Fuse: fast blown vs slow blown
Man-wai Chang
How dangerous is it to replace a 500mA fast-brown fuse with a 500mA
slow-brown one?
--
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Phil Allison
"Man-wai Chang"
>
> How dangerous is it to replace a 500mA fast-brown fuse with a 500mA
> slow-brown one?
** Confucius once say:
" The quick brown fox jumps over the lazy dog "
Think about it ...........
.... Phil
Globemaker
The danger, on a scale from 1 to 10 is 8. Some equipment can be
damaged in a millisecond, so a slow-blown fuse can result in a ruined
piece of equipment. For example, an integrated circuit could need 12
volts, but you plug in the wrong wall wart that has no labels on it.
It has 18 volts instead of 12 volts, but it uses the same diameter
coaxial connector. A fast fuse protects in 400 microseconds, but the
slow blow does not blow that fast so the 45 nanometer digital device
gets melted in 1000 microseconds.
Phil Allison
"Globemaker"
The danger, on a scale from 1 to 10 is 8. Some equipment can be
damaged in a millisecond, so a slow-blown fuse can result in a ruined
piece of equipment. For example, an integrated circuit could need 12
volts, but you plug in the wrong wall wart that has no labels on it.
It has 18 volts instead of 12 volts, but it uses the same diameter
coaxial connector. A fast fuse protects in 400 microseconds, but the
slow blow does not blow that fast so the 45 nanometer digital device
gets melted in 1000 microseconds.
** Globemaker is one of those personages who sincerely believes that " Star
Trek " is a documentary.
And he has pointy ears too.
Beam me up Scotty ........
... Phil
Tim Wescott
>
> How dangerous is it to replace a 500mA fast-brown fuse with a 500mA
> slow-brown one?
It depends entirely on the equipment. Slow-blow fuses used to be more
expensive than fast-blow fuses, and tend to be less available. So a
designer's knee-jerk reaction may be to specify a fast-blow fuse
'because it's there'.
So there's a good chance that you can drop your slow-blow fuse in there
and everything will be fine, but if you do and burn something up, don't
come crying to me. I would hesitate to do so myself unless I knew what
was in the product, and felt that a slow-blow would work OK. I would
also hesitate to replace the fuse unless I knew why the original had
blown -- fuses blow for reasons, and if the equipment is dorked and
blowing fuses, then putting in more fuses will just make it more dorked.
Your best bet is to get the right fuse, and at least try to fix the
fault before you turn the equipment on with your shiny new fuse.
--
Tim Wescott
Wescott Design Services
http://www.wescottdesign.com
Do you need to implement control loops in software?
"Applied Control Theory for Embedded Systems" was written for you.
See details at http://www.wescottdesign.com/actfes/actfes.html
Man-wai Chang
> fault before you turn the equipment on with your shiny new fuse.
For a multimeter, is it always better to use a fast blow fuse?
--
@~@ Might, Courage, Vision, SINCERITY.
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Man-wai Chang
> coaxial connector. A fast fuse protects in 400 microseconds, but the
> slow blow does not blow that fast so the 45 nanometer digital device
> gets melted in 1000 microseconds.
Is the 13A BS1362 fuse a fast blow one?
--
@~@ Might, Courage, Vision, SINCERITY.
/ v \ Simplicity is Beauty! May the Force and farces be with you!
/( _ )\ (x86_64 Ubuntu 9.10) Linux 2.6.39
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Tim Wescott
>> Your best bet is to get the right fuse, and at least try to fix the
>> fault before you turn the equipment on with your shiny new fuse.
>
> For a multimeter, is it always better to use a fast blow fuse?
It depends on the multimeter. I'd stick with the fast blow fuse and
stop putting it in 'voltage' mode when you've got it connected to
measure current.
Tim Wescott
>> fault before you turn the equipment on with your shiny new fuse.
>
> For a multimeter, is it always better to use a fast blow fuse?
>
-- if it is, then you don't just need the right current rating, you need
a matched fuse.
Man-wai Chang
> putting it in 'voltage' mode when you've got it connected to measure
> current.
It's a glass one, 500mA fast blow according to the manual.
--
@~@ Might, Courage, Vision, SINCERITY.
/ v \ Simplicity is Beauty! May the Force and farces be with you!
/( _ )\ (x86_64 Ubuntu 9.10) Linux 2.6.39
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Jeff Liebermann
wrote:
>On 05/31/2011 08:57 AM, Man-wai Chang wrote:
>>> Your best bet is to get the right fuse, and at least try to fix the
>>> fault before you turn the equipment on with your shiny new fuse.
>>
>> For a multimeter, is it always better to use a fast blow fuse?
>Check to make sure that the fuse isn't being used as the current shunt
>-- if it is, then you don't just need the right current rating, you need
>a matched fuse.
Chuckle. If a fuse were used as a current shunt, then when the fuse
blows, instead of a few millivolts across the fuse, the meter now gets
the full voltage of whatever is being measured. The fuse holder
contact resistance will probably be larger than the wire resistance in
the fuse (fast blow). I don't think anyone uses a fuse as a current
shunt.
--
Jeff Liebermann je...@cruzio.com
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558
Jeff Liebermann
<toylet...@gmail.com> wrote:
>> It has 18 volts instead of 12 volts, but it uses the same diameter
>> coaxial connector. A fast fuse protects in 400 microseconds, but the
>> slow blow does not blow that fast so the 45 nanometer digital device
>> gets melted in 1000 microseconds.
>
>Is the 13A BS1362 fuse a fast blow one?
