Every person in in general terms knows what a circuit breaker installed in the 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 normal conditions operation 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 agree that appearance the machine will not be able to say anything about itself and all its characteristics can only be recognized by the markings applied.
The marking is applied on the front (front) side of the body of the machine with resistant, indelible paint, so that you can familiarize yourself with the parameters even when the 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 devices protection, and we 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 for its right choice. 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 the machine to distinguish models by technical specifications or price category, for example, SH200 are short-circuit rated up to 4.5 kA, less expensive to manufacture and cheaper than S200, rated at 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 certain temperature environment+ 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. 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.
Friends, if this article was interesting for you, I would be grateful if you share it in social networks. If you have any questions or suggestions, feel free to ask them in the comments, I will try to answer everyone.
From the very beginning of the emergence of electricity, engineers began to think about the safety of electrical networks and devices from current overloads. As a result, many different devices have been designed that are reliable and quality protection. One of the latest developments has become electric machines.
This device is called automatic due to the fact that it is equipped with the function of turning off the power in automatic mode, in the event of short circuits, overloads. Conventional fuses after operation must be replaced with new ones, and the machines can be turned on again after the causes of the accident have been eliminated.
Such a protective device is necessary in any electrical network scheme. The circuit breaker will protect the building or premises from various emergencies:
- Fires.
- Electric shocks to a person.
- Electrical faults.
Types and design features
Need to know information about existing types circuit breakers in order to select the right device at the time of purchase. There is a classification of electric machines according to several parameters.
Breaking capacity
This property determines the short circuit current at which the machine will open the circuit, thereby turning off the network and devices that were connected to the network. According to this property, automata are divided into:
- Automatic machines for 4500 amperes, are used to prevent malfunctions of power lines residential buildings old building.
- At 6000 amperes, they are used to prevent accidents during short circuits in the network of houses in new buildings.
- At 10,000 amperes, they are used in industry to protect electrical installations. A current of this magnitude can be formed in the immediate vicinity of the substation.
The operation of the circuit breaker occurs during short circuits, accompanied by the occurrence of a certain amount of current.
The machine protects the wiring from damage to the insulation by high current.
Number of poles
This property tells us about the largest number of wires that can be connected to the machine to provide protection. In the event of an accident, the voltage at these poles is turned off.
Features of machines with one pole
Such electric machines are the simplest in design, and serve to protect individual sections of the network. Two wires can be connected to such a circuit breaker: an input and an output.
The task of such devices is to protect electrical wiring from overloads and short circuits of wires. The neutral wire is connected to the neutral bus, bypassing the machine. Grounding is connected separately.
Electric machines with one pole are not introductory, since when it is turned off, the phase breaks, and the neutral wire still remains connected to the power supply. It does not provide 100% protection.
Properties of automata with two poles
In cases where an accident requires a complete disconnection from the electrical network, use circuit breakers with two poles. They are used as input. AT emergency cases, or in the event of a short circuit, the entire electrical wiring turns off at the same time. This makes it possible to carry out repair and maintenance work, as well as work on connecting equipment, since complete safety is guaranteed.
Two-pole electric machines are used when it is necessary to have a separate switch for a device powered by a 220 volt network.
An automatic machine with two poles is connected to the device using four wires. Of these, two come from the power supply, and the other two come out of it.
Three-pole electric machines
In an electrical network with three phases, 3-pole machines are used. Grounding is left unprotected, and the phase conductors are connected to the poles.
A three-pole machine serves as an input device for any three-phase load consumers. Most often, this version of the machine is used in industrial conditions to supply electricity to electric motors.
6 conductors can be connected to the machine, three of which are the phases of the electrical network, and the remaining three are coming from the machine and provided with protection.
Using a four-pole machine
To provide protection for a three-phase network with a four-wire system of conductors (for example, an electric motor connected according to the “star” scheme), a 4-pole circuit breaker is used. It plays the role of an introductory device of a four-wire network.
