Although the first electrical generator and transformer were invented in the mid-18th century, more than a full century passed before fuses came into use to protect against overcurrents. These relatively simple devices were comprised of an inflammable housing and a metallic strip that would break if too much current passed through it. However, the obvious downside of having to replace individual fuses after breakage led Thomas Edison to patent the first circuit breaker in 1879, and the Swiss conglomerate Brown, Boveri & Cie would produce one remarkably similar to modern devices in 1924.
Today, circuit breakers come in many different kinds of configurations and are widely used in both consumer and commercial electrical applications where an overload could lead to a fire risk. During an overload event, electricity will arc, which could cause combustion if not contained. All circuit breakers feature an arc extinguisher, which does just that. They also all have protective frames, a means of opening and closing the breaker, contacts that let electricity flow when closed, and trip units that help manage lengthy overloads. Unlike fuses, circuit breakers can be manually or automatically reset after a short circuit.
While all circuit breakers contain these elements, models can vary significantly based on other factors such as voltage rating, casing type, extinguisher method, and more.
Circuit Breaker Manufacturers
Surplus Record has a wide assortment of circuit breakers by top manufacturers. Read more about our top circuit breaker manufacturers.
Types of Circuit Breakers
Insulated Case & Molded Case Circuit Breakers
Generally speaking, these are some of the most popular types of circuit breaker. They employ glass-reinforced insulating materials, like fiberglass, for dielectric strength and can be used for a large range of voltages and frequencies with easily adjustable trip settings.
Low-Voltage Circuit Breakers
Possibly the most common kind of circuit breaker in residential, commercial, and industrial applications alike, low-voltage circuit breakers come in two primary types: miniature circuit breakers that manage currents up to 100 amps and molded-case breakers rated up to 2,500 amps. These circuit breakers are generally easy to service and disassemble.
Medium-Voltage Circuit Breakers
Typically rated from one to 72 kilovolts, these circuit breakers are used primarily in industrial applications and differ according to the ways they extinguish an electrical arc. Air-break circuit breakers use common atmosphere combined with electronic controls, while vacuum-break interrupters employ atmosphereless bottles. Sulfur hexafluoride breakers use their eponymous gas and require little maintenance.
High-Voltage Circuit Breakers
Rated for 72.5 kilovolts and up, high-voltage circuit breakers are primarily used in infrastructure-related electrical applications. In addition to the extinguishing methods used for medium-voltage breakers, high-voltage breakers employ bulk oil and carbon dioxide.
Magnetic-Hydraulic Circuit Breakers
Springs, solenoids, and a viscous fluid combine to safeguard against overcurrent events with this type of breaker.
Thermal-Magnetic Circuit Breakers
This dual-stage circuit breaker most commonly appears in building electrical distribution boards, employing both thermal sensors and magnetic sensors to detect surges. These circuit breakers guard against short, intense overcurrents and lower overcurrents that occur over an extended period.