Compared to conventional circuit breakers, automatic ones are placed in distribution cabinets and are designed to protect electrical wiring from short circuits and overloads during power surges. The marking of circuit breakers, applied to the case, contains their main characteristics. From them you can get a complete picture of the device.
Circuit breakers: marking and designations
There are many types of machines, for example, the old type - AE20XXX.
For example, for the AE2044 machine, the marking is deciphered as follows: 20 - development, 4 - 63 A, 4 - single-pole with thermal and electromagnetic release. The devices are distinguished by the characteristic black color of the carbolite body.
The marking scheme of machines is standardized. Its main goal is to convey the main parameters of the device to the attention of users in the most understandable way.
The marking of the circuit breakers is read on the case from top to bottom.
- Manufacturer or trademark - Schneider, ABB, IEK, EKF.
- Series or catalog number (ABB S200Y, SH200 series).
- Time-current characteristic (A, B, C) and rating in amperes (Inom.).
- Rated voltage.
- Maximum allowable tripping currents at short circuits
- Current limiting class.
- Manufacturer's article, by which you can find this type of machine in the catalog.
The picture below shows how ABB and Schneider circuit breakers are marked.
The opening button is marked or marked in red. If it is only one and is pressed, then the depressed position means that the circuit is closed.
The marking of circuit breakers from the main manufacturers contains QR codes, which reflects all information about the model. Their presence is a kind of guarantee of quality.
Environment influence
- The temperature range for conventional models is from -5 °C to +40 °C. Special models are available for operation outside these limits.
- Operation of devices is allowed at relative humidity up to 50% at 40 °С. With a decrease in temperature, the permissible humidity increases (up to 90% at 20 ° C).
Types of machines
Automatic machines are selected depending on the power grid.
1. Single pole machine
Devices are used in single-phasenetworks. The phase is connected to the top terminal, and the load is connected to the bottom. The device is connected to a break in the phase wire in order to disconnect power from the load in an emergency.
2. Bipolar machine
Structurally, the device is a block of two unipole connected by a lever. The blocking between the shutdown mechanisms is designed in such a way that the phase is switched off before zero (according to the rules of the PUE).
3. Three-pole circuit breaker
The device serves to simultaneously turn off the power of the three-phase network in the event of an accident. The three-terminal combines 3 unipoles with the setting for simultaneous operation. Electromagnetic and thermal releases are carried out separately for each circuit.
Circuit breaker specifications
Automatic machines can have different time-current characteristics:
a) current-dependent;
b) current-independent;
c) two-stage;d) three-stage.
On the cases of most machines you can see the capital Latin letters B, C, D. The marking of the circuit breakers B, C, D indicates a characteristic that reflects the dependence of the operation time of the machine on the ratio K=I/Inom.
- B - thermal protection is activated after 4-5 s when the nominal value is exceeded by 3 times, and electromagnetic - after 0.015 s. The devices are designed for loads with low inrush currents, in particular for lighting.
- C - the most common characteristic of slot machines,protecting electrical installations with moderate inrush currents.
- D - load breakers with high starting currents.
The peculiarity of the time-current characteristic lies in the fact that with the same ratings of automatic machines of types B, C and D, their trips will occur at different current excesses.
Other types of slot machines
- MA - no thermal release. If a current relay is installed in the circuit, it is sufficient to install a circuit breaker with only short-circuit protection.
- A - thermal release trips when Inom. is exceeded by 1.3 times. In this case, the shutdown time can be 1 hour. If the rating is exceeded by 2 times or more, the current release is activated after 0.05 s. If this protection fails, after 20-30 seconds, overheating protection operates. A machine with characteristic A is used to protect electronics. Devices with characteristic Z are also used here.
Criteria for choosing machines
- Inom.- exceeding which leads to the operation of overload protection. The rating is selected according to the permissible maximum wiring current, and then reduced by 10-15%, choosing it from the standard range.
- Trip current. The switching class of the circuit breaker is selected depending on the type of load. For domestic purposes, the most common characteristic is C.
- Selectivity is a property of selective shutdown. The machines are selected according to the rated current, so that in the first placedevices on the load side have been triggered. First of all, protection is turned off in places where short circuits occur or the network is overloaded. Time selectivity is selected so that the operation time is longer for the machine located closer to the power source.
- Number of poles. An automatic machine with four poles is connected to a three-phase input, and to a single-phase input - with one or two. Lighting and household appliances work on single-terminal networks. If the house has an electric boiler or a three-phase electric motor, three-pole machines are used for them.
Other options
When a circuit breaker is purchased, the characteristics must be selected according to the operating and connection conditions. Each machine is designed for a certain number of operation cycles. It is not recommended to use it as a load switch. The number of machines is selected as needed. Be sure to install an introductory, and after it - on the line of lighting, sockets and separately to powerful consumers. Mounting methods may vary for different models. Therefore, devices similar to those installed in the cabinet are selected.
Conclusion
Marking circuit breakers is required to select them according to specific needs. Their characteristics are directly related to the cross-section of the wiring and the types of load. In case of short circuits, electromagnetic releases are activated first of all, in case of prolonged overloads - thermal protection.
