Cartridge fuses are low-cost electrical safety devices that are used for the overload protection of electrical circuits and appliances. They are cylindrical in shape and have a contact point at each end. Cartridge fuses are typically constructed from ceramic, glass, or porcelain. For more information on cartridge fuses please see our complete guide to fuses.

RS stock a comprehensive range of cartridge fuses from industry-leading brands including Eaton, Littelfuse, Mersen and of course RS PRO.

How do cartridge fuses work?

Cartridge fuses contain a piece of wire that melts when too much current flows through the circuit. When the wire melts, it breaks the circuit which prevents any damage. This is often referred to as burning out or blowing out. Put simply, when a fuse blows, the circuit is broken. Once a fuse has blown, it will need replacing to make the circuit complete again and allow the flow of current.

What are the different types of fuse markings and speed codes?

Cylindrical cartridge fuses are used in a range of industrial, commercial, and domestic applications. Selecting the correct fuse speed is essential for the protection of your device. Here are some of the most common markings you will find on a cartridge fuse.

• FF = Very Fast Acting (Flink Flink)
• F = Fast Acting (Flink)
• M = Medium Acting (Mitteltrage)
• T = Slow Acting (Trage)
• TT = Very Slow Acting (Trage Trage)

Why use cartridge fuses?

Cartridge fuses are a relatively cheap way of protecting electrical equipment from short circuits and overcurrent. They are incredibly safe as they do not produce flames, arcs, or gas when they burn out and break the circuit.

What current rating should you choose?

Cartridge fuses are available in a range of standard amperages. When choosing the correct fuse for your application, you should choose a fuse with a nominally higher current rating than the device that it is being used in. This means that if there is a slight, harmless power increase, the fuse will not blow.