How to calculate the cross-section of the cable by the load, every self-respecting man must know. And this knowledge is needed for practical, everyday purposes. It should be understood that during the Soviet period, the calculation of the load on the electrical wiring of residential buildings was made, implying an average family that would live in an apartment. However, at that time there was not such a variety( and so many) of various household appliances, which now exist in almost every house.
The growth of individual construction also brings a growing number of people to such issues. After all, any new building involves laying cables and isolating the power wires. Now on the Internet on some sites there are even special calculators for determining the cross-section. It seems to be, why do you know the calculation?
The answer is simple - no one will deny that everything should be done meaningfully. For example, what if you do not have a cable with wires of the cross section that "counted" the computer? In the store - it means spending time and money, especially if there is some stock, as it should be for a good owner. Knowing how, on the basis of which calculations are made, clearly understanding their essence, one can always find a replacement for the missing material, take into account the perspective. And if you make a gasket "about", of which there is, then it is likely that the wires are shorted( and ignited), or the banal line break that still has to be looked for.
Calculation principle
All wires are calculated "by current".It is understood how much current( in amperes) the current can withstand this wire for any time, naturally, without damage. If there is a connection at home, then everything is done according to the project. And if you need to "supply" a separate room, for example, an extension? In this case, you need to think about what will be consumers in this room. It is considered all: bulbs in chandeliers, sconces and other lighting devices, televisions, refrigerators.
All the data on the power consumed by each device can be found in its passport. On many instruments, such data is also available on special plates( plates), which are screwed( glued), as a rule, from the back side. In this way, all available power in the room is counted. Something like in the all-inclusive mode.
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Section calculation
It is necessary to take into account that the cross-sections of wires are calculated according to those tables that correspond to the type of supplied voltage. For the vast majority of residential buildings this single-phase voltage. Therefore, the table should be looked at for it, and not for 3-phase. There the values will be different. So, in order to know the cross section, we need to determine which current should be oriented. Although the tables give data either on the strength of the current, or on the total power. There are also pivot tables. But the formula for a single-phase 220 V circuit is useful to remember.
P = J x U x COS / KH
- P - total power of all "consumers" of electricity / energy;
- J - the required current for calculation by the table;
- U is the mains voltage. It is equal to 220 V;
- Сos - for household appliances it is assumed to be "1";
- Ki is the coefficient assumed to be 0.75.
As a result of substitution of known values (as in school) we get:
P = J х 220 х 1 / 0,75 or J = 0,75 Р / 220
After learning the magnitude of the current strength, according to the table we find the cross section of one core. However, one must take into account that it is always necessary to make a reserve of "strength", just in case. Therefore, the found value of the current strength must be increased by another third, and then by the table to search for the required section. If there is no such wire at hand, then a wire with a larger cross-section can be used. But the smaller one does not.
Wire type
When choosing a wire, the preference should be given to the copper. It is stronger than aluminum, less oxidized, more resistant to bending. With the same current strength, the cross-section of the copper wire is smaller. This means that the wiring will also be more "compact".
