When connecting heaters and other powerful consumers of electricity, it is necessary to take into account the compatibility of the power source, wiring, and circuit breakers. If you convert watts to amperes incorrectly, expensive, high-quality equipment will be damaged. This publication will help eliminate dangerous emergency situations.
Incorrect calculation can cause a fire
Tables of ratios of amperes, volts, watts, ohms
To simplify, the main parameters of the electrical circuit are explained using the example of the functioning of a conventional pipeline. The movement of fluid is ensured by the pressure difference. The narrowing (expansion) of the transport route changes the flow resistance accordingly. If necessary, using the listed parameters or experimentally, you can set the pipeline productivity in liters per unit of time.
By analogy with the above description, the potential difference (voltage) ensures the movement of electric charges (current). As the cross-section of the conductor decreases, the electrical resistance increases. Knowing the basic parameters, it is easy to calculate the power consumption of the connected load.
Table for calculating the comfort zone of “electronic” cigarettes
The specified power data corresponds to certain resistance and voltage values. Similar tables are compiled for converting Watts into amperes and other quantities. This example clearly demonstrates the main disadvantages of the tabular form:
- complexity of processing large amounts of data;
- discreteness of information provision;
- limited accuracy.
Graphical representation of basic formulas for calculating electrical parameters
Using calculations, you can convert volts to amperes quickly and accurately.
For your information. As an alternative, an electrical quantity converter is used, which is available for free use on reference and specialized websites on the Internet.
Formula for calculating current
One of the main parameters is the amount of current consumed by the device. However, many users whose main activity is not at all related to electrical engineering will find it difficult to quickly answer simple questions about how many milliamps are in an ampere and how to convert microamps to amperes. As part of the school physics course, we “went through” all this, but over the years, part of the knowledge gained is naturally forgotten, so a reminder of the basic definitions will be useful.
Electric current is the collective movement of charged particles - electrons or ions, in a particular medium (solid, liquid or gas). The magnitude of the current is equal to the number of charges crossing the cross section of the conductor perpendicular to the flow of particles per unit time:
I = Q / T, where I is current, Q is charge, T is time.
What is voltage, Volt [V]
How to calculate amperes
By creating a potential difference, they ensure the movement of charges. The unit of measurement is one Volt. This voltage ensures the movement of 1 Coulomb (C) of electric charge between the poles. During this process, work with energy of 1 Joule (J) is performed.
The same value (V) can be represented as the potential difference to release a unit power of 1 W (W) when the current is limited to one ampere. Similarly, it is permissible to use proportions when determining the relationship between voltage and electrical resistance (R). The listed dependencies can be expressed as follows:
V=J/C=W/A=A*R.
The simplest formulas are valid for calculating a DC network. If sinusoidal oscillations are considered, in addition to the amplitude, it is necessary to take into account the corresponding changes in voltage depending on time. The instantaneous value is described as follows:
Ut=Ua*sin(w*t+ϕ),
Where:
- Ua – maximum voltage deviation (amplitude);
- w – frequency;
- t – time;
- ϕ – phase (initial).
For simplified calculations, it is convenient to use the root mean square voltage ( Uc p), which is related to the amplitude value by the following proportion:
Ucр=Ua*(1/√2)≈ Ua*0.707.
How many amperes in a kilowatt and kilowatts in an ampere
kVA to kW - how to correctly convert power
The presented formulas show that direct conversion of power to amperes does not make sense. Depending on the calculation method, it is necessary to additionally take into account voltage or resistance. In two- and three-phase networks, corrections have to be made due to the sinusoidal shape of the signal. An additional influencing factor is the capacitive (inductive) nature of the load.
