In the past, industrial fuses were considered to have ‘operation speeds’ such as ‘fast acting’ or ‘slow acting’. In recent years, these descriptions have been replaced with a new way of communicating the intended function of a fuse – the ‘Utilisation Categories’ (created by the IEC). Most fuses are marked with symbols denoting their particular application or characteristic. The symbols consist of two or three letters.

The first, lower-case letter indicates the breaking range of the fuse.

• “g” stands for full-range breaking capacity fuse-link, meaning that the fuse is capable of breaking all overcurrents from its minimum melting current up to its breaking capacity. These fuses can protect from overloads and short circuits. Full-range breaking capacity fuses can be used as sole protective devices.
• “a” stands for partial-range breaking capacity fuse link, meaning that the fuse is capable of only breaking high currents of a multiple of its rated current. Partial-range breaking capacity fuses are designed for shortcircuit protection only, and are therefore used in combination with other devices providing protection against overcurrents. They are also frequently used for back-up protection of other switching devices having a lower breaking capacity (eg. contactors or circuit breakers).

The second, upper-case letter indicates the characteristic. These are related to the intended application. For example, ‘G’ relates to general applications (cable & line protection) and ‘M’ relates to motor circuits. Sometimes, this part can be expressed with two letters such as ‘PV’ (Photovoltaic protection) or ‘Tr’ (Transformer protection). 

Current Utilisation Categories

gG: Full range breaking capacity fuse for general application, mainly used for cable and line protection. Formerly known as gl, gll, gL, gT & gF.

aM: Partial range breaking capacity fuse for the short circuit protection of motor circuits.

gR: Full range breaking capacity fuse for the protection of semiconductor devices (quicker than gS).

aR: Partial range breaking capacity fuse for the short circuit protection of semiconductor devices.

gPV: Full range breaking capacity fuse for the protection of photovoltaic systems. Also known as PV.

gS: Full range breaking capacity fuse for the protection of semiconductor devices for increased line utilisation. Combines gR and gG performance. Semiconductor protection against short circuits via the gR characteristic combined with cable protection against overload via the gG characteristic. Formerly known as gRL & gGR.

gB: Full range breaking capacity fuse for mining applications. Formerly known as gTF.

gTr: Full range breaking capacity fuse for transformer protection, rated in transformer apparent power (kVA) instead of rated current (A).

gM: Full range breaking capacity fuse for motor circuit protection, dual rated (widely used in the UK, Australia & South Africa).

gN: North American general application fuse, mainly for cable and line protection.

gD: North American general application time-delay fuse, mainly for motor circuit protection.

Identification of Miniature Fuses

As there is no global standard requirement, most miniature electronic fuses do not have any identifiable markings that communicate their design function. However, most of the European brands have the following markings:

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If you’re trying to identify a fuse, please contact the experts at FUSECO. We have 29 years of experience specialising in electrical products. Our friendly staff members will be willing to help you identify exactly what fuse you need.

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