The main types of manufactured circuit breakers. What are the types and types of circuit breakers in electrical networks
Circuit breakers are devices that are responsible for protecting an electrical circuit from damage associated with the effect of a large current on it. Too strong a flow of electrons can damage household appliances, as well as cause overheating of the cable, followed by melting and ignition of the insulation. If the line is not de-energized in time, it can lead to a fire, Therefore, in accordance with the requirements of the PUE (Electrical Installation Rules), the operation of a network in which no electrical circuit breakers are installed is prohibited. AB have several parameters, one of which is the time-current characteristic of the automatic protective switch. In this article, we will explain how category A, B, C, D circuit breakers differ and which networks they are used to protect.
Features of the operation of circuit breakers
Whatever class the circuit breaker belongs to, its main task is always the same - to quickly detect the occurrence of excessive current, and to de-energize the network before the cable and devices connected to the line are damaged.
Currents that can pose a danger to the network are divided into two types:
- Overload currents. Their appearance most often occurs due to the inclusion of devices in the network, the total power of which exceeds that that the line can withstand. Another cause of overload is a malfunction of one or more devices.
- Overcurrents caused by short circuit. A short circuit occurs when the phase and neutral conductors are connected together. They are normally connected to the load separately.
The device and principle of operation of the circuit breaker - in the video:
Overload currents
Their value most often slightly exceeds the rating of the machine, therefore, the passage of such an electric current through the circuit, if it has not lasted too long, does not cause damage to the line. In this regard, instantaneous de-energization is not required in this case; moreover, often the magnitude of the electron flux quickly returns to normal. Each AB is designed for a certain excess of the strength of the electric current at which it is triggered.
The tripping time of the protective circuit breaker depends on the magnitude of the overload: with a slight excess of the norm, it can take an hour or more, and with a significant excess, it can take several seconds.
A thermal release is responsible for turning off the power under the influence of a powerful load, the basis of which is a bimetallic plate.
This element heats up under the influence of a powerful current, becomes plastic, bends and triggers the machine.
Short circuit currents
The flow of electrons caused by a short circuit is much higher than the rating of the protection device, as a result of which the latter is immediately triggered, turning off the power. An electromagnetic release, which is a solenoid with a core, is responsible for detecting a short circuit and an immediate reaction of the device. The latter, under the influence of an overcurrent, instantly acts on the circuit breaker, causing it to trip. This process takes a split second.
However, there is one caveat. Sometimes the overload current can also be very high, but this is not caused by a short circuit. How is the apparatus supposed to distinguish between the two?
In the video about the selectivity of circuit breakers:
Here we smoothly move on to the main issue that our material is devoted to. There are, as we have already said, several classes of AB, differing in time-current characteristics. The most common of these, which are used in household electrical networks, are devices of classes B, C and D. Circuit breakers belonging to category A are much less common. They are the most sensitive and are used to protect high-precision devices.
These devices differ from each other in instantaneous tripping current. Its value is determined by the multiplicity of the current passing through the circuit to the rating of the machine.
Tripping characteristics of protective circuit breakers
The AB class, determined by this parameter, is indicated by a Latin letter and is affixed to the body of the machine in front of the number corresponding to the rated current.
In accordance with the classification established by the PUE, circuit breakers are divided into several categories.
Automatic machines of the MA type
A distinctive feature of such devices is the absence of a thermal release in them. Devices of this class are installed in the connection circuits of electric motors and other powerful units.
Overload protection in such lines is provided by an overcurrent relay, the circuit breaker only protects the network from damage as a result of short-circuit overcurrents.
Class A devices
Automata type A, as has been said, have the highest sensitivity. The thermal release in devices with time-current characteristic A most often trips when the current exceeds the nominal AB by 30%.
The electromagnetic tripping coil de-energizes the network for about 0.05 seconds if the electric current in the circuit exceeds the rated one by 100%. If, for any reason, after doubling the strength of the electron flow, the electromagnetic solenoid does not work, the bimetallic release cuts off the power for 20-30 seconds.
The machines with the time-current characteristic A are included in the lines, during the operation of which even short-term overloads are unacceptable. These include circuits with semiconductor elements included in them.
