RE: Bad Fuse vs. Good Fuse

[POWELL, DOUG]

Greetings all,
 
Excellent discussion.  I've had a number of responses ranging from "it really
doesn't matter" to the highly technical (it's truly amazing how complicated
fuses can be).  As I expected, everyone seems to be more or less on the same
page with this matter, and a few anecdotes were provided as well.  
 
 
thanks,
 
-doug
 
Douglas E. Powell 
Regulatory Compliance Engineer 
Advanced Energy Industries, Inc. 
Fort Collins, CO 80535 USA 

 

From: POWELL, DOUG [mailto:doug.pow...@aei.com]
Sent: Friday, May 23, 2003 4:57 PM
To: EMC-PSTC (E-mail)
Subject: Bad Fuse vs. Good Fuse


Hello all,
 
Recently, in my company, we've been discussing what exactly constitutes a good
or bad fuse.  In this industry we often hear that the trouble with a defective
product was, "the fuse was bad."  I occurred to me that the fuse is not bad,
it performed exactly intended.  In fact if the problem that caused the fuse to
"operate" is still present, then the fuse is still good even though it is now
an open circuit.  The only time it can be a bad fuse is if it did not operate,
resulting in shock or a fire.
 
I have now have my ears tuned-in to this concept of a "bad fuse" and find it
is commonly used all over the industry.  In fact you can go to any number of
websites that provide trouble shooting notes, and find instructions on how you
can measure a bad fuse from a good fuse using an Ohm meter, photos included. 
And some of these instructions are from reputable manufacturers.  Another term
often used is "defective fuse", which in some way sounds more scientific, but
is still fundamentally wrong.
 
I recently saw a newspaper article that gave the explaination why electrical
service was lost for over 100,000 people as a bad fuse.  An investigation was
under way to determine why the fuse went bad.  This is a little like hearing
the technologically uninitiated say "it must be a short somewhere", when the
television set stops working.
 
Maybe I am finicky, but this affects how companies view real product defects. 
When the "defect" is the bad fuse, then the real problem may be covered up. 
Often the answer is, increase the fuse size to prevent nuisance trips.  The
risk, of course, is that for every incremental increase in fuse value, you
increase the risk of fire proportionally.
 
Any thoughts or experiences?
 
BTW - To all US citizens in the group, have a relaxing Memorial Day weekend.
 
 
-doug
 
Douglas E. Powell 
Regulatory Compliance Engineer 
Advanced Energy Industries, Inc. 
Fort Collins, CO 80535 USA 

___
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that is confidential and proprietary information of Advanced 
Energy Industries, Inc.  The dissemination, distribution, use 
or copying of this message or any of its attachments is 
strictly prohibited without the express written consent of 
Advanced Energy Industries, Inc.

RE: Bad Fuse vs. Good Fuse

[drcuthb...@micron.com]

Doug,
 
I agree with you completely. I would not call a fuse that correctly performed
its job a "bad fuse". I would classify a fuse as either "intact" or "open".
And I would say "the failure caused the fuse to open".
 
On the subject of fuse sizing I have changed my philosophy over the years. In
the beginning I sized fuses to open when the current somewhat exceeded the
normal current. I favored slo-blow fuses. I later sized fuses to open only
under component failure conditions.I went to favoring fast-blow fuses.
Ultimately, or course, the object is to prevent smoke and fire. When done
correctly there is no nuisance opening. So when I build something, the fuses
are not conveniently located for the operator to change. 
 
As you know, specifying a fuse is like any other component- some engineering
is required to do it right. Determine the stresses the fuse will encounter
under all conditions and then match the fuse characteristics to the stresses. 
 
 Dave Cuthbert
 Micron Technology
 
 -Original Message-
From: POWELL, DOUG [mailto:doug.pow...@aei.com]
Sent: Friday, May 23, 2003 4:57 PM
To: EMC-PSTC (E-mail)
Subject: Bad Fuse vs. Good Fuse


Hello all,
 
Recently, in my company, we've been discussing what exactly constitutes a good
or bad fuse.  In this industry we often hear that the trouble with a defective
product was, "the fuse was bad."  I occurred to me that the fuse is not bad,
it performed exactly intended.  In fact if the problem that caused the fuse to
"operate" is still present, then the fuse is still good even though it is now
an open circuit.  The only time it can be a bad fuse is if it did not operate,
resulting in shock or a fire.
 
I have now have my ears tuned-in to this concept of a "bad fuse" and find it
is commonly used all over the industry.  In fact you can go to any number of
websites that provide trouble shooting notes, and find instructions on how you
can measure a bad fuse from a good fuse using an Ohm meter, photos included. 
And some of these instructions are from reputable manufacturers.  Another term
often used is "defective fuse", which in some way sounds more scientific, but
is still fundamentally wrong.
 
I recently saw a newspaper article that gave the explaination why electrical
service was lost for over 100,000 people as a bad fuse.  An investigation was
under way to determine why the fuse went bad.  This is a little like hearing
the technologically uninitiated say "it must be a short somewhere", when the
television set stops working.
 
Maybe I am finicky, but this affects how companies view real product defects. 
When the "defect" is the bad fuse, then the real problem may be covered up. 
Often the answer is, increase the fuse size to prevent nuisance trips.  The
risk, of course, is that for every incremental increase in fuse value, you
increase the risk of fire proportionally.
 
Any thoughts or experiences?
 
BTW - To all US citizens in the group, have a relaxing Memorial Day weekend.
 
 
-doug
 
Douglas E. Powell 
Regulatory Compliance Engineer 
Advanced Energy Industries, Inc. 
Fort Collins, CO 80535 USA 

___
This message, including any attachments, may contain information
that is confidential and proprietary information of Advanced 
Energy Industries, Inc.  The dissemination, distribution, use 
or copying of this message or any of its attachments is 
strictly prohibited without the express written consent of 
Advanced Energy Industries, Inc.

Re: Bad Fuse vs. Good Fuse

[Rich Nute]

Hi Dan:


Thank you for giving us straight answers and helping us
to overcome the "conventional wisdom" about fuses.

Several years ago, I put together an article addressing
fuses, their operation, and how to select the fuse rating.
See:

http://www.ewh.ieee.org/soc/emcs/pstc/psn/

Then, download file 90v03n3.pdf.

Clearly, this is out of date, but the principles I believe
are still valid.


Best regards,
Rich





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Re: Bad Fuse vs. Good Fuse

[Fred Townsend]

Dan I agree in general with your comments.  I will go so far as to stipulate
many design engineers don't know their hole from an ass in the ground as far
as properly specifying fuses. That being said the fuse industry has a problem. 

I have seen many, genuinely defective fuses.  I have seen even more genuinely
defective fuse holders that make the fuse appear defective.  Fuse holders that
were so hot they melted the fuse because they had several ohms of contact
resistance caused by the holder manufacture not properly cleaning them. 


I am happy to state that 99.5% of the problems I have seen were not with Buss
fuses. The vast majority of problems lie with your competitors that undersell
Buss.  Purchasing thinks a fuse is a fuse is a fuse and buys the cheaper fuse.
How about some guaranteed AQL levels that the engineers can specify to keep
the bad guys out of the purchasing office?  Is there an IEEE group for fuses? 
Maybe there should be. 


Fred Townsend 


"Giblin, Dan" wrote: 


  

As a fuse manufacturer, I have read all the e-mail on this subject with great
interest.  Unfortunately, many responses emphasize common misunderstandings. 


