An early form of circuit breaker was described by Thomas Edison in an 1879 patent application, although his commercial power distribution system used "Fuse (Electrical)" fuses.[2] Their purpose was to protect lighting circuit wiring from short circuits and accidental overloads. Brown, Boveri & Cie in 1924 patented a modern miniature circuit breaker similar to those now used. Hugo Stotz, an engineer who had sold his company to the BBC, was credited as the inventor in DRP (Deutsches Reichspatent) 458392.[3] Stotz's invention was the precursor to the modern thermomagnetic switch commonly used in domestic load centers to this day.

The interconnection of multiple generating sources on a power grid required the development of circuit breakers with increasing voltage ratings and increased ability to safely interrupt the increasing short-circuit currents produced by the grids. Simple manual air break switches produced dangerous arcs when interrupting high voltages; these gave way to oil-enclosed contacts and various forms that used the directed flow of pressurized air, or pressurized oil, to cool and interrupt the arc. In 1935, specially constructed circuit breakers used on the Boulder Dam project used eight series interruptions and pressurized oil flow to interrupt faults of up to 2500 MVA, in three cycles of the AC power frequency.[4]​.

The most important parameters that define a circuit breaker are:.

The most commonly used circuit breakers are those that work with alternating currents, although they also exist for direct currents. The most common types of circuit breakers are:.

The word relay is also used relatively frequently, although not completely correctly, to refer to these devices, especially thermal devices.

Colloquially, the name "automatic", "fuses", "plugs" or even "leads" is given to the magneto-thermal circuit breakers and the differential installed in homes.

In the case of railways, a circuit breaker is used to open and disconnect the main power line, cutting power directly from the pantograph to the rest of the train.

Thermal device

Present in thermal and magneto-thermal circuit breakers. It is composed of a calibrated bimetal through which the current that powers the load circulates. When this is higher than the intensity for which the device is built, it heats up, expands and causes the bimetal to arch, causing the switch to open automatically. Detects overload faults.

It is made up of a solenoid or electromagnet, whose attractive force increases with the intensity of the current. The contacts of the switch are kept in electrical contact by means of a latch, and, when the current exceeds the range allowed by the device, the solenoid releases the latch, separating the contacts by means of a spring. Some types of switches include a hydraulic delay system, immersing the solenoid core in a tube filled with a viscous liquid. The core is held with a spring that keeps it displaced with respect to the solenoid as long as the circulating current remains below the nominal value of the switch. During an overload, the solenoid draws the core through the fluid to close the magnetic circuit, applying enough force to release the latch. This delay allows brief increases in current beyond the nominal value of the device, without opening the circuit, in situations such as, for example, starting motors. The short circuit currents supply sufficient force to the solenoid to release the latch regardless of the position of the core, thus preventing delayed opening.

Magnetic device

Present in magnetic and magneto-thermal circuit breakers, it is made up of a coil, a core and a moving part. The intensity that powers the load passes through said coil, and if it is much higher than the nominal intensity of the device, a magnetic field is created that is capable of dragging the moving part and causing the circuit to open almost instantaneously. Detects short circuit faults that may exist in the electrical circuit.

Under short-circuit conditions, a current much greater than the nominal current flows; When an electrical contact opens a circuit where there is a large current flow, an electric arc is generally produced between said already open contacts, which allows the current to continue flowing. To avoid this, the switches incorporate features to divide and extinguish the electric arc. In small switches, an arc extinction chamber is implemented, which consists of several metal plates or ridges of ceramic material, which help lower the arc temperature. The arc is moved to this chamber by the influence of a magnetic blowing coil. In larger switches, such as those used in electrical substations, vacuum, inert gases such as sulfur hexafluoride or oil are used to weaken the arc.

The breaking capacity or breaking capacity of a switch is the maximum short-circuit current that it is capable of successfully breaking without suffering major damage. If the short circuit current is set to a value greater than the breaking capacity of a switch, the switch will not be able to interrupt it, and will be destroyed.

The small switches can be installed directly next to the equipment to be protected, although they are generally arranged in a panel designed for this purpose. Power switches are located in cabinets or electrical cabinets, while high voltage switches can be located outdoors.

Circuit breakers are rated both by the normal current they are expected to carry and by the maximum short circuit current they can safely interrupt. This last figure is the ampere interrupting rating (AIC) of the breaker.