Class B protective devices
Devices of category B have less sensitivity than those of type A. The electromagnetic release in them trips when the rated current is exceeded by 200%, and the trip time is 0.015 sec. The actuation of the bimetallic plate in the breaker with characteristic B with a similar excess of the AB rating takes 4-5 seconds.
Equipment of this type is intended for installation in lines that include sockets, lighting devices and in other circuits where there is no starting increase in electric current or has a minimum value.
Category C machines
Type C devices are most common in home networks. Their overload capacity is even higher than those previously described. In order for the solenoid of electromagnetic release installed in such a device to operate, it is necessary that the flow of electrons passing through it exceeds the nominal value by 5 times. The thermal release when the protection device is exceeded fivefold occurs after 1.5 seconds.
The installation of circuit breakers with a time-current characteristic C, as we said, is usually carried out in household networks. They do an excellent job of playing the role of input devices to protect the general network, while category B devices are well suited for individual branches to which outlet groups and lighting fixtures are connected.
This will allow observing the selectivity of the circuit breakers (selectivity), and with a short circuit in one of the branches, the entire house will not be de-energized.
Category D circuit breakers
These devices have the highest overload capacity. For the operation of an electromagnetic coil installed in a device of this type, it is necessary that the electric current rating of the circuit breaker is at least 10 times exceeded.
In this case, the thermal release is triggered after 0.4 seconds.
Devices with characteristic D are most often used in general networks of buildings and structures, where they play a safety role. They are triggered if there was no timely power outage by circuit breakers in separate rooms. They are also installed in circuits with high starting currents, to which, for example, electric motors are connected.
Category K and Z protective devices
Automata of these types are much less common than those described above. Type K devices have a wide variation in the values of current required for electromagnetic tripping. So, for an alternating current circuit, this indicator should exceed the nominal 12 times, and for a constant one - 18 times. The electromagnetic solenoid is triggered in no more than 0.02 seconds. The thermal release in such equipment can operate when the rated current is exceeded by only 5%.
These features are responsible for the use of devices of type K in circuits with an exclusively inductive load.
Devices of type Z also have different operating currents of the electromagnetic tripping solenoid, but the spread is not as great as in AB category K. 4.5 times the nominal.
Devices with characteristic Z are used only in lines to which electronic devices are connected.
Conclusion
In this article, we examined the time-current characteristics of protective circuit breakers, the classification of these devices in accordance with the PUE, and also figured out in which circuits devices of various categories are installed. The information obtained will help you determine which protective equipment should be used on the network, based on what devices are connected to it.
The main difference between these switching devices from all other similar devices is the complex combination of capabilities:
1. to maintain the rated load in the system for a long time due to the reliable transmission of powerful flows of electricity through its contacts;
2. to protect the operating equipment from accidental faults in the electrical circuit by quickly removing power from it.
Under normal operating conditions of the equipment, the operator can manually switch the loads with the circuit breakers, providing:
different power schemes;
changing the network configuration;
withdrawal of equipment from work.
Emergency situations in electrical systems occur instantly and spontaneously. A person is not able to quickly respond to their appearance and take measures to eliminate them. This function is assigned to automatic devices built into the circuit breaker.
In the power industry, the division of electrical systems by type of current is accepted:
constant;
alternating sinusoidal.
In addition, there is a classification of equipment according to the magnitude of the voltage for:
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.
AC circuits
According to the power of the transmitted electricity, automatic switches in alternating current circuits are conventionally divided into:
1.modular;
2. in a molded case;
3. power air.
Modular designs
A specific design in the form of small standard modules with a width of multiples of 17.5 mm determines their name and design with the possibility of mounting on a Din-rail.
The internal structure of one of these circuit breakers is shown in the picture. Its body is completely made of durable dielectric material, excluding.
The supply and outgoing wires are connected to the upper and lower terminal clamp, respectively. For manual control of the state of the switch, a lever with two fixed positions is installed:
the upper one is designed to supply current through a closed power contact;
bottom - provides 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 larger, then the power contact breaks. For this, two types of protections are placed inside the case:
1. thermal release;
2.current cutoff.
