Electrical Supply: What is a Fast-Acting Fuse?

Fuses work to protect us from electrical faults that could start fires in our homes. If they detect there is too much current running through an electrical device, they block the currents by shorting out. There are different kinds of fuses which can be used in various electrical applications. While a slow blow fuse can withstand high current for short amounts of time, fast-acting fuses will burst immediately when high power voltage passes through it. This article will take a look at some of the uses and applications of a fast acting fuse.

How do Fuses Work?

Wires get hot when electricity travels through them. In a fuse, electricity flows through a thin piece of wire. If it detects that the current passing through the wire is too high, it will heat up to a point that it will burn or melt. When this happens, it will break the circuit and stop the current, preventing any sort of electrical hazard from occurring.

When Are Fast Acting Fuses Used?

Fast blow fuses are the most common type of fuse. They are used in home appliances because these are very sensitive to the changes in the flow of electricity, thus, require a safety device that will be able to handle this problem. A short-circuit happens when these fuses sense a surge in electricity, therefore saving the electronic circuit. Fast acting fuses must be used in purely resistive circuits where there are very few or no surges or where IC and other sensitive components need to be protected.

Slow blow fuses, on the other hand, are often used in motors and fluorescent lights. These devices power on with a high voltage which then lowers and regulates during regular use. Therefore, they need a fuse that will be able to handle this immediate burst of power and then adjust as needed.

It is important to know the difference between the slow blow and fast acting fuses if you are using them in practical applications. There should be a sticker or raised lettering on the fuse which indicates which it is. If not, you can look inside the tube of the fused glass to see the wire filament. A fast blow fuse has thin wire while a slow blow fuse has a thick wire with a small spring at one end.

Fast acting fuses can be replaced with slow blow ones to enhance anti-surge capability. However, slow blow fuses that are replaced by fast-acting ones may cause the fuse to break as soon and the equipment is switched on. Slow blow fuses are also considerably more expensive than fast acting ones.

Types of Fuses

There are two types of fuses that are commonly used. These include cylindrical and plug fuses. A cylindrical fuse consists of a ribbon of fusible metal enclosed in a ceramic fiber or cylinder. This type of fuse is found in an electric circuit where current must flow through the metal strip to complete the circuit. If excess current surges through the circuit, the metal link will heat to its melting point and break. The circuit will then open, stopping the current flow and protecting the circuit. This type of fuse is mostly used for electrical equipment and appliance.

Plug fuses are used to protect electrical wiring in homes, consisted of a fusible metal strip that current flows through to complete the circuit. The strip is enclosed in a plug that can be screwed into a fusible electric panel. Plug fuses usually have a window which allows those using it to be able to determine the condition of the strip by glancing at it.

How are Fuses Rated?

Fuses are rated in amps. They are also engineered to contribute a negligible amount of extra resistance to the circuits they protect. This is done by making the fuse wire as short as possible. However, the ampacity of the fuse is not related to its length and will, therefore, blow at a certain current no matter how long it is. The length of the wire is directly related to its resistance only, and the shorter it can be made, the less resistance it will have.

However, some amount of consideration has to be made of what happens after a fuse blows. The metal ends of the wire will be separated by an air gap with a full supply voltage between the ends. If the fuse isn’t made long enough on a high voltage circuit, a spark may be able to jump from one end of the melted wire to the other, completing the circuit again. Consequently, fuses are rated in terms of their voltage capacity in addition to the current level at which they will blow.

It is good to understand how these fuses work and the best applications to use them in, so we can stay safe while working with electricity.