Production automation is a process in the development of machine production, in which the functions of management and control, previously performed by a person, are transferred to instruments and automatic devices. The introduction of automation in production makes it possible to significantly increase labor productivity and the quality of products, and to reduce the proportion of workers employed in various areas of production.
Before the introduction of automation tools, the replacement of physical labor took place through the mechanization of the main and auxiliary operations of the production process. For a long time intellectual labor remained non-mechanized (manual). At present, the operations of physical and intellectual labor, amenable to formalization, are becoming the object of mechanization and automation.
Modern manufacturing systems that provide flexibility in automated manufacturing include:
· CNC machines that first appeared on the market back in 1955. Mass distribution began only with the use of microprocessors.
· Industrial robots, first introduced in 1962. Mass distribution is associated with the development of microelectronics.
· Robotic technological complex (RTK), which first appeared on the market in 1970-80s. Mass distribution began with the use of programmable control systems.
· Flexible production systems, characterized by a combination of technological units and robots, computer controlled, equipped with equipment for moving workpieces and changing tools.
· Automated warehouse systems (eng. Automated Storage and Retrieval Systems, AS / RS). Provides for the use of computer-controlled lifting and transporting devices that place products in a warehouse and retrieve them from there on command.
· Computer-based quality control systems (eng. Computer-aided Quality Control, CAQ) is a technical application of computers and computer-controlled machines for checking the quality of products.
· Computer-aided design system (eng. Computer-aided Design, CAD) is used by designers in the development of new products and technical and economic documentation.
· Planning and coordination of individual elements of the plan using a computer (eng. Computer-aided Planning, CAP). SAR- it is divided according to various characteristics and purposes, according to the state of approximately the same elements.
Computer (electronic computer)
State the main provisions of the technology of harvesting and washing operations. Compare cleaning and washing equipment and justify its choice. Evaluate the possibilities of designing a cleaning and washing station.
Washing works are often performed manually using a hose with a gun and a pump of low (0.3-0.4 MPa) or high (1.5-2.0 MPa) pressure or mechanically using washing installations. A progressive method is the mechanized and automatic washing of cars, automotive units and parts, which allows you to replace manual labor as much as possible and increase labor productivity with a high-quality wash.
So, let's consider the main existing types of car washes:
A hand wash is a traditional car wash performed by people. The machine is washed with water and car shampoo using sponges, brushes, rags, etc., that is, a contact wash.
The advantage of a manual car wash is that a person in the process of work sees which areas are more contaminated and need more thorough cleaning.
Cons: with such a wash there is a great risk of damaging the paintwork on the car body; and hand washing the car will take the longest amount of time.
A brush car wash is a contact wash in which people do not participate, it is carried out using special automatic installations. The process consists of several stages: first, the machine is sprayed with water under pressure, then with hot foam, then quickly rotating brushes are taken to clean the machine from dirt. The last step is applying a protective wax and drying the car.
The brush washer is suitable for stubborn dirt, which a contactless wash may not cope with. Brushes are made of synthetic filaments with rounded ends. Good quality brushes should not scratch the paintwork.
A non-contact car wash is a wash with active foams. This technology is used in conventional contactless car washes, where people wash using special devices, as well as in conveyor and gantry car washes. In the process of such washing, the main layer of dirt is washed off with a jet of water under high pressure, then active foam is applied by special equipment, under the action of which the remaining dirt falls off the body, and after a while the foam is also washed off with a stream of water under pressure. As a rule, such a wash ends with the application of a protective polish, which will give an attractive shine and protect against rapid pollution and harmful effects of the environment.
A non-contact car wash or pressure washer causes the least damage to the body paintwork.
Dry washing is washing with the help of a special shampoo-polish. Car enthusiasts carry out such a wash with their own hands. No water is required for such a wash. Manufacturers of shampoos for dry washing claim that the silicone oil and surfactants included in the shampoo soften, saturate and envelop dirt particles, ensuring the integrity of the paintwork during this type of washing. Dry washing will provide shine and protection of the body from negative environmental factors for some time.
