How to connect a single switch. How to wire a single key switch when replacing an outdoor outlet. Preparing to connect electrical appliances

The name "transformer" comes from Latin word“transformare”, which means “to transform, transform.” This is precisely its essence - the transformation of one voltage into alternating current by magnetic induction alternating current different voltage, but similar frequency. The main purpose of the transformer is to use it in electrical networks and power supplies for various devices.

Device and principle of operation

A transformer is a device for converting alternating current and voltage, having no moving parts.

The transformer device consists of one or more separate wire, sometimes tape, coils (windings), which are covered by a single magnetic flux. Coils are usually wound around a core (magnetic core). It is usually made of ferromagnetic material.

The figure schematically shows the operating principle of the transformer.

The figure shows that the primary winding is connected to the AC source, and the other (secondary) is connected to the load. In this case, an alternating current flows in the turns of the primary winding, its value is I1. And both coils are surrounded by a magnetic flux F, which produces an electromotive force in them.

If the secondary winding is without load, then this mode of operation of the converter is called “idling”. When the secondary coil is under load, a current I2 arises in it under the action of an electromotive force.

The output voltage depends directly on how many turns there are on the coils, and the current strength depends on the diameter (section) of the wire. In other words, if both coils have an equal number of turns, then the output voltage will be equal to the input voltage. And if you wind 2 times more turns on the secondary coil, then the output voltage will become 2 times higher than the input.

The resulting current also depends on the diameter of the winding wire. For example, with a large load and a small diameter of the wire, overheating of the winding, disruption of the integrity of the insulation, and even complete failure of the transformer can occur.

To avoid such situations, tables have been compiled for calculating the converter and selecting the wire diameter for a given output voltage.

Classification by type

Transformers are usually classified according to several criteria: by purpose, by installation method, by type of insulation, by voltage used, etc. Let's consider the most common types of devices.

Power converters

This type of device is used to supply and receive electrical energy to and from power lines with voltages up to 1150 kW. Hence the name - power. These devices operate at low frequencies - about 50−60 Hz. Their design features is that they can contain several windings, which are located on an armored core made of electrical steel. Moreover, low voltage coils can be powered in parallel.

This device is called a split-winding transformer. Usually power transformers placed in a container with transformer oil, and the most powerful units are cooled by an active system. For installation at substations and power plants, three-phase devices with a power of up to 4 thousand kVA are used. They are most widespread, since losses in them are reduced by 15% compared to single-phase ones.

Autotransformers (LATR)

This is a special type of low-frequency device. In it, the secondary winding is simultaneously part of the primary and vice versa. That is, the coils are connected not only magnetically, but also electrically. Different voltage it turns out from one winding, if several conclusions are made. By using fewer wires, the cost of the device is reduced. However, there is no galvanic isolation of the windings, and this is a significant drawback.

Autotransformers have found application in high-voltage networks and installations automatic control, for starting AC motors. It is advisable to use them at low transformation ratios. LATR is used to regulate voltage in laboratory conditions.

Current transformers

In such devices, the primary winding is connected directly to the current source, and the secondary winding is connected to devices with a small internal resistance. These may be protective or measuring devices. The most common type of current transformer is the measuring one.

It consists of a core made of laminated silicon cold-rolled electrical steel, with one or more separate secondary windings wound on it. While the primary one can simply be a bus or a wire with a measured current passed through the window of the magnetic circuit. For example, current clamps operate on this principle. The main characteristic of transformer current is the transformation ratio.

Such converters are safe and therefore have found application in current measurement and in relay protection circuits.

Pulse converters

IN modern world pulse systems have almost completely replaced heavy low-frequency transformers. Typically, a pulsed device is made on a ferrite core of various shapes and sizes:

• ring;
• kernel;
• cup;
• in the form of the letter W;
• U-shaped.

The superiority of such devices is beyond doubt - they are capable of operating at frequencies up to 500 kHz or more.

Since this is a high-frequency device, its dimensions decrease significantly with increasing frequency. A smaller amount of wire is consumed on the winding, and to obtain a high-frequency current in the first circuit, it is enough to simply connect a field-effect or bipolar transistor.

There are many more types of transformers: isolation, matching, peak transformers, dual choke, etc. All of them are widely used in modern industry.

