Drivers of cars equipped with a manual gearbox, from time to time, in order to engage the desired gear, have to control the car using only one hand. In contrast, happy owners of vehicles with an automatic gearbox can hold the steering wheel with both hands throughout the entire movement. And now we will look at the basic types of automatic transmissions.

Summary :

Types of automatic transmission | Types of automatic transmissions

Classic hydraulic “Automatic” (automatic transmission) | Hydraulic automatic

A striking example of a classic automatic transmission is precisely hydraulic type automatic transmission, aka hydraulic automatic machine. The absence of a direct connection between the engine and the wheels is the peculiarity of of this type automatic transmission The question arises: how is torque transmitted? The answer is simple - two turbines and working fluid. As a result of the further “evolution” of this type of “automatic machine”, the role of control in them was taken over by specialized electronic devices, which made it possible to add special “winter” and “sport” modes to such automatic transmissions, a program for economical driving and the ability to change gears “manually” appeared.

Unlike a manual gearbox, a hydraulic “automatic” requires slightly more fuel and takes longer to accelerate. But this is the price you have to pay for comfort. And it was “hydraulics”, challenging “mechanics”, that won a landslide victory in many countries, except for “old Europe”.

How does an automatic transmission work?

For a long time, drivers in Europe have all types of automatic transmission was categorically not accepted. The engineers had to do a lot before finally adapting the automatic gearbox for Europe. But all this ultimately served to increase efficiency and the emergence of such modes as “winter” and “sport”. In addition, the box learned to adapt individually to the driver’s driving style, and it became possible to manually change gears with an automatic transmission - which was important for European drivers.

Each manufacturer preferred to call such transmissions in its own way, but the very first name to appear was - Autostick. One of the most widespread inventions today is considered to be the invention of the AUDI company - Tiptronic. BMW, for example, called such a transmission - Steptronic, Volvo considered it a suitable name for the automatic transmission Geartronic.

However, even though the driver engages the gears himself, he is not considered to be completely manual. This is more semi-automatic, because the transmission computer continues to control the operation of the car regardless of the selected mode.

Robotic gearbox | Automatic robot

MTA (Manual Transmission Automatically Shifted) - or so-called popularly, is structurally, perhaps, in many ways similar to “mechanics”, but from a control point of view, it is nothing more than an automatic transmission. And although fuel consumption here is more moderate than with the same manual transmission, there are also some nuances. The “robot” is very effective only at a very moderate driving pace.

The more aggressive your driving becomes, the more painful the gear changes feel. Sometimes when switching, it may even seem as if someone is pushing you into the rear bumper. That is difference between a robot (DSG) and an automatic machine lies in the principle of operation of the first. However, the low cost and low weight of the automatic transmission completely compensate for this disadvantage.

About the DSG box Video

Why does the Robot need two clutches?

Volkswagen Golf R32 DSG with 2 clutches

Existing shortcomings seriously complicated operation, and this had a particularly acute effect on driving comfort. Therefore, the designers, during a lengthy “search”, eventually came to a solution that solved the problems - they equipped the “robot” with two clutches.

In 2003, Volkswagen launched a robotic transmission with two clutches into mass production, installing it for the first time on the Golf R32. The name was given to him DSG(Direct Shift Gearbox). Here, even gears were controlled by one clutch disc, and odd gears by a second. This significantly softened the operation of the box, but another serious drawback appeared - the price of this automatic transmission is quite high. Although mass acceptance of such a transmission by car enthusiasts can solve this problem.

CVT | CVT gearbox

CVT transmission (Continuously Variable Transmission) - it changes torque smoothly, this is its feature. This type of automatic transmission does not have steps; its gears do not have a fixed gear ratio. And if we compare it with “hydraulics”, then we can monitor the work of the latter using the tachometer readings, but variator very measuredly picks up the moments of gear shifting while the speed balance remains unchanged.

CVT | Continuously variable transmission

Useful video about what a CVT transmission is

Features | Differences between a CVT and an automatic transmission.

Those drivers who are accustomed to “listening” to their car will not be able to love such a box, because, like a trolleybus, it does not change the tone of the engine. But it’s probably not worth abandoning the CVT for this reason. Engineers found a way out of this situation by adding a mode where “virtual gears” can be selected manually. The gearshift mode simulates, allowing the driver to feel like driving a normal car. automatic transmission gear shift.