It is possible to connect eight conductors to the device. On the one hand - three phases and zero, on the other hand - the output of three phases with zero.
Time-current characteristic
When devices that consume electricity and the electrical network are operating normally, normal current flow occurs. This phenomenon also applies to the electric machine. But, in the event of an increase in current strength for various reasons above the nominal value, the automatic release trips, and the circuit breaks.
The parameter of this operation is called the time-current characteristic of the electric machine. It is the dependence of the time of operation of the machine and the ratio between the real strength of the current passing through the machine and the nominal value of the current.
The importance of this characteristic lies in the fact that the least number of false positives is provided on the one hand, and current protection is carried out, on the other hand.
In the energy industry, there are situations when a short-term increase in current is not associated with an accident, and the protection should not work. It also happens with electric machines.
Time-current characteristics determine how long the protection will operate, and what current strength parameters will occur. The greater the overload, the faster the machine will work.
Electric machines marked "B"
Automatic switches of category "B" are able to turn off in 5 - 20 s. In this case, the current value is from 3 to 5 nominal current values ≅0.02 s. Such machines are used to protect household appliances, as well as all electrical wiring in apartments and houses.
Properties of machines marked "C"
Electric machines of this category can turn off in 1 - 10 s, at 5 - 10 times the current load ≅0.02 s. These are used in many areas, most popular for houses, apartments and other premises.
The meaning of the marking "D" on the machine
With this class, automata are used in industry and are made in the form of 3-pole and 4-pole versions. They are used to protect powerful electric motors and various three-phase devices. Their operation time is up to 10 seconds, while the operation current can exceed the nominal value by 14 times. This makes it possible to use it with the necessary effect to protect various circuits.
Electric motors with significant power are most often connected through electric machines with characteristic "D", because. starting current is high.
Rated current
There are 12 versions of automatic machines, which differ in the characteristics of the rated operating current, from 1 to 63 amperes. This parameter determines the speed at which the machine switches off when the current limit is reached.
The machine for this property is selected taking into account the cross-section of the conductors of the wires, the allowable current.
The principle of operation of electric machines
normal mode
During normal operation of the machine, the control lever is cocked, current flows through the power wire at the top terminal. Next, the current goes to the fixed contact, through it to the moving contact and through the flexible wire to the solenoid coil. After it, the current goes through the wire to the bimetallic release plate. From it, the current passes to the lower terminal and further to the load.
Overload mode
This mode occurs when the rated current of the machine is exceeded. The bimetallic plate is heated by a large current, bends and opens the circuit. The action of the plate requires time, which depends on the value of the passing current.
The circuit breaker is an analog device. There are certain difficulties in setting it up. The tripping current of the release is adjusted at the factory with a special adjusting screw. After the plate has cooled down, the machine can function again. The temperature of the bimetal strip depends on the environment.
The release does not act immediately, allowing the current to return to its nominal value. If the current does not decrease, the release trips. Overload can occur due to powerful devices on the line, or connecting several devices at once.
Short circuit mode
In this mode, the current increases very quickly. The magnetic field in the solenoid coil moves the core, which activates the release, and disconnects the contacts of the power supply, thereby removing the emergency load of the circuit and protecting the network from possible fire and destruction.
The electromagnetic release operates instantly, which is different from the thermal release. When the contacts of the working circuit are opened, an electric arc appears, the magnitude of which depends on the current in the circuit. It causes destruction of contacts. To prevent this negative effect, an arc chute is made, which consists of parallel plates. In it, the arc fades and disappears. The resulting gases are discharged into a special hole.
It is easier and cheaper to prevent the fire-hazardous consequences of destruction than to complain bitterly about the measures not taken. Prevention of ignition of the electrical network consists in the installation of protective equipment. In the last century, the function of protecting against short circuits and against the danger of overload was entrusted to porcelain fuses with replaceable fuses, then to automatic plugs. However, due to a significant increase in the load on power lines, the situation has changed. It's time to replace outdated devices with reliable machines. In order for the choice of a circuit breaker to end with the acquisition of a device with the appropriate characteristics, information about a number of electrical nuances is required.
