Circuit breaker Guide, Meaning , Facts, Information and Description
A circuit breaker is a piece of equipment which is designed to protect an electrical apparatus from damage caused by overload or short circuit. Unlike a fuse which operates once and then has to be replaced, a circuit breaker can be reset (either manually or automatically) to resume normal operation.Circuit breakers are often implemented with a solenoid (electromagnet) whose strength increases as the current increases and eventually trips the circuit breaker. Alternatively a bimetallic strip may be used which heats and bends with increased current. Some circuit breakers incorporate both techniques. This allows the properties of the circuit breaker to be tailored to suit the application, with the electromagnet generally responding to short, large surges in current (short circuit) and the bimetallic strip responding to smaller but longer-term (overload) overcurrent conditions.
Under short-circuit conditions a current of several thousand amps can flow (see maximum prospective short circuit current) and when a circuit breaker tries to interrupt this current an arc may form allowing the flow of current to continue even though the contacts of the circuit breaker are open. Some smaller circuit breakers incorporate a device which divides and extinguishes this arc. Larger circuit breakers such as those used in electrical power distribution may use an inert gas such as sulfur hexafluoride or be immersed in oil to suppress the arc.
Circuit breakers are either installed directly in equipment, or are arranged in a breaker panel.
When supplying center tapped single phase (e.g. 240 volts from +/-120 volts), or other line-to-line circuits, a double pole, common trip breaker is typically used. Appliances such as stoves, electric clothes dryers, and large heaters are typically wired line-to-line and supplied by a common trip breaker. Three pole common trip breakers are typically used to supply three phase power.Internal details of a European breaker
Photograph of the inside of a 10 amp European DIN-rail mounted thermal-magnetic miniature circuit breaker. Circuit breakers such as this are the most common style in modern domestic and commercial electrical distribution boards throughout Europe. Unfortunately while the size and shape of the opening in the front and its elevation from the rail are standardised the arrangements for busbar connections are NOT so you should take care that the breaker you select fits the busbar in your board and prefereablly is the same make and range.
Common trip breakers