How to determine which gearbox is installed in a car, CVT or hydraulic automatic:

1. If possible, study the technical documentation of the car. In most cases, the automatic is designated as AT (Automatic Transmission), the variator is designated CVT;
2. Look for information on the Internet. Usually in technical specifications You will definitely find the answer on popular sites;
3. Test drive. If the car is equipped with a variator, then you will not feel any, even subtle jolts or jerks; acceleration is similar to the acceleration of a “trolleybus”. On a classic automatic transmission you can feel the gear changes, although on a working one they are almost invisible, it is impossible not to “feel” them.

What is more reliable and better: a CVT, a robot or an automatic?

The development of power grid security tools has become relevant since their inception. Various overloads led not only to cable damage, but also to fires.

Today, the most popular devices of this type are circuit breakers.

They help prevent events such as fires and damage to electrical wiring. Since they are automatic, operation occurs without human intervention. Choosing the right switch will help protect the room from accidents.

Design and principle of operation

Understanding the automatic switch operation mechanism will help you select the right model. Structurally, the machine includes the following key elements:

• terminals;
• toggle switch;
• electromagnetic release;
• bimetallic plate.

Depending on the type of overload, one of two mechanisms is triggered.

If a circuit overload occurs with a current that exceeds the nominal value by several times, the bimetallic plate is triggered. It heats up within a few seconds, causing it to expand thermally. When it reaches a certain size, it bends significantly and the chain opens. The plate parameters are adjusted by the manufacturer. For switches used in everyday life, the response time takes 5–20 s. They are usually marked with the letters: B, C, D.

The short circuit (SC) mode is characterized by an avalanche-like increase in current, exceeding not only the nominal value, but also its maximum permissible loads. There is no time left for heating the plate during the jump, otherwise the wiring may melt. In such a situation, an electromagnetic release is triggered. The magnetic field moves the core, which opens the circuit. Instant operation allows you to protect the premises from the consequences of a short circuit.

Classification

Electric machines differ in the following key characteristics:

• number of poles;
• time current characteristic;
• operating current value;
• breaking capacity.

Number of poles

This characteristic corresponds to the number of electrical wiring lines that can be directly connected to the machine. All output wires will be disconnected simultaneously when the machine is triggered.

Single-pole circuit breaker. This is the simplest type of circuit protection devices. Only 2 wires are connected to it: one goes to the load, the second is power. It is placed on a standard 18 mm din strip. The power wire is supplied from the top, and the load is connected to the bottom terminal. It can work in electrical wiring lines with one, two or three phases. In addition to the power and load wires, it has a neutral and ground, which are connected to the corresponding buses. Such machines are not installed at the entrance, since the circuit will only open along the phase line. The neutral wiring remains closed and in the event of a failure, potential may remain on it.

A two-pole machine, its difference from a single-pole one. This type of circuit breaker allows you to completely cut off the electrical wiring in the room. It allows you to synchronize the moment when you turn off your two output lines. The latter leads to more high level safety during electrical installation work. It can be used as a separate toggle switch for appliances such as a water heater or washing machine. The connection is made using 4 cables: a pair at the input and output.

A simple question is logical: is it possible to connect two single-pole circuit breakers instead of one double-pole one? Of course not. After all, when a two-terminal switch is automatically triggered, all output lines are switched off. For a pair of independent machines, an overload may not occur on one of the lines and the blackout will be partial. IN ordinary apartments You can connect a phase and neutral line to this machine. When opened, there will be a complete blackout of the entire group of devices that are powered from it.

Three and four pole machines. All three or four phase wires are connected to the poles of the corresponding circuit breaker. They are used when connected by a star, when the phase wires are protected from overloads, and the middle wire remains switched all the time, or by a triangle, when there is no middle central cable, but the phase wires are protected.

If an overload occurs on one of the lines, a shutdown occurs immediately on all the others. These machines are connected to 6 (three-phase machine) or 8 wires. 3-4 at the output and the same number of lines at the output. They are mounted on DIN rails with a length of 54 (three-phase automatic) and 72 mm, respectively. They are most often used in industrial installations, when connecting powerful electric motors.

