[analog97]

Hi.  I must replace a blown amplifier fuse and am struggling a tad.  The fuse is a 10A/250V glass fuse, a short one about 5/8" long.  In looking thru the Mouser catalog, there are several to choose from, slow-blow and fast acting as well as 2 different "interruptor ratings" of 1500 A and 35 A.  I am guessing I need a fast acting fuse, but I don't get the "interruptor rating" concept.  Any help appreciated.  TIA!!

[hagtech]

It sounds like a 5mm x 20mm metric size.  Me don't know anything about interruptor ratings.  But I bet WikiPedia can explain it.

jh

[analog97]

I never used Wikipedia, but you were correct, Sir.  It seems hard to fathom a small fuse such as the one I need can stop 1500 amps!  It also seems odd that I am given a choice between 35 amps and 1500 amps for the interruptor rating.  Here is the definition of "interruptor rating":


Interrupting rating

A fuse also has a rated interrupting capacity, also called breaking capacity, which is the maximum current the fuse can safely interrupt. Generally this should be higher than the maximum prospective short circuit current. Miniature fuses may have an interrupting rating only 10 times their rated current.


Sorry to take your time away from artful engineering!

[Wayner]

The number one job of a fuse is safety. There are many electrical devices that have different requirements because they have different behaviors within an electrical circuit. A device with a simple 12 volt power supply and a very simple inductive circuit can be easily calculated for proper amperage protection for devices and wire guage. When a circuit has a thing like a motor, things get a little weird. Motors have high inrush current and a "normal" fuse with too low a rating will cause nusance blowing. That is why they make fuses like "slow-blo". They will take the high inrush current for a longer time (which will not melt the wiring infrastructure) and still be protective. Alway replace the fuse in your HI-FI system with the same type and rating. That has been calculated for you by an electrical engineer and if you are not one, it's none of your business to determine the correct fuse.  aa

[samplesj]

The number one job of a fuse is safety. There are many electrical devices that have different requirements because they have different behaviors within an electrical circuit. A device with a simple 12 volt power supply and a very simple inductive circuit can be easily calculated for proper amperage protection for devices and wire guage. When a circuit has a thing like a motor, things get a little weird. Motors have high inrush current and a "normal" fuse with too low a rating will cause nusance blowing. That is why they make fuses like "slow-blo". They will take the high inrush current for a longer time (which will not melt the wiring infrastructure) and still be protective. Alway replace the fuse in your HI-FI system with the same type and rating. That has been calculated for you by an electrical engineer and if you are not one, it's none of your business to determine the correct fuse.  aa

?

Your canned response doesn't actually address the original poster's quetion at all.  While its obvious you want to crusade against magic fuses, at no point did the original poster say he was "upgrading" the fuses.  Instead he said he had a fuse blow and needed to replace it.  He specifically asked about interruptor rating, which was a new one for me too.  I guess it makes sense that at some current level it will arc, but I'd never have thought about it mattering (IE the breaker is going to flip first).

While he isn't sure he needs a fast or slow blow, a fast blow replacement is safe.  It may not work worth a hoot because it nusiance tripps all the time, but it is a safer bet.

Also note what circle this is, which means he did in fact ask an engineer (JH).

[analog97]

"it's none of your business to determine the correct fuse. "

HEY, lighten up on me.  I am not an EE, nor do I pretend to be.  I am just a measly,  PhD biomedical scientist whose hobby is analog and supporting analog engineers like JH.  The fuse I am attempting to replace is blown.  Of course, I am trying to replace it with an exact replacement.  The problem is that all the markings on the fuse said "250V/10 amps".  So, I looked up a replacement in Mouser, and that is when I ran into the so-called "interruptor ratings".  So, I had to choose between a 35 amp rating and a 1500 amp rating.  No labelling is apparent on the PCB or the fuse for this.  So, being a thoughtful kinda guy, I thought I'd ask this forum.  Without an answer, I will try a fast-acting, 10A high-interruptor rating fuse.  Please don't bother to respond if you're just gonna take a shot at a non-EE.

