---------------------------------------------------------- AeroElectric-List Digest Archive --- Total Messages Posted Sun 08/23/15: 2 ---------------------------------------------------------- Today's Message Index: ---------------------- 1. 06:42 AM - Re: Re: Newbie with PM alternator feed question (Robert L. Nuckolls, III) 2. 07:14 AM - Re: Bending copper (bus) bar (JOHN TIPTON) ________________________________ Message 1 _____________________________________ Time: 06:42:16 AM PST US From: "Robert L. Nuckolls, III" Subject: Re: AeroElectric-List: Re: Newbie with PM alternator feed question At 09:24 PM 8/22/2015, you wrote: [quote="nuckolls.bob(at)aeroelect"] > > (1) Is dynamo current "self limiting" a characteristic of all 3 phase PM type alternators? (dynamos?) Would gladly eliminate those three 20 amp c/b's if not required! the PM alternators will self-destruct if presented with a hard short on their windings generated by failure of the rectifier=regulator. Use in-line fuses. One for the single phase machines, two for the three phase machines. These need no be crew- accessible. Do you mean these "need to be" or "need not be" crew accessible? Why? or why not? Do the Failure Mode Effects Analysis: What kind of failure would put these windings at risk? What is the probability that system functionality will be restored by resetting crew accessible circuit protection after suffering such a failure? Suggest you review the Fuses vs. Breakers discussions on the website . . . http://tinyurl.com/nmwyak5 . . . I think there's a pretty good case to be made for having NO crew accessible circuit protection for a constellation of reasons including. (1) Likelihood of restoring functionality after any righteous trip is zero. The fuse blew because something was broke . . . (2) Unlike the circuit protection in the TC aircraft, any discovery of a nuisance-trip condition in an OBAM aircraft can be quickly FIXED . . . (3) Crew accessible circuit protection has little up-side. It takes up panel space and it's a potential distraction from being pilot- in-the-air and saving mechanic-on-the-ground activities for later. (4) Paying homage to the federally mandated prohibition for unreachable protection of 'critical' hardware calls for doing your FMEA and making minimizing single-systems critical to comfortable termination of flight. In cases where this is simply not possible . . . like a one and only-one fuel injection system, then that system needs to be crafted with critical-item reliability like propeller bolts . . . ten to the minus bazillion failures per flight hour. Then, having its breaker/fuse accessible in the cockpit becomes immaterial. > (2) Was planning on a 40A ANL type fuse for the 10 ga wire from the relay to the primary bus. ANL's and their cousins are members of the genus "current limiter" . . . exceedingly robust and designed to protect fat-feeders from battery-fed, 1000A+ style faults. There are few instances in our size airplanes where the ANL-type devices are really well placed. The vast majority of protection goals are handily met with fast-fuses sized to avoid nuisance trips. I prefer the ANL-style device for automotive-style alternator b-leads because of their bolt-on style mounting and wire-termination that makes them a bit more convenient than any of the fuse holders but a well-considered fuse installation is never a 'bad' idea. What is the rated output of your altenrator? An inline maxi-fuse of next-step higher value would be fine and a lot less bulky. 30 Amp alternator, and I like the idea of the inline maxi-fuse versus the ANL because of the reduced size. I thought ANL type was preferred because of the longer response time and thus helped to avoid potential nuisance trips? It's true that current limiters simply do not nuisance trip but in this case, the maxi-fuse seems the more elegant solution. Thanks Bob! A real treat to be able to discuss topics with subject matter experts! My cluebag continues to fill... You're most welcome my friend . . . ________________________________ Message 2 _____________________________________ Time: 07:14:29 AM PST US Subject: AeroElectric-List: Re: Bending copper (bus) bar From: "JOHN TIPTON" The copper bar is 2mm (0.08inch) - so bend cold over a not too sharp (vice) edge Thanks Bob (and all) John Read this topic online here: http://forums.matronics.com/viewtopic.php?p=446290#446290 ------------------------------------------------------------------------------------- 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.