The circuit breaker is used for switching and protection. It is a mechanical connection device capable of establishing, supporting and interrupting currents under normal conditions, as well as supporting and breaking short-circuit currents for a period of time. Due to its high breaking capacity, it can automatically disconnect overload or short-circuit currents before harmful effects occur.
Automatic switches are essential devices in the modern world, and one of the most important security mechanisms in any house, building or industry. When an electrical wiring in a building has too much current, these simple items cut it off until someone fixes the problem.
Unlike fuses, which are single-use, a circuit breaker or electrical breaker can be reconnected as long as the causes that activated it have been resolved. In this way they assume the protection of electrical means against excessive heating. Each of the circuits that are installed has its own thermomagnetic circuit breaker. They are designed to withstand the current peaks that are generated during the start-up of electric motors.
They can be divided into two large groups: those called “Small Automatic Switches” or PIAs and those simply called “Automatic Switches” or IAs.
It is the small automatic switch (PIA), used in Low Voltage.
How Circuit Breaker Protects Circuits
The circuit breaker protects electrical circuits against overloads (thermal) and short circuits (magnet).
· In case of overload, the deformation of the bimetallic sheet by heat causes the contacts to open. thermal effect.
· In the event of a short circuit, the current that passes through the solenoid has a magnitude such that it produces the displacement of the core, which in turn causes the opening of the contacts. Cut by magnetic effect.
The thermal mechanism or device consists of a sheet made of two metals with different expansion coefficients (bimetallic pair) that deforms due to the heat produced by the passage of current. When the current is intense enough, the deformation reaches the point of activating the switch mechanism, activating the protection and interrupting the flow of current. The heating and deformation of bimetallic are slow processes, so this mechanism is appropriate to respond to current overload.
The magnetic mechanism or device is connected in series with the thermal one, so that both are crossed by the same current. It consists of a coil wound on a core of magnetic material, constituting an electromagnet. The passage of current produces a magnetic field that displaces the core of the electromagnet like the latch of an electric doorman. If the current is strong enough, the core drives the mechanism and the switch opens. This happens without delay, so this mechanism is capable of responding to short circuits.
Circuit Breaker Ratings
Circuit breakers can be classified based on multiple criteria, such as:
1. According to its function of use:
Power switches. They are those that are installed in the connection of an electrical panel from a transformer, a generator, another panel, etc. They must be coordinated with the distribution and load power switches to guarantee the selectivity of the protections.
· Distribution Switches. They protect the conductors that connect the panel with another point of the installation.
· Consumer Switches. In this case, the protection is direct, since it is located as close as possible to the load.
2. Depending on the type of use:
· Industrial use
· Domestic use.
3. According to its construction type:
· Modular automatic switches. Commonly called PIA (small automatic switch), they are typically used for final consumption, nominal current values up to 50 or 63 A, and low breaking capacities.
· Molded case switches. They are more robust than modular circuit breakers, they are used for currents up to around 1000 A, and higher breaking capacities.
· Air cut-off switches. Its use applies to the highest currents, up to around 6300 A, with the highest breaking powers. It is usually typical to use them in switchboards that exchange great power, or in their connections.
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