Why do we need automatics?
Circuit breakers - devices designed to protect power cable, more precisely, its isolation from melting and integrity violations. Automatic machines do not protect the owners of equipment from shock and do not protect the equipment itself. For these purposes, an RCD is equipped. The task of the automata is to prevent overheating, which accompanies the flow of overcurrents to the entrusted section of the circuit. Thanks to their use, the insulation will not be melted and damaged, which means that the wiring will operate in normal mode without fire hazards.
The operation of circuit breakers is to open the electrical circuit in the event of:
- the appearance of TKZ (further short-circuit currents);
- overload, i.e. passage through the protected section of the network of currents, the strength of which exceeds the permissible operational value, but is not a TKZ;
- a noticeable decrease or complete disappearance of tension.
The automata guard the section of the chain following them. In other words, they are set on the input. They protect the lines of lighting and sockets, the mains for connecting household equipment and electric motors in private homes. These lines are laid with a cable of various sections, because equipment is powered by them different power. Therefore, to protect network sections with unequal parameters, protection devices with unequal capabilities are needed.
If you want to know how to install socket boxes, we advise you to read the article
It would seem that it is possible, without too much trouble, to purchase the most powerful automatic shutdown devices for installation on each of the lines. The step is fundamentally wrong! And the result of it will lay a direct "path" to the fire. Protection against the vagaries of electric current is a delicate matter. Therefore, it is better to learn how to choose a circuit breaker, and install an apparatus that breaks the circuit when a real need arises.
Attention. An oversized circuit breaker will carry currents that are critical to the wiring. It will not turn off the protected section of the circuit in a timely manner, due to which the cable insulation will melt or burn.
Automatic machines with underestimated characteristics will also present a lot of surprises. They will endlessly break the line when the equipment is started and eventually break due to repeated exposure to too large currents. Contacts are soldered, which is called "sticky".
The design and principle of operation of the machine
It will be difficult to make a choice without understanding the circuit breaker device. Let's see what is hidden in a miniature box made of refractory dielectric plastic.
Releases: their types and purpose
The main working bodies of automatic switches are releases that break the circuit in case of exceeding the standard operating parameters. The releases differ in the specifics of their action and in the range of currents to which they must respond. Their ranks include:
- electromagnetic releases, almost instantly responding to the occurrence of TKZ and "cutting off" the protected section of the network in hundredths or thousandths of a second. They consist of a coil with a spring and a core, which is drawn in by the action of overcurrents. Retracting, the core strains the spring, and it makes the release device work;
- thermal bimetal releases acting as an overload barrier. They undoubtedly also react to TKZ, but they are required to perform a slightly different function. The task of thermal counterparts is to break the network in the event that currents flow through it that exceed the maximum operating parameters of the cable. For example, if a 35A current flows through the wiring intended for transportation of 16A, the plate consisting of two metals will bend and cause the machine to turn off. Moreover, she will courageously “hold” 19A for more than an hour. But 23A will not be able to “endure” for an hour, it will work earlier;
- semiconductor releases are rarely used in household machines. However, they can serve as a working body safety switch at the input to private house or on the line of a powerful electric motor. The measurement and fixation of the anomalous current in them is carried out by transformers, if the device is installed on the network alternating current, or choke amplifiers if the device is connected to a DC line. Disengagement is carried out by a block of solid-state relays.
There are also zero or minimum releases, most often used as an addition. They disconnect the network when the voltage drops to any limit value specified in the data sheet. A good option are remote releases that allow you to turn off and turn on the machine without opening the control cabinet, and locks that fix the “off” position. It is worth considering that equipping with these useful additions significantly affects the price of the device.