That's the number of the plug, not the fuse:
<http://en.wikipedia.org/wiki/BS_1363>
It does have a fuse inside, but I don't know the value or type.
Winston
> On 05/31/2011 08:57 AM, Man-wai Chang wrote:
>>> Your best bet is to get the right fuse, and at least try to fix the
>>> fault before you turn the equipment on with your shiny new fuse.
>>
>> For a multimeter, is it always better to use a fast blow fuse?
>
> It depends on the multimeter. I'd stick with the fast blow fuse and stop
> putting it in 'voltage' mode when you've got it connected to measure
> current.
That's 'current' mode when you've got it connected to measure
voltage, yes?
--Winston
Tim Wescott
Uhhh...
D'oh!
Jamie
>> Your best bet is to get the right fuse, and at least try to fix the
>> fault before you turn the equipment on with your shiny new fuse.
>
>
> For a multimeter, is it always better to use a fast blow fuse?
>
yes
Jamie
> On Tue, 31 May 2011 09:02:08 -0700, Tim Wescott <t...@seemywebsite.com>
> wrote:
>
>
>>On 05/31/2011 08:57 AM, Man-wai Chang wrote:
>>
>>>>Your best bet is to get the right fuse, and at least try to fix the
>>>>fault before you turn the equipment on with your shiny new fuse.
>>>
>>>For a multimeter, is it always better to use a fast blow fuse?
>
>
>>Check to make sure that the fuse isn't being used as the current shunt
>>-- if it is, then you don't just need the right current rating, you need
>>a matched fuse.
>
>
> Chuckle. If a fuse were used as a current shunt, then when the fuse
> blows, instead of a few millivolts across the fuse, the meter now gets
> the full voltage of whatever is being measured. The fuse holder
> contact resistance will probably be larger than the wire resistance in
> the fuse (fast blow). I don't think anyone uses a fuse as a current
> shunt.
>
Hush, you wasn't suppose to notice that! Built in obsolescence.
Jamie
Michael A. Terrell
Jeff Liebermann wrote:
>
> On Tue, 31 May 2011 09:02:08 -0700, Tim Wescott <t...@seemywebsite.com>
> wrote:
>
> >On 05/31/2011 08:57 AM, Man-wai Chang wrote:
> >>> Your best bet is to get the right fuse, and at least try to fix the
> >>> fault before you turn the equipment on with your shiny new fuse.
> >>
> >> For a multimeter, is it always better to use a fast blow fuse?
>
> >Check to make sure that the fuse isn't being used as the current shunt
> >-- if it is, then you don't just need the right current rating, you need
> >a matched fuse.
>
> Chuckle. If a fuse were used as a current shunt, then when the fuse
> blows, instead of a few millivolts across the fuse, the meter now gets
> the full voltage of whatever is being measured. The fuse holder
> contact resistance will probably be larger than the wire resistance in
> the fuse (fast blow). I don't think anyone uses a fuse as a current
> shunt.
Too hard to calibrate. :)
I used some test fixtures on the PRC-77 QA line for module
interchangability that had to be returned to the cal lab if a module
blew a fuse. !@#$%^&*( RCA/NATO design. @#$%^&*
--
It's easy to think outside the box, when you have a cutting torch.
John Robertson
>
> How dangerous is it to replace a 500mA fast-brown fuse with a 500mA
> slow-brown one?
>
Hope this helps answer your question!
http://flippers.com/fuses.html
John :-#)#
--
(Please post followups or tech enquiries to the newsgroup)
John's Jukes Ltd. 2343 Main St., Vancouver, BC, Canada V5T 3C9
Call (604)872-5757 or Fax 872-2010 (Pinballs, Jukes, Video Games)
www.flippers.com
"Old pinballers never die, they just flip out."
Baron
>> It has 18 volts instead of 12 volts, but it uses the same diameter
>> coaxial connector. A fast fuse protects in 400 microseconds, but the
>> slow blow does not blow that fast so the 45 nanometer digital device
>> gets melted in 1000 microseconds.
>
> Is the 13A BS1362 fuse a fast blow one?
No !
--
Best Regards:
Baron.
Phil Allison
"Jeff Liebermann"
>>
>>Is the 13A BS1362 fuse a fast blow one?
>
> That's the number of the plug, not the fuse:
** Funny, I have any number of fuses in my bins with "BS 1362" printed on
them.
> <http://en.wikipedia.org/wiki/BS_1363>
>
> It does have a fuse inside, but I don't know the value or type.
**From the very same Wiki:
http://en.wikipedia.org/wiki/BS_1363#Fuses
A 13A, BS 1362 fuse is very much a Slow Blow !
.... Phil
Winston
> On 05/31/2011 10:16 AM, Winston wrote:
(...)
>> That's 'current' mode when you've got it connected to measure
>> voltage, yes?
>
> Uhhh...
>
>
>
> D'oh!
The fuse for my Fluke 79 multimeter retails for $10.00.
(Ten U.S. Dollars)
http://www.flukeonlinestore.com/3478682.html
Guess what prompted that discovery.
Go ahead. Guess. :)
--Winston <-- It's better, now.
Phil Allison
"Winston"
> The fuse for my Fluke 79 multimeter retails for $10.00.
> (Ten U.S. Dollars)
>
> http://www.flukeonlinestore.com/3478682.html
>
> Guess what prompted that discovery.
>
> Go ahead. Guess. :)
** That fuse is designed to protect the multi-meter, its leads ( and you )
from a worst case scenario.
That scenario is when you probe a 415 volt, 3 phase power outlet with the
meter accidentally set to the 10 amp range.
