Knife fuse bursting apart

[frank cinker]

What would cause a 200 amp (250 volt) knife fuse to burst apart and smolder upon apparent overload? Could it just simply be that the fuse was very old?

 

[mdshunk]

Re: Knife fuse bursting apart

I've seen this happen on a few types of fuses a few different times. At least one occurance was attributed to a lightning strike.

 

[tshea]

Re: Knife fuse bursting apart

Originally posted by frank cinker:
What would cause a 200 amp (250 volt) knife fuse to burst apart and smolder upon apparent overload? Could it just simply be that the fuse was very old?

I've seen this happen, also. Fuse was very hot and conducting minimal amount of current. The lights were dim and flickering like in old scifi movie. Discovered a few things that day.
Bad fuseholders, loose connections on wiring and the worse part was one of the "renewable" fuses had 10,000+ Amp rating. Somebody figured how to jam a copper tube in the fuse holder.

 

[bphgravity]

Re: Knife fuse bursting apart

I would imagine this was more of a result of a ground-fault or short-circuit rather than a simple overload.

 

[Leitmotif]

Re: Knife fuse bursting apart

What was the circut voltage?? Did someone put a 250 V fuse in a 450V (or higher) circuit?

 

[LarryFine]

Re: Knife fuse bursting apart

Originally posted by tshea:
Fuse was very hot and conducting minimal amount of current. The lights were dim and flickering like in old scifi movie.

Sounds like the only current was arcing current.

 

[frank cinker]

Re: Knife fuse bursting apart

Leitmotif,

The voltage was correct, 250 volts. The 200A knife fuse looked very, very old. That's what lead me to believe it was just the fuse. It seems fine now after fuse replacement.

 

[steve66]

Re: Knife fuse bursting apart

I think a bad connection at the fuseholder could cause this. If there is 200A flowing, and say 0.1 ohm at the holder, that translates into 4000W of heat at the fuseholder. Subject an old fuse to that much heat, and it probably would self destruct.

Steve

 

[charlie b]

Re: Knife fuse bursting apart

Originally posted by steve66: I think a bad connection at the fuseholder could cause this.

I agree. I think it is even possible that the "bad connection" might have been caused by corrosion, either on the fuse's ferrules or on the fuse holder.