Automatic machines used in everyday life are most often equipped with a well-functioning combination of an electromagnetic and thermal release. Devices with one of these devices are much less common and used. However, circuit breakers combined type more practical: two in one is more profitable in every sense.
Extremely important additions
There are no useless components in the design of the circuit breaker. All components work diligently in the name of a common safety cause, these are:
- an arcing device mounted on each pole of the machine, of which there are from one to four pieces. It is a chamber in which, by definition, the electric arc that occurs when the power contacts are forced to open is extinguished. Copper-plated steel plates are located in parallel in the chamber, dividing the arc into small parts. The fragmented threat to the fusible parts of the machine in the arc extinguishing system cools down and completely disappears. Combustion products are discharged through gas outlet channels. An addition is a spark arrester;
- a system of contacts, subdivided into fixed, built into the housing, and movable, pivotally attached to the semi-axes of the levers of the opening mechanisms;
- calibration screw, with which the thermal release is adjusted in the factory;
- a mechanism with a traditional inscription "on / off" with the corresponding function and with a handle intended for implementation;
- connection terminals and other devices for connection and installation.
Here is what the process of extinguishing the arc looks like:
Let's dwell a little on the power contacts. The fixed version is brazed with electromechanical silver optimizing the electrical durability of the switch. When an unscrupulous manufacturer uses a cheap silver alloy, the weight of the product decreases. Sometimes silver plated brass is used. “Substitutes” are lighter than standard metal, therefore a high-quality device of a reputable brand weighs somewhat more than the “left” counterpart. It is important to note that when replacing the silver soldering fixed contacts with cheap alloys, the resource of the machine is reduced. It will withstand less cycles of shutdown and subsequent inclusion.
Decide on the number of poles
It has already been mentioned that this protection device can have from 1 to 4 poles. Choosing the number of poles of the machine is as easy as shelling pears, because it all depends on its purpose of use:
- a single-pole machine will perfectly cope with the protection of lighting lines and sockets. Mounted only on the phase, no zeros!;
- a two-pole switch will protect the cable that feeds the electric stoves, washing machines and water heaters. If powerful household appliances not in the house, they put it on the line from the shield to the entrance to the apartment;
- a three-pole device is required for three-phase wiring equipment. This is already semi-industrial scale. In everyday life there may be a workshop line or well pump. A three-pole device must not be connected to a ground wire. He must always be in full combat readiness;
- four-pole circuit breakers are used to protect four-wire wiring from fire.
If it is planned to protect the wiring of an apartment, bath, house with the help of two-pole and single-pole circuit breakers, a two-pole device is installed first, then a single-pole device with a maximum rating, then in descending order. The principle of "ranking": from a more powerful component to a weak, but sensitive one.
Marking - information for reflection
We figured out the device and the principle of operation of the machines. Learned why. Now let's boldly proceed to the analysis of the markings affixed to each circuit breaker, regardless of the logo and country of origin.
The main reference point is the denomination
Because the purpose of acquiring and installing the machine is to protect the wiring, then first of all you need to focus on its characteristics. The current flowing through the wires heats the cable in proportion to the resistance of its current-carrying core. In short, the thicker the vein, the greater value current can pass through it without melting the insulation.
In accordance with the maximum value of the current transported by the cable, the rating of the device is selected automatic shutdown. You don’t need to calculate anything, the interdependent values \u200b\u200bof electrical installation devices and wiring by caring electricians have long been summarized in the table:
Tabular information should be somewhat adjusted according to domestic realities. The prevailing number of household sockets is designed to connect a wire with a core of 2.5 mm², which, according to the table, implies the possibility of installing a machine with a rating of 25A. The real value of the outlet itself is only 16A, which means you need to buy a circuit breaker with a rating equal to the rating of the outlet.
A similar adjustment should be made if there is any doubt about the quality of the existing wiring. If there is a suspicion that the cable cross-section might not correspond to the size specified by the manufacturer, it is better to play it safe and take an automatic machine, the nominal value of which is one position less than the table indicator. For example: according to the table, an automatic machine for 18A is suitable for protecting the cable, and we will take it for 16A, because we bought the wire from Vasya on the market.