Time current parameter

Nutritional consumption patterns various devices varies even when the power values ​​are the same. Uneven dynamics of consumption during correct operation, a surge in load during switching on - all these phenomena lead to significant changes in such a parameter as current consumption. Power dispersion can lead to false tripping of the circuit breaker.

To eliminate such situations, dynamic operating parameters are introduced, called time-current characteristics of circuit breakers. Based on this parameter, machines are divided into several types. The triggering time of the machine is different for each group. Front panel switch is marked with the corresponding letter from the list: A, B, C, D, K, Z.

Rated current

The differences in automatic machines depending on the rated current values ​​are divided into several groups (12 current levels). It is directly related to the response time when power consumption is exceeded. The operating value can be determined purely theoretically by adding up the sums of currents consumed by each device separately. In this case, you should take a small reserve. You should also not forget about the electrical wiring options.

The machines are designed primarily to prevent damage. Depending on the metal of the wires and their cross-section, the maximum load is calculated. The current ratings of circuit breakers allow this division to be made.

Breaking capacity

This parameter depends on the maximum current value when a short circuit occurs, provided that the machine disconnects the network. Based on the magnitude of the short-circuit current, all circuit breakers are divided into three groups.

• The first includes devices with a rating of 4.5 kA. They are used in private houses intended for human habitation. The current limit is approximately 5 kA. This is due to the fact that the resistance of the conductive cable system leading to the house from the substation is 0.05 Ohm.
• The second group has rated 6 kA. This level is already used in residential apartment buildings And public places. Current limit can reach 5.5 kA (wiring resistance 0.04 Ohm). Models of the following types are used: B, C, D.
• In industrial installations the rating is 10 kA. The maximum current value that can occur in the circuit near the substation has the same value.

How to choose the right machine

Until recently, porcelain fuses with fusible elements were widely used. They were well suited for the same type of load in Soviet apartments. Nowadays, the number of household appliances has become much larger, as a result of which the likelihood of a fire with old fuses has increased. To prevent this, you need to carefully select a machine with the right characteristics. Excessive power reserves should be avoided. The final choice is made after completing a few simple steps.

Determination of the number of poles

When determining this switch parameter, you should follow a simple rule. If you plan to secure sections of the circuit with devices that have low power consumption (for example, lighting devices), then it is better to leave your choice on a single-pole circuit breaker (usually class B or C). If you plan to connect a complex household device with significant power consumption (washing machine, refrigerator), then a two-pole circuit breaker (class C, D) should be installed. If the equipment is small production workshop or a garage with multi-phase motor systems, then you should choose a three-pole option (class D).

Power consumption calculation

As a rule, by the time it is planned to connect the machine, the wiring to the room has already been installed. Based on the cross-section of the conductors and the type of metal (copper or aluminum), the maximum power can be determined. For example, for copper core in 2.5 mm 2 this value is 4–4.5 kW. But the wiring is often supplied with a large margin. Yes, and the calculation should be done before all installation work begins.

In this case, you will need a value about how much total power will be used by all devices. It is always possible to turn them on simultaneously. So, in an ordinary kitchen, the following appliances are often used:

• fridge– 500 W;
• electric kettle– 1700 W;
• microwave oven– 1800 W

The total load is 4 kW and a 25 A circuit breaker is enough for it. But there are always consumers who turn on sporadically and can create factors that contribute to the circuit breaker tripping. Such devices can be a combine or a mixer. Therefore, you should take a machine with a reserve of 500–1200 W.

Rated current calculation

Since power in single-phase networks is equal to the product of voltage and current, the current can easily be determined as the quotient of power and voltage. For the above example, this value is easy to calculate, knowing that the mains voltage is 220 V. The current consumed is 18.8 A. Taking into account a reserve of 500–1200 V, it will be 20.4–23.6 A.

In order to ensure that the work does not stop even with such short-term excess loads, the rated current for the machine can be taken equal to 25 A. The nominal current corresponds to approximately the same value, based on copper cable with a cross section of 2.5 mm 2, which is sufficient for such a load. A circuit breaker with a rated current of 25 A will work before it starts to heat up.

