I need to get a 1.6 amp, "slow blow", 250V, 5x20mm fuse for a piece of equipment.

The ones I bought in the attached picture seem to be the correct ones (according to the store). Sorry for the poor image quality.

I had two quick questions, since I'm new to this:

  • What's the significance of the table (circled in red) of "breaking capacities"? That is, if this is a 1.6 A fuse, why does it show the fuse breaking at higher amperages? I want to make sure the fuse will break at 1.6 A, not higher. Does this all have something to do with the "time delayed" aspect of it, or does it all mean something else?
  • The fuse is marked with the inscription "T 1,6A L 250V". I think that the "T" means "slow blow", or "slow", right? (Time delayed, or something like that). What does the "L" stand for?

Thanks for any infoenter image description here


1 Answer 1


Breaking capacity means that your 1.6A fuse is rated to safely operate up to 35A at 250 VAC.

If the short circuit current exceeds 35A, then it may not safely operate any more and break the current in the time stated in the fuse specification. If you for example had a circuit with more than 250V or more than 35A passes through the fuse, the fuse is not rated to handle that, and current may continue to flow as an electrical arc between the fuse terminals.

But be aware that due to how fuses are marked and depending on their tolerances the fuse will not immediately trip if you test it at 1.6A rated current. It might take hours. At twice the rated current, it may still take seconds.

T means slow acting fuse (Trage)

1.6A is the rated current

L means low breaking capacity, glass fuses are typically in this category

250V is the rated voltage maximum

  • \$\begingroup\$ Thanks -- so the 35A, for example, would be the upper limit to the functionality, and the 1.6 the lower limit? That means (although perhaps delayed), the fuse should break at over 1.6A, but at 35A the whole thing may fail (arcing)? \$\endgroup\$
    – Cerulean
    Jan 12 at 15:10
  • \$\begingroup\$ It is somewhat more complex. If there is ever a possibility to current through the fuse go past 35A, this is a wrong fuse and you need a better fuse. And depending on which standard is used to rate the fuse, it may either be continuously rated to operate at 100% of 1.6A (IEC), or only 75% of 1.6A (UL). If you need the fuse to pass 1.6A, you should get a fuse rated for a bit higher. There is no exact current when it trips, it depends on current, time, temperature, and aging of the fuse. Also any inrush surges need to be considered, or fuse may trip after few hundred cycles. \$\endgroup\$
    – Justme
    Jan 12 at 16:16
  • \$\begingroup\$ Thanks -- it's for a modular synthesizer case, which is plugged into wall current, and they specified a '1.6A type T, 5x20mm' fuse (from this table, doepfer.de/faq/a100_faq.htm#Fuse, case type "A-100PMS6 monster suitcase 6U/168HP"), so I think it's the correct one. \$\endgroup\$
    – Cerulean
    Jan 12 at 16:41

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