Semiconductor fuses are categorized into three main classes based on their breaking (interrupting) characteristics: aR, gR, and gS. The markings for these fuse speeds are typically printed on the fuse body to aid in identification.
Typical applications for semiconductor fuses include the protection of semiconductors (diodes, thyristors, TRIACs, etc.) in power rectifiers, UPS systems, inverters, motor drives (both AC and DC), soft starters, solid-state relays, photovoltaic inverters, welding inverters, and any application that requires the protection of sensitive semiconductor devices.
• aR Class Fuses
The aR class fuse provides partial-range breaking capability (short-circuit protection only) and is one of the most common types found on the market. It is used for the protection of power semiconductors and is governed by common standards such as IEC 60269-4, GB/T 13539, GB/T 31465, and UL 248.
Note: aR class fuses are typically faster (i.e., have a lower I²t value) than their gS or gR counterparts. An aR fuse must not be used to replace a gR fuse. However, a gR fuse can completely replace an aR fuse. The GB 13539 standard specifies that while the current performance is not restricted, requirements for temperature rise, power dissipation, and breaking capacity must be met.
• gR Class Fuses
The gR class fuse provides full-range breaking capability (both overload and short-circuit protection). It is used to protect semiconductors, cables, and all switchgear within an installation.
Designers can often replace an aR class fuse with a gR class fuse for enhanced protection.
• gS Class Fuses
The gS class fuse is very similar to the gR class. Both offer full-range breaking capability (overload and short-circuit protection). However, because gS class fuses have stricter melting thresholds, their power dissipation is lower than that of gR fuses. This also results in a lower fuse element temperature for gS fuses.
The Key Difference Between aR and gR/gS Fuses
The minimum breaking current of an aR class fuse is significantly higher relative to its rated current.
The gR class fuse markedly enhances the performance of semiconductor protection. It is suitable for the design of low-voltage equipment and the protection of power electronics, offering more comprehensive performance and a wider safety range. The GFEFUSE brand recommends prioritizing gR class fuses for the protection of electronic and electrical power supply equipment.
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