Re: Glass fuses.

In message <1141500650.327289.319450@xxxxxxxxxxxxxxxxxxxxxxxxxxxx>, Frank Wood <frankwood95@xxxxxxx> writes
This is a tricky subject. Ceramic and sand-filled fuses will handle much larger instantaneous fault currents, but have much more thermal inertia. This may not protect the equipment in time to save it.

The thermal inertia is nothing compared to the sustained arc through the glass tube. There are FF rated fuses for semiconductor loads, but quite frankly it's still hit and miss whether a standard triac will survive a blast.

On my own gear I make the triacs as easy to replace as a fuse and generally include basic onboard diagnostics to guide the technicians to the fault. A triac costs less than an FF fuse! In the pro stuff I use MCB's. I used to use type "A" for their close load protection, but it's debatable whether they provide any real advantage over the much easier to source "B" characteristic breakers. Nowadays I go one step further and use 10,000A fault breaking capacity industrial breakers.

15 years of three phase 240/415 lighting controllers for the ride industry and the first units are still working hard around the world. Not bad even if I say so myself.

--
Clive Mitchell
http://www.bigclive.com
.

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