Cable cross-section for 1 kW of power. Online calculator for calculating cable cross-section by power. Relation between current and cross section

The correct choice of electrical cable to power electrical equipment is the key to long-term and stable operation of installations. Using the wrong wire has serious negative consequences.

The physics of the process of damage to an electrical line due to the use of an unsuitable wire is as follows: due to the lack of space in the cable core for the free movement of electrons, the current density increases; this leads to excess energy release and an increase in the temperature of the metal. When the temperature gets too high, the line's insulating sheath melts, which can cause a fire.

To avoid trouble, you must use a cable with cores of suitable thickness. One way to determine the cross-sectional area of a cable is to start from the diameter of its cores.

Calculator for calculating cross-section by diameter

To simplify calculations, a calculator has been developed for calculating cable cross-section by diameter. It is based on formulas that can be used to find the cross-sectional area of single-core and stranded wires.

You need to measure the cross-section by measuring the core without insulation, otherwise nothing will work.

When it comes to calculating tens and hundreds of values, an online calculator can significantly simplify the life of electricians and electrical network designers due to convenience and increased speed of calculations. It is enough to enter the value of the core diameter, and, if necessary, indicate the number of wires if the cable is multi-core, and the service will show the required wire cross-section.

Calculation formula

You can calculate the cross-sectional area of an electrical wire in different ways, depending on its type. For all cases, a single formula is used to calculate the cable cross-section by diameter. It looks like this:

D – core diameter.

The core diameter is usually indicated on the wire sheath or on a general label with other technical characteristics. If necessary, this value can be determined in two ways: using a caliper and manually.

The first way to measure the core diameter is very simple. To do this, it must be cleared of the insulating shell, and then use a caliper. The value that it will show is the diameter of the core.

If the wire is stranded, you need to unravel the bundle, count the wires and measure only one of them with a caliper. There is no point in determining the entire diameter of the beam - such a result will be incorrect due to the presence of voids. In this case, the formula for calculating the cross section will look like:

D – core diameter;

a is the number of wires in the core.

If a caliper is not available, the core diameter can be determined manually. To do this, a small section of it must be freed from the insulating shell and wound around a thin cylindrical object, for example, a pencil. The coils should fit snugly against each other. In this case, the formula for calculating the diameter of the wire core looks like this:

L – wire winding length;

N is the number of complete turns.

The longer the core is wound, the more accurate the result.

Selection by table

Knowing the diameter of the wire, you can determine its cross-section using a ready-made dependence table. The table for calculating the cable cross-section by core diameter looks like this:

Conductor diameter, mm	Conductor cross-section, mm2
0.8	0.5
1	0.75
1.1	1
1.2	1.2
1.4	1.5
1.6	2
1.8	2.5
2	3
2.3	4
2.5	5
2.8	6
3.2	8
3.6	10
4.5	16

When the cross-section is known, it is possible to determine the permissible power and current values for copper or aluminum wire. In this way, it will be possible to find out what load parameters the current-carrying core is designed for. To do this, you will need a table of the dependence of the cross section on the maximum current and power.

In the air (trays, boxes, voids, channels)						Section, sq. mm	In the ground
Copper conductors			Aluminum conductors				Copper conductors			Aluminum conductors
Current. A	power, kWt		Tone. A	power, kWt			Current, A	power, kWt		Current. A	Power, kWt
Current. A	220 (V)	380(V)	Tone. A	220(V)	380(V)		Current, A	220(V)	380(V)	Current. A	220(V)
19	4.1	17.5				1,5	77	5.9	17.7
35	5.5	16.4	19	4.1	17.5	7,5	38	8.3	75	79	6.3
35	7.7	73	77	5.9	17.7	4	49	10.7	33.S	38	8.4
*2	9.7	77.6	37	7	71	6	60	13.3	39.5	46	10.1
55	17.1	36.7	47	9.7	77.6	10	90	19.8	S9.7	70	15.4
75	16.5	49.3	60	13.7	39.5	16	115	753	75.7	90	19,8
95	70,9	67.5	75	16.5	49.3	75	150	33	98.7	115	75.3
170	76.4	78.9	90	19.8	59.7	35	180	39.6	118.5	140	30.8
145	31.9	95.4	110	74.7	77.4	50	775	493	148	175	38.5
ISO	39.6	118.4	140	30.8	97.1	70	775	60.5	181	710	46.7
770	48.4	144.8	170	37.4	111.9	95	310	77.6	717.7	755	56.1
760	57,7	171.1	700	44	131,6	170	385	84.7	753.4	795	6S
305	67.1	700.7	735	51.7	154.6	150	435	95.7	786.3	335	73.7
350	77	730.3	770	59.4	177.7	185	500	110	379	385	84.7

