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Hot fuses?
08-09-2013, 11:49 AM
Post: #1
Hot fuses?
[/font] I have a question that is making mesay “HMMMM!”. I have attached IR images, thermal reports and awiring diagram. The diagram (see attachment “diagram”) shows we areheating 4500 Watts of 240 volt heaters. Our problem is overheating offuses FU223 and FU226. These were replaced because of terminal heating ofthe fuse holders and were using LP-CC-25 fuses (see attachment “5-2-13”). The connections were re-torqued with no change. This past weekend wereplaced the fuse holders with compact disconnects CCP-1-30M and inserted fusesFWC-25A10F. The thermal post repair examination indicates aneven thermal issue (see attachment “8-9-13”). Current readings on bothoutputs are 19.3A. The fuses are slightly discolored.

I'm at a loss. Any ideas?[font=Times New Roman]


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.pdf  5-2-13.pdf (Size: 972.65 KB / Downloads: 54)
.pdf  8-9-13.pdf (Size: 984.17 KB / Downloads: 46)
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08-09-2013, 11:59 AM (This post was last modified: 08-09-2013 12:39 PM by acardoso.)
Post: #2
RE: Hot fuses?
How did you measure the current? With a TrueRMS?
What is side by side with the fuses? Can it magnetic induction?
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08-09-2013, 12:17 PM
Post: #3
RE: Hot fuses?
I used a clamp on ammeter. We don't have any power analizing equipment.

Richard "Rookie" Hoyer
EnerSys, Inc.
Warrensburg, MO
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08-12-2013, 10:29 AM
Post: #4
RE: Hot fuses?
I would double check that the heaters are actually 4500 watts, maybe one is partially shorted. The amperage if accurate is high and can expect some heating but the connections at the fuses at this amperage is unforgiving. must be claen and tight. the images are a bit unfocused so any measurements of temperaturea re inaccurate. but the general heating is still imageable.
J
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08-12-2013, 11:35 AM
Post: #5
RE: Hot fuses?
The heaters are definatly 4500 Watts. The connections were cleaned when the holders were replaced. I personnally torqued the connections to the Compact Disconnects specifications.

Richard "Rookie" Hoyer
EnerSys, Inc.
Warrensburg, MO
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08-12-2013, 02:52 PM
Post: #6
RE: Hot fuses?
Fuses, by their design, are meant to run warm. Their function depends upon melting the internal "wire". Some fuse wires melt down below 300 or 400 degrees, but most are designed using materials with melting points from 500 to 1 or 2 thousand degrees. Not knowing what type is inside your fuseholders, I'm not surprised that a fuse operating at 80% of its rating is getting that hot. Especially since it appears that the holder you're using is of the type that encloses the fuse (making it harder for the heat to dissipate).
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08-13-2013, 02:20 AM
Post: #7
RE: Hot fuses?
Like IRJAY says, I would be more concerned about the cables.

To me 80% FL is high, and I agree with EDAZ22, they are bound to be hot. Some things are supposed to be hot, and a fuse operating at 80% FL is one of those things.

I would replace the cables with a larger size, as a first step. Then I would consider using a different type of fuse unit and perhaps a larger (or different type) of fuse.
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09-12-2013, 01:18 PM
Post: #8
RE: Hot fuses?
I work at a mine and i usually run into the same problem with 480v buckets. It is usually a bad connection or small wire size, or its even different manufacture fuses. I concure with EDAZ22 and Bobberry. try uping the wire size. Loose and Dirty connections are a big problem where i work. stranded 12AWG, 10AWG wire needs to be twisted before insurted into the connection point. 8AWG and up not so much just needs the proper lug size.
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12-19-2013, 03:37 PM
Post: #9
RE: Hot fuses?
It appears that there are either control power transformers or starters next to the fuses in question, it is difficult to tell from the picture. I would suspect that a lot of the heating is due to the radient heat from those as well as being from the normal function of the fuses. I would try sliding a piece of plastic between them and see what happens to the temperature.
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10-22-2014, 05:10 PM
Post: #10
RE: Hot fuses?
It looks like a bad connection to me. The current flowing through that wire is the same current flowing ALL ALONG THE WIRE. So if the wire were undersized, it would be hot everywhere along the wire. But there's that gradient that I can see.

I mean, think about it..2 feet of wire..short it out on a battery (high current)..and look at the temperature anywhere on the wire and it should be the same all along it. An electric heater for example glows the same all along the nichrome element. That's NOT what you see in the photo.


Do this (CAREFULLY!): Measure the voltage drop across that bright area. It should be close to zero volts. Really you're looking for I-squared-R loses..or power..which is heat.

I'd think if it were radiant heat, it would be more uniform.

I'm not familiar with your exact situation so just take this as something to CHECK--not necessarily the solution.
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