Area of ​​application of devices

Today, it is perhaps difficult to imagine an area of ​​science and technology where transformers are not used. They are widely used for the following purposes:

Based on the variety of devices and types of purposes of transformers, it can be argued that today they are irreplaceable, devices used almost everywhere, thanks to which stability and achievement of the voltage values ​​required by the consumer are ensured for both civil networks and industrial networks.

With the discovery and beginning of the industrial use of electricity, the need arose to create systems for its conversion and delivery to consumers. This is how transformers appeared, the principle of operation of which will be discussed.

Their appearance was preceded by the discovery of the phenomenon of electromagnetic induction by the great English physicist Michael Faraday almost 200 years ago. Later, he and his American colleague D. Henry drew a diagram of the future transformer.

Faraday transformer

The first embodiment of the idea in iron took place in 1848 with the creation of an induction coil by the French mechanic G. Ruhmkorff. Russian scientists also made their contribution. In 1872, Moscow University professor A.G. Stoletov discovered the hysteresis loop and described the structure of a ferromagnet, and 4 years later, the outstanding Russian inventor P.N. Yablochkov received a patent for the invention of the first alternating current transformer.

How a transformer works and how it works

Transformers are the name of a huge “family” that includes single-phase, three-phase, step-down, step-up, measuring and many other types of transformers. Their main purpose is to convert one or more alternating current voltages to another based on electromagnetic induction at a constant frequency.

So, briefly, how the simplest single-phase transformer works. It consists of three main elements - the primary and secondary windings and the magnetic circuit that unites them into a single whole, on which they are, as it were, strung. The source is connected exclusively to primary winding, while the secondary one removes and transmits the already changed voltage to the consumer.

The primary winding connected to the network creates an alternating electromagnetic field in the magnetic circuit and forms a magnetic flux, which begins to circulate between the windings, inducing an electromotive force (EMF) in them. Its value depends on the number of turns in the windings. For example, to lower the voltage, it is necessary that there be more turns in the primary winding than in the secondary. It is on this principle that step-down and step-up transformers work.

An important feature of the transformer design is that the magnetic core has a steel structure, and the windings, usually cylindrical in shape, are isolated from it, are not directly connected to each other and have their own markings.

Voltage transformers

This is perhaps the most numerous type of transformer family. In a nutshell, their main function is to make the energy produced in power plants available for consumption by various devices. For this purpose, there is a power transmission system consisting of step-up and step-down transformer substations and power lines.

Initially, the electricity produced by the power plant is supplied to a step-up transformer substation(for example, from 12 to 500 kV). This is necessary in order to compensate for the inevitable losses of electricity during transmission over long distances.

The next stage is a step-down substation, from where electricity is supplied via a low-voltage line to a step-down transformer and then to the consumer in the form of a voltage of 220 V.

But the work of transformers does not end there. In most of those around us household electrical appliances- in PCs, TVs, printers, automatic washing machines, refrigerators, microwave ovens, DVD and even energy saving light bulbs Step-down transformers are installed. An example of an individual “pocket” transformer - Charger mobile phone(smartphone).

The gigantic variety of modern electronic devices and the functions they perform correspond to many various types transformers. This is not a complete list of them: power, pulse, welding, separating, matching, rotating, three-phase, peak transformers, current transformers, toroidal, rod and armor.

What are they, transformers of the future?

The transformer industry is considered to be quite conservative. Nevertheless, it also has to reckon with revolutionary changes in the field of electrical engineering, where nanotechnology is making itself known more and more loudly. Like many other devices, they are gradually getting smarter.

An active search is underway for new structural materials – insulating and magnetic – that can provide higher reliability of transformer equipment. One direction could be the use of amorphous materials, which will significantly increase its fire safety and reliability.

Explosion- and fire-proof transformers will appear in which chlorinated biphenyls, used to impregnate electrical insulating materials, will be replaced by non-toxic liquid, environmentally friendly dielectrics.

An example of this is SF6 power transformers, where the function of the coolant is performed by non-flammable SF6 gas, sulfur hexafluoride, instead of the far from safe transformer oil.

