# Fuse failures

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#### T.M.Haja Sahib

##### Guest
Bes:
I want to submit that, unfortunately,you too do not seem to grasp the purpose of test-1 on a fuse.Do you?

#### iwire

##### Moderator
Staff member
Bes:
I want to submit that, unfortunately,you too do not seem to grasp the purpose of test-1 on a fuse.Do you?

And I submit that you seem to be over looking the fact that a fuse that can hold 140% of its rating for one hour is not a normal fuse. All the fuses I install would fail the test you describe below.

First test.The fuse should not blow for current up to 140% of its rated current within one hour.

#### Besoeker

##### Senior Member
The reason is the curve become almost parallel to the vertical line erected at 140% of rated current of each fuse.
Look again at the curve for the 3A fuse. At what current does it cross the 100 second line?
It's a simple question and I have posted sufficient information for you to work it out.
Can you?
And, if so, what is it?
And how does that relate to your 140%?

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#### T.M.Haja Sahib

##### Guest
All the fuses I install would fail the test you describe
Is it a conviction or a confirmation?

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#### T.M.Haja Sahib

##### Guest
Look again at the curve for the 3A fuse.
Please look at again at my post below and try to answer and that would clear up any misgiving,I am sure.
Bes:
I want to submit that, unfortunately,you too do not seem to grasp the purpose of test-1 on a fuse.Do you?

#### Besoeker

##### Senior Member
Please look at again at my post below and try to answer and that would clear up any misgiving,I am sure.
Would the 3A fuse pass your test?
That's just yes or no.

#### iwire

##### Moderator
Staff member
Is it a conviction or a confirmation?

You propose that all fuses should be tested at 140% of there rated value for 1 hour.

What I am telling you is most standard fuses in use in America would fail before that hour.

There should fail be for that hour

If they did not fail before the hour was up there is something wrong with the fuse.

Why not pick a particular fuse that you would work with, post its specifications and we can discuss it?

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#### T.M.Haja Sahib

##### Guest
Would the 3A fuse pass your test?
That's just yes or no.

Can you believe the obvious answer here is liable to mislead?

So try to answer my question first.

#### Besoeker

##### Senior Member
Can you believe the obvious answer here is liable to mislead?
If it's obvious then just spit it out, why don't you?

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#### T.M.Haja Sahib

##### Guest
What I am telling you is most standard fuses in use in America would fail before that hour.

Take for example any one fuse rating you illustrated few posts back and work the time for the fuse to blow when 140% current passes through it.Say it is 20A common fuse.The 140% current is 28A.From its fuse curve,you may find time for the fuse to blow for that 28A.

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#### T.M.Haja Sahib

##### Guest
If it's obvious then just spit it out, why don't you?
It is misleading.you do not listen to me.:happysad:

#### Besoeker

##### Senior Member
You said you were here to help.
So be helpful and explain what you think is misleading about.

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#### T.M.Haja Sahib

##### Guest
explain what you think is misleading about.

Your 'demonstration' that a 3A common fuse would blow at 4.2A within one hour and so the 140% rule is false is misleading.

The test is actually carried out at about 140% of fuse rating.If the fuse curve shows it would below at 140% exactly,slightly reduce the percentage;fix it at 135%, for example, for all of the fuses in the batch under test.

Same is the case for 160% rule.

#### Besoeker

##### Senior Member
Your 'demonstration' that a 3A common fuse would blow at 4.2A within one hour and so the 140% rule is false is misleading.
The rule clearly is false for that fairly common fuse. The curve shows it would blow at 4A after 100 seconds.
I don't see anything whatsoever misleading about that. It is what it is.

So what now do you say about your comment:
Any one fuse curve negating the tests would do.
We've found one.

The test is actually carried out at about 140% of fuse rating.If the fuse curve shows it would below at 140% exactly,slightly reduce the percentage;fix it at 135%, .
I think that's called moving the goalposts.

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#### T.M.Haja Sahib

##### Guest
It is apparent that you are commenting without understanding

Bes:
I want to submit that, unfortunately,you too do not seem to grasp the purpose of test-1 on a fuse.Do you?

#### Besoeker

##### Senior Member
It is apparent that you are commenting without understanding
Really?
I simply pointed out that your 140% rule was violated by that fuse. On both counts.
What part of that have I misunderstood?

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#### Besoeker

##### Senior Member
You're right.
I don't understand why you would want to stick with a rule that has been clearly shown to be violated.
Actually, I did a bit more.
The curves go to 100 seconds, and, despite what you said, they most certainly have not leveled other than just about for the 1A fuse. I'll come back to that.
For all the others, they are continuing to reduce in value and no doubt would continue to do so beyond that 100 seconds.
So I projected them to 600 seconds - it was as far as I could on the page on which I printed the curves - still a long way short of your one hour.
As far as I could tell, every one would fail your 140% test with the possible exception of the 1A fuse. And even that is marginal. The scales are logarithmic and, when you take that into account, it's by no means certain that it would survive for an hour.

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#### T.M.Haja Sahib

##### Guest
You're right.
I don't understand why you would want to stick with a rule that has been clearly shown to be violated.
Actually, I did a bit more.
The curves go to 100 seconds, and, despite what you said, they most certainly have not leveled other than just about for the 1A fuse. I'll come back to that.
For all the others, they are continuing to reduce in value and no doubt would continue to do so beyond that 100 seconds.
So I projected them to 600 seconds - it was as far as I could on the page on which I printed the curves - still a long way short of your one hour.
As far as I could tell, every one would fail your 140% test with the possible exception of the 1A fuse. And even that is marginal. The scales are logarithmic and, when you take that into account, it's by no means certain that it would survive for an hour.

The fuse curves presented so far in the thread is up to 200 seconds only.If more time period were present,you could have made better decision.For this purpose,I provide a link for your eyes only.Take a look at page 147 and offer more comments.

http://www.fmccrustel.ru/pdf/BS88/BS88.pdf

#### Besoeker

##### Senior Member
The fuse curves presented so far in the thread is up to 200* seconds only.
My comments related to the curves kindly provided by iwire and your
And your
Any one fuse curve negating the tests would do.
We may have found several from that one sheet alone that negate the tests.

*Clearly, you missed post #71.
And, just for the record, I'm well aware of BS88 fuse characteristics. I have a copy of BS7671 on my desk both here at home and in my office at work.
Being British and an electrical engineer it would shameful if I did not.

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