In every branch of technology you can always find a kind of echo of ancient times, namely the title, reflecting a sort of history of this area.And few know that one or the other technical concept has a long way of development, addiction, and at the very beginning of his birth marked another, often a very significant step of technological progress.For example, among electrical terms it is very common to hear the expression "three-phase voltage," "line voltage", "constant" or "variable voltage" and many other names with the word "tension."
initially as a physical quantity voltage is defined as the potential difference of the electric field, the ability to perform the work on the movement of electrical charge from one point to another field.On the movement of the charge consumed energy field, so its value or, more precisely, the potential difference is reduced to zero.In the actual closed circuit work to move electric charge treated as the electric current - the result of removing electrons from one point to another chain.That he did not change, the potential difference must be maintained unchanged.As we know, keeping current in the circuit "knows" the power supply.From it, depending whether the constant current circuit, i.e.It does not change its magnitude and direction, or variable, changing according to some law.The term "line voltage" only makes sense for AC networks.
most widely used in electrical engineering received AC voltage sine wave.The maximum value of the voltage when the amplitude of oscillation is called the Ua.For such a voltage apply additional units - the frequency F and the phase ψ.The frequency is determined by the number of oscillations per unit time, and phase - time shift is identical swing points.It so happened historically that the term "phase" came to be called and the power line AC voltage if it is part of a system of many phases - usually three.The three-phase networks are another achievement of electrical engineering and have so many advantages that it is simply impossible to pass.And most important of them - this is an opportunity very simple, in fact, without any effort to obtain a rotating magnetic field - the basic principle of operation of any motor.The three-phase circuit distinguish phase and line voltage, and its main feature is that each of the phase shift is in relation to the other two +/- 120 degrees.The generator has a three-phase voltage output winding, wherein structurally specified phase shift.Each coil has an end and a beginning: the H1-K1 and H2-K2-K3 H3.The three-phase system, there are two ways of connecting the phase - "star" and "delta".
When connecting "star" all the ends are connected to one point - "a conclusion 0" and start to serve the terminal ends of the generator and the input to the device energized them.In such a system, the line voltage - is the value measured between any pair of output ends of H1, H2, H3, and denote Ulin.There is another characteristic of the three-phase - phase voltage.Uf is designated and measured between points "0 output", and any of the output ends K1, K2 and K3.Omitting the details, it should be noted that, based on the vector diagram for three-phase network, the relationship between these voltages Ulin = Ѵ3 * Uf.When connecting to a "triangle" the ends of the windings are connected in a ring: K1-K2-N1-N2-N3-R3-K1.Each connection "end - start" is output, while the line voltage is different from the phase, ie,Ulin = Uf.It is interesting to compare between a constant voltage and Udir amplitude alternating voltage Ua, for example, based on the same energy released in the load.In this case Udir = Ѵ2 * Ua.
So for decades been accumulating knowledge of nature and the nature of electricity and discreetly simple concept of "stress" has acquired related terms, enhances our ability to use natural phenomena to human needs.
