A person without engineering education, when asked what an electrical network is, will immediately name several of its characteristic components, among which it will almost certainly be mentioned transformer. If such a person constantly encounters wires and sockets at home, then he knows about the transformer from the transformer booth and from that characteristic buzz that is heard from behind closed doors.
So why is this electrical grid component so popular and how does it work? The second part of the question is far from superfluous. the transformer has no intuitive and familiar moving parts.
Basic physical processes in a transformer
An electrical network for any purpose is based on the use of electrical energy to perform mechanical work (power electrical engineering) and transfer information (telecommunications). This energy can exist in the form of two fields: electric and magnetic.
Electric and magnetic fields are closely related. It is known that a metal contains a large number of free electrons, which determine its high conductivity. If a metal object is held through a magnetic field, electrons move with it, which means the occurrence of an electric current. It is important that this process is reversible, i.e. an electric current creates a magnetic field around the conductor.
Now let's imagine that in a certain pair of wires 1-2 there is an electric current I. Then, provided that this current I is variable, it is possible to achieve the appearance of current and / or voltage in another a pair of wires 3 - 4, provided that these pairs interact with each other through an electrical or / or magnetic fields. Figure 1 depicts these processes in schematic form.
Thus, it becomes possible to implement the connection between two different circuits of current flow without their direct connection to each other.
It is convenient to make the primary (conductors 1 and 2) and secondary (conductors 3 and 4) in the form of windings. Then the ratio between currents and voltages in the primary and secondary circuits is completely determined by the number of turns primary and secondary windings, which, in turn, means the possibility of creating a current transformer (converter) and voltage.
In addition, the transformation process itself is conveniently organized through the magnetic component of the electromagnetic field.
Increasing the efficiency of the transformer
In the process of transferring electromagnetic energy from the primary winding to the secondary, only those lines of force of the magnetic field that intersect the turns of the secondary winding are involved. Taking this feature into account, the so-called. a core made of electrical steel, which creates a noticeably lower resistance to the magnetic field compared to air.
As a result, the lines of force of the magnetic field created by the primary winding pass mainly through the core and interact with the secondary winding, Figure 2. This, by the way, explains the second name of the core as a magnetic circuit.
Core design
The first examples of core transformers had significant losses, which were caused by the so-called. eddy currents. They arose due to the fact that an alternating magnetic field generates currents not only in the secondary winding, but also in the core itself.
To suppress this undesirable effect, the core is assembled from thin plates that are insulated along the plane of contact. Figure 3 schematically illustrates the eddy current suppression in the transition to such a design.
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