In the modern technological world, electricity has practically become one level in importance with water and air. It is used in almost every sphere of human activity. There was such a thing as electricity as far back as 1600, before that we knew no more about electricity than the ancient Greeks. But over time, it Start spread more widely, and only in 1920 did it begin to crowd out kerosene lamps from street lighting. Since then, the electric current began to spread rapidly, and now it is even in the most remote village, at least covering the house and for telephone communications.
Electricity itself is a stream of directed charges moving through a conductor. A conductor is a substance capable of passing through these electric charges themselves, but each conductor there is resistance (except for the so-called superconductors, the resistance of superconductors is zero, this state is achievable by lowering the temperature to -273.4 degrees Celsius).
But in everyday life, of course, there are still no superconductors, and it will not be soon to appear on an industrial scale. In everyday life, as a rule, current is passed through the wires, and as a core it is used mainly
Content
- 1 How to understand the sections of copper and aluminum cables for wiring?
- 2 Calculation of wire cross-section for a network with a single phase (single phase)
- 3 Calculation of the wire section of the network with three phases (three-phase)
- 4 The concept of continuous current
How to understand the sections of copper and aluminum cables for wiring?
This article is intended to teach you how to calculate the cross section of the wire. It's like the more water you want to feed, the larger the diameter of the pipe you need. So here, the greater the consumption of electric current, the greater must be the cross section of cables and wires. Briefly I will describe what it is: if you cut a cable or wire, and look at it from the end, then you will see its cross section, that is, the thickness of the wire, which determines the power that this wire is able to miss, warming up to the allowable temperature
In order to properly choose the cross section of the power wire to us must take into account the maximum amount of current load consumed. It is possible to determine the values of the currents, knowing the power rating of the consumer, is determined by the following formula: I = P / 220, where P is the power of the current consumer, and 220 is the number of volts in your outlet. Accordingly, if the socket is 110 or 380 volts, then substitute this value.
It is important to know that the calculation of the value for single-phase and three-phase networks is different. In order to know how many phases of the network you need, you need to calculate the total amount of current consumption in your home. We give an example of the average set of equipment that can be in your home.
A simple example of the calculation of the cable cross-section on the current consumption, we now calculate the amount of power connected electrical appliances. The main consumers in an average apartment are such devices:
- TV - 160 watts
- Refrigerator - 300 W
- Lighting - 500 W
- Personal computer - 550 W
- A vacuum cleaner - 600 W
- Microwave oven - 700 W
- Electric kettle - 1150 W
- Iron - 1750 W
- Boiler (water heater) - 1950 W
- Washing a machine - 2650 W
- A total of 10310 W = 10.3 kW.
When we learned the total consumption of electricity, we can calculate the wire cross section by the formula, for the normal functioning of the wiring. It is important to remember that for single-phase and three-phase networks, the formulas will be different.
Calculation of wire cross-section for a network with a single phase (single phase)
The calculation of the wire cross section is carried out using the following formula:
I = (P × K and) / (U × cos (φ))
Where:
I - current strength;
- P - power of all energy consumers in the amount
- K and - the coefficient of simultaneity, as a rule, the generally accepted value of 0.75 is accepted for calculations.
- U - phase voltage, which is 220V but can vary from 210V to 240V.
- cos (φ) - for household single-phase appliances, this value is a steel, and is equal to 1.
If there is a need to calculate the current faster, then you can omit the cos (φ) value and the K and value. The result in this case is 15% lower if we apply the formula:
I = p / u
When we found the power consumption of the current according to the formula, we can begin to choose a cable which suits us in power. Rather, its cross-sectional area. Below is a special table in which the data are provided, which compares the amount of current, cable cross-section and power consumption.
Data may vary for wires made from different metals. Today, for use in residential areas, as a rule, copper, rigid cable is used. Aluminum cable is practically not used. But still in many old homes, aluminum cable is still present.
Table of the estimated cable power by current. The choice of the cross section of the copper cable is made according to the following parameters:
We also give a table for calculating the current consumption of aluminum cable:
If the power value turned out to be an average between two indicators, then it is necessary to choose the value of the wire cross section in a larger direction. Since the power reserve must be present.
Calculation of the wire section of the network with three phases (three-phase)
And now we will analyze the formula for calculating the wire cross section for three-phase networks.
To calculate the cross section of the power cable, we use the following formula:
I = P / (√3 × U × cos (φ))
Where:
- I - current, which selects the cable cross-sectional area
- U - phase voltage, 220V
- Cos φ - phase angle
- P - shows the total consumption of all electrical appliances
Cos φ - in the above formula is extremely important, as it affects the strength of the current itself. It differs for different equipment, with this parameter most often can be found in the technical documentation, or the corresponding marking on the case.
The total power is very simple, we summarize the value of all power indicators, and use the resulting number in the calculations.
A distinctive feature of a three-phase network is that a thinner wire is able to withstand a greater load. The required wire section is selected according to the table below.
The calculation of the wire cross-section for the current consumed used in a three-phase network is used using such a value as √3. This value is needed to simplify the appearance of the formula itself:
U linear = √3 × U phase
In this way, when the need arises, the product of the root and phase voltage is replaced by the line voltage. This value is 380V (U linear = 380V).
The concept of continuous current
Also one not less important point when choosing a cable for a three-phase and single-phase network is that it is necessary to take into account such a concept that sounds like a permissible continuous current. This parameter shows us the strength of the current in the cable that the wire can withstand for an unlimited amount of time. You can define ego in a special table. Also for aluminum and copper conductors, they are significantly different.
In the case when this parameter exceeds the allowable values, overheating of the conductor begins. The heating temperature is inversely proportional to the strength of the current.
Temperatures may increase in some areas. not only because of the wrong wire size, but also in case of poor contact. For example, in the place of twisting the wires. This happens quite often at the point of contact of copper and aluminum cables. In this regard, the surface of the metals undergoes oxidation, being covered with an oxide film, which greatly deteriorates the contact. In such a place the cable will heat up above the permissible temperature.
When we have done all the calculations, and checked the data from the tables, you can safely go to a specialized store and buy the cables you need to lay the network at home or in the country. Your main advantage over, for example, your neighbor will be that you fully understand this question with the help of our article, and save a lot of money without overpaying for what you wanted to sell score. Yes, and knowing how to calculate the current cross-section for copper or aluminum wires will never be superfluous, and we are sure that the knowledge gained from us will be useful in your life path many times.