Amps to watts: formula and table for converting current to power and vice versa

Power in an electrical circuit represents the energy consumed by a load from a source per unit time, indicating the rate at which it is consumed. Unit of measurement Watt

[W or W].
The current strength displays the amount of energy passed over a period of time, that is, it indicates the speed of passage. It is measured in amperes
[A or Am]. And the voltage of electric current flow (potential difference between two points) is measured in volts. Current strength is directly proportional to voltage.

To independently calculate the Ampere / Watt or W / A ratio, you need to use the well-known Ohm's law. Power is numerically equal to the product of the current flowing through the load and the voltage applied to it. Determined by one of three equalities: P = I * U = R * I² = U²/R.

Therefore, to determine the power of the energy source when the current in the network is known, you need to use the formula: W (watts) = A (amps) x I (volts). And to make the reverse conversion, you need to convert the power in watts to the current consumption in amperes: Watt / Volt. When we are dealing with a 3-phase network, we will also have to take into account the coefficient of 1.73 for the current strength in each phase.

Is there a difference between Volts and Watts?

First, let's remember what these concepts mean.
Let’s also try to find out if there is a significant difference between them. So, an electrical voltage that produces a current whose strength is equal to 1 Ampere is called a Volt. In this case, it stands in a conductor with a resistance of 1 ohm.

Volts can be divided:

• 1,000,000 microvolts
• 1,000 millivolts

At the same time, we can say that Watt is the constant power of electric current. At a voltage of 1 Volt, its power is 1 Ampere.

Based on the above, we can safely say that there is still a difference between these concepts. Therefore, it must be taken into account when working with various electrical systems.

How many volts does 1 ampere contain?

It is quite difficult to answer this question. However, to make it easier for you to understand this issue, we suggest that you familiarize yourself with the tables of ratios:

For DC:

For AC:

What are Volt Amperes and how to convert them to Watts?

Another unit of measurement of power adopted in SI is Volt-ampere (VA). It is equal to the product of effective values ​​such as current and voltage.

Additionally, it is worth noting that, as a rule, VAs are used solely to estimate the power in AC connections. That is, in cases where Watt and Volt-Ampere have different meanings.

There are now many different online calculators that allow you to quickly and easily convert VA to Watts. This procedure is so simple that we will not dwell on it.

But, especially for those people who do not have an online calculator at hand to convert Volt-amps to Watts, we will look at the process of converting these quantities in more detail:

1. Energy is produced or consumed at a certain rate. And Watt is one of the units of power.
2. To measure the magnitude of the electric current, A is used, which is equal to 1 Coulomb.
3. Electromotive force or voltage is measured in Volts.
4. In order to remember how these quantities relate to each other, you need to learn the following formula: Amps = Watts/Volts

Using this formula we can find out the current strength. Of course, only if we already know the voltage and power.

That is, it turns out that to convert Watts to Amperes, we must find out the voltage in the system. For example, in the USA the voltage in the electrical network is 120V, and in Russia it is 220V.

It is worth noting that batteries used in cars usually have a voltage of 12 V. And the voltage in small batteries used for various portable devices, as a rule, does not exceed 1.5 V.

Thus, we can say that knowing the voltage and power, we can easily find out the current strength as well. To do this, we only need to correctly use the above formula.

Let's look at how this “works” with a specific example: if the voltage is 220V and the power is 220W, then the current will be 220/220 or 1 A.

What is power? Watt [W]

Watt , according to the SI system, is a unit of measurement of power. Nowadays it is used to measure the power of all electrical and other devices. According to the theory of physics, power is the rate of energy consumption, expressed in the ratio of energy to time: 1 W = 1 J/1 s. One watt is equal to the ratio of one joule (a unit of work) to one second.

Today, the unit of measurement kilowatt (abbreviated designation kW) is more often used to indicate the power of electrical appliances. It’s easy to guess how many watts are in a kilowatt - the prefix “kilo” in the SI system denotes the value obtained by multiplying by a thousand.

For calculations involving power, it is not always convenient to use the watt itself. Sometimes, when the quantities being measured are very large or very small, it is much more convenient to use a unit of measurement with standard prefixes, which avoids constant calculations of the order of the value. Thus, when designing and calculating radars and radio receivers, pW or nW are most often used; for medical devices such as EEG and ECG, μW is used. In the production of electricity, as well as in the design of railway locomotives, megawatts (MW) and gigawatts (GW) are used.

How many watts are in 1 ampere?

Now let's try to convert Watts to Amps. And for this we need one more formula:

I=P/U

In it, I is A, P is Watt, and U is Volt.

By making a simple calculation using this formula, we can find out how many Watts are in one A.

As we said earlier, there is another way to calculate how many watts are in 1 A. In order to use it, you will need to open an online calculator and enter the power consumption and voltage into it.

Next, you just need to click on the button labeled “calculate” and within a couple of seconds a special program will give you the correct value. By using this method, you will undoubtedly be able to save your time and effort, since you do not have to independently calculate all the indicators using formulas.

