How Circuit Breakers Work?

Giving this essential item the name “circuit breaker” was probably an easy decision since the name describes exactly what the item does. Electricity has to travel in a complete or closed circuit to function properly and the circuit breaker exists to interrupt the movement of electrons in the circuit. It doesn’t break the circuit literally of course, but unless it is reset the closed system will not operate.

Circuit breakers are a crucial safety item in home and business electrical systems because they are designed to “trip” if the circuit is overloaded. Heat generated in an overloaded circuit could cause a fire or damage equipment and appliances if there were no circuit breakers built in. Not only that, a repairman can manually “trip” the breaker to cut power in the circuit so that he can do his work safely.

Most of the basic information about electricity describes the three basic components: voltage, current and resistance. To understand voltage it may be best to think of the power that moves electrical charge through the circuit. Some texts and study materials describe voltage as pressure. Current (in amperes) is a measure of the rate of movement. Of course, resistance is just that. Even the wire that carries the electrical charge puts up some resistance to the movement of electrons.

The relationship of these three elements determines the usefulness and safety of the electrical circuit. This is where the circuit breaker comes in. It is designed to automatically protect the circuit, the building and the connected equipment from damage. As described earlier, an electrical circuit must be closed and provide a continuous route for the electrons to move through. At one time, a fuse was used to interrupt a circuit if there was too much voltage or the rate of movement was too high. But the fuse needed to be replaced because it the path it provided was permanently “cut.” That’s the basis for the common term “blow a fuse.”

Circuit breakers, by contrast, are made to open the circuit but can be reset without being replaced. Some breakers detect low voltage and open. There are also high-voltage breakers that open when the voltage level is dangerously high. Some circuit breakers operate on a spring mechanism that uses a level of tension to open contacts within the breaker. In normal operation the contacts touch and conduct electricity, continuing the circuit. When the voltage or amps are too high for safe operation, the breaker opens the circuit and stops the flow of electricity.

The constant current through copper or silver-alloy contacts inside a breaker can erode the metal. Though breakers are designed to be re-used, as compared to the older-style fuse, they have to be replaced occasionally. Some newer-style breakers use a particular type of gas/vapor that will conduct electricity. There are also vacuum circuit breakers that can operate in high-voltage situations. Modern circuit breakers are so well made and sensitive that they can interrupt the current in less than a second.

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