The 25 Amp modular circuit breaker performs several functions in electrical circuits. First, it protects them against overloads and short circuits. Secondly, with its help, linear circuits are connected to and disconnected from loads. They are called modular because the devices are produced in the form of single-pole blocks, from which complex multi-pole devices are assembled. To understand the purpose of machines for 25 Amperes, familiarization with their technical characteristics will help.
General characteristics and markings
Electrical equipment operating in power circuits is represented by technical characteristics and standard markings. A number of parameters determining the operation of the automatic device are taken as a basis.
Main factors
The functionality of any protective device is determined by:
- rated current;
- switching or breaking capacity;
- current limiting class;
- time-current characteristics of electromagnetic and thermal releases.
Taken together, these indicators fully characterize it, and some of them are used in the factory marking.
Extra options
- permissible load power that the machine can withstand;
- type of switched voltage (220 or 380 volts);
- number of poles.
In contrast to the main indicators relating directly to the circuit breaker, these parameters characterize the device by its operation in the serviced circuit. According to them, it is possible to distinguish a three-phase 25 Ampere machine, for example, from its single-phase counterpart.
According to the number of poles, the devices are:
- single-pole;
- bipolar;
- three-pole and four-pole.
Each of them has a corresponding number of inlet and outlet contacts and is used for specific purposes. Single-pole circuit breakers are installed in 220 Volt phase power circuits (the earth core is not involved, since it is routed bypassing the switch). Two-pole circuit breakers 25 Amperes are needed for the simultaneous switching of the phase and ground wires and are used to organize the input into the apartment.
More functional 3-pole products are used in three-phase circuits (without a zero core). A 4-pole device is selected when it is necessary to switch three phases and zero.
PUE allows the use of poles of machines for controlling currents of various linear loads. The situation is not excluded when a phase is supplied to one of them from one line, and to the other - from the second.
Marking
The marking applied to the C25 machine informs about the following device parameters:
- The "C" symbol stands for a current characteristic indicating the trip time delay.
- Digits 25 - rated current at which the machine works for a long time without overloads (in normal mode).
Below the marking on the front panel of the device, symbols are applied within the boxes indicating the current limiting class and the rated breaking capacity.
Description of the main parameters
The switching capacity of the machine characterizes its ability to instantly turn off at short-circuit currents of a certain magnitude. This indicator for household appliances takes typical values of 4.5 thousand or 6 thousand Amperes. In industrial designs, it is indicated separately (without a square frame). The higher the switching capacity of the model, the better the machine is considered to be and the more expensive it is.
The current limiting class indicates how long it takes to extinguish the arc that occurs when switching high currents. There are 3 classes of switches that differ in this parameter:
- In the third grade, the arc extinguishes in 3-5 milliseconds.
- In devices of the second group, it takes 5-10 milliseconds to extinguish it.
- For devices of the first class, the limitation is not standardized. The process usually takes 10 milliseconds or more.
The class marking is applied to the case in the form of numbers 3 or 2, placed in a frame.
In any machine, two releases are used as actuators. One of them (thermal type) is made as a bimetallic plate, and the other is electromagnetic, which is an overcurrent relay. The first turns off the device when the current power is exceeded for a long time in the section of the line protected with it. The electromagnetic release is triggered by a short circuit in the circuit. The values of the currents at which the machine turns off, as well as the time delays are called its time-current characteristics.
Applications and wiring diagram
Two-pole and 4-pole circuit breakers for 380 Volts 25 Amperes are most often installed at the input of the serviced object, before the meter.
For input devices, the permissible power is no more than 5.5 kilowatts (kW) for a single-phase network and no more than 9.5 kW for a 3-phase 25A machine.
Single-pole and double-pole devices are allowed to be used in the power circuits of individual consumers with a capacity of up to 5.5 kW, if only the input automatic device has a higher current rating. Their 3-pole and 4-pole counterparts can be installed if it is necessary to protect the circuits of current collectors with a capacity of up to 9.5 kW (electric stoves and similar heating devices). Before installing the machine for 25A 380V, it is necessary to calculate the permissible load, summing up the indicators for individual consumers. In this case, it is important to take into account the thickness of the supplied wires. The cable cross-section is determined according to the tables in which the required value is selected in accordance with the operating current of this device.
According to the PUE, protective devices, in the designation of which there is the letter "C", are calculated according to formulas for averaged characteristics and are considered universal. They can work in a network to which various types of loads are connected (from a light bulb to an electric motor).
Connection diagram
When connecting any machine, it is important to learn the following rule: the wires to it are always supplied from the side of the upper terminals, and taken off from the bottom and go further to the load. There are exceptions to this rule; but then on the body of the device its special switching circuit is shown.
In a situation where, in addition to the numbers on the diagram or on the contacts of the machine, there is the letter N, a zero bus is connected to these terminals. If there is no designation on the case, it is connected to the contacts indicated by the last numbers. Phase and neutral conductors are always connected on the same side.
It is important to know the procedure for connecting the device to the general power supply circuit. It is always installed before the RCD, since it requires a phase conductor and ground for normal operation, and the linear machine switches one phase. However, they are usually mounted on a common DIN rail located in the switch cabinet next to the meter.
Manufacturing companies and brands
Before choosing and buying a C25 circuit breaker, you should familiarize yourself with the companies that represent them and the price. Famous appliance manufacturers:
- The Swedish-Swiss company ABB, rightfully considered the leader in the market for electrical products of this class.
- Automatic switches from Legrand (France) are not inferior in quality to the previous brand, the costs are approximately comparable in value.
- Products of another French company (Schneider Electric) are well known to the domestic consumer, who speaks very well about this product.
The price of the C25 machine in the domestic market ranges from 100 rubles. up to 100 thousand rubles depending on the number of poles, firm and brand.