Determination of time current characteristic

This parameter is determined using a special table that lists the starting currents and their flow time. For example, for a household refrigerator, the starting current multiplicity is 5. With a power of 500 W, the operating current is 2.2 A. The starting current value will be 2.2 * 7 = 15.4 A. Periodicity data is also taken from a special table.

Table No. 1. Starting currents and pulse durations for household appliances

For the selected device, this characteristic does not exceed 3 s. The choice becomes obvious: for such a consumer it is necessary to take a type B circuit breaker. It is permissible to select a circuit breaker based on load power. You can skip the last step and opt for a class B switch. For domestic needs, the characteristics of class B and C electrical switches are most often sufficient.

Electrical circuit breakers perform the function of protecting wiring from overloads, short circuits, and accidents that may occur during voltage surges. So that it doesn't happen emergency, necessary in apartments, private houses, garages, cottages and outbuildings install electrical circuit breakers. When overloads or surges occur, the device reacts and operates differently. In one situation or another, individual parts of the device are triggered, while other parts continue to work, ensuring the safety of the home.

Operating principle of the circuit breaker

The switch has a compact, small size, the device is placed in plastic made of heat-resistant materials. On one side - the front - there is a handle that allows you to turn the device on and off, on the other - at the back - there is a latch, which is attached to a special DIN rail. Screw terminals are located at the bottom and top.

The operating principle of the switches depends on the state of the network and the flow of current through the wiring. When the device electrical switch is in normal mode, then a current passes through the machine, the indicators of which may be equal to or less than the set nominal value. The voltage from the external network goes to the upper terminal with a fixed contact. From here the current flows to a closed moving contact, and then passes to the solenoid coil, which is flexible copper conductor. From here the current goes to the thermal release, from which it flows to the lower terminal. It is she who is connected to the network.

Table of current circuit breaker ratings

The standard current that passes through the wiring may be more or less than the established values. Based on them, a classification of time-current characteristics for releases in devices has been compiled. Each type in the state standard is marked with a Latin letter, and the permissible excess should be sought using the coefficient formula - k=I/In.

Table 1 shows the norms for each type of time-current indicators.

Table 1

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Table 2 shows the time-current characteristics of the devices automatic shutdown current

Table 2

Type	Characteristic	Types of chains
A	Protection on the AB segment is activated when the coefficient is equal to 1.3. The current is turned off within 60 minutes. If the current continues to increase, the shutdown time is reduced exactly by half. Electromagnetic protection at a speed of 0.05 sec. will work if the nominal value exceeds 2 times.	They are not subject to short-term overloads and are used on an industrial scale, not in everyday life.
IN	The standard nominal value can be exceeded by 3-5 times. The solenoid is activated if the overload increases by 5 times. Then de-energization will occur within 0.015 seconds. The thermocouple will turn off within 4 seconds. already at three times the excess.	Characteristic for circuits without high inrush currents.
WITH	Overload occurs more often than with other types, the permissible indicators are 5 times higher than the norm. As soon as the standard mode is exceeded, the thermoelement will automatically turn off.	In household networks, where there is often a load of different types.
D	Exceeding the standard norm occurs 10 times, after which the thermoelement is turned off, and 20 times for the solenoid.	Used to protect starting devices carrying high current.
TO	The solenoid will turn off if the current exceeds 8 times.	Such devices must be installed on circuits that have an inductive load.
Z	A slight excess is typical - from 2 to 4 times.	Used to connect electronic devices.
M.A.	The thermocouple is not used to disconnect the load.	Installed on devices with electric motors.

Selection of circuit breaker by power

One of the main indicators by which a circuit breaker is selected is the load power. This allows you to calculate the required current value for the device and its protection against voltage surges. The calculation is carried out based on the rated current, so it is recommended to choose based on power individual areas. It is worth taking into account lower or nominal values ​​of calculated currents. The permissible current of the electrical wiring will be greater than the rated power of the circuit breaker.

It is also necessary to take into account such an indicator as the time-current characteristic of the device. The main parameter for determining the rated power is the cross-section of the wire. The permissible current value, which is indicated on the circuit breaker, should be slightly less than the maximum current for the wire cross-section. Select a device based on the smallest cross-section of the wire that is laid in the wiring.

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The dangers of a cable mismatch with the network load

If the circuit breaker does not match the network power and load, then it will not protect the wiring from the fact that the current strength and voltage sharply increases or decreases.

