Phase can often be heard in a conversation about electricity. But, of course, the word has a much broader meaning. What is a phase, its cycles, how is it connected with grounding. We will learn about this and much more in the next article.
What is phase
In physics, a phase is understood to mean one of the states of a substance (for example, water is in a liquid, liquid crystalline, crystalline and gaseous state of aggregation). In addition, it means a stage in a cycle of oscillation (for example, in wave motion).
In astronomy, the word has a slightly different meaning. What is the phase in this science can be understood from observations from the Earth of a celestial body (for example, the Moon). That is, it can be designated as the visible part of the illuminated hemisphere of a celestial object from the Earth.
In the theory of economics it is widely known what the phases of the cycle are. This is when in a certain period of time (cycle) a regular activity is observed.
Consider what this term implies in electricity.
Phase in electricity
Do you know where electricity comes from power plants? Everywhere the principle of its occurrence is the same: the rotation of the magnet inside the coil leads to the fact that an alternating current appears in it . This effect is called EMF, or electromotive force of induction. A rotating magnet is called a rotor, and coils attached around it are called a stator.
Alternating voltage is obtained from constant, when the latter is bent along the sine, as a result of which its positive or negative value is achieved.
So, the magnet comes into motion, for example, due to the flow of water. When the rotor rotates, the magnetic flux changes all the time. Therefore, an alternating voltage is created. With three coils installed, each of them has a separate electric circuit, and the same variable value appears inside it, where the voltage phase is shifted around the circle by one hundred and twenty degrees, that is, by a third relative to the one located next to it.
Or, to feed at home as before?
This scheme is called three-phase. But you can safely power the house and with the help of one such coil. In this case, the first end of the coil is simply grounded, and the second - lead to the house, where this wire is connected, for example, to the plug of the kettle. The second pin of the plug is earthed. Get the same electricity.
Three-phase current distribution
Three-phase current flows into homes through power lines (where the voltage reaches thirty-five kilovolts). It is believed that it is the most economical and on all sides more profitable compared to conventional current.
In industry, power is supplied by just a three-phase current, since it is easier to build a rotating structure on it, and in general it is more mobile and has more power.
Wires
We will understand what phase, ground and neutral wire are, in more detail.
It is easy to imagine a three-phase generator with a star connection. The phase connection point is called neutral.
Usually it is grounded to increase safety, since if the device fails, then in the absence of grounding, a danger to humans will be created. When you touch the device, it will simply be shocked. But if there is grounding, an excess current will leak and no risk will be formed.
So, all together - the neutral wire, the earth and the phase of the wire are necessary to ensure the safety of people. In new houses under construction, such a system is provided, while in old ones it is absent.
Phase determination
Sometimes it is necessary to determine where the phase wire is located. For a conventional outlet, this may not be necessary. But when connecting, for example, a chandelier, the phase should be fed directly to the switch, and zero - directly to the lamps. Then, if the light is turned off, when replacing the lamp a person will not be shocked. And even when the device is on, if it accidentally touches the lamp, although it will be hot, it will not happen.
There is a very simple and convenient device for determining the phases. In appearance, it resembles an ordinary screwdriver. But inside the device has a light bulb that, when you touch the phase, will light up. In this case, the finger should touch at this time the metal patch of the device.
Some daredevils decide to determine the phase completely unsafe methods. These include the so-called "control", when the wire is substituted under a stream of water, they are touched by a neon bulb or brought into contact with the battery.
Needless to say, it is better not to resort to methods that become dangerous not only for the experimenter, but also for others. Moreover, an indicator screwdriver is currently very inexpensive.
If the electrical cables are installed correctly in the rooms, the blue wire will indicate zero, yellow-green will indicate ground, and the phase will be indicated with black or any other color. But the work of electricians, unfortunately, is not always conscientious and qualified. Therefore, the colors may not match the purpose.