A standard glass fuse would simply arc from end to end, the probes and leads
would explode and cover you in hot metal and the meter would become a write
off.
The specified ( fast acting, high rupture current, high voltage fuse ) would
merely produce a loud pop.
.... Phil
Winston
Phil Allison
"Winston"
> Phil Allison wrote:
>> "Winston"
>>
>>> The fuse for my Fluke 79 multimeter retails for $10.00.
>>> (Ten U.S. Dollars)
>>>
>>> http://www.flukeonlinestore.com/3478682.html
>
>> you )
>> from a worst case scenario.
>>
>> That scenario is when you probe a 415 volt, 3 phase power outlet with the
>> meter accidentally set to the 10 amp range.
>>
>> A standard glass fuse would simply arc from end to end, the probes and
>> leads
>> would explode and cover you in hot metal and the meter would become a
>> write
>> off.
>>
>> The specified ( fast acting, high rupture current, high voltage fuse )
>> would
>> merely produce a loud pop.
>
> I didn't know that.
** Cos you know fuck all about anything.
> How about this one?
> http://www.flukeonlinestore.com/3478747.html
>
** Standard glass (fast) fuse by the look of it.
.... Phil
Winston
> "Winston"
(...)
>> I didn't know that.
>
> ** Cos you know fuck all about anything.
It's a continuing problem.
Watta ya gonna do. :)
>> How about this one?
>> http://www.flukeonlinestore.com/3478747.html
>>
>
> ** Standard glass (fast) fuse by the look of it.
It must be ~36 times safer than a commodity GMA
fuse in a multimeter application, yes?
http://www.amazon.com/125mA-250v-Fuses-0-125A-5x20mm/dp/B004HLZYVI
Fluke wouldn't overcharge for that part either,
surely.
--Winston
Phil Allison
"Winston"
** The price is very steep.
But I expect the fuse IS safe when used in the Fluke DMMs it is specified
for.
The scenario with a 0.125A fuse is nothing like the one with the 10A range
fuse.
Typical 0.125A rated fast fuses have resistances of 8 to 10 ohms - which
limits the fault current to a value the fuse can easily break.
A 10 amp fuse may well have a resistance of only a few milliohms, so the
fault current is only limited by the resistance of the DMM's leads.
A current of 40 amps is easy enough for a small fuse to break, while one of
over 4000 amps is not.
Capice?
.... Phil
Winston
> "Winston"
(...)
>> Fluke wouldn't overcharge for that part either,
>> surely.
>
> ** The price is very steep.
We agree.
> But I expect the fuse IS safe when used in the Fluke DMMs it is specified
> for.
Both the 'Fluke' brand and the commodity brand are safe, I suspect.
It wouldn't shock me to learn both kinds are sourced from the same
place.
> The scenario with a 0.125A fuse is nothing like the one with the 10A range
> fuse.
>
> Typical 0.125A rated fast fuses have resistances of 8 to 10 ohms - which
> limits the fault current to a value the fuse can easily break.
>
> A 10 amp fuse may well have a resistance of only a few milliohms, so the
> fault current is only limited by the resistance of the DMM's leads.
>
> A current of 40 amps is easy enough for a small fuse to break, while one of
> over 4000 amps is not.
We agree on that, too.
--Winston
Phil Allison
"Winston"
> Phil Allison wrote:
>> "Winston"
>
>
> We agree.
** Yawnnnnnnnnnnnn....
>
>> But I expect the fuse IS safe when used in the Fluke DMMs it is specified
>> for.
>
> Both the 'Fluke' brand and the commodity brand are safe, I suspect.
>
> It wouldn't shock me to learn both kinds are sourced from the same
> place.
>
** Nothing shocks a fuckwit like you.
>> The scenario with a 0.125A fuse is nothing like the one with the 10A
>> range
>> fuse.
>>
>> Typical 0.125A rated fast fuses have resistances of 8 to 10 ohms -
>> which
>> limits the fault current to a value the fuse can easily break.
>>
>> A 10 amp fuse may well have a resistance of only a few milliohms, so the
>> fault current is only limited by the resistance of the DMM's leads.
>>
>> A current of 40 amps is easy enough for a small fuse to break, while one
>> of
>> over 4000 amps is not.
>
> We agree on that, too.
** GIANT Yawwnnnnnnnnnnnnnnnnnnn
Piss off wanker.
... Phil
Man-wai Chang
> them.
Coz you are in USA, not Hong Kong (ex-UK colony)! :)
--
@~@ Might, Courage, Vision, SINCERITY.
/ v \ Simplicity is Beauty! May the Force and farces be with you!
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Phil Allison
"Man-wai Chang"
>>
>> ** Funny, I have any number of fuses in my bins with "BS 1362" printed on
>> them.
>
> Coz you are in USA, not Hong Kong (ex-UK colony)! :)
** Hey - rice muncher.
I am in Sydney, Australia.
BS1362 fuses are used in professional dimmers imported from the UK.
.... Phil
Man-wai Chang
Hello, wheat muncher!
> I am in Sydney, Australia.
> BS1362 fuses are used in professional dimmers imported from the UK.
How do you tell they were really BS1362 without any printing on the
fuse? So its look is unique among all fuses?
--
@~@ Might, Courage, Vision, SINCERITY.
/ v \ Simplicity is Beauty! May the Force and farces be with you!
/( _ )\ (x86_64 Ubuntu 9.10) Linux 2.6.39
^ ^ 17:59:01 up 7 days 3:01 0 users load average: 0.97 1.03 1.04
Phil Allison
"Man-wai Chang"
>
>> ** Hey - rice muncher.
