The table shows the power, current and sections of cables and wires, For calculations and selection of cable and wire, cable materials and electrical equipment.

In the calculation, the data of the PUE tables, active power formulas for single-phase and three-phase symmetrical loads were used.

Below are tables for cables and wires with copper and aluminum conductors.

Table for selecting the cable cross-section for current and power with copper conductors

	Copper conductors of wires and cables
	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	33,0
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	66,0	260	171,6

Table for selecting the cable cross-section for current and power with aluminum conductors

Conductor cross section, mm 2	Aluminum conductors of wires and cables
	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	132,0

Example of cable section calculation

Task: to power the heating element with a power of W = 4.75 kW with a copper wire in the cable channel.
Current calculation: I = W/U. We know the voltage: 220 volts. According to the formula, the current flowing I = 4750/220 = 21.6 amperes.

We focus on the copper wire, therefore we take the value of the diameter of the copper core from the table. In the column 220V - copper conductors, we find a current value exceeding 21.6 amperes, this is a line with a value of 27 amperes. From the same line we take the cross section of the conductive core, equal to 2.5 squares.

Calculation of the required cable cross-section by brand of cable, wire

№	Number of lived section mm. Cables (wires)	Outer diameter mm.							Pipe diameter mm.		Permissible long current (A) for wires and cables when laying:		Permissible continuous current for copper bars rectangular section (A) PUE
		VVG	VVGng	KVVG	KVVGE	NYM	PV1	PV3	PVC (HDPE)	Met.tr. Doo	in the air	in the ground	Cross-section, tires mm	Number of busbars per phase
1	1x0.75							2,7	16	20	15	15		1	2	3
2	1x1							2,8	16	20	17	17	15x3	210
3	1x1.5	5,4	5,4				3	3,2	16	20	23	33	20x3	275
4	1x2.5	5,4	5,7				3,5	3,6	16	20	30	44	25x3	340
5	1x4	6	6				4	4	16	20	41	55	30x4	475
6	1x6	6,5	6,5				5	5,5	16	20	50	70	40x4	625
7	1x10	7,8	7,8				5,5	6,2	20	20	80	105	40x5	700
8	1x16	9,9	9,9				7	8,2	20	20	100	135	50x5	860
9	1x25	11,5	11,5				9	10,5	32	32	140	175	50x6	955
10	1x35	12,6	12,6				10	11	32	32	170	210	60x6	1125	1740	2240
11	1x50	14,4	14,4				12,5	13,2	32	32	215	265	80x6	1480	2110	2720
12	1x70	16,4	16,4				14	14,8	40	40	270	320	100x6	1810	2470	3170
13	1x95	18,8	18,7				16	17	40	40	325	385	60x8	1320	2160	2790
14	1x120	20,4	20,4						50	50	385	445	80x8	1690	2620	3370
15	1x150	21,1	21,1						50	50	440	505	100x8	2080	3060	3930
16	1x185	24,7	24,7						50	50	510	570	120x8	2400	3400	4340
17	1x240	27,4	27,4						63	65	605		60x10	1475	2560	3300
18	3x1.5	9,6	9,2			9			20	20	19	27	80x10	1900	3100	3990
19	3x2.5	10,5	10,2			10,2			20	20	25	38	100x10	2310	3610	4650
20	3x4	11,2	11,2			11,9			25	25	35	49	120x10	2650	4100	5200
21	3x6	11,8	11,8			13			25	25	42	60	rectangular copper bars (A) Schneider Electric IP30
22	3x10	14,6	14,6						25	25	55	90
23	3x16	16,5	16,5						32	32	75	115
24	3x25	20,5	20,5						32	32	95	150
25	3x35	22,4	22,4						40	40	120	180	Cross-section, tires mm	Number of busbars per phase
26	4x1			8	9,5				16	20	14	14		1	2	3
27	4x1.5	9,8	9,8	9,2	10,1				20	20	19	27	50x5	650	1150
28	4x2.5	11,5	11,5	11,1	11,1				20	20	25	38	63x5	750	1350	1750
29	4x50	30	31,3						63	65	145	225	80x5	1000	1650	2150
30	4x70	31,6	36,4						80	80	180	275	100x5	1200	1900	2550
31	4x95	35,2	41,5						80	80	220	330	125x5	1350	2150	3200
32	4x120	38,8	45,6						100	100	260	385	Permissible continuous current for rectangular copper bars (A) Schneider Electric IP31
33	4x150	42,2	51,1						100	100	305	435
34	4x185	46,4	54,7						100	100	350	500
35	5x1			9,5	10,3				16	20	14	14
36	5x1.5	10	10	10	10,9	10,3			20	20	19	27	Cross-section, tires mm	Number of busbars per phase
37	5x2.5	11	11	11,1	11,5	12			20	20	25	38		1	2	3
38	5x4	12,8	12,8			14,9			25	25	35	49	50x5	600	1000
39	5x6	14,2	14,2			16,3			32	32	42	60	63x5	700	1150	1600
40	5x10	17,5	17,5			19,6			40	40	55	90	80x5	900	1450	1900
41	5x16	22	22			24,4			50	50	75	115	100x5	1050	1600	2200
42	5x25	26,8	26,8			29,4			63	65	95	150	125x5	1200	1950	2800
43	5x35	28,5	29,8						63	65	120	180
44	5x50	32,6	35						80	80	145	225
45	5x95	42,8							100	100	220	330
46	5x120	47,7							100	100	260	385
47	5x150	55,8							100	100	305	435
48	5x185	61,9							100	100	350	500
49	7x1			10	11				16	20	14	14
50	7x1.5			11,3	11,8				20	20	19	27
51	7x2.5			11,9	12,4				20	20	25	38
52	10x1			12,9	13,6				25	25	14	14
53	10x1.5			14,1	14,5				32	32	19	27
54	10x2.5			15,6	17,1				32	32	25	38
55	14x1			14,1	14,6				32	32	14	14
56	14x1.5			15,2	15,7				32	32	19	27
57	14x2.5			16,9	18,7				40	40	25	38
58	19x1			15,2	16,9				40	40	14	14
59	19x1.5			16,9	18,5				40	40	19	27
60	19x2.5			19,2	20,5				50	50	25	38
61	27x1			18	19,9				50	50	14	14
62	27x1.5			19,3	21,5				50	50	19	27
63	27x2.5			21,7	24,3				50	50	25	38
64	37x1			19,7	21,9				50	50	14	14
65	37x1.5			21,5	24,1				50	50	19	27
66	37x2.5			24,7	28,5				63	65	25	38

