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Fuse: fast blown vs slow blown
How dangerous is it to replace a 500mA fast-brown fuse with a 500mA slow-brown 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 ^ ^ 19:36:01 up 6 days 4:38 0 users load average: 1.22 1.09 1.06 不借貸! 不詐騙! 不援交! 不打交! 不打劫! 不自殺! 請考慮綜援 (CSSA): http://www.swd.gov.hk/tc/index/site_...sub_addressesa |
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? ** Confucius once say: " The quick brown fox jumps over the lazy dog " Think about it ........... ..... Phil |
Fuse: fast blown vs slow blown
On May 31, 7:41*am, Man-wai Chang wrote:
How dangerous is it to replace a 500mA fast-brown fuse with a 500mA slow-brown 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 * *^ ^ * 19:36:01 up 6 days 4:38 0 users load average: 1.22 1.09 1.06 不借貸! 不詐騙! 不援交! 不打交! 不打劫! 不自殺! 請考慮綜援 (CSSA):http://www.swd.gov.hk/tc/index/site_...sub_addressesa 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. |
Fuse: fast blown vs slow blown
"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 |
Fuse: fast blown vs slow blown
On 05/31/2011 04:41 AM, Man-wai Chang wrote:
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 |
Fuse: fast blown vs slow blown
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? -- @~@ 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 ^ ^ 23:56:02 up 6 days 8:58 0 users load average: 1.05 1.09 1.06 不借貸! 不詐騙! 不援交! 不打交! 不打劫! 不自殺! 請考慮綜援 (CSSA): http://www.swd.gov.hk/tc/index/site_...sub_addressesa |
Fuse: fast blown vs slow blown
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? -- @~@ 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 ^ ^ 23:56:02 up 6 days 8:58 0 users load average: 1.05 1.09 1.06 不借貸! 不詐騙! 不援交! 不打交! 不打劫! 不自殺! 請考慮綜援 (CSSA): http://www.swd.gov.hk/tc/index/site_...sub_addressesa |
Fuse: fast blown vs slow blown
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. -- 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 |
Fuse: fast blown vs slow blown
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. -- 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 |
Fuse: fast blown vs slow blown
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. 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 ^ ^ 00:36:01 up 6 days 9:38 0 users load average: 1.12 1.09 1.12 不借貸! 不詐騙! 不援交! 不打交! 不打劫! 不自殺! 請考慮綜援 (CSSA): http://www.swd.gov.hk/tc/index/site_...sub_addressesa |
Fuse: fast blown vs slow blown
On Tue, 31 May 2011 09:02:08 -0700, Tim Wescott
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 150 Felker St #D http://www.LearnByDestroying.com Santa Cruz CA 95060 http://802.11junk.com Skype: JeffLiebermann AE6KS 831-336-2558 |
Fuse: fast blown vs slow blown
On Tue, 31 May 2011 23:57:58 +0800, Man-wai Chang
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. -- Jeff Liebermann 150 Felker St #D http://www.LearnByDestroying.com Santa Cruz CA 95060 http://802.11junk.com Skype: JeffLiebermann AE6KS 831-336-2558 |
Fuse: fast blown vs slow blown
Tim Wescott 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? 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 |
Fuse: fast blown vs slow blown
On 05/31/2011 10:16 AM, Winston wrote:
Tim Wescott 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? 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? Uhhh... D'oh! -- 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 |
Fuse: fast blown vs slow blown
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? yes |
Fuse: fast blown vs slow blown
Jeff Liebermann wrote:
On Tue, 31 May 2011 09:02:08 -0700, Tim Wescott 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 |
Fuse: fast blown vs slow blown
Jeff Liebermann wrote: On Tue, 31 May 2011 09:02:08 -0700, Tim Wescott 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. |
Fuse: fast blown vs slow blown
Man-wai Chang wrote:
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." |
Fuse: fast blown vs slow blown
Man-wai Chang Inscribed thus:
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. |
Fuse: fast blown vs slow blown
"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 |
Fuse: fast blown vs slow blown
Tim Wescott wrote:
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. |
Fuse: fast blown vs slow blown