What quantities are measured in Amperes and Watts?

The main quantities needed to convert amps to watts are current, whose unit is 1A (ampere), and voltage, whose unit is 1V (volt).

Important! Power for calculations is measured in watts (W), otherwise the result will be underestimated by 1000 times.

It is impossible to directly convert these quantities into each other using certain coefficients. Finding out how many watts are in 1 ampere is possible only in individual cases, for which these coefficients have already been calculated and allow for an approximate recalculation.

For more accurate calculations, all three parameters are needed, and in some cases additional data, such as the number of phases, cos(φ) and efficiency.

Formula for direct current

To determine power at constant voltage, the following expression is used - P=U•I, where:

• P (W) – power of the electrical appliance;
• U (B) – network voltage;
• I (A) – current consumption.

Using the rules of mathematics known from elementary school, you can perform a conversion to determine voltage and current. These formulas have the following form, allowing you to calculate one unknown parameter with the other two known:

• current – ​​I=P/U;
• power – Р=U•I;
• voltage – U=P/I.

In this form they are used primarily in DC networks. At home, this voltage is used in car wiring, as well as when connecting LED strips and modules.

For single-phase and three-phase networks, a more complex formula is needed. It is necessary to take into account additional parameters.

Formula for single-phase network

In electrical engineering there is such a concept as active and reactive load. The reactive load is characterized by the consumption of reactive power and is expressed by the coefficient cos(φ) (cosine “phi”). Taking into account the cos(φ) coefficient, the formula by which you can convert Amps to Watts will look like:

In apartment sockets the voltage is not constant, but alternating. In such networks, in addition to active power, there is reactive power. It appears when there is an inductive or capacitive load. The sum of these powers is called total. The parameter that determines the active load component is called cosφ (cosine phi).

In order to find out how many watts are in an ampere, the calculation must be made using the following formulas - P=U*I*cosφ, and the current, accordingly, I=P/(U*cosφ). In everyday life, cosine phi is usually not taken into account.

It is also not used when calculating devices that consume only active power - electric heating, electric furnace with heating elements, water heater, electric kettle, electric stoves, incandescent lamps and other similar devices.

To understand how to convert Amps to Watts using the formula, you can consider an example:

• 11.36 Amps = 2500W/220V
• 6.81 Amps = 1500W/220V
• 4.54 Amps = 1000W/220V
• 2.27 Amps = 500W/220V
• 1.81 Ampere = 400W/220V
• 1 Ampere = 220W/220V
• 0.45 Ampere = 100W/220V
• 0.27 Ampere = 60W/220V

If we take a 12-volt car battery as an example, a load of 1 ampere will correspond to a power of 12 watts. For a household network with a voltage of 220 Volts, a current of 12 Amps corresponds to 2640 Watts or 2.64 kW.

How to use an online calculator

Knowing the current parameters, you can independently calculate such an important parameter as power. This value determines the rate of energy consumption per unit of time, so you can calculate additional costs and load on the network when the device is turned on.

What information will you need to enter:

• Mains voltage , which may also vary. Car wiring is usually designed for 12 V voltage. On older models there is still an indicator of 6 V , and on large vehicles - 24 V (buses or trucks with diesel engines).
• Rated current , the value of which can usually be found from the technical data sheet of the equipment. Typically, such information is placed directly on the device body.

The intuitive interface of the calculator will allow you to quickly convert amperes to kilowatts and perform other similar operations. The service will allow you to quickly convert the power consumption of electrical appliances in order to calculate the load on the network. In addition, such a calculator will provide car owners with complete information about the consumed power of the electrical network. This will allow you to easily select a new battery and replace individual electrical wiring components.

Formula for three-phase network

Some private houses equipped with electric heating and electric stoves are supplied with a three-phase 380V line. There are two situations that require calculation in this network:

All loads are single-phase, divided into separate groups. The calculation is performed for each phase separately, similar to a single-phase network.

In addition to single-phase appliances and heaters, there are three-phase electric motors. For these devices, power is converted into current using special formulas:

and the current, respectively:

Table on how to convert Amperes to Watts for calculating circuit breakers:

Calculation of power in a DC network

The easiest way to convert amps to watts is for DC devices. In these devices it is used in its simplest form. In everyday life, such a calculation is most often made when repairing automotive electrical wiring and connecting LED strips.

These strips are connected to the power supply and to select it you need to know the current consumption of the LED devices. If the choice of unit is made incorrectly, it will be overloaded and burn out, or vice versa, the power of the device will be excessive. Such a block is more expensive and has larger dimensions.

On the housing of power supplies designed specifically for LED strips, the output voltage, current and power are indicated, but on some devices the power is not indicated.

In this case, it can be calculated using the formula P=U*I. For a device with an output voltage of 12V and a current of 1.4 A, P=12V*1.4A=16.8 W. Taking into account the 20% power reserve, such a power supply is enough to connect 1 meter of LED5050 strip.

