Circuit Breakers & Fuses
Circuit protection is vital to any electrical system and circuit breakers and fuses are the main components to provide this protection. When a short circuit or overload occurs, breakers and fuses are designed to disconnect the current, preventing irreparable damage.
Fuses contain a wire that heats up and melts when the current going through the fuse is too great, thus breaking the circuit. The fuse would then need to be replaced.
Resettable fuses contain a polymer material that heats up when overcurrent occurs causing resistance to increase sharply. This resistance cuts off the current in the circuit. When the overcurrent conditions are removed, the resettable fuse cools and its resistance, drops causing the fuse to “reset” and allowing the current to flow through the circuit once again.
Miniature circuit breakers are electromechanical, temperature-sensitive devices contained within a plastic casing with an on/off switch, which makes them very easy to use. These breakers are mainly designed for low-energy circuits and automatically reset when the overcurrent is removed and the temperature returns to a safe level.
Molded circuit breakers are electromechanical, temperature-sensitive devices contained within a plastic casing with an on/off switch, which makes them very easy to use. These breakers are mainly designed for high-power equipment due to its better capacity and automatically reset when the overcurrent is removed and the temperature returns to a safe level.
Fuses are safety devices that are intended to provide protection to both equipment and people in the event of a power surge or an overcurrent situation. A fuse can provide this protection by using a small piece of wire that is sacrificial, and is intended to burn up when too much current is passed through it. When this happens, the fuse eliminates the flow of electricity in that circuit until it is replaced. The size and type of wire that is used in the fuse will dictate how much current can pass through that individual fuse. So the main thing to remember is, when a fuse blows, it must be replaced and cannot be reused.
Circuit breakers are intended to be reused after they are “tripped” during a power surge or an overcurrent situation. Much like fuses, circuit breakers are designed to trip at a certain current level. This is intended to protect both equipment and anyone in the area of that particular circuit. Circuit breakers can be found in just about any variation from single phase, low current applications to three phase, and high current applications.
As a general rule: fuses are more simplistic and reliable. They cost less initially and are better suited for individual circuit protection. However, they can create more cost over time with each use and may create hazards due to the exposed connection points. Whereas circuit breakers offer better branch circuit protection and do not need to be replaced after each use. They are more expensive initially and, because of their complexity, are more prone to failure over time.