The cable cross-section for the network load must exactly match the power of the device. If the total power in different areas is greater than the nominal value, then the temperature will increase. This may cause the cable insulating layer to melt. As a result, a fire will start electrical wiring. Also, if the cable cross-section does not correspond to the load, the following phenomena will be observed:

• Smoke.
• Smell of burnt insulation.
• A flame appears.
• The switch will not be disconnected from the network, since the rated current through the wiring will not exceed permissible limits.

The process of melting the insulating layer will cause a short circuit over time. Next, the circuit breaker will turn off; at this time, the fire can engulf the entire house.

Weak link protection

The rules for electrical installations state that the switch for the electrical network must protect the weakest section as much as possible or contain a current rating that will fully correspond to the parameters of the installations that are included in the network. To connect wires to the network, you need to connect them cross sections had the total power of all connected devices.

Compliance with such rules can protect an apartment or house from an accident due to a weak section of electrical wiring. The described requirements cannot be ignored, since the homeowner is capable of losing not only the automatic power switch device, but also the apartment.

How to calculate the rating of a circuit breaker

• I - indicator/value of rated current.
• P is the total power of all installations that are included in the circuit. Light bulbs and other devices that consume electricity are taken into account.
• U is the current voltage in the network.

To calculate the denomination, you can use Table 3:

Connection type	Single phase in kilowatts	Three-phase (delta) in kilowatts	Three-phase (star) in kilowatts
U, B Automatic, in amperes	220	380	220
1 Ampere	0,2	1,1	0,7
2	0,4	2,3	1,3
3	0,7	3,4	2
6	1,3	6,8	4
10	2,2	11,4	6,6
16	3,5	18,2	10,6
20	4,4	22,8	13,2
25	5,5	28,5	16,5
32	7,0	36,5	21,1
40	8,8	45,6	26,4
50	11	57	33
63	13,9	71,8	41,6

Circuit breakers are devices whose task is to protect an electrical line from exposure to powerful current that can cause overheating of the cable with further melting of the insulating layer and fire. An increase in current strength can be caused by too much load, which occurs when the total power of the devices exceeds the value that the cable can withstand in its cross-section - in this case, the machine does not turn off immediately, but after the wire heats up to a certain level. During a short circuit, the current increases many times over within a fraction of a second, and the device immediately reacts to it, instantly stopping the supply of electricity to the circuit. In this material we will tell you what types of circuit breakers are and their characteristics.

Automatic safety switches: classification and differences

Beyond Devices protective shutdown, which are not used individually, there are 3 types of network circuit breakers. They work with loads different sizes and differ from each other in their design. These include:

• Modular AB. These devices are installed in household networks in which negligible currents flow. Typically have 1 or 2 poles and a width that is a multiple of 1.75 cm.

• Molded switches. They are designed to operate in industrial networks with currents up to 1 kA. They are made in a cast case, which is why they got their name.
• Air electric machines. These devices can have 3 or 4 poles and can handle currents up to 6.3 kA. Used in electrical circuits with high power installations.

There is another type of circuit breaker for protecting the electrical network - differential. We do not consider them separately, since such devices are ordinary circuit breakers that include an RCD.

Types of releases

Releases are the main operating components of the automatic circuit breaker. Their task is to ensure that if the permissible value current to break the circuit, thereby stopping the supply of electricity to it. There are two main types of these devices, differing from each other in the principle of tripping:

• Electromagnetic.
• Thermal.

Electromagnetic type releases ensure almost instantaneous operation of the circuit breaker and de-energization of a section of the circuit when a short circuit overcurrent occurs in it.

They are a coil (solenoid) with a core that is drawn inward under the influence of a large current and causes the tripping element to operate.

The main part of the thermal release is a bimetallic plate. When a current exceeding the rated value of the protective device passes through the circuit breaker, the plate begins to heat up and, bending to the side, touches the disconnecting element, which trips and de-energizes the circuit. The time it takes for the thermal release to operate depends on the magnitude of the overload current passing through the plate.

Some modern devices are equipped as an addition with minimum (zero) releases. They perform the function of turning off the AV when the voltage drops below the limit value corresponding to the technical data of the device. There are also remote releases, with the help of which you can not only turn off, but also turn on the AV, without even going to the distribution board.