Converting watts to kilowatts

In order to correctly use the table of wire cross-section versus power, it is important to correctly convert watts to kilowatts.

1 kilowatt = 1000 watts. Accordingly, to obtain the value in kilowatts, the power in watts must be divided by 1000. For example, 4300 W = 4.3 kW.

Examples

Example 1. It is necessary to determine the permissible current and power values for a copper wire with a core diameter of 2.3 mm. Supply voltage – 220 V.

First of all, you should determine the cross-sectional area of the core. This can be done using a table or a formula. In the first case, the value is 4 mm 2, in the second - 4.15 mm 2.

The calculated value is always more accurate than the tabulated value.

Using a table of the dependence of cable cross-section on power and current, you can find out that for a cross-section of a copper core with an area of 4.15 mm 2, a power of 7.7 kW and a current of 35 A are permissible.

Example 2. It is necessary to calculate the current and power values for an aluminum stranded wire. Core diameter – 0.2 mm, number of wires – 36, voltage – 220 V.

In the case of a stranded wire, it is not advisable to use tabular values; it is better to use the formula for calculating the cross-sectional area:

Now you can determine the power and current values for a stranded aluminum wire with a cross section of 2.26 mm 2. Power – 4.1 kW, current – 19 A.

In the modern technological world, electricity has almost become on the same level of importance as water and air. It is used in almost any area of human activity. The concept of electricity appeared back in 1600; before that, we knew about electricity no more than the ancient Greeks. But over time, it began to spread more widely, and only in 1920 did it begin to displace kerosene lamps from street lighting. Since then, electric current began to spread rapidly, and now it is available even in the most remote village, at least illuminating the house and for telephone communications.

Electricity itself is a stream of directed charges moving along a conductor. A conductor is a substance capable of passing these electric charges through itself, but each conductor there is resistance(except for the so-called superconductors, the resistance of superconductors is zero, this state is achievable by lowering the temperature to -273.4 degrees Celsius).

But, of course, there are no superconductors in everyday life, and it is still a long time before they appear on an industrial scale. In everyday life, as a rule, current is passed through wires, and is mainly used as a conductor. copper or aluminum wires. Copper and aluminum are popular primarily due to their conductivity properties, which is the inverse of electrical resistance, and also because they are cheap compared to, for example, gold or silver.

How to understand the cross-sections of copper and aluminum cables for wiring?

This article is intended to teach you how to calculate the cross-section of a wire. It's like the more water you want to supply, the larger the diameter of the pipe you need. So here, the greater the electrical current consumption, the larger the cross-section of cables and wires should be. I will briefly describe what it is: if you bite through a cable or wire and look at it from the end, you will see its cross-section, that is, the thickness of the wire, which determines the power that this wire is capable of transmitting when heated to the permissible temperature.

In order to select the correct cross-section of the power wire, we it is necessary to take into account the maximum value of the current load consumed. The current values can be determined by knowing the rated power of the consumer, which is determined by the following formula: I=P/220, where P is the power of the current consumer, and 220 is the number of volts in your outlet. Accordingly, if the outlet is 110 or 380 volts, then we substitute this value.

