Schemes for connecting the electric motor to the power supply. Connecting a three-phase motor to a three-phase network Three phases for the home

Content:

Many owners, especially owners of private houses or cottages, use equipment with 380 V motors powered by three-phase network. If an appropriate power supply circuit is connected to the site, then no difficulties arise with their connection. However, quite often a situation arises when a section is powered by only one phase, that is, only two wires are connected - phase and neutral. In such cases, you have to decide how to connect a three-phase motor to a 220 volt network. This can be done in various ways, but it should be remembered that such intervention and attempts to change parameters will lead to a drop in power and a decrease in the overall efficiency of the electric motor.

Connecting a 3-phase 220 motor without capacitors

As a rule, circuits without capacitors are used to start low-power three-phase motors in a single-phase network - from 0.5 to 2.2 kilowatts. Start-up time is spent approximately the same as when operating in three-phase mode.

These circuits are used under the control of pulses with different polarities. There are also symmetrical dinistors that supply control signals to the flow of all half-cycles present in the supply voltage.

There are two options for connecting and starting. The first option is used for electric motors with a speed of less than 1500 per minute. The windings are connected in a triangle. A special chain is used as a phase-shifting device. By changing the resistance, a voltage is generated across the capacitor, shifted by a certain angle relative to the main voltage. When the capacitor reaches the voltage level required for switching, the dinistor and triac are triggered, causing activation of the power bidirectional switch.

The second option is used when starting engines whose rotation speed is 3000 rpm. This category also includes devices installed on mechanisms that require a large moment of resistance during startup. In this case, it is necessary to provide a large starting torque. To this end, changes were made to the previous circuit, and the capacitors required for the phase shift were replaced by two electronic switches. The first switch is connected in series with the phase winding, leading to an inductive shift of the current in it. The connection of the second switch is parallel to the phase winding, which contributes to the formation of a leading capacitive current shift in it.

This connection diagram takes into account the motor windings, which are displaced in space by 120 0 C. When setting, the optimal angle of current shift in the phase windings is determined, ensuring reliable starting of the device. When performing this action, it is quite possible to do without any special equipment.

Connecting a 380V to 220V electric motor via a capacitor

For a normal connection, you should know the principle of operation of a three-phase motor. When connected to the network, current begins to flow alternately through its windings at different times. That is, in a certain period of time, the current passes through the poles of each phase, also creating a rotational magnetic field in turn. It exerts an influence on the rotor winding, causing rotation by pushing in different planes at certain times.

When such a motor is connected to a single-phase network, only one winding will participate in the creation of rotating torque and the impact on the rotor in this case occurs only in one plane. This force is completely insufficient to shift and rotate the rotor. Therefore, in order to shift the phase of the pole current, it is necessary to use phase-shifting capacitors. The normal operation of a three-phase electric motor largely depends on the correct choice of capacitor.

Calculation of a capacitor for a three-phase motor in a single-phase network:

With an electric motor power of no more than 1.5 kW, one operating capacitor will be sufficient in the circuit.
If the engine power is more than 1.5 kW or it experiences heavy loads during startup, in this case two capacitors are installed at once - a working one and a starting one. Their connection is carried out in parallel, and starting capacitor It is needed only for startup, after which it automatically turns off.
The operation of the circuit is controlled by the START button and the power off toggle switch. To start the engine, press the start button and hold it until it is fully turned on.

If it is necessary to ensure rotation in different directions, an additional toggle switch is installed that switches the direction of rotation of the rotor. The first main output of the toggle switch is connected to the capacitor, the second to the neutral, and the third to the phase wire. If such a circuit contributes to a weak increase in speed, in this case it may be necessary to install an additional starting capacitor.

Connecting a 3-phase motor at 220 without loss of power

The simplest and effective way It is considered to connect a three-phase motor to a single-phase network by connecting a third contact connected to a phase-shifting capacitor.

The highest output power that can be obtained in domestic conditions is up to 70% of the rated one. Such results are obtained when using the “triangle” scheme. Two contacts in distribution box directly connected to the wires of a single-phase network. The connection of the third contact is made through a working capacitor with any of the first two contacts or wires of the network.

In the absence of loads, a three-phase motor can be started using only a run capacitor. However, if there is even a small load, the speed will increase very slowly, or the engine will not start at all. In this case, an additional connection of a starting capacitor will be required. It turns on for literally 2-3 seconds so that the engine speed can reach 70% of the nominal speed. After this, the capacitor is immediately turned off and discharged.