In the fuse industry, there is no such thing as a "Bad" fuse.  The chain of
e-mails clearly indicate why we avoid this word due to its various meanings. 
Similarly, we try to avoid the word 'failure'.  A "bad" or 'failed' fuse can
mean any number of things, but the most common is that the fuse is open, (it
operated).  Thus, the fuse did what it was supposed to do - operate - and yet
it is deemed 'bad' or a 'failure'. 


There are numerous occasions when a customer returns a 'bad' fuse.  The fuse
was 'bad' because it operated properly.  In many instances, the choice of fuse
type or amperage rating was flawed. 


For being such a 'simple' device, there are many items that influence the
correct choice.  I will address some of these by picking quotes out of the
various e-mail on the subject.  Among these are: 


*   Voltage rating - (This was addressed in Mr. Richmond's e-mail - I've 
heard
of a "bad" fuse, in this case, a fuse not adequate to protect the circuit and
user.  A 30 volt fuse can't be counted on to interrupt a 408 volt circuit. 
This is absolutely correct.  Choosing a voltage rating below your application
can be very dangerous.
*   Continuous Current rating  - This was addressed in Mr. Beckwith's 
e-mail -
Fuse operation when there is no fault can also sometimes be caused by
incorrect specification at the design stage, i.e. the fuse is rated too low
for the actual current consumed.  Very true.  One must look at surges
mentioned below and temperature.
*   Temporary Surges that you want the fuse to pass - A time delay fuse is
typically chosen for motor or transformer applications.  This is addressed a
little in Mr. Beckwith's e-mail - We have all seen cases where a fuse blows
when there is no apparent fault in the equipment, hence the maintainer's
comment "bad fuse". In my experience, this is usually caused by a temporary
overload condition or a power surge, not a "bad" fuse.
*   Temporary Surges that you do not want the fuse to pass.
*   Ambient temperature rating - This was addressed in Mr. Hughes e-mail 
below.
*   Interrupting Rating - This was addressed in Mr. Hughes e-mail - A 
couple of
other common design drop-offs I would like to mention include failure to
select a fuse with an adequate prospective fault current (i.e. selecting a
5x20 mm glass fuse - rated at Isc=35A max and using it in a mains circuit
where the prospective fault is in the order of 1kA) and 'forgetting' to
de-rate the fuse for use in a high ambient temperature (although this has
already be mentioned re. pico-fuses). 
*   Shock/Vibration - Most fuses do not claim to be suitable for such
applications.  From Mr. Schlentz - I have seen one instance where a fuse
opened during a vibration test.  I think that was a BAD FUSE.  I don't know if
the fuse in question was supposed to be suitable or not.

If chosen incorrectly, and 'nuisance' opening occurs, as Mr. Powell mentions -
Often the answer is, increase the fuse size to prevent nuisance trips.  The
risk, of course, is that for every incremental increase in fuse value, you
increase the risk of fire proportionally.  In doing this, you may be defeating
the purpose of having the protection there in the first place.  If a fuse
nuisance opens, it is likely that one of the above bulleted items was
overlooked. 


Additionally, as Mr. Richmond points out - Many fuses ARE mechanically
fragile; it's simple physics that says a low-current fuse will be a fragile
thread.  Think of them as light bulbs.  We do not call a light bulb unreliable
if it fails after being dropped on the floor; we call it broken.  This is
particularly true for low amperage fuses. 


As Mr. Beckwith points out - AIUI, there is a specified time it takes the fuse
to operate at 200% of the rated current, so for example a 1A normal blow fuse
requires 2A for 

RE: Bad Fuse vs. Good Fuse

[fdev...@assaabloyitg.com]

Dan,

So far there hasn't been mention of the mechanical stress aspect of fuse
failure related to the fuse wire breaking because of repeated cycling of
power.  I have personally seen this happen at a commercial daytime radio
station.  It took over a year for a properly rated fuse to blow because the
transmitter was turned on and off daily; the fuse wire was simply
mechanically flexed because of slight heating and finally went.  Yes, it
blew again about a year after it was replaced.  Maybe the transmitter
manufacturer should have specified a slow-blow fuse.

Frank de Vall
Manager Compliance Engineering
Assa Abloy ITG & HID Corporation



  

  "Giblin, Dan"   

  To:  
"'emc-p...@majordomo.ieee.org'"  
  Sent by:  
, "'POWELL, DOUG'"   
  owner-emc-pstc@majordo 

  mo.ieee.org   cc:   

                Subject:  RE: Bad Fuse vs.
Good Fuse   
  

  05/27/2003 02:17 PM 

  Please respond to   

  "Giblin, Dan"   

  

  







As a fuse manufacturer, I have read all the e-mail on this subject with
great interest.  Unfortunately, many responses emphasize common
misunderstandings.

In the fuse industry, there is no such thing as a "Bad" fuse.  The chain of
e-mails clearly indicate why we avoid this word due to its various
meanings.  Similarly, we try to avoid the word 'failure'.  A "bad" or
'failed' fuse can mean any number of things, but the most common is that
the fuse is open, (it operated).  Thus, the fuse did what it was supposed
to do - operate - and yet it is deemed 'bad' or a 'failure'.

There are numerous occasions when a customer returns a 'bad' fuse.  The
fuse was 'bad' because it operated properly.  In many instances, the choice
of fuse type or amperage rating was flawed.

For being such a 'simple' device, there are many items that influence the
correct choice.  I will address some of these by picking quotes out of the
various e-mail on the subject.  Among these are:

   Voltage rating - (This was addressed in Mr. Richmond's e-mail - I've
   heard of a "bad" fuse, in this case, a fuse not adequate to protect the
   circuit and user.  A 30 volt fuse can't be counted on to interrupt a 408
   volt circuit.  This is absolutely correct.  Choosing a voltage rating
   below your application can be very dangerous.

   Continuous Current rating  - This was addressed in Mr. Beckwith's e-mail
   - Fuse operation when there is no fault can also sometimes be caused by
   incorrect specification at the design stage, i.e. the fuse is rated too
   low for the actual current consumed.  Very true.  One must look at
   surges mentioned below and temperature.

   Temporary Surges that you want the fuse to pass - A time delay fuse is
   typically chosen for motor or transformer applications.  This is
   addressed a little in Mr. Beckwith's e-mail - We have all seen cases
   where a fuse blows when there is no apparent fault in the equipment,
   hence the maintainer's comment "bad fuse". In my experience, this is
   usually caused by a temporary overload condition or a power surge, not a
   "bad" fuse.

   Temporary Surges that you do not want the fuse to pass.

   Ambient temperature rating - This was addressed in Mr. Hughes e-mail
   below.

   Interrupting Rating - This was addressed in Mr. Hughes e-mail - A couple
   of other common design drop-offs I would like to mention include failure
   to select a fuse with an adequate prospective fault current (i.e.
   selecting a 5x20 mm glass fuse - rated at Isc=35A max and using it in a
   mains circuit where the prospective fault is in the order of 1kA) and
   'forgetting' to de-rate the fuse for use in a h

RE: Bad Fuse vs. Good Fuse

[Giblin, Dan]

As a fuse manufacturer, I have read all the e-mail on this subject with great
interest.  Unfortunately, many responses emphasize common misunderstandings.