The presence of these options significantly increases the cost of the device.

Number of poles

As already mentioned, the circuit breaker has poles - from one to four.

Selecting a device for a circuit based on their number is not at all difficult; you just need to know where they are used various types AB:

• Single-pole circuits are installed to protect lines that include sockets and lighting fixtures. They are mounted on phase wire, without capturing null.
• The two-terminal network must be included in the circuit to which it is connected household appliances with sufficiently high power (boilers, washing machines, electric stoves).
• Three-terminal networks are installed in semi-industrial networks, to which devices such as borehole pumps or auto repair shop equipment.
• Four-pole AVs allow you to protect electrical wiring with four cables from short circuits and overloads.

The use of machines of different polarities is shown in the following video:

Characteristics of circuit breakers

There is another classification of machines - according to their characteristics. This indicator indicates the degree of sensitivity of the protective device to exceeding the rated current. The corresponding marking will show how quickly the device will react in the event of an increase in current. Some types of AVs work instantly, while others will take some time.

There is the following marking of devices according to their sensitivity:

• A. Switches of this type are the most sensitive and react instantly to increased load. They are practically not installed in household networks, using them to protect circuits that include high-precision equipment.
• B. These machines operate when the current increases with a slight delay. They are usually included in lines with expensive household appliances(LCD TVs, computers and others).
• C. Such devices are the most common in household networks. They are turned off not immediately after increasing the current strength, but after some time, which makes it possible to normalize it with a slight difference.
• D. The sensitivity of these devices to increasing current is the lowest of all types listed. They are most often installed in shields at the line approach to the building. They provide security for apartment automatic machines, and if for some reason they do not work, they turn off the general network.

Features of the selection of machines

Some people think that the most reliable circuit breaker is the one that can handle the most current, and therefore can provide the most protection to the circuit. Based on this logic, you can connect an air-type machine to any network, and all problems will be solved. However, this is not at all true.

To protect circuits with different parameters, it is necessary to install devices with the appropriate capabilities.

Errors in the selection of AB are fraught with unpleasant consequences. If you connect a high-power protective device to a regular household circuit, it will not de-energize the circuit, even when the current significantly exceeds what the cable can withstand. The insulating layer will heat up and then begin to melt, but no shutdown will occur. The fact is that the current strength destructive to the cable will not exceed the AB rating, and the device will “consider” that emergency situation there wasn't. Only when the melted insulation causes a short circuit will the machine turn off, but by then a fire may already have started.

We present a table that shows the ratings of machines for various electrical networks.

If the device is designed for less power than what the line can withstand and which the connected devices have, the circuit will not be able to operate normally. When you turn on the equipment, the AV will constantly knock out, and ultimately, under the influence of high currents, it will fail due to “stuck” contacts.

Visually about the types of circuit breakers in the video:

Conclusion

The circuit breaker, the characteristics and types of which we reviewed in this article, is very important device, which protects the electrical line from damage by powerful currents. The operation of networks not protected by automatic circuit breakers is prohibited by the Electrical Installation Rules. The most important thing is to choose the right type of AV that is suitable for a specific network.

The main difference between these switching devices and all other similar devices is the complex combination of capabilities:

1. maintain rated loads in the system for a long time by reliably passing powerful flows of electricity through its contacts;

2. protect operating equipment from accidental malfunctions electrical diagram due to quick removal food from it.

Under normal equipment operating conditions, the operator can manually switch loads with circuit breakers, providing:

different power plans;

changing the network configuration;

removal of equipment from operation.

Emergency situations in electrical systems occur instantly and spontaneously. A person is not able to quickly react to their appearance and take measures to eliminate them. This function is assigned to automatic devices, built into the switch.

In the energy sector, it is common practice to divide electrical systems by type of current:

constant;

variable sinusoidal.

In addition, there is a classification of equipment according to voltage:

low voltage - less than a thousand volts;

high voltage - everything else.

For all types of these systems, their own circuit breakers are created, designed for repeated operation.

Chains AC

Based on the power of transmitted electricity, circuit breakers in alternating current circuits are conventionally divided into:

1. modular;

2. in a molded case;

3. power air.

