A fuse types chart categorizes overcurrent protection devices by physical form factor, interrupting capacity (AIC/kA), and time-current characteristics (fast-acting vs. time-delay) according to UL 248 and IEC 60127 standards. For low-voltage electronics, the 5x20mm cartridge and ATO/ATC automotive blade dominate; for mains and industrial panels, Class CC, Class J, and NH/HRC fuses provide the necessary high interrupting ratings to safely clear massive fault currents without catastrophic failure.

The Master Fuse Types Chart (UL 248 & IEC 60127)

Before selecting a component, understand how to read this table. The Standard column dictates the testing methodology (UL for North America, IEC for international/European). The Interrupting Rating (AIC) is the maximum short-circuit current the fuse can safely clear without rupturing. The Time-Current Profile defines how fast it blows relative to its nominal rating. Bookmark this section for quick reference when sizing protection for your next bench build or panel wiring job.

Table 1: Comprehensive Fuse Types and Ratings Reference (Assumes 25°C Ambient, Copper Conductors)
Form Factor Standard Voltage / Current Range Interrupting Rating (AIC) Time-Current Profile Primary Application
5x20mm Glass IEC 60127-2 250V AC / 0.1A-10A 35A or 10x In (Low) Fast-Acting (F) Low-power PCBs, basic IEC inlets
5x20mm Ceramic IEC 60127-2 / UL 248 250V AC / 0.1A-20A 1,500A - 10kA (High) Time-Delay (T) / Fast (F) Mains power supplies, motor loads
ATO/ATC Blade ISO 8820 / UL 248 32V DC / 1A-40A 1,000A Fast / Slow Automotive 12V/24V DC circuits
Class CC UL 248-4 600V AC/DC / 0.1A-30A 200kA AC / 20kA DC Fast / Time-Delay Industrial control panels, VFDs
Class J UL 248-8 600V AC / 1A-600A 200kA AC Fast / Time-Delay Main disconnects, large feeders
NH / HRC IEC 60269 400V-690V AC / 2A-1250A 120kA - 200kA gG (General) / aM (Motor) European industrial, heavy machinery

Decoding the Columns: Derating and Installation Realities

A chart provides baseline data, but real-world physics dictates how the fuse actually performs on the bench or in the panel. Here is how to translate the table above into safe, reliable circuit protection.

Which Column Applies to Your Installation?

While voltage and current ratings get the most attention, the Interrupting Rating (AIC) column is the most critical for safety. If your mains busbar has an available fault current of 10,000A (10kA) and you install a 5x20mm glass fuse rated to interrupt only 35A, a dead short will cause the glass tube to violently shatter, spraying molten metal and sustaining an arc. You must always match or exceed the AIC to the available fault current at the point of installation. For standard 120V/240V residential branch circuits, 10kA AIC is usually sufficient; for industrial 480V services, 200kA AIC (Class J or NH) is mandatory.

How Derating Modifies the Base Value

Fuses are fundamentally thermal devices. The nominal current ratings in the chart assume a standard 25°C (77°F) ambient temperature. When installed in an enclosed control panel, a solar combiner box, or near a heat-generating transformer, ambient temperatures frequently exceed 40°C.

The 10% Derating Rule: For most standard cartridge and blade fuses, you must derate the nominal current capacity by roughly 10% to 15% for every 10°C increase above 25°C. If you place a 10A ATO blade fuse inside an engine bay or enclosed inverter chassis that reaches 65°C, the fuse will nuisance-blow at approximately 6.5A to 7.5A of continuous load. Always calculate your continuous load (NEC 125% rule) against the derated fuse capacity, not the stamped nominal value.

What the Table Cannot Tell You

A reference chart cannot show you let-through energy (I²t) or peak let-through current. Two different 10A fast-acting fuses might both clear a short circuit, but a specialized semiconductor fuse will clear it in 1 millisecond (limiting the thermal energy passed to the load), while a standard glass fuse might take 10 milliseconds. If you are protecting a $500 IGBT or a sensitive MOSFET bridge, standard time-current profiles are useless; you must consult the manufacturer's specific I²t melting and clearing curves to ensure the fuse clears before the silicon junction vaporizes.

Application Quick-Jumps: Sizing for Common Bench and Mains Loads

Use these common scenarios as a decision framework for your next project. These examples assume standard copper conductors and typical ambient conditions.

Scenario A: 120V AC Bench Power Supply (IEC Inlet)

  • Selected Fuse: 5x20mm Ceramic, Time-Delay (T), 250V AC.
  • Sizing Math: The power supply draws 2.5A continuous (Full Load Amps). Applying the 125% continuous load multiplier yields 3.125A. Select the next standard size: 3.15A or 4A.
  • Why Ceramic Time-Delay? Switching power supplies and transformers draw massive inrush currents (often 10x to 20x nominal) for the first few AC cycles as bulk capacitors charge. A Fast-Acting (F) glass fuse will interpret this inrush as a fault and nuisance-trip. A ceramic Time-Delay fuse absorbs the thermal spike of inrush without opening, but will still clear a sustained dead short. Never use glass here; the interrupting rating is too low for direct mains connection.

Scenario B: 12V DC Off-Grid Solar Branch Circuit

  • Selected Fuse: ATO/ATC Blade (for loads <40A) or Class CC (for loads >40A up to 30A per pole, ganged).
  • Sizing Math: A 300W 12V inverter draws roughly 25A continuous. 25A x 1.25 = 31.25A. Select a 35A or 40A ATC blade fuse, paired with 8 AWG wire minimum.
  • The DC Arc Hazard: DC current does not have a natural zero-crossing like AC, meaning electrical arcs are much harder to extinguish. Standard AC-rated glass cartridge fuses lack the internal arc-quenching filler (like silica sand) required for DC. If a 12V battery bank shorts out through an AC glass fuse, the fuse will clear the initial melt but may sustain a plasma arc across the gap, leading to a fire. Always use fuses explicitly rated for DC voltage (32V DC for automotive blades, 600V DC for Class CC solar applications).
Mains Voltage Safety Protocol: Any work involving fuse replacement or sizing on circuits above 50V AC or 120V DC requires strict adherence to safety protocols. De-energize the circuit at the main breaker, apply Lockout/Tagout (LOTO) procedures, and verify the circuit is dead using a known-working CAT III or CAT IV multimeter before touching any fuse clips or terminal blocks. NEC-style guidance is provided here for educational purposes; your local Authority Having Jurisdiction (AHJ) has final authority on code compliance and may require a licensed electrician for panel modifications.

For deeper engineering data on specific melting curves and I²t values, consult the Littelfuse Fuseology Application Guide, which remains the industry benchmark for time-current characteristic analysis. For physical installation and panel spacing rules, always cross-reference the latest edition of NFPA 70 (National Electrical Code), specifically Article 240 regarding overcurrent protection devices.