---------------------------------------------------------- AeroElectric-List Digest Archive --- Total Messages Posted Tue 08/02/11: 4 ---------------------------------------------------------- Today's Message Index: ---------------------- 1. 06:46 AM - Alternator Contactor (Dennis Ramsey) 2. 07:55 AM - Re: Alternator Contactor (Robert L. Nuckolls, III) 3. 07:58 AM - Re: Permanet Splicing RG400 (Robert L. Nuckolls, III) 4. 08:21 AM - Re: Permanet Splicing RG400 (Robert L. Nuckolls, III) ________________________________ Message 1 _____________________________________ Time: 06:46:59 AM PST US Subject: AeroElectric-List: Alternator Contactor From: Dennis Ramsey At Oshkosh, I sat in on an "electrical system design" forum. The presenter at the end presented there little box that they sell with all the contactors, fuses, and overvoltage protection in it. One of the contactors was an "alternator contactor". So I decided to stop by their booth and ask questions. Here is our conversation: Why do you need an alternator contactor? The field is going to be 5 amps or less, you can use a switch for that. "Our contactor is on the alternator output". Why do you need that, once you kill the field its going to shut down the alternator? "You can still have a run away alternator with the field shut off" Hmmm. So my question is, can you really have a runaway alternator with the field shut off? My B&C controller is focused on the field juice, and just wondering how much risk I have of an issue. ________________________________ Message 2 _____________________________________ Time: 07:55:48 AM PST US From: "Robert L. Nuckolls, III" Subject: Re: AeroElectric-List: Alternator Contactor At 08:43 AM 8/2/2011, you wrote: At Oshkosh, I sat in on an "electrical system design" forum. The presenter at the end presented there little box that they sell with all the contactors, fuses, and overvoltage protection in it. One of the contactors was an "alternator contactor". So I decided to stop by their booth and ask questions. Here is our conversation: Why do you need an alternator contactor? The field is going to be 5 amps or less, you can use a switch for that. "Our contactor is on the alternator output". Why do you need that, once you kill the field its going to shut down the alternator? "You can still have a run away alternator with the field shut off" Hmmm. There is a exceedingly tiny chance that the alternator designer didn't do his homework and the alternator develops and internal short from field lead to some hot conductor within. Saw this happen one time at Mooney . . . they experienced an un-controllable runaway on a prototype alternator they were testing. So my question is, can you really have a runaway alternator with the field shut off? My B&C controller is focused on the field juice, and just wondering how much risk I have of an issue. Chances of this happening in real life are zero. Who is this organization? I'll send them a couple of books. Bob . . . ________________________________ Message 3 _____________________________________ Time: 07:58:05 AM PST US From: "Robert L. Nuckolls, III" Subject: Re: AeroElectric-List: Permanet Splicing RG400 At 06:45 PM 8/1/2011, you wrote: > > > Wow, thank you Bob for that detailed explanation. Now that I have > the "how" I have to decide if it's worth it. > >Just checked on the price of RG400, and it seems to be around >$2.50/ft. Egads! I swear that is 2x more than what i paid for my >original order just a year ago!? That's $33 savings if i can splice >the coax myself. :D Yeah, that stuff has gotten expensive . . . but anything with copper in it has been given an excuse to jump in price . . . even if copper is the least expensive commodity in the product. I'll poke around my surplus/used sources and see if I can dig up some 400 at more attractive prices. But for our purposes, the splice I described is pretty easy to do and has no observable impact on performance. For that matter, you could consider RG58 for anything except GPS and Transponders. That coax performed well for decades. Bob . . . ________________________________ Message 4 _____________________________________ Time: 08:21:52 AM PST US From: "Robert L. Nuckolls, III" Subject: Re: AeroElectric-List: Permanet Splicing RG400 > I'll poke around my surplus/used sources and see > if I can dig up some 400 at more attractive prices. Don't forget eBay. For example, if your run is 9' or less, you can buy something like this: http://tinyurl.com/4x3a3na which is pre-assembled with connectors. But it's $10 with free shipping. Cut the connectors off and install your own. Also, consider the modern Poly coax LMR400. It's larger in diameter but connectors for it are easy to get. It's losses at the high frequencies are on par with the fancier stuff and a whole lot cheaper. If the size is not a turn off for your particular application: http://tinyurl.com/3k86rvm Bob . . . ------------------------------------------------------------------------------------- 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.