Circuit Breakers Information Guide

Circuit breakers are electrical switches designed to protect an electrical circuit from damage caused by overload or short circuit.
If a circumstance arises where a fault condition occurs, the switch discontinues electrical flow. This circuit breaker can be reset either manually or automatically. In contrast, a fuse must be replaced when it operates one time.

Circuit breakers are made in varying sizes, from small devices that protect an individual household appliance up to large switchgear
designed to protect high voltage circuits feeding an entire city.

Types of Circuit Breakers

Low voltage circuit breakers
Magnetic circuit breakers
Thermal magnetic circuit breakers
Common trip breakers
Medium-voltage circuit breakers
High-voltage circuit breakers

Operation

All circuit breakers have common features in their operation, although details vary substantially depending on the voltage class, current rating and type of the circuit breaker.

The circuit breaker must detect a fault condition; in low-voltage circuit breakers this is usually done within the breaker enclosure. Circuit breakers for large currents or high voltages are usually arranged with pilot devices to sense a fault current and to operate the trip opening mechanism. The trip solenoid that releases the latch is usually energized by a separate battery, although some high-voltage circuit breakers are self-contained with current transformers, protection relays, and an internal control power source.