2024 Author: Howard Calhoun | [email protected]. Last modified: 2024-01-02 13:48
Not every average person understands what electrical circuits are. In apartments, they are 99% single-phase, where the current flows to the consumer through one wire, and returns through another (zero). A three-phase network is a system for transmitting electric current, which flows through three wires with a return one at a time. Here the return wire is not overloaded due to the phase shift of the current. Electricity is generated by a generator driven by an external drive.
Increasing the load in the circuit leads to an increase in the strength of the current passing through the windings of the generator. As a result, the magnetic field resists the rotation of the drive shaft to a greater extent. The number of revolutions begins to decrease, and the speed controller commands to increase the power of the drive, for example by supplying more fuel to the internal combustion engine. RPM is restored and more power is generated.
Three-phase system consists of 3 circuits with EMF of the same frequency and a phase shift of 120°.
Features of connecting power to a private house
Many believe that a three-phase network in the house increases the power consumption. In fact, the limit is set by the power supply organization and is determined by factors:
- provider capabilities;
- number of consumers;
- condition of line and equipment.
To prevent power surges and phase imbalance, they should be loaded evenly. The calculation of a three-phase system is approximate, since it is impossible to determine exactly which devices will be connected at the moment. The presence of pulsed devices currently leads to increased power consumption when they are started.
Distribution electrical panel with a three-phase connection is taken larger than with a single-phase power supply. Options are possible with the installation of a small inlet shield, and the rest - made of plastic for each phase and for outbuildings.
Connection to the highway is carried out by underground method and overhead line. Preference is given to the latter due to the small amount of work, low cost of connection and ease of repair.
Now it is convenient to make an air connection using a self-supporting insulated wire (SIP). The minimum cross-section of an aluminum core is 16 mm2, which is more than enough for a private house.
SIP is attached to the supports and the wall of the house using anchor brackets with clamps. The connection to the main overhead line and the input cable to the electrical panel of the house is made with branch piercing clamps. The cable is taken fromnon-combustible insulation (VVGng) and is carried out through a metal pipe inserted into the wall.
Aerial connection of three-phase power at home
If the distance from the nearest support is more than 15 m, another pole must be installed. This is to reduce loads that cause sagging or broken wires.
Height of connection point is 2.75 m or more.
Electric distribution box
Connection to a three-phase network is carried out according to the project, where consumers are divided into groups inside the house:
- lighting;
- sockets;
- high-power individual appliances.
Some loads can be turned off for repair while others are running.
The power of consumers is calculated for each group, where a wire of the required cross section is selected: 1.5 mm2 - for lighting, 2.5 mm2- to sockets and up to 4 mm2 - to powerful appliances.
Wiring is protected from short circuit and overload by circuit breakers.
Electric meter
Any connection scheme requires an electricity meter. A 3-phase meter can be connected directly to the network (direct connection) or through a voltage transformer (semi-indirect), where the meter readings are multiplied by a factor.
It is important to follow the connection order, where odd numbers are power, and even numbers are load. The color of the wires is indicated in the description, and the diagram is placed on the back cover of the device. Input and corresponding output3-phase meters are indicated by one color. The most common connection order is when the phases go first, and the last wire is zero.
A 3-phase direct connection meter for the home is typically rated up to 60kW.
Before choosing a multi-tariff model, the issue should be agreed with the power supply company. Modern devices with metering devices make it possible to calculate the fee for electricity depending on the time of day, register and record power values over time.
Temperature indicators of devices are chosen as widely as possible. On average, they range from -20 to +50 °С. The service life of the devices reaches 40 years with a calibration interval of 5-10 years.
The meter is connected after the introductory three- or four-pole circuit breaker.
Three-phase load
Consumers include electric boilers, asynchronous electric motors and other electrical appliances. The advantage of their use is the uniform distribution of the load on each phase. If a three-phase network contains unevenly connected single-phase powerful loads, this can lead to phase imbalance. In this case, electronic devices begin to malfunction, and the lighting lamps glow dimly.