Calibrated characteristics of the nominal value of the device
This characteristic is the operating parameters of the thermal release or its semiconductor counterpart. It is a coefficient, by multiplying by which we get the current strength during overload, which the device may or may not hold for a certain period of time. The value of the calibrated characteristic is set during the production process, it is not subject to adjustment at home. Pick it up from the standard range.
The calibrated characteristic indicates how long and what kind of overload the machine can withstand without disconnecting the circuit section from the power supply. Usually these are two numbers:
- the smallest value indicates that the machine will pass current with parameters exceeding the standard for more than an hour. For example: a 25A machine will pass a current of 33A for more than an hour without disconnecting the protected section of the wiring;
- the largest value is the limit beyond which the shutdown will occur in less than an hour. The device specified in the example will quickly turn off at a current of 37 or more amperes.
If the wiring runs in a strobe formed in a wall with impressive insulation, the cable will practically not be cooled during overload and the accompanying overheating. So, in an hour, the wiring can be badly damaged. Maybe no one will immediately notice the result of the excess, but the service life of the wires will be significantly reduced. Therefore, for concealed wiring we will look for a switch with minimum calibration characteristics. For the open version, you can not particularly dwell on this value.
Setpoint - indicator of instantaneous operation
This figure on the case is a characteristic of the operation of the electromagnetic release. It indicates the limiting value of the anomalous current strength, which, with repeated shutdowns, will not affect the performance of the device. It is normalized in units of current, and is indicated in numbers or Latin letters. With numbers, everything is extremely simple: this is the face value. But the hidden meaning of the letter designations is worth finding out.
Letters are affixed on machines made according to DIN standards. They denote the multiplicity of the maximum current that occurs when the equipment is turned on. A current that is several times higher than the operating characteristics of the circuit, but does not cause a shutdown and does not render the device unusable. It is simpler, how many times the switching current of the equipment can exceed the rating of the device and cable without threatening consequences.
For circuit breakers used in everyday life, these are:
- AT- designation of automata capable of responding without their own damage to currents exceeding the nominal value in the range from 3 to 5 times. Very suitable for equipping old buildings and countryside. They are not often used, therefore for the distribution network they are most often a custom item;
- With- designation of these protective equipment, the operating range of which is in the range from 5 to 10 times. The most common option, in demand in new buildings and in new country houses with autonomous communications;
- D- the designation of switches that instantly break the network when a current flows with a force exceeding the nominal value from 10 to 14, sometimes up to 20 times. Devices with such characteristics are needed only to protect the wiring of powerful electric motors.
There are variations abroad, both up and down, but they should not be of interest to the average owner of domestic property.
Current limiting class and its meaning
This is brief, because most of the devices offered by the trade belong to the 3rd class of current limitation. Occasionally meets the 2nd. This is an indicator of the speed of the device. The higher it is, the faster the device will respond to TKZ.
There is a lot of information, but without it it will be difficult to choose the right circuit breaker and protect property from unwanted fires. Information is also needed for those who will order the installation of protection devices. After all, not every electrician who positions himself as a great specialist should be unconditionally trusted.
Circuit breakers are not at all like the usual ones that are installed in every room to turn the light on and off (Fig. 1). Their task is somewhat different. Circuit breakers are installed in switchboards and serve to protect the circuit from power surges and non-periodic power outages in certain sections of the power grid.
Rice. one.
Automata, as they are often called, are installed at the entrance to a house or apartment and are located in special boxes, metal or plastic (Fig. 2).
Rice. 2. Distribution board with automatic machines
There are many types of circuit breakers. Some of them serve only as circuit breakers and protect the network from overload. Such are, for example, the old AE type circuit breakers in a black carbolite case (Fig. 3).