In the fuse industry, there is no such thing as a "Bad" fuse.  The chain of
e-mails clearly indicate why we avoid this word due to its various meanings. 
Similarly, we try to avoid the word 'failure'.  A "bad" or 'failed' fuse can
mean any number of things, but the most common is that the fuse is open, (it
operated).  Thus, the fuse did what it was supposed to do - operate - and yet
it is deemed 'bad' or a 'failure'.

There are numerous occasions when a customer returns a 'bad' fuse.  The fuse
was 'bad' because it operated properly.  In many instances, the choice of fuse
type or amperage rating was flawed.

For being such a 'simple' device, there are many items that influence the
correct choice.  I will address some of these by picking quotes out of the
various e-mail on the subject.  Among these are:

*   Voltage rating - (This was addressed in Mr. Richmond's e-mail - I've 
heard
of a "bad" fuse, in this case, a fuse not adequate to protect the circuit and
user.  A 30 volt fuse can't be counted on to interrupt a 408 volt circuit. 
This is absolutely correct.  Choosing a voltage rating below your application
can be very dangerous. 

*   Continuous Current rating  - This was addressed in Mr. Beckwith's 
e-mail -
Fuse operation when there is no fault can also sometimes be caused by
incorrect specification at the design stage, i.e. the fuse is rated too low
for the actual current consumed.  Very true.  One must look at surges
mentioned below and temperature.

*   Temporary Surges that you want the fuse to pass - A time delay fuse is
typically chosen for motor or transformer applications.  This is addressed a
little in Mr. Beckwith's e-mail - We have all seen cases where a fuse blows
when there is no apparent fault in the equipment, hence the maintainer's
comment "bad fuse". In my experience, this is usually caused by a temporary
overload condition or a power surge, not a "bad" fuse.

*   Temporary Surges that you do not want the fuse to pass.

*   Ambient temperature rating - This was addressed in Mr. Hughes e-mail 
below. 

*   Interrupting Rating - This was addressed in Mr. Hughes e-mail - A 
couple of
other common design drop-offs I would like to mention include failure to
select a fuse with an adequate prospective fault current (i.e. selecting a
5x20 mm glass fuse - rated at Isc=35A max and using it in a mains circuit
where the prospective fault is in the order of 1kA) and 'forgetting' to
de-rate the fuse for use in a high ambient temperature (although this has
already be mentioned re. pico-fuses).  

*   Shock/Vibration - Most fuses do not claim to be suitable for such
applications.  From Mr. Schlentz - I have seen one instance where a fuse
opened during a vibration test.  I think that was a BAD FUSE.  I don't know if
the fuse in question was supposed to be suitable or not.

  

If chosen incorrectly, and 'nuisance' opening occurs, as Mr. Powell mentions -
Often the answer is, increase the fuse size to prevent nuisance trips.  The
risk, of course, is that for every incremental increase in fuse value, you
increase the risk of fire proportionally.  In doing this, you may be defeating
the purpose of having the protection there in the first place.  If a fuse
nuisance opens, it is likely that one of the above bulleted items was
overlooked.

Additionally, as Mr. Richmond points out - Many fuses ARE mechanically
fragile; it's simple physics that says a low-current fuse will be a fragile
thread.  Think of them as light bulbs.  We do not call a light bulb unreliable
if it fails after being dropped on the floor; we call it broken.  This is
particularly true for low amperage fuses. 

As Mr. Beckwith points out - AIUI, there is a specified time it takes the fuse
to operate at 200% of the rated current, so for example a 1A normal blow fuse
requires 2A for approximately 10 seconds to go open circuit.  This time
reduces exponentially as the current increases.  There are different opening
time requirements depending on the type of fuse, (Time Delay versus Fast
Acting), and its physical size.  The 135%, 200% and/or 500% opening times are
documented in the tri-national, harmonized 248 Series of fuse Standards,
(248.1 through 248.16 - The standards are UL, CSA, and ANCE).   

If anyone has any specific questions, or would like more information, send me
a separate e-mail and I'll see what I can do.

Dan 

Manager, Industry Standards & Certifications 
Cooper Bussmann 

RE: Bad Fuse vs. Good Fuse

[Stone, Richard]

seems this Fuse thing may need to be Dis-Fused..
99.99% of time their probably made correctly and thus
blow per their intended current..
its possible one was mfr'rd wrong/bad.
thus not working correctly..
which could be a problem for the user.
hope this stop before someone blows
his/her fuse...
only thing I have ever seen is the wrong fuse
used, that didnt blow..but the right fuse always did.
Richard,


From: don_borow...@selinc.com [mailto:don_borow...@selinc.com]
Sent: Tuesday, May 27, 2003 11:31 AM
To: EMC-PSTC (E-mail)
Subject: Re: Bad Fuse vs. Good Fuse








This seems to be a problem of semantics. In the case of a fuse, a "failure"
is a success - the fuse succeeded in protecting the circuit (neglecting the
cases where the fuse failed to do its job, discussed elsewhere).

I clearly recall some ads for Timken Steel in the 1960s which discussed the
successful "failure" of a mechanical "fuse", a device that would restrain
jets on the deck of an aircraft carrier until the engine thrust and
catapult force built up sufficiently for a safe launch, at which point the
device broke.

The problem is that in many cases when a metal part breaks, it is indeed a
failure. The same language gets carried across to cases where breakage is
the desired result, as in the case of the mechanical "fuse" where its
breaking is an indication things going well.

In the case of fuse operation, things are not going well. There is some
problem. The blown fuse is associated with a true failure. So perhaps there
is some guilt by association, even though the fuse is the (desired) victim
of the true failure.

I like the term "blown fuse". Though perhaps it is not as exact a
descrition as one would like, it is broadly understood, and is not
necessarily associated with failure or a "bad" fuse.

Don Borowski
Schweitzer Engineering Labs
Pullman, WA  USA

owner-emc-p...@majordomo.ieee.org wrote on 05/23/2003 03:56:53 PM:

> Hello all,
>
> Recently, in my company, we've been discussing what exactly
> constitutes a good or bad fuse.  In this industry we often hear that
> the trouble with a defective product was, "the fuse was bad."  I
> occurred to me that the fuse is not bad, it performed exactly
> intended.  In fact if the problem that caused the fuse to "operate"
> is still present, then the fuse is still good even though it is now
> an open circuit.  The only time it can be a bad fuse is if it did
> not operate, resulting in shock or a fire.
>
> I have now have my ears tuned-in to this concept of a "bad fuse" and
> find it is commonly used all over the industry.  In fact you can go
> to any number of websites that provide trouble shooting notes, and
> find instructions on how you can measure a bad fuse from a good fuse
> using an Ohm meter, photos included.  And some of these instructions
> are from reputable manufacturers.  Another term often used is
> "defective fuse", which in some way sounds more scientific, but is
> still fundamentally wrong.
>
> I recently saw a newspaper article that gave the explaination why
> electrical service was lost for over 100,000 people as a bad fuse.
> An investigation was under way to determine why the fuse went bad.
> This is a little like hearing the technologically uninitiated say
> "it must be a short somewhere", when the television set stops working.
>
> Maybe I am finicky, but this affects how companies view real product
> defects.  When the "defect" is the bad fuse, then the real problem
> may be covered up.  Often the answer is, increase the fuse size to
> prevent nuisance trips.  The risk, of course, is that for every
> incremental increase in fuse value, you increase the risk of fire
> proportionally.
>
> Any thoughts or experiences?
>
> BTW - To all US citizens in the group, have a relaxing Memorial Day
weekend.
>
>
> -doug
>
> Douglas E. Powell
> Regulatory Compliance Engineer
> Advanced Energy Industries, Inc.
> Fort Collins, CO 80535 USA



This message is from the IEEE EMC Society Product Safety
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Re: Bad Fuse vs. Good Fuse

[garymcintu...@aol.com]

(from Cambridge Advanced Learner's Dictionary
 )
bad (LOW QUALITY) adjective worse, worst
low quality; not acceptable:

Re: Bad Fuse vs. Good Fuse

[don_borow...@selinc.com]

This seems to be a problem of semantics. In the case of a fuse, a "failure"
is a success - the fuse succeeded in protecting the circuit (neglecting the
cases where the fuse failed to do its job, discussed elsewhere).

