# fuse ?

Discussion in 'General Electronics Chat' started by Mathematics!, Nov 15, 2009.

1. ### Mathematics! Thread Starter Senior Member

Jul 21, 2008
1,022
4
Ok , I am wondering about the voltage rating on a fuse.
What I looked up is this rating is the rating if exceeded can cause the air/gas to ion's and for the electrons to arc over the broken fuse.
So this would imply it would still be conducting and the circuit would never be broken even when the fuse has blown.
( this is all provided we exceed the voltage rating)

If this is true can this arcing occur indefinitly or just for a split second like lighting does?

If it can occur indefinitely then really no fuse can be 100% safe to break a circuit?

Same question but with circuit breakers can they be prone to arcing?

When buying a fuse I always ever was worried about amperage but now I am looking for voltage ratings as well. When I install house fuses and breakers I don't have any clue on the voltage ratings they just tell you the amperage 15 , 20 ,25 ,30 ,40 ,...etc . Curious to know the voltage rating of these house fuses? Probably in the 1000 volt range though just to be safe.

I see in stores they sell fuses that are 5 amps 32 volt and 5 amps 240 volt. Why would anybody ever want the 32 volt one over the 240 volt one? Won't the high the voltage rating the better for the same amp fuse?

Also once arcing occurs in a fuse if it stops arcing can it start arcing again or does once the air turn into a plasma state it cann't have no clue here?

Thanks for any help in clearing these questions up.

Jan 28, 2005
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3. ### beenthere Retired Moderator

Apr 20, 2004
15,808
295
The fuse voltage rating is a guarantee that the link will blow clear at that voltage level. A 120 volt fuse in a 12 volt circuit might not clear, but a 32 volt rated fuse will.

Breakers can and do arc, but the voltage across them (if AC) will fall to zero periodically. That tends to let the arc go out. Really big switchyard breakers use gas jets to blow out the arc.

4. ### Mathematics! Thread Starter Senior Member

Jul 21, 2008
1,022
4
wait so a fuse will blow if you exceed it voltage rating?

Example you can have a fuse rated at 5 amps 32 volts and what happens the load is geting 3 amps with 40 volts. You would be still under the amp rating so the fuse wire won't burn out. But would it still break because you exceeded the voltage rating?

I don't get it thought the higher the voltage rating the safer because it would be harder to arc you would need more voltage to do the arc???

5. ### GetDeviceInfo AAC Fanatic!

Jun 7, 2009
1,623
240
your electrical code will dictate what voltage rating a fuse must be. It also speaks to current ratings, of which there are two. One being the calibrated opening current, and the second being the value of current that could be present, which is more of a concern for fuse erruption. There are many different styles of fuses, and consideration is given for thier various characteristics.

The code may refer to a certification boards specifications, such as UL.