Thus, when deciding how to connect a three-phase motor to a 220 volt network, all factors must be taken into account. Special attention should be given to capacitors, since the operation of the entire system depends on their action.

It happens that a three-phase electric motor falls into your hands. It is from such engines that homemade circular saws, emery machines and various types of shredders are made. In general, a good owner knows what can be done with it. But the trouble is, a three-phase network in private homes is very rare, and it is not always possible to install it. But there are several ways to connect such a motor to a 220V network.

It should be understood that the engine power with such a connection, no matter how hard you try, will drop noticeably. Thus, a delta connection uses only 70% of the engine power, and a star connection uses even less - only 50%.

In this regard, it is desirable to have a more powerful engine.

Important! When connecting the motor, be extremely careful. Take your time. When changing the circuit, turn off the power supply and discharge the capacitor with an electric lamp. Work with at least two people.

So, in any connection scheme, capacitors are used. In essence, they act as the third phase. Thanks to it, the phase to which one terminal of the capacitor is connected shifts exactly as much as necessary to simulate the third phase. Moreover, to operate the engine, one tank is used (working), and for starting, another (starting) is used in parallel with the working one. Although this is not always necessary.

For example, for a lawn mower with a blade in the form of a sharpened blade, a 1 kW unit and only working capacitors will be sufficient, without the need for containers for starting. This is due to the fact that the engine is idling when starting and it has enough energy to spin the shaft.

If you take circular saw, a hood or other device that puts an initial load on the shaft, then you can’t do without additional banks of capacitors for starting. Someone may say: “why not connect the maximum capacity so that there is not enough?” But it's not that simple. With such a connection, the motor will overheat and may fail. Don't risk your equipment.

Important! Whatever the capacitance of the capacitors, their operating voltage must be at least 400V, V otherwise they will not work for long and may explode.

Let's first consider how a three-phase motor is connected to a 380V network.

Three-phase motors come with either three terminals - for connection to a star only - or with six connections, with the ability to select a circuit - star or delta. The classic scheme can be seen in the figure. Here in the picture on the left there is a star connection. The photo on the right shows how it looks on a real engine frame.

It can be seen that for this it is necessary to install special jumpers on the required pins. These jumpers come with the motor. In the case where there are only 3 terminals, the star connection is already made inside the motor housing. In this case, it is simply impossible to change the winding connection diagram.

Some say that they did this to prevent workers from stealing units from home for their own needs. Be that as it may, such engine options can be successfully used for garage purposes, but their power will be noticeably lower than those connected by a triangle.

Connection diagram for a 3-phase motor in a 220V network connected by a star.

As you can see, the 220V voltage is distributed over two series-connected windings, where each is designed for such a voltage. Therefore, the power is lost almost twice, but such an engine can be used in many low-power devices.

The maximum power of a 380V motor in a 220V network can only be achieved using a delta connection. In addition to minimal power losses, the engine speed also remains unchanged. Here, each winding is used for its own operating voltage, hence the power. The connection diagram for such an electric motor is shown in Figure 1.

Fig. 2 shows a terminal with a 6-pin terminal for delta connection. The three resulting outputs are supplied with: phase, zero and one terminal of the capacitor. The direction of rotation of the electric motor depends on where the second terminal of the capacitor is connected - phase or zero.

In the photo: an electric motor only with working capacitors without starting capacitors.

If there is an initial load on the shaft, it is necessary to use capacitors for starting. They are connected in parallel with the workers using a button or switch at the time of switching on. As soon as the engine reaches maximum speed, the starting tanks should be disconnected from the workers. If it is a button, we simply release it, and if it is a switch, then we turn it off. Then the engine uses only working capacitors. Such a connection is shown in the photo.

How to select capacitors for a three-phase motor using it in a 220V network.

The first thing you need to know is that the capacitors must be non-polar, that is, not electrolytic. It is best to use containers of the brand ― MBGO. They were successfully used in the USSR and in our time. They perfectly withstand voltage, current surges and the damaging effects of the environment.

They also have mounting eyes that help you easily place them at any point on the device’s body. Unfortunately, getting them now is problematic, but there are many other modern capacitors that are no worse than the first ones. The main thing is that, as mentioned above, their operating voltage is not less than 400V.

Calculation of capacitors. Working capacitor capacity.