The principle of their operation makes it possible to explain the time-current characteristic, which expresses the dependence of the protection operation time on the load current or failure passing through it.
The graph shown in the picture is for one specific circuit breaker, when the cut-off operating zone is selected at 5 ÷ 10 times the rated current.
At the initial overload, a thermal release is made, which, with an increased current, gradually heats up, bends and acts on the disconnecting mechanism not immediately, but with a certain time delay.
In this way, it allows small overloads associated with short-term connection of consumers to self-eliminate and eliminate unnecessary shutdowns. If the load provides critical heating of the wiring and insulation, then the power contact breaks.
When an emergency current arises in the protected circuit, capable of burning equipment with its energy, then an 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 out-of-limit mode.
The graph shows that the higher the short-circuit currents, the faster they are disconnected by the electromagnetic release.
The household automatic steam fuse works according to the same principles.
When large currents are broken, an electric arc is created, the energy of which can burn out the contacts. To eliminate its effect, an arc-extinguishing chamber is used in circuit breakers, which divides the arc discharge into small flows and extinguishes them due to cooling.
Multiplicity of cutoffs of modular structures
Electromagnetic releases are tuned and matched to work with certain loads because they create different transients when they start. For example, during the switching on of various luminaires, the short-term inrush current due to the changing resistance of the filament can approach three krats of 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 the "B" type. It is 3 ÷ 5 In.
Asynchronous motors, when spinning a rotor with a drive, cause higher overload currents. For them, select machines with the characteristic "C", or - 5 ÷ 10 In. Due to the created margin in time and current, they allow the engine to spin up and it is guaranteed to enter the operating mode without unnecessary shutdowns.
In industrial production, on machine tools and mechanisms, there are loaded drives connected to motors, which create more increased overloads. For such purposes, automatic switches 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, the 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 the technical documentation from different manufacturers, the cutoff rate for the last two types may differ slightly.
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 structures, but taking into account the increased requirements for the transmission of the increased load, they are trying to give them relatively small dimensions and high technical quality.
These machines are designed for safe operation in industrial facilities. By the value of the rated current, they are conventionally divided into three groups with the ability to switch loads up to 250, 1000 and 3200 amperes.
Constructive design of their case: three- or four-pole models.
Power air switches
They work in industrial installations and handle very heavy currents up to 6.3 kiloamperes.
These are the most complex devices for switching devices of low-voltage equipment. They are used for the operation and protection of electrical systems as input and output devices for high power distribution plants and for connecting generators, transformers, capacitors or powerful electric motors.
A schematic representation of their internal structure is shown in the picture.
Here, a double break of the power contact is already used and arc extinguishing chambers are installed with gratings on each side of the disconnection.
The operation algorithm involves the closing coil, the closing spring, the motor-drive of the spring charging and the automation elements. To monitor the flowing loads, a current transformer with a protective and measuring winding is integrated.
Circuit breakers for high-voltage equipment are very complex technical devices and are made strictly individually for each voltage class. They are usually used.
Requirements are imposed on them:
high reliability;
security;
performance;
ease of use;
relative noiselessness during operation;
optimal cost.
Loads that break during a fault trip are accompanied by a very strong arc. Various methods are used to extinguish it, 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 high-quality operation of the circuit in such structures, 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 at rms value that the tripping mechanism can withstand;
the permissible component of the aperiodic current at the moment of circuit rupture;
automatic reclosing capabilities and two AR cycles.
According to the methods of extinguishing the arc during tripping, the switches are classified into:
oil;
vacuum;
air;
SF6 gas;
autogas;
electromagnetic;
auto-pneumatic.
For reliable and convenient operation, they are equipped with a drive mechanism that can use one or several types of energies or their combinations:
cocked 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 a different design. dimensions, automatic and remote control capabilities, protection settings for safe operation.
The auxiliary systems of such circuit breakers can have a very complex branched structure and be located on additional panels in special technical buildings.
DC circuits
A huge number of circuit breakers with different capabilities also operate in these networks.
Electrical equipment up to 1000 volts
Modern modular devices with the ability to mount on a Din-rail are massively introduced here.
