По сравнению с обычными выключателями automatic are placed in the distribution cabinets and are designed to protect the electrical wiring against short circuits and overloads during power surges. The marking of the circuit breakers on the housing contains their main characteristics. On them you can get a full picture of the device.
Circuit breakers: marking and symbols
There are many types of machines, for example, the old type - AE20XXX.
For example, for the AE2044 machine, the markingis deciphered as follows: 20 - development, 4 - 63 A, 4 - single-pole with thermal and electromagnetic release. Devices differ in the characteristic black color of the carbolite body.
The labeling scheme for automatic machines is standardized. Its main purpose is to understand most clearly the basic parameters of the device.
The marking of the circuit-breakers is read from the top to the bottom.
- The manufacturer or trademark is Schneider, ABB, IEK, EKF.
- The serial or catalog number (series AB200 S200U, SH200).
- Time-current characteristic (A, B, C) and nominal in amperes (Inom.).
- Rated voltage.
- The maximum permissible values of the tripping currents at the output current.
- Class of current limitation.
- The article of the manufacturer, by which you can find this type of machine by catalog.
The picture below shows how to label the ABB and Schneider circuit breakers.
The disconnect button is marked or marked in red. If it is only one and is pressed, the depressed position means that the circuit is closed.
The marking of circuit breakers from the main manufacturers contains QR codes, where all information about the model is reflected. Their availability is a kind of quality guarantee.
The influence of environment
- The temperature range for conventional models is from -5 ° C to +40 ° C. To work beyond these limits, special models are produced.
- It is allowed to operate the apparatus at a relative humidity of up to 50% at 40 ° C. With decreasing temperature, the permissible humidity increases (up to 90% at 20 ° C).
Types of automata
Automatic machines are selected depending on the scheme of the electric system.
1. A single-pole automatic device
Devices are used in single-phase networks.The phase is connected to the upper terminal, and the load to the lower terminal. The device is connected to the phase wire break to disconnect the power from the load in the event of an emergency.
2. Double pole machine
Structurally, the device is a block of twounipoles connected by a lever. The interlock between the shutdown mechanisms is designed so that the phase is cut off before zero (according to the rules of the SAE).
3. Three-pole automatic device
The device is used for simultaneous shutdownsupply three-phase network in the event of an accident. The three-terminal network combines 3 single-pole networks with a setting for simultaneous operation. Electromagnetic and thermal releases are performed separately for each circuit.
Circuit Breaker: Specifications
Automatic machines can have different time-current characteristics:
a) current-dependent;
b) independent of the current;
c) two-stage;
d) three-stage.
On the cases of most machines you can seecapital Latin letters B, C, D. Marking of circuit breakers B, C, D denotes a characteristic reflecting the response time of the machine from the ratio K = I / Inom.
- B - thermal protection triggers after 4-5 s atexceeding the nominal value by 3 times, and electromagnetic - after 0.015 s. The devices are designed for loads with small values of the starting currents, in particular for lighting.
- C - the most common characteristic of machines that protect electrical installations with moderate starting currents.
- D - automatic machines for load with high starting currents.
The peculiarity of the time-current characteristic is that for identical values of the automata of types B, C and D, their disconnections will occur at different current excesses.
Other types of machines
- MA - without thermal release. If a current relay is installed in the circuit, it is sufficient to install a circuit breaker only with short circuit protection.
- A - thermal release trips when I is exceedednom. 1.3 times.At the same time off time can be 1 hour. If the nominal value is exceeded by 2 times or more, the current release trips in 0.05 s. In case of failure of this protection after 20-30 s overheating protection is valid. An automaton with characteristic A is used to protect the electronics. Devices with the Z characteristic are also used here.
Criteria for the selection of machines
- ANDnom.- exceeding of which leads to overload protection. The nominal value is selected by the allowable maximum wiring current, and then it is reduced by 10-15%, choosing it from the standard series.
- Tripping 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.
- Селективность - свойство избирательного shutdown. Automata are selected according to the rated current so that the devices on the load side work first. First, protection is disabled in places where short circuits occur or the network is overloaded. The time selectivity is chosen in such a way that the response time is longer for the automaton located closer to the power source.
- The number of poles.On a three-phase input connects the machine with four poles, and on the single-phase - with one or two. Lighting and household appliances work on the same network. If the house has an electric boiler or a three-phase electric motor, three-pole automatic machines are used for them.
Other options
When a circuit breaker is purchased,Characteristics must be selected according to the conditions of use and connection. Each machine is designed for a certain number of cycles of operation. It is not recommended to use it as a load switch. The number of machines is selected as needed. Be sure to set the introductory, and after it - on the line of lighting, outlets, and separately to powerful consumers. Attachment methods may vary by model. Therefore, devices similar to those installed in the cabinet are selected.
Conclusion
Marking of circuit breakers requiredto select them according to specific needs. Their characteristics are directly related to the wiring cross-section and types of load. In case of short circuits, the electromagnetic release opens first of all, during long-term overloads - thermal protection.