It is important to know that the calculation of the value for single-phase and three-phase networks is different. In order to find out how many phases of the network you need, you need to calculate the total amount of current consumption in your home. Let's give an example of the average set of equipment that you may have at home.

A simple example of calculating cable cross-section based on current consumption, now we will calculate the sum of the powers of connected electrical appliances. The main consumers in an average apartment are the following devices:

TV - 160 W
Refrigerator - 300 W
Lighting - 500 W
Personal computer - 550 W
Vacuum cleaner - 600 W
Microwave oven - 700 W
Electric kettle - 1150 W
Iron - 1750 W
Boiler (water heater) - 1950 W
Washing machine - 2650 W
Total 10310 W = 10.3 kW.

Once we know the total electricity consumption, we can use the formula to calculate the cross-section of the wire for the normal functioning of the wiring. It's important to remember that for single-phase and three-phase networks the formulas will be different.

Calculation of wire cross-section for a network with one phase (single-phase)

The wire cross-section is calculated using the following formula:

I = (P × K u) / (U × cos(φ))

I- current strength;

P- power of all energy consumers in total
K and- simultaneity coefficient, as a rule, the generally accepted value for calculations is 0.75
U- phase voltage, which is 220V but can range from 210V to 240V.
cos(φ)- for household single-phase appliances this value is fixed and equals 1.

When we have found the current consumption according to the formula, we can start choosing a cable, which suits us in terms of power. Or rather, its cross-sectional area. Below is a special table that provides data that compares the current value, cable cross-section and power consumption.

Data may vary for wires made of different metals. Today, for residential applications, copper, rigid cable is typically used. Aluminum cable is practically not used. But still, in many older houses, aluminum cable is still present.

Table of estimated cable current capacity. The choice of copper cable cross-section is made according to the following parameters:

We also provide a table for calculating the current consumption of an aluminum cable:

If the power value turns out to be an average between two indicators, then you need to select a larger wire cross-section value. Since there must be a power reserve.

Calculation of the wire cross-section of a network with three phases (three-phase)

Now let’s look at the formula for calculating the wire cross-section for three-phase networks.

To calculate the cross-section of the supply cable, we use the following formula:

I = P / (√3 × U × cos(φ))

I- current strength by which the cross-sectional area of the cable is selected
U- phase voltage, 220V
Cosφ - phase angle
P- shows the total consumption of all electrical appliances

Cosφ- in the above formula is extremely important, since it personally affects the current strength. It varies for different equipment; this parameter can most often be found in the technical documentation, or the corresponding marking on the case.

The total power is found very simply, we sum up the value of all power indicators and use the resulting number in the calculations.

A distinctive feature in a three-phase network is that a thinner wire can withstand a larger load. We select the required wire cross-section according to the table below.

Calculation of wire cross-section by current consumption used in a three-phase network is used using such a value as √3 . This value is needed to simplify the appearance of the formula itself:

U linear = √3 × U phase

In this way, if the need arises, the product of the root and phase voltage is replaced by the linear voltage. This value is equal to 380V (U linear = 380V).

Concept of continuous current

Also, one equally important point when choosing a cable for a three-phase and single-phase network is that it is necessary to take into account a concept that sounds like permissible long-term current. This parameter shows us the current strength in the cable that the wire can withstand for an unlimited amount of time. You can define the ego in a special table. They also differ significantly for aluminum and copper conductors.

When this parameter exceeds the permissible values, the conductor begins to overheat. The heating temperature is inversely proportional to the current strength.

Temperatures may increase in some areas not only due to incorrectly selected wire cross-section, and also with poor contact. For example, in the place where wires are twisted. This quite often happens at the point of contact between copper cables and aluminum cables. In this regard, the surface of the metals undergoes oxidation, becoming covered with an oxide film, which greatly impairs the contact. In such a place the cable will heat up above the permissible temperature.