Instruction

To determine the cross section of a round, measure its diameter using a micrometer or caliper. If a micrometer is not at hand, the diameter of the wire can be approximately determined using a regular ruler. To use this method, strip the wire of insulation for a length of half a meter to one meter. Wind 10 turns of wire onto a ruler. The winding should be tight, coil to coil. Determine the length of the winding on the scale of the ruler and divide by ten. The resulting value is the required wire diameter. To improve the accuracy of diameter determination, increase the number of coils wound.

Square the diameter of the wire, expressed in . Multiply the resulting value by the number of PI, and then divide by four. The result of all actions will be the cross section of the wire, in square millimeters. The value of the number of PI to obtain a satisfactory accuracy is enough to take equal to 3.14. The number of mathematical operations can be reduced if the number of PIs is divided by four in advance. In this case, the squared diameter is multiplied by 0.785.

It is somewhat more difficult to calculate the cross section of a stranded wire. To find it, count the number of individual veins. Select one strand and measure its diameter. Calculate the cross section of this vein. Find the required cross-section of a stranded wire by multiplying the number of cores by the cross section of one core.

If a rectangular wire is used, determine its width and height using one of the above measuring tools. The resulting values ​​​​must have a dimension - millimeters. Multiply the length by the width. The result of multiplication is the cross section of the rectangular wire.

Related videos

note

Attention: the determination of the geometric characteristics of the wire is carried out in the absence of insulation on it. Failure to follow this rule may result in overloading the electrical circuit or incorrect parameters of its operation.

Helpful advice

When buying, the cross section of the wire can be found by marking. The first number following the letter designation of the wire type displays its cross section.

Sources:

• how to calculate wire diameter

Tip 2: How to Find the Cross-Sectional Area of ​​a Conductor

The maximum current that can be safely passed through a conductor depends on factors such as the material of the conductor, its cross-sectional area, type of insulation, temperature conditions, etc. The cross-sectional area is the main of these factors. To determine it, it is necessary to carry out measurements, and then calculations.

