Buying household appliances often prompts thoughts about whether the machine will withstand the voltage. The owner of the room faces certain difficulties, because the current strength is measured in amperes, and the consumption in kilowatts or watts. It is necessary to calculate the ratio of the two measurement quantities. But not everyone knows how to convert amperes to watts, so you need to understand physical terms and formulas.
Content
- Necessary calculations
- Single-phase network
- Voltage 380 volts
- Terms of transfer
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 improperly installed, the entire supply may depend on only one device. The total number of consumers is calculated, the voltage that they need to work is added up.
The result will be the amount of watts that the automatic device delivers 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 indicator of the consumed voltage. If on some device not a certain power is indicated, but its interval, then it is necessary to take the largest value.
The minimum indicators 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 a breakdown of the disconnecting device. The tension in private homes and manufacturing plants is different. There are two types:
- single-phase network - 220 V;
- two-phase - 380 volts.
Single-phase network
In private houses, the voltage does not exceed 220 volts. In this case, it is necessary to make calculations specifically for a single-phase network. General physical formula of voltage: U = P / I, where:
- U is the voltage;
- P is the power of electricity;
- I is the current strength.
The result makes it possible to measure consumption in watts, but usually a value such as kilowatts is used. To do this, divide the resulting number by 1000 (1 kW = 1000 W). To understand the algorithm for calculating how many amperes are in 1 kilowatt, you can use 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 an automatic machine with 6 amps (0.13 / 220 = 6 A) will be needed. That is, now you can find out how many amperes are contained in kW: 1000/220 = 4.5 A.
Inverse calculations can be performed in a similar way. If the network has a 5 A disconnect device, then the maximum power that it can withstand can be determined. In this case, amperes are multiplied by volts: 5x220 = 115 watts. 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 one- and three-phase networks, respectively;
- 6 amperes is 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.
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. That's why an automatic shutdown device can be installed with a lower rating at the same power consumption. The formula looks like this: P = U x I x root of 3. Thus, 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 feature of the calculations using an example. The voltage of the three-phase network is 380 V, and the devices for power supply need a power of 0.13 kW. You need to find out which machine is better to buy for such a room. To do this, use the formula: 130/380 = 0.5 amperes.
In a similar way, you can carry out calculations for a two-phase network. It has a voltage of 266 V. One kilowatt will contain 3.7 A (1000/266). Respectively, in one ampere is 266 watts. For a room with a two-phase network and a power consumption of 250 watts, an automatic machine with a nominal value 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 with the same amount of power consumption.
Terms of transfer
Calculation formulas are useful both when buying a new circuit breaker and when choosing household appliances.
It is necessary to convert one value to another when choosing a cable cross-section for power. To do this, you need to find out the total current strength that is needed for home appliances, taking into account their power. In some cases, reverse calculations are performed.
The ability to do physical calculations will not be superfluous 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 wire burnout or overloading of the automatic device. Formulas allow you to find out how many volts, watts and kilowatts are in 1 ampere.