Rice. 3. AE series circuit breaker
In most old shields in the entrances of residential buildings there are just such. However, they are quite reliable and are still in operation.
Modern variations allow additional functions, such as undercurrent protection.
According to the response time to an unacceptable voltage, the automata are divided into 3 types: selective, normal and high-speed. The response time of a normal machine ranges from 0.02 to 0.1 s. In selective circuit breakers, this time is the same. High-speed circuit breakers work faster - they have this value is only 0.005 s.
All circuit breakers are enclosed in a plastic unbreakable case with a special fastening (bar or rail) on the rear plane. Installing the machine on such a mount is very easy - just insert it on the rail until it clicks. You can remove it with a screwdriver by gently pulling on the special tab on top of the circuit breaker. This greatly simplifies the task of installing the machine in a cabinet (Fig. 4).
Rice. 4.
Inside the case is the "stuffing" of the machine, its main safety devices, which can be 2 (Fig. 5).
Rice. 5. Internal
We are talking about electromagnetic and thermal releases - peculiar mechanisms for automatically breaking the circuit. A bimetallic plate, when heated by an unacceptably high current passing through it, straightens and opens the contacts - this is a thermal release. In terms of response time, it is the slowest.
The electromagnetic release operates according to the "dead hand" rule. The coil located in the center of the machine is continuously kept in place by a stable voltage. As soon as he jumps out of the nominal limits, the coil literally jumps out of its place, breaking the circuit. This way of breaking the chain is the fastest.
All circuit breakers have contacts for connecting incoming and outgoing wires (Fig. 6).
Rice. 6. Wires are connected to the contacts of the circuit breaker using screw terminals
Automata are distinguished by the degree of sensitivity to tripping. In the standard most common models, circuit breakers with a threshold value approximately equal to 140% of the nominal are most often used. With an increase in voltage by one and a half times, an electromagnetic (fast) release is triggered. With a slight excess of the rated voltage, the thermal release operates. The shutdown process can take hours, which is highly dependent on the ambient temperature. However, the machine will react to voltage changes in any case.
Circuit breakers are distinguished by the number of poles. What does it mean? In one machine there can be several electrical lines independent of each other, which are interconnected by a common shutdown mechanism (Fig. 7 and 8). Automatic machines are one-, two-, three- and four-pole (this applies to domestic use).
Rice. 7. in a plastic box in the off state
Rice. 8. : all lines are triggered at the same time when disconnected, they are connected together with one lever jumper
The circuit breaker has differences in other indicators. They differ in the threshold current strength that they pass through themselves. In order for the machine to work in emergency turn off the mains, it must be set to a certain sensitivity threshold. This setting is made by the manufacturer, so the machine immediately writes the numerical value of this threshold. For domestic needs, machines with indicators of 6.3, 10, 16, 25, 32, 40, 63, 100 and 160 A are used (Fig. 9). There are machines with values of both 1000 and 2600 A, but they are not used in everyday life. These figures mean the total power of all consumers electric current, which will be connected to the circuit, "guarded" by the machine.
Machine sensitivity it is necessary to calculate not only by the total power of the proposed energy consumers, but also by wiring and electrical installation products - sockets and switches.
Table 1 shows the typology of automata.
