---------------------------------------------------------- AeroElectric-List Digest Archive --- Total Messages Posted Wed 11/23/22: 5 ---------------------------------------------------------- Today's Message Index: ---------------------- 1. 05:12 AM - Re: Fusible Links in lieu of ANL protectors (rockitdoc) 2. 05:48 AM - Re: Fusible Links in lieu of ANL protectors (rockitdoc) 3. 05:53 AM - Fusible Link Performance vs ANL Current Limiters (rockitdoc) 4. 08:05 AM - Re: Re: Fusible Links in lieu of ANL protectors (Robert L. Nuckolls, III) 5. 08:54 AM - Re: Fusible Link Performance vs ANL Current Limiters (Robert L. Nuckolls, III) ________________________________ Message 1 _____________________________________ Time: 05:12:59 AM PST US Subject: AeroElectric-List: Re: Fusible Links in lieu of ANL protectors From: "rockitdoc" nuckolls.bob(at)aeroelect wrote: > At 05:25 PM 11/22/2022, you wrote: > > > > > I am building an RV14A. I planned on using ANL current limiters for the two alternators (60A PP and 40AB&C), but have since learned of these fusible link thingys. I would prefer not to drill more holes in my firewall to mount the ANLs an fusible links would foot the bill nicely. That is, if they provide the services necessary to protect stuff. > > Fusible links are the way to go. Just splice them onto the > risk-source end of your protected feeder. > > For the big alternator, I suggest an 8AWG (or larger) > feeder with this fusible link. > > https://tinyurl.com/2md9xov3 > > For the little alternator build a 10AWG feeder (or larger) > with this fusible link. > > https://tinyurl.com/2mek723r (https://tinyurl.com/2mek723r) > > These are just a few options. You can buy > BULK fusible link wire but you wind up with > a extra wire you will probably > never need. Buying automotive pre-fab > links is a lot less fussy and nothing > to inventory. > > > > Bob . . . > > Un impeachable logic: George Carlin asked, "If black boxes > survive crashes, why don't they make the whole airplane > out of that stuff?" Thanks, Bob. Do I need to protect the fusible link with a fire sleeve, or do the ready-made versions come with protection? And, for that matter, does the bulk fusible link wire come with protection? Scott -------- RV14A Began 7-23-20 Fuse and tail Completed 2-20-21 Wings 99% Finish 90% Engine 99% Wiring in Process Read this topic online here: http://forums.matronics.com/viewtopic.php?p=509082#509082 ________________________________ Message 2 _____________________________________ Time: 05:48:19 AM PST US Subject: AeroElectric-List: Re: Fusible Links in lieu of ANL protectors From: "rockitdoc" nuckolls.bob(at)aeroelect wrote: > At 05:25 PM 11/22/2022, you wrote: > > > > > I am building an RV14A. I planned on using ANL current limiters for the two alternators (60A PP and 40AB&C), but have since learned of these fusible link thingys. I would prefer not to drill more holes in my firewall to mount the ANLs an fusible links would foot the bill nicely. That is, if they provide the services necessary to protect stuff. > > Fusible links are the way to go. Just splice them onto the > risk-source end of your protected feeder. > > For the big alternator, I suggest an 8AWG (or larger) > feeder with this fusible link. > > https://tinyurl.com/2md9xov3 > > For the little alternator build a 10AWG feeder (or larger) > with this fusible link. > > https://tinyurl.com/2mek723r (https://tinyurl.com/2mek723r) > > These are just a few options. You can buy > BULK fusible link wire but you wind up with > a extra wire you will probably > never need. Buying automotive pre-fab > links is a lot less fussy and nothing > to inventory. > > > > Bob . . . > > Un impeachable logic: George Carlin asked, "If black boxes > survive crashes, why don't they make the whole airplane > out of that stuff?" Thanks, Bob. Do I need to protect the fusible link with a fire sleeve, or do the ready-made versions come with protection? And, for that matter, does the bulk fusible link wire come with protection? Scott -------- RV14A Began 7-23-20 Fuse and tail Completed 2-20-21 Wings 99% Finish 90% Engine 99% Wiring in Process Read this topic online here: http://forums.matronics.com/viewtopic.php?p=509083#509083 ________________________________ Message 3 _____________________________________ Time: 05:53:13 AM PST US Subject: AeroElectric-List: Fusible Link Performance vs ANL Current Limiters From: "rockitdoc" I read a good review of this but cannot find it anywhere. Can somebody lead me to it. The discussion regarded why the fusible link was a better method than the ANL for electrical protection near the alternators. -------- RV14A Began 7-23-20 Fuse and tail Completed 2-20-21 Wings 99% Finish 90% Engine 99% Wiring in Process Read this topic online here: http://forums.matronics.com/viewtopic.php?p=509084#509084 ________________________________ Message 4 _____________________________________ Time: 08:05:51 AM PST US From: "Robert L. Nuckolls, III" Subject: Re: AeroElectric-List: Re: Fusible Links in lieu of ANL protectors >Thanks, Bob. > >Do I need to protect the fusible link with a >fire sleeve, or do the ready-made versions come >with protection? And, for that matter, does the >bulk fusible link wire come with protection? > >Scott Check the ones in your car . . . I wrote about his back in 2018 which I repeat here: >Thanks so much...as usual a real education.=C2 =C2 >I had no idea that a 22 AWG fuselink is >equivalent to a 30-40AMP fuse.=C2 =C2 Intuitively I >thought it was much less.