Test Equipment Anonymous

Zenith wrote: ↑Tue Apr 01, 2025 11:04 pm I've seen very high value (100A plus) fuses filled with sand (or something). I assumed it was there for quenching. When it blows you want it to stop conducting, not to continue as an arc.

Diazed fuses (Siemens invention from the early 1900s) as used in Sweden and Germany (Among many other places!)
are sand filled, down to the household sizes of 6,10,16 A.



Most domestic fuse panels in Sweden have D II fuses.



These days, they're being installed only in select places. Most domestic uses have replaced them with DIN rail mounted MCBen.

Some of the old UK power circuit fuses had the wire running through an asbestos tube. I've also seen asbestos used around the fuse in some domestic radios.

The granualar material in high rupture current fuses isn't so much for arc quenching (stopping conduction) as energy absortion to stop the fuse physically exploding. It presents a large surface area to the hot expanding gases cooling them and reducing internal pressures.

AVGresponding wrote: ↑Sat Apr 05, 2025 9:31 am All modern HRC fuses have some sort of filler for arc quenching. It shouldn't be sand: https://www.electricaltechnology.org/20 ... types.html

They mention a number of fillers in articles about HRC fuses; silica (purified sand), marble (calcium carbonate), Plaster of Paris (calcium sulphate). The wire is made of silver (which must be for good reason) and they talk about the metal vapour reacting with the filler to create an insulating compound. No doubt the other effects mentioned are also taking place.

There must have been a lot of R&D done on getting these right.