They successfully complement the classes of old automatic machines such as, AE and other similar ones, which were fixed on the walls of the panels with screw connections.
DC modular designs have the same structure and principle of operation as their alternating voltage counterparts. They can be performed by one or several units and are selected according to the load.
Electrical equipment above 1000 volts
High-voltage circuit breakers for direct current are used in electrolysis plants, metallurgical industrial facilities, railway and urban electrified transport, and energy enterprises.
The main technical requirements for the operation of such devices correspond to their alternating current counterparts.
Hybrid breaker
Scientists from the Swedish-Swiss company ABB managed to develop a high-voltage DC circuit breaker that combines two power structures in its device:
1. SF6 gas;
2. vacuum.
It was named hybrid (HVDC) and uses the technology of sequential arc quenching in two environments at once: sulfur hexafluoride and vacuum. For this, the following device is assembled.
Voltage is applied 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 individual drives. In order for them to work simultaneously, a synchronized coordinate operations control device was created, which transmits commands to the control mechanism with independent power supply via a fiber-optic channel.
Due to the use of high-precision technologies, the designers managed to achieve the coordination of actions of the actuators of both drives, which fits into a time interval of less than one microsecond.
The circuit breaker is controlled from a relay protection unit built into the power line through a repeater.
The hybrid circuit breaker has made it possible to significantly increase the efficiency of composite SF6 and vacuum structures through the use of their combined characteristics. At the same time, it was possible to realize the advantages over other analogues:
1.the ability to reliably disconnect short-circuit currents at high voltage;
2. the possibility of a small effort to carry out the switching of the power elements, which made it possible to significantly reduce the dimensions and. accordingly, the cost of equipment;
3. the availability of implementation of 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 effects of rapidly increasing recovery stress;
5. Possibility of forming a basic module for working with voltages up to 145 kilovolts and above.
A distinctive feature of the design is the ability to break an electrical circuit in 5 milliseconds, which is almost impossible to perform with power devices of other designs.
The hybrid circuit breaker device was ranked among the top ten developments of the year according to the MIT (Massachusetts Institute of Technology) Technology Review.
Other manufacturers of electrical equipment are engaged in similar research. They also achieved certain results. But ABB is ahead of them in this matter. Its management believes that the transmission of AC power is causing its great losses. They can be significantly reduced by using high voltage direct voltage circuits.
When assembling an electrical panel or connecting new large household appliances, a home craftsman will certainly face such a problem as the need to select circuit breakers. They provide electrical and fire safety, so choosing the right machine is a guarantee of the safety of you, your family and property.
What is the machine for
In the power supply circuit, the machine is installed to prevent overheating of the wiring. Any wiring is designed to carry a certain current. If the passed current exceeds this value, the conductor begins to heat up too much. If this situation persists for a sufficient period of time, the wiring begins to melt, resulting in a short circuit. The automatic circuit breaker is installed to prevent this situation.
The second task of the circuit breaker is to turn off the power when a short-circuit current (SC) occurs. When closed, the currents in the circuit increase many times and can reach thousands of amperes. So that they do not destroy the wiring and damage the equipment included in the line, the circuit breaker must turn off the power as quickly as possible - as soon as the current exceeds a certain limit.
In order for the protective circuit breaker to properly perform its functions, it is necessary to correctly select the machine in all parameters. There are not so many of them - only three, but each must be dealt with.
What are the automatic circuit breakers
To protect the conductors of a single-phase 220 V network, there are single-pole and double-pole disconnecting devices. Only one conductor is connected to single-pole - phase, to two-pole and phase and zero. Single-pole machines are installed on a 220 V internal lighting circuit, on socket groups in rooms with normal operating conditions. They are also placed on some types of loads in three-phase networks, connecting one of the phases.
For three-phase networks (380 V), there are three and four-pole. These circuit breakers (the correct name is a circuit breaker) are put on a three-phase load (ovens, hobs and other equipment that operates from a 380 V network).
In rooms with high humidity (bathroom, bath, pool, etc.), two-pole circuit breakers are installed. They are also recommended to be installed on powerful equipment - on washing machines, dishwashers, boilers, ovens, etc.