I clearly recall some ads for Timken Steel in the 1960s which discussed the
successful "failure" of a mechanical "fuse", a device that would restrain
jets on the deck of an aircraft carrier until the engine thrust and
catapult force built up sufficiently for a safe launch, at which point the
device broke.

The problem is that in many cases when a metal part breaks, it is indeed a
failure. The same language gets carried across to cases where breakage is
the desired result, as in the case of the mechanical "fuse" where its
breaking is an indication things going well.

In the case of fuse operation, things are not going well. There is some
problem. The blown fuse is associated with a true failure. So perhaps there
is some guilt by association, even though the fuse is the (desired) victim
of the true failure.

I like the term "blown fuse". Though perhaps it is not as exact a
descrition as one would like, it is broadly understood, and is not
necessarily associated with failure or a "bad" fuse.

Don Borowski
Schweitzer Engineering Labs
Pullman, WA  USA

owner-emc-p...@majordomo.ieee.org wrote on 05/23/2003 03:56:53 PM:

> Hello all,
>
> Recently, in my company, we've been discussing what exactly
> constitutes a good or bad fuse.  In this industry we often hear that
> the trouble with a defective product was, "the fuse was bad."  I
> occurred to me that the fuse is not bad, it performed exactly
> intended.  In fact if the problem that caused the fuse to "operate"
> is still present, then the fuse is still good even though it is now
> an open circuit.  The only time it can be a bad fuse is if it did
> not operate, resulting in shock or a fire.
>
> I have now have my ears tuned-in to this concept of a "bad fuse" and
> find it is commonly used all over the industry.  In fact you can go
> to any number of websites that provide trouble shooting notes, and
> find instructions on how you can measure a bad fuse from a good fuse
> using an Ohm meter, photos included.  And some of these instructions
> are from reputable manufacturers.  Another term often used is
> "defective fuse", which in some way sounds more scientific, but is
> still fundamentally wrong.
>
> I recently saw a newspaper article that gave the explaination why
> electrical service was lost for over 100,000 people as a bad fuse.
> An investigation was under way to determine why the fuse went bad.
> This is a little like hearing the technologically uninitiated say
> "it must be a short somewhere", when the television set stops working.
>
> Maybe I am finicky, but this affects how companies view real product
> defects.  When the "defect" is the bad fuse, then the real problem
> may be covered up.  Often the answer is, increase the fuse size to
> prevent nuisance trips.  The risk, of course, is that for every
> incremental increase in fuse value, you increase the risk of fire
> proportionally.
>
> Any thoughts or experiences?
>
> BTW - To all US citizens in the group, have a relaxing Memorial Day
weekend.
>
>
> -doug
>
> Douglas E. Powell
> Regulatory Compliance Engineer
> Advanced Energy Industries, Inc.
> Fort Collins, CO 80535 USA



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Re: Bad Fuse vs. Good Fuse

[John Woodgate]

I read in !emc-pstc that richhug...@aol.com wrote (in <095A00F3.5FF82361
.0ba45...@aol.com>) about 'Bad Fuse vs. Good Fuse' on Mon, 26 May 2003:
>It could
>be that the faulty components that John Woodgate mentioned fall into this
>category.

The epidemic failures were undoubtedly due to manufacturing defects, not
counterfeiting - unless the manufacturer was shipping the counterfeits
to us! We weren't buying from distributors.
-- 
Regards, John Woodgate, OOO - Own Opinions Only. http://www.jmwa.demon.co.uk 
Interested in professional sound reinforcement and distribution? Then go to 
http://www.isce.org.uk
PLEASE do NOT copy news posts to me by E-MAIL!


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re: Bad Fuse vs. Good Fuse

[richhug...@aol.com]

Doug,
 
Linguistically, how can an inanimate object such as a fuse be "good" or
"bad"?  Can it also be "angelic" or "evil"?  
 
I may be able to train a dog by telling it that it is a "good boy" when it
does what I want it to do (plus offer a suitable reward, of course) or
prevent it from not doing what I want by telling it that it is a "bad boy"
at the right moment.  However, as far as I know, it is not possible to
improve the reliability of a series of fuses by getting hold of each fuse
that has blown and telling it that it has been a "bad boy" - even if you
also tell all the fuses that haven't blown that they also "good boys".
Perhaps it is necessary to catch the fuse in the act of going "bad" (e.g.
blowing when its specification says it shouldn't?).
 
It seems to that others in this forum have many people have anecdotes
regarding incorrect collection of the fuse in the first case.  A couple of
other common design drop-offs I would like to mention include failure to
select a fuse with an adequate prospective fault current (i.e. selecting a
5x20 mm glass fuse - rated at Isc=35A max and using it in a mains circuit
where the prospective fault is in the order of 1kA) and 'forgetting' to
de-rate the fuse for use in a high ambient temperature (although this has
already be mentioned re. pico-fuses).  
 
Not in this forum, but I have been informed by other reliable sources that
it is possible to purchase counterfeited products that may look as though
they come from a reputable manufacturer, but in fact do not.  Certainly, the
UK has had to withdraw mains plugs that were inadequate and I have also
heard from reputable sources of high rupture capacity fuses that do not
contain and sand and where the fusing element is of the wrong type and
configuration of metal - meaning that they could explode if subjected to the
prospective fault current that such fuses are supposed to handle.  It could
be that the faulty components that John Woodgate mentioned fall into this
category.
 
So, we have fuses that do what they are intended to do and go open circuit
when an over-current is passed through them.  Such components are well
behaved; good fuse, good designer.
 
We have fuses that behave as their manufacturer said they would, but
unfortunately the designer selected the part incorrectly; good fuse, bad
designer.
 
We have fuses that do not behave as expected because they are not purchased
>from the expected manufacture; bad fuse, good designer, {naughty purchasing
dept?}
 
We have fuses that fail due to excessive vibration {but are the fuses
specified to operate under those conditions?}; possibly naughty fuse,
possibly naughty designer.
 
Oh dear, I've fallen into the trap of ascribing fuses with some kind of
will.  Oh well, at least I'm not alone...
 
Richard Hughes
 
Safety Answers Ltd.
 


From: ed.pr...@cubic.com [mailto:ed.pr...@cubic.com] 
Sent: Friday, May 23, 2003 11:42 PM
To: emc-p...@ieee.org
Subject: RE: Bad Fuse vs. Good Fuse




-Original Message----- 
From: POWELL, DOUG [mailto:doug.pow...@aei.com] 
Sent: Friday, May 23, 2003 3:57 PM 
To: EMC-PSTC (E-mail) 
Subject: Bad Fuse vs. Good Fuse 


Hello all, 

Recently, in my company, we've been discussing what exactly constitutes a
good or bad fuse.  In this industry we often hear that the trouble with a
defective product was, "the fuse was bad."  I occurred to me that the fuse
is not bad, it performed exactly intended.  In fact if the problem that
caused the fuse to "operate" is still present, then the fuse is still good
even though it is now an open circuit.  The only time it can be a bad fuse
is if it did not operate, resulting in shock or a fire.

