What's the Difference Between a Circuit Breaker and a Fuse?
A Circuit Breaker (C/B) is a mechanical device that will involve a magnetic solenoid and bimetallic strip inside. When the strip heats up due to current, it will bend and activate the solenoid to trip the circuit breaker and stop the flow of power.
A Fuse is a type of insulating material with a filament in the middle of it. When the fuse starts to heat up due to current, the filament will break, breaking the flow of electricity in the circuit.
Some of the main differences between fuses and C/Bs are usually cost. Fuses will be less expensive, but that is due to a fuse being a one and done. When it blows, you must replace it, unlike a C/B. Fuses will typically react very quickly to overcurrent whereas a C/B will take a bit longer to react.
Fuses have the advantage of being less expensive, quicker to react which is nice for sensitive electronics. Fuses have a disadvantage of being single use, which can lead to either being out of fuses or selecting the wrong type of replacement fuse.
Fuses also have the propensity to blow more often on circuits that might have high inrush currents on startup.
What are the Advantages?
C/Bs have the advantage of being able to reset the breaker when they trip once the fault has been cleared. C/Bs are going to be more expensive than fuses, and do not have as quick of reaction time as fuses do. When to Select Circuit Breakers or Fuses
Selecting a fuse or circuit breaker all depends on the application you are using. If you have something that requires high sensitivity you might want to look at fuses, whereas if you have high inrush current you will want to lean towards circuit breakers. It can also depend on ground fault or arc fault applications, which would generally be protected by a circuit breaker.
Some of the different types of fuses can include slow blow, quick blow. They can also have different types of filaments inside that allow them to react differently. Not all fuses are created equally, there are specialty fuses for special applications such as drive fuses or ac or dc fuses only. With breakers, you can have multipole breakers, arc fault, and ground fault breakers, as well as adjustable trip units within the breaker which allows you to dial in the breaker for your application.
Breakers have different trip curves. You want to ensure that you’re selecting the right type of curve. When looking at the curves you will see a multiple of current along one axis and time along the other. When reading the curves, it will show how long a breaker can withstand current before tripping. This can be important to make sure you select the right type of breaker for the application such as high inrush on a motor so that you don’t trip the breaker too soon and cause nuisance tripping or taking down a whole line unexpectedly.
When selecting fuses, make sure you’re selecting the right type of fuse for your application. You will want to make sure you select the right class of fuse or specialty fuse for your needs. When replacing a fuse, you will want to ensure that you are referencing the original drawings to ensure that the correct fuse is being put in. One best practice would be to use a label on the circuit to make sure the proper fuse is identified for that circuit. It helps eliminate confusion on what type of fuse is needed.
Selecting the right type of protection for the circuit is important to ensure that in the event of some type of overcurrent or other unintended means of operation that the device you selected reacts the way it should to make sure that the circuit is removed from power. At the end of the day, it's important to select the right type of breaker or fuse to ensure the safety of everyone involved.