When we have carried out all the calculations and checked the data from the tables, you can safely go to a specialized store and buy the cables you need for laying a network at home or in the country. Your main advantage over, for example, your neighbor will be that you have fully understood this issue with the help of our article, and you will save a lot of money without overpaying for what the store wanted to sell you. Yes, and knowing how to calculate the current cross-section for copper or aluminum wires will never be superfluous, and we are sure that the knowledge gained from us will come in handy many times on your life’s journey.

When installing electrical wiring, it is necessary to determine the power of consumers in advance. This will help in the optimal selection of cables. This choice will allow you to operate the wiring for a long time and safely without repairs.

Cable and conductor products are very diverse in their properties and intended purpose, and also have a wide range in prices. The article talks about the most important wiring parameter - the cross-section of a wire or cable in terms of current and power, and how to determine the diameter - calculate it using a formula or select it using a table.

The current-carrying part of the cable is made of metal. The part of the plane passing at right angles to the wire, bounded by metal, is called wire cross-section. The unit of measurement is square millimeters.

Section determines permissible currents passing through wires and cables. This current, according to the Joule-Lenz law, leads to the release of heat (proportional to the resistance and the square of the current), which limits the current.

Conventionally, three temperature ranges can be distinguished:

the insulation remains intact;
the insulation burns, but the metal remains intact;
metal melts at high temperatures.

Of these, only the first is the permissible operating temperature. In addition, with a decrease in cross-section its electrical resistance increases, which leads to an increase in voltage drop in the wires.

However, an increase in cross-section leads to an increase in mass and especially cost or cable.

The materials used for the industrial production of cable products are pure copper or aluminum. These metals have different physical properties, in particular resistivity, and therefore the cross sections selected for a given current may be different.

Find out from this video how to choose the correct wire or cable cross-section according to power for home wiring:

Determination and calculation of cores using the formula

Now let’s figure out how to correctly calculate the cross-section of a wire based on power, knowing the formula. Here we will solve the problem of determining the section. It is the cross section that is the standard parameter due to the fact that the nomenclature includes both single-core and multi-core options. The advantage of multi-core cables is their greater flexibility and resistance to kinks during installation. As a rule, stranded wires are made of copper.

The easiest way to determine the cross-section of a round single-core wire is d– diameter, mm; S– area in square millimeters:

Stranded ones are calculated by a more general formula: n– number of veins, d– core diameter, S- square:

The diameter of the core can be determined by removing the insulation and measuring the diameter against the bare metal with a caliper or micrometer.

The current density is determined very simply, it is number of amperes per section. There are two wiring options: open and closed. The open one allows for a higher current density due to better heat transfer to the environment. Closed requires a downward adjustment so that the heat balance does not lead to overheating in the tray, cable duct or shaft, which can cause a short circuit or even a fire.

Accurate thermal calculations are very complex; in practice, they are based on the permissible operating temperature of the most critical element in the structure, according to which the current density is selected.

Thus, the permissible current density is the value at which heating of the insulation of all wires in a bundle (cable duct) remains safe, taking into account the maximum ambient temperature.

Table of current cross-section of copper and aluminum wire or cable:

Table 1 shows the permissible current density for temperatures not higher than room temperature. Most modern wires have PVC or polyethylene insulation, allowing heating during operation no more than 70-90°C. For “hot” rooms, the current density must be reduced by a factor of 0.9 for every 10°C to the operating temperatures of the wires or cables.

Now about what is considered open and what . is wiring if it is made with clamps (tires) along the walls, ceiling, along the supporting cable or through the air. The closed one is laid in cable trays, walled into walls under plaster, made in pipes, a shell or laid in the ground. You should also consider the wiring closed if it is in or. The closed one cools worse.