The disadvantage of such a wash is the impossibility or inconvenience of processing hard-to-reach places of the car. Therefore, this type of washing is recommended to be used in the intervals between water washes to maintain the cleanliness and tidiness of the car.
There are two types of automatic car washes:
Conveyor type (or tunnel). This is when the car is slowly transported by a conveyor through several arches with various cleaning and rinsing functions (for example: pre-wash, wheel wash, underbody wash, high pressure wash, drying).
The biggest plus of such car washes is the speed of work and high productivity. All arches work at the same time, so the driver does not have to wait for the previous car to go through all the procedures.
Portal type. With such a wash, the car is stationary, and the portal (wash arch) moves relative to it.
The disadvantage compared to a conveyor car wash is that a gantry car wash is not able to quickly accept such a number of cars.
State the main provisions of the technology of diagnostic work. Compare diagnostic equipment and justify its choice. Evaluate the possibilities of designing a post of diagnostic work
1.1. The Guide sets out the main provisions for the organization of diagnostics of the technical condition of the rolling stock of road transport in cars, trucks, buses and mixed motor transport enterprises (ATP) of various capacities.
1.2. Technical diagnostics is a part of the technological process of maintenance (MOT) and repair (R) of cars, the main method of control and control and adjustment work. In the ATP technical service management system, diagnostics is an information subsystem.
1.3. The basis for the organization of car diagnostics is the planned preventive system of maintenance and repair, which is in force in the USSR, set forth in the "Regulations on the maintenance and repair of rolling stock of road transport".
1.4. In the conditions of ATP, technical diagnostics should solve the following tasks:
Clarification of failures and malfunctions revealed during operation;
Identification of vehicles, the technical condition of which does not meet the requirements of traffic safety and environmental protection;
Identification of faults before maintenance, for the elimination of which labor-intensive repair or adjustment work is required in the current repair area (TR);
Clarification of the nature and causes of failures or malfunctions identified in the course of maintenance and repair;
Predicting the failure-free operation of units, systems and the vehicle as a whole within the inter-inspection mileage;
Issuance of information on the technical condition of the rolling stock for planning, preparation and management of the production of TO and TR;
Quality control of the performed maintenance and repair works.
Vehicle diagnostics technology contains: list and sequence of operations, repeatability factors, labor intensity, work category, used tools and equipment, technical conditions for the performance of work.
3.2. Depending on the shift program and the type of rolling stock, diagnostic work is carried out at separate posts (dead-end or travel) or posts located in a line.
3.3. The technology is compiled separately for the types of diagnostics D-1, D-2 and others.
3.4. For specialized repair, adjustment and diagnostic posts, the DR technology is compiled for individual diagnosed units, systems and types of work (braking system, steering, wheel alignment angles, wheel balancing, headlight installation, etc.).
3.5. When developing diagnostics technology, one should be guided by the established lists of diagnostic operations by type of diagnostics (Appendices 1, 2), which are part of the control works given in the current Regulation on the maintenance and repair of rolling stock of road transport, as well as the list of diagnostic signs (parameters) and their limit values (Appendix 5).
3.6. A typical diagnostics technology should contain preparatory work performed before diagnosing, the actual diagnostics, adjustment and final work performed based on the results of diagnostics.
3.7. The technology for diagnosing D-1 and D-2 is compiled taking into account the specific conditions of the ATP.
3.8. Diagnostics at posts (lines) in the amount of D-1 and D-2 are performed by diagnostic operators or diagnostic mechanics. To help them, drivers-ferrymen are attached, who, in addition to driving cars during the diagnosis process, are engaged in setting cars to diagnostic posts, removing them from them, distilling them into the appropriate area (storage, waiting, maintenance and repairs), as well as preparatory and some adjustment work ... In an ATP, where there are no regular ferry drivers, this work is entrusted to the drivers of diagnosed vehicles or column mechanics who have the right to drive.
