Switch failures
Introduction
A circuit breaker (Argentina and the Philippines), circuit breaker (Spain), automatic (Chile), differential or taco[1] (Colombia and Nicaragua), breaker or pastilla (Mexico, Venezuela, Ecuador, Costa Rica and Panama), or flipon (Guatemala) is a device capable of automatically interrupting or opening an electrical circuit when certain fault conditions occur. They can be thermomagnetic or differential automatic switches (circuit breakers).
Thermomagnetic switches or circuit breakers mainly protect the circuit, equipment and wiring from overcurrents, through two mechanisms. Thermal protection protects against overloads, and its actuation time is much slower than the other protection. The magnetic protection protects against short circuits, and its actuation time is much faster than the previous one. Overloads are overcurrents that barely exceed the nominal current value of a circuit, for example due to excess connected loads, motor starts or loads with motors (air conditioners, refrigerators). Short circuits are situations in which a low impedance path is unintentionally provided in a circuit, causing current to flow up to hundreds of times the circuit's rated current.
Differential switches or circuit breakers mainly protect people, in case current flows through them. Very low currents (in the order of milliamps) can cause death, however, thermomagnetic switches are not sensitive enough nor do they act quickly enough. Instead, residual current circuit breakers trip as soon as a difference as small as 5 mA is detected between the incoming and outgoing current (where the rest of the current is supposed to flow to ground through a person), thus tripping and saving the person.
Unlike fuses, which must be replaced after a single use, the circuit breaker can be reset once the problem that caused it to trip has been located and repaired.
Circuit breakers are manufactured in different sizes and characteristics, which makes them widely used in homes, industries and businesses.
The first circuit breaker was designed by Thomas Edison in 1879. Electrical engineer William Stanley Jr. improved the design in 1890. Granville Woods invented the automatic circuit breaker in 1900.