You will need

- voltmeter;

- caliper or micrometer;

- ruler;

- calculator.

Instruction

Completely de-energize the conductor in which you want to determine the cross-sectional area. Make sure that all capacitors are discharged in the device where it is located. If necessary, discharge them not with a short circuit, but with a load, and then check with a voltmeter that the capacitors are really discharged.

During all these actions, do not touch live parts, use insulated wires and probes. Measure the geometrical parameters of the conductor in the place where there is no insulation on the conductor. What exactly to measure depends on what cross-sectional shape the conductor has. If round, you need to know the diameter, if square - one of the sides, if rectangular - two perpendicular sides.

Do not apply voltage to the conductor until you remove the caliper or micrometer. The result of the measurement, if it is not in millimeters, convert to these units, and then the value of the cross-sectional area will be in square millimeters.

Content:

In electrical networks, there are many parameters that are determined in various ways. Among them there is a special table, the diameter and cross section of the wire with its help are determined with high accuracy. Such precise data is required when adding an electrical load, and the old wire does not have letter markings. However, even the conventions do not always correspond to reality. This is mainly due to the dishonesty of product manufacturers. Therefore, it is best to do your own calculations.

Application of measuring instruments

To determine the diameter of the cores of wires and cables, various measuring instruments are widely used, showing the most accurate results. Basically, for these purposes, the use of micrometers and calipers is practiced. Despite the high efficiency, a significant drawback of these devices is their high cost, which is of great importance if the tool is planned to be used only 1-2 times.

As a rule, professional electricians who are constantly engaged in work use special devices. With a competent approach, it becomes possible to measure the diameter of wire cores even on working lines. After obtaining the necessary data, it remains only to use a special formula: The result of the calculation will be the area of ​​the circle, which is the cross section of the core of the wire or cable.

Definition of a section with a ruler

An economical and accurate method is to determine the cross section of cables and wires using an ordinary ruler. In addition to it, you will need a simple pencil and the wire itself. To do this, the core of the wire is stripped of insulation, and then tightly wound onto a pencil. After that, using a ruler, the total length of the winding is measured.

The resulting measurement result must be divided by the number of turns. The result is the diameter of the wire, which will be needed for subsequent calculations. The cable cross section is determined by the previous formula. To obtain more accurate results, there should be as many wound turns as possible, but not less than 15. The turns are tightly pressed together, since the free space contributes to a significant increase in the error in the calculations. You can reduce the error by using a large number of measurements made in different versions.

A significant disadvantage of this method is the possibility of measuring only relatively thin conductors. This is due to the difficulties that arise when winding a thick cable. In addition, it is required to purchase a product sample in advance to perform preliminary measurements.

Table of ratios of diameters and sections

Determining the cross sections of cables and wires using formulas is considered a rather laborious and complex process that does not guarantee an accurate result. For these purposes, there is a special ready-made table, the diameter and cross section of the wire in which they clearly represent their ratio. For example, with a conductor diameter of 0.8 mm, its cross section will be 0.5 mm. A diameter of 1 mm corresponds to a cross section of 0.75 mm, and so on. It is enough just to measure the diameter of the wire, and then look into the table and calculate the desired cross section.

When performing calculations, certain recommendations must be followed. To determine the cross section, it is necessary to use a wire that is completely stripped of insulation. This is due to the possible reduced dimensions of the conductors and a higher insulating layer. In case of any doubt about the cable dimensions, it is recommended to purchase a conductor with a higher cross-section and power reserve. In the case of determining the cross-section of a multi-core cable, the diameters of individual wires are first calculated, the obtained values ​​​​are summarized and used in the formula or in the table.

The ability to choose the right cable cross-section over time can be useful to everyone, and for this it is not necessary to be a qualified electrician. By incorrectly calculating the cable, you can expose yourself and your property to a serious risk - too thin wires will get very hot, which can lead to a fire.

What is the calculation of the cable cross section for?

First of all, carrying out this slightly complicated procedure is necessary to ensure the safety of both the premises itself and the people in it. To date, mankind has not invented a more convenient method of distribution and delivery of electrical energy to the consumer, as by wire. People almost daily need the services of an electrician - someone needs to connect an outlet, someone needs to install a lamp, etc. It turns out that even such a seemingly insignificant procedure as installing a new lamp is connected with the selection of the required section. . What then to say about connecting an electric stove or water heater?