Control and diagnostic (D) and adjustment operations at the maintenance and repair posts are performed by repair workers.
3.9. At posts (lines) D-1 and D-2, repair work related to the elimination of identified malfunctions, as a rule, is not performed. The exception is adjustment work, the implementation of which in the process of diagnostics is provided for by the technological process.
3.10. Performing diagnostic operations before maintenance and current repairs is mandatory, regardless of the availability of diagnostic tools. In the absence of the latter in the ATP, the control and diagnostic operations provided for by this "Manual ..." are performed by the diagnostic mechanic subjectively in order to identify the necessary volumes of current repairs performed before maintenance.
At the same time, for a long time, the automatic transmission was installed on cars of the middle class and premium segment, but later the unit became widespread.
Due to the huge popularity, as well as taking into account the constant tightening of norms and standards regarding fuel efficiency and environmental friendliness, manufacturers are constantly improving automatic transmissions, offering innovative solutions, etc.
As a result, today it is possible to distinguish at least three main types of "automatic machines", which are very different from each other in design and principles of operation, but each of them is called an automatic transmission. Next, we will talk about what automatic transmissions are, as well as what features this or that unit has.
If we talk about the advantages, the hydroautomatic device has a fairly large resource (in some cases up to 500 thousand km), and also provides a good level of comfort while driving.
As for the main disadvantages, such a box is expensive to repair, requires regular maintenance, is demanding on the quality of transmission oil, is afraid of prolonged loads and severe operating conditions, and is not highly economical. We also note that the losses in the gas turbine engine lead to the fact that the efficiency of hydromechanical machines decreases in comparison with analogs. As a result, acceleration dynamics suffers.
- (CVT transmission) is a separate type of automatic transmission, which, for a number of reasons, is not as widespread as a hydromechanical automatic transmission.
Such a transmission, like an automatic transmission, has a torque converter for transmitting torque from the internal combustion engine, but the transmission itself is very different. In short, there are two pulleys mounted on the variator shafts. These pulleys are connected to each other by a belt or chain. Depending on the load and speed, the drive and driven pulleys change their diameter, as a result of which the torque on the wheels also changes. And it happens very smoothly.
Taking into account the fact that there are no usual fixed speeds (steps), thanks to this feature, the CVT variator is called a continuously variable transmission (flexible change in the gear ratio). This type of automatic machines differs from analogs in the maximum smoothness of the course, since there is practically no gear change. The engine speed is also kept at the same level, without a sharp increase and decrease.
As in the case of the automatic transmission, additional modes can be implemented (winter, economical, sports, as well as Tiptronic with imitation of manual gear shifting). When driving a car with a variator, drivers note the complete absence of tangible shocks, vibrations, etc. You should also highlight good acceleration dynamics and fuel efficiency.
However, there are also downsides. First of all, it does not differ in a large resource, it is extremely difficult and expensive to repair, it is demanding on the quality and level of oil. This means that such a box is not paired with powerful engines; during operation, it is highly discouraged to load the transmission.
- (robot box or automatic transmission robot) is another type of automatic transmission, which for a number of reasons became really widespread about 20 years ago.
It is noteworthy that this unit was developed for a long time and in fact is a manual transmission with one clutch, in which, at the same time, the control of the clutch operation, as well as the selection and switching on / off of the desired gear, is automated.
In simple words, an automatic transmission robot is an automated (robotic) mechanics. Such a box is notable for its low production cost (which significantly reduces the cost of the entire car), allows for significant fuel savings (by analogy with mechanics), as well as dynamic acceleration.
If we consider the disadvantages, then, first of all, a noticeable decrease in comfort should be highlighted in comparison with automatic transmissions and variators. In simple words, the clutch remains exactly the same as on the manual transmission, while the robot does not always timely, quickly and accurately select the desired gear, cannot smoothly control the clutch, etc.