>
>> BS1362 fuses are used in professional dimmers imported from the UK.
>
> How do you tell they were really BS1362 without any printing on the fuse?
** Learn to fucking read - you stinking Chink moron.
" Funny, I have any number of fuses in my bins with "BS 1362" printed on
them. "
They look much like this - fuckwit.
http://www.betterfuse.com/MyUploadFiles/image/2010-03/2010033110104827.jpg
Figured out what " The quick brown fox jumps over the lazy dog " means
??
Very deep.
.... Phil
Jasen Betts
>
> How dangerous is it to replace a 500mA fast-brown fuse with a 500mA
> slow-brown one?
could be as dangerous as using a nail instead,
--
⚂⚃ 100% natural
Man-wai Chang
> them. "
Sorry!
--
@~@ Might, Courage, Vision, SINCERITY.
/ v \ Simplicity is Beauty! May the Force and farces be with you!
/( _ )\ (x86_64 Ubuntu 9.10) Linux 2.6.39
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bud--
Nice post a couple levels up.
Meters like the Flukes are "Category" rated - 1, 2, 3. When working on
high capacity services, like 1000A 480V, you really want a cat 1
meter. You won't wind up wearing it as in your previous post. The
problem is not just the meter. Arc in meter causes vaporized meter
leads that turns into an arc between busbars - very dangerous.
In addition to the nominal voltage you have the hazard of transients
that could start an arc which will then sustain at the nominal
voltage. In the US, OSHA may also take strong exception to using a
meter without the right cat rating.
One of the hazards in high capacity services is available fault
current, which can be 200,000A. Fuses have a rating for available
fault current. The fix is to use "current limiting" fuses. For high
currents they have a clearing time of under 1/4 cycle. You handle a
200,000A available location by the fuse clearing before the current
increases to anything near that value. The earlier Fluke fuse is
certainly current limiting. The fuse opens before the meter leads turn
to plasma.
The fuse in the later link is a mere 250V - not likely a cat 1 meter.
But a glass 250V GMA fuse in a meter may exceed the fault current
rating for the fuse. One of the fuses in my Fluke is 0.44A and is
almost certainly current limiting.
--
bud--
Winston
(...)
> Nice post a couple levels up.
Thanks!
> Meters like the Flukes are "Category" rated - 1, 2, 3. When working on
> high capacity services, like 1000A 480V, you really want a cat 1
> meter. You won't wind up wearing it as in your previous post. The
> problem is not just the meter. Arc in meter causes vaporized meter
> leads that turns into an arc between busbars - very dangerous.
I learned about 'flashover' only very recently.
Once you know about it, it's obvious.
> In addition to the nominal voltage you have the hazard of transients
> that could start an arc which will then sustain at the nominal
> voltage. In the US, OSHA may also take strong exception to using a
> meter without the right cat rating.
>
> One of the hazards in high capacity services is available fault
> current, which can be 200,000A. Fuses have a rating for available
> fault current. The fix is to use "current limiting" fuses. For high
> currents they have a clearing time of under 1/4 cycle. You handle a
> 200,000A available location by the fuse clearing before the current
> increases to anything near that value. The earlier Fluke fuse is
> certainly current limiting. The fuse opens before the meter leads turn
> to plasma.
So *that's* the '40,000 A' number in the 11A fuse ratings.
I always wondered about those stunningly huge numbers.
> The fuse in the later link is a mere 250V - not likely a cat 1 meter.
I pointed to that fuse to show that Fluke were not
undercharging for replacement parts. :)
That fuse is in a 'hobby / light industrial' instrument.
> But a glass 250V GMA fuse in a meter may exceed the fault current
> rating for the fuse. One of the fuses in my Fluke is 0.44A and is
> almost certainly current limiting.
That's the same package as the 11 A fuse I originally mentioned.
Ironically, I popped it measuring automotive electrical stuff.
(Note to self: Don't leave meters on the bench with the probes
connected to measure current!) :)
Lesson learned.
--Winston
Winston
(...)
> Piss off wanker.
You are so beautiful when you are angry, Phil.
--Winston :)
Jamie
no, he's not angry, he's being Phil.
Jamie
Winston
Michael A. Terrell
Man-wai Chang wrote:
>
> > " Funny, I have any number of fuses in my bins with "BS 1362" printed on
> > them. "
>
> Sorry!
Ignore Phil. He's mentally ill, and off his medication most of the
time.
Phil Allison
"Michael A. Terrell"
> Man-wai Chang wrote:
** Ignore Terrell.
He's a rabid psychopath, wheelchair bound and lives in the Florida
everglades in a caravan.
He knows he is gonna die a horrible death.
And it cannot come too soon for me.
... Phil
Man-wai Chang
> time.
I really mis-interpreted his sentence. Apology is necessary! :)
--
@~@ Might, Courage, Vision, SINCERITY.
/ v \ Simplicity is Beauty! May the Force and farces be with you!
/( _ )\ (x86_64 Ubuntu 9.10) Linux 2.6.39
^ ^ 16:22:01 up 8 days 1:24 0 users load average: 1.02 1.07 1.12
Man-wai Chang
> high capacity services, like 1000A 480V, you really want a cat 1
> meter. You won't wind up wearing it as in your previous post. The
> problem is not just the meter. Arc in meter causes vaporized meter
> leads that turns into an arc between busbars - very dangerous.
The physics books I read did NOT talk about this danger. So were all the
physics teachers that taught me. Maybe I fell asleep when they talked
about this. In short, the "art" of choosing the right multimeter for the
right job was not covered by the physics course material of my school time.