You can do it differently and determine the current consumption of the LEDs. When installing a strip with a power of 14.4 W/m indicated on the tag, the current consumption of 1 meter will be I=P/U=14.4W/12V=1.2A. With a tape length L of 3 meters, the total current I=1.2 A*3m=3.6 A.

An example of converting Amperes to Watts in a single-phase network

Calculation for a single-phase network is most often carried out for household electrical wiring. Cosφ in this case is taken equal to 1, but difficulties arise due to the non-simultaneous inclusion of all electrical appliances.

For example, all kitchen outlets are connected to a 25A circuit breaker. These sockets include a 2kW electric kettle, 1.2kW electric oven, 0.8kW microwave oven, 3.5kW dishwasher and 3.5kW washing machine. Which of these devices can be turned on at the same time?

First of all, you need to find out the total power of the devices that can be connected to the machine. For this, the formula P=U*I=220V*25A=5500V=5.5 kW is used. As can be seen from the calculation, it is allowed to simultaneously turn on a kettle, oven and microwave without a dishwasher and washing machine, or one of these devices and one of the devices of lower power.

Converting Amperes to Watts for a three-phase network

Let's say you have a private house and use a three-phase input to connect it. A three-pole 32 Ampere circuit breaker is installed in the water shield. How much power is this? In order to convert amperes into watts in this case and find out what maximum power can be connected in this case, we will use the above formula (assuming that cos(φ) = 1):

P=380*32*1.73=21036 W ≈ 21 kW

Another example, if there is a three-phase input in the house and a 25A input circuit breaker, the total power of simultaneously switched on electrical appliances will be:

P=380*25*1.73=16500W=16.5kW.

The actual load in a residential building consists of a large number of electrical appliances of different power and is unevenly distributed.

Another example of how you can find the current for a three-phase motor when connected with a star:

Formulas for converting amperes to watts and vice versa are necessary primarily at home, but their knowledge will not be superfluous for electricians working in industrial enterprises.

Cable cross-section

The cable cross-section is the cut area of ​​the current-carrying core. If the cut of the core is round (as in most cases) and consists of one wire, then the area/section is determined by the formula for the area of ​​a circle. If there are many wires in the core, then the cross-section will be the sum of the cross-sections of all the wires in this core.

The cross-sectional values ​​are standardized in all countries, and the standards of the former CIS and Europe in this part completely coincide. In our country, the document that regulates this issue is the “Rules for the Construction of Electrical Installations” or briefly - PUE.

The cable cross-section is selected based on the loads using special tables called “Permissible current loads on the cable.” If you have no desire to understand these tables, then it is enough for you to know that it is advisable to use a copper cable with a cross-section of 1.5-2.5 mm² for sockets, and 1.0-1.5 mm² for lighting.

To introduce one phase into an ordinary 2-3 room apartment, 6.0 mm² is quite enough. All the same, your 40-80 m² will not fit larger equipment, even taking into account the electric stove.

To “estimate” the required cross-section, many electricians believe that 1 mm² of copper wire can pass 10A of electric current through itself: accordingly, 2.5 mm² of copper can pass 25A, and 4.0 mm² - 40A, etc. If you analyze the cable cross-section selection table a little, you will see that this method is only suitable for estimation and only for cables with a cross-section no higher than 6.0 mm².

Below is an abbreviated table for selecting cable cross-sections up to 35 mm² depending on current loads. For your convenience, the total power of electrical equipment is given there for 1-phase (220V) and 3-phase (380V) consumption.

When laying the cable in a pipe (i.e. in any closed spaces), the possible current loads on the cable should be less than when laying it openly. This is due to the fact that the cable heats up during operation, and heat transfer in a wall or in the ground is much lower than in open space.

When the load is called in kW, we are talking about the total load. Those. for a single-phase consumer, the load will be indicated for one phase, and for a three-phase consumer - in total for all three. When the load value is named in amperes (A), we are always talking about the load on one core (or phase).

Load table for cable cross-section:

To independently calculate the required cable cross-section, for example, for entry into a house, you can use a cable calculator or select the required cross-section from the table.

This table applies to cables and wires with rubber and plastic insulation. These are such widespread brands as: PVS, GDP, VPP, PPV, APPV, VVG. AVVG and a number of others. Paper-insulated cables have their own table, and non-insulated wires and buses have their own.

When calculating the cable cross-section, the specialist must also take into account the methods of laying the cable: in trays, in bundles, etc. In addition, the values ​​​​from the tables on permissible current loads must be adjusted by the following reduction factors:

• correction factor corresponding to the cable cross-section and its location in the block;
• correction factor for ambient temperature;
• correction factor for cables laid in the ground;
• correction factor for different numbers of operating cables laid nearby.

Calculation of cable cross-section

Let's start not with a table, but with a calculation. That is, each person, without having the Internet at hand, where the PUE with tables is freely available, can independently determine the cable cross-section by current. To do this you will need a caliper and a formula.