As a result, at the moment of shifting, jerks, jerks, etc. are felt, the robot tightens gear changes, does not always accurately select gears in accordance with constantly changing conditions while driving.
Also, actuators (servomechanisms, actuators) on robotic gearboxes of manual transmissions quickly fail, high-quality repairs are often impossible, that is, a complete replacement is needed. At the same time, it is important to understand that such mechanisms are quite expensive.
- (for example, DSG or Powershift) can be considered a more technologically advanced and perfect version of a conventional box - a robot. At the same time, units of this type are devoid of many of the disadvantages of their predecessors.
On the one hand, the design remained similar to mechanics, however, the engineers conditionally placed two such mechanical boxes at once in one case. One box has even gears, the other has odd gears, and a separate clutch is provided for each.
In short, while the car is moving, for example, in one gear, the next one after it is also selected and engaged, but not engaged, since the clutch is disengaged. At the moment of gear shifting, the working clutch is quickly disengaged, then the second is instantly connected. Gear changes happen so quickly that the driver hardly feels it.
At the same time, the control of such a robot is more reminiscent of the automatic transmission control scheme (there is a valve body called Mechatronic, a larger amount of transmission oil is needed, etc.). At the same time, a large number of servos are also present (by analogy with a single-disk robot, which has one clutch).
Among the advantages, one can single out high fuel efficiency and excellent acceleration dynamics, a high level of comfort, as well as the better ability of the box to cope with high loads compared to automatic transmissions and variators.
At the same time, a preselective gearbox is complex and expensive to manufacture, has a noticeably smaller resource, in practice it requires intervention earlier than an automatic transmission or a variator. With regard to repairs, robots of this type require exclusively qualified maintenance; often sets of expensive special equipment are also required for carrying out many procedures (for example,).
How to distinguish a robot from a machine or variator
The fact is that manufacturers strive to simplify as much as possible the entire process of interaction between the driver and the box. For this reason, for example, a robot can have the same selector and modes (P-R-N-D) as a variator or automatic transmission.
As for the sensations when driving (provided that the transmission and the car itself are completely in good condition), you can pay attention to the following:
- AT - often stands for hydromechanical automatic;
- CVT - variator transmission;
- AMT - robotic box with one clutch;
You can also ask a question at specialized auto forums, study technical literature separately, etc.
Let's summarize
As you can see, each automatic transmission has both strengths and weaknesses. Also, taking into account the diversity, you may be faced with the fact that it is difficult to immediately determine which automatic transmission is on a particular car.
Finally, we note that during operation it is important to separately take into account certain features of a particular machine, depending on the type of transmission and the type of automatic transmission. You also need to strictly follow the rules for servicing an automatic transmission, which allows you to increase the resource of the unit.
Read also
Topic: what types are divided into electric machines, their types and classification.
A circuit breaker is an electrical device, the main purpose of which is to switch its operating state when a certain situation occurs. Electric machines combine two devices in themselves, this is a conventional switch and a magnetic (or thermal) release, the task of which is to timely break the electrical circuit in case of exceeding the threshold value of the current strength. Circuit breakers, like all electrical devices, also have various varieties, which divides them into certain types. Let's take a look at the main classifications of circuit breakers.
1 "Classification of machines by the number of poles:
A) single-pole machines
b) single-pole circuit breakers with neutral
c) two-pole machines
d) three-pole machines
e) three-pole circuit breakers with neutral
f) four-pole machines
2 "Classification of automatic machines by type of release.
The design of various types of circuit breakers usually includes 2 main types of releases (breakers) - electromagnetic and thermal. Magnetic ones are used for electrical protection against short circuits, and thermal breakers are intended mainly for protecting electrical circuits at a certain overload current.