It's really lucky that I was never hurt so far when playg with hobby
circuits...
--
@~@ Might, Courage, Vision, SINCERITY.
/ v \ Simplicity is Beauty! May the Force and farces be with you!
/( _ )\ (x86_64 Ubuntu 9.10) Linux 2.6.39
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Man-wai Chang
> could be as dangerous as using a nail instead,
Good analogy! :)
Phil Allison
Michael A. Terrell"
Man-wai Chang wrote:
** Ignore the Terrell fuckwit..
He's a rabid psychopath, wheelchair bound and lives in the Florida
everglades in a rusty caravan.
Phil Allison
"Man-wai Chang"
> The physics books I read did NOT talk about this danger. So were all the
> physics teachers that taught me. Maybe I fell asleep when they talked
> about this. In short, the "art" of choosing the right multimeter for the
> right job was not covered by the physics course material of my school
> time.
** So fucking what ???
Did your physics course cover making Dim Sims ??
Or the Chinese Revolution by " Ou Flung Dung " ??
.... Phil
Phil Allison
"Man-wai Chang"
> Good analogy! :)
** Shame you are not an analogy to anything human.
.... Phil
Michael A. Terrell
Phil Allison wrote:
>
> Michael A. Terrell"
> Man-wai Chang wrote:
>
> ** Ignore the Terrell fuckwit..
>
> He's a rabid psychopath, wheelchair bound and lives in the Florida
> everglades in a rusty caravan.
Liar. I do use a cane becasue of a bad knee. I live in a three
bedroom house, with a 1200 square foot shop building. I also have a one
bedroom cottage on my property. I am over one hundred of miles from the
Everglades as well.
You live in a tiny, crappy apartment filled with old stereos, and
mutilated toasters.
> He knows he is gonna die a horrible death.
Is there any pleasant death? That is, other than when a loser like
you goes away?
> And it cannot come too soon for me.
Not going to happen, Phil. Unless you steal enough money to carry out
your death threats.
Anyone who is on any electronics newsgroup for very long sees what a
shrieking psychopath you are when you're off your medication.
Phil Allison
"Michael A. Terrell
> Phil Allison wrote:
>
>> ** Ignore the Terrell fuckwit..
>>
>> He's a rabid psychopath, wheelchair bound and lives in the Florida
>> everglades in a rusty caravan.
>
>
>
>
> Not going to happen, Phil.
** You are one sick man.
Mentally and physically.
A raving criminal psychopath of the gutless scumbag kind.
You imminent death will be cause for great celebration.
..... Phil
Jamie
>> Meters like the Flukes are "Category" rated - 1, 2, 3. When working on
>> high capacity services, like 1000A 480V, you really want a cat 1
>> meter. You won't wind up wearing it as in your previous post. The
>> problem is not just the meter. Arc in meter causes vaporized meter
>> leads that turns into an arc between busbars - very dangerous.
>
>
> The physics books I read did NOT talk about this danger. So were all the
> physics teachers that taught me. Maybe I fell asleep when they talked
> about this. In short, the "art" of choosing the right multimeter for the
> right job was not covered by the physics course material of my school time.
>
> It's really lucky that I was never hurt so far when playg with hobby
> circuits...
>
don't feel so bad, it used to be an accepted practice to use your index
finger and thumb as a go-no-go voltage test.. I know some one that has
one of the first NEC or what ever they called it back then, books, with
that statement in it.
Jamie
Phil Allison
"Jamie the fuckwit radio ham"
Man-wai Chang = Dim as he Sim
>> The physics books I read did NOT talk about this danger. So were all the
>> physics teachers that taught me. Maybe I fell asleep when they talked
>> about this. In short, the "art" of choosing the right multimeter for the
>> right job was not covered by the physics course material of my school
>> time.
>>
>> It's really lucky that I was never hurt so far when playg with hobby
>> circuits...
** So fucking what ???
Did your physics course cover making Dim Sims ??
Or the Chinese Revolution by " Ou Flung Dung " ??
You pathetic Wang Ker !!!
.... Phil
Man-wai Chang
> Or the Chinese Revolution by " Ou Flung Dung " ??
> You pathetic Wang Ker !!!
When are you going to write a book on circuitries? :)
--
@~@ Might, Courage, Vision, SINCERITY.
/ v \ Simplicity is Beauty! May the Force and farces be with you!
/( _ )\ (x86_64 Ubuntu 9.10) Linux 2.6.39
^ ^ 22:34:02 up 8 days 7:36 0 users load average: 1.09 1.05 1.05
Phil Allison
"Man-wai Chang" <toylet...@gmail.com>
** See the reference to shit head.
> When are you going to write a book on circuitries? :)
** When are you going to stick you fat head up a dead dragon's arse ??
BTW:
Still no idea what Confucius meant by:
" The quick brown fox jumps over the lazy dog "
Wang Kerr.
... Phil
bud--
> bud-- wrote:
>
> (...)
>
> > Nice post a couple levels up.
>
> Thanks!
>
> > Meters like the Flukes are "Category" rated - 1, 2, 3. When working on
> > high capacity services, like 1000A 480V, you really want a cat 1
> > meter. You won't wind up wearing it as in your previous post. The
> > problem is not just the meter. Arc in meter causes vaporized meter
> > leads that turns into an arc between busbars - very dangerous.
>
> I learned about 'flashover' only very recently.
> Once you know about it, it's obvious.
