Today the topic of the article is reactive power. With this word, many people, for some reason, imagine a jet turbine.
But no! Reactive power occurs in alternating current networks. Right off the bat, I’ll give you an example that you’ll understand right off the bat.
Let's imagine there are two girls, both come to the dacha. One comes to work, and the other comes to relax and goes back home.
One girl can be safely called active power (denoted as P), and the second one can be called reactive power (denoted as Q).
Active power is generated at sources, well, let's say at power plants, it comes to the consumer and there it is converted into useful work. For example, a light is on, an electric stove is working, and reactive power comes and goes back to the power plant. And so it constantly "rushes" back and forth, back and forth.
And why does it arise at all? Why is reactive power needed? Why would she "run from the power plant to the consumers"?
The whole reason lies in the details, as they say. Namely in inductive elements. We have elevators at home, factories have machines, machines have motors, and motors have windings, and windings are inductive loads.
When an alternating current flows through an inductive load, electromagnetic fields are generated. These fields store energy in themselves, then release energy. The energy comes back and then comes back and so endlessly.
That is, if there is an inductive load, then it consumes this reactive power. In fact, she creates it by her presence. The reactive power from the source "runs along the wires". And while she is running, she spends active energy on her "running". That is, while it runs along the wires, it heats them up and energy is lost there.
That is, it seems like this reactive power seems useless. But if you look at the story with the girls at the beginning of the article, you cannot say that the girl who comes to the country to show off is useless.
It creates beauty: beauty, aesthetics - just as it creates reactive power electromagnetic fields, it is also needed and must be reckoned with.
But somehow smart people came up with how not to drive this power from the power plant to the consumer and it just needs to be generated next to the consumer so that it does not "ran" along a long path back and forth, and was generated right somewhere next to this machine, next to this engine, with this transformer, and so Further.
The easiest way is to put in a capacitor. The capacitor is the source of reactive power. And the coil is a consumer. If you put them next to it, then the capacitor will generate, and give to the coil. There is an exchange between them as in a circuit and we then unload this huge section of the network from the power plant to our distant transformer or engine. we simply unload it from unnecessary running of reactive power along this section. These actions are called reactive power compensation.
If the active and reactive power are added together P + Q, then we get the total power S (see the power triangle in the figure below).