Marking of circuit breakers. Types, characteristics and purpose of circuit breakers

Compared to conventional switches, automatic switches are placed in switch cabinets and are designed to protect 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 complete 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 marking is deciphered as follows: 20 - development, 4 - 63 A, 4 - single-pole with a thermal and electromagnetic release. Devices differ in the characteristic black color of the carbolite case.

The labeling scheme for automatic machines is standardized. Its main purpose is the most understandable to bring to the attention of users the basic parameters of the device.

The marking of the circuit breakers is read from the top to the bottom.

1. The manufacturer or trademark is Schneider, ABB, IEK, EKF.
2. The serial or catalog number (series AB200 S200U, SH200).
3. Time-current characteristic (A, B, C) and nominal in amperes (I _nom. ).
4. Rated voltage.
5. The maximum permissible values of the tripping currents at the kc.
6. Class of current limitation.
7. The article of the manufacturer, by which you can find this type of machine by catalog.

The picture below shows how the ABB and Schneider circuit breakers are labeled.

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

1. The temperature range for conventional models is in the range of -5 ° C to +40 ° C. To work beyond these limits, special models are produced.
2. It is allowed to operate the equipment 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. Two-pole automatic device

Structurally the device is a block of two unipoles connected by a lever. The interlock between the shutdown mechanisms is designed so that the phase is turned off before the zero (according to the rules of the SAE).

3. Three-pole automatic device

The device serves to simultaneously disconnect the power of the 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 casings of most machines, you can see the uppercase Latin letters B, C, D. The marking of the circuit breakers B, C, D denotes a characteristic reflecting the dependence of the response time of the machine on the ratio K = I / I _nom .

1. B - thermal protection is triggered after 4-5 seconds when the nominal value is exceeded by 3 times, and electromagnetic protection is triggered after 0.015 sec. The devices are designed for loads with small values of starting currents, in particular for lighting.
2. C - the most common characteristic of machines that protect electrical installations with moderate starting currents.
3. 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 automata

1. MA - without thermal release. If a current relay is installed in the circuit, it is sufficient to install the circuit-breaker only with short-circuit protection.
2. A - the thermal release trips when I exceeds the _{nominal value.} In 1,3 times. The shutdown time can be up to 1 hour. If the rating is exceeded by 2 times or more, the current release releases after 0.05 s. In case of failure of this protection, overheat protection operates after 20-30 seconds. The automatic device with characteristic A is used to protect the electronics. Devices with characteristic Z are also used here.

Criteria for the selection of automata

1. I _nom. - exceeding which leads to the activation of the overload protection. The nominal is selected according to the allowable maximum current of the wiring, and then reduce it by 10-15%, choosing it from the standard series.
2. 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.
3. Selectivity is a feature of selective shutdown. The automatics are selected according to the rated current, so that the devices on the load side first of all operate. First of all, the protection is disconnected in places where short circuits occur or the network is overloaded. The time selectivity is selected in such a way that the response time is longer for the machine closer to the power supply.
4. Number of poles. The three-phase input is connected to an automatic device with four poles, and to a single-phase input with one or two. Lighting and household appliances operate on single-pole networks. If the house has an electric boiler or a three-phase electric motor, three-pole automata are used for them.

Other options

When a circuit-breaker is purchased, the characteristics must be selected in accordance with the operating and connection conditions. Each machine is designed for a certain number of cycles of operation. As a load switch it is not recommended to use it. The number of machines is selected as necessary. It is mandatory to install the introductory, and after it - on the lighting line, sockets and separately to powerful consumers. Mounting methods for different models may vary. Therefore, devices similar to those in the cabinet are selected.

Conclusion

Marking of circuit breakers is required to select them in accordance with specific needs. Their characteristics are directly related to the section of the wiring and the types of load. In case of short circuits, first of all, electromagnetic releases are activated, thermal overload is provided for prolonged overloads.