In order not to resort to long formulas and torture your brain, there is a simple way to calculate a capacitor for a 380V motor. For every 100 W (0.1 kW) 7 µF is taken. For example, if the motor is 1 kW, then we calculate it like this: 7 * 10 = 70 µF. It is extremely difficult to find such a capacity in one jar, and it is also expensive. Therefore, most often the containers are connected in parallel, gaining the required capacity.

Starting capacitor capacity.

This value is taken at the rate of 2-3 times greater than the capacity of the working capacitor. It should be taken into account that this capacity is taken in total with the working capacity, that is, for a 1 kW motor, the working capacity is equal to 70 μF, multiply it by 2 or 3, and get the required value. This is 70-140 µF of additional capacitance - starting. At the moment of switching on, it is connected to the working one and the total is 140-210 µF.

Features of the selection of capacitors.

Capacitors, both working and starting, can be selected using the method from smallest to largest. Having thus selected the average capacity, you can gradually add and monitor the operating mode of the engine so that it does not overheat and has enough power on the shaft. Also, the starting capacitor is selected by adding until it starts smoothly without delays.

Content:

The operation of three-phase electric motors is considered to be much more efficient and productive than single-phase motors designed for 220 V. Therefore, if there are three phases, it is recommended to connect the appropriate three-phase equipment. As a result, connecting a three-phase motor to a three-phase network ensures not only economical, but also stable operation of the device. The connection diagram does not require the addition of any starting devices, since immediately after starting the engine, a magnetic field is formed in its stator windings. The main condition for the normal operation of such devices is the correct connection and compliance with all recommendations.

Connection diagrams

The magnetic field created by the three windings ensures the rotation of the electric motor rotor. Thus, Electric Energy transforms into mechanical.

The connection can be made in two main ways - star or triangle. Each of them has its own advantages and disadvantages. Star circuit provides more smooth start unit, however, the engine power drops by about 30% of the nominal. In this case, the delta connection has certain advantages, since there is no loss of power. However, this also has its own peculiarity associated with the current load, which increases sharply during startup. This condition has a negative impact on the insulation of wires. The insulation may be punctured and the engine may fail completely.

Particular attention should be paid to European equipment equipped with electric motors designed for voltages of 400/690 V. They are recommended for connection to our 380 volt networks only using the delta method. If connected with a star, such motors immediately burn out under load. This method is applicable only to domestic three-phase electric motors.

Modern units have a connection box into which the ends of the windings are led out. Their number can be three or six. In the first case, the connection diagram is initially assumed to be a star method. In the second case, the electric motor can be connected to a three-phase network in both ways. That is, with a star circuit, the three ends located at the beginning of the windings are connected into a common twist. The opposite ends are connected to the phases of the 380 V network from which power is supplied. With the triangle option, all ends of the windings are connected in series to each other. The phases are connected to three points at which the ends of the windings are connected to each other.

Using a star-delta circuit

A combined connection diagram known as “star-delta” is used relatively rarely. It allows for a smooth start with a star circuit, and during the main operation a triangle is turned on, providing maximum power to the unit.

This connection diagram is quite complex, requiring the use of three windings installed in the connections at once. The first MP is connected to the network and with the ends of the windings. MP-2 and MP-3 are connected to opposite ends of the windings. The delta connection is made to the second starter, and the star connection is made to the third. Simultaneous activation of the second and third starters is strictly prohibited. This will cause a short circuit between the phases connected to them. To prevent such situations, an interlock is installed between these starters. When one MP turns on, the contacts of the other open.

The entire system operates according to the following principle: simultaneously with MP-1 being turned on, MP-3, connected by a star, is turned on. After soft start engine, after a certain period of time set by the relay, the transition to normal operating mode occurs. Next, MP-3 is turned off and MP-2 is turned on according to a triangle diagram.

Three-phase motor with magnetic starter

Connecting a three-phase motor using a magnetic starter is carried out in the same way as through circuit breaker. This circuit is simply supplemented with an on/off block with corresponding START and STOP buttons.

One normally closed phase connected to the motor is connected to the START button. When pressed, the contacts close, after which current flows to the motor. However, it should be noted that if the START button is released, the contacts will be open and no power will be supplied. To prevent this, the magnetic starter is equipped with another additional contact connector, the so-called self-retaining contact. It acts as a locking element and prevents the circuit from breaking when the START button is turned off. The circuit can only be completely disconnected using the STOP button.

