Electrical overloads are common. To protect appliances powered by electricity from such voltage drops, circuit breakers were invented. Their task is simple - to break the electrical circuit if the voltage exceeds the nominal limits.
The first such devices were plugs familiar to everyone, which are still in some apartments. As soon as the voltage jumps above 220 V, they are knocked out. Modern types of circuit breakers are not only plugs, but also many other varieties. Their remarkable feature is the possibility of repeated use.
Classification
Modern GOST 9098-78 distinguishes 12 classes of circuit breakers:
This classification of circuit breakers is very convenient. If you wish, you can figure out which of the devices to install in the apartment, and which for production.
Types (kinds)
GOST R 50345-2010 divides circuit breakers into the following types (the division is based on sensitivity to overloads), marked with Latin letters:
These are the main circuit breakers used in residential buildings and apartments. In Europe, the marking begins with the letter A - the most sensitive circuit breakers to overloads. They are not used for domestic needs, but are actively used to protect the power supply circuits of precision instruments.
There are also three more markings - L, Z, K.
Distinctive design features
Automatic devices consist of the following units:
- main contact system;
- arc chute;
- the main drive of the release device;
- various types of release;
- other auxiliary contacts.
The contact system can be multistage (one-, two- and three-stage). It consists of arcing, main and intermediate contacts. Single-stage contact systems are mainly made from sintered metal.
In order to somehow protect parts and contacts from the destructive force of an electric arc, reaching 3,000 ° C, an arc chute is provided. It consists of several arc quenching grids. There are also combined devices that can extinguish a high current electric arc. They contain slit chambers along with a grille.
For any circuit breaker, there is a current limit. Due to the protection of the machine, it can not lead to breakage. With huge overloads of such a current, the contacts can either burn out or even weld to each other. For example, for the most common household appliances with a trip current from 6 A to 50 A, the current limit can be from 1000 A to 10,000 A.
Modular designs
Designed for small currents. Modular automatic switches consist of separate sections (modules). The whole structure is mounted on a DIN rail. Let's consider in more detail the device of the modular switch:
- On / off is made by a lever.
- The terminals to which the wires are connected are screw.
- The device is fixed to the DIN rail with a special latch. This is very convenient, because such a switch can be easily dismantled at any time.
- The connection of the entire electrical circuit is made due to the movable and fixed contacts.
- Disconnection occurs with the help of some kind of release (thermal or electromagnetic).
- Contacts are specially placed next to the arc chute. This is due to the occurrence of a powerful electric arc during the disconnection of the connection.
VA series - industrial switches
Representatives of these machines are primarily intended for use in AC circuits of 50-60 Hz, with an operating voltage of up to 690 V. They are also used for direct current of 450 V and current strength of up to 630 A. Such switches are designed for very rare operational use ( no more than 3 times per hour) and protection of lines from short circuit and electrical overload.
Important features of this series include:
- high breaking capacity;
- a wide range of electromagnetic releases;
- button for testing the device with free tripping;
- load break switches with special protection;
- remote control through a closed door.
AP series
Automatic circuit breaker ap is able to protect electrical installations, motors from sudden voltage surges and short circuits within the network. The launches of such mechanisms are not intended to be very frequent (5-6 times per hour). Automatic switch ap can be two-pole and three-pole.
All structural elements are located on a plastic base, which is closed with a lid on top. In case of large overloads, the free tripping mechanism is activated, and the contacts open automatically. At the same time, the thermal release withstands the operating time, and the electromagnetic release provides instantaneous disconnection in the event of a short circuit.
When operating the machine, it is desirable to adhere to the following conditions:
- With air humidity of 90%, the temperature should not exceed 20 degrees.
- The operating temperature ranges from -40 to +40 degrees.
- Vibration at the attachment point should not exceed 25 Hz.
It is strictly forbidden to work in an explosive atmosphere containing gases that destroy metal and winding, near the pure energy of heating devices, water flows and splashes, in places with conductive dust.
The variety of circuit breakers allows you to easily choose a device for an apartment or house. It is best to invite a specialist to install it.
The main difference between these switching devices and all other similar devices is a complex combination of abilities:
1. maintain nominal loads in the system for a long time due to the reliable transmission of powerful electricity flows through their contacts;
2. to protect the operating equipment from accidental malfunctions 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 circuit breakers, providing:
different power schemes;
changing the network configuration;
decommissioning equipment.
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 switch.
In the energy sector, the division of electrical systems by types of current is accepted:
constant;
alternating sinusoidal.
