Let's see how the calculation of current by power is carried out

Before proceeding with the design of electricians in your home, you need to draw up a calculation scheme indicating all the expected loads in the premises and the length of individual cable sections. To draw up such a circuit, it will be necessary to calculate the current "by power". A properly drawn up map of the electrical system at home will allow you to select the cables of the required sections, which will protect your wiring from overheating and, accordingly, from the possibility of fire. Let's see, what is the calculation of the current "by power".

The correct selection of and also largely depends on the various values ​​of the parameters of electrical networks. The most important among them is considered And at the design stage, these quantities can be determined only by the calculation mathematical method. It is considered very important to calculate the current “by power” in three-phase networks, where the load must be placed evenly among the phases in order to prevent distortions. However, in urban household networks, these calculations must be carried out when designing not only switchboards, but also residential premises.

The calculation of the current "by power" is carried out under the condition of known values ​​​​of the power of electrical appliances, the nature of the loads and the mains voltage. For a single-phase supply network, the following formula is used: I = P / (U × cosφ), where:

• U - the value of the actual network voltage, measured in volts;
• cosφ is the corresponding power factor.

Depending on the nature of the load, the power factor is selected. So, for active loads (heating elements, incandescent lamps), it will be approximately equal to one. However, if we take into account that there is always a reactive component in the active load, then it is customary to use the cosφ value equal to 0.95 for calculations. When calculating the load, which is characterized by a large one (chokes of lighting devices, electric motors, induction furnaces, etc.), an average value of cosφ equal to 0.8 is taken.

For a three-phase supply network, the current power formula will be as follows: I \u003d P / (1.73 × U × cosφ).

For three-phase networks, the power factor values ​​for active and reactive loads are completely identical to single-phase networks.

Thus, using these formulas, it is necessary to calculate all the values ​​of the electric current from the load power that will be used in a particular area.

The next step in our calculations will be the choice of cable section. Although in the technical literature you can often find such a thing as “cable power calculation”, in fact, this is not a calculation, but still a “choice”. The calculation is understood as the formulas described above for determining the current load. In the presence of certain values ​​​​of current and voltage, it is selected from the reference tables. These tables are very clear and do not require a detailed description. You first select the wire material: copper or aluminum, and then determine the cable cross-section by the mains voltage and current value.

Here, in fact, we have considered how the electrical load is calculated and the cross section of cables for the electrification of objects is selected.