Modular designs

The specific design in the form of small standard modules with a width that is a multiple of 17.5 mm determines their name and design with the possibility of installation on a Din rail.

The internal structure of one of these circuit breakers is shown in the picture. Its body is entirely made of durable dielectric material, eliminating .

The supply and output wires are connected to the upper and lower terminals, respectively. To manually control the state of the switch, a lever with two fixed positions is installed:

the top one is designed to supply current through a closed power contact;

the lower one ensures a break in the power supply circuit.

Each of these machines is designed for long-term operation at a certain value (In). If the load becomes greater, then the power contact breaks. For this purpose, two types of protection are placed inside the case:

1. thermal release;

2. current cut-off.

The principle of their operation makes it possible to explain the time-current characteristic, which expresses the dependence of the response time of the protection on the load current passing through it or an accident.

The graph presented in the picture is shown for one specific circuit breaker, when the cutoff operating zone is selected at 5÷10 times the rated current.

During the initial overload, a thermal release made of , which, with increased current, gradually heats up, bends and acts on the tripping mechanism not immediately, but with a certain time delay.

In this way, it allows small overloads associated with short-term connection of consumers to resolve themselves and eliminate unnecessary shutdowns. If the load provides critical heating of the wiring and insulation, then the power contact breaks.

When an emergency current occurs in the protected circuit, capable of burning the equipment with its energy, the electromagnetic coil comes into operation. With an impulse, due to the surge of the load that has arisen, it throws the core onto the disconnecting mechanism in order to instantly stop the over-the-top mode.

The graph shows that the higher the short circuit currents, the faster they are switched off by the electromagnetic release.

The household automatic PAR fuse works on the same principles.

When large currents break, an electric arc is created, the energy of which can burn out the contacts. To eliminate its effect, circuit breakers use an arc suppression chamber, which divides the arc discharge into small streams and extinguishes them due to cooling.

Cut-off ratio of modular structures

Electromagnetic releases are configured and selected to work with certain loads because when started they create different transient processes. For example, when turning on various lamps, a short-term surge of current due to the changing resistance of the filament can approach three times the nominal value.

Therefore, for the socket group of apartments and lighting circuits, it is customary to choose automatic switches with a time-current characteristic of type “B”. It is 3÷5 In.

Asynchronous motors, when spinning a rotor with a drive, cause large overload currents. For them, machines with characteristic “C” are selected, or - 5÷10 In. Due to the created reserve of time and current, they allow the engine to spin up and be guaranteed to reach operating mode without unnecessary shutdowns.

IN industrial production On machines and mechanisms there are loaded drives connected to motors, which create more increased overloads. For such purposes, automatic circuit breakers of characteristic “D” with a rating of 10÷20 In are used. They have proven themselves well when working in circuits with active-inductive loads.

In addition, machines have three more types of standard time-current characteristics that are used for special purposes:

1. “A” - for long wiring with an active load or protection of semiconductor devices with a value of 2÷3 In;

2. “K” - for pronounced inductive loads;

3. “Z” - for electronic devices.

IN technical documentation at different manufacturers The cut-off ratio for the last two types may be slightly different.

This class of devices is capable of switching higher currents than modular designs. Their load can reach values ​​up to 3.2 kiloamperes.

They are manufactured according to the same principles as modular designs, but, taking into account the increased requirements for carrying increased loads, they are made to have relatively small dimensions and high technical quality.

These machines are designed for safe work at industrial facilities. Based on the rated current, they are conventionally divided into three groups with the ability to switch loads up to 250, 1000 and 3200 amperes.

Design of their housing: three- or four-pole models.

Power air circuit breakers

They work in industrial installations and operate with very high load currents up to 6.3 kiloamperes.

These are the most complex devices for switching devices of low-voltage equipment. They are used to operate and protect electrical systems as input and output devices distribution installations increased capacity and for connecting generators, transformers, capacitors or powerful electric motors.

Schematic representation of them internal structure shown in the picture.

Here, a double break of the power contact is used and arc-extinguishing chambers with grilles are installed on each side of the shutdown.

The operating algorithm involves a switching coil, a closing spring, a spring charging motor drive and automatic elements. To control the flowing loads, a current transformer with a protective and measuring winding is built in.

