Under the International Electrotechnical Commission (IEC) standards, fuse markings like gG, gR, and aR define their specific performance characteristics and intended applications. Understanding these classifications is crucial for selecting the right fuse to ensure system safety and reliability. Here’s a breakdown of what these common fuse types mean.
gG / gL - General Purpose, Full-Range Protection
A gG (or the older gL) fuse is a general-purpose, full-range protection device. It is designed to safely interrupt everything from the smallest melting overload currents up to the highest-rated short-circuit fault. However, its operating speed is slower compared to specialized semiconductor fuses.
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Primary Use: Its main application is the protection of cables, wires, and line-side equipment in general distribution circuits.
aM - Motor Protection, Partial-Range Protection
An aM fuse is specifically designed for the short-circuit protection of motor circuits. It can withstand the high inrush currents associated with motor start-ups and shutdowns without tripping. Because it only provides partial-range protection, it must be paired with an overload device (like a thermal relay) for complete motor safety.
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Primary Use: Protecting electric motors from short-circuit faults.
aR - Semiconductor Protection, Partial-Range Protection
An aR fuse is a high-speed, partial-range device designed for the short-circuit protection of power semiconductors. It operates extremely quickly, clearing major faults within milliseconds to protect sensitive components like diodes, thyristors, and IGBTs. The trade-off for this high speed is typically higher power loss (watt loss) during normal operation.
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Primary Use: Short-circuit protection for power semiconductors in devices like inverters, soft starters, and UPS systems.
gR - Semiconductor Protection, Full-Range Protection
A gR fuse provides full-range protection (both overload and short-circuit) for semiconductors. While it offers robust overload protection, it operates slightly slower on short circuits compared to an aR fuse. This makes it a comprehensive solution for protecting sensitive power electronics from a wide array of fault conditions.
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Primary Use: Complete overload and short-circuit protection for semiconductors and power electronic devices.
Specialized Fuses for New Energy Applications
gPV - Photovoltaic System Protection
A gPV fuse is a fast-acting, full-range fuse specifically designed to protect photovoltaic (PV) systems, such as in solar combiner boxes. Its electrical performance is defined by standards IEC 60269-6 and UL 248-19. These fuses are built to handle the specific low-overload and DC fault conditions found in solar power applications.
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Primary Use: Overcurrent protection in photovoltaic panels, strings, and inverters.
gBat - Battery System Protection
A gBat fuse is a fast-acting fuse designed to protect battery energy storage systems (BESS). Engineered according to the IEC 60269-7 standard, these fuses can withstand the constant charge and discharge cycles of battery use while providing rapid interruption in the event of a system fault.
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Primary Use: Protection of battery packs, energy storage systems (ESS), and DC power circuits.