I have now have my ears tuned-in to this concept of a "bad fuse" and find it
is commonly used all over the industry.  In fact you can go to any number of
websites that provide trouble shooting notes, and find instructions on how
you can measure a bad fuse from a good fuse using an Ohm meter, photos
included.  And some of these instructions are from reputable manufacturers.
Another term often used is "defective fuse", which in some way sounds more
scientific, but is still fundamentally wrong.

I recently saw a newspaper article that gave the explaination why electrical
service was lost for over 100,000 people as a bad fuse.  An investigation
was under way to determine why the fuse went bad.  This is a little like
hearing the technologically uninitiated say "it must be a short somewhere",
when the television set stops working.

Maybe I am finicky, but this affects how companies view real product
defects.  When the "defect" is the bad fuse, then the real problem may be
covered up.  Often the answer is, increase the fuse size to prevent nuisance
trips.  The risk, of course, is that for every incremental increase in fuse
va

re: Bad Fuse vs. Good Fuse

[richhug...@aol.com]

Doug,
 
Linguistically, how can an inanimate object such as a fuse be "good" or
"bad"?  Can it also be "angelic" or "evil"?  
 
I may be able to train a dog by telling it that it is a "good boy" when it
does what I want it to do (plus offer a suitable reward, of course) or
prevent it from not doing what I want by telling it that it is a "bad boy"
at the right moment.  However, as far as I know, it is not possible to
improve the reliability of a series of fuses by getting hold of each fuse
that has blown and telling it that it has been a "bad boy" - even if you
also tell all the fuses that haven't blown that they also "good boys".
Perhaps it is necessary to catch the fuse in the act of going "bad" (e.g.
blowing when its specification says it shouldn't?).
 
It seems to that others in this forum have many people have anecdotes
regarding incorrect collection of the fuse in the first case.  A couple of
other common design drop-offs I would like to mention include failure to
select a fuse with an adequate prospective fault current (i.e. selecting a
5x20 mm glass fuse - rated at Isc=35A max and using it in a mains circuit
where the prospective fault is in the order of 1kA) and 'forgetting' to
de-rate the fuse for use in a high ambient temperature (although this has
already be mentioned re. pico-fuses).  
 
Not in this forum, but I have been informed by other reliable sources that
it is possible to purchase counterfeited products that may look as though
they come from a reputable manufacturer, but in fact do not.  Certainly, the
UK has had to withdraw mains plugs that were inadequate and I have also
heard from reputable sources of high rupture capacity fuses that do not
contain and sand and where the fusing element is of the wrong type and
configuration of metal - meaning that they could explode if subjected to the
prospective fault current that such fuses are supposed to handle.  It could
be that the faulty components that John Woodgate mentioned fall into this
category.
 
So, we have fuses that do what they are intended to do and go open circuit
when an over-current is passed through them.  Such components are well
behaved; good fuse, good designer.
 
We have fuses that behave as their manufacturer said they would, but
unfortunately the designer selected the part incorrectly; good fuse, bad
designer.
 
We have fuses that do not behave as expected because they are not purchased
>from the expected manufacture; bad fuse, good designer, {naughty purchasing
dept?}
 
We have fuses that fail due to excessive vibration {but are the fuses
specified to operate under those conditions?}; possibly naughty fuse,
possibly naughty designer.
 
Oh dear, I've fallen into the trap of ascribing fuses with some kind of
will.  Oh well, at least I'm not alone...
 
Richard Hughes
 
Safety Answers Ltd.
 


From: ed.pr...@cubic.com [mailto:ed.pr...@cubic.com] 
Sent: Friday, May 23, 2003 11:42 PM
To: emc-p...@ieee.org
Subject: RE: Bad Fuse vs. Good Fuse




-Original Message----- 
From: POWELL, DOUG [mailto:doug.pow...@aei.com] 
Sent: Friday, May 23, 2003 3:57 PM 
To: EMC-PSTC (E-mail) 
Subject: Bad Fuse vs. Good Fuse 


Hello all, 

Recently, in my company, we've been discussing what exactly constitutes a
good or bad fuse.  In this industry we often hear that the trouble with a
defective product was, "the fuse was bad."  I occurred to me that the fuse
is not bad, it performed exactly intended.  In fact if the problem that
caused the fuse to "operate" is still present, then the fuse is still good
even though it is now an open circuit.  The only time it can be a bad fuse
is if it did not operate, resulting in shock or a fire.

I have now have my ears tuned-in to this concept of a "bad fuse" and find it
is commonly used all over the industry.  In fact you can go to any number of
websites that provide trouble shooting notes, and find instructions on how
you can measure a bad fuse from a good fuse using an Ohm meter, photos
included.  And some of these instructions are from reputable manufacturers.
Another term often used is "defective fuse", which in some way sounds more
scientific, but is still fundamentally wrong.

I recently saw a newspaper article that gave the explaination why electrical
service was lost for over 100,000 people as a bad fuse.  An investigation
was under way to determine why the fuse went bad.  This is a little like
hearing the technologically uninitiated say "it must be a short somewhere",
when the television set stops working.

Maybe I am finicky, but this affects how companies view real product
defects.  When the "defect" is the bad fuse, then the real problem may be
covered up.  Often the answer is, increase the fuse size to prevent nuisance
trips.  The risk, of course, is that for every incremental increase in fuse
va

Re: Bad Fuse vs. Good Fuse

[John Woodgate]

I read in !emc-pstc that douglas_beckw...@mitel.com wrote (in
)
about 'Bad Fuse vs. Good Fuse' on Mon, 26 May 2003:

>You can be almost certain that it was
>not caused by a "bad" fuse.

No, that is not true, or at least it wasn't when we were putting 20 x 5
mm fuses in television sets. Periodically, one or other of our five fuse
suppliers would run into manufacturing problems and we would get a batch
of fuses with a short-term failure rate of 20% or even more. They would
usually hold up long enough to pass soak and final test, and let go a
few days after purchase. 

The failure modes were open-circuit for no external reason and high
resistance. Occasionally, we would get one that produced cracking on
sound, indicating a poor internal connection.
-- 
Regards, John Woodgate, OOO - Own Opinions Only. http://www.jmwa.demon.co.uk 
Interested in professional sound reinforcement and distribution? Then go to 
http://www.isce.org.uk
PLEASE do NOT copy news posts to me by E-MAIL!


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 unsubscribe emc-pstc

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Re: Bad Fuse vs. Good Fuse

[douglas_beckw...@mitel.com]

Hi Doug,
In my days in reliability engineering, this discussion came up many times
when we were doing FMECA or fault tree analysis. Try posing the question
"what is the failure mode(s) of a fuse? " to a hardware designer. The
immediate answer you get is " When it goes open circuit". As you have
correctly noted in your posting, this is the wrong answer.