3 "Classification of automatic devices for trip current: B, C, D, (A, K, Z)
GOST R 50345-99, according to the instantaneous release current, the machines are divided into the following types:
A) type "B" - over 3 In up to 5 In inclusive (In is the rated current)
b) type "C" - over 5 In up to 10 In inclusive
B) type "D" - over 10 In up to 20 In inclusive
Manufacturers of automatic machines in Europe have a slightly different classification. For example, they have an additional type "A" (over 2 In to 3 In). Some manufacturers of circuit breakers also have additional tripping curves (ABB has circuit breakers with K and Z curves).
4 "Classification of machines by the type of current in the circuit: constant, variable, both.
Rated electric currents for the main circuits of the release are selected from: 6.3; ten; 16; twenty; 25; 32; 40; 63; 100; 160; 250; 400; 630; 1000; 1600; 2500; 4000; 6300 A. Also, in addition to produce machines for rated currents of the main electrical circuits of machines: 1500; 3000; 3200 A.
5 "Classification by the presence of current limitation:
a) current-limiting
b) non-current limiting
6 "Classification of automatic machines by type of release:
A) with overcurrent release
b) with a shunt release
c) with undervoltage release or zero voltage release
7 "Classification of machines according to the time delay characteristic:
A) without time delay
b) with a time delay independent of the current
c) with a time delay, inversely dependent on current
d) with a combination of the specified characteristics
8 "Classification by the presence of free contacts: with and without contacts.
9 "Classification of machines according to the method of connecting external wires:
A) with rear connection
b) with front connection
c) with combined connection
d) with universal connection (both front and rear).
10 "Classification by drive type: with manual, motor and spring.
P.S. Everything has its own varieties. After all, if there was only one thing in its single copy, it would be at least just boring and too limited! So the diversity and good that in it you can choose exactly what the maximum meets your needs.
In the event of an emergency in the electrical network - short circuit, fire or electric shock to a person, it must be immediately de-energized. Previously, this function was performed by fuses. Their main disadvantage is that they disconnect only one, and most often only phase, line.
And according to today's rules for the operation of electrical installations, a complete break is required. In addition, they do not work quickly enough and must be replaced after triggering. Automatic fuses and switches are devoid of these disadvantages.
The family of electrical devices, which in everyday use are often called "electric machine", is very diverse. If such a comparison is allowed, it consists of several clans, differing in the type of impact to which they react, as well as in design.
Depending on this, they are used to protect the entire electrical network as a whole, individual circuits and devices, or a person. There is also an intra-clan division. For example, in terms of response speed.
Types of circuit breakers by type of exposure:
- Overcurrent (short circuit) and heating tripping. The most common type. They are used to protect the entire power supply circuit (input automatic devices) or individual devices.
- Differential current response. These are the so-called RCDs - residual current devices used to prevent electric shock to a person.
- Thermal relays. They are used in electric drives to protect electric motors from overloads.
Differences in design:
- AP series. The so-called apeshki are large black boxes made of electrical plastic with two buttons: ON (white) and OFF (red). They react to heat and overcurrents. Usually used in three-phase networks to protect individual devices. Reliable massive construction, considered obsolete.
- VA series. A modern small-sized device with a horizontal on / off lever.
- Automatic fuses. Replaced the so-called Edison E14 screw cap plugs. Also outdated, but still widely used in household electrical networks, the design.
Depending on the number of connection points, which are called poles, the switches are one-, two-, three- and four-pole.
Single-pole switches only one line, usually phase. They are used in lightly loaded electrical circuits. For example, lighting. Their second name is "modular circuit breakers", since they are usually assembled in a package (several on one DIN rail) and placed in a distribution board, adjacent to a common zero bus. They also include automatic fuses, the input of which is the central contact, and the output is a threaded ring.
Two-pole are used in single-phase networks to protect the entire electrical circuit, then they are called input, or one device.
