How are the wire size and power among themselves

Anyone whose work is related to the electrical service, simply must know how to perform the calculation section of the power cable.Without it, you can be faced with an unpleasant situation when recently stretched to the consumer line goes down because of damage to the thermal conductor.To avoid this, you should not just always remember that wire size and power are interrelated, and if necessary, perform calculations.The ability to select the right diameter of conductors, depending on the power consumption can be useful in everyday life: for example, to choose their own cable-mounted electric boiler.

Wire, power and permissible current

Since most electrical formulas are quite complex, many people hardly heard of the need to perform any calculations, decide that without the help of energy specialists in this field to understand not work.In fact, cross-section of wires and power associated with a couple of simple formulas.The problem is reduced to the determination of the maximum current and further selection conductor using publicly available reference data.


From school physics course known that the current passing through the conductive material causes it to heat, which depends on the cross-sectional area of ​​the conductor and configuration (it is obvious that a thin conductive wires heats the hair higher thanmetal plate).Current rms value also influences, ie it increases the heating process become more intense.Let us recall the formula for calculating the known current and voltage resistance.It is derived from the classical Ohm's law and looks like I = U / R, where U - voltage in volts, R - resistance in ohms.

However, both associated with the wire size and power?Immediately!More correctly, in this case do not use the concept of power, and power (their communication, we show below, bringing a formula).

Electric power consumers linked to the magnitude of the current flowing through the conductor.In general, it can be determined from the formula P = I * U, where I - current in amperes.We do not consider the characteristics of power (active or reactive component), but these data is sufficient for the selection of wire section.It remains the last stage - to determine the cross-sectional area of ​​the cable core.Experienced electricians determine this parameter "by eye", but we recommend that you use a simple formula, thus avoiding possible mistakes.


With cable conductor insulation must be removed, exposing the metal, and to measure the diameter.Next, the obtained value to be substituted into the formula S = (3,14 * (d * d)) / 4, where d - diameter in millimeters.

remains to take reference (PUE), find a current and a correlation table section and select the right cable.Also considered material and method of laying line.

life example

Suppose that you need to connect boiler 2 kW to 220 V. Using the above formula for the «P», we obtain a current, it will be 9 amps.The store is the cheapest two-core cable with copper conductors with a cross section represented 0.75 and 1 mm.kv.Open the directory, find the "open wiring".Two-wire cross-section 1 mm.kv.It can withstand 16 amps (GOST-80!), and 0.75 corresponds to 15 A. Almost two-time reserve.Thus, in this example, the use of cables with copper conductors indicated quite acceptable.This is how tied wire size and power.