In addition, there is a classification of equipment according to the magnitude of the voltage on:
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, circuit breakers in AC circuits are conventionally divided into:
1. modular;
2. molded case;
3. power air.
Modular designs
Specific execution in the form of small standard modules with a width multiple 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 circuit breaker state, a lever with two fixed positions is installed:
the upper one is designed to supply current through a closed power contact;
lower - provides a break in the power circuit.
Each of these automata is designed for long-term operation at a certain value (In). If the load becomes greater, then the power contact breaks. For this, two types of protection 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 response time on the load or accident current passing through it.
The graph shown in the picture is for one specific circuit breaker, when the cut-off operating zone is selected to be 5÷10 times the rated current.
During the initial overload, a thermal release operates, 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 self-eliminate and eliminate unnecessary disconnections. 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 the equipment with its energy, then the electromagnetic coil comes into operation. It impulse due to the surge of the load that has arisen throws the core onto the tripping mechanism in order to instantly stop the transcendental mode.
The graph shows that the higher the short-circuit currents, the faster they are turned off by the electromagnetic release.
According to the same principles, a household automatic steam fuse works.
When high currents break, an electric arc is created, the energy of which can burn out the contacts. To exclude its action in circuit breakers, an arc chute is used, which divides the arc discharge into small flows and extinguishes them due to cooling.
Multiplicity of cut-offs of modular structures
Electromagnetic releases are configured and selected to work with certain loads because they create different transients at start-up. For example, during the switching on of various lamps, a short-term inrush current due to the changing resistance of the filament can approach three times the nominal value.
Therefore, for the outlet group of apartments and lighting circuits, it is customary to choose circuit breakers with a time-current characteristic of type "B". It is 3÷5 In.
Asynchronous motors, when spinning the rotor with the drive, cause higher overload currents. For them, automatic machines with the characteristic “C” are selected, or - 5 ÷ 10 In. Due to the created time and current margin, they allow the motor to spin up and guarantee to reach the operating mode without unnecessary shutdowns.
In industrial production, on machines and mechanisms, there are loaded drives connected to engines that create more increased overloads. For such purposes, 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, automata 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 for different manufacturers, the cutoff actuation ratio 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 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 increased loads, 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 conditionally divided into three groups with the possibility of switching loads up to 250, 1000 and 3200 amperes.
The design of their housing: three- or four-pole models.
Power air circuit breakers
They work in industrial installations and operate with very high currents up to 6.3 kiloamperes.
These are the most complex devices of switching devices of low-voltage equipment. They are used for the operation and protection of electrical systems as incoming and outgoing devices of high-power switchgear and for connecting generators, transformers, capacitors or large 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 chute chambers with gratings are installed on each side of the disconnection.
The switching coil, the closing spring, the motor drive for charging the spring and the automation elements are involved in the operation algorithm. 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 required to:
high reliability;
security;
speed;
ease of use;
relative noiselessness during operation;
optimal cost.
Loads that break during emergency shutdown are accompanied by a very strong arc. To extinguish it, various methods are used, including breaking the circuit in a special environment.
This switch includes:
contact system;
arc extinguishing device;
live parts;
insulated body;
drive mechanism.
One of these switching devices is shown in the photograph.
For high-quality operation of the circuit in such designs, in addition to the operating voltage, take into account:
the nominal value of the load current for its reliable transmission in the on state;
the maximum short-circuit current in terms of the effective value that the tripping mechanism can withstand;
permissible component of the aperiodic current at the moment of circuit break;
the possibility of automatic reclosing and the provision of two AR cycles.
According to the methods of extinguishing the arc during shutdown, the circuit breakers are classified into:
oil;
vacuum;
air;
SF6;
autogas;
electromagnetic;
autopneumatic.
For reliable and convenient operation, they are equipped with a drive mechanism that can use one or more types of energy or combinations thereof:
cocked spring;
lifted load;
compressed air pressure;
electromagnetic pulse from the solenoid.
Depending on the conditions of use, they can be designed 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.
Auxiliary systems of such circuit breakers can have a very complex branched structure and be placed on additional panels in special technical buildings.
DC circuits
These networks also have 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 massively introduced.
They successfully complement the classes of old automata such as , AE and other similar ones, which were fixed on the walls of the shields with screw connections.
Modular DC designs have the same design and operating principle as their AC counterparts. They can be performed by one or several blocks and are selected according to the load.
