Advice 1: How to calculate wire size

To determine the cross section of the electric wire, use basic geometric formulas. Most commonly the calculation is made using the formula of area of a circle. Its application requires knowledge of such characteristics of the wire, such as diameter.
How to calculate wire size
You will need
  • micrometer, caliper or ruler, calculator.
Instruction
1
The method of calculating the cross section of electric wire depends on the construction of this wire. To calculate the cross sections used formulas area of a circle or rectangle. The calculation is performed in the following sequence. Clean the wire of insulation to a length of about 10 mm.
2
To determine the cross section of the conductor is round, measure its diameter using a micrometer or caliper. If the micrometer is not turned, the diameter of the wire can be approximated using a simple ruler. To use this method, clear the wire from the insulation to the length from half a meter to one meter. Wrap 10 turns of wire on the ruler. The winding should be dense, turn to turn. Determine the length of the winding on the ruler scale and divide by ten. The resulting value is the desired diameter of wire. To improve the precision of measurement of diameter, increase the number of winding turns.
3
The diameter of the wireexpressed in millimeters, erected in the square. The resulting value multiply by PI and then divide by four. The result of all actions will be section of the wirein square millimeters. The value of PI to obtain a satisfactory precision is enough to take = 3.14. The number of mathematical operations can be reduced, if the advance to make the division of PI by four. In this case, the diameter squared, multiplied by 0,785.
4
A bit more complicated calculated cross section stranded wire. To find it, count the number of individual wires. Select the vein and measure its diameter. Calculate the cross-section of this core. The required cross-section stranded wire find by multiplying the number of cores in the cross section of one core.
5
If you are using wire of rectangular cross section, determine its width and height using one of the above-mentioned measuring instruments. The obtained value should have a dimension – millimeters. Multiply length by width. The result of the multiplication is the value of the cross section of rectangular wire.
Note
Note: determination of the geometric characteristics of the wire produced in the absence of this exclusion. Ignoring this rule may result in the overloading of electrical circuits or incorrect parameters of its operation.
Useful advice
When you purchase the wire size you can find on the marking. The first number following the letter designation of the type of wire shows its cross section.

Advice 2: How to define section diameter

While wiring is sometimes needed to know the cross section of the used wire. You can find the table of diameters of wires and their respective sections, but the desired value it is possible to calculate independently.
How to define section diameter
You will need
  • - Vernier caliper or micrometer;
Instruction
1
To calculate the wire size, i.e. its area, enough basic knowledge from the school course of mathematics. As is known, the area of a circle is equal to the square of its radius multiplied by PI (3,14). For example, if the wire diameter is 1 mm, the radius will be respectively equal to 0.5 mm. to find the section, it is necessary 0,5 to square and multiply by 3.14. Total 0,5 × 0,5 × 3,14 = 0,785.
2
In practice, the important point is the correct measurement of wire diameter. For measurement, use a caliper or micrometer. The micrometer allows you to get a more accurate reading. The thinner the wire, the more error creeps into the calculations.
3
To determine the diameter of a thin wire, use the following method: tightly, turn to turn, wrap a pencil or other suitable mandrel about fifty turns of wire. Then measure the overall width of fifty turns, and divide the resulting value by 50. The more turns, the more accurate the result. This way you can determine the diameter, even very fine wires.
4
To avoid wasting time on calculations, you can use the table of the most common cross sections of connecting wires, it is given at the end of the article. When selecting wire for the wiring be sure to consider the maximum current that will consume electrical equipment.
5
To calculate the current in the network use the formula I = P/U where P is power, U – voltage. For example, if the total load may be 10 kW (10,000 watts), the wiring must be rated for the amperage: 10000/220 = 46 And (round the resulting number in a big way). Next on the table, select copper or aluminum wire, the cross section which can withstand the current.
6
Given that all electrical equipment in the apartment is never included simultaneously, the estimated load can be multiplied by a factor of 0.7. That is вместо10 use kW in calculations 10 × 0,7 = 7 kW. Then the wiring must be rated for the amperage 7000/220 = 32 A.
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