Three-phase and single-phase networks are distributed approximately equally in private and apartment buildings. But it is worth noting that the industrial network is three-phase by default and in most cases to a street where private houses are located or a three-phase house is suitable for an apartment building network. And only then it is branched into three single-phase, and led to the final consumer of current.
The calculation was made not just like that, but with the aim of ensuring the most efficient transfer of electricity from the power plant to you, and also pursued the goal the greatest reduction in the loss of electricity in the transportation process, because the conductor, on which this current flowing.
If you are wondering which network you have in your house or apartment, then it is quite simple to determine. If you open the electrical panel and see how many wires are used for your apartment, then if you see 2 or 3 wires, it is a single-phase network, 1 and 2 wire is a phase and zero, 3 wire, if present, is grounding. In a three-phase network, the wires will be either 4 or 5. Three phases A, B, C, zero, and if present - grounding conductor.
The number of phases is also determined by the so-called sachet, an input circuit breaker. For a single-phase network, 2 or 1 dual cable is allocated, and in a three-phase network there will be 1 single cable and one single. But we should not forget about the tension with which you need to be very careful.
In order to make a calculation on the current, and a calculation on the voltage, it is easy to know the power, as a rule, three-phase networks need large power consumers. Using the formula given in the article, you can calculate the power, using the values of current and voltage, you can easily.
- 1 We recognize the power consumption of electricity
- 2 Three phase network
- 3 Calculate the power of a three-phase network
- 4 Payment
We recognize the power consumption of electricity
So, let's get to the creature, we need learn the power of electricity current and voltage. First you need to know how much energy you will consume. It is easy to find out by comparing all energy consumers in your home. Let's choose the most common technique, without which modern man cannot do. By the way, you can find out how much a particular device consumes in the passport data of your appliance, or on a tag that may be on the case. Let's start with the highest voltage consumption:
- Washer - 2700 Watts
- Water heater (boiler) - 2000 watts
- Iron - 1875 Watts
- Coffee maker - 1200 watts
- Vacuum cleaner - 1000 watts
- Microwave - 800 Watts
- Computer - 500 watts
- Lighting - 500 watts
- Refrigerator - 300 watts
- TV - 100 watts
According to the formula, we need to add everything and divide by 1000to convert from watts to kilowatts.
In total, we got 10975 watts, translated into kilowatts, divided by 1000.
Total consumption is 10.9 kW.
For the average man in the street is enough of one phase. Especially if you are not going to include everything at the same time, which, of course, is unlikely.
But we must remember that the current consumption can be significantly higher, especially if you live in a private house and / or you have a garage, then the consumption of one device can be 4-5 kW. Then you would prefer a three-phase network, as more powerful and allowing you to connect much more powerful current consumers.
Three phase network
Let's take a closer look at the three-phase network, as more preferred for us. To start we give a comparative characteristic single-phase and three-phase network. Highlight some pros and cons.
When a three-phase network is used, there is a probability that the load is distributed unevenly on each phase. If, for example, an electric boiler and a powerful heater are powered from the first phase, and a TV and a refrigerator from the second, it will have place of such phenomena as “phase imbalance” - asymmetry of voltages and currents, which may be due to the failure of some consumers current. To avoid such a situation, it is necessary to carefully plan the distribution of the load at the initial stage of network design.
Also a three-phase network will need more wires, cables and circuit breakers that transmit current, as the power will be much higher, respectively, the installation of such a network will be more expensive.
Single-phase network on the possible potential power inferior to three-phase. So if you intend to use many powerful current consumers, then the second option will be correspondingly better. For example, if a two-core (three-core if it is grounded) comes into the house, from a power line, the cable 16 mm2 section, then the total power of all electricity consumers in the house should not exceed 14 kW, as in the example, induced above.
But if you will use the same cross-section of the wire for a three-phase network, but accordingly cable will be 4-5 core, then already the maximum total power will be equal to 42 kW.
Calculate the power of a three-phase network
For the calculation we will take a certain production workshop in which thirty electric motors. A four-wire line comes into the workshop, remember that these are 3 phases: A, B, C, and neutral (zero). Rated voltage 380/220 volts. The total power of all engines is Ru1 - 48kW, we also have lighting lamps in the workshop, the total power of which is Ru2-2kW.
- Py - the installed total power of a group of consumers, the largest equal to the sum of their declared capacity, is measured in kW.
- Кс - demand factor at the highest load mode. The demand factor takes into account the largest possible number of inclusions of receivers of the group. For electric motors, the demand factor should take into account the magnitude of their load.
The demand factor for lighting (lighting) load, i.e. lighting, Кс2-0.9, and for power load, that is, electric motor Кс1 = 0.35. The average power factor for all consumers is cos (φ) = 0.75. Required find the calculated line current.
Calculate the calculated power load P1 = 0.35 * 48 = 16.8 kW
and the estimated lighting load P2 = 0.9 * 2 = 1.8 kW.
Full rated load P = 16.8 + 1.8 = 18.6 kW;
Rated current we consider using the formula:
Р - estimated power of the consumer (electric motors and lighting), kW;
Un is the nominal voltage at the terminals of the receiver, which is equal to the interfacial (linear when the phase and the phase are connected, ie 380 V), that is, the mains voltage from which it is powered, V;
cos (φ) is the power factor of the receiver.
So we produced current power calculationwhich will allow you to deal with three-phase networks. But going directly to the installation of the system, do not forget the safety precautions, because current and voltage is a dangerous phenomenon for your life.