[amandarae]

here's another definiton!

Interrupting Rating (Abbreviated I.R.)  
Same as breaking capacity or short circuit rating. The maximum current a fuse can safely interrupt at rated voltage. Some special purpose fuses may also have a "Minimum Interrupting Rating". This defines the minimum current that a fuse can safely interrupt. Safe operation requires that the fuse remain intact. Interrupting ratings may vary with fuse design and range from 35 amperes AC for some 250V metric size (5 x 20mm) fuses up to 200,000 amperes AC for the 600V industrial fuses (for example, ATDR series).

The 35 amps should work fine.

regards,

Abe

[analog97]

Thanks, Abe.  I'll try that.  Regards.

[Wayner]

Did you ever consider contacting the amplifier manufacturer for replacement fuses? I wouldn't put a 35 amp fuse in.

 

[samplesj]

Did you ever consider contacting the amplifier manufacturer for replacement fuses? I wouldn't put a 35 amp fuse in.

 

IT IS NOT A 35 AMP FUSE!

Read the post before you go off half cocked.

[analog97]

Thanks, Samplesj for helping to "de-fuse" this ridiculous banter.  I tried to make my questions clear in the posts! I am finished now, and will conclude by ordering another Hagtech product so I can include a few fuses (yes, 10AMP, fast-blow) in my Digi-key order.  Thanks to all who tried to help.

[hagtech]

I still find this "interrupter" rating confusing.  Perhaps they mean that the fuse will pass 35 amps for a short duration without blowing?   And then blow at the normal (say 1 amp) load given enough time?  Normally, it takes awhile (up to a second or more) for a fuse to heat up and melt at the specified rating.  The higher the current, the less time it takes. 

And so I think some more about fusing.  They sell these audiophile grade fuses now.  HiFi-Tuning, etc.  Wondering how these work better.  Just how audible is the difference?  At first glance it would seem impossible.  But look closer.  The fuse element itself has certain characteristics that might affect sonics.  It has a resistance, which is likely proportional to temperature.  For sure, the load current varies and hence temperature is in constant flux, in either 60Hz or 120Hz cycles.  As input capacitors get charged, the fuse heats up.  Then it cools again as we get a zero crossing on the ac line voltage.  So the change in resistance is dynamic and a function of drawn ac line current into the primary.  This will be different for each amplifier.  My new choke rectified machines will have much less noticeable effect, as the input current is much more constant.  Is there a sonic difference between blade and wire types?  I see several different element constructions.  I would think the flat blade wire type could be best, but I am only guessing.  Anyway, I see a dynamic circuit element.  It ain't no piece of wire.

Curious if any of you have experimented with fuses, making some sort of general classifications as to which constructions are best.

jh

[samplesj]

I still find this "interrupter" rating confusing.  Perhaps they mean that the fuse will pass 35 amps for a short duration without blowing?   And then blow at the normal (say 1 amp) load given enough time?  Normally, it takes awhile (up to a second or more) for a fuse to heat up and melt at the specified rating.  The higher the current, the less time it takes. 

I'd never seen it at all, but based on the two definitons earlier in the thread I was seeing it as a arc limit.

A bit more digging makes it look like its the lower of the arc limit, or rupturing/other the damage to fuse holder limit.

So if we assume a 10A fuse with 35A interruption rating then
9A no issue
11A fuse blows
36A either arcing from one end to the other OR rupturing/damage to the fuse holder

[analog97]

It is curious, isn't it?  A biologist gets confused and poses a question to an engineer.  I like that!  Jim, FWIW, my intuition tells me that some marketing may be involved here.  It seems inconceivable to me that any 5x20 glass fuse with a thin wire inside could be used in an application where 1,500 Amps could be aborted!  !!That's like hooking up an 80 horsepower motor or 100 portable electric heaters to a PCB.  I don't get it, but hey I'm just a biologist.  Your fascination with the sonics of fuses I will leave to an artful engineer.  My thanks to your being open on this forum to a non-EE.