Electrical equipment above 1000 volts
High-voltage circuit breakers for direct current operate at 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 analogues on alternating current.
hybrid switch
Scientists from the Swedish-Swiss company ABB managed to develop a high-voltage DC switch that combines two power structures in its device:
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, the following device is assembled.
Voltage is applied to the top busbar of the hybrid vacuum circuit breaker, and the voltage is removed from the bottom 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 a control mechanism with independent power supply via a fiber optic channel.
Through the use of high-precision technologies, the design developers managed to achieve consistency in the actions of the actuators of both drives, which fits into a time interval of less than one microsecond.
The circuit breaker is controlled by a relay protection unit built into the power line through a repeater.
The hybrid circuit breaker made it possible to significantly increase the efficiency of composite SF6 and vacuum structures by using 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. respectively, the cost of equipment;
3. the availability of various standards for the creation of structures operating as part of a separate circuit breaker or compact devices at one substation;
4. ability to eliminate the consequences of a rapidly increasing restoring voltage;
5. the 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 the electrical circuit in 5 milliseconds, which is practically impossible to perform with power devices of other designs.
The hybrid circuit breaker device was named one of the top ten designs of the year by the MIT (Massachusetts Institute of Technology) Technology Survey.
Other manufacturers of electrical equipment are also engaged in similar studies. 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 AC electricity. They can be significantly reduced by using high voltage DC circuits.
A circuit breaker, or, more simply, an automaton, is an electrical device that is familiar to almost everyone. Everyone knows that the machine turns off the network when there are some problems in it. If not to be wiser, then these problems are too much electric current. Excessive electric current is dangerous for the failure of all conductors and household electrical equipment, possible overheating, ignition and, accordingly, fire. Therefore, protection against high currents is a classic of electrical circuits, and it has existed since the dawn of electrification.
Any overcurrent protection device has two important tasks:
1) timely and accurately recognize too high current;
2) break the circuit before this current can cause any damage.
In this case, high currents can be divided into two categories:
1) high currents caused by network overload (for example, the inclusion of a large number of household electrical appliances, or the malfunction of some of them);
2) when the neutral and phase conductors are directly connected to each other, bypassing the load.
It may seem strange to someone, but it is with short-circuit overcurrents that everything is extremely simple. Modern electromagnetic releases easily and completely accurately determine the short circuit and turn off the load in a fraction of a second, preventing even the slightest damage to conductors and equipment.
With overload currents, everything is more complicated. Such a current does not differ much from the nominal one, for some time it can flow through the circuit without any consequences. Therefore, there is no need to turn off such a current instantly, especially since it could occur for a very short time. The situation is aggravated by the fact that each network has its own limiting overload current. And not even one.
Circuit breaker device
There are a number of currents, for each of which it is theoretically possible to determine its maximum network outage time, which ranges from several seconds to tens of minutes. But false positives must also be excluded: if the current is harmless to the network, then the shutdown should not occur in a minute or an hour - never at all.
It turns out that the overload protection trip setting must be adjusted for a specific load, its ranges must be changed. And, of course, before installing the overload protection device, it must be loaded and checked.
So, in modern "automatic machines" there are three types of releases: mechanical - for manual switching on and off, electromagnetic (solenoid) - for switching off short-circuit currents, and the most difficult - thermal for protection against overloads. It is the characteristic of thermal and electromagnetic releases that is circuit breaker characteristic, which is indicated by a Latin letter on the body before the number indicating the current rating of the device.
This feature means:
a) the range of operation of the overload protection, due to the parameters of the built-in bimetallic plate, which bends and breaks the circuit when a large electric current flows through it. Fine tuning is achieved by adjusting the screw that presses this very plate;
b) the operating range of the overcurrent protection, determined by the parameters of the built-in solenoid.
Below we list characteristics of modular circuit breakers, we will talk about how they differ from each other and what the machines that have them are intended for. All characteristics represent the relationship between the load current and the tripping time at this current.
1) Characteristic MA - no thermal release. In fact, it really is not always needed. For example, protection of electric motors is often carried out using overcurrent relays, and in such a case, an automatic machine is needed only for protection against short-circuit currents.
2) Feature A. The thermal release of an automaton of this characteristic can already work at a current of 1.3 of the nominal. In this case, the shutdown time will be about an hour. At a current that is twice the rated current, an electromagnetic release can come into action, which operates in about 0.05 seconds. But if, when the current is doubled, the solenoid still does not work, then the thermal release still remains “in play”, disconnecting the load in about 20-30 seconds. At a current that is three times the rated current, the electromagnetic release is guaranteed to operate in hundredths of a second.