If we consider the cross-section of the cable, it is a circle with a certain diameter. There is a formula for the area of ​​a circle: S = 3.14*D²/4, where 3.14 is the Archimedean number, “D” is the diameter of the measured core. The formula can be simplified: S=0.785*D².

If the wire consists of several cores, then the diameter of each is measured, the area is calculated, then all the indicators are summed up. How to calculate the cross-section of a cable if each core consists of several thin wires?

The process becomes a little more complicated, but not much. To do this, you will have to count the number of wires in one core, measure the diameter of one wire, calculate its area using the described formula and multiply this figure by the number of wires. This will be the cross section of one core. Now you need to multiply this value by the number of cores.

If you don’t want to count the wires and measure their sizes, you just need to measure the diameter of one core, consisting of several wires. You must take measurements carefully so as not to crush the core. Please note that this diameter is not exact because there is space between the wires.

Relation between current and cross section

To understand how an electrical cable works, you need to remember a regular water pipe. The larger its diameter, the more water will pass through it. It's the same with wires.

The larger their area, the greater the current that will pass through them, the greater the load such a wire can withstand. In this case, the cable will not overheat, which is the most important requirement of fire safety rules.

Therefore, the cross-section - current connection is the main criterion that is used in the selection of electrical wires in the wiring. Therefore, you need to first figure out how many household appliances and what total power will be connected to each loop.

For example, the kitchen must have a refrigerator, microwave, coffee grinder and coffee maker, an electric kettle and sometimes a dishwasher. That is, all these devices can be turned on simultaneously at the same time. Therefore, the total power of the room is used in the calculations.

You can find out the power consumption of each device from the product passport or on the tag.

For example, let's designate some of them:

1. Kettle – 1-2 kW.
2. Microwave and meat grinder 1.5-2.2 kW.
3. Coffee grinder and coffee maker – 0.5-1.5 kW.
4. Refrigerator 0.8 kW.

Having found out the power that will act on the wiring, you can select its cross-section from the table. We will not consider all the indicators in this table; we will show those that prevail in everyday life.

How to translate

The basic formula reflecting the dependence of electric current indicators on each other is as follows: P = U*I, where U denotes voltage in volts, I is current in amperes, and P is power in watts. Everyone knows the ratio from school physics, which sometimes people forget. Actually, knowing this ratio, you can carry out all further operations yourself, however, there are some subtleties that we will discuss below.

Power Expression

Theoretically, to obtain a particular value, you only need to transform the formula. For example, to find voltage: U=P/I. For example, in Russia, household electrical networks are energized at 220 V. With a power equal to, say, 220 W, the current will be 1 A (220/220). However, this calculation is only valid for a constant voltage network.

If we convert amperes to watts on an alternating voltage network, its actual, effective value should be used. Most often, this is what is indicated as nominal. If only the amplitude value is known, it should be reduced to the effective value by dividing by 1.41 (a rounded number, but sufficient for everyday calculations, the square root of two). And then, using the formula, calculate the power.

Expression of current strength

Often, when choosing a suitable socket, plug, circuit breaker, meter and other similar equipment, it becomes necessary to find the current strength in the network. To do this, the formula is converted to the following form: I=P/U. Considering that power is often indicated in kilowatts, this figure should be converted to watts by multiplying by 1000.

If the voltage is in kilovolts, it cannot always be converted to volts by multiplying. This is due to the fact that this figure is often rounded. For example, the value of 0.4 kV is used in both Russia and Europe, but indicates an actual voltage of 380 V and 400 V, respectively. This means that European loads will remain operational in Russian networks at reduced voltage, but the opposite is not guaranteed.

Differences between "kVA" and "kW"

Thermal resistance

Sometimes on the surface of the device panel or in its description, kVA is used instead of the traditional kW for electrical power. In order for the consumer to be able to determine what value in kVA he needs, he should know that they measure the full value of the quantity, and in kW - the active value.

The total power indicator includes everything that the power source transmits externally, but it is not necessarily completely spent on doing the work. One of its fractions (active) performs work or is transformed into thermal form, the other (reactive) is redirected to the electromagnetic field available in the network. These are different quantities, although they have identical dimensions. In order not to confuse them, volt-amperes, rather than watts, are used to measure the full indicator. The pragmatic meaning of apparent power is that it describes the actual loads created by the consumer on the components of the electrical network. After all, these loads depend on how much current is consumed. Because of this, it is customary to use the volt-ampere value to indicate the power rating of switchboards and transformer devices.

When choosing a power source, it is often not clear to the consumer how much power it can actually provide. This is due to the fact that the technical parameters of such devices record the full power value in VA, and knowledge of how VA and W are related is required.

Unit conversion rules

In the instructions for many devices there are designations in volt-amperes. Their distinction is necessary only for specialists for whom these nuances are important professionally, but for ordinary consumers this is not so important, because the designations used in this case characterize almost the same thing. As for kilowatt/hour and just kilowatt, these are two different quantities that should not be confused under any circumstances.