For example, let the thermometer in the dryer room show 50°C. To what value should the current density of a copper cable laid in this room along the ceiling be reduced if the cable insulation can withstand heating up to 90°C? The difference is 50-20 = 30 degrees, which means you need to use the coefficient three times. Answer:

Example of calculating the wiring section and load

Let the suspended ceiling be illuminated by six lamps with a power of 80 W each and they are already connected to each other. We need to supply power to them using aluminum cable. We will assume that the wiring is closed, the room is dry, and the temperature is room temperature. Now we’ll find out how to calculate the power of copper and aluminum cables; for this we use the equation that determines the power (according to the new standards, we consider the mains voltage to be equal to 230 V):

Using the corresponding current density for aluminum from Table 1, we find the cross section required for the line to operate without overheating:

If we need to find the diameter of the wire, we use the formula:

Suitable would be cable APPV2x1.5 (section 1.5 mm.kv). This is perhaps the thinnest cable you can find on the market (and one of the cheapest). In the above case, it provides a double power reserve, i.e. a consumer with a permissible load power of up to 500 W, for example, a fan, dryer or additional lamps, can be installed on this line.

It is unacceptable to install sockets on this line, since they may (and most likely will) contain a powerful consumer and this will lead to overloading the line section.

Quick Selection: Useful Standards and Ratios

To save time, calculations are usually tabulated, especially since the range of cable products is quite limited. The following table shows the calculation of the cross-section of copper and aluminum wires according to power consumption and current strength, depending on the purpose - for open and closed wiring. The diameter is obtained as a function of load power, metal and type of wiring. The mains voltage is considered to be 230 V.

The table allows you to quickly select a section or diameter, if the load power is known. The found value is rounded up to the nearest value from the nomenclature series.

The following table summarizes the data on permissible currents by cross-section and power of materials of cables and wires for calculation and quick selection of the most suitable ones:

The wiring arrangement, among other things, requires design skills, which not everyone who wants to do it has. It is not enough to just have good electrical installation skills. Some people confuse design with drawing up documentation according to some rules. These are completely different things. A good project can be written out on pieces of paper from a notebook.

First of all, draw a plan of your premises and mark future sockets and lamps. Find out the power of all your consumers: irons, lamps, heating devices, etc. Then enter the power of the loads most frequently consumed in different rooms. This will allow you to choose the best cable options.

You will be surprised how many possibilities there are and what is the reserve for saving money. Once you select , count the length of each line you draw. Put everything together, and then you will get exactly what you need, and as much as you need.

Each line must be protected by its own (), designed for a current corresponding to the permissible power of the line (the sum of the consumer powers). Sign the machines, located in, for example: “kitchen”, “living room”, etc.

It is advisable to have a separate line for all lighting, then you can easily repair the socket in the evening without using matches. It is the sockets that are most often overloaded. Provide outlets with enough power - you don't know in advance what you'll have to plug into them.

In damp rooms, use only double-insulated cables! Use modern sockets (“Euro”) and with grounding conductors and connect the grounding correctly. Bend single-core wires, especially copper ones, smoothly, leaving a radius of several centimeters. This will prevent them from breaking. Wires must lie straight in cable trays and ducts, but freely, in no case should you pull them like a string.

There should be a margin of a few extra centimeters. When laying, you need to make sure that there are no sharp corners anywhere that could cut the insulation. The terminals must be tightened tightly when connecting., and for stranded wires this procedure should be repeated; they have a tendency for the cores to shrink, as a result of which the connection may become loose.

Copper wires and aluminum wires are not “friendly” with each other for electrochemical reasons; they cannot be connected directly. To do this, you can use special terminal blocks or galvanized washers. The joints must always be dry.
Phase conductors must be white (or brown), and neutrals must always be blue. Grounding is yellow-green in color. These are generally accepted color rules and commercial cables, as a rule, have internal insulation in exactly these colors. Compliance with colors increases the safety of operation and repair.

We bring to your attention an interesting and educational video on how to correctly calculate the cable cross-section by power and length:

The choice of wire cross-section is the main element of a power supply project of any scale, from a room to large networks. The current that can be taken into the load and power will depend on this. The correct choice of wires also ensures electrical and fire safety, and provides an economical budget for your project.

When repairing and designing electrical equipment, it becomes necessary to choose correctly. You can use a special calculator or reference book. But for this you need to know the load parameters and cable laying features.

Why do you need to calculate the cable cross-section?

