Proper selection of electrical cable is important in order to provide an adequate level of safety, cost-effective use of the cable and fully exploit the full potential of the cable. A properly dimensioned cross-section must be able to operate continuously under full load without damage, withstand short circuits in the network, provide a load with an appropriate voltage (without excessive voltage drop) and ensure the operation of protective devices during a lack of grounding. That is why a scrupulous and accurate calculation of the cable cross-section by power is made, which today can be done using our online calculator quite quickly.
Calculations are made individually according to the formula for calculating the cable section separately for each power cable for which a certain section must be selected, or for a group of cables with similar characteristics. All cable sizing methods to some extent follow the main 6 points:
To apply the online calculator for calculating the cable section, it is necessary to collect the information necessary to perform the sizing calculation. As a rule, you need to obtain the following data:
Copper cable section table
Aluminum cable section table
When determining most of the calculation parameters, the cable cross-section calculation table presented on our website is useful. Since the main parameters are calculated based on the needs of the current consumer, all initial ones can be calculated quite easily. However, the brand of cable and wire, as well as an understanding of the cable design, also plays an important role.
The main characteristics of the cable design are:
The current flowing through the cable creates heat due to losses in the conductors, losses in the dielectric due to thermal insulation and resistive losses from the current. That is why the most basic is the load calculation, which takes into account all the features of the power cable supply, including thermal ones. The parts that make up the cable (eg conductors, insulation, sheath, armour, etc.) must be able to withstand the temperature rise and heat radiating from the cable.
Cable carrying capacity is the maximum current that can continuously flow through a cable without damaging the cable insulation and other components. It is this parameter that is the result when calculating the load, to determine the total cross section.
Cables with larger conductor cross-sectional areas have lower resistance losses and can dissipate heat better than thinner cables. Therefore, a 16 mm2 cable will have a higher current carrying capacity than a 4 mm2 cable.
However, this difference in cross-section is a huge difference in cost, especially when it comes to copper wiring. That is why it is necessary to make a very accurate calculation of the wire cross-section in terms of power so that its supply is economically feasible.
For AC systems, the method of calculating voltage drops based on the power factor of the load is usually used. Typically the full load currents are used, but if the load was high at start (e.g. a motor), then the voltage drop based on the starting current (power and power factor if applicable) must also be calculated and taken into account, since low voltage It is also the reason for the failure of expensive equipment, despite the modern levels of its protection.
Use other online calculators.
| Enter power, kW: | |
| Select voltage: | 220 V 380 V 660 V 6 kV 10 kV |
| Specify the number of phases: | 1 3 |
| Select core material: | Aluminum (Al) Copper (Cu) |
| Cable line length, m: | |
| Specify line type: | Undefined up to 1 kB 6 kB 10 kB |
The online calculator considers the wire cross section for current and power, as well as for length. Counts both aluminum wiring and power copper conductors. Makes the selection of the section (core diameter) depending on the load. Doesn't count for 12v. To calculate, fill in all the fields and select the required parameters in all drop-down lists. Important! Please note that the calculations of this program for the selection of cables are not a direct guide to the use of electrical conductors, with the cross-sectional area calculated here. They are only a preliminary guide to the choice of section. The final accurate calculation for the selection of the section should be made by a qualified specialist who will make the right choice in each case. Remember, with correct calculations, you will get the result for the minimum cross-section of power cables. It is allowed to exceed this result for the calculated electrical wiring.
Allows you to select the cross section for maximum current and maximum load.
for copper wires:
for aluminum wires:
Allows you to choose the cross section for power consumption and voltage.
For single-phase electrical networks (220 V):
I = (P × K and) / (U × cos(φ))
For 380 in three-phase networks:
I = P / (√3 × U × cos(φ))
The table below shows the currents of the machine according to the connection method, depending on the voltage.
Cross section of an electric cable.
Cross section of electrical cable- this is one of the fundamental components of proper electrical wiring in the apartment. This means comfortable operation of electrical appliances and equipment, as well as the safety of consumers, i.e. all of us. The purpose of this article is to explain how to calculate cable cross section for the residential electrical network, based on the power of the electrical appliances used. And also tell what wire is needed for a particular section of home electrical wiring.
Before starting a conversation on the main topic of the article, let me remind you of some terms.
● Core- this, in the general sense, is a separate conductor (copper or aluminum), which can be either a solid conductor or consist of several individual wires twisted together in a bundle or dressed in a common braid.
● Wire- this is a product that consists of one single-wire or multi-wire core, dressed in a light protective sheath.
● Installation wire- this is a wire that is used for electrical wiring intended for lighting or power networks. It can be one -, two - or three-wire.
- this is a wire having a core cross section of up to 1.5 mm2. Cords are used to power light mobile (portable) electrical appliances and equipment. It consists of a multi-wire core, due to which it has increased ductility.
● Electrical cable- this is a product consisting of several insulated wires, on top of which there is from one to several protective sheaths.
Now, having decided on the names, let's move on to the main topic.
Since round-section wires and cables are mainly used for household electrical wiring, they will also be discussed.