Called arc-flash in US. The hazard isn't always obvious. One of the
smartest electricians I have run across wanted to measure the motor
current in a food plant. The motor starters were in a motor control
center, which is a frame with many motor starter modules - busbar feed
in back. He defeated the door interlock, opened the module door and
put a clamp-on ammeter on one of the contactor motor wires - all
absolutely routine. No one knows what happened - the guess was there
was a loose screw. In any case there was an arc-flash. He had bad
burns, some from vaporized copper condensing on his skin. He spent a
lot of time in the hospital with multiple plastic surgeries. But he
survived. You can be killed from burns, concussion from the explosion,
shrapnel.
These days to be OSHA compliant and make the same measurement you
might have to wear an arc-flash suit. OSHA interest in arc-flash is
relatively recent. Some related equipment issues are now in the US-
NEC.
>
> > In addition to the nominal voltage you have the hazard of transients
> > that could start an arc which will then sustain at the nominal
> > voltage. In the US, OSHA may also take strong exception to using a
> > meter without the right cat rating.
>
> > One of the hazards in high capacity services is available fault
> > current, which can be 200,000A. Fuses have a rating for available
> > fault current. The fix is to use "current limiting" fuses. For high
> > currents they have a clearing time of under 1/4 cycle. You handle a
> > 200,000A available location by thefuseclearing before the current
> > increases to anything near that value. The earlier Flukefuseis
> > certainly current limiting. Thefuseopens before the meter leads turn
> > to plasma.
>
> So *that's* the '40,000 A' number in the 11Afuseratings.
> I always wondered about those stunningly huge numbers.
>
A commonly available Bussmann FRN 20A fuse is "current limiting" and
rated for 200,000A available fault current. But much bigger.
--
bud--
Man-wai Chang
dragon? you meant this one: http://sites.google.com/site/changmw/
> Still no idea what Confucius meant by:
> " The quick brown fox jumps over the lazy dog"
That's not a chinese idiom as far as I knew.... you have the chinese words?
--
@~@ Might, Courage, Vision, SINCERITY.
/ v \ Simplicity is Beauty! May the Force and farces be with you!
/( _ )\ (x86_64 Ubuntu 9.10) Linux 2.6.39
^ ^ 00:14:01 up 8 days 9:16 0 users load average: 1.04 1.14 1.12
Smitty Two
Man-wai Chang <toylet...@gmail.com> wrote:
> > ** When are you going to stick you fat head up a dead dragon's arse ??
>
> dragon? you meant this one: http://sites.google.com/site/changmw/
>
> > Still no idea what Confucius meant by:
> > " The quick brown fox jumps over the lazy dog"
>
> That's not a chinese idiom as far as I knew.... you have the chinese words?
It's a typing exercise. Contains every letter of the alphabet. Stop
taking Phil seriously.
Man-wai Chang
> taking Phil seriously.
Thanks. I wonder whether he/she met a REAL dragon before! :)
--
@~@ Might, Courage, Vision, SINCERITY.
/ v \ Simplicity is Beauty! May the Force and farces be with you!
/( _ )\ (x86_64 Ubuntu 9.10) Linux 2.6.39
^ ^ 00:34:01 up 8 days 9:36 0 users load average: 1.10 1.08 1.09
Rich Grise
http://www.youtube.com/watch?v=FQMbXvn2RNI
Pay particular attention at 3:40
Cheers!
Rich
Rich Grise
manipulating the probe, and the other hand in your pocket or tied behind
your back, that sometimes people will ground their thumb or more likely
little (pinkie) finger, so that when they _do_ get zapped, it only burns
their hand and doesn't go through their heart and cause fibrillation or
cardiac arrest.
Hope This Helps!
Rich
Winston
> On Jun 1, 1:30 pm, Winston<Wins...@BigBrother.net> wrote:
(...)
>> I learned about 'flashover' only very recently.
>> Once you know about it, it's obvious.
>
> Called arc-flash in US.
Yes.
> The hazard isn't always obvious.
I meant 'conceptually speaking'. At higher voltage levels,
a lot more objects look like conductors. At higher current
levels, a lot more objects *continue* to be conductors.
When we combine higher voltage with higher current, it is
amazing that more electricians aren't injured.
I spent my career working on the really low-power
end of the spectrum and never thought about high-power
hazards. I recently helped troubleshoot a 208 V
3 phase system and thought I was in the 'big leagues'!
Um. Turns out I wasn't. :)
> One of the
> smartest electricians I have run across wanted to measure the motor
> current in a food plant. The motor starters were in a motor control
> center, which is a frame with many motor starter modules - busbar feed
> in back. He defeated the door interlock, opened the module door and
> put a clamp-on ammeter on one of the contactor motor wires - all
> absolutely routine. No one knows what happened - the guess was there
> was a loose screw. In any case there was an arc-flash. He had bad
> burns, some from vaporized copper condensing on his skin. He spent a
> lot of time in the hospital with multiple plastic surgeries. But he
> survived. You can be killed from burns, concussion from the explosion,
> shrapnel.
That's one of those situations where living can be worse
than dying.
> These days to be OSHA compliant and make the same measurement you
> might have to wear an arc-flash suit. OSHA interest in arc-flash is
> relatively recent. Some related equipment issues are now in the US-
> NEC.
http://www.texsoinstruments.com/arc-flash-suits
I see that this company makes several suits that apparently
comply to NFPA 70E but only their most expensive is said to
protect against shrapnel and none are said to protect
against plasma (reasonably enough!).
I guess 'something' is better than nothing.
(...)
(Snip fuse 'fault current rating')
>> So *that's* the '40,000 A' number in the 11A fuse ratings.