The following requirements apply to electrical networks:

safety;
reliability;
efficiency.

If the selected cross-sectional area of the wire is small, then the current loads will not be large, which will lead to overheating. As a result, an emergency may occur that will damage all electrical equipment and become dangerous to the life and health of people.

If you install wires with a large cross-sectional area, then safe use is ensured. But from a financial point of view there will be cost overruns. The correct choice of wire cross-section is the key to long-term safe operation and rational use of financial resources.

The cable cross-section is calculated based on power and current. Let's look at examples. To determine what wire gauge is needed for 5 kW, you will need to use PUE tables (“ Rules for electrical installations“). This directory is a regulatory document. It states that the choice of cable cross-section is made according to 4 criteria:

Supply voltage ( single-phase or three-phase).
Conductor material.
Load current measured in amperes ( A), or power - in ( kW).
Cable location.

There is no meaning in the PUE 5 kW, so you have to choose the next larger value -- 5.5 kW. For installation in an apartment today it is necessary. In most cases, installation is by air, so a cross-section of 2.5 mm² is suitable from the reference tables. In this case, the maximum permissible current load will be 25 A.

The above reference book also regulates the current for which the input circuit breaker is designed ( VA). According to " Rules for electrical installations“, with a load of 5.5 kW, the VA current should be 25 A. The document states that the rated current of the wire that is suitable for a house or apartment should be an order of magnitude greater than that of VA. In this case, after 25 A there is 35 A. The last value must be taken as the calculated value. A current of 35 A corresponds to a cross section of 4 mm² and a power of 7.7 kW. So, the choice of the cross-section of the copper wire according to power is completed: 4 mm².

To find out what wire gauge is needed for 10 kW, let's use the reference book again. If we consider the case for open wiring, then we need to decide on the cable material and the supply voltage.

For example, for an aluminum wire and a voltage of 220 V, the nearest higher power will be 13 kW, the corresponding cross-section will be 10 mm²; for 380 V the power will be 12 kW and the cross-section will be 4 mm².

Choose by power

Before choosing a cable cross-section based on power, you need to calculate its total value and make a list of electrical appliances located in the territory to which the cable is laid. The power must be indicated on each of the devices; the corresponding units of measurement will be written next to it: W or kW ( 1 kW = 1000 W). Then you will need to add up the power of all equipment and get the total.

If you select a cable to connect one device, then only information about its energy consumption is sufficient. You can select wire cross-sections based on power in the PUE tables.

Table 1. Selection of wire cross-section based on power for cables with copper conductors

	For cable with copper conductors
	Voltage 220 V		Voltage 380 V
	Current, A	power, kWt	Current, A	power, kWt
1,5	19	4,1	16	10,5
2,5	27	5,9	25	16,5
4	38	8,3	30	19,8
6	46	10,1	40	26,4
10	70	15,4	50	33
16	85	18,7	75	49,5
25	115	25,3	90	59,4
35	135	29,7	115	75.9
50	175	38.5	145	95,7
70	215	47,3	180	118,8
95	260	57,2	220	145,2
120	300	66	260	171,6

Table 2. Selection of wire cross-section based on power for cables with aluminum conductors

Conductor cross-section, mm²	For cable with aluminum conductors
	Voltage 220 V		Voltage 380 V
	Current, A	power, kWt	Current, A	power, kWt
2,5	20	4,4	19	12,5
4	28	6,1	23	15,1
6	36	7,9	30	19,8
10	50	11,0	39	25,7
16	60	13,2	55	36,3
25	85	18,7	70	46,2
35	100	22,0	85	56,1
50	135	29,7	110	72,6
70	165	36,3	140	92,4
95	200	44,0	170	112,2
120	230	50,6	200	132,2

In addition, you need to know the network voltage: three-phase corresponds to 380 V, and single-phase corresponds to 220 V.

The PUE provides information for both aluminum and copper wires. Both have their advantages and disadvantages. Advantages of copper wires:

high strength;
elasticity;
oxidation resistance;
electrical conductivity is greater than that of aluminum.

