Modern life is unimaginable without electricity and benefits that are associated with it.Lack of natural gas is easily offset by solid-fuel heat sources, water is also available, but without electricity comes the real "end of the world."
Most modern power plants generate three-phase alternating current.Among its advantages of particular note are the ease of obtaining and subsequent reforms, high reliability and simplicity of design intended for him induction motors.Three-phase current - is the most common type of worldwide electricity.
System three phase electrical current is a set of three-phase current circuits with the same frequency and amplitude, but mutually offset by 120 degrees (or, what is the same, 1/3 of the period).Each of these circuits is called a phase, respectively, all three form a three-phase current.
Theoretical foundations are simple: metal frame rotates in a magnetic field, crossing the line tension.That in accordance with the law of electromagnetic induction to get an electric current, just connect it to the load terminals and create a chain.If the phase current is required, the device is complicated: the mechanism are three identical frame shifted relative to one another by 120 degrees.The result is the generation of three-electromotive force (EMF).Standard power rotation speed is unchanged.
In practice, the implementation is a bit different from the theory.Three-phase current set up special equipment - generators.They winding phase mains immobile (compare with the theory) and arranged in a certain way at the poles of the stator (the stationary part of the machine).A rotating magnetic field is generated by the rotor.Torque tells him the energy of falling water in hydroelectric, steam turbines in nuclear power plants and so forth.
One of the features of circuits using three-phase current, lies in harnessing consumer-side only three or four wires - three-phase and zero.It is possible to achieve due to the method of connecting the generator windings - star or delta.
Star connection means that the ends of the three windings converge at one point zero.Based on Kirchhoff's law, it follows that the sum of currents at the point (node) is zero, so no fault occurs.From zero output neutral wire.The voltage measured between the conductor and any of the three linear, a 1.73 times smaller than the value of the voltage between the line conductors themselves.In the first case, a phase voltage, and the second linear.
important feature of the star connection is the need to avoid phase imbalance, that is, to control, to the currents flowing in the branches were roughly equal.That little difference is inevitable leads to a small current in the neutral wire, but it is small.
completely different type of connection of the windings of the generator - a triangle, allowing abolition of the neutral wire.With its implementation, each end of the winding is connected to the beginning of the next, in fact, form a triangle, and the voltage is removed from its vertices.In this way, phase and line voltage are equal.It is also necessary to monitor the equality of the currents in the branches have been ignoring, the total current in the closed circuit may become excessive, causing the heat generator and its failure.
Most electric motors designed for three-phase network, provide a choice of ways to connect the windings to the star or triangle.This allows you to select the operating voltage.Thus, when connecting the load windings star rated voltage will be 1.73 times smaller than the triangle.