It’s a matter of time to create “smart” power grids equipped with semiconductor solid-state transformers with electronically controlled, with the help of which it will be possible to regulate the voltage depending on the needs of consumers, in particular, connect renewable and industrial power sources to the home network, or, conversely, turn off unnecessary ones when they are not needed.

Another promising direction– low-temperature superconducting transformers. Work on their creation began back in the 60s. The main problem faced by scientists is the enormous size of the cryogenic systems required to produce liquid helium. Everything changed in 1986, when high-temperature superconducting materials were discovered. Thanks to them, it became possible to abandon bulky cooling devices.

Superconducting transformers have a unique quality: when high density current losses in them are minimal, but when the current reaches critical values, the resistance from zero level increases sharply.

It is difficult for a person who is little familiar with electrical engineering to imagine what a transformer is, where it is involved, and the purpose of its design elements.

General information about the device

A transformer is a static electromagnetic device designed to convert current variable frequency with one voltage into alternating current with a different voltage, but with the same frequency, based on the phenomenon of electromagnetic induction.

Devices are used in all spheres of human activity: electric power industry, radio engineering, radio-electronic industry, household sphere.

Design

The transformer design assumes the presence of one or more individual coils(tape or wire), located under a single magnetic flux, wound on a core made of a ferromagnet.

The most important structural parts are as follows:

• winding;
• frame;
• magnetic circuit (core);
• cooling system;
• insulation system;
• additional parts necessary for protective purposes, for installation, to provide access to the output parts.

In devices you can most often see two types of winding: the primary, which receives electric current from an external power source, and the secondary, from which the voltage is removed.

The core provides improved return contact of the windings and has reduced magnetic flux resistance.

Some types of devices operating at ultrahigh and high frequencies are produced without a core.

The production of devices is established in three basic winding concepts:

• armored;
• toroidal;
• core.

The design of core transformers involves winding the winding onto the core strictly horizontally. In armor-type devices it is enclosed in a magnetic circuit and placed horizontally or vertically.

Reliability, operational features, the design and operating principle of the transformer are adopted without any influence from the principle of its manufacture.

Principle of operation

The operating principle of the transformer is based on the effect of mutual induction. The supply of a variable frequency current from a third-party electricity supplier to the inputs of the primary winding forms a magnetic field in the core with a variable flux passing through the secondary winding and inducing the formation of an electromotive force in it. Short-circuiting the secondary winding at the electricity receiver causes an electric current to pass through the receiver due to the influence of the electromotive force, and at the same time a load current is generated in the primary winding.

The purpose of the transformer is to move converted electrical energy (without changing its frequency) to secondary winding from the primary with a voltage suitable for the operation of consumers.

Classification by type

Power

An AC power transformer is a device used to transform electricity in supply networks and electrical installations of significant power.

Need for power plants is explained by the serious difference in the operating voltages of main power lines and city networks coming to end consumers required for the operation of machines and mechanisms powered by electricity.

Autotransformers

The design and principle of operation of a transformer in this design implies direct coupling of the primary and secondary windings, thanks to which their electromagnetic and electrical contact is simultaneously ensured. The windings of the devices have at least three terminals, differing in their voltage.

The main advantage of these devices should be called good efficiency, because not all the power is converted - this is significant for small differences in input and output voltages. The downside is that the transformer circuits are not isolated (lack of separation) from each other.

Current transformers

This term usually denotes a device powered directly from the electricity supplier, used to reduce the primary electric current to suitable values ​​for those used in measuring and protective circuits, alarms, and communications.

The primary winding of electric current transformers, the design of which provides for the absence of galvanic connections, is connected to a circuit with an alternating electric current to be determined, and electrical measuring instruments are connected to the secondary winding. The electric current flowing through it approximately corresponds to the current of the primary winding divided by the transformation ratio.

Voltage transformers

The purpose of these devices is to reduce voltage in measuring circuits, automation and relay protection. Such protective and electrical measuring circuits in devices for various purposes separated from circuits high voltage.

Pulse

These types of transformers are necessary for changing short-term video pulses, which, as a rule, are repeated in a certain period with a significant duty cycle, with a minimum change in their shape. The purpose of use is the transfer of an orthogonal electrical pulse with the steepest cut and front, a constant amplitude indicator.