Thus, connecting a three-phase motor to a three-phase network can be done in various ways. Each of them is selected in accordance with the unit model and specific operating conditions.

A correctly chosen meter is the main assistant in saving. To do right choice When purchasing, the first thing you have to decide is single-phase or three-phase. But how do they differ, how does installation occur, and what are the pros and cons of each?

In a word, single-phase ones are suitable for a network with a voltage of 220V, and three-phase ones are suitable for a voltage of 380V. The first of them - single-phase - are well known to everyone, as they are installed in apartments, office buildings and private garages. But three-phase ones, which were previously used in most cases in enterprises, are increasingly being used in private or country houses. The reason for this was the increase in the number of household electrical appliances requiring more powerful power.

The solution was found in the electrification of houses with three-phase cable inputs, and to measure incoming energy, many models of three-phase meters equipped with useful features. Let's deal with everything in order.

Perform electricity metering in two-wire networks alternating current with voltage 220V. And three-phase - in three-phase alternating current networks (3 and 4-wire) with a nominal frequency of 50 Hz.

Single-phase power is most often used for electrification of the private sector, residential areas of cities, office and administrative premises, in which the power consumption is about 10 kW. Accordingly, in this case, electricity metering is carried out using single-phase meters, the great advantage of which is the simplicity of their design and installation, as well as ease of use (taking phases and readings).

But modern realities are such that over the past couple of decades the number of electrical appliances and their power has increased significantly. For this reason, not only enterprises, but also residential premises - especially in the private sector - are connected to three-phase power. But does this actually allow you to consume more power? According to the technical conditions for connection, it turns out that the power supply from a three-phase and single-phase network is almost equal - 15 kW and 10-15 kW, respectively.

The main advantage is the ability to directly connect three-phase electrical appliances, such as heaters, electric boilers, asynchronous motors, and powerful electric stoves. More precisely, there are two advantages at once. Firstly, with a three-phase power supply, these devices operate with higher quality parameters, and secondly, “phase imbalance” does not occur when several powerful electrical receivers are used simultaneously, since it is always possible to connect electrical appliances to a phase that is free from drawdown through “distortion”.

The increase in the need for three-phase power has led to an increase in the installation of three-phase meters. Compared to single-phase ones, they have higher accuracy of readings, but they are also larger in size and more complex in design, requiring a three-phase input.

The presence or absence of a neutral wire determines which meter will need to be installed: a three-wire one if there is no “zero”, and if there is one, a four-wire one. For this purpose, there are corresponding special symbols in its marking - 3 or 4. Direct and transformer connection meters are also distinguished (for currents of 100 A or more per phase).

To get a clearer idea of the advantages of single-phase and three-phase meters over each other, you should compare their pros and cons.

Let's start with where three-phase is inferior to single-phase:

a lot of hassle in connection with the mandatory obtaining of permission to install a meter and the likelihood of a refusal
Dimensions. If you previously used single-phase power with a meter of the same name, you should take care of the place to install the input panel, as well as the three-phase meter itself.

Advantages of three-phase design

Watch a video about the advantages of a three-phase network:

Let us list the advantages of this type of counter:

Allows you to save money. Many three-phase meters are equipped with tariffs, such as day and night, for example. This makes it possible from 11 pm to 7 am to use up to 50% less energy than with a similar load, but during the daytime.
Possibility of choosing a model that corresponds to specific wishes for the accuracy class. Depending on whether the purchased model is intended for use in a residential area or in an enterprise, there are names with an error of 0.2 to 2.5%;
The event log allows you to notate changes regarding voltage dynamics, active and reactive energy and directly transmit them to a computer or the corresponding communication center;

There are only three types of three-phase meters

Direct connection meters, which, like single-phase ones, are connected directly to a 220 or 380 V network. They have a throughput power of up to 60 kW, a maximum current level of no more than 100 A and also provide for the connection of small-section wires of about 15 mm2 (up to 25 mm2)
require connection via transformers, therefore suitable for networks of higher power. Before paying for consumed energy, you simply need to multiply the difference between the meter readings (current and previous) by the transformation ratio.
Indirect switching meters. Their connection occurs exclusively through voltage and current transformers. They are usually installed at large enterprises, as they are designed for energy metering through high-voltage connections.

