AC power sources. DC and AC

Anyone who has chosen to work with electrical engineering as a profession should have a very good understanding of what kind of power supplies are available, what are their features and differences. In fact, there is nothing complicated, which we will show in this article.

It is difficult to imagine what the modern world would look like, disappear from it electrical energy and related electrical appliances. Probably, mankind would still use steam engines and muscular strength of animals and their fellow humans. It is impossible to say unequivocally who exactly for the first time discovered electrical energy: for example, spinners in ancient Syria used the property of amber to magnetize (electrify), Aristotle tried to study the possibilities of an electric ray, but the danger of lightning is known since the beginning of the world (not without reason, some nationalities deified it).

Electric current is of two kinds - variable and constant. This difference is due to the way it is obtained. Accordingly, the AC power supplies output a current of the first type, and a constant one of the second type. By the way, here the division into "first - second" is conditional. In electrical engineering, both AC and DC power supplies are used. Let's recall a bit of theory.

Any electric current is a movement of charged particles, guided by a conductive material by the electromotive force of the EMF. The external action informs some electrons located in the outer orbits of the atoms, additional energy sufficient to overcome the attraction of the nucleus. As a result, free charge carriers appear-ions and electrons. According to the law of conservation of energy, a process of natural recombination of particles occurs at nearby atoms at lattice sites. Without external influence, the structure of the material will be restored. However, if a source of EMF is connected to the conductor, then the field generated by it directs recombination in the required direction - an electric current arises. The AC source is actually an EMF generator whose directivity vector periodically changes to the opposite one. Hence the name "variable". AC power sources in most cases are represented by generating powers - generators in modern power plants create exactly alternating current. They are more reliable in operation and easier to maintain than collector models for direct current. In circuits, AC power supplies are often indicated by a circle with a wave inside. This wave is a symbolic image of a sinusoid.

The AC source creates the motion of the particles not only with a changing direction, but also with a "floating" active value. The sine wave itself indicates that periodically the value passes through zero.

Absolutely on the other principle sources of direct current are based. They create in the conductor a constant in the direction of the electric field, which forms the directed motion of the particles with charge. It is generally assumed that the current flows from the positive to the negative (from positive to negative). In reality, however, the movement of electrons occurs in the opposite direction - from minus to plus. Since the charge of a single electron is negative, the pole with a minus sign indicates an excess of these particles (hence the total charge). Proceeding from the fact that unlike charged particles are mutually attracted, it is not difficult to guess that the electrons along the conductor move from "minus" to "plus". Artificial change of the current value is allowed - from this the current does not cease to be constant. There are a lot of different solutions that allow you to convert DC to AC (sinusoid generators) and vice versa (rectifiers, bridges).