Table 1. Types of machines
| Type | Purpose |
| A | For opening circuits with a large length of electrical wiring and protecting semiconductor devices |
| B | For lighting networks of general purpose |
| C | For lighting circuits and electrical installations with moderate starting currents (motors and transformers) |
| D | For circuits with active-inductive loads, as well as protection of electric motors with high starting currents |
| K | For inductive loads |
| Z | For electronic devices |
Table 2. Two-core copper cable laid in a conduit
| Section, mm2 | Cable current/1.45, A | Automatic, A | Excess current, % | |
| 1,5 | 19 | 13,1 | 13 | - |
| 2,5 | 27 | 18,62 | 16 | - |
| 4 | 38 | 26,2 | 25 | - |
| 6 | 50 | 34,48 | 32 | - |
| 10 | 70 | 48,27 | 40(50) | 3,5 |
| 16 | 90 | 62,06 | 50(63) | 1,5 |
Table 3. Two-core copper wire laid in a box
| Section, mm2 | Maximum continuous cable current, A | Cable current/1.45, A | Automatic, A | Excess current, % |
| 1 | 15 | 10,34 | 10 | - |
| 1,5 | 18 | 12,41 | 10(13) | 4,7 |
| 2 | 23 | 15,86 | 13(16) | 0,87 |
| 2,5 | 25 | 17,24 | 16 | - |
| 4 | 32 | 22,06 | 20 | - |
| 6 | 40 | 27,58 | 25 | - |
| 10 | 48 | 33,1 | 32 | - |
| 16 | 55 | 37,93 | 32(40) | 5,4 |
The maximum continuous current of the cable is assumed for core temperature +65 and air +25 °C. The number of simultaneously laid conductors is up to 4. A number of automatic machines: 0.5 A, 1 A, 2 A, 3 A, 4 A, 6 A, 10 A, 13 A, 16 A, 20 A, 25 A, 32 A, 40 A, 50 A and 63 A. Data in Table. 3 are also suitable for a three-core cable. In this case, the third core must be a wire protective earth or nulls.
Rice. 9. A row of 16 A single-pole automata. Let's say for a separate section in an apartment, for example, a kitchen, we have one 6.3 A automaton (it happens, too - the electricians were joking). According to the well-known formula Watt \u003d Volt x Ampere, we calculate how many devices (and which ones) can be powered from our network. It turns out that this value is equal to 1386 W, since the default voltage is 220 V. This means that even a powerful kettle cannot be turned on in such a kitchen, not to mention a refrigerator or electric stove - the machine will work instantly and will not allow unacceptable, in its opinion, current to pass through controlled territory. In this case, it is urgent to change the circuit breaker to 25 or even 32 A.
Installation of protective equipment is an important stage in the construction of electrical networks. In the event of the occurrence of large currents, heating occurs, causing the melting of the insulating layer of the conductor. This situation leads to a fire. A sharp increase in the magnitude of the current is associated with a short circuit that occurs during the operation of faulty equipment.
In order to avoid the threat of fire and damage to wires, various types of electric machines are used, depending on the parameters used in conjunction with electrical devices.
Principle of operation and varieties
The principle of operation of electrical switches is to break the electrical circuit when a short circuit occurs. Or exceeding the permissible power for which the electrical network is designed. Electric circuit breakers are always located at the beginning of the protected section of the circuit. In this case, the type of connected load does not matter.
According to their form and parametric values, automata are divided into:
- by the number of poles;
- according to the time-current characteristic;
- by rated current.
It is also necessary to note the current limiting class. This value is characterized by the speed of the device's response to an emergency situation. The division is into three classes. For domestic use, the third class is used.
Regardless of their characteristics, the principle of operation for all switches is identical. To connect the machine to the electrical network, it is necessary to set the control switch to the "on" position. The current flowing to the switch is fed through the input terminal to the solenoid coil, and from it to the bimetallic plate. The plate is a strip of two pressed metals with different coefficients of thermal linear expansion. The current from the plate comes to the output terminal and then enters the electrical circuit. The plate and solenoid are called releases.
Current release - important element designs, it can be:
- electromagnetic (solenoid);
- thermal (bimetallic plate);
- combined (combination of thermal and electromagnetic);
- independent (remotely acting on the switch, it turns off).
There are two conditions under which the electrical switch will trip to open the line: overload mode and short circuit mode.
The principle of operation in overload mode is based on the ability of a bimetallic strip to bend under the influence of heat. With an increase in power to the line, the current flowing through the electric machine increases, exceeding the working value switch. As a result, the release heats up, its plate bends, and the contact breaks. Accordingly, the electrical circuit is broken. The current supply is stopped. The amount of current at which the plate breaks the contact is set at the factory with an adjustment screw. After the plate has cooled, it returns to its previous shape, and the contact appears again.