Three- and four-pole devices are used to work in three-phase networks, in which there can be three (in the case of a solidly grounded neutral) or four conductors.
Circuit breaker device
The design principle of switches that react to overcurrents and overheating is the same as for devices such as AP, VA or automatic fuses. BA type switches have screw terminals. A movable contact is connected to the input, which is connected to the control lever by a system of levers and springs.
In the on state, it has an electrical contact with an electromagnetic release - a solenoid with a moving core-rod. The conductor at its outlet is connected to another control element - a bimetallic plate abutting against the stem. An additional element of the device is an arc-extinguishing chamber - a package of plates made of electrical fiberboard.
The release is designed to trip when a current of a certain rating flows through its coil. When this value is reached, the solenoid pushes the stem and opens the contact. Please note that the bimetal plate is connected to the output terminal. Therefore, there is a significant difference in how to install the circuit breaker. When turned upside down, it stops responding to short circuits due to the additional resistance of the plate.
Residual current circuit breakers
They are called RCDs - residual current devices. Outwardly, they are very similar to VA machines, differing only in the "Test" button. Fundamental differences in the device of the electromagnetic release. It is built on the basis of a differential transformer.
Its primary winding is composed of two coils to which the phase and neutral wires are connected. The secondary winding is connected by a solenoid. In the normal state, the currents in the phase and neutral conductors are equal in magnitude, but opposite in phase. They compensate each other, and no electromagnetic field is induced in the primary winding.
With a partial breakdown of the insulation and the connection of the phase line with the grounding circuit, the balance is disturbed, a magnetic flux arises in the primary winding, which generates an electric current in the secondary. The solenoid is triggered and opens the contact.
This happens if, for example, a person takes an electrical appliance with his hand, the body of which is shorted to a phase. These devices do not protect either from short circuit or overheating, therefore they are installed in series with VA machines. And always after them. Read about the correct connection.
Differential switches
They are also called residual current circuit breakers - the abbreviation RCBO. They combine an automatic VA and an RCD. Their use simplifies the electrical circuit and its installation - instead of two devices, one can be supplied.
It is possible to distinguish RCBOs from RCDs by the schematic image on the front panel, which is not always possible due to insufficient technical literacy, or by the letter in front of the nominal figure and its value. More on this.
The residual current device can be written, for example, I n 16A and I ∆n 10 mA. The first value is the rated current of the circuit in which the device can operate. Note that there is no letter in front of it. The second is the operating current, it never exceeds a unit of amperes. RCBO is marked differently: C16 10 mA. Letter C is a time-current characteristic.
Time-current characteristics of circuit breakers
Depending on the design of the solenoid of the magnetic release, the circuit breaker can trip at different speeds. This is called the time-current characteristic. The main ones are:
- A - the fastest response. Required to protect semiconductor circuits sensitive to electricity quality. The device can only work in tandem with a compensating-type stabilizer. It is better not to use at home, since the quality standards for household networks are low, it will constantly work.
- B - increased sensitivity, but reduced response time. Can be used to protect power supply circuits in local area networks.
- C is the most common type of appliance used in everyday life. Satisfactory sensitivity and average response speed.
- B - industrial version with reduced sensitivity. It is used in networks with large amplitudes of voltage drops. For example, connected to electric transport traction substations.
Circuit breakers are an important element of the electrical circuit. Operation of electrical installations without them can lead to a man-made disaster of a local nature and endangers the life of the maintenance personnel.
Circuit breakers are devices whose task is to protect an electric line from the effects of a 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. With a short circuit, the current increases many times over 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.
Circuit breakers: classification and differences
In addition to residual current circuit breakers, which are not used individually, there are 3 types of circuit breakers. They work with loads of different sizes and differ in their design. These include:
- Modular AB. These devices are installed in household networks in which currents of negligible magnitude flow. They usually have 1 or 2 poles and a width in multiples of 1.75 cm.
