A circuit breaker is an automatically-operated electrical switch designed to protect an electrical circuit from damage caused by excess current, typically resulting from an overload or short circuit. Its basic function is to interrupt current flow after a fault is detected. Unlike a fuse, which operates once and then must be replaced, a circuit breaker can be reset to resume normal operation.
All circuit breaker systems have common features in their operation but can vary depending on the voltage class, current rating, and type of the circuit breaker.
A basic circuit breaker consists of a simple switch, connected to either a bimetallic strip or an electromagnet. The hot wire in the circuit connects to the two ends of the switch. When the switch is flipped to the on position, electricity can flow from the bottom terminal, through the electromagnet, up to the moving contact, across to the stationary contact and out to the upper terminal. The electricity magnetizes the electromagnet. Increasing current boosts the electromagnet’s magnetic force, and decreasing current lowers the magnetism. When the current jumps to unsafe levels, the electromagnet is strong enough to pull down a metal lever connected to the switch linkage. The entire linkage shifts, tilting the moving contact away from the stationary contact to break the circuit and the electricity shuts off.
Classifications of circuit breakers can be made based on voltage class, construction type, interrupting type, and structural features. Circuit breakers also come in a variety of sizes: from small devices that protect low-current circuits or individual household appliances, up to large switchgear designed to protect high voltage circuits feeding heavy machinery.
For more information about circuit breakers and other electrical safety equipment, contact our experts today.