Lack of copper conductors-- high price. In Soviet houses, aluminum electrical wiring was used during construction. Therefore, if a partial replacement occurs, it is advisable to install aluminum wires. The only exceptions are those cases when, instead of all the old wiring ( to the distribution board) a new one is installed. Then it makes sense to use copper. It is unacceptable for copper and aluminum to come into direct contact, as this leads to oxidation. Therefore, a third metal is used to connect them.

You can independently calculate the wire cross-section according to power for a three-phase circuit. To do this you need to use the formula: I=P/(U*1.73), Where P-- Power, W; U-- voltage, V; I-- current, A. Then the cable cross-section is selected from the reference table depending on the calculated current. If the required value is not there, then the closest one is selected, which exceeds the calculated one.

How to calculate by current

The amount of current passing through a conductor depends on the length, width, resistivity of the latter and on temperature. When heated, the electric current decreases. Reference information is given for room temperature ( 18°C). To select the cable cross-section for current, use the PUE tables.

Table 3. Electric current for copper wires and cords with rubber and PVC insulation

Conductor cross-sectional area, mm²
	open	in one pipe
	open	two single-core	three single-core	four single-core	one two-wire	one three-wire
0,5	11	-	-	-	-	-
0,75	15	-	-	-	-	-
1	17	16	15	14	15	14
1,2	20	18	16	15	16	14,5
1,5	23	19	17	16	18	15
2	26	24	22	20	23	19
2,5	30	27	25	25	25	21
3	34	32	28	26	28	24
4	41	38	35	30	32	27
5	46	42	39	34	37	31
6	50	46	42	40	40	34
8	62	54	51	46	48	43
10	80	70	60	50	55	50
16	100	85	80	75	80	70
25	140	115	100	90	100	85
35	170	135	125	115	125	100
50	215	185	170	150	160	135
70	270	225	210	185	195	175
95	330	275	255	225	245	215
120	385	315	290	260	295	250
150	440	360	330	-	-	-
185	510	-	-	-	-	-
240	605	-	-	-	-	-
300	695	-	-	-	-	-
400	830	-	-	-	-	-

A table is used to calculate aluminum wires.

Table 4. Electric current for aluminum wires and cords with rubber and PVC insulation

Conductor cross-sectional area, mm²	Current, A, for wires laid
	open	in one pipe
	open	two single-core	three single-core	four single-core	one two-wire	one three-wire
2	21	19	18	15	17	14
2,5	24	20	19	19	19	16
3	27	24	22	21	22	18
4	32	28	28	23	25	21
5	36	32	30	27	28	24
6	39	36	32	30	31	26
8	46	43	40	37	38	32
10	60	50	47	39	42	38
16	75	60	60	55	60	55
25	105	85	80	70	75	65
35	130	100	95	85	95	75
50	165	140	130	120	125	105
70	210	175	165	140	150	135
95	255	215	200	175	190	165
120	295	245	220	200	230	190
150	340	275	255	-	-	-
185	390	-	-	-	-	-
240	465	-	-	-	-	-
300	535	-	-	-	-	-
400	645	-	-	-	-	-

In addition to the electric current, you will need to select the conductor material and voltage.

For an approximate calculation of the cable cross-section for current, it must be divided by 10. If the resulting cross-section is not in the table, then it is necessary to take the nearest larger value. This rule is only suitable for cases where the maximum permissible current for copper wires does not exceed 40 A. For the range from 40 to 80 A, the current must be divided by 8. If aluminum cables are installed, then it must be divided by 6. This is explained by the fact that for to ensure equal loads, the thickness of the aluminum conductor is greater than that of copper. Each conductor is characterized by electrical resistance. This parameter is affected by:

Wire length, unit of measurement - m. As it increases, losses increase.
Cross-sectional area, measured in mm². As it increases, the voltage drop decreases.
Material resistivity (reference value). Shows the resistance of a wire measuring 1 square millimeter per 1 meter.