- Cast 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 be 3 or 4 poles and can handle currents up to 6.3 kA. They are used in electrical circuits with high power installations.
There is another type of circuit breakers for power grid protection - differential. We do not consider them separately, since such devices are ordinary circuit breakers, which include an RCD.
Release types
The releases are the main working components of AB. Their task is to break the circuit when the permissible current value is exceeded, thereby stopping the supply of electricity to it. There are two main types of these devices, differing from each other in terms of the release principle:
- Electromagnetic.
- Thermal.
Electromagnetic-type releases provide almost instantaneous operation of the circuit breaker and de-energize the circuit section when an overcurrent short circuit 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 that exceeds the rated value of the protective device passes through the machine, the plate begins to heat up and, bending to the side, touches the disconnecting element, which is triggered and de-energizes the circuit. The tripping time of the thermal release depends on the value of the overload current passing through the plate.
Some modern devices are equipped as a supplement with undervoltage (zero) releases. They perform the function of switching off the AB when the voltage falls below the limit value corresponding to the technical data of the device. There are also distance releases, with which you can not only turn off, but also turn on AB, even without going to the switchboard.
The presence of these options significantly increases the cost of the device.
Number of poles
As already mentioned, the network circuit breaker has poles - from one to four.
It is not difficult to choose a device for a circuit according to their number, it is enough just to know where different types of AB are used:
- Single-pole networks are installed to protect lines that include sockets and lighting fixtures. They are mounted on a phase conductor without capturing a neutral conductor.
- The two-pole must be included in the circuit to which household appliances with a sufficiently high power are connected (boilers, washing machines, electric stoves).
- Three-pole networks are installed in semi-industrial scale networks, to which devices such as borehole pumps or equipment of a car repair shop can be connected.
- Four-pole AB allow you to protect electrical wiring with four cables from short-circuit and overloads.
The use of machines of different polarity is in the following video:
Circuit breaker characteristics
There is another classification of machines - according to their characteristics. This indicator indicates the degree of sensitivity of the protective device to exceeding the value of 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 AB work instantly, while others will take a certain amount of 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, protecting with their help circuits in which high-precision equipment is included.
- B. These breakers operate on rising current with a slight delay. Usually they are included in the line with expensive household appliances (LCD TVs, computers, and others).
- C. These devices are the most common in household networks. Their disconnection does not occur immediately after an increase in the current strength, but after a while, which makes it possible to normalize it with a slight drop.
- D. The sensitivity of these devices to increasing current is the lowest of all the listed types. They are most often installed in shields at the approach of the line to the building. They provide a safety net for the apartment 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 highest current, which means that it is he who can provide the maximum circuit protection. Based on this logic, an air-type machine can be connected to any network, and all problems will be solved. However, this is not at all the case.
To protect circuits with different parameters, it is necessary to install devices with appropriate capabilities.
Mistakes in the selection of AB are fraught with unpleasant consequences. If you connect a protective device designed for high power to a regular household circuit, then it will not de-energize the circuit, even when the current value significantly exceeds that that the cable can withstand. The insulating layer will heat up, then start to melt, but the shutdown will not occur. The fact is that the current strength, destructive for the cable, will not exceed the nominal AB, and the device will "count" that there was no emergency. Only when the molten insulation causes a short circuit will the machine turn off, but by that time a fire may have already begun.
Here is a table showing the ratings of the machines for various power grids.
If the device is designed for less power than that which the line can withstand and which the connected devices have, the circuit will not be able to work normally. When the equipment is turned on, the AB will constantly knock out, and ultimately, under the influence of high currents, it will fail due to "stuck" contacts.
Clearly about the types of circuit breakers in the video:
Conclusion
The circuit breaker, the characteristics and types of which we have considered in this article, is a very important device that protects an electrical line from damage by high currents. Operation of networks not protected by machines is prohibited by the Electrical Installation Rules. The most important thing is to choose the right type of AB, which is suitable for a particular network.