The main requirement for devices of this type is the absence of distortion when transferring the shape of the converted voltage pulses. The action of a voltage of any shape on the input causes the output of a voltage pulse of an identical shape, but probably with a different range or changed polarity.

Separating

What an isolation transformer is becomes clear based on the definition itself - it is a device with a primary winding that is not electrically connected (i.e., separated) from the secondary windings.

There are two types of such devices:

• power;
• signal.

Power ones are used to improve the reliability of electrical networks in the event of an unexpected synchronous connection with the ground and live parts, or non-current carrying elements that are energized due to an insulation failure.

Signal signals are used to ensure galvanic isolation of electrical circuits.

Coordinating

How this type of transformer works is also clear from its name. Matching devices are devices used to match resistance with each other. individual elements electrical circuits with minimal change in signal shape. Also, devices of this type are used to eliminate galvanic interactions between individual parts of circuits.

Peak transformers

The principle of operation of peak transformers is based on transforming the nature of the voltage, from input sinusoidal to pulsed. The polarity after the transition changes after half the period.

Twin throttle

Its purpose, structure and principle of operation as a transformer are absolutely identical to devices with a pair of similar windings, which, in this case, are absolutely identical, wound counter-winding or coordinated.

You can also often find this device called a counter inductive filter. This indicates the scope of application of the device - input voltage filtering in power supplies, audio equipment, and digital devices.

Operating modes

Idling speed (XX)

This operating procedure is implemented by opening the secondary network, after which the flow of electric current in it stops. An no-load current flows in the primary winding; its component element is the magnetizing current.

When the secondary current is zero, the electromotive force of induction in the primary winding completely compensates for the voltage of the supply source, and therefore, when the load currents disappear, the current passing through the primary winding corresponds in its value to the magnetizing current.

The functional purpose of idle operation of transformers is to determine their most important parameters:

• transformation indicator;
• losses in the magnetic circuit.

Load mode

The mode is characterized by the operation of the device when voltage is applied to the inputs of the primary circuit and a load is connected to the secondary circuit. The loading current flows through the “secondary”, and in the primary - the total load current and the no-load current. This operating mode is considered predominant for the device.

The question of how a transformer operates in the main mode is answered by the basic law of induced emf. The principle is this: applying a load to the secondary winding causes the formation of a magnetic flux in the secondary circuit, which forms a loading electric current in the core. It is directed in the direction opposite to its flow, created by the primary winding. There is parity in the primary chain electromotive forces the electricity supplier and induction are not observed, the electric current is increased in the primary winding until the magnetic flux returns to its original value.

Short circuit (SC)

The device switches to this mode when the secondary circuit is briefly closed. Short circuit- a special type of load, the applied load - the resistance of the secondary winding - is the only one.

The principle of operation of a transformer in short-circuit mode is as follows: an insignificant amount comes to the primary winding AC voltage, the secondary leads are short-circuited. The input voltage is set so that the value of the closing current corresponds to the value of the rated electric current of the device. The voltage value determines the energy losses due to heating of the windings, as well as active resistance.

This mode is typical for measuring type devices.

Based on the variety of devices and types of purposes of transformers, we can say with confidence that today they are indispensable devices used almost everywhere, thanks to which stability is ensured and the voltage values ​​​​required by the consumer are achieved, both in civil networks and in industrial networks.

Used by man Electric Energy mainly produced in large power plants. These enterprises transmit electricity to district substations, which then distribute it to consumers.

Since power lines have electrical resistance, part of the energy electric current is lost, turning into heat. Direct current (DC) flows in one direction; alternating current (AC) periodically changes its direction. Initially, only direct current was used for power supply. For a number of reasons, transmission and conversion direct current associated with significant difficulties, so for safety reasons power plants transmitted it at low voltage. However, by the time the direct current reached consumers, the resistance had consumed 45 percent of its energy.

The solution was found in high voltage alternating current transmission, which can be easily changed using a transformer (picture below). Because high voltage lines less current is required to transmit the same amount of energy, its losses to overcome resistance have become much smaller. When the alternating current leaves the power plant, step-up transformers increase its voltage from 22,000 to 765,000 volts, and before entering homes, other step-down transformers reduce it to PO or 220 volts.