"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 |
Fuse: fast blown vs slow blown
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 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. I didn't know that. How about this one? http://www.flukeonlinestore.com/3478747.html --Winston :) |
Fuse: fast blown vs slow blown
"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 ** 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. I didn't know that. ** Cos you know **** all about anything. How about this one? http://www.flukeonlinestore.com/3478747.html ** Standard glass (fast) fuse by the look of it. ..... Phil |
Fuse: fast blown vs slow blown
Phil Allison wrote:
"Winston" (...) I didn't know that. ** Cos you know **** 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-Fus.../dp/B004HLZYVI Fluke wouldn't overcharge for that part either, surely. --Winston |
Fuse: fast blown vs slow blown
"Winston" Phil Allison wrote: I didn't know that. ** Cos you know **** 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-Fus.../dp/B004HLZYVI Fluke wouldn't overcharge for that part either, surely. ** 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 |
Fuse: fast blown vs slow blown
Phil Allison wrote:
"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 |
Fuse: fast blown vs slow blown
"Winston" Phil Allison wrote: "Winston" ** The price is very steep. 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 ****wit 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 **** off ******. .... Phil |
Fuse: fast blown vs slow blown
** 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)! :) -- @~@ 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 ^ ^ 14:44:01 up 6 days 23:46 0 users load average: 1.00 1.01 1.05 不借貸! 不詐騙! 不援交! 不打交! 不打劫! 不自殺! 請考慮綜援 (CSSA): http://www.swd.gov.hk/tc/index/site_...sub_addressesa |
Fuse: fast blown vs slow blown
"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 |
Fuse: fast blown vs slow blown
** Hey - rice muncher.
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 不借貸! 不詐騙! 不援交! 不打交! 不打劫! 不自殺! 請考慮綜援 (CSSA): http://www.swd.gov.hk/tc/index/site_...sub_addressesa |
Fuse: fast blown vs slow blown
"Man-wai Chang" ** Hey - rice 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? ** Learn to ****ing 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 - ****wit. http://www.betterfuse.com/MyUploadFi...3110104827.jpg Figured out what " The quick brown fox jumps over the lazy dog " means ?? Very deep. ..... Phil |
Fuse: fast blown vs slow blown
On 2011-05-31, Man-wai Chang wrote:
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 |
Fuse: fast blown vs slow blown
" Funny, I have any number of fuses in my bins with "BS 1362" printed on
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 ^ ^ 20:09:01 up 7 days 5:11 0 users load average: 1.04 1.09 1.08 不借貸! 不詐騙! 不援交! 不打交! 不打劫! 不自殺! 請考慮綜援 (CSSA): http://www.swd.gov.hk/tc/index/site_...sub_addressesa |
Fuse: fast blown vs slow blown
On Jun 1, 12:09*am, "Phil Allison" wrote:
"Winston" Phil Allison wrote: I didn't know that. ** Cos you know **** 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-Fus.../dp/B004HLZYVI Fluke wouldn't overcharge for that part either, surely. ** 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? 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-- |
Fuse: fast blown vs slow blown
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. 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 |
Fuse: fast blown vs slow blown
Phil Allison wrote:
(...) **** off ******. You are so beautiful when you are angry, Phil. --Winston :) |
Fuse: fast blown vs slow blown
Winston wrote:
Phil Allison wrote: (...) **** off ******. You are so beautiful when you are angry, Phil. --Winston :) no, he's not angry, he's being Phil. Jamie |
Fuse: fast blown vs slow blown
Jamie wrote:
Winston wrote: Phil Allison wrote: (...) **** off ******. You are so beautiful when you are angry, Phil. --Winston :) no, he's not angry, he's being Phil. http://en.wikipedia.org/wiki/Coprolalia I see. --Winston |
Fuse: fast blown vs slow blown
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. -- It's easy to think outside the box, when you have a cutting torch. |
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