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Content:
Before connecting the load to the network, it is important to make sure that the cores of the supply cable are of sufficient thickness. In the case of a significant excess of the permissible power, the destruction of the insulation and even the core itself is possible due to its overheating.
Before calculating the cable cross-section by power, you should calculate the sum of the powers of the connected electrical appliances. In most modern apartments, the main consumers are:
In sum, most modern apartments consume approximately 10 kW. Depending on the time of day, this parameter can be significantly reduced. However, when choosing a conductor cross section, it is important to focus on a large value.
You need to know the following: the calculation of the cable cross-section for single-phase and three-phase networks is different. But in both cases, three parameters should be taken into account first of all:
There are also several other variables, their meaning differs for each specific case.
The calculation of the wire cross-section by power is carried out using the following formula:
I = (P × K and) / (U × cos(φ))
Where,
If you need to quickly calculate the current, you can omit the value of cos (φ) and even K and. The resulting value will differ downward (by 15%) if a formula of this type is applied:
I=P/U
Having found the current according to the calculation formula, you can safely proceed to the choice of the supply cable. More precisely, its cross-sectional area. There are special tables that provide data that allow you to compare the amount of current, power consumption and cable cross-section.
Data vary greatly for conductors made from different metals. To date, for residential electrical wiring is usually used only rigid copper cable, aluminum is practically not used. Although in many old houses all lines are laid using aluminum.
The cross section of the copper cable is selected according to the following parameters:
Calculation of the wire cross section in the apartment - Table
It often happens that as a result of calculations, a current is obtained that is between the two values \u200b\u200bpresented in the table. In this case, the nearest higher value should be used. If, as a result of calculations, the current value in a single-core wire is 25 (A), it is necessary to select a cross section of 2.5 mm 2 or more.
To calculate the cross section of the supply cable used in a three-phase network, you must use the following formula:
I = P / (√3 × U × cos(φ))
Where,
Cos φ in this formula is very important. Since it directly affects the strength of the current. For different equipment, it is different, most often this parameter can be found in the technical accompanying documentation, or it is indicated on the case.
The total power of consumers is very simple: all powers are added up, the resulting value is used for calculations.
A distinctive feature of the choice of cable cross-sectional area for use in a three-phase network is that a thinner core can withstand a greater load. The required section is selected according to the standard table.
The choice of cable cross-section for a three-phase network - Table
The calculation of the wire cross-section by power in a three-phase network is performed using a value such as √3 . This value is necessary to simplify the appearance of the formula.
U linear = √3 × U phase
Thus, if necessary, you can replace the product of the root and the phase voltage with a linear voltage. This value is 380 (V) (U linear = 380 V).
When choosing a cable section, both for a three-phase network and for a single-phase network, it is necessary to take into account permissible continuous current . This parameter indicates the amount of current (measured in amperes) that the conductor can withstand for an unlimited amount of time. It is determined according to special tables, they are available in the PUE. For aluminum and copper conductors, the data differ significantly.
Permissible current duration - Table
If the value specified in the table is exceeded, the conductor starts to heat up. The heating temperature is inversely proportional to the current strength.
The temperature in a certain area can increase not only due to an incorrectly selected section, but also due to poor contact.For example, in the place of twisting wires. Quite often this happens as a result of direct contact between aluminum and copper cables. The surface of the metals is oxidized, covered with an oxide film, which significantly worsens the contact. This is where the cable gets hot.
During the repair process, the old electrical wiring is usually always replaced. This is due to the fact that recently many useful household appliances have appeared that make life easier for housewives. Moreover, they consume a lot of energy, which the old wiring simply cannot withstand. Such electrical appliances include washing machines, electric ovens, electric kettles, microwave ovens, etc.
When laying electrical wires, you should know what section of the wire you need to lay in order to power one or another electrical appliance or a group of electrical appliances. As a rule, the choice is made both in terms of power consumption and in terms of the current that electrical appliances consume. In this case, it is necessary to take into account both the laying method and the length of the wire.
It is quite simple to select the section of the cable to be laid according to the load power. It can be a single load or a combination of loads.
Each household appliance, especially a new one, is accompanied by a document (passport), which indicates its main technical data. In addition, the same data is available on special plates attached to the body of the product. This plate, which is located on the side or back of the device, indicates the country of manufacture, its serial number and, of course, its power consumption in watts (W) and the current that the device consumes in amperes (A). On products of a domestic manufacturer, power may be indicated in watts (W) or kilowatts (kW). The letter W is present on imported models. In addition, the power consumption is indicated as "TOT" or "TOT MAX".
An example of such a plate, which contains basic information about the device. Such a plate can be found on any technical device. If it is not possible to find out the necessary information (the inscription is erased on the plate or there are no household appliances yet), you can find out approximately what power the most common household appliances have. All this data can really be found in the table. Basically, electrical appliances are standardized in terms of power consumption and there is not much data scatter.