It's just that in emergency situations - with a short circuit or insulation breakdown - a phase voltage can enter the neutral wire. If a single-pole device is installed on the power line, it will disconnect the phase conductor, and a zero with a dangerous voltage will remain connected. This means that there is a possibility of electric shock when touched. That is, the choice of the machine is simple - single-pole switches are placed on some of the lines, and double-pole on some. The exact amount depends on the condition of the network.
For a three-phase network, there are three-pole circuit breakers. Such an automatic machine is installed at the entrance and at consumers, to which all three phases are supplied - an electric stove, a three-phase hob, an oven, etc. For other consumers, two-pole circuit breakers are installed. They must disconnect both phase and neutral without fail.
Example of wiring a three-phase network - types of circuit breakers
The choice of the rating of the circuit breaker does not depend on the number of wires connected to it.
Determining the denomination
Actually, from the functions of the circuit breaker, the rule for determining the rating of the circuit breaker follows: it must operate until the current exceeds the wiring capabilities. And this means that the current rating of the machine must be less than the maximum current that the wiring can withstand.
Based on this, the algorithm for choosing a circuit breaker is simple:
- for a specific site.
- See what maximum current this cable can withstand (see the table).
- Further, of all the ratings of the circuit breakers, we select the closest smaller one. The ratings of the machines are tied to the permissible continuous load currents for a particular cable - they have a slightly lower rating (available in the table). The list of denominations looks like this: 16 A, 25 A, 32 A, 40 A, 63 A. From this list, choose the right one. There are ratings and less, but they are practically not used anymore - we have too many electrical appliances and they have considerable power.
Example
The algorithm is very simple, but it works flawlessly. To make it clearer, let's look at an example. Below is a table that shows the maximum allowable current for conductors that are used at. There are also recommendations regarding the use of machines. They are given in the column "Rated current of the circuit breaker". It is there that we are looking for ratings - it is slightly less than the maximum allowable for the wiring to work in normal mode.
| Cross-section of copper wires | Permissible continuous load current | Maximum load power for a single-phase 220 V network | Rated current of the circuit breaker | Limiting current of the circuit breaker | |
|---|---|---|---|---|---|
| 1.5 sq. mm | 19 A | 4.1 kW | 10 A | 16 A | lighting and signaling |
| 2.5 sq. mm | 27 A | 5.9 kW | 16 A | 25 A | socket groups and electric underfloor heating |
| 4 sq. Mm | 38 A | 8.3 kW | 25 A | 32 A | air conditioners and water heaters |
| 6 sq. Mm | 46 A | 10.1 kW | 32 A | 40 A | electric stoves and ovens |
| 10 sq. mm | 70 A | 15.4 kW | 50 A | 63 A | introductory lines |
In the table we find the selected wire cross-section for this line. Suppose we need to lay a cable with a cross section of 2.5 mm 2 (the most common when laying to medium power devices). A conductor with such a cross section can withstand a current of 27 A, and the recommended rating of the machine is 16 A.
How will the chain work then? As long as the current does not exceed 25 A, the machine does not turn off, everything works as usual - the conductor heats up, but not to critical values. When the load current begins to increase and exceeds 25 A, the machine does not turn off for some time - perhaps these are starting currents and they are short-term. It turns off if the current exceeds 25 A by 13% for a sufficiently long time. In this case, if it reaches 28.25 A. Then the power pack will work, de-energize the branch, since this current already poses a threat to the conductor and its insulation.
Power calculation
Is it possible to choose an automatic machine according to the load power? If only one device is connected to the power line (usually these are large household appliances with high power consumption), then it is permissible to make a calculation based on the power of this equipment. Also, in terms of power, you can choose an introductory machine, which is installed at the entrance to a house or apartment.
If we are looking for the nominal value of the input machine, it is necessary to add up the power of all devices that will be connected to the house network. Then the found total power is substituted into the formula, the operating current for this load is found.
After we have found the current, we choose the denomination. It can be either slightly more or slightly less than the found value. The main thing is that its shutdown current does not exceed the maximum permissible current for this wiring.