>> I always wondered about those stunningly huge numbers.
>>
>
> A commonly available Bussmann FRN 20A fuse is "current limiting" and
> rated for 200,000A available fault current. But much bigger.
Whoa.
--Winston
bud--
> bud-- wrote:
> > On Jun 1, 1:30 pm, Winston<Wins...@BigBrother.net> wrote:
>
> (...)
>
> >> I learned about 'flashover' only very recently.
> >> Once you know about it, it's obvious.
>
> > Called arc-flash in US.
>
> Yes.
>
> > The hazard isn't always obvious.
>
> I meant 'conceptually speaking'. At higher voltage levels,
> a lot more objects look like conductors. At higher current
> levels, a lot more objects *continue* to be conductors.
> When we combine higher voltage with higher current, it is
> amazing that more electricians aren't injured.
>
> I spent my career working on the really low-power
> end of the spectrum and never thought about high-power
> hazards. I recently helped troubleshoot a 208 V
> 3 phase system and thought I was in the 'big leagues'!
>
> Um. Turns out I wasn't. :)
There was a building downtown, maybe 8 stories, that burned down. Just
the 1st floor and basement were left, and they were used as a parking
lot. The existing service remained - a mere 208/120V, but fed by 4 or
6 parallel conductors. They cleverly stored ice melting salt on top of
the service. It burned down. The utility guys said some of the
conductors burned back into the supply conduits and remained hot. Some
others burned back and welded to the conduit. (They were fed at the
utility end with "cable limiters", which are lugs combined with fuses.
Limiters on the welded cables opened.)
>
> > One of the
>
> > smartest electricians I have run across wanted to measure the motor
> > current in a food plant. The motor starters were in a motor control
> > center, which is a frame with many motor starter modules - busbar feed
> > in back. He defeated the door interlock, opened the module door and
> > put a clamp-on ammeter on one of the contactor motor wires - all
> > absolutely routine. No one knows what happened - the guess was there
> > was a loose screw. In any case there was an arc-flash. He had bad
> > burns, some from vaporized copper condensing on his skin. He spent a
> > lot of time in the hospital with multiple plastic surgeries. But he
> > survived. You can be killed from burns, concussion from the explosion,
> > shrapnel.
>
> That's one of those situations where living can be worse
> than dying.
>
> > These days to be OSHA compliant and make the same measurement you
> > might have to wear an arc-flash suit. OSHA interest in arc-flash is
> > relatively recent. Some related equipment issues are now in the US-
> > NEC.
>
> http://www.texsoinstruments.com/arc-flash-suits
>
> I see that this company makes several suits that apparently
> comply to NFPA 70E but only their most expensive is said to
> protect against shrapnel and none are said to protect
> against plasma (reasonably enough!).
> I guess 'something' is better than nothing.
Far as I know NFPA 70E is not adopted as an enforceable standard
anywhere, but is the default standard for working on electrical
equipment (arc-flash is only part of it). Protection required for arcs
depends on voltage, available fault current, clearing time of the
overcurrent protection, and distance. "Current limiting" fuses, with
fast clearing times, can greatly limit the damage to equipment and
hazard to workers. New equipment is supposed to get a label giving the
hazard (calories per square cm.). One label I saw said there was there
was no safe protection.
Plasma is at the arc, and you should get blown away from it, an
advantage of the explosion.
The emphasis is to work on dead circuits. I am not sure how you do
useful work in an arc flash suit. Can't remember - the protection may
be so you 'only' get 2nd degree burns, but a lot better than
"nothing". One of the things you don't want to wear is polyester - it
melts.
>
> >> So *that's* the '40,000 A' number in the 11Afuseratings.
> >> I always wondered about those stunningly huge numbers.
>
> > A commonly available Bussmann FRN 20Afuseis "current limiting" and
> > rated for 200,000A available fault current. But much bigger.
>
> Whoa.
>
It is a commonly used garden variety 2" x 0.5"d "time delay" cartridge
fuse. It is safe on 200kA available by clearing long before the
current through it reaches 200kA.
--
bud--
Robert Macy
Two somewhat related incidences:
To pass a very stringent British Telecom specification that equipment
would survive adjacent equipment blowing a fuse, I desigened a
'transient generator' using 4 12Vdc 500A vehicle batteries in series
with a 50 ft 0000 Awg coil (to provide a bit of inductance), a starter
solenoid, and a fuse. The idea is the fuse shorts the 48 V, then
blows, and you get a 300+volt surge that wants to put more than 300A
someplace. If your adjacent equipment uses a 'shorting' protection
method, God save us all! The surge will strip off 1/4 inch wide traces
on a PCB. Anyway, I tested all kinds of fuses and discovered the fuse
designers very intelligently designed the fuse to 'gently' blow, just
die, go away. It turned out the BEST fuse for this test equipment
was a small 3AG 1A FB, went off like a flash bulb, and created the 'in-
spec' waveforms.
While visiting an Alcoa plant (in Iowa?), I saw a large casting of
aluminum, approx 18 feet long, 14 to 18 inches tall and 10 inches
wide, of a very strange shape. I was told that that was ordered by a
utility company. It is a FUSE and they had just blown one on one of
their high tension distribution lines and this was the replacement!
Now you want shrapnel and melted metal. Blowing that kind of fuse
must be awesome to behold.
Regards,
Winston
(...)