=C2 =C2 Much appreciated. > >So if a 22AWG wire is normally "rated" to 5A >which means 10degC (Ch8-8) current rise >presumably therefore needs 40A to get to melting point.=C2 Exactly . . . see https://goo.gl/zye61w Circuit protection is about keeping insulation temperatures comfortably below maximum rated operating vales. Wire size is all about maintaining distribution voltage drops below acceptable levels based on system design goals. 5% is the max-drop rule of thumb although other values may be adopted by program managers. Wire sizing tends to be very conservative . . . unless you are as weight-sensitive as a moon mission or Voyager flight, the design rules will keep wires pretty cool. >By the same token the 16AWG fuselink at the >starter contactor (from the alternator) and from >the battery contactor to the buss performs in a >similar way. If this is correct the 16AWG >fuselink rated at 12.5A for 10 degC current rise >will melt at something like 100A. Whereas the >12AWG wire it's protecting will melt at something like 150. Fusible links in vehicles are expected to protect major feeders of a distribution system against hard faults . . . generally experienced only during major disassembly of the vehicle. By hard fault, were talking many times hundreds to thousands of amps supplied by a battery . . . not the soft fault precipitated by a failing appliance. https://goo.gl/QEBeZs >Is this correct? Generally . . . When we use plain-vanilla wire as a fusible link in the OBAM aircraft world, it's a good idea to use the silicone/fiberglas sleeving over it to limit the propagation of heat damage during a fusing event. In the ground transportation industries, fusible links are fabricated from wire having friendlier outcomes during the fusing event. Hypalon insulation (A Dupont product that targeted electric locomotives in mines) is used on many fusible link replacement assemblies available at your local car parts stores . . . or in bulk wire on places like eBay. https://goo.gl/RH2eEY The material selected for a fusible link has little to do the loads presented by downstream appliances. The wire in fusible link is EXPECTED to burn . . . at many degrees above the insulation rating. Selection of material is about reduction of risk in the rare but catastrophic event. So, fusible link wire is simply used as a short extension of the feeder to be protected by splicing a short chunk (6-10 inches) onto the end of the feeder. Bob . . . Un impeachable logic: George Carlin asked, "If black boxes survive crashes, why don't they make the whole airplane out of that stuff?" ________________________________ Message 5 _____________________________________ Time: 08:54:20 AM PST US From: "Robert L. Nuckolls, III" Subject: Re: AeroElectric-List: Fusible Link Performance vs ANL Current Limiters At 07:52 AM 11/23/2022, you wrote: > > >I read a good review of this but cannot find it anywhere. Can >somebody lead me to it. The discussion regarded why the fusible >link was a better method than the ANL for electrical protection near >the alternators. 'Better' is not a very quantifiable term when applied out of context. The design goal calls for reduction of risk to certain conductors in the system against hazardous fault currents. How much current? In this case, a battery feed fault with a potential for hundreds of amps for an extended period of time. Precipitating event? Destruction of semiconductor devices in (1) output of alternator or (2) rectifier regulator. Options? Fuses, circuit breakers, current limiters, fusible link, etc. With respect to functionality, ANY of these would serve just fine. Design goals? Hmmmm . . . ease of installation, reduction of weight, minimum cost, attractive service life, or any combination of these. Fuses, current limiters, breakers have significant costs for procurement and installation. They may also feature threaded fasteners which adds to complexity and risk of loss of integrity due to environmental effects or deficiencies in craftsmanship. The lightest and lowest parts count approach is the fusible link. Tooling and skills are no greater than required for all other wires and terminals in the system. So unless constrained by other design goals favoring alternatives, I suggest that fusible links are the elegant solution to a VERY LOW RISK problem. Bob . . . Un impeachable logic: George Carlin asked, "If black boxes survive crashes, why don't they make the whole airplane out of that stuff?" ------------------------------------------------------------------------------------- Other Matronics Email List Services ------------------------------------------------------------------------------------- Post A New Message aeroelectric-list@matronics.com UN/SUBSCRIBE http://www.matronics.com/subscription List FAQ http://www.matronics.com/FAQ/AeroElectric-List.htm Web Forum Interface To Lists http://forums.matronics.com Matronics List Wiki http://wiki.matronics.com Full Archive Search Engine http://www.matronics.com/search 7-Day List Browse http://www.matronics.com/browse/aeroelectric-list Browse Digests http://www.matronics.com/digest/aeroelectric-list Browse Other Lists http://www.matronics.com/browse Live Online Chat! http://www.matronics.com/chat Archive Downloading http://www.matronics.com/archives Photo Share http://www.matronics.com/photoshare Other Email Lists http://www.matronics.com/emaillists Contributions http://www.matronics.com/contribution ------------------------------------------------------------------------------------- These Email List Services are sponsored solely by Matronics and through the generous Contributions of its members.