---------------------------------------------------------- AeroElectric-List Digest Archive --- Total Messages Posted Mon 08/29/22: 2 ---------------------------------------------------------- Today's Message Index: ---------------------- 1. 12:46 PM - Re: Re: flyback diode across fuel pump (Robert L. Nuckolls, III) 2. 12:46 PM - Re: Re: 30A PM alternator and Z101? (Robert L. Nuckolls, III) ________________________________ Message 1 _____________________________________ Time: 12:46:19 PM PST US From: "Robert L. Nuckolls, III" Subject: Re: AeroElectric-List: Re: flyback diode across fuel pump >Hi Bob, > >The VAF thread started as =9Clocal ground or >forest of tabs for fuel pump ground?=9D, EFI >fuel pump, and drifted at post 9 to someone >recommending a diode across the pump motor to >protect the pump switch. I had never heard of this so I asked here on AEL. > >https://vansairforce.net/community/showpost.php?p=1629894&postcount=9 > >-------- >John Bright, RV-6A, at FWF, O-360 Good show 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 2 _____________________________________ Time: 12:46:19 PM PST US From: "Robert L. Nuckolls, III" Subject: Re: AeroElectric-List: Re: 30A PM alternator and Z101? >Hi Bob, > >I have