Circuit Breakers & Fuses

More Information about Circuit Breakers and Fuses

The major difference between fuses and circuit breakers is that the former are discarded after providing one-time protection, while the latter can be reused repeatedly. Circuit breakers use either magnetic or thermal mechanisms to detect a fault and to interrupt current flow. Fuses operate by melting their fuse wire. Both should provide operational protection for circuits. Fuses should be used in smaller systems because they are a less expensive protective component. Circuit breakers should be used for larger assemblies because of their size and because they can be reset.

FAQs

Can molded case circuit breakers provide overcurrent protection for electrical equipment in electrical systems?

Yes, molded case circuit breakers (MCCBs) can provide overcurrent protection for electrical equipment in electrical systems, safeguarding against maximum fault current and short circuit current.

What is "voltage drop" in control circuits?

In control circuits, "voltage drop" refers to the reduction in voltage that occurs as electrical current flows through the resistance or impedance of the conductors and components within the circuit​.

What is the short circuit rating of cartridge fuses and glass fuses?

The short circuit rating of cartridge fuses and glass fuses varies by design and application but typically ranges from 35A to 10kA or higher for cartridge fuses and up to 35A for smaller glass fuses used in low-power circuits.

Breakers vs Fuses 

Fuses

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

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.