Table on how to convert watts to amperes
| Current, A | power, kWt | Minimum cross-section of the power supply conductor, sq. mm (for different materials) | ||
| 1 phase, 220V | 3 phases, 380 V | Aluminum | Copper | |
| 1 | 0,2 | 0,5 | 2,5 | 1 |
| 2 | 0,4 | 1,1 | 2,5 | 1 |
| 5 | 1,1 | 2,6 | 2,5 | 1 |
| 10 | 2,2 | 5,3 | 2,5 | 1,5 |
| 20 | 4,4 | 10,5 | 4 | 2,5 |
For a fairly accurate selection of circuit breakers and cables, ready-made reference data is suitable. It is recommended to calculate watts with a reserve to prevent overheating of the conductors when connecting the maximum load.
Conversion to Watt hours and back
Using an example, we will consider a laptop battery, on the case of which the capacity is indicated, say, 5200 mAh, and the voltage is 14.9 V. You need to divide 5200 by 1000, and you get 5.2 Ah. Next, 5.2 is multiplied by 14.9 and you get 78.48 Wh.
When converting Wh to mAh, count in the opposite direction. To do this, divide 78.48 by 14.9 - you get 4.9 Ah, which is multiplied by 1000 and gets the figure 4900 mAh.
So, what can the designation mAh mean? This is one of the key parameters when choosing a mobile device, on which battery life largely depends. But a battery, say 5000 mAh, can be drained in a day or in 5 hours - it all depends on what tasks are performed on the gadget. If you just listen to music, your smartphone will last longer on one charge than if you were using a “heavy” toy.
How many volts does 1 ampere contain?
kW to HP - how to convert correctly
As in the previous example, such questions are asked incorrectly. Converting voltage to current is possible only taking into account:
- electrical resistance of the circuit section;
- power;
- load characteristics;
- constant (variable) parameters of the power supply network.
However, it should be noted that in the Russian Federation, along with the international standard (SI), the non-system unit “Volt-ampere” is used. Its value is equal to 1 W of power, so there is no need to convert using additional coefficients. In this case we are talking about power supply with a sinusoidal signal in a single-phase network.
Volt-amp power refers to the total energy of the power source that is consumed per hour. Measure the actual voltage values at the generator terminals and the current in the connected circuit. This means that in real conditions some of the energy will be wasted on:
- thermal heating;
- electromagnetic oscillations created by reactive components.
What is mAh
It is immediately worth noting that some batteries indicate the unit of measurement mAh, while others indicate Wh.
The Wh unit is usually found on laptop batteries from the manufacturer Dell. And mAh - on batteries from ASUS, Toshiba and others. To understand the difference, let's delve into the definitions.
Laptops and smartphones do not require a powerful power source, so for them the unit of measurement used to determine capacity is milliamp hours (written as mAh). For car batteries, the unit is different - ampere-hours (Ah). A milliamp is one thousandth of an Ampere, and is the derivative of current and time.
Milliamp-hour is a unit of measurement that reflects the charge available in the battery. 1 mAh is a charge transmitted over an hour through a conductor with a characteristic current of 1 mA. If the capacity is indicated as 2000 mAh, the battery supplies a current of 2 A (2000 mA) during this hour.
mAh characteristics of the battery.
Another unit - Wh (watt-hour) - is the power reserve stored in the battery. 1 Wh = 1 W of power transmitted over an hour through a conductor. Based on it, you can roughly determine the operating time of the laptop on one battery charge. Let's say 90 Wh is written on the power supply housing. It is known that 1 W is consumed within an hour, and to really find out the battery life of a laptop that requires at least 60 W to operate: you need to divide 90 Wh by 60 W = 1.5 hours of battery life of the device.
Where does 60 W come from then? As a rule, this figure is indicated on laptop power supplies. These are the Volts and Amps values that must be multiplied to get the power rating (60 or 70 W).
Converting kilowatts to amperes (single-phase 220V network)
How to convert watts to amperes:
- make a list of all consumers: 5 LED lamps of 15 W each, heater 2.3 kW, laptop 120 W;
- recalculate into a single format: 2.3 * 1000 = 2,300 W;
- sum up the obtained values: 75 + 2,300 + 120 = 2,495 W;
- calculate the total current when all consumers are connected simultaneously:
I (current) = P (power) / U (voltage) = 2,495 / 220 = 11.34 A.