To determine electrical power through the network current indicator, you can use various tools with which measurements and calculations are made:

• using a tester;
• using clamp meters;
• making calculations on a calculator;
• using special reference books.

Using a tester, we measure the voltage in the electrical network we are interested in, and then use a current clamp to determine the current strength. Having obtained the necessary indicators and applying the existing formula for calculating direct and alternating current, you can calculate the power. We divide the existing result in watts by 1000 and get the number of kilowatts.

Single phase electrical circuit

Basically, all household electrical networks are single-phase networks that use a voltage of 220 volts. The load marking for them is written in kilowatts, and the current strength is in amperes and is designated as AB.

To convert one unit to another, the formula of Ohm's law is used, which states that power (P) is equal to current (I) multiplied by voltage (U). That is, the calculation will look like this:

W = 1A x 1V

In practice, such a calculation can be applied, for example, to the designations on old electricity meters, where the installed machine is designed for 12 A. Substituting digital values ​​into the existing formula, we get:

12A x 220V = 2640 W = 2.6 kW

Calculations for an electrical network with direct and alternating current are practically no different, but are valid only in the presence of active devices that consume energy, for example, incandescent electric lamps. And when devices with a capacitive load are connected to the network, then a phase shift appears between current and voltage, which is the power factor, written as cos φ. When there is only an active load, this parameter is usually equal to 1, but when there is a reactive load in the network, it must be taken into account.

In cases where the network load is mixed, the value of this parameter fluctuates around 0.85. Reducing the reactive component of power leads to a reduction in losses in the network, which increases the power factor. Many manufacturers, when marking a device, indicate this parameter on the label.

Three-phase electrical network

If we take the example of a three-phase network, then everything is somewhat different here, since three phases are involved. When making calculations, you need to take the value of the electric current of one of the phases, which is multiplied by the voltage in this phase, after which the resulting result is multiplied by cos φ, that is, by the phase shift.

Having thus counted the voltage in each phase, we add up the results and obtain the total power of the device, which is connected to a three-phase network. In formulas it looks like this:

Watt = √3 Ampere x Volt or P = √3 x U x I

Ampere = √3 Volt or I = P/√3 x U

It must be borne in mind that there is a difference between phase and line voltage and current. But the calculation formula remains the same, except for the case when the connection is made in the form of a triangle, and it is necessary to calculate the load of an individual connection.

For circuits with alternating current, there is an unspoken rule for this calculation: the current strength is divided in half to select the power of the protective and starting relays. The same rule applies when calculating the diameter of the conductor in such electrical circuits.

Why is there a need to move from amperes to kilowatts and back?

It is impossible to reduce the description of an electrical network to just one unit. The need to use two different units of measurement of parameters arises due to the fact that in the vast majority of cases, a particular wiring serves several consumers, each of which contributes to the strength of the flowing current.

As a result

• It is convenient to calculate the cross-section of the wires based on the maximum strength of the current flowing through them;
• circuit breakers that protect receivers and wires from overload and short circuit are selected in the same way;
• The main characteristic of any electrical device connected to a socket as a current collector or load is traditionally its power.

The popularity of indicating power consumption, as one of the main parameters of an electrical appliance, is also determined by the fact that payment for electricity is carried out using an electric meter, which is calibrated in kWh.

Accordingly, given the known cost of one kW*hour, payment for electricity is determined by simply multiplying three numbers: power, operating time and cost of one kW*hour.

Taking into account the peculiarities of determining electricity costs, it becomes clear the advantage of using for powerful devices not useful power, measured in kW, but total power, which is determined in kVA.

It is advantageous in that it makes it possible to perform calculations using a single method without separately taking into account the actual phase shift of current and voltage.

The principle of identical calculations when knowing the total power also applies to current calculations.

The conversion from one unit to another is carried out according to the relations (1) and (2) presented above and, due to their simplicity, does not pose any big problems.

In this case, the fact that voltage U can be considered a constant, which varies only depending on the number of wiring phases, plays a role.

Below we present the basic rules for performing such calculations in relation to the most common cases in practice.

Conversions from amps to kilowatts and vice versa

You can convert values ​​in three ways: a universal table, an online calculator or a formula. As for using the calculator, you need to insert the initial indicators into the appropriate fields and press the button. It is convenient to use this system when you have to deal with large digital values.

Note! According to the universal table and formula, you can find out that one A contains 0.22 kW or 0.38 kW. You can convert values ​​using the available numbers using a calculator or by multiplying by the given value. For example, to calculate how much 6A will be in kW, you need to multiply 0.6 by 0.22. The result will be 1.32 kW.

