500A fuse burned in half. Any thoughts on pix?
500A fuse burned in half. Any thoughts on pix?
(OP)
The pictured Bussman FLS-R 500A fuse was installed in a Square D I-Line bus plug-in disconnect feeding an ABB DCS401.0500 drive (rated 408 AC amps/phase) driving a Reliance "Super RPM" 250 HP, 500V/400 FLA motor in a plastics extrusion screw application. The drive itself is protected with fast-clearing semiconductor fuses, and they were not affected.
I was not involved in the fuse replacement, and don't know which pole it was installed in, or it's specific orientation (although it is installed along the horizontal axis, rather than vertically).
For approximately two weeks before the fuse burned in half the drive would shut down approximately every two or three days. Unfortunately, instead of checking fault code(s) after shutdown the drive was power-cycled to clear the fault, and diagnostic information was lost. Since fuse replacement these "mystery" shutdowns appear to have ceased.
My best guess based on heavy oxidation on only half of the links is this fuse was leaking filler material, exposing progressively greater fuse element surface area to the air, and these oxidized elements developed higher resistance. Over time this process avalanched, and eventually the fuse dropped enough power for it to burn apart.
http://f iles.engin eering.com /getfile.a spx?folder =64368553- ac7e-4441- 93ff-abf2e 1cfe757&am p;file=fus eview1.jpg
http://f iles.engin eering.com /getfile.a spx?folder =1f61d3ad- 6a75-4ac2- b15c-6ccec ed86764&am p;file=fus eview2.jpg
Does that scenario seem likely? Has anyone else seen a fuse failure like this?
I was not involved in the fuse replacement, and don't know which pole it was installed in, or it's specific orientation (although it is installed along the horizontal axis, rather than vertically).
For approximately two weeks before the fuse burned in half the drive would shut down approximately every two or three days. Unfortunately, instead of checking fault code(s) after shutdown the drive was power-cycled to clear the fault, and diagnostic information was lost. Since fuse replacement these "mystery" shutdowns appear to have ceased.
My best guess based on heavy oxidation on only half of the links is this fuse was leaking filler material, exposing progressively greater fuse element surface area to the air, and these oxidized elements developed higher resistance. Over time this process avalanched, and eventually the fuse dropped enough power for it to burn apart.
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Does that scenario seem likely? Has anyone else seen a fuse failure like this?





RE: 500A fuse burned in half. Any thoughts on pix?
Keith Cress
Flamin Systems, Inc.- http://www.flaminsystems.com
RE: 500A fuse burned in half. Any thoughts on pix?
Every type and manufacturer of drives that I have used has a list of history faults on the drive. Powering down the drive does not clear these faults. Usually there are at least 5 faults in the history section of the drive for display.
RE: 500A fuse burned in half. Any thoughts on pix?
If your fault current exceeds the interuption rating of your fuse it will end up looking just like the picture you posted.
Have you tested the cable from the bus plug to the VFD? Since the VFD fuses were not affected I would guess the cable faulted, the motor contributed to the fault and the fuse interuption rating was exceeded.
RE: 500A fuse burned in half. Any thoughts on pix?
Gunnar Englund
www.gke.org
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100 % recycled posting: Electrons, ideas, finger-tips have been used over and over again...
RE: 500A fuse burned in half. Any thoughts on pix?
My first GUESS would be the same as Keith's - the fuses overheated due to high contact resistance, either external or internal.
RE: 500A fuse burned in half. Any thoughts on pix?
It could have been a bad fuse. I've seen a burn out failure like that before with a few different medium voltage fuses.
Also, not familiar with that particular fuse. Does it have a minimum melt current? Some fuses do not provide full-range protection.
RE: 500A fuse burned in half. Any thoughts on pix?
Roy
RE: 500A fuse burned in half. Any thoughts on pix?
In response to Controldude's observation ... checked the manual, and they list the 'faultlogger' function as non-volatile, and 16 items "deep". Forgot to look at the log today (the tech mentioned he received a "Mains Undervoltage" fault, so that should at least be in the log), but did survey it about a week before the fuse failure, and all 16 items were '0' (no fault).
The failed fuse had been mounted in the upper position of the bus switch.
All three fuses were replaced with FLS-R 500A fuses.
However, a Bussman NOS-600 (!) single element, 10 KAIC, class H fuse was originally in the center position, and another FLSR 500A was in the bottom position.
I was wrong about the FLSR fuse being manufactured by Bussman. The failed fuse label was mostly destroyed, but checked the other one, and learned it is actually a Littelfuse part number for an RK5 dual-element time delay fuse, 600V, 200 KAIC.
http://www.littelfuse.com/part/FLSR500.html
Maybe I'm looking in the wrong place, but can't find the characteristic curves for it, and gave up after about 5 minutes. Everything seems to point back to the above cut sheet.
The Square D plug-in disconnect uses spring-tensioned fuse holder fingers (rather than a bolted connection; guess they start using them at 600A and higher), and the technician related all three replacement fuses required considerable force to push in.
This suggests inadequate force on the fuse tabs didn't play a role in the original failure. Also, while there is some heat discoloration on the failed fuse tabs it appears to have migrated from the overheated fuse body, rather than being generated within the holder fingers. Nevertheless, it won't hurt to shoot it with an IR camera next time time allows.
I'm having a hard time with my original failure theory. The notion of heavily oxidized elements being due to loss of filler doesn't sound likely unless the fuse was in a 'bolted' orientation (which puts the heavily oxidized element towards the top). Plugging it into a spring clamp holder throws orientation out 90°. Also, it uses rather large grain silica sand (dissected the other one salvaged from that night) and I'd have a hard time believing it was prone to leakage.
On the other hand, the mystery NOS 600 fuse was leaking finely powered borax like crazy.
Tending towards believing it was an internal high resistance connection where the corroded set of element foils connected to the center piece.
In a couple of weeks I'm going to be doing a couple of changes to this drive, and will inspect everything with the proverbial fine-tooth comb.