As we all know, a fuse is a protective device designed to go open circuit
under specified current conditions. A fuse fails when it doesn't go open
circuit under the specified current conditions. However the answer is not
is not as simple as it first looks. We have all seen cases where a fuse
blows when there is no apparent fault in the equipment, hence the
maintainer's comment "bad fuse". In my experience, this is usually caused
by a temporary overload condition or a power surge, not a "bad" fuse. Fuse
operation when there is no fault can also sometimes be caused by incorrect
specification at the design stage, i.e. the fuse is rated too low for the
actual current consumed. AIUI, there is a specified time it takes the fuse
to operate at 200% of the rated current, so for example a 1A normal blow
fuse requires 2A for approximately 10 seconds to go open circuit. This time
reduces exponentially as  the current increases. There are probably some
fuse manufacturers on this forum who can correct me on this. At 135% of the
rated current, a fuse will not operate almost indefinitely, though there is
some heating and it will eventually go open due to metal fatigue of the
wire.

Field failure reports of "bad fuse" are very misleading, because you really
do not know what caused the fault. You can be almost certain that it was
not caused by a "bad" fuse.

Regards

Doug

[Doug's of the world unite]





  
  
"POWELL, DOUG"
  
 To: "EMC-PSTC (E-mail)"

Sent by:  cc: 
              
owner-emc-pstc@majordom   Subject: Bad Fuse vs.
Good Fuse
o.ieee.org
  
  
  
  
  
05/23/03 06:56 PM 
  
Please respond to 
  
"POWELL, DOUG"
  
  
  
  
  





Hello  all,

Recently, in my  company, we've been discussing what exactly constitutes a
good or bad  fuse.  In this industry we often hear that the trouble with a
defective  product was, "the fuse was bad."  I occurred to me that the fuse
is not bad, it performed exactly intended.  In fact if the problem that
caused the fuse to "operate" is still present, then the fuse is still good
even  though it is now an open circuit.  The only time it can be a bad fuse
is if  it did not operate, resulting in shock or a fire.

I have now have my  ears tuned-in to this concept of a "bad fuse" and find
it is commonly used all  over the industry.  In fact you can go to any
number of websites that  provide trouble shooting notes, and find
instructions on how you can measure a  bad fuse from a good fuse using an
Ohm meter, photos included.  And some of  these instructions are from
reputable manufacturers.  Another term often  used is "defective fuse",
which in some way sounds more scientific, but is still  fundamentally
wrong.

I recently saw a  newspaper article that gave the explaination why
electrical service was lost for  over 100,000 people as a bad fuse.  An
investigation was under way to  determine why the fuse went bad.  This is a
little like hearing the  technologically uninitiated say "it must be a
short somewhere", when the  television set stops working.

Maybe I am finicky,  but this affects how companies view real product
defects.  When the  "

Re: Bad Fuse vs. Good Fuse

[Scott Lacey]

Doug,
The ony experience I ever had with "bad" fuses blowing prematurely 
was a soldered-in picofuse laying across a heavy copper trace on a 
PCB. This trace was retaining enough heat after soldering to 
weaken the fuse, causing premature failure in the field. Raising the 
body of the fuse off the board solved the problem.

Incidently, the problem was caught early through statistical analysis 
of field returns.

Scott Lacey

P.S.: It is well known in the automotive field that the old glass tube 
fuses often failed prematurely due to repeated stress and vibration. 
The newer blade type fuses are far more reliable.

On 23 May 2003 at 16:56, POWELL, DOUG wrote:

> 
> Hello all,
> 
> Recently, in my company, we've been discussing what exactly
> constitutes a good or bad fuse. In this industry we often hear that
> the trouble with a defective product was, "the fuse was bad." I
> occurred to me that the fuse is not bad, it performed exactly
> intended. In fact if the problem that caused the fuse to "operate" is
> still present, then the fuse is still good even though it is now an
> open circuit. The only time it can be a bad fuse is if it did not
> operate, resulting in shock or a fire.
> 
> I have now have my ears tuned-in to this concept of a "bad fuse" and
> find it is commonly used all over the industry. In fact you can go to
> any number of websites that provide trouble shooting notes, and find
> instructions on how you can measure a bad fuse from a good fuse using
> an Ohm meter, photos included. And some of these instructions are from
> reputable manufacturers. Another term often used is "defective fuse",
> which in some way sounds more scientific, but is still fundamentally
> wrong.
> 
> I recently saw a newspaper article that gave the explaination why
> electrical service was lost for over 100,000 people as a bad fuse. An
> investigation was under way to determine why the fuse went bad. This
> is a little like hearing the technologically uninitiated say "it must
> be a short somewhere", when the television set stops working.
> 
> Maybe I am finicky, but this affects how companies view real product
> defects. When the "defect" is the bad fuse, then the real problem may
> be covered up. Often the answer is, increase the fuse size to prevent
> nuisance trips. The risk, of course, is that for every incremental
> increase in fuse value, you increase the risk of fire proportionally.
> 
> Any thoughts or experiences?
> 
> BTW - To all US citizens in the group, have a relaxing Memorial Day
> weekend.
> 
> 
> -doug
> 
> Douglas E. Powell 
> Regulatory Compliance Engineer 
> Advanced Energy Industries, Inc. 
> Fort Collins, CO 80535 USA 
> 
> ___
> This message, including any attachments, may contain information
> that is confidential and proprietary information of Advanced 
> Energy Industries, Inc. The dissemination, distribution, use 
> or copying of this message or any of its attachments is 
> strictly prohibited without the express written consent of 
> Advanced Energy Industries, Inc.





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Re: Bad Fuse vs. Good Fuse

[bob]

I have seen one instance where a fuse opened during a vibration test. I 
think that was a BAD FUSE.

Best Regards

Bob Schlentz






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RE: Bad Fuse vs. Good Fuse

[Charles Grasso]

Seems to me - a bad fuse is open. Simple as that.


From: owner-emc-p...@majordomo.ieee.org
[mailto:owner-emc-p...@majordomo.ieee.org]On Behalf Of POWELL, DOUG
Sent: Friday, May 23, 2003 4:57 PM
To: EMC-PSTC (E-mail)
Subject: Bad Fuse vs. Good Fuse


Hello all,
 
Recently, in my company, we've been discussing what exactly constitutes a good
or bad fuse.  In this industry we often hear that the trouble with a defective
product was, "the fuse was bad."  I occurred to me that the fuse is not bad,
it performed exactly intended.  In fact if the problem that caused the fuse to
"operate" is still present, then the fuse is still good even though it is now
an open circuit.  The only time it can be a bad fuse is if it did not operate,
resulting in shock or a fire.
 
I have now have my ears tuned-in to this concept of a "bad fuse" and find it
is commonly used all over the industry.  In fact you can go to any number of
websites that provide trouble shooting notes, and find instructions on how you
can measure a bad fuse from a good fuse using an Ohm meter, photos included. 
And some of these instructions are from reputable manufacturers.  Another term
often used is "defective fuse", which in some way sounds more scientific, but
is still fundamentally wrong.
 
I recently saw a newspaper article that gave the explaination why electrical
service was lost for over 100,000 people as a bad fuse.  An investigation was
under way to determine why the fuse went bad.  This is a little like hearing
the technologically uninitiated say "it must be a short somewhere", when the
television set stops working.
 
Maybe I am finicky, but this affects how companies view real product defects. 
When the "defect" is the bad fuse, then the real problem may be covered up. 
Often the answer is, increase the fuse size to prevent nuisance trips.  The
risk, of course, is that for every incremental increase in fuse value, you
increase the risk of fire proportionally.
 
Any thoughts or experiences?
 
BTW - To all US citizens in the group, have a relaxing Memorial Day weekend.
 