Circuit breakers of characteristic A are installed in those circuits where short-term overloads cannot occur in normal operating mode. An example would be circuits containing devices with semiconductor elements capable of failing at a slight excess of current.
3) Characteristic B. The characteristic of these automata differs from characteristic A in that the electromagnetic release can only operate at a current that exceeds the rated current not by two, but by three or more times. The solenoid response time is only 0.015 seconds. The thermal release with a threefold overload of the machine B will work in 4-5 seconds. Guaranteed operation of the machine occurs at a fivefold overload for alternating current and at a load exceeding the rated value by 7.5 times in direct current circuits.
Circuit breakers characteristic B are used in lighting networks, as well as other networks in which the starting current increase is either small or absent at all.
4) Characteristic C. This is the most famous characteristic for most electricians. Automata C are distinguished by an even greater overload capacity compared to automata B and A. Thus, the minimum operating current of the electromagnetic release of the automaton of characteristic C is five times the rated current. At the same current, the thermal release trips after 1.5 seconds, and the guaranteed operation of the electromagnetic release occurs at a tenfold overload for alternating current and at a 15-fold overload for DC circuits.
Characteristics of circuit breakers B, C and D
5) Characteristic D- has a very high load capacity. The minimum operating current of the electromagnetic solenoid of this machine is ten rated currents, and the thermal release can operate in 0.4 seconds. Guaranteed operation is provided with a twenty-fold current overload.
Circuit breakers characteristic D are intended, first of all, for connection of the electric motors having big starting currents.
6) K characteristic has a large spread between the maximum solenoid actuation current in AC and DC circuits. The minimum overload current at which the electromagnetic release can operate is eight rated currents for these machines, and the guaranteed operating current of the same protection is 12 rated currents in the AC circuit and 18 rated currents in the DC circuit. The operating time of the electromagnetic release is up to 0.02 seconds. The thermal release of the machine K can operate at a current exceeding the rated current by only 1.05 times.
Due to such features of the characteristic K, these machines are used to connect a purely inductive load.
7) Z characteristic also has differences in the currents of guaranteed operation of the electromagnetic release in AC and DC circuits. The minimum possible operating current of the solenoid for these machines is two nominal, and the guaranteed operating current of the electromagnetic release is three nominal currents for AC circuits and 4.5 nominal currents for DC circuits. The thermal release of automata Z, like that of automata K, can operate at a current of 1.05 of the nominal.
Z machines are used only for connecting electronic devices.
Alexander Molokov
Circuit breakers are devices whose task is to protect the 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. 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 article we will tell you what types of circuit breakers are and their characteristics.
Automatic protective switches: classification and differences
In addition to residual current devices that are not used individually, there are 3 types of circuit breakers. They work with loads of different sizes and differ from each other in their design. These include:
- Modular AV. These devices are mounted in household networks in which currents of insignificant magnitude flow. They usually have 1 or 2 poles and a width that is a multiple of 1.75 cm.
- Cast switches. They are designed to work in industrial networks, with currents up to 1 kA. Made in a cast case, which is why they got their name.
- Air electric machines. These devices are available with 3 or 4 poles and can withstand currents up to 6.3 kA. Used in electrical circuits with high power installations.
There is another type of circuit breaker - 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 the 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, which differ from each other in the principle of decoupling:
- 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 drawn in under the influence of a large current and causing 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 machine, the plate begins to heat up and, bending to the side, touches the disconnecting element, which operates and de-energizes the circuit. The time 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 option 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 which you can not only turn off, but also turn on the AB, without even approaching the switchboard.
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.
It’s not difficult to choose a device for a circuit according to their number, you just need to know where different types of AB are used:
- Single terminals are installed to protect lines that include sockets and lighting fixtures. They are mounted on a phase wire without capturing zero.
- A 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-terminal networks are installed in semi-industrial scale networks, to which devices such as borehole pumps or car repair equipment can be connected.
- Four-pole ABs allow you to protect electrical wiring with four cables from short circuits and overloads.
The use of machines of different poles - 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 the excess 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 ABs work instantly, while others take time.
There is the following marking of devices according to their sensitivity:
- A. Breakers of this type are the most sensitive and respond instantly to an increase in load. They are practically not installed in household networks, protecting circuits with high-precision equipment with their help.
- B. These circuit breakers operate with a slight delay when the current increases. Usually they are included in lines with expensive household appliances (LCD TVs, computers, and others).