Circuit breakers of high-voltage equipment are very complex technical devices and are manufactured strictly individually for each voltage class. They are usually used.

They are subject to the following requirements:

high reliability;

security;

speed;

ease of use;

relative noiselessness during operation;

optimal cost.

Loads that break during an emergency shutdown are accompanied by a very strong arc. To extinguish it they use various ways, including breaking the circuit in a special environment.

This switch includes:

contact system;

arc extinguishing device;

live parts;

insulated housing;

drive mechanism.

One of these switching devices is shown in the photograph.

For quality work circuits in such designs, in addition to the operating voltage, take into account:

the rated value of the load current for its reliable transmission in the on state;

maximum short-circuit current based on the effective value that the disconnecting mechanism can withstand;

permissible component of the aperiodic current at the moment of circuit break;

automatic re-closing capabilities and provision of two automatic reclosure cycles.

According to the methods of extinguishing the arc during shutdown, switches are classified into:

oil;

vacuum;

air;

SF6;

autogas;

electromagnetic;

autopneumatic.

For reliable and comfortable work they are equipped with a drive mechanism that can use one or more types of energy or combinations thereof:

charged spring;

lifted load;

compressed air pressure;

electromagnetic pulse from the solenoid.

Depending on the conditions of use, they can be created with the ability to operate under voltage from one to 750 kilovolts inclusive. Naturally, they have different designs. dimensions, automatic and remote control, setting up protections for safe operation.

Auxiliary systems of such circuit breakers can have a very complex branched structure and are located on additional panels in special technical buildings.

Chains DC

These networks also operate a huge number of circuit breakers with different capabilities.

Electrical equipment up to 1000 volts

Here, modern modular devices that can be mounted on a Din rail are being introduced en masse.

They successfully complement the classes of old machine guns such as , AE and other similar ones, which were fixed to the walls of shields with screw connections.

Modular DC designs have the same structure and operating principle as their AC counterparts. They can be performed in one or several blocks and are selected according to the load.

Electrical equipment above 1000 volts

High-voltage circuit breakers for direct current operate in electrolysis production plants, metallurgical industrial facilities, railway and urban electrified transport, and energy enterprises.

Basic technical requirements the operation of such devices corresponds to their alternating current counterparts.

Hybrid switch

Scientists from the Swedish-Swiss company ABB managed to develop a high-voltage DC switch that combines two power structures:

1. SF6;

2. vacuum.

It is called hybrid (HVDC) and uses the technology of sequential arc extinguishing in two environments at once: sulfur hexafluoride and vacuum. For this purpose, the following device has been assembled.

Voltage is supplied to the upper busbar of the hybrid vacuum circuit breaker, and voltage is removed from the lower busbar of the SF6 circuit breaker.

The power parts of both switching devices are connected in series and controlled by their own individual drives. In order for them to work simultaneously, a control device for synchronized coordinate operations was created, which transmits commands to the control mechanism with independent power supply via a fiber optic channel.

Through the use of high-precision technologies, the design developers were able to achieve consistency in the actions of the actuators of both drives, which fits into a time period of less than one microsecond.

The switch is controlled by a relay protection unit built into the power line through a repeater.

The hybrid circuit breaker has significantly improved the efficiency of composite SF6 and vacuum designs by exploiting their combined characteristics. At the same time, it was possible to realize advantages over other analogues:

1. the ability to reliably turn off short-circuit currents at high voltage;

2. the possibility of a small effort for switching power elements, which made it possible to significantly reduce the dimensions and. accordingly, the cost of equipment;

3. availability of compliance with various standards for the creation of structures operating as part of a separate circuit breaker or compact devices at one substation;

4. the ability to eliminate the consequences of rapidly increasing recovering stress;

5. the ability to form a base module to work with voltages up to 145 kilovolts and higher.

A distinctive feature of the design is the ability to break an electrical circuit in 5 milliseconds, which is almost impossible to achieve with power devices of other designs.

Hybrid switch device marked as number ten best developments per year according to version technology review MIT (Massachusetts Institute of Technology).

Other manufacturers of electrical equipment are also engaged in similar research. They also achieved certain results. But ABB is ahead of them in this matter. Its management believes that large losses occur during the transmission of alternating current electricity. They can be significantly reduced by using high-voltage direct voltage circuits.