 
-doug
 
Douglas E. Powell 
Regulatory Compliance Engineer 
Advanced Energy Industries, Inc. 
Fort Collins, CO 80535 USA 

___
This message, including any attachments, may contain information
that is confidential and proprietary information of Advanced 
Energy Industries, Inc.  The dissemination, distribution, use 
or copying of this message or any of its attachments is 
strictly prohibited without the express written consent of 
Advanced Energy Industries, Inc.

Re: Bad Fuse vs. Good Fuse

[Cortland Richmond]

I believe the term "bad," as applied to a fuse which has functioned as
intended, is a report of its (no pun intended) current condition, rather
than its suitability for the purpose.  A better word, I think, and still
accessible to laymen, is "blown."

>> On the other side fuses and fuse holders were probably the least
reliable components we had with defect rates of 4 to 80%. <<

Reliability rightfully includes surviving shock and vibration; a complete
specification for an application would include what stresses a component
(not just fuses) must endure before, during and after installation. Many
fuses ARE mechanically fragile; it's simple physics that says a low-current
fuse will be a fragile thread. Think of them as light bulbs. We do not call
a light bulb unreliable if it fails after being dropped on the floor; we
call it broken. Perhaps we should specify our fuses to last long enough to
be installed? 

I've heard of a "bad" fuse, in this case, a fuse not adequate to protect
the circuit and user.  A 30 volt fuse can't be counted on to interrupt a
408 volt circuit. There were frightful physical consequences (which I did
not see, thank God) and also legal ones, the echoes of which I did get to
hear.  But here, the fuse itself was not malfunctioning, either, only badly
specified. 

>>  I forbad my testers from using the term "bad" or its military
equivalent "NFG" on their failure tags <<

I ran into this myself, some years ago, as an Army avionics tech. Since we
were forbidden to write "INOP," we had to describe what symptoms were
observed. Having worked both line and bench I understood why, too. But
perhaps "Modulator transistors get hot enough to boil spit" was more than
they wanted to know.



Cortland


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Re: Bad Fuse vs. Good Fuse

[Fred Townsend]

Doug when I ran my own section of a factory I forbad my testers from using the
term "bad" or its military equivalent "NFG" on their failure tags although we
saw the term many times on field returns.  Bad isn't descriptive. Instead they
were instructed to simply describe why they thought the unit was defective. 
This sounds complicated at first, but we quickly worked out some simple codes.
i.e. ma=0 meant the unit didn't draw any current.  If ma=0 then it was quite
possible the fuse was open but the fuse was not the defect, rather a pointer
to a latent defect. 

On the other side fuses and fuse holders were probably the least reliable
components we had with defect rates of 4 to 80%.  Sometimes it was very
confusing. A fuse that had opened because the current exceeded rating was not
defective but merely a formally functional open fuse.  Then again a fuse that
was open before any current was passed was definitely a defective fuse.  125
or 180 ma fuses could be made defective merely by dropping them.  We had some
signaling fuses that would blow on over current but fail to signal.  These
were defective blown fuses. 


I fear I may have added to the "fog" but at least I never used the term "bad". 


Fred Townsend 
  
  
  


"POWELL, DOUG" wrote: 


 Hello all,Recently, in my company, we've been discussing what exactly
constitutes a good or bad fuse.  In this industry we often hear that the
trouble with a defective product was, "the fuse was bad." I occurred to me
that the fuse is not bad, it performed exactly intended.  In fact if the
problem that caused the fuse to "operate" is still present, then the fuse is
still good even though it is now an open circuit.  The only time it can be a
bad fuse is if it did not operate, resulting in shock or a fire.I have now
have my ears tuned-in to this concept of a "bad fuse" and find it is commonly
used all over the industry.  In fact you can go to any number of websites that
provide trouble shooting notes, and find instructions on how you can measure a
bad fuse from a good fuse using an Ohm meter, photos included.  And some of
these instructions are from reputable manufacturers.  Another term often used
is "defective fuse", which in some way sounds more scientific, but is still
fundamentally wrong.I recently saw a newspaper article that gave the
explaination why electrical service was lost for over 100,000 people as a bad
fuse.  An investigation was under way to determine why the fuse went bad. 
This is a little like hearing the technologically uninitiated say "it must be
a short somewhere", when the television set stops working.Maybe I am finicky,
but this affects how companies view real product defects.  When the "defect"
is the bad fuse, then the real problem may be covered up.  Often the answer
is, increase the fuse size to prevent nuisance trips.  The risk, of course, is
that for every incremental increase in fuse value, you increase the risk of
fire proportionally.Any thoughts or experiences?BTW - To all US citizens in
the group, have a relaxing Memorial Day weekend.-doug 

Douglas E. Powell 
Regulatory Compliance Engineer 
Advanced Energy Industries, Inc. 
Fort Collins, CO 80535 USA 
___ 
This message, including any attachments, may contain information 
that is confidential and proprietary information of Advanced 
Energy Industries, Inc.  The dissemination, distribution, use 
or copying of this message or any of its attachments is 
strictly prohibited without the express written consent of 
Advanced Energy Industries, Inc.

Re: Bad Fuse vs. Good Fuse

[John Woodgate]

I read in !emc-pstc that POWELL, DOUG  wrote (in
) about 'Bad
Fuse vs. Good Fuse' on Fri, 23 May 2003:

>Recently, in my company, we've been discussing what exactly constitutes a 
>good or bad fuse.  In this industry we often hear that the trouble with
a 
>defective product was, "the fuse was bad."  I occurred to me that the
fuse 
>is not bad, it performed exactly intended.  In fact if the problem that 
>caused the fuse to "operate" is still present, then the fuse is still
good 
>even though it is now an open circuit.  The only time it can be a bad
fuse 
>is if it did not operate, resulting in shock or a fire.

There are two cases where a fuse really is 'bad':

 - it goes open-circuit in spite of its fusing current/time not having
been exceeded;

 - its resistance changes from milliohms to ohms, perhaps varying.

I agree that a fuse that has failed when it should have is not 'bad',
but it's notoriously difficult to stop people using bad terminology.
-- 
Regards, John Woodgate, OOO - Own Opinions Only. http://www.jmwa.demon.co.uk 
Interested in professional sound reinforcement and distribution? Then go to 
http://www.isce.org.uk
PLEASE do NOT copy news posts to me by E-MAIL!


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Re: Bad Fuse vs. Good Fuse

[Boris Yost]

Dear Team:

I vaguely recall some fuse spec for some flavor of the little tubular
glass fuses, that said that an for N amp fuse, 50% of a population run at
exactly N amps at 25C into a resistive load would blow in 4 hours.  And the
current rating goes up/down as a function of temperature.

And probably age.   And when they used to use them in cars, they would
occasionally 'go bad' due to vibration and temperature cycling.

And we just had one 'go bad' due to the fact that the fuse holder contact
wasn't well made so it got hot.

A fuse is a cheap electronic component.  Like resistors and capacitors,
most they are reliable when they are made.  In application they have wear-out
mechanisms and accelerated failure conditions.  But they're a whole lot better
than doing nothing.

