Fuse failures

[T.M.Haja Sahib]

If available fault current is low then maybe a current limiting fuse is not needed in the first place.

A misapplication of the fuse in that case.

Besides when there is fault current don't we want fuses to "fail"

There is a difference between operation of a fuse and failure of the same.

 

[iwire]

There is a difference between operation of a fuse and failure of the same.

Is there?



The job of a fuse is to protect the conductors as long as the fuse opens it has done its job and has not failed.

 

[T.M.Haja Sahib]

Is there?

Yes.Even one or two cases highlighting it were mentioned in this thread.

 

[T.M.Haja Sahib]

Two simple tests to ascertain the health of a fuse in a given batch.First test.The fuse should not blow for current up to 140% of its rated current within one hour.Second test.The fuse should blow for current beyond 160% of its rated current within one hour.Of course the second test can not be performed on all fuses in the batch but only on a select few.

 

[iwire]

Two simple tests to ascertain the health of a fuse in a given batch.First test.The fuse should not blow for current up to 140% of its rated current within one hour.Second test.The fuse should blow for current beyond 160% of its rated current within one hour.Of course the second test can not be performed on all fuses in the batch but only on a select few.

Again, what type of fuse are you going on about?

The point at which fuses open depends on the fuse.

 

[T.M.Haja Sahib]

Again,all fuses.
Do you have any difference of opinion on this?

 

[iwire]

Again,all fuses.
Do you have any difference of opinion on this?

Yes, I do.

Your tests described here are meaningless and pointless without knowing about the fuses characteristics.

Two simple tests to ascertain the health of a fuse in a given batch.First test.The fuse should not blow for current up to 140% of its rated current within one hour.Second test.The fuse should blow for current beyond 160% of its rated current within one hour.Of course the second test can not be performed on all fuses in the batch but only on a select few.

Look at this graph of a common fuse here

http://www.cooperindustries.com/con...Resources/Data Sheets/Bus_Ele_DS_2011_BAF.pdf


Now compare it to the slow blow version here

http://www.cooperindustries.com/con...Resources/Data Sheets/Bus_Ele_DS_2028_FNM.pdf


What do you notice?

1) The fuses are very different

2) Per design both would fail your test 1.

3) Per design both would pass your test 2

This makes your test pointless.

 

[T.M.Haja Sahib]

Unfortunately,both the links do not open.
The controversy is about test-1.
Is it possible to reproduce the curves here?
or
What is the time period for 140% current through the fuse as noted from the fuse curve?

 

[iwire]

Unfortunately,both the links do not open.

Strange they work fine for me.

The controversy is about test-1.

Actually both test 1 and 2

What is the time period for 140% current through the fuse as noted from the fuse curve?

For what type and manufacturer of fuse, every fuse type is different.

 

[T.M.Haja Sahib]

Strange they work fine for me.

It happened earlier also.

Actually both test 1 and 2
For what type and manufacturer of fuse, every fuse type is different.

Any one fuse curve negating the tests would do.

 

[iceworm]

Disclaimer: I am not a "fuse guy". So please bear with me and correct/educate me if I use a term in the wrong context.

... If no,I think the rupturing capacity of the fuse might have been exceeded so that even though the fuse failed catastrophically,it nevertheless caused no damage to the downstream equipments it protected.Correct?

TM -

Look at a fuse curve - pick one that shows a band instead of a line: On the left side the line shows where the fuse starts to melt. The line on the right side of the curve, the fuse is guarranteed to be melted clear.

If the selected curve is a line instead of a band, then there will be words telling about the melting to opening time tollerances.

In both cases there will be test specs with the X/R ratio, voltage, temperature.

Now let's look at all of the posts with anecdotal catastrophic failures:
I read all of the posts about the blown up, burned up fuses, and all appear to be mis-applied (application out of fuse spec to interupt), or poor contact fuse holders, or in the case of expulsion type - worn out.

So, if you are telling me that a miss-applied, poorly installed fuse, used near the rating limits, it may explode. If that is so, I am going to say, "So what? Why would you expect anything different? If one is planning to mis-apply any piece of equipment Why would anyone ever think they would know what exactly what it would do.

So, here is the question: The term "rupturing capacity" has been used in several posts and I am not familiar with it. I have looked a lot of fuse data sheets and I do not recall ever seeing a column marked "rupturing capacity". Can you give me a definition?

If this is meant to be some sort of an i^t value, am thinking that a fuse will stand any i^2t value along fuse curve line where it is rated to open.

ice

 

[iceworm]

... Because the problem is on heating, the paper emits conductive vapor which on being absorbed by sand makes it in turn conductive.The result is when the fuse tries to interrupt a fault current,the fault current may continue flowing through the sand even after the fuse element is broken!

This is another one I have neve heard of. This is a problem when one has lived such as a sheltered as I.

Do you have any publish data or even your own test data that shows the sand turns conductive?

ice

 

[T.M.Haja Sahib]

Yes, I do.

Your tests described here are meaningless and pointless without knowing about the fuses characteristics.



Look at this graph of a common fuse here

http://www.cooperindustries.com/con...Resources/Data Sheets/Bus_Ele_DS_2011_BAF.pdf


Now compare it to the slow blow version here

http://www.cooperindustries.com/con...Resources/Data Sheets/Bus_Ele_DS_2028_FNM.pdf


What do you notice?

1) The fuses are very different

2) Per design both would fail your test 1.

3) Per design both would pass your test 2

This makes your test pointless.

If a straight vertical line is erected at 140% of rated current of a fuse say 1A in the above common fuse curve,it is almost parallel to the fuse curve.Same is true for any other fuse curve including the slow fuse type.So what is your problem here?

 

[Besoeker]

If a straight vertical line is erected at 140% of rated current of a fuse say 1A in the above common fuse curve,it is almost parallel to the fuse curve.

Which shows 100 seconds on the vertical axis. I think that one hour is actually 3,600 seconds.

 

[iwire]

If a straight vertical line is erected at 140% of rated current of a fuse say 1A in the above common fuse curve,it is almost parallel to the fuse curve.Same is true for any other fuse curve including the slow fuse type.So what is your problem here?

So you choose to ignore the difference in time.

So in your view the normal fuse and the slow blow fuse are the same. Interesting.

 

[T.M.Haja Sahib]

Which shows 100 seconds on the vertical axis. I think that one hour is actually 3,600 seconds.

Guess why it stopped at 100 seconds,but I really detest spoon feeding.

 

[T.M.Haja Sahib]

So you choose to ignore the difference in time.

Interesting.

I am afraid you do not understand the purpose of test-1 on a fuse.Care to explain in your own words?

 

[Besoeker]

I am afraid you do not understand the purpose of test-1 on a fuse.Care to explain in your own words?

First you tell him he doesn't understand then you ask him to explain.....
Surely you can see the paradox with your logic?

 

[Besoeker]

Guess why it stopped at 100 seconds,but I really detest spoon feeding.

I feel much the same way about rudeness and willful ignorance.

Here are a couple of pictures of the fuses which you had trouble with the link.

How would the 3A fuse fare at 100 seconds with your tests in post #84?

 

[T.M.Haja Sahib]

How would the 3A fuse fare at 100 seconds with your tests in post #84?

I requested you to find for yourself why the fuse curves stop at 100 seconds.

You did not.

The reason is the curve become almost parallel to the vertical line erected at 140% of rated current of each fuse.