Reactive power is a very common word for electricians, but once they ask them what reactive power is, few people can say it. If you look for information or read books online, it will involve relatively complex calculations, which is even more like reading a heavenly book for electricians with weak foundations.
Today, I will explain the reactive power to you on the basis of not involving formula calculations, aiming to let everyone understand the meaning of reactive power, at least when others ask you what reactive power is, you won’t be unable to answer it.
Before talking about reactive power, we must first know two points: reactive power is only applicable to AC circuit , and there is no such term for reactive power in DC circuits; reactive power is only related to inductance or capacitor , and has nothing to do with resistor .
In fact, has three important powers in the AC circuit. Among them, has inductance and capacitors, reactive power , and resistance are called active power , , and combination of active power and reactive power is apparent power . The reactive power of the inductor of
is called inductive reactive power of , and the reactive power of the capacitor is called capacitance reactive power of . The two are very similar, so we only need to understand one of them. Next, I will explain reactive power to you from the inductor.
As we all know, transformers, motors and other devices have coil , and a magnetic field will be generated when the current flows through the coil. Ignoring the resistance value of the coil, it is inductance component in the circuit.
In an AC circuit, the voltage and current are alternating, and their magnitude and direction change periodically. This alternating current flows through the inductor, which will produce an alternating magnetic field. The magnetic field has energy. For example, two magnets can generate force to each other and attract or repel it because the magnetic field stimulated by the magnet has energy and does work on the other magnet.
The stronger the magnetic field, the greater the energy it has. Therefore, in an AC circuit, if the alternating current becomes larger, the magnetic field becomes stronger, and at this time the inductor will absorb electric energy; if the current becomes smaller, the magnetic field will weaken, and the inductor will release electric energy. In other words, as the alternating current increases and decreases, the inductor is constantly absorbing and releasing energy (i.e., exchanging energy) .
Compared with the energy dissipation characteristics of the resistor, the inductor (resistance is zero) does not consume energy, and it only exchanges energy with the power supply. However, during the exchange process, the inductor absorbs energy, which means that the power supply must first have part of the energy to absorb the inductor, even if the inductor returns this energy to the power supply.
For the sake of easy understanding, before talking about reactive power, let’s first understand the active power. active power is actually the average power . As mentioned earlier, active power is only related to resistance, and resistance is an energy-consuming component, so active power refers to the speed of the resistor consumes electricity, and the focus is on the word "consumption". In actual AC circuits, anything that involves electricity consumption means that there must be resistance and active power in the circuit.
For example, the actual inductance coil , the resistance cannot be zero, so it has more or less a certain active power, but in circuit analysis , the coil often ignores the resistance (active is zero), and only looks at the part of its electrical and magnetic exchange.
Since active power is the embodiment of energy consumption, it is obvious that reactive power is the embodiment of energy consumption . In addition, whether it is active power or reactive power, they are all a kind of "power". The so-called power refers to the speed of energy change. For example, active power represents the speed of the resistor's consumption of electrical energy.So, learn from one example and apply it to other things, does reactive power refer to the speed of the exchange energy of the inductor (or capacitor)? That's right!
In order to distinguish the active consumption of resistors, we refer to the fastest process of inductors or capacitors that do not consume electricity, , which only exchanges energy, as the reactive power (that is, the maximum value of instantaneous power). Do you understand?
After knowing the meaning of reactive power, we can try to explain the reactive power of the capacitor. The reactive power of an inductor is manifested as the exchange of electrical energy and magnetic field energy, while the capacitor is the exchange of electrical energy and electric field energy. Simply put, in an AC circuit, as the voltage changes, the electric field between the two plates of the capacitor will also change. If the voltage becomes larger, the electric field will increase and the capacitor will absorb energy; if the voltage becomes smaller and the electric field will weaken, the capacitor will release energy. Like the inductor, the capacitor will also continuously absorb and release energy. The fastest absorption and release is the reactive power of the capacitor!
Article source: Original by Jicheng Training Network, author: Yang Sihui; reproduction is prohibited without authorization, violators will be prosecuted!