When can this method be used? If the wiring is laid with a large margin (this is not bad, by the way). Then, in order to save money, you can install automatic switches corresponding to the load, and not to the cross-section of the conductors. But once again we draw attention to the fact that the long-term permissible current for the load must be greater than the limiting current of the circuit breaker. Only then will the choice of the circuit breaker be correct.
Choosing the breaking capacity
The above describes the selection of the bag for the maximum permissible load current. But the circuit breaker must also turn off when a short circuit (short circuit) occurs in the network. This characteristic is called breaking capacity. It is displayed in thousands of amperes - this is the order of currents that can reach during a short circuit. The choice of a circuit breaker for breaking capacity is not very difficult.
This characteristic shows at what maximum value of the short-circuit current the machine retains its operability, that is, it can not only turn off, but will also work after it is turned on again. This characteristic depends on many factors and for accurate selection it is necessary to determine the short-circuit currents. But for wiring in a house or apartment, such calculations are done very rarely, but are guided by the distance from the transformer substation.
If the substation is located near the entrance to your house / apartment, they take an automatic device with a disconnecting capacity of 10,000 A, for all other city apartments 6,000 A is enough. and a breaking capacity of 4,500 A. The networks here are usually old and short-circuit currents are not large. And since the price rises significantly with increasing breaking capacity, the principle of reasonable economy can be applied.
Is it possible to put bags with a lower breaking capacity in city apartments? In principle, it is possible, but no one guarantees that after the first short circuit you will not have to change it. He may have time to turn off the network, but at the same time it will be inoperative. In the worst case, the contacts will melt and the machine will not have time to shut down. Then the wiring will melt and a fire may occur.
Electromagnetic release type
The machine should operate when the current rises above a certain mark. But the network periodically experiences short-term overloads. They are usually associated with inrush currents. For example, such overloads can be observed when the compressor of the refrigerator, the motor of the washing machine, etc. is turned on. The circuit breaker with such temporary and short-term overloads should not be tripped, therefore they have a certain response delay.
But if the current increased not because of an overload but because of a short circuit, then during the time that the circuit breaker "waits", its contacts will melt. This is why there is an electromagnetic automatic release. It operates at a certain current value, which can no longer be an overload. This indicator is also called the cut-off current, since in this case the circuit breaker cuts off the line from the power supply. The magnitude of the operating current can be different and is displayed in letters that stand in front of the numbers indicating the rating of the machine.
There are three most common types:
What characteristics should you choose a bag with? In this case, the choice of the circuit breaker is also based on the remoteness of your household from the substation and the state of the power grids, the choice of the circuit breaker is carried out using simple rules:
- With the letter "B" on the body, they are suitable for summer cottages, houses, villages and townships that receive power supply through air vents. They can also be installed in the apartments of old houses, in which the reconstruction of the in-house electrical network has not been carried out. These circuit breakers are not always on sale, they cost a little more than category C, but can be delivered on request.
- Pouches with a "C" on the body are the most widely used option. They are installed in networks with normal conditions, suitable for apartments in new buildings or after overhaul, in private houses near the substation.
- Class D is used in factories, in workshops with equipment with high inrush currents.
That is, in fact, the choice of a circuit breaker in this case is simple - type C is suitable for most cases. It is in stores in a large assortment.
Which manufacturers should you trust
And finally, let's pay attention to manufacturers. The choice of the machine cannot be considered complete if you have not thought about which company the circuit breakers you will buy. You should definitely not take unknown companies - electricians are not an area where you can experiment. More details about choosing a manufacturer in the video.
Mechanization and automation. Types of automatic devices.
Basic concepts of TAU
In any process performed by a person, two types of operations can be distinguished:
1.working operations;
2. control and management operations.
Working operations are necessary for the direct implementation of the technical process, for example, removing chips, rotating the machine shaft. Work operations are associated with the expenditure of physical energy. Replacement of human labor in working operations is called mechanization.
Control operations associated with the measurement of physical quantities, and control operations are designed for the correct and high-quality conduct of the process and are aimed at improving it. Replacement of human labor in the operations of monitoring and controlling the operation of instruments and devices is called automation.
A set of technical devices that perform this process and are subject to automation. called object of management(OU).
Technical devices performing control operations are called automatic.