- C. Such devices are the most common in household networks. Their shutdown does not occur immediately after the increase in current strength, but after a while, which makes it possible to normalize it with a slight difference.
- D. The sensitivity of these devices to the increase in current is the lowest of all the listed types. They are most often installed in shields on the approach line to the building. They provide insurance for 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 most current, which means it can provide the most 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 high-power protective device to a normal household circuit, it will not de-energize the circuit, even when the current value is much higher than that which the cable can withstand. The insulating layer will heat up, then start to melt, but no shutdown will occur. The fact is that the current strength, which is destructive for the cable, will not exceed the AB rating, and the device will “think” that there was no emergency. Only when the melted insulation causes a short circuit will the machine turn off, but by that time a fire may already have started.
Here is a table that shows the ratings of machines for various electrical networks.
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 eventually, under the influence of high currents, it will fail due to “sticky” contacts.
Clearly about the types of circuit breakers in the video:
Conclusion
The circuit breaker, the characteristics and types of which we examined in this article, is a very important device that protects the electrical line from damage by powerful currents. The operation of networks that are not protected by automatic machines is prohibited by the Electrical Installation Rules. The most important thing is to choose the right type of AB that is suitable for a particular network.
Everyone knows in general terms what a circuit breaker installed in an electrical panel is. Most of the population at the genetic level knows when the light went out in the apartment, gently go and check if the machine in the floor board has turned off, and turn it on if necessary. However, not everyone has an idea about the technical characteristics of these devices, and according to what criteria they need to be selected to maintain the high performance of the switchboard.
Greetings to all friends on the Electrician in the House website. Today we will analyze a very important, in my opinion, topic that directly affects the normal operating conditions of automatic protection devices, namely - . Not everyone knows what the symbols and designations on the case of the machine mean, so let's decipher the markings and analyze in detail what each inscription on the case of the circuit breaker means.
Marking of electric machines - designations on the case
All circuit breakers have certain technical characteristics. To get acquainted with them, when choosing a machine, a marking is applied to the case, which includes a set of diagrams, letters, numbers and other symbols. Friends will agree that the appearance of the machine will not be able to say anything about itself and all its characteristics can only be recognized by the applied markings.
The marking is applied on the front (front) side of the body of the vending machine with resistant indelible paint, so that you can familiarize yourself with the parameters even when the vending machine is in operation, that is, it is installed in a switchboard on a DIN rail and wires are connected to it (no need to disconnect the wires and pull out it from the shield to read the markings).
In the picture below you can see some examples, how to mark electrical machines different manufacturers. Each of them is clearly visible markings made in different letters and numbers. In this article, we will not analyze industrial protection devices, but will only touch on ordinary household modular machines. But in any case, the article will be of interest not only to beginners, but also to professionals, “bison” who encounter this on a daily basis, it will also be interesting to remember the basics of their profession.
Deciphering the marking of the machine
In order to choose the right circuit breaker when buying, you should pay attention not only to the appearance and brand of the device, but also to its characteristics. Let's take a look at what characteristics the manufacturer displays on the case of the circuit breaker in order to select it correctly. Marking on the machine presents the following information about itself.
1. Manufacturer (brand) of the circuit breaker
The marking of circuit breakers begins with the logo or name of the manufacturer. The pictures show the machines of the most popular brands hager, IEK, ABB, Schneider Electric.
These brands have been presented to the world public for a long time and during their existence have proven themselves to be the release of quality products. On the case, the name of the manufacturer is applied at the very top and it is hard not to notice it.
2. Linear series of automata (model)
The circuit breaker model usually reflects the device series in the manufacturer's line and is an alphanumeric designation, for example, SH200 and S200 series circuit breakers belong to ABB, while Schneider Electric has Acti9, Nulti9, Brownie.
An example of how the marking of circuit breakers from Schneider Electric, hager and IEK is indicated.
Often, a series is assigned to an automatic machine to distinguish models by technical characteristics or price category, for example, SH200 are designed for short circuits up to 4.5 kA, less expensive to manufacture and cheaper than S200, designed for 6 kA.
3. Time-current characteristic of the machine
This characteristic is indicated by a Latin letter. In total, there are 5 types of time-current characteristics: "B", "C", "D", "K", "Z". But the most common of them are the first three: "B", "C" and "D".
Automatic machines with characteristics of the type "K" and "Z" are used to protect consumers, where an actively inductive load and electronics are used, respectively.
