Fuse: fast blown vs slow blown

The most important piece of safety equipment anybody has is a fully functional brain. ;-)

Cheers! Rich

Personally, I wouldn't depend on them, but I don't know what industry guidelines are. Leather is only animal skin, after all.

Cheers! Rich

Well, then I guess a lot of people are in a world of s*it!

Jamie

If they slept well.. Some jobs demand shift duties, affecting your sleep and hence your safety.

-- @~@ Might, Courage, Vision, SINCERITY. / v \ Simplicity is Beauty! May the Force and farces be with you! /( _ )\ (x86_64 Ubuntu 9.10) Linux 2.6.39 ^ ^ 15:30:01 up 10 days 32 min 0 users load average: 1.08 1.08 1.06 ???! ???! ???! ???! ???! ???! ????? (CSSA):

From Alcoa employee: the utility breaker was mounted on top the towers and simply bolts in place with the surface the contact. Once bolted, no oxide can form.

From memory [can somebody find the reference number and post the waveform], British Telecom Spec defined the 'boundaries of the voltage waveform at the EUT's terminals and added that 350+A is available during the waveform. During fuse blowing, the GND went down to -10 and the -48 came up to -20, then pops with a risetime [can't remember the risetime] GND goes positive 30 or 40V and the -48 goes way down to

-300, or -500V and then decays back up to above -60 volts in 50mS. That is a VERY long time for electronics.

The energy is approx 1/2 * 300V * 350A * 0.05 =3D 2600 joules When you consider that the large protection MOV's inside your PC power strip are rated for 5 - 10 j; you have some idea of the energy potentially shoved into a telecom unit.

From memory and my understanding that the origin of the spec came about after ....Telecom equipment are placed in racks in a room, the batteries are usually in another room and 1 inch diameter rods go from the batteries through the wall to the equipment room. At the equipment room cables go down to the rods and simply clamp on the rods to get power to an individual rack. A workman dropped his wrench across the rods. The wrench was never found. The surge described in the spec probably occurred, or worse, so the WHOLE room of equipment blew out, destroyed. Since British Telecom had purchased all the equipment without that power surge specced, British Telecom had to eat the loss, thus the origin of the spec in future BT purchases.

The fuse and wiring and solenoid would pass up to 350 Amps, but not for long, before the fuse disappeared. By the way, the coil of wire would 'jump' up off the floor when the fuse went. When I first built up the equipment, I insisted on placing everything inside a separate room and activating remotely, just in case we lost a battery! We never lost a battery. Turned out luckily to be an unnecessary precaution.

Somewhere on the internet there must be pictures/videos of fuses blowing under extreme current conditions. In such a picture, I remember seeing a 'cone' of blasted metal progressing from some weak point in the wire along the wire until most of it was gone. Plus blowing a fuse in a controlled magnetic field will yield very destructive EMP. Do a search for such weaponry. Perhaps, videos are there.

Regards, Robert

(Snip installation details of stunningly huge over-current protection device)

Sounds like the geometry and pressure used for the contact surfaces was such that it broke through existing aluminum oxides and created a gas - tight seal in the connector area. Sounds simple if you don't have to actually design to achieve that effect. :)

(Snip effect of shorting huge batteries through an inductor)

Thanks! Very interesting!

--Winston