Under short-circuit conditions, the maximum calculated or measured short-circuit current may be many times the normal rated current of the circuit. When electrical contacts are opened to interrupt a large current, there is a tendency for an arc to form between the open contacts, which would allow the current to continue. This condition can create conductive ionized gases and molten or vaporized metal, which can cause the arc to continue or create additional short circuits, which could cause the circuit breaker and the equipment on which it is to explode. is installed. Therefore, circuit breakers must incorporate several features to split and extinguish the arc.

The maximum short circuit current that a switch can interrupt is determined by testing. Application of a switch on a circuit with a potential short-circuit current greater than the interrupting capacity rating of the switch may cause the switch to fail to safely interrupt a fault. In the worst case, the switch may successfully interrupt the fault, only to explode when reset.

Typical home panel circuit breakers are rated to interrupt a short circuit current of 6 kA (6000 A).

Miniature circuit breakers used to protect control circuits or small appliances may not have sufficient interrupting capacity for use in a panel; These circuit breakers are called "supplementary circuit protectors" to distinguish them from distribution circuit breakers.

Several companies have considered adding monitoring for appliances through electronics or using a digital circuit breaker to monitor circuit breakers remotely. Utilities in the United States have been reviewing the use of the technology to turn appliances on and off, as well as potentially shutting down electric car charging during periods of high grid load. These devices under investigation and testing would have wireless capability to monitor electrical usage in a home through a smartphone app or other means.[5]​.

The following types are described in separate articles.

The differential circuit breaker is a protection element for people. It has a differential transformer (that is, it detects differences in current intensity), it has a magnetic core on which the phase is wound (for example, clockwise) and the neutral (in the opposite direction to the previous one), as well as a detection coil, which powers a small electromagnet, which triggers the trip. When the same amount of current flows through the phase as through the neutral (normal operation) the magnetic flux is zero, so in the detection coil the induced voltage "Voltage (electricity)") is 0 V; As soon as there is a leak to the ground (it can be through the third wire or a person), the total current flows through the phase, but only the total "leaves" through the neutral minus the amount that is being diverted to ground (this amount depends on each case), so if the difference is greater than the triggering value, the voltage at the ends of the detector winding is sufficient to activate the electromagnet that disconnects.

The thermal only protects the installation; Inside it has a bimetallic pair (two metals with different expansion coefficients) riveted at one end; When a current greater than the calibrated one circulates (circulates through the pair), one metal expands more than the other, bending the bimetallic pair, which activates the firing mechanism.

It is always advisable to place a thermal circuit breaker "upstream" of the differential circuit breaker, and that it be of a smaller caliber, since the circuit breaker is a more expensive element than the thermal circuit breaker. In addition to this, it is advisable to have one in every electrical installation and to press the test button once a month to verify its correct operation.

An early form of circuit breaker was described by Thomas Edison in an 1879 patent application, although his commercial power distribution system used "Fuse (Electrical)" fuses.[2] Their purpose was to protect lighting circuit wiring from short circuits and accidental overloads. Brown, Boveri & Cie in 1924 patented a modern miniature circuit breaker similar to those now used. Hugo Stotz, an engineer who had sold his company to the BBC, was credited as the inventor in DRP (Deutsches Reichspatent) 458392.[3] Stotz's invention was the precursor to the modern thermomagnetic switch commonly used in domestic load centers to this day.

The interconnection of multiple generating sources on a power grid required the development of circuit breakers with increasing voltage ratings and increased ability to safely interrupt the increasing short-circuit currents produced by the grids. Simple manual air break switches produced dangerous arcs when interrupting high voltages; these gave way to oil-enclosed contacts and various forms that used the directed flow of pressurized air, or pressurized oil, to cool and interrupt the arc. In 1935, specially constructed circuit breakers used on the Boulder Dam project used eight series interruptions and pressurized oil flow to interrupt faults of up to 2500 MVA, in three cycles of the AC power frequency.[4]​.

The most important parameters that define a circuit breaker are:.

The most commonly used circuit breakers are those that work with alternating currents, although they also exist for direct currents. The most common types of circuit breakers are:.

The word relay is also used relatively frequently, although not completely correctly, to refer to these devices, especially thermal devices.

Colloquially, the name "automatic", "fuses", "plugs" or even "leads" is given to the magneto-thermal circuit breakers and the differential installed in homes.