The set of automatic devices and control objects forms control system(SU). A system in which all work operations and control operations are performed automatically, without human intervention, is called automatic... A system in which only part of the management operations are automatically performed, and the other part is performed by people, is called automated.
When automating production processes, depending on the use of tools and methods, both simpler and more complex influences on the process are possible. By purpose, the following types of automatic devices can be distinguished.
1. Automatic control system (SAK).
2. Automatic protection and blocking system (SAZ and B).
3. Automatic calculating devices (ASRU).
4. Automatic control systems (ACS).
5. Automated control systems (ACS).
1. SAC are designed to measure a controlled physical quantity and register it without human involvement. It includes a sensor, a recording device (indicating or self-recording) and an alarm device.
2. SAS serves to prevent damage to equipment in the event of abnormal operating modes. Automatic blocking is used to prevent personnel errors.
3. Automatic solvers include control computers that perform various calculations and determine the optimal mode of operation.
4. Automatic regulation is called maintaining a constant or variable according to a given law of some output value. ATS is a special case of ACS.
5. The ACS carries out a complex complex of actions on the object, changing the parameter of the controlled technical process in accordance with the change in the controlled physical quantity. In addition, the task of the ACS includes:
· Implementation of extreme regulation;
Optimal control, i.e. finding optimal modes for solving certain problems;
· Adaptation or self-tuning of the automatic device.
Thus, we can say that the subject of TAU studies:
1. The principles of building ATS and ACS.
2. Determination of the mathematical description of these systems in the form of differential equations (DE) and transfer functions.
3. Research and analysis of the stability of these systems.
4. Analysis of the accuracy of control processes in a steady state.
5. Synthesis of ACS and ACS. Includes the definition of a control algorithm, i.e. the law of regulation, in accordance with which the automatic device must act on the object in the event of a change in the controlled value.
Hello friends. The topic of the post is the types and types of circuit breakers (automatic machines, AB). I also want the results of the crossword puzzle.
Types of machines:
It can be divided into AC, DC and universal switches operating at any current.
Design - there are air, modular, in a molded case.
Indicator of rated current. The minimum operating current of a modular machine is 0.5 Ampere, for example. I will write soon about how to choose the right rated current for a circuit breaker, subscribe to the blog news so as not to miss it.
Rated voltage, another difference. In most cases, AB work in networks with a voltage of 220 or 380 volts.
There are current-limiting and non-current limiting.
All breaker models are classified according to the number of poles. They are divided into single-pole, two-pole, three-pole and four-pole machines.
Types of releases - overcurrent release, shunt release, undervoltage release or undervoltage release.
The speed of the circuit breakers. High-speed, normal and selective automata are distinguished. They come with a time delay, without it, independent or inversely dependent on the current, the response time. Features can be combined.
They differ in the degree of protection from the environment - IP, mechanical stress, material conductivity. By type of drive - manual, motor, spring.
By the presence of free contacts and the method of connecting conductors.
Types of machines:
What does type AB mean?
Circuit breakers contain two types of breakers inside - thermal and magnetic.
The magnetic high-speed circuit breaker is designed for short-circuit protection. The breaker can be triggered in a time from 0.005 to several seconds.
The thermal breaker is much slower, designed for overload protection. It works with a bimetallic plate that heats up when the chain is overloaded. Response time from a few seconds to minutes.
The combined pickup characteristic depends on the type of connected load.
There are several types of AB shutdown. They are also called - types of trip time-current characteristics.
A, B, C, D, K, Z.
A- It is used to open circuits with long electrical wiring, it serves as a good protection for semiconductor devices. They operate at 2-3 rated currents.
B- for general purpose lighting network. They operate at 3-5 rated currents.
C- lighting circuits, electrical installations with moderate starting currents. These can be motors, transformers. The overload capacity of the magnetic circuit breaker is higher than that of type B circuit breakers. They operate at 5-10 rated currents.
D- are used in circuits with active-inductive load. For electric motors with high starting currents, for example. At 10-20 rated currents.
K- inductive loads.
Z- for electronic devices.
It is better to look at the data on the operation of switches of types K, Z in the tables specifically for each manufacturer.
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