In a single-phase electrical circuit

To calculate the required values ​​in a single-phase network, where the rated current of the circuit breaker, for example, is 10 A and in normal condition no energy flows through it above the specified value, it is necessary to calculate the maximum electrical power. You need to substitute the values ​​of voltage and electric current into the formula for finding power and multiply them together. It turns out that the power will be equal to 220*10=2200 watts. To convert to smaller values, you need to divide the figure by 1000. The result is 5.5 kW. This is the entire amount of power supplied from the machine.

Translation in a single-phase electrical circuit

In a three-phase electrical circuit

The conversion of indicators in a three-phase network designed for 380 volts can be done in a similar way. The difference lies in the formula. To determine the required data, you need to substitute the root of three into the product of voltage and electric current. For example, the machine is designed for 40 A. By substituting the values, you can get 26327 W. After dividing the value by 1000, the result is 26.3 kW. That is, it turns out that the machine will be able to withstand the load.

With a known power indicator of a three-phase circuit, the operating current can be calculated by transforming this formula. That is, the electrical power must be divided by the root of 3 multiplied by the voltage. As a result, if the electrical power is 10 kW, the value of the machine will be 16A.

Translation in a three-phase electrical circuit

Calculation of the cross-section of copper wires and cables

Having calculated the load and decided on the material (copper), let’s consider an example of calculating the cross-section of wires for individual groups of consumers, using the example of a two-room apartment.

As you know, the entire load is divided into two groups: power and lighting.

In our case, the main power load will be the socket group installed in the kitchen and bathroom. Since the most powerful equipment is installed there (electric kettle, microwave, refrigerator, boiler, washing machine, etc.).

For this socket group we select a wire with a cross section of 2.5 mm2. Provided that the power load will be scattered across different outlets. What does it mean? For example, in the kitchen, to connect all household appliances, you need 3-4 sockets connected with copper wire with a cross-section of 2.5 mm2 each.

If all equipment is connected through one single socket, then a cross-section of 2.5 mm2 will not be enough, in this case you need to use a wire with a cross-section of 4-6 mm2. In living rooms, a wire with a cross section of 1.5 mm2 can be used to power sockets, but the final choice must be made after appropriate calculations.

The entire lighting load is powered by a wire with a cross section of 1.5 mm2.

It is necessary to understand that the power in different sections of the electrical wiring will be different, and accordingly the cross-section of the supply wires will also be different. Its greatest value will be in the introductory section of the apartment, since the entire load passes through it. The cross-section of the input supply wire is selected 4 - 6 mm2.

When installing electrical wiring, wires and cables of the PVS, VVGng, PPV, APPV brands are used.

Cable cross-section by power (table)

Now we get to the essence of our article. However, everything that was above cannot be missed, which means we could not remain silent.

If we try to present the idea logically and simply, then a current of a certain strength can pass through each conventional cross-section of a conductor. This conclusion is quite logical and now all that remains is to find out these ratios and correlate them for different wire diameters, based on its type series.

It also cannot be ignored that here, when calculating the current cross section, temperature also comes into play. Yes, this is a new component – ​​temperature. It is she who can influence the cross section. How and why, let's figure it out.

We all know about Brownian motion. On the constant displacement of ions in a crystal lattice. All this happens in all materials, including conductors. The higher the temperature, the greater these vibrations of ions within the material will be. And we know that current is the directed movement of particles.

So, the directed movement of particles will collide with ions in the crystal lattice, which will lead to an increase in resistance to current.

The higher the temperature, the higher the electrical resistance of the conductor. Therefore, by default, the wire cross-section for a certain current is taken at room temperature, that is, at 18 degrees Celsius. It is at this temperature that all reference values ​​are given in the tables, including ours.

Despite the fact that we do not consider aluminum wires as wires for electrical wiring, at least in an apartment, they are nevertheless used in many places. Let's say for wiring on the street. That is why we will also present the values ​​of the cross-section and current dependencies for aluminum wires.

So, for copper and aluminum there will be the following indicators of the dependence of the cross-section of the wire (cable) on the current (power). See table.

Table of conductors for maximum permissible current for their use in wiring:

Since 2001, aluminum wires have not been used for wiring in apartments. (PEU)

Yes, here, as our reader noted, we actually did not provide calculations, but only provided reference data, tabulated, based on these calculations. But we dare to tell you that for calculations it is necessary to go through many formulas and indicators. Starting from temperature, resistivity, current density and the like.

Therefore, we will leave such calculations for specialists. It should be noted that they are not final, since they may vary slightly depending on the standard for the material and the current reserve of the wire used in different countries.

But what we would also like to talk about is converting the wire cross-section to diameter. This is necessary when there is a wire, but for some reason there is no marking on it. In this case, the cross-section can be calculated from the diameter of the wire, and vice versa from the diameter of the cross-section.

Common cross-sections for wiring in an apartment

We talked a lot about names, materials, individual characteristics and even temperature, but we lost sight of life circumstances.

So, if you hire an electrician to conduct wiring in the rooms of your apartment or house, then the following values ​​are usually accepted. For lighting, the wire cross-section is taken at 1.5 mm 2, and for sockets at 2.5 mm 2.

