges. But while it was only static charges. With the experiments of Faraday and Oersted, electricity begins, which we know now. They invented a DC -generator layout , the device and the principle of operation of which are based on the phenomenon of EMF electromotive force.

The strength of the electricity movement

As the water of the river sets in motion the attraction of the earth, so charged particles in the conductor cause the EMF to move. This force is closely related to the magnetic phenomenon, namely, it appears as soon as the flux created by the magnet changes. EMF is able to work only in a substance where there are always available charges. This property is possessed by metals and saline solutions.

The emf is the larger, the faster the intensity of magnetic waves changes. As you know, a magnet has two poles always. In accordance with the direction in which the flow changes with respect to the conductor, the current in the conductor flows in one direction or another. Positive and negative charges themselves create an energy field between ourselves, which we call a voltage, it is the greater, the stronger the total electric charge of the eponymous pole.

What is an electric generator?

The design or machine that is capable of converting any mechanical force into electrical energy has been called the electricity generator. The principle of operation and the device of a direct current generator are related to magnetism. If we take a permanent magnet and cross the field of its strength with a conductor, then in the latter there is a force that forces the charged particles to move in one direction - a current appears. The same will happen with a fixed conductor and a moving magnet.

Experimentally, scientists have established that the value of the current is the greater, the greater:

• The magnitude of the magnetic flux between the poles of the magnet.
• Speed of intersection of tension lines.
• The length of the current-carrying wire.

If, however, the conductor is moved parallel to the direction of the flow, no induction is observed in it. This led to the law of the right hand, which helps to understand in which direction the current moves. When the hand of the right side of the body is placed with the palm of the hand so that the magnetic lines of the stressed field enter into it, and the thumb is bent and pointed where the conductor moves, the remaining four fingers show the current path. In the magnet, the motion vector of the field is directed from north to south.

Operation scheme of the elementary generator

The principle of operation and the device of a constant-current generator of a simple type are as follows: the frame is made of current-carrying material, is mounted on the axis and rotates between the poles of the magnet. Each free end of the frame is connected to its contact, which looks like an arcuate plate. Together, the contacts form a circle torn in two points (collector). These semicircular contacts are movably connected to the spring-loaded conductive brushes. They remove the current.

In space, the frame relative to the contacts is oriented so that when each half of the sections of the largest magnetic flux cross each other, the brushes are closed at the contacts. When the frame elements go through a phase of movement along the lines - the brush contacts are open to the collector.

If you connect an oscilloscope, you can see that the DC generator device and the principle of operation have such that it produces an alternation of half-waves that are on one side of the coordinates and change their value from zero to the highest and again to zero. The frequency of their follow depends on the speed of the rotation of the frame. This means that the current in such a system moves in one direction (constant), but has a pulsating appearance.

Principle of operation and the device of the generator of a direct current

A real constant current generator is more complex, although the principle of its action does not differ from the one considered above. Instead of a single frame and a pair of semicircular contacts, it has many frames and contacts of the collector. This, firstly, increases the power of such a machine, and secondly, it smooths the ripple of the current, since each frame creates its own half-wave, which, when tuned to each other, form a total current. Such a rotating system is called an anchor or rotor.

The magnet of the generator is also modified. Its role is played by an electromagnet consisting of a winding and a core. Using electromagnets, you can create a large magnetic flux, which is beyond the power of the usual permanent. In addition, the flow can be easily changed. The stationary part of the generator is called the stator.

Depending on the operating mode of the machine during shaft rotation, the following processes are observed between the stator and the rotor:

1. No load is connected to the generator. In the case of such idle work, the armature generates a rotation, EMF is induced in it, but there is no current in the winding, since the circuit is not closed.
2. The DC generator, whose device circuit is connected to the circuit, operates in the load mode. In this case, the current flows in the armature and a new component appears-the magnetic flux created by the armature (armature response). This stream moves in such a direction that it counteracts the main lines of force created by the electromagnet. As a result, the real EMF will be lower, that is, the generator's power is reduced. And the more the generator load, the more energy is spent to overcome the reaction of the armature when the shaft rotates.

In order to level the magnetic flux of the armature, so-called compensatory windings are introduced into the rotor circuit, in which a magnetic flux is formed, which weakens the armature response.

Types of generators producing constant electricity

The principle of operation and the arrangement of DC generators differ in the execution of the excitation circuit. They are:

• Magnetoelectric. They use permanent magnets to create a magnetic flux. Such machines, usually of low power, have a high efficiency, since there is no loss in the field windings. The lack of devices in the complexity of regulation.
• Generators with independent excitation circuit. These are devices whose winding of electromagnets is powered from external power sources: a battery or a generator.
• Self-excited DC generators. Such devices feed electromagnets from their own anchors. The main condition for self-excitation is the residual magnetic flux. The design, the principle of the operation of the generators and the scheme of their activation is compound, shunt and serial.

Principle of operation and the device of the generator from the electric motor

The principle of reversibility of electrical machines suggests that any electric motor can be converted into a generator and vice versa. After all, both of these devices use EMF induction, as the basis of their work. Only in the motor is an electric current applied to the rotor, which, creating a magnetic flux, repels from the poles of the stator magnet, making a rotational movement.

If the motor shaft rotates at a certain speed, the induction windings begin to be induced in the armature windings and the current will flow. The restriction is only in the thickness of the armature winding wire. When the wire is thin, then it will not be possible to get more power from such a generator.

Where did you find the DC source?

Despite the fact that permanent electricity can be obtained by the method of rectifying an alternating current, a DC generator is widely used. The principle of operation, the scheme of such a machine is indispensable in metallurgical enterprises, in powerful electrolysis plants of plants. In the transport industry, the units operate in electric locomotives, ship ships. DC power sources are also suitable for powering the exciting windings of alternating current generators in power plants. For domestic purposes, dynamo-current machines have been developed. They can be seen on bicycles, where they feed the lights.

Conclusion

Current generators of constant polarity are good in that they can produce electricity at different rotational speeds of the shaft. They do not need to withstand a clear frequency, as, for example, in alternators, where it should be at 50 Hz. Such machines are very convenient to use as alternative sources of electricity, for example in wind turbines.