Failure to comply with regulations can lead to a violation of the integrity of the wiring, which often becomes the cause of a short circuit or even electric shock.

If you make a mistake when choosing a cable cross-section and purchase a cable with a smaller conductor area, this will lead to constant heating of the cable, which will cause the destruction of its insulation. Naturally, all this negatively affects the life of the wiring - it is not uncommon for a month after successful installation, the wiring stopped working, and specialist intervention was required.

It should be remembered that the electrical and fire safety in the building, and hence the life of the residents themselves, directly depends on the correctly selected cable cross-section value.

Of course, every owner wants to save as much as possible, but you should not do this at the cost of your life, putting it at risk - after all, as a result of a short circuit, a fire can occur, which may well destroy all property.

To avoid this, before starting electrical work, you should select a cable of the optimal section. There are several factors to consider when choosing:

• the total number of electrical devices in the room;
• the total power of all devices and the load they consume. To the obtained value should be added "in reserve" 20-30%;
• then, by means of simple mathematical calculations, convert the obtained value into the wire section, taking into account the material of the conductor.

Attention! Due to the lower electrical conductivity, wires with aluminum conductors must be purchased with a larger cross section than copper.

What affects the heating of wires

If the wiring heats up during the operation of household appliances, then all necessary measures should be taken immediately to eliminate this problem. There are many factors that affect the heating of wires, but the main ones include the following:

1. Insufficient cable area. In plain language, we can say this - the thicker the cores of the cable, the more current it can transmit without heating up. The value of this value is indicated in the marking of cable products. You can also measure the cross section yourself with a caliper (make sure that the wire is not energized) or by wire brand.
2. The material from which the wire is made. Copper conductors better transmit voltage to the consumer, and have less resistance than aluminum. Naturally, they heat up less.
3. Core type. The cable can be single-core (the core consists of one thick rod) or multi-core (the core consists of a large number of small wires). A multi-core cable is more flexible, but it is significantly inferior to a single-core cable in terms of the allowable strength of the transmitted current.
4. Cable laying method. Tightly laid wires located in the pipe at the same time heat up significantly more than open wiring.
5. Material and quality of insulation. Inexpensive wires tend to have poor quality insulation, which negatively affects their resistance to high temperatures.

How is the calculation of power consumption done

You can also calculate the approximate cross section of the cable yourself - it is not necessary to resort to the help of a qualified specialist. The data obtained as a result of the calculations can be used to purchase a wire, however, the electrical installation work itself should only be trusted by an experienced person.

The sequence of actions when calculating the section is as follows:

1. A detailed list of all electrical appliances in the room is compiled.
2. Passport data of the power consumption of all found devices are established, after which the continuity of operation of this or that equipment is determined.
3. Having identified the value of power consumption from devices that operate constantly, this value should be summed up, adding to it a coefficient equal to the value of periodically turning on electrical appliances (that is, if the device works only 30% of the time, then one third of its power should be added).
4. Next, we look for the obtained values ​​​​in a special table for calculating the wire section. For a greater guarantee, it is recommended to add 10-15% to the obtained value of power consumption.

To determine the necessary calculations for the selection of the cross section of electrical wiring cables according to their power within the network, it is important to use data on the amount of electrical energy consumed by devices and current devices.

At this stage, it is necessary to take into account a very important point - the data of power-consuming devices do not give an exact, but an approximate, averaged value. Therefore, to this mark, it is necessary to add about 5% of the parameters specified by the equipment manufacturer.

Most far from the most competent and qualified electricians are sure of one simple truth - in order to properly conduct electrical wires for lighting sources (for example, for lamps), it is necessary to take wires with a cross section of 0.5 mm², for chandeliers - 1, 5 mm², and for sockets - 2.5 mm².

Only incompetent electricians think about it and think so. But what if, for example, a microwave oven, a kettle, a refrigerator and lighting work in the same room at the same time, for which wires with different cross sections are needed? This can lead to a variety of situations: a short circuit, rapid damage to the wiring and insulating layer, as well as fire (this is a rare case, but still possible).

Exactly the same not the most pleasant situation can happen if a person connects a multicooker, a coffee maker and, say, a washing machine to the same outlet.