The voltage drop is numerically equal to the product of resistance and current. It is acceptable that the specified value does not exceed 5%. Otherwise, you need to take a cable with a larger cross-section. Algorithm for calculating wire cross-section based on maximum power and length:

Depending on power P, voltage U and coefficient cosф we find the current using the formula: I=P/(U*cosф). For electrical networks used in everyday life, cosф = 1. In industry, cosph is calculated as the ratio of active power to total power. The latter consists of active and reactive powers.
Using PUE tables, the current cross-section of the wire is determined.
We calculate the conductor resistance using the formula: Ro=ρ*l/S, where ρ is the resistivity of the material, l is the length of the conductor, S is the cross-sectional area. It is necessary to take into account the fact that current flows through the cable not only in one direction, but also back. Therefore the total resistance is: R = Ro*2.
We find the voltage drop from the relationship: ΔU=I*R.
Determine the voltage drop as a percentage: ΔU/U. If the obtained value exceeds 5%, then select the nearest larger cross-section of the conductor from the reference book.

Open and closed wiring

Depending on the placement, wiring is divided into 2 types:

closed;
open.

Today, hidden wiring is installed in apartments. Special recesses are created in the walls and ceilings to accommodate cables. After installing the conductors, the recesses are plastered. Copper wires are used. Everything is planned in advance, because over time, to build up electrical wiring or replace elements, you will have to dismantle the finishing. For hidden finishing, wires and cables that have a flat shape are often used.

When laid open, the wires are installed along the surface of the room. Advantages are given to flexible conductors that have a round shape. They are easy to install in cable channels and pass through the corrugation. When calculating the load on the cable, the method of laying the wiring is taken into account.

Cable power table required to correctly calculate the cable cross-section, if the power of the equipment is large and the cable cross-section is small, then it will heat up, which will lead to the destruction of the insulation and loss of its properties.

To calculate the conductor resistance, you can use the conductor resistance calculator.

For the transmission and distribution of electric current, the main means are cables; they ensure the normal operation of everything related to electric current, and how good this work will be depends on the right choice cable cross-section by power. A convenient table will help you make the necessary selection:

Current cross-section conductive lived mm
	Voltage 220V		Voltage 380V
	Current. A	Power. kW	Current. A	Power, kWt

Section Toko- conductive lived mm	Aluminum conductors wires and cables
	Voltage 220V		Voltage 380V
	Current. A	Power. kW	Current. A	Power, kWt

But in order to use the table, you need to calculate the total power consumption of devices and equipment that are used in a house, apartment or other place where the cable will be laid.

Example of power calculation.

Let's say you are installing closed electrical wiring in a house using an explosive cable. You need to write down a list of equipment used on a piece of paper.

But how now find out power? You can find it on the equipment itself, where there is usually a label with the main characteristics recorded.

Power is measured in Watts (W, W) or Kilowatts (kW, KW). Now you need to write down the data and then add it up.

The resulting number is, for example, 20,000 W, which would be 20 kW. This figure shows how much energy all electrical receivers together consume. Next, you should consider how many devices will be used simultaneously over a long period of time. Let’s say it turns out to be 80%, in which case the simultaneity coefficient will be equal to 0.8. We calculate the cable cross-section based on power:

20 x 0.8 = 16 (kW)

To select a cross-section, you will need a cable power table:

Current cross-section conductive lived mm	Copper conductors of wires and cables
	Voltage 220V		Voltage 380V
	Current. A	Power. kW	Current. A	Power, kWt




10		15.4

If the three-phase circuit is 380 Volts, then the table will look like this:

Current cross-section conductive lived mm	Copper conductors of wires and cables
	Voltage 220V		Voltage 380V
	Current. A	Power. kW	Current. A	Power, kWt

				16.5


10		15.4

These calculations are not particularly difficult, but it is recommended to choose a wire or cable with the largest cross-section of conductors, because it may be that it will be necessary to connect some other device.

Additional cable power table.