> There was a building downtown, maybe 8 stories, that burned down. Just
> the 1st floor and basement were left, and they were used as a parking
> lot. The existing service remained - a mere 208/120V, but fed by 4 or
> 6 parallel conductors. They cleverly stored ice melting salt on top of
> the service. It burned down. The utility guys said some of the
> conductors burned back into the supply conduits and remained hot. Some
> others burned back and welded to the conduit. (They were fed at the
> utility end with "cable limiters", which are lugs combined with fuses.
> Limiters on the welded cables opened.)
'Cable limiters'. That's a new one on me.
If it weren't for the guys that insist on 'belt, suspenders *and* rope,
we'd be caught with out pants down much more often.
(...)
> Plasma is at the arc, and you should get blown away from it, an
> advantage of the explosion.
"It's A Feature!" we explained, as the electrician (slumped against the
wall on the other side of the garage) finally opened his eyes.
This'll be my entry! http://www.bulwer-lytton.com/
> The emphasis is to work on dead circuits. I am not sure how you do
> useful work in an arc flash suit. Can't remember - the protection may
> be so you 'only' get 2nd degree burns, but a lot better than
> "nothing". One of the things you don't want to wear is polyester - it
> melts.
Which wouldnt be too bad, except that it *sticks* too. Ouch.
(...)
> It is a commonly used garden variety 2" x 0.5"d "time delay" cartridge
> fuse. It is safe on 200kA available by clearing long before the
> current through it reaches 200kA.
I use my arc welder at ~120A (~30 V) for my hobby projects.
I'm trying unsuccessfully to get a visceral understanding of 200kA
at 220 V.
--Winston <-- Nope. Still don't get it.
Winston
(...)
> It turned out the BEST fuse for this test equipment
> was a small 3AG 1A FB, went off like a flash bulb, and created the 'in-
> spec' waveforms.
I wonder what those waveforms looked like?
I *guess* that there was a >> 1 A current spike as the surge power
ionized the fuse element, then down to zero.
Or did the current peak at just over 1.0 A?
> While visiting an Alcoa plant (in Iowa?), I saw a large casting of
> aluminum, approx 18 feet long, 14 to 18 inches tall and 10 inches
> wide, of a very strange shape. I was told that that was ordered by a
> utility company. It is a FUSE and they had just blown one on one of
> their high tension distribution lines and this was the replacement!
> Now you want shrapnel and melted metal. Blowing that kind of fuse
> must be awesome to behold.
The installation manual for that fuse must be a work of art.
Imagine trying to keep the oxide off of the contact surfaces!
--Winston
William Sommerwerck
news:isbc0...@news5.newsguy.com...
> The installation manual for that fuse must be a work of art.
> Imagine trying to keep the oxide off of the contact surfaces!
All you need is a gallon jug of Cramolin!
Winston
Rich Grise
>
> I use my arc welder at ~120A (~30 V) for my hobby projects.
> I'm trying unsuccessfully to get a visceral understanding of 200kA
> at 220 V.
>
Cheers!
Rich
Robert Macy
From Alcoa employee: the utility breaker was mounted on top the towers
and simply bolts in place with the surface the contact. Once bolted,
no oxide can form.
From memory [can somebody find the reference number and post the
waveform], British Telecom Spec defined the 'boundaries of the voltage
waveform at the EUT's terminals and added that 350+A is available
during the waveform. During fuse blowing, the GND went down to -10
and the -48 came up to -20, then pops with a risetime [can't remember
the risetime] GND goes positive 30 or 40V and the -48 goes way down to
-300, or -500V and then decays back up to above -60 volts in 50mS.
That is a VERY long time for electronics.
The energy is approx 1/2 * 300V * 350A * 0.05 = 2600 joules When you
consider that the large protection MOV's inside your PC power strip
are rated for 5 - 10 j; you have some idea of the energy potentially
shoved into a telecom unit.
From memory and my understanding that the origin of the spec came
about after ....Telecom equipment are placed in racks in a room, the
batteries are usually in another room and 1 inch diameter rods go from
the batteries through the wall to the equipment room. At the equipment
room cables go down to the rods and simply clamp on the rods to get
power to an individual rack. A workman dropped his wrench across the
rods. The wrench was never found. The surge described in the spec
probably occurred, or worse, so the WHOLE room of equipment blew out,
destroyed. Since British Telecom had purchased all the equipment
without that power surge specced, British Telecom had to eat the loss,
thus the origin of the spec in future BT purchases.
The fuse and wiring and solenoid would pass up to 350 Amps, but not
for long, before the fuse disappeared. By the way, the coil of wire
would 'jump' up off the floor when the fuse went. When I first built
up the equipment, I insisted on placing everything inside a separate
room and activating remotely, just in case we lost a battery! We
never lost a battery. Turned out luckily to be an unnecessary
precaution.
Somewhere on the internet there must be pictures/videos of fuses
blowing under extreme current conditions. In such a picture, I
remember seeing a 'cone' of blasted metal progressing from some weak
point in the wire along the wire until most of it was gone. Plus
blowing a fuse in a controlled magnetic field will yield very
destructive EMP. Do a search for such weaponry. Perhaps, videos are
there.
Regards,
Robert
Winston
(Snip installation details of stunningly huge over-current
protection device)
> From Alcoa employee: the utility breaker was mounted on top the towers
> and simply bolts in place with the surface the contact. Once bolted,
> no oxide can form.
Sounds like the geometry and pressure used for the contact surfaces
was such that it broke through existing aluminum oxides and created
a gas - tight seal in the connector area. Sounds simple if you don't
have to actually design to achieve that effect. :)
(Snip effect of shorting huge batteries through an inductor)
Thanks! Very interesting!
--Winston