---------------------------------------------------------- AeroElectric-List Digest Archive --- Total Messages Posted Thu 05/08/14: 7 ---------------------------------------------------------- Today's Message Index: ---------------------- 1. 04:11 AM - Fusable link (JOHN TIPTON) 2. 04:13 AM - Re: Fusable link (JOHN TIPTON) 3. 05:40 AM - Re: Fusable link (Robert L. Nuckolls, III) 4. 05:58 AM - FYI - LMR195 coax (Robert L. Nuckolls, III) 5. 11:22 AM - Re: Fusable link (JOHN TIPTON) 6. 05:36 PM - Re: Re: Fusable link (Robert L. Nuckolls, III) 7. 08:17 PM - Re: Re: Fusable link (Jeff Luckey) ________________________________ Message 1 _____________________________________ Time: 04:11:23 AM PST US Subject: AeroElectric-List: Fusable link From: "JOHN TIPTON" Hi Guys (Bob) I see that Z11 is using a fuse block as opposed the CBs (no problem there), can you tell me why the feed to the 5a CB has a fuse able link, why not use a fuse in the distribution fuse block Best regards John Read this topic online here: http://forums.matronics.com/viewtopic.php?p=422991#422991 ________________________________ Message 2 _____________________________________ Time: 04:13:01 AM PST US Subject: AeroElectric-List: Re: Fusable link From: "JOHN TIPTON" Ps: the 5amp CB did relate to the alternator feed circuit John Read this topic online here: http://forums.matronics.com/viewtopic.php?p=422992#422992 ________________________________ Message 3 _____________________________________ Time: 05:40:11 AM PST US From: "Robert L. Nuckolls, III" Subject: Re: AeroElectric-List: Fusable link At 06:09 AM 5/8/2014, you wrote: Hi Guys (Bob) I see that Z11 is using a fuse block as opposed the CBs (no problem there), can you tell me why the feed to the 5a CB has a fuse able link, why not use a fuse in the distribution fuse block Best regards John The length of wire from fuse block feeder terminal out to the circuit breaker is an EXTENSION of the bus. In larger aircraft the bus feeders will sometimes be protected by a VERY robust fusible device like the ANN/ANL series of "current limiters" . . . http://aeroelectric.com/Mfgr_Data/Fuses_and_Current_Limiters/Bu http://tinyurl.com/lrjm5y3 http://tinyurl.com/k7o3l3q Note that these devices, while 'rated' at some value like 100A, they will CARRY 2x their rated current almost indefinitely. At the same time, when subjected to a hard fault of 5 to 10x rated current, they open in tens of milliseconds. Legacy design goals for aircraft suggest that this extension of the bus up to your panel mounted circuit breaker needs a 'current limiter' but not like the devices cited above. It's much smaller and designed to protect the longer run of wire to the breaker. Protection with a response many times longer than the breaker it feeds. This question came up on the List a few years ago . . . Q: Drawing Z24 shows how to add an OV protection module for an internally regulated power supply. It requires the use of a 5A circuit breaker and also of a fuselink attached to the main connection of the main bus. The question: Can we replace the fuselink by using one of the outputs on the main bus protected by a larger fuse (say 15amps)? I would like for sure the breaker to let go before the fuse. A: Some 5A breakers will open a 15A fuse. Fuses are MUCH faster than breakers. This is why I prefer the fusible link The risks of positioning fuses upstream of breakers is illustrated in the accident case I chronicled here http://tinyurl.com/msfmldj and demonstrated here http://tinyurl.com/ppdv5fg The automotive world has used fusible links in this capacity for decades and they've served well in the capacity of mini-limiters. Bob . . . ________________________________ Message 4 _____________________________________ Time: 05:58:28 AM PST US From: "Robert L. Nuckolls, III" Subject: AeroElectric-List: FYI - LMR195 coax I installed a new antenna on the roof yesterday and wired it to the radio with LMR195 coax. While this stuff has appealing performance specs, it is NOT a drop-in-replacement for the legacy coaxes that feature one or more braided outer conductors. Emacs! Unlike the RG142 illustrated above I found that the braid wires on this coax are very small and few. The coax's shield performance is bounded by the foil shield. The outer braid is just a means by which connection can be made to the foil and is relatively fragile compared to the two heavy layers of braid in RG142/400 The installer must take extra care in the 3rd cut and removal of the outer jacket so as not to damage the braid. Further, the 2nd cut designed to remove the shield from a stub of center insulation is problematic. Again, depth of cut and subsequent removal of the foil shield (tightly bonded to the insulation) is tricky. I got my connectors installed and the feed line performs as expected . . . but I would caution builders to work with some scraps of this coax and some 'training connectors' to refine their technique. I'll put LMR195 coax termination on the list of comic books to be crafted for the website. Bob . . . ________________________________ Message 5 _____________________________________ Time: 11:22:42 AM PST US Subject: AeroElectric-List: Re: Fusable link From: "JOHN TIPTON" So a ANL current limiter off the main battery protecting the whole system would not be a bad idea ? John Read this topic online here: http://forums.matronics.com/viewtopic.php?p=423017#423017 ________________________________ Message 6 _____________________________________ Time: 05:36:22 PM PST US From: "Robert L. Nuckolls, III" Subject: Re: AeroElectric-List: Re: Fusable link At 01:21 PM 5/8/2014, you wrote: > > >So a ANL current limiter off the main battery protecting the whole >system would not be a bad idea ? Not a bad idea . . . but not a good one either. Current limiters have value for fault isolation in complex bus structures . . . which are generally not found in Part 23 airplanes. The fat wires between battery, main bus and starter terminal are usually of such robustness that any fault to ground would be more likely to burn a hole in fault location as opposed to opening any limiter in the path. Single light TC aircraft have never been fitted with such protection that I know of. Bob . . . ________________________________ Message 7 _____________________________________ Time: 08:17:37 PM PST US From: Jeff Luckey Subject: Re: AeroElectric-List: Re: Fusable link =0A=0AFrom: "Robert L. Nuckolls, III" =0ATo: aeroelectric-list@matronics.com =0ASent: Thursday, May 8, 2014 5:32 PM=0AS ubject: Re: AeroElectric-List: Re: Fusable link=0A =0A=0A--> AeroElectric-L ist message posted by: "Robert L. Nuckolls, III" =0A=0AAt 01:21 PM 5/8/2014, you wrote:=0A>--> AeroElectric-List messag e posted by: "JOHN TIPTON" =0A>=0A>=0A>So a ANL c urrent limiter off the main battery protecting the whole =0A>system would n ot be a bad idea ?=0A=0A- Not a bad idea . . . but not a good one either . Current=0A- limiters have value for fault isolation in complex bus=0A - structures . . . which are generally not found in Part=0A- 23 airpl anes.=0A=0A- The fat wires between battery, main bus and starter=0A- terminal are usually of such robustness that any=0A- fault to ground wou ld be more likely to burn a hole=0A- in fault location as opposed to ope ning any limiter=0A- in the path.=0A=0ANot sure what that means... ??? - =0A=0AIf it is "robust" wouldn't it carry enough current to blow the li miter?=0AAre you suggesting that "welding/burning" aluminum does not draw a lot of current?=0AHave you ever tested that hypothesis?=0A=0AEven if some of the above is true, a current limiter still could provide some protection =0Afrom a "hard" fault, could it not?=0A=0A-Jeff=0A=0A=0A- Single light TC aircraft have never been fitted with=0A- such protection that I know - - - - - - - - - - - - - -Matt Dralle, List Adm ===== ------------------------------------------------------------------------------------- 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.