Boris

 


-Original Message- 
From: POWELL, DOUG [ mailto:doug.pow...@aei.com] 
Sent: Friday, May 23, 2003 3:57 PM 
To: EMC-PSTC (E-mail) 
Subject: Bad Fuse vs. Good Fuse 


Hello all, 

Recently, in my company, we've been discussing what exactly constitutes a good
or bad fuse.  In this industry we often hear that the trouble with a defective
product was, "the fuse was bad."  I occurred to me that the fuse is not bad,
it performed exactly intended.  In fact if the problem that caused the fuse to
"operate" is still present, then the fuse is still good even though it is now
an open circuit.  The only time it can be a bad fuse is if it did not operate,
resulting in shock or a fire.

I have now have my ears tuned-in to this concept of a "bad fuse" and find it
is commonly used all over the industry.  In fact you can go to any number of
websites that provide trouble shooting notes, and find instructions on how you
can measure a bad fuse from a good fuse using an Ohm meter, photos included. 
And some of these instructions are from reputable manufacturers.  Another term
often used is "defective fuse", which in some way sounds more scientific, but
is still fundamentally wrong.

I recently saw a newspaper article that gave the explaination why electrical
service was lost for over 100,000 people as a bad fuse.  An investigation was
under way to determine why the fuse went bad.  This is a little like hearing
the technologically uninitiated say "it must be a short somewhere", when the
television set stops working.

Maybe I am finicky, but this affects how companies view real product defects. 
When the "defect" is the bad fuse, then the real problem may be covered up. 
Often the answer is, increase the fuse size to prevent nuisance trips.  The
risk, of course, is that for every incremental increase in fuse value, you
increase the risk of fire proportionally.

Any thoughts or experiences? 

BTW - To all US citizens in the group, have a relaxing Memorial Day weekend. 


-doug 

Douglas E. Powell 
Regulatory Compliance Engineer 
Advanced Energy Industries, Inc. 
Fort Collins, CO 80535 USA  


Doug: 

I would submit that a fuse can be "bad" if it opens at too low of a current,
thus creating an improper denial of service.

A fuse may also be "bad" if it does not follow the expected curve of energy
operation for both conductive and interrupted states. An "open" fuse may be
considered a successful application of protection, but, suppose it was a
one-amp rated fuse, was subjected to a 20-amp fault current, yet required 30
seconds to melt and create the interrupted condition. I suspect that most
engineers would expect a one-amp fuse to blow much faster than that.

As usual, it's always more complicated the closer you look at it. 

Regards, 

Ed Price 
ed.pr...@cubic.com 
NARTE Certified EMC Engineer & Technician 
Electromagnetic Compatibility Lab 
Cubic Defense Systems 
San Diego, CA  USA 
858-505-2780  (Voice) 
858-505-1583  (Fax) 
Military & Avionics EMC Is Our Specialty  

RE: Bad Fuse vs. Good Fuse

[Price, Ed]

-Original Message- 
From: POWELL, DOUG [ mailto:doug.pow...@aei.com] 
Sent: Friday, May 23, 2003 3:57 PM 
To: EMC-PSTC (E-mail) 
Subject: Bad Fuse vs. Good Fuse 


Hello all, 

Recently, in my company, we've been discussing what exactly constitutes a good
or bad fuse.  In this industry we often hear that the trouble with a defective
product was, "the fuse was bad."  I occurred to me that the fuse is not bad,
it performed exactly intended.  In fact if the problem that caused the fuse to
"operate" is still present, then the fuse is still good even though it is now
an open circuit.  The only time it can be a bad fuse is if it did not operate,
resulting in shock or a fire.

I have now have my ears tuned-in to this concept of a "bad fuse" and find it
is commonly used all over the industry.  In fact you can go to any number of
websites that provide trouble shooting notes, and find instructions on how you
can measure a bad fuse from a good fuse using an Ohm meter, photos included. 
And some of these instructions are from reputable manufacturers.  Another term
often used is "defective fuse", which in some way sounds more scientific, but
is still fundamentally wrong.

I recently saw a newspaper article that gave the explaination why electrical
service was lost for over 100,000 people as a bad fuse.  An investigation was
under way to determine why the fuse went bad.  This is a little like hearing
the technologically uninitiated say "it must be a short somewhere", when the
television set stops working.

Maybe I am finicky, but this affects how companies view real product defects. 
When the "defect" is the bad fuse, then the real problem may be covered up. 
Often the answer is, increase the fuse size to prevent nuisance trips.  The
risk, of course, is that for every incremental increase in fuse value, you
increase the risk of fire proportionally.

Any thoughts or experiences? 

BTW - To all US citizens in the group, have a relaxing Memorial Day weekend. 


-doug 

Douglas E. Powell 
Regulatory Compliance Engineer 
Advanced Energy Industries, Inc. 
Fort Collins, CO 80535 USA  


Doug: 

I would submit that a fuse can be "bad" if it opens at too low of a current,
thus creating an improper denial of service.

A fuse may also be "bad" if it does not follow the expected curve of energy
operation for both conductive and interrupted states. An "open" fuse may be
considered a successful application of protection, but, suppose it was a
one-amp rated fuse, was subjected to a 20-amp fault current, yet required 30
seconds to melt and create the interrupted condition. I suspect that most
engineers would expect a one-amp fuse to blow much faster than that.

As usual, it's always more complicated the closer you look at it. 

Regards, 

Ed Price 
ed.pr...@cubic.com 
NARTE Certified EMC Engineer & Technician 
Electromagnetic Compatibility Lab 
Cubic Defense Systems 
San Diego, CA  USA 
858-505-2780  (Voice) 
858-505-1583  (Fax) 
Military & Avionics EMC Is Our Specialty  

Bad Fuse vs. Good Fuse

[POWELL, DOUG]

Hello all,
 
Recently, in my company, we've been discussing what exactly constitutes a good
or bad fuse.  In this industry we often hear that the trouble with a defective
product was, "the fuse was bad."  I occurred to me that the fuse is not bad,
it performed exactly intended.  In fact if the problem that caused the fuse to
"operate" is still present, then the fuse is still good even though it is now
an open circuit.  The only time it can be a bad fuse is if it did not operate,
resulting in shock or a fire.
 
I have now have my ears tuned-in to this concept of a "bad fuse" and find it
is commonly used all over the industry.  In fact you can go to any number of
websites that provide trouble shooting notes, and find instructions on how you
can measure a bad fuse from a good fuse using an Ohm meter, photos included. 
And some of these instructions are from reputable manufacturers.  Another term
often used is "defective fuse", which in some way sounds more scientific, but
is still fundamentally wrong.
 
I recently saw a newspaper article that gave the explaination why electrical
service was lost for over 100,000 people as a bad fuse.  An investigation was
under way to determine why the fuse went bad.  This is a little like hearing
the technologically uninitiated say "it must be a short somewhere", when the
television set stops working.
 
Maybe I am finicky, but this affects how companies view real product defects. 
When the "defect" is the bad fuse, then the real problem may be covered up. 
Often the answer is, increase the fuse size to prevent nuisance trips.  The
risk, of course, is that for every incremental increase in fuse value, you
increase the risk of fire proportionally.
 
Any thoughts or experiences?
 
BTW - To all US citizens in the group, have a relaxing Memorial Day weekend.
 
 
-doug
 
Douglas E. Powell 
Regulatory Compliance Engineer 
Advanced Energy Industries, Inc. 
Fort Collins, CO 80535 USA 

___
This message, including any attachments, may contain information
that is confidential and proprietary information of Advanced 
Energy Industries, Inc.  The dissemination, distribution, use 
or copying of this message or any of its attachments is 
strictly prohibited without the express written consent of 
Advanced Energy Industries, Inc.