If the wiring is intended for connecting boilers, heaters, stoves, then the cross-section of the wire (cable) is already calculated individually.

Selecting the wire cross-section based on the number of consumers

What I also wanted to say is that it is better to use several independent power lines for each room in a room or apartment. Thus, you will not use a wire with a cross-section of 10 mm 2 for the entire apartment, routed to all rooms, from which there are taps.

Such a wire will come to the input machine, and then from it, in accordance with the power of the consumed load, selected wire sections will be routed for each of the rooms.

Typical electrical wiring diagram for an apartment or house with an electric stove (indicating the cable cross-section for electrical appliances)

Necessary calculations

First you need to check the sockets that are connected to the selected machine. Sometimes an automatic device powers not only household appliances, but also lighting devices. If the electrical wiring in the house is not installed correctly, the entire supply may depend on only one device. They count the total number of consumers and add up the voltage they need to operate.

The result will be the sum of watts that the automatic device supplies to these devices. Most likely, the equipment will not be connected at the same time, but the formula will make it possible to calculate the maximum voltage consumption. If some device does not indicate a specific power, but its interval, then it is necessary to take the largest value.

Minimum values ​​are not taken into account, since in this case the machine will operate at full load. This is unacceptable, because there are interruptions in the network, and this will lead to breakdown of the disconnecting device. The voltage in private homes and in industrial enterprises is different. There are two types:

• single-phase network - 220 V;
• two-phase - 380 volts.

Single-phase network

In private homes, the voltage does not exceed 220 volts. In this case, you need to make calculations specifically for a single-phase network. General physical formula for voltage: U = P/I, where:

• U is voltage;
• P - electrical power;
• I is the current strength.

The result makes it possible to measure consumption in watts, but usually a value such as kilowatt is used. To do this, you need to divide the resulting number by 1000 (1 kW = 1000 W). You can understand the algorithm for calculating how many amperes are in 1 kilowatt using an example.

If in a single-phase network the consumption is 220 V, then the rating of the automatic device is calculated as follows: 220/200 = 1 ampere. If all devices use a total power of 0.13 kW, then you will need an automatic machine with 6 amperes (0.13/220 = 6 A). That is, now you can find out how many amperes are contained in kW: 1000/220 = 4.5 A.

Reverse calculations can be done in a similar way. If the network has a 5 A disconnect device, then you can determine the maximum power it can handle. In this case, amperes are multiplied by volts: 5x220 = 115 W. If the devices consume more power, then the machine will not be able to withstand it, it must be replaced with another. You can use the table for converting amperes to watts and kilowatts:

• 2 A = 0.4 and 1.3 kW for single- and three-phase networks, respectively;
• 6 amperes are 1.3 and 3.9 kilowatts;
• 10 A = 2.2 and 6.6 kW;
• 16 A - 3.5 kW for single-phase and 10.5 for a network with a voltage of 380 V;
• 20 amperes = 4.4 and 13.2 kilowatts;
• 25 A - 5.5 and 16.4 kW.

Conclusion

If we return to a single-phase 220V network, then there is a rule that 1 kW is equal to 4.54A, that is, 1A = 0.22 kW or 220V.

As can be seen from the above formulas and calculations, Ohm’s law is used throughout the calculations, where the electric current is the inverse of the resistance. Knowing now all the formulas necessary for calculations, you can independently carry out the necessary actions to select the automatic relay you need to connect, which can be included in the electrical network with the guarantee that all devices connected to it will be safe.

Voltage 380 volts

Calculations for a three-phase network are carried out using a different formula. The voltage in such rooms is 380 V, it is distributed over three wires. Therefore, it is possible to install an automatic shutdown device with a lower rating at the same power consumption. The formula looks like this: P = U x I x root of 3. This way you can find out how many watts are in 1 ampere. To determine the number of kW, you need W x (0.7 x 380).

You can better understand the peculiarities of the calculations using an example. The three-phase network voltage is 380 V, and power supply devices require 0.13 kW of power. You need to find out which machine is best to buy for such a room. To do this, use the formula: 130/380 = 0.5 amperes.

In a similar way, calculations can be carried out for a two-phase network. Its voltage is 266 V. One kilowatt will contain 3.7 A (1000/266). Accordingly, one ampere is equal to 266 watts. For a room with a two-phase network and a power consumption of 250 watts, a machine with a rating of 3.7 amperes is suitable. When choosing a device, you need to take into account the current strength, which is less in a three-phase network for the same amount of power consumption.

Terms of transfer

Calculation formulas will be useful both when purchasing a new circuit breaker and when choosing household appliances.

It is necessary to convert one value into another when choosing a cable cross-section for power. To do this, you need to find out the total current required by home appliances, taking into account their power. In some cases, reverse calculations are performed.

