Fuses, 2 in series to comply with needed voltage rating

OK I'm not at all sure how this should look, or how it would work. But I can imagine some sort of cut out/ hinge that would allow thermal stress to happen in the fiber glass. That may end up using more pcb area than you can afford. It's hard to know if just a slot would be enough.

George H.

You are very likely right about the violent destruction of one of the fuses

As long as the fuse is destroyed and serves the purpose of protecting the power module then It may do the trick

I've done something similar before which was approved by UL (on single phase power). I cannot disclose the details, but it involves containing the melted metal of the fuse, so it does not propagate to the rest of the electronics.

We actually have custom metal enclosure, so we could design a wall around the fuse which encloses the PCB surface, containing the fuse evaporation

Cheers

Klaus

"- show quoted text - Two fuses in series is absolutely NOT supported anywhere.

A fuse is a fail open device and if you are exceeding its rated voltage, you risk continued conduction via arc after the fuse link itself 'opens' in a failure event.

This isn't about 'pushing limits', this is blatant lack of grasp of the concept, and shows a lack of grasp of electronics as well. "

Unquote

Your statements sound like carved in stone, but I have seen it done before although at other power levels

Such comments are typical from older engineers that no longer come up with ideas of their own by relies on only prior experience ;-)

Regards

Klaus

Explain.

Nonsense. It's more like older engineers understand the failure modes and know what the risks are. If you can point to where UL says it's acceptable to use series 250V fuses in a 500V application, please enlighten us all.

That's rather missing the point. A tiny fuse fails to open on excess v/i, what happens is it keeps arcing. This converts the pcb into carbon, which also arcs merrily. What you get is a firework that doesnt interrupt the power.

IRL fuses might manange more than their ratings, but relying on them to is a gamble.

NT

That's rather missing the point. A tiny fuse fails to open on excess v/i, what happens is it keeps arcing. This converts the pcb into carbon, which also arcs merrily. What you get is a firework that doesnt interrupt the power.

IRL fuses might manange more than their ratings, but relying on them to is a gamble.

Unquote

Since it's 3 phase ac, won't the arcing stop after some milliseconds?

Cheers

Klaus

quote

Nonsense. It's more like older engineers understand the failure modes and know what the risks are. If you can point to where UL says it's acceptable to use series 250V fuses in a 500V application, please enlighten us all.

Unquote

I stated that I have a pending inquiry from UL. If it was written plainly in the standard I would not be inquiring at SED

Cheers

Klaus

Let us know how that works out for you. Complete with *DETAILS* (which you conveniently hide).

Since it's AC, won't the arc restart on the next cycle? Subject change (and missing details) also noted.

You refuse to say what fuse type you are considering, what its ratings are or what sort of fault current is possible.

However, you still expect a precise answer to an undefined question and that answer MUST suit YOU.

OK - I'll oblige.

Your twin fuse idea is brilliant and will work perfectly.

Amazing no-body else ever thought of it.

Happy now ?

.... Phil

More reaslistically, a very large current flows via the arc causing wiring or PCB tracks to explode OR forcing the next fuse or breaker up the line to open.

IOW, an arcing fuse is just as useful as no fuse.

... Phil

Then he was stupid as well, and the entire company if it ever became incorporated into a product.

Fun (custom blast shields) So knowing nothing about arcs, I assume you keep the fuses close (no extra metal bits or capacitance) and figure the voltage will split ~evenly across the gaps.

But what about a slot in the pcb... I drew a pic.

.-. ( )

More about absolute real physics than prior experience, dingledorf.

Call someone at Buss and ask their engineers why NO fully educated engineer would incorporate any such 'idea' into a circuit.

It is there for protection at an absolute value. Your scenario introduces too many variables and even moreso from example to example. It removes the "known behavior" factor and introduces a "catastrophic failure" likelihood.

No engineer anywhere would ever specify such a set-up, and you and your friend must be mere tech wanna be stock for you to simply call it "an idea".

Use some common sense. Remember putting the thin wire across the car battery made it glow and melt? No? I do.

Now imagine a heavy cable, two 3 inch thin wires joined in the center and attached in series to the heavy cable return to the battery.

Current is series, so the current that made the wire glow orange and melt will now fill both small wires. So the same current will make both fuses blow (but only one will).

"Such comments" as yours indicate an arrogant adolescent minded dork, at best, and a mosh pit punk isn't far off that step stool either.

You are not coming up with any magic, child.

I can't believe you are actually serious with that question.

Why 250V? Use a string of 32V automotive fuses for an even more impressive, plasma induced fire.

Cost effective, too!

no, thats what breaking capacity means. Exceed it and it just keeps going, and growing as more material becomes carbonised and/or gets into the arc. Arcs do run on ac.

NT

You probably can.... 100 fuses in series would likely work lol. They'd all melt into 3 big blobs that would fall out of the way :)

NT