When it comes to installing any of these meters, there may be a number of difficulties associated with them. After all, if for single-phase meters there is a universal circuit, then for three-phase meters there are several connection diagrams for each type. Now let's look at this clearly.

Direct or immediate switching devices

The connection diagram for this meter is in many ways (especially in terms of ease of implementation) similar to the installation diagram for a single-phase meter. It is indicated in the technical data sheet, as well as on back side covers. The main condition for connection is strict adherence to the order of connecting the wires according to the color indicated in the diagram and the correspondence of odd wire numbers to the input, and even numbers to the load.

The order of connecting the wires (indicated from left to right):

wire 1: yellow - input, phase A
wire 2: yellow - output, phase A
wire 3: green - input, phase B
wire 4: green - input, phase B
wire 5: red - input, phase C
wire 6: red - output, phase C
wire 7: blue - zero, input
wire 8: blue - zero, output

Semi-indirect counters

This connection occurs through current transformers. There are a large number of schemes for this inclusion, but the most common among them are:

The ten-wire connection diagram is the simplest, and therefore the most popular. To connect, you must follow the order of 11 wires from right to left: the first three are phase A, the second three are phase B, 7-9 for phase C, 10 are neutral.
Connection via terminal box - it is more complicated than the first one. The connection is made using test blocks;
A star connection, like the previous one, is quite complex, but requires fewer wires. First, the first unipolar outputs of the secondary winding are collected at a common point, and the next three from the other outputs are directed to the meter, and the current windings are also connected.

Indirect meters

Such meters are not installed for residential premises; they are intended for use in industrial enterprises. Responsibility for installation rests with qualified electricians.

Which device should you choose?

Although most often those who want to install a meter are literally informed about which model is required for this and it is very problematic to agree on its replacement, despite its obvious non-compliance with the requirements, it is still worth learning the basics of the criteria that a three-phase meter must meet in terms of its characteristics .

The choice of a meter begins with the question of its connection - through a transformer or directly to the network, which can be determined by the maximum current. Direct connected meters have currents of the order of 5-60/10-100 amperes, and semi-indirect ones - 5-7.5/5-10 amperes. The meter is also selected strictly according to these readings - if the current is 5-7.5A, then the meter should be similar, but not 5-10A, for example.

Secondly, we pay attention to the presence of a power profile and an internal tarifficator. What does this give? The tariffifier allows the meter to regulate tariff transitions and record the load schedule for any time period. And the profile records, records and stores power values over a period of time.

For clarity, let’s consider the characteristics of a three-phase meter using the example of its multi-tariff model:

It should be noted that today three-phase meters are widely used for single-phase networks and vice versa: when three single-phase meters are connected to a three-phase network at once.

The accuracy class is determined in values from 0.2 to 2.5. The larger this value, the greater the percentage of error. For residential premises, class 2 is considered the most optimal.

nominal frequency value: 50Hz
rated voltage value: V, 3x220/380, 3x100 and others

If when using instrument transformer secondary voltage is 100V, a meter of the same voltage class (100V) is required, as well as a transformer
value of total power consumed by voltage: 5 VA, and active power - 2 W

rated-maximum current value: A, 5-10, 5-50, 5-100
maximum value of total power consumed by current: up to 0.2VA
inclusion: transformer and direct
registration and accounting of active energy

In addition, the temperature range is important - the wider it is, the better. Average values range from minus 20 to plus 50 degrees.

You should also pay attention to the service life (depending on the model and quality of the meter, but on average it is 20 -40 years) and the inspection interval (5-10 years).

A big plus will be the presence of a built-in electric power modem, with the help of which indicators are exported via the power network. And the event log allows you to notate changes regarding voltage dynamics, active and reactive energy and directly transmit them to a computer or the appropriate communication center.

And the most important thing. After all, when choosing a meter, we first of all think about saving. So, to really save on electricity, you should pay attention to the availability of tariffs. According to this feature, meters are available in single, double and multi-tariff types.

For example, two-tariff ones consist of a combination of positions “ “, continuously replacing each other according to the schedule “7 a.m. -11 a.m.; 11 am -7 am” respectively. The cost of electricity at night is 50% lower than during the day, so it makes sense to operate appliances that require a lot of energy (electric ovens, washing machines, dishwashers, etc.) at night.

Practical advice on how to connect a three-phase electricity meter

This type of meter is connected through a three-phase type input circuit breaker (containing three or four contacts). It is worth immediately noting that replacing it with three single-pole ones is strictly prohibited. Switching of phase wires in three-phase switches must occur simultaneously.