In the short circuit mode, the current increases very quickly, the magnetic field formed by it in the solenoid sets the core in motion. The core acts on the release, and the electrical circuit breaks, and an arc appears. The appearance of an arc negatively affects the internal parts of the machine, therefore, a device for extinguishing it is used. The arc chute is made of plates parallel to each other, passing through which the arc dissipates.
Thus, the main structural parts can be noted:
- current terminals;
- release:
- control lever;
- release adjusting screw;
- arc chamber.
Number of poles
The number of poles indicates how many wires can be passed through the switch at the same time. There are devices with the number of outputs from one to four. The device of a single-pole switch is no different from a multi-pole one, only in the second case, when the passage of electric current several chains are broken at the same time.
Single-pole devices are more often used in domestic conditions and are placed in a break in the phase wire, the zero one is connected directly through the block, as an introductory machine, its use is not recommended. For installation at the entrance, two-pole circuit breakers are used, the phase and neutral wires are connected to them at the same time. For use in a three-phase network, a three-pole machine is already used as an input. To protect a four-phase electrical network, for example, a star-connected motor, a four-phase automatic machine is used. In this case, three phase and one neutral wire are connected.
The usual scheme for building protection on electrical switches comes down to installing an input automaton of the required number of poles. After it, single-pole ones are installed - one for each group. In this case, the value of the rated current of a single-pole machine is already calculated based on the parameters of the group to which it is connected. Its value is chosen less than the input value.
Time-current characteristic
This parameter indicates the ratio of the actual current flowing through the machine to the nominal value. Depending on the value of the ratio, the sensitivity of the automaton is determined, which is characterized by the number of false positives. There are machines various kinds. They are marked with letters of the Latin alphabet. The most common switches are labeled B, C and D.
Electric machines with characteristic B are switched off within 5-20 seconds. In this case, the current value can exceed the nominal value by five times. These models are widely used in household premises. Marking C means switching off interval 1-10 seconds, while the load is ten times the value. Class D circuit breakers are used to protect engines. The operating current exceeds the nominal by 14−20 times.
Rated current
Indicates the amount of current that can pass through an electric machine without it tripping. Strictly defined values \u200b\u200bare produced from 1 to 63 amperes. There are 12 values in total: 1A, 2A, 3A, 6A, 10A, 16A, 20A, 25A, 32A, 40A, 50A, 63A.
The choice of rated current depends on the power value that the wiring can withstand without damage. This value is determined by the cross section of the wire and the material of its manufacture. In homes, the most popular machines for use are 6A, 10A and 16A. Automatic machines with a nominal value of 20A, 25A, 32A are used in apartments as introductory, i.e., two-pole.
Location and accommodation
The method of placement (whether it is a single-phase electric machine or another type) is strictly vertical. The fixed part of the control lever must be on top, i.e. the device is switched on by switching from bottom to top. Devices are placed in accessible places, and the possibility of their mechanical damage is excluded.
DIN rail mounting is the most popular. Usually such a rail is installed in the shield. Electrical switches structurally have special grooves into which the rail is inserted.
What are the machines, how are they marked - you need to know this information in order to choose the right device. Regardless of the manufacturer and type of electric machines, they are always marked on front side. Marking is carried out according to a single scheme. It includes an indication of all the main parameters:
On the control lever, inscriptions are made indicating the set position - “on.” and "off" or "1" and "0".
Leading brands and manufacturers
The leaders in the production of circuit breakers are the following brands:
This is famous brands, producing any kind of automatic machines. They are characterized by high quality housing, long service life and high mechanical strength. Often, protective covers are additionally installed on them. These manufacturers produce their devices from solid materials. Their quality is confirmed by certificates and a warranty period given by manufacturers for their products.
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