The most versatile, which is suitable for everyday use - characteristic type "C". Most electricians use it to protect electrical wiring. Narrow-profile machines with BTX "B" or "D" can only be found in specialized stores and, often, by order.
Friends on the topic of the time of the current characteristics of automata, I have a separate article, please come in, read, familiarize yourself.
4. Rated current of the machine
After the letter value comes a number that determines the rating of the circuit breaker. The rating determines the maximum value of current that can continuously pass without tripping the circuit breaker. Moreover, the value of the rated current is indicated for a certain ambient temperature + 30 degrees.
For example, if rated current of the machine equal to 16A, then the machine will keep this load and not turn off at an ambient temperature not higher than +30 degrees. If the temperature is above +30, then the machine can work at a current of less than 16 A.
If overloads occur in the network, that is, a situation when the load current exceeds the rated current reacts to this thermal release automatic switch. Depending on the multiplicity of the overload, the time during which the machine will turn off will be from several minutes to seconds. The current at which the thermal release will operate must exceed the nominal value of the machine by 13% - 55%.
When a short circuit occurs in the network, an overcurrent occurs, to which it reacts electromagnetic release automatic switch. A serviceable machine in the event of a short circuit must operate within 0.01 - 0.02 seconds, otherwise the insulation of the electrical wiring will begin to melt with the risk of further ignition.
5. Rated voltage
Right under marking on the machine time-current characteristics there is a designation of the rated voltage for which this machine is designed. The rated voltage is displayed in Volts (V/V), and can be either constant (“-”) or variable (“~”).
The value of the rated voltage determines for which networks the device is intended. Voltage marking provides two values for single-phase and three-phase networks. For example, marking 230/400V~ means that 230 Volt is the voltage of a single-phase network, 400 Volt is the voltage of a three-phase network. The symbol "~" means AC voltage.
6. Breaking current limit
The next parameter is the tripping current limit, or as it is also called breaking capacity of the machine. This parameter characterizes the short-circuit current that the machine is able to pass through itself and turn off without losing its performance (without the risk of failure).
The electrical network is a complex system in which overcurrents often occur due to short circuits. Overcurrents are short-term, but are characterized by a large value. Each circuit breaker has a limiting switching capacity, which determines the ability to withstand overcurrents and operate at the same time.
For modular circuit breakers, the breaking current limit is 4500, 6000 or 10000. The values are indicated in Amperes.
7. Current limiting class
Immediately below the value of the limiting tripping current, the so-called current limiting class. The occurrence of overcurrents is dangerous because when they appear, thermal energy is released. As a result, the insulation of the electrical wiring begins to melt.
The circuit breaker will trip when the short circuit current reaches its maximum value. And in order for the short-circuit current to reach its maximum, it takes some time and the longer this time is, the greater the damage to the equipment and insulation of the electrical wiring.
The current limiter contributes to the accelerated shutdown of the circuit breaker, thereby preventing the short circuit current from reaching its maximum value. Essentially, this setting limits the short circuit time.
There are three classes of current limiter, which are marked in a black square. The higher the class, the faster the machine will turn off.
- - class - 1 there is no marking, or in other words, machines, on the case of which there is no current limiting class, belong to the first class. The limit time is more than 10ms;
- - class - 2 limits the short-circuit current passage time within 6-10 ms;
- - class - 3 limits the short-circuit current passage time within 2.5-6 ms (the fastest).
8. Wiring diagram and terminal designation
Some manufacturers apply a circuit diagram for connecting the machine to the case to inform the consumer. The connection diagram is an electrical circuit with the designation of thermal and electromagnetic releases. The diagram also marks the contacts indicating the place of connection of the wires.
On single pole machines contacts are marked as "1" - top and "2" - bottom. As a rule, the power wire is connected to the upper contact, and the load is connected to the lower one. By the way, there is a separate article on this topic, how to properly connect the machine. On bipolar machines, the contacts are marked "1", "3" - top; "2", "4" - lower.
And this is how the designation of the circuit and contacts for connection on a two-pole circuit breaker looks like
Also on two- and four-pole machines near the connection diagram, you can find a designation in the form of the Latin letter "N", indicating the terminal for connecting the zero working conductor. This is important, since not all poles of multi-pole circuit breakers have releases (thermal and electromagnetic).
9. Article
On any side of the body of the machine, information about the product (article, QR code) is also applied, provided by the manufacturer, which helps to easily find a specific model in the catalog of stores.
After reading the above information, it will not be a problem for you, and you can easily choose a protection device with the characteristics that suit you.
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