In a three-phase meter, the wiring connection is as simple as possible. So, the first two wires are the input and output of the first phase, respectively; similarly, the third and fourth wires correspond to the input and output of the second, and the fifth and sixth wires correspond to the input and output of the third phase. The seventh wire corresponds to the input of the neutral conductor, and the eighth wire corresponds to the output of the neutral wire to the energy consumer in the premises.

Grounding is usually allocated to a separate block and is made in the form of a combined PEN wire or PE wire. The best option, if there is a separation into two wires.

Now we will analyze the installation of the meter step by step. Let's assume that there is a need to replace a three-phase direct-connection meter.

First, let's determine the reason for the replacement and the time for it.

It is preferable to replace the meter during the daytime for the simple reason that the lighting during this period is much better than from using a flashlight. This means that it will be more convenient and faster to carry out the work, which cannot but affect your wallet if you have to use the services of a paid electrician.

After this, it is necessary to relieve the voltage by changing the position of the switch on the circuit breaker.

After making sure that the phases have been removed, we dismantle the old electric meter.

The difficulties that may arise when installing a new meter are related to how different the manufacturers and models of the old and new meters are, and at the same time their shapes and dimensions.

We perform a preliminary fitting of the new meter, placing it within the perimeter of contact between the surface (wall) of the mounting and the body of the electric meter itself. It is important here that the side mounting holes of both of them coincide.

If the preliminary check showed some inconsistencies, we eliminate them by adding suitable mounting holes, extend the wires if the terminals of the new meter are located a little further, etc.

Now that everything fits together, let's start connecting. The connection sequence is as follows (from left to right): the first wire is phase A (input), the second is its output; the third is the input, and the fourth is the output of phase B; similarly - the 5th and 6th wires, corresponding to the input and output of phase C, the last two - the input and output of the neutral conductor.

Further installation of the electric meter occurs in accordance with the instructions supplied with it.

Among the precautions, which, considering the seriousness of the consequences, should be strictly adhered to, the main place is given to the taboo on any kind of amateur activity - the creation of unintended jumpers; actions that may lead to disruption of normal contact, etc. It is necessary to carefully ensure that the wires are well stretched.

It should be remembered that the meter can only be connected by a qualified electrician who has permission to carry out such work. After installation is completed, the meter will be sealed by a specialist.

Video about the practice of connecting a three-phase meter

In conclusion - briefly about the main points

The advantage of single-phase meters is the simplicity of their design and installation, as well as ease of use (taking phases and readings)
But three-phase ones have the highest accuracy of readings, although they are more complex in design, have large dimensions and require a three-phase input.
Allows you to save money. Thanks to tariffs such as day and night, from 11 pm to 7 am you can use up to 50% less energy than with the same load, but during the day.
Possibility to select accuracy class. Depending on whether the purchased model is intended for use in a residential area or in an enterprise, there are items with an error of 0.2 to 2.5%
The event log allows you to notate changes regarding voltage dynamics, active and reactive energy and directly transmit them to a computer or the corresponding communication center
The presence of a built-in electric power modem, with the help of which indicators are exported via the power network.

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 the other (zero). Three-phase network is a transmission system electric current, which flows through three wires and returns 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.

An increase in the load in the circuit leads to an increase in the current passing through the generator windings. As a result, the magnetic field resists rotation of the drive shaft to a greater extent. The rpm begins to decrease and commands an increase in drive power, for example by supplying more fuel to the engine internal combustion. The speed is restored and more electricity is generated.

A three-phase system consists of 3 circuits with an EMF of the same frequency and a phase shift of 120°.

Features of connecting power to a private home

Many people believe that a three-phase network in the house increases power consumption. In fact, the limit is set by the electricity supply organization and is determined by the following factors:

supplier capabilities;
number of consumers;
condition of the line and equipment.

To prevent voltage surges and phase imbalance, they should be loaded evenly. The calculation of a three-phase system is approximate, since it is impossible to accurately determine which devices in this moment will be connected. The presence of pulsed devices currently leads to increased energy consumption during their startup.

The electrical distribution panel for a three-phase connection is larger in size than for a single-phase supply. Options are possible with the installation of a small input panel, and the rest - made of plastic for each phase and for outbuildings.

