The calculation of the cable cross-section of current , power , length

Today there is a wide range of cable products, with a cross section of 0.35 lived mm.kv.and higher.

If you choose the wrong cable cross-section for household wiring, the result can have two total:

1. Too thick lived "hit" on your budget, becauseits meter will cost more.
2. If the wrong diameter wire (less than necessary), veins begin to heat up and melt the insulation, which will soon lead to spontaneous ignition wiring and short-circuit.

As you know, both the result of disappointing, so before installing the wiring in the house and the apartment must correctly calculate the cable section depending on the power, current and line length.Now we have a detailed look at each of the methods.

calculation power electrical

Each cable has a nominal capacity ofhe is able to withstand during operation of electrical appliances.If the power of all the appliances in the house will be greater than the estimated figure of the conductor, the accident will soon not be avoided.

to independently calculate the power of electrical appliances in the house, you need a sheet of paper write down the characteristics of each device separately (plates, TV, lamps, vacuum cleaner, etc.).After this, all the values ​​are summed up and ready number is used to select the optimal diameter.

calculation formula is:

Ptot = (P1 + P2 + P3 + ... + Pn) * 0.8,

Where: P1..Pn-power of each appliance kW

draw your attention to the fact that the resultingthe number must be multiplied by a correction factor of - 0,8.This ratio indicates that all of the appliances simultaneously be only 80%.This calculation is more logical, because, for example, a vacuum cleaner or hair dryer you sure you will not use for a long time without a break.

Selection Tables section of power cable:

For conductor with aluminum conductors
For conductor with copper conductors

As you can see, for each specific type of cable tabulated values ​​have their own data.All you need to do is find the nearest power value and see the corresponding cross section.

to you clearly understand how to calculate the cable for power, give a simple example:

We estimate that the total capacity of all the appliances in the apartment is 13 kW.This value must be multiplied by a factor of 0.8, which will result in the actual load of 10.4 KW.The table looking for a suitable value in the column.We are satisfied with the number "10.1" in the single-phase (220 V) and "10.5" if the three-phase network.Total, section selection stops at the 6-conductor milimmetrovom with single-phase or a 1.5-milimmetrovom when the three-phase network.As you can see, everything is quite simple and even an electrical novice to cope with the task on their own!

Calculation of current load calculation

current cable cross-section is more accurate, so it is best to use it.The essence is similar, but in this case it is necessary to determine the current load on the wiring.To begin, we consider the formulas amperage for each electric appliance.

average power household appliances
power Sample appliance (in this case, an LCD TV)

If the home is a single-phase network, for the calculation must use the following formula:

formula will be for a three-phase network haveview:

Where, P - the appliance power, kW

cos fi- power factor

Further, all currents are summed up and tabulated values ​​must be selected cross-section of the current cable.

draw your attention to the fact that the conductor pads conditions will depend on the values ​​of table values.When mounting open wiring load current and power will be significantly greater than when installing wiring in the pipe.

should be noted that the calculation of the resulting total value of the currents is recommended to multiply by half, to reserve.Suddenly, by the time you decide to buy more powerful electrical appliances?

selection table on the current cable cross-section:

calculation of the length

And the last way to calculate the cable cross-section - the length.The essence of these calculations is that each conductor has a resistance which increases with the length of the line current contributes losses (the greater the distance, the greater the loss).In the event that the magnitude of the losses will exceed 5%, it is necessary to choose larger conductor wires.

For calculations use the following procedure:

• necessary to calculate the total power and the power of electrical current (above, we have provided the corresponding formulas).
• perform calculations wiring resistance.The formula is as follows: the resistivity of the conductor (p) * length (in meters).The resulting amount is divided by the selected cable cross-section.

R = (p * L) / S, where p - the value of tabular

Please note that the length of the passage of the current must be multiplied twice becausecurrent is initially for one core, and then comes back on the other.

• Calculate the voltage loss: current strength is multiplied by the calculated resistance.
• determines the amount of loss: loss of voltage share on the mains voltage and multiplied by 100%.
• final number is analyzed.If the value is less than 5%, subject to the selected conductor cross-section.Otherwise, select a "thick" wire.

Table resistivity:

If you stretch the line for quite an extended distance, be sure to make calculations taking into account the losses in length, otherwise there is a high probability of a wrong choice of cable cross section.

Video examples of calculations

Illustrative examples of the video always allow better assimilate the information, so give it to your attention:

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