In the table, exactly those electrical appliances that are planned to be purchased are selected, and their current consumption and power are recorded. From the list, it is better to choose indicators that have maximum values. In this case, it will not be possible to miscalculate and the wiring will be more reliable. The fact is that the thicker the cable, the better, since the wiring heats up much less.
When choosing a wire, you should sum up all the loads that will be connected to this wire. At the same time, it should be checked that all indicators are written out either in watts or kilowatts. To convert the indicators to one value, you should either divide the numbers or multiply by 1000. For example, to convert to watts, you should multiply all the numbers (if they are in kilowatts) by 1000: 1.5 kW \u003d 1.5x1000 \u003d 1500 W. With the reverse translation, the actions are performed in the reverse order: 1500 W \u003d 1500/1000 \u003d 1.5 kW. Usually, all calculations are made in watts. After such calculations, the cable is selected using the appropriate table.
You can use the table as follows: find the corresponding column, which indicates the supply voltage (220 or 380 volts). This column contains a figure that corresponds to the power consumption (you need to take a slightly larger value). In the line that corresponds to the power consumption, the first column indicates the wire section that can be used. Going to the store for a cable, you should look for a wire whose cross section matches the records.
In this case, it all depends on the power consumption. In addition, the copper wire can withstand a load twice that of aluminum. If the loads are large, then it is better to give preference to copper wire, as it will be thinner and easier to lay. In addition, it is easier to connect it to electrical equipment, including sockets and switches. Unfortunately, copper wire has a significant disadvantage: it costs much more than aluminum wire. Despite this, it will last much longer.
Most craftsmen calculate wire diameters by current consumption. Sometimes this simplifies the task, especially if you know what current a wire with a particular thickness can withstand. To do this, it is necessary to write out all the indicators of the consumed current and sum them up. The wire cross section can be selected from the same table, only now you need to look for the column where the current is indicated. As a rule, a larger value is always chosen for reliability.
For example, to connect a hob that can consume a maximum current of up to 16A, a copper wire must be selected. Referring to the table for help, the desired result can be found in the third column from the left. Since there is no value 16A, we choose the nearest, larger - 19A. Under this current, the value of the cable cross section, equal to 2.0 mm square, is suitable.
As a rule, when connecting powerful household appliances, they are powered by separate wires, with the installation of separate automatic switches. This greatly simplifies the process of selecting wires. In addition, this is part of the modern requirements for electrical wiring. Plus, it's practical. In an emergency, you do not have to turn off the electricity completely, throughout the home. It is not recommended to select wires with a smaller value. If the cable constantly works at maximum loads, this can lead to emergency situations in the electrical network. The result can be a fire if the circuit breakers are not properly selected. At the same time, you should know that they do not protect the wire shell from ignition, and it will not be possible to select exactly the current so that it can protect the wires from overload. The fact is that they are not regulated and are produced for a fixed current value. For example, at 6A, at 10A, at 16A, etc.
The choice of a wire with a margin will allow in the future to install another electrical appliance on this line or even several, if this corresponds to the current consumption rate.
If we take into account the average apartment, then the length of the wires does not reach such values to take this factor into account. Despite this, there are times when when choosing a wire, their length should also be taken into account. For example, it is required to connect a private house from the nearest pole, which may be at a considerable distance from the house.
With significant current consumption, a long wire can affect the quality of power transmission. This is due to losses in the wire itself. The longer the wire length, the greater the losses in the wire itself. In other words, the longer the wire length, the greater the voltage drop in this section. In relation to our time, when the quality of power supply leaves much to be desired, this factor plays a significant role.
To know this, you will again have to refer to the table where you can determine the cross section of the wire, depending on the distance to the power point.
Table for determining the thickness of the wire, depending on the power and distance.
The current passing through the conductor causes it to heat up, since it has a certain resistance. So, the greater the current, the more heat is released on it, under conditions of the same cross section. With the same current consumption, more heat is generated on conductors of smaller diameter than on conductors of greater thickness.
Depending on the laying conditions, the amount of heat generated on the conductor also changes. In an open laying, when the wire is actively cooled by air, it is possible to give preference to a thinner wire, and when the wire is laid closed and its cooling is minimized, it is better to choose thicker wires.
Similar information can also be found in the table. The principle of choice is the same, but taking into account one more factor.
And finally, the most important thing. The fact is that in our time, the manufacturer is trying to save on everything, including the material for the wires. Very often, the declared cross section does not correspond to reality. If the seller does not notify the buyer, then it is better to measure the thickness of the wire on the spot if this is critical. To do this, just take a caliper with you and measure the thickness of the wire in millimeters, and then calculate its cross section using the simple formula 2 * Pi * D or Pi * R squared. Where Pi is a constant number equal to 3.14 and D is the diameter of the wire. In another formula, respectively, Pi \u003d 3.14, and R squared is the radius squared. It is very easy to calculate the radius, just divide the diameter by 2.
Some sellers directly point out the discrepancy between the declared section and the actual one. If the wire is selected with a large margin, then this is not at all significant. The main problem is that the price of the wire, in comparison with its cross section, is not underestimated.