In the case of railways, a circuit breaker is used to open and disconnect the main power line, cutting power directly from the pantograph to the rest of the train.

Thermal device

Present in thermal and magneto-thermal circuit breakers. It is composed of a calibrated bimetal through which the current that powers the load circulates. When this is higher than the intensity for which the device is built, it heats up, expands and causes the bimetal to arch, causing the switch to open automatically. Detects overload faults.

It is made up of a solenoid or electromagnet, whose attractive force increases with the intensity of the current. The contacts of the switch are kept in electrical contact by means of a latch, and, when the current exceeds the range allowed by the device, the solenoid releases the latch, separating the contacts by means of a spring. Some types of switches include a hydraulic delay system, immersing the solenoid core in a tube filled with a viscous liquid. The core is held with a spring that keeps it displaced with respect to the solenoid as long as the circulating current remains below the nominal value of the switch. During an overload, the solenoid draws the core through the fluid to close the magnetic circuit, applying enough force to release the latch. This delay allows brief increases in current beyond the nominal value of the device, without opening the circuit, in situations such as, for example, starting motors. The short circuit currents supply sufficient force to the solenoid to release the latch regardless of the position of the core, thus preventing delayed opening.

Magnetic device

Present in magnetic and magneto-thermal circuit breakers, it is made up of a coil, a core and a moving part. The intensity that powers the load passes through said coil, and if it is much higher than the nominal intensity of the device, a magnetic field is created that is capable of dragging the moving part and causing the circuit to open almost instantaneously. Detects short circuit faults that may exist in the electrical circuit.

Under short-circuit conditions, a current much greater than the nominal current flows; When an electrical contact opens a circuit where there is a large current flow, an electric arc is generally produced between said already open contacts, which allows the current to continue flowing. To avoid this, the switches incorporate features to divide and extinguish the electric arc. In small switches, an arc extinction chamber is implemented, which consists of several metal plates or ridges of ceramic material, which help lower the arc temperature. The arc is moved to this chamber by the influence of a magnetic blowing coil. In larger switches, such as those used in electrical substations, vacuum, inert gases such as sulfur hexafluoride or oil are used to weaken the arc.

The breaking capacity or breaking capacity of a switch is the maximum short-circuit current that it is capable of successfully breaking without suffering major damage. If the short circuit current is set to a value greater than the breaking capacity of a switch, the switch will not be able to interrupt it, and will be destroyed.

The small switches can be installed directly next to the equipment to be protected, although they are generally arranged in a panel designed for this purpose. Power switches are located in cabinets or electrical cabinets, while high voltage switches can be located outdoors.

Circuit breakers are rated both by the normal current they are expected to carry and by the maximum short circuit current they can safely interrupt. This last figure is the ampere interrupting rating (AIC) of the breaker.

Under short-circuit conditions, the maximum calculated or measured short-circuit current may be many times the normal rated current of the circuit. When electrical contacts are opened to interrupt a large current, there is a tendency for an arc to form between the open contacts, which would allow the current to continue. This condition can create conductive ionized gases and molten or vaporized metal, which can cause the arc to continue or create additional short circuits, which could cause the circuit breaker and the equipment on which it is to explode. is installed. Therefore, circuit breakers must incorporate several features to split and extinguish the arc.

The maximum short circuit current that a switch can interrupt is determined by testing. Application of a switch on a circuit with a potential short-circuit current greater than the interrupting capacity rating of the switch may cause the switch to fail to safely interrupt a fault. In the worst case, the switch may successfully interrupt the fault, only to explode when reset.

Typical home panel circuit breakers are rated to interrupt a short circuit current of 6 kA (6000 A).

Miniature circuit breakers used to protect control circuits or small appliances may not have sufficient interrupting capacity for use in a panel; These circuit breakers are called "supplementary circuit protectors" to distinguish them from distribution circuit breakers.

Several companies have considered adding monitoring for appliances through electronics or using a digital circuit breaker to monitor circuit breakers remotely. Utilities in the United States have been reviewing the use of the technology to turn appliances on and off, as well as potentially shutting down electric car charging during periods of high grid load. These devices under investigation and testing would have wireless capability to monitor electrical usage in a home through a smartphone app or other means.[5]​.

The following types are described in separate articles.