The ability to do physical calculations will not become unnecessary information; sometimes this knowledge can come in handy. Voltage in any network can become dangerous, so electrical wiring must be handled with care and attention. Incorrect connection leads to burnt wires or overloads of the automatic device. Formulas allow you to find out how many volts, watts and kilowatts are in 1 ampere.

Reasons for making a transfer

Power and current are key characteristics necessary for the proper selection of protective devices for equipment powered by electricity. Protection is needed to prevent melting of the wiring insulation and breakdown of units.

Electrical wiring supplying lighting, an electric stove, and a coffee machine must be protected by individually selected devices. After all, each consumer creates “its own” load - in other words, consumes a certain current.

By the way, the cables and wires that supply the listed household devices have a certain current-carrying capacity. The latter is dictated by the cross-section of the cores.

Each protective device must operate at the moment of a voltage surge that is dangerous for the type of equipment being protected or a group of technical devices. This means that RCDs and machines should be selected so that during a threat to a low-power device, the network is not completely disconnected, but only the branch for which this surge is critical.

The housings of the circuit breakers offered by the retail chain are marked with a number indicating the maximum permissible current. Naturally, it is indicated in Amperes.

But on the electrical appliances that are required to protect these machines, the power they consume is indicated. This is where the need for translation arises. Despite the fact that the units we are examining belong to different current characteristics, the connection between them is direct and quite close.

Amperes and kilowatts, which characterize the power consumption of household devices, help you choose the right protection.

Voltage is the potential difference, in other words, the work put into moving a charge from one point to another. It is expressed in Volts. Potential is the energy at each point where the charge is/was.

Current strength refers to the number of Amperes passing through a conductor in a specific unit of time. The essence of power is to reflect the speed at which the charge moved.

Power is indicated in Watts and Kilowatts. It is clear that the second option is used when an overly impressive four- or five-digit figure needs to be reduced for ease of perception. To do this, its value is simply divided by a thousand, and the remainder is rounded up as usual.

Powering high-power equipment requires a higher rate of energy flow. The maximum permissible voltage for it is higher than for low-power equipment. The machines selected for it should have a higher operating limit. Therefore, accurate selection according to the load with competent conversion of units is simply necessary.

FAQ

How many Watts are in Ampere?

If we are talking about a car network, then in one ampere there are 12 watts at a voltage of 12V. In a household electrical network of 220 Volts, a current of 1 ampere will be equal to the consumer power of 220 Watts, but if we are talking about an industrial network of 380 Volts, then 657 Watts per ampere.

12 amps how many watts?

How many watts of power at 12 amperes of current consumption will depend on the network voltage with which the consumer himself operates. So 12A it could be: 144 Watts in a 12V car network; 2640 Watts in a 220V network; 7889 Watts on a 380 Volt power supply.

220 watts how many amps?

The current strength of a 220 Watt consumer will differ depending on the network in which it operates. This can be: 18A at a voltage of 12 Volts, 1A if the voltage is 220 Volts, or 6A when current consumption occurs in a 380 Volt network.

5 amps how many watts?

To find out how many watts a 5 ampere source consumes, just use the formula P = I * U. That is, if the consumer is connected to a car network where there is only 12 Volts, then 5A will be 60W. When consuming 5 amperes in a 220V network, it means that the consumer’s power is 1100W. When the consumption of five amperes occurs in a two-phase 380V network, the source power is 3290 Watts.

Why do you need to convert amperes to kilowatts?

People have long been accustomed to the fact that on their electrical appliances the amount of energy consumed is indicated in kilowatts. But fuses, plugs and automatic sockets are marked in amperes, and not everyone will understand the first time how many kilowatts we are talking about. When faced with such a problematic situation, people wonder how to convert one value to another, what scheme to use for this, and what will it yield.

It is precisely because users have problems with these two concepts that electrical accessories and protective equipment are often selected incorrectly, which is extremely harmful. That is why every owner of a private house or apartment needs to learn how to independently deal with such values ​​so that the electricity system functions correctly and safely.

Sources

• https://kupi-elektriku.ru/osnovy-elektrotexniki/skol-ko-vatt-v-1-ampere-i-kak-ih-perevesti-po-formule-ili-s-pomosch-yu-programmy/
• https://electricvdome.ru/instrument-electrica/perevod-ampery-v-vatty.html
• https://TokIdet.ru/bazovye-znaniya/skolko-vatt-v-ampere.html
• https://soloserv.ru/stroitelstvo/ampery-v-vatty-formula-i-tablicza-perevoda-sily-toka-v-moshhnost-i-obratno
• https://www.calc.ru/voltamper-v-vatt.html?source=2.1
• https://220v.guru/fizicheskie-ponyatiya-i-pribory/ampermetry/kak-perevesti-1-amper-v-vatty-i-kilovatty.html
• https://etlib.ru/calc/amps-watts-conversion
• https://uk-parkovaya.ru/whatandwhy/tips/perevod-amper-v-kilovatty-i-vatty-tablica-formuly-primery.html