Select the machine with the nearest higher nominal value. For this example, a 16 A protective device is suitable. The serial product is designed for a load power of up to 3,500 W, which more than covers the existing needs. The power supply network is made of copper (aluminum) conductors with a cross-sectional area of 1.5 (2.5) square meters. mm, respectively.
Converting amperes to kilowatts (single-phase 220V network)
An example of how to calculate watts:
- a 15A circuit breaker is installed in the electrical panel (the nominal characteristics are indicated on the housing);
- To calculate the permissible load in a 220 V , the classic formula is used:
P (power, W) = U (voltage, Volt) * I (current, Ampere).
- Substituting the original values, perform the Watt calculation:
220*15= 3 300.
For your information. For convenience, the result obtained can be converted into multiple units: 3,300 W = 3.3 kW (kilowatts).
Using Internet calculators
Another method for quickly and error-free conversion of mA (or μA) into amperes and vice versa is provided by the Internet - calculators, which are offered by numerous sites with electrical engineering topics. Using such calculators is extremely simple: the known current value in amperes (mA, µA) is inserted into the text field on the monitor desktop, marked with the corresponding unit. After this, the value in the units required for the calculation will appear in the adjacent column.
Technical progress and the emergence of new technologies in the near future will make it possible to create devices with much lower power consumption, in which currents will be tens of times less than current values.
Thus, the next, in decreasing order, multiple unit “nano”, equal to one billionth of the basic unit or, in numerical terms, 10-9, will be in demand. So you should prepare for this, but for now you can practice on microamps.
Conversion of watts to amperes for three-phase alternating voltage
Sequencing:
- To select a suitable protective device, use the following formula:
I = P/ (U * √3)
- summarize the power of connected devices:
2,300 + 2,400 +1,800 = 6,500 W
- calculate the current in the circuit at maximum load:
6,500/(380 * 1.732) = 9.876 A.
Select a suitable machine for a three-phase network. In this example, a product rated at 10 A is suitable.
How to convert µA to amperes
Researchers and developers are working to create new, even lower current devices for which milliamps may be too large a unit. Then the next multiple of the unit that will be useful is “micro,” meaning one millionth of the base unit. A numeric factor in 10-6 format is easier to write than a decimal notation with a lot of zeros. The abbreviated name of the prefix “micro” in the Russian version is “mk”.
Thus, to convert the current value in µA to amperes, you simply need to divide its value by 1,000,000 (or multiply by 10-6). Conversely, to convert a value in amperes to µA, you must either multiply by 1,000,000 or divide by 10-6.
Conversion table from Volt-amps to Watts
Power losses when connecting a certain load are determined by the correction factor cos ϕ. With linear parameters (incandescent lamps, heating elements), the energy is almost completely used for useful work. In electric motors, reactive components degrade performance characteristics.
The cos ϕ is indicated in the accompanying documentation:
- 0.6-0.7 – worst indicators;
- 0.8-0.9 – average;
- 1 – minimal losses.
When connecting several devices, make a table for convenience. The calculation is made taking into account the active and reactive components.
Convert Volt Amperes to Watts, VA to kW
For calculation use the formula:
Pп (apparent power, kVA) = Pa (active power, kW)*cos ϕ.
Example:
- generator power in normal operating mode – 8 kW;
- The documentation for the connected machine indicates the power consumption:
7 kW and cos ϕ = 0.8
- When connecting such a load, the power source will not be able to provide the required operating mode:
8*0.8=6.4 kW.
Converting power units by dividing by voltage, converting with a calculator
To select a circuit breaker, use the following formulas:
- direct current (single-phase network 220 V ):
I = P/U,
- three-phase network 380 V :
I = P/ (U * √3).
The data obtained will be useful for selecting wiring, sockets, and other functional components.
Ampere calculator
For your information. On specialized websites you can find a Watt calculator and other programs for automated calculations.