Connection to the main line is realized via underground method and by air. Preference is given to the latter due to the small amount of work, low connection cost and ease of repair.

Nowadays it is convenient to make an air connection using a self-supporting insulated wire (SIP). The minimum cross-section of the aluminum core is 16 mm 2, which is sufficient for a private home.

The SIP is attached to the supports and the wall of the house using anchor brackets with clamps. Connection to main by air line and the input cable into the electrical panel of the house is made by branch piercing clamps. The cable is taken with non-combustible insulation (VVGng) and passed through a metal pipe inserted into the wall.

Air connection of three-phase power supply at home

At a distance from the nearest support, it is more necessary to install another pole. This is necessary to reduce loads that lead to sagging or broken wires.

The height of the connection point is 2.75 m and above.

Electrical distribution cabinet

Connection to a three-phase network is made according to the project, where inside the house consumers are divided into groups:

lighting;
sockets;
separate powerful devices.

Some loads can be disconnected for repairs while others are running.

The power of consumers is calculated for each group, where the wire of the required cross-section is selected: 1.5 mm 2 - for lighting, 2.5 mm 2 - for sockets and up to 4 mm 2 - for powerful devices.

The wiring is protected from short circuit and overloads by circuit breakers.

Electric meter

For any connection scheme, a metering device is required. 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 coefficient.

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 back cover device. The input and corresponding output of a 3-phase meter are indicated by the same color. The most common connection order is when the phases come first and the last wire is zero.

A 3-phase direct connection meter for a home is usually designed for a power of up to 60 kW.

Before choosing a multi-tariff model, you should coordinate the issue with the energy supply company. Modern devices with tarifficators make it possible to calculate electricity charges depending on the time of day, register and record power values over time.

The temperature readings of the devices are selected as widely as possible. On average they range from -20 to +50 °C. The service life of the devices reaches 40 years from calibration interval 5-10 years.

The meter is connected after the input three- or four-pole circuit breaker.

Three-phase load

Consumers include electric boilers, asynchronous electric motors and other electrical appliances. The advantage of using them is the uniform distribution of the load in each phase. If a three-phase network contains unevenly connected single-phase powerful loads, this can lead to phase imbalance. At the same time, electronic devices begin to malfunction, and lighting lamps glow dimly.

Connection diagram of a three-phase motor to a three-phase network

The operation of three-phase electric motors is different high performance and efficiency. No additional starting devices are required here. For normal operation, it is important to connect the device correctly and follow all recommendations.

The connection diagram of a three-phase motor to a three-phase network creates a rotating magnetic field with three windings connected in a star or delta.

Each method has its own advantages and disadvantages. The star circuit allows the engine to start smoothly, but its power is reduced by up to 30%. This loss is absent in the delta circuit, but at start-up current load much bigger.

The motors have a connection box where the winding terminals are located. If there are three of them, then the circuit is connected only by a star. With six terminals, the motor can be connected in any way.

Power consumption

It is important for the home owner to know how much energy is consumed. This is easy to calculate for all electrical appliances. Adding up all the powers 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 home where there is powerful equipment. One device can have 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 with three phases and a neutral enters the house. Voltage electrical network Electrical appliances are connected between the phases and the neutral wire. In addition, there may be a three-phase load.

The power calculation of a three-phase network is carried out in parts. First, it is advisable to calculate purely three-phase loads, for example a 15 kW electric boiler and a 3 kW asynchronous electric motor. The total power will be P = 15 + 3 = 18 kW. In this case, current I = Px1000/(√3xUxcosϕ) flows in the phase wire. For household electrical networks cosϕ = 0.95. Substituting into the formula numeric values, we obtain the current value I = 28.79 A.

Now you need to define single-phase loads. Let them be P A = 1.9 kW, P B = 1.8 kW, P C = 2.2 kW for the phases. The mixed load is determined by summation and is 23.9 kW. Maximum current will be I = 10.53 A (phase C). Adding it to the current from the three-phase load, we get I C = 39.32 A. The currents in the remaining phases will be I B = 37.4 kW, I A = 37.88 A.

When calculating the power of a three-phase network, it is convenient to use power tables taking into account the type of connection.

Using them it is convenient to select circuit breakers and determine wiring cross-sections.

Conclusion

With proper design and maintenance, a three-phase network is ideal for a private home. It allows you to evenly distribute the load across phases and connect additional power from electrical consumers, if the wiring cross-section allows.