Transformer operating principle

Transformers increase or decrease AC voltage. The converted alternating current passes through the primary winding surrounding the steel core (picture above). Periodically changing current creates an alternating magnetic field in the core. When moved to the secondary winding, this magnetic field generates an alternating current in it. If the secondary winding has more turns than the primary, the output voltage will be higher than the input voltage.

Energy losses when direct current flows

Electrical power (P) is calculated by multiplying current (I) by voltage (V), i.e. P = I x V. If the voltage increases, the current required to provide a given power decreases. Low voltage DC power requires greater strength current than high voltage AC power to transmit the same amount of electricity.

AC current is easily transformed

Unlike direct current, alternating current periodically changes its direction. If an alternating current passes through the primary winding of a transformer (picture on the left), the resulting alternating magnetic field induces a current in the secondary winding. When direct current flows through the primary winding (figure on the right), no current arises in the secondary winding.

Pass-through switches allow you to control lighting from two or more at once various places. In some situations, this is not just an additional convenience, but also an urgent necessity.

You are invited to familiarize yourself with the operating features of pass-through switches, the main options for their connection and the installation instructions themselves.

Most often, such switches are used in the following places:

• on the stairs. You can install switches on the 1st and 2nd floors. We turn on the lights at the bottom, go up the stairs, and turn them off at the top. For houses with a height of more than two floors, additional switches can be added to the circuit;
• in the bedrooms. We install a switch at the entrance to the room, and another one or even two near the bed. We entered the bedroom, turned on the light, got ready for bed, lay down and turned off the lighting with a device installed near the bed;
• in the corridors. We install a switch at the beginning and at the end of the corridor. We go in, turn on the light, reach the end, turn it off.

The list can be continued for a very long time, because for almost every situation there is its own option for using a pass-through switch system.

Switch installation diagrams

There are several options for connecting the devices in question. We bring to your attention the most popular and successful of them.

The system is assembled from two single-type pass-through switches.

Each of these devices has one contact at the input and a pair of contacts at the output.

The “zero” wire is connected from the power source through the distribution box to the lighting fixture. The phase cable, also passing through the box, is connected to the common contact of the first switch. The output contacts of this switch are connected via a box to the output contacts of the next device.

Finally, the wire from the common contact of the 2nd switch is connected to the lighting fixture via a junction box.

There is an option that allows you to control from two places different groups lighting fixtures. For example, we need to organize the ability to control lighting in a room directly from the room itself and from the adjacent corridor. There is a chandelier with 5 lights. We can install a pass-through switch system to turn on and off two groups of light bulbs in our chandelier.

The diagram shows the option of dividing the light bulbs into 2 groups. One has 3, the other has 2. The number of lighting fixtures in groups can change at the discretion of the owner.

To set up such a system we also use 2 pass-through switches, but they must be double type, and not single, as in the previous version.

The double switch design has 2 contacts at the input and 4 at the output. Otherwise, the connection procedure remains similar to the previous method, only the number of cables and controlled lighting fixtures changes.

Find out what it looks like and also check out step by step instructions on connection, in our article.

This connection method differs from previous options only in that a cross switch is added to the circuit. This device has 2 contacts at the input and a similar number of contacts at the output.

You have become familiar with the most popular installation schemes for pass-through switches. However, the number of such devices does not necessarily have to be limited to two or three. If necessary, the circuit can be expanded to include the required number of devices. The principle of operation remains the same for all cases: at the beginning and at the end of the circuit, a single pass-through switch with three contacts is installed, and cross devices with four contacts are used as intermediate elements.

We install switches to control lighting from three different places

If with the arrangement of a system for controlling lighting from two different places Usually no problems arise, because the circuit has simplest form, then installing three switches can cause certain difficulties for an untrained installer.

We will look at how to install a system of two pass-through and one crossover switches. By analogy, you can assemble a chain from more devices.

Before you begin any further work, turn off the power supply.

To do this, find the corresponding switch in the in-house electrical panel or in the panel on the site (for apartment owners). Additionally, make sure that there is no voltage in the switch wires using a special indicator screwdriver. Also perform a similar check at the installation locations of the devices.