Scheme for connecting a three-phase motor to a three-phase network
The operation of three-phase electric motors is characterized by high performance and efficiency. It does not require the presence of additional starting devices. For normal operation, it is important to connect the device correctly.and follow all recommendations.
The scheme for connecting a three-phase motor to a three-phase network creates a rotating magnetic field with three windings connected by a star or a delta.
Each method has its advantages and disadvantages. The star circuit allows you to smoothly start the engine, but its power is reduced to 30%. This loss is absent in the delta circuit, but at start the current load is much higher.
Motors have a connection box where the winding leads are located. If there are three of them, then the circuit is connected only by a star. With six leads, the motor can be connected in any way.
Power consumption
For the owner of the house, it is important to know how much energy is consumed. This is easy to calculate for all electrical appliances. Adding all the power and dividing the result by 1000, we get the total consumption, for example 10 kW. For household electrical appliances, one phase is sufficient. However, current consumption increases significantly in a private house, where there is a powerful technique. One device can account for 4-5 kW.
It is important to plan the power consumption of a three-phase network at the design stage in order to ensure symmetry in voltages and currents.
A four-wire wire enters the house for three phases and a neutral. The voltage of the electrical network is 380/220 V. Electrical appliances for 220 V are connected between the phases and the neutral wire. In addition, there may also be a three-phase load.
Power calculationthree-phase network is made in parts. First, it is advisable to calculate purely three-phase loads, for example, a 15 kW electric boiler and a 3 kW asynchronous motor. The total power will be P=15 + 3=18 kW. In this case, the current I=Px1000/(√3xUxcosϕ) flows in the phase wire. For household electrical networks cosϕ=0.95. Substituting numerical values into the formula, we obtain the current value I=28.79 A.
Now the single-phase loads should be defined. Let the phases be PA=1.9 kW, PB=1.8 kW, PC=2.2 kW. The mixed load is determined by summation and is 23.9 kW. The maximum current will be I=10.53 A (phase C). Adding it to the current from the three-phase load, we get IC=39.32 A. The currents in the remaining phases will be IB=37.4 kW, I A=37.88 A.
In calculating the power of a three-phase network, it is convenient to use power tables, taking into account the type of connection.
It is convenient to select circuit breakers and determine the wiring sections using them.
Conclusion
When properly designed and maintained, a three-phase network is ideal for a private home. It allows you to evenly distribute the load across the phases and connect additional power consumers, if the wiring section allows.
Recommended:
Nuclear power plants. Nuclear power plants of Ukraine. Nuclear power plants in Russia
Modern energy needs of mankind are growing at a gigantic pace. Its consumption for lighting cities, for industrial and other needs of the national economy is increasing. Accordingly, more and more soot from burning coal and fuel oil is emitted into the atmosphere, and the greenhouse effect increases. In addition, there has been more and more talk in recent years about the introduction of electric vehicles, which will also contribute to the increase in electricity consumption
What is reactive power? Reactive power compensation. Reactive power calculation
In real production conditions, reactive power of an inductive nature prevails. The enterprises install not one electric meter, but two, one of which is active. And for the overexpenditure of energy “chased” in vain through power lines, the relevant authorities are mercilessly fined
Hydrodistributor R-80: diagram, device, connection, do-it-yourself repair
The R-80 hydraulic distributor is used on tractors manufactured by MTZ, designed to redistribute the circulating fluid of these units. The mixture flows from the pump into the working space of the cylinder. The design of the device makes it possible to adjust the oil pressure in the system, fix attachments in the required position
Three Gorges: the largest hydroelectric power station in the world
Three Gorges is not just the largest hydroelectric power station in the world, but also a national Chinese landmark that attracts many tourists from all over the world. The article tells about this largest hydraulic structure, located at the mouth of the Yangtze River, between the Chinese cities of Yichang and Chongqing
Golovnaya Zaramagskaya HPP: height above sea level, photo, location, connection diagram
North Ossetia is rich in wild mountain rivers. These rivers have enormous potential in hydropower. In 2009, the head Zaramagskaya HPP was launched. The river on which the hydroelectric power station is located is called Ardon