Features of calculating the power of hidden wiring

If the design documentation implies the use of hidden wiring, then it is necessary to purchase cable products "with a margin" - about 20–30% should be added to the obtained cable cross-section value. This is done to avoid heating the cable during operation. The fact is that in conditions of cramped space and lack of air access, the heating of the cable occurs much more intensively than when installing open wiring. If in closed channels it is planned to lay not one cable, but several at once, then the cross section of each wire should be increased by at least 40%. It is also not recommended to tightly lay various wires - ideally, each cable should be in a corrugated pipe, which provides additional protection.

Important! It is by the value of power consumption that professional electricians are guided when choosing a cable section, and only this method is correct.

How to calculate cable cross-sections by power

With a sufficient cable cross-section, the electric current will pass to the consumer without causing heating. Why does heating occur? We will try to explain as clearly as possible. For example, a kettle with a power consumption of 2 kilowatts is plugged into the outlet, but the wire going to the outlet can transmit only 1 kilowatt of current for it. The carrying capacity of the cable is related to the resistance of the conductor - the larger it is, the less current can be transmitted through the wire. As a result of the high resistance in the wiring, the cable heats up, gradually destroying the insulation.

With an appropriate cross section, the electric current reaches the consumer in full, and the wire does not heat up. Therefore, when designing electrical wiring, the power consumption of each electrical device should be taken into account. This value can be found in the technical data sheet for the electrical appliance or from the label affixed to it. Summing up the maximum values ​​and using a simple formula:

and get the value of the total current strength.

Pn denotes the power of the appliance indicated in the passport, 220 is the rated voltage.

For a three-phase system (380 V), the formula looks like this:

I=(P1+P2+....+Pn)/√3/380.

The resulting value of I is measured in Amperes, and on the basis of it, the appropriate cable section is selected.

It is known that the bandwidth of a copper cable is 10 A/mm, for an aluminum cable the bandwidth value is 8 A/mm.

For example, we calculate the size of the cable cross-section for connecting a washing machine, the power consumption of which is 2400 watts.

I \u003d 2400 W / 220 V \u003d 10.91 A, rounding up we get 11 A.

11 A+5 A=16 A.

If we take into account that three-core cables are used in apartments and look at the table, then 16 A is close to 19 A, therefore, to install a washing machine, you will need a wire with a cross section of at least 2 mm².

Table of cable section in relation to the magnitude of the current

Current- wire- wire (mm 2)		Current (A), for wires laid
	Open- That		in one pipe
		two one- vein	three one- vein	four one- vein	one two- vein	one three vein
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	-	-	-	-	-

How to choose conductor cross-sections

There are several more criteria that the cross section of the wires used must meet:

1. Length of cable. The longer the wire is, the greater the current loss is observed in it. This happens again as a result of an increase in resistance, which increases as the length of the conductor increases. This is especially felt when using aluminum wiring. When using copper wires to organize electrical wiring in an apartment, the length, as a rule, is not taken into account - a standard margin of 20–30% (with hidden wiring) is more than enough to compensate for possible increases in resistance associated with the length of the wire.
2. Type of wires used. In household power supply, 2 types of conductors are used - based on copper or aluminum. Copper wires are better and have less resistance, but aluminum wires are cheaper. When fully compliant, aluminum wiring does the job just as well as copper, so you need to carefully consider your choice before buying wire.
3. Electrical panel configuration. If all the wires supplying consumers are connected to one machine, then it will be the weak point in the system. A heavy load will lead to heating of the terminal blocks, and non-compliance with the rating will lead to its constant operation. It is recommended to divide the wiring into several "beams" with the installation of a separate machine.

In order to determine the exact data for selecting the section of electrical wiring cables, it is necessary to take into account any, even the most insignificant parameters, such as:

1. Type and type of electrical wiring insulation;
2. Plot length;
3. Ways and options for laying;
4. Features of the temperature regime;
5. The level and percentage of humidity;
6. The maximum possible value of overheating;
7. The difference in power of all current receivers belonging to the same group. All these and many other indicators can significantly increase the efficiency and benefits of using energy at any scale. In addition, correct calculations will help to avoid cases of overheating or rapid abrasion of the insulating layer.

In order to correctly determine the optimal cable section for any human domestic needs, it is necessary in all general cases to use the following standardized rules:

• for all sockets that will be installed in the apartment, it is necessary to use wires with an appropriate cross section of 3.5 mm²;
• for all spot lighting elements, it is necessary to use an electrical wiring cable with a cross section of 1.5 mm²;
• as for high-power devices, cables with a cross section of 4-6 mm² should be used for them.

If some doubts arise during the installation or calculations, it is better not to act blindly. The ideal option would be to refer to the appropriate table of calculations and standards.

Copper cable section table

Conductive cross section (mm)	Copper conductors of wires and cables
	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	80	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	265	57,2	220	145,2
120	300	66	260	171,6

Aluminum cable section table

Let's start the general course of calculations by first carrying out calculations using the formula:

P = (P1+P2+..PN)*K*J,

• P- the power of all consumers connected to the calculated branch in watts.
• P1, P2, PN- power of the first consumer, second, n-th, respectively, in watts.

Having received the result at the end of the calculations according to the above formula, it was the turn to turn to the tabular data.

Now we have to choose the required section according to Table 1.

Stage #1 - calculation of reactive and active power

The capacities of consumers are indicated in the documents for the equipment. Usually, equipment datasheets indicate active power along with reactive power.

Devices with an active type of load convert all the received electrical energy, taking into account the efficiency, into useful work: mechanical, thermal, or any other form of it.

Active load devices include incandescent lamps, heaters, electric stoves.

For such devices, the calculation of power by current and voltage has the form:

P=U*I,

• P- power in W;
• U- voltage in V;
• I is the current strength in A.

Devices with a reactive type of load are able to accumulate energy coming from a source, and then return it. Such an exchange occurs due to the displacement of the sinusoid of the current strength and the sinusoid of the voltage.

Current section calculation

Calculations of the required cross-section for current and power of cables and wires will provide more accurate results. Such calculations make it possible to evaluate the overall influence of various factors on conductors, including thermal load, wire grade, gasket type, operating conditions, etc.

The entire calculation is carried out during the following steps:

• choice of power of all consumers;
• calculation of currents passing through the conductor;
• selection of a suitable cross-section according to the tables.

For this calculation option, the power of consumers in terms of current with voltage is taken without taking into account correction factors. They will be taken into account when summing the current strength.

Stage # 1 - calculation of the current strength using the formulas

For those who have forgotten the school physics course, we offer the basic formulas in the form of a graphic diagram as a visual cheat sheet:

Voltage drop calculation

Any conductor, except superconductors, has resistance. Therefore, with a sufficient length of cable or wire, a voltage drop occurs.

PES standards require that the cross section of the cable core be such that the voltage drop is not more than 5%.

First of all, this concerns low-voltage cables of small cross section.

The voltage drop calculation is as follows:

R = 2*(ρ * L) / S,

U pad = I * R,

U% \u003d (U pad / U lin) * 100,

• 2 - coefficient due to the fact that the current flows necessarily through two wires;
• R– conductor resistance, Ohm;
• ρ - specific resistance of the conductor, Ohm * mm 2 / m;
• S- conductor cross section, mm 2;
• U pad– drop voltage, V;
• U%- voltage drop with respect to U lin,%.

Using formulas, you can independently perform the necessary calculations.

Carry Calculation Example

Those who wish to connect a household welding machine to a branch of the mains should take into account the current sieve for which the cable used is designed. It is possible that the total power of the working devices may be higher. The best option is to connect consumers to separate branches

Step 1. We calculate the resistance of the copper wire using table 9:

R \u003d 2 * (0.0175 * 20) / 1.5 \u003d 0.47 Ohm

Step #2 The strength of the current flowing through the conductor:

I \u003d 7000 / 220 \u003d 31.8 A

Step #3 Voltage drop across the wire:

U pad \u003d 31.8 * 0.47 \u003d 14.95 V

Step #4 Calculate the percentage of voltage drop:

U% \u003d (14.95 / 220) * 100 \u003d 6.8%

Conclusion: to connect the welding machine, a conductor with a large cross section is required.

Conclusions and useful video on the topic

Calculation of the conductor section according to the formulas:

The above calculations are valid for copper and aluminum conductors for industrial use. For other types of conductors, the total heat transfer is preliminarily calculated.

Based on these data, the maximum current that can flow through the conductor without causing excessive heating is calculated.