Set for work

1. Flathead and Phillips screwdrivers.
2. Wire stripping tool. Can be replaced with a regular knife.
3. Side cutters or pliers.
4. Level.
5. Indicator screwdriver.
6. Hammer.
7. Roulette.

To install, we must first prepare grooves in the wall for laying electrical cables, power the wires and extend them to the locations of the installed devices.

For gating concrete walls It is most convenient to use a hammer drill. If the partitions are made of limestone, it is better to make the indentations using a chisel, because In such material, the punch will leave a groove that is too wide and deep, which will make fixing the wire difficult and will require more cement or plaster consumption in the future.

It is not recommended to use a hammer drill for chipping brick walls - it can split the masonry. In such a situation, the only safe solution is to lay it in pre-adapted joints between the masonry elements.

Wooden walls are not grooved - the wires are laid in special protective boxes. Most often, the cable is pulled under the baseboard and brought out directly under the switch installation site.

First step. We begin the work by connecting the wires to the electrical panel. There should not be any difficulties at this stage - modern devices allow you to start up to 8 or more wires at once.

Important point! First we need to determine the optimal cable cross-section. Domestic power grids can hardly be called stable. The current strength in them constantly fluctuates, and in moments of overload it even increases to dangerous values. To avoid wiring problems, we use copper wires cross section from 2.5 mm 2.

Second step. Select a convenient height for installing switches. At this point, we focus entirely on our preferences.

Third step. Having decided on the installation height of the switches, we proceed to gating. The width and depth of the grooves are 1.5 times larger than the diameter of the wire.

Important point! The wires are connected to the switches from below, so we install the groove 5-10 cm below the installation points of the switches. This requirement is relevant purely from practical side, because in such conditions, working with cables is easier and more convenient.

Fourth step. We lay the wires in grooves. We fix the wiring elements with small nails. We drive nails into the wall so that they support the cable and prevent it from falling out. Before attaching the wires, we need to place them under the switch (installation box). We will consider this point in the main section of the instructions. We will plaster the grooves after installing all the switches, making sure that the system is working.

Fifth step. We make holes for installing switches according to the size of the devices used.

Let's move on to the main stage of work.

Installing switches

First step. We turn it on under the switch. We cut the cables so that approximately 100 mm of their length remains in the installation box. Side cutters or pliers will help us with this. We remove approximately 1-1.5 cm of insulation from the ends of the wires.

Second step. Install the pass-through switch. We connect the phase cable (in our example it is white) to the terminal marked in the form of the letter L. We connect the remaining two cables to the terminals marked with arrows.

In your case, the color of the cables may vary. Don't know how to lay and connect the wires in the junction box? Then do the following. Turn off the electricity and find the phase. An indicator screwdriver will help you. A phase is a live cable. It is this that you connect to the terminal with the letter L, and the remaining wires are randomly connected to the terminals marked with arrows.

Third step. We install the cross switch. 4 wires are connected to it. We have a pair of cables, each of which has blue and white cores.

Let's understand the order of terminal markings on the switch. At the top we see a pair of arrows pointing “inside” the device, while at the bottom they are pointing “away” from it.

To the terminals at the top we connect the first pair of cables from the previously installed pass-through switch. We connect the remaining two cables to the terminals below.

To find live cables, we turn on the electricity and find the phases one by one. First, we determine the first one by changing the position of the key of the first pass-through switch. We find the next phase on the crossover switch cables. Next, we just have to connect the remaining wires to the terminals below.

Fourth step. Let's start connecting the last switch. We need to find the cables in it through which the voltage from the crossover switch flows. Our cables have blue and yellow. We connect them to the terminals marked with arrows. The white cable remains. We connect it to the terminal marked with the letter L.

We already know the procedure for identifying live cables. In the case of the second switch, we need to connect a wire that will not have voltage to the L terminal.

Fifth step. Carefully insert the device mechanisms into the mounting boxes. We carefully bend the wires to the base. We secure the devices. Fasteners in the mounting box or “claws” for clamping mechanisms will help us with this.

Sixth step.

Seventh step.

In conclusion, all we have to do is connect lighting with wires coming from distribution boxes, check the correct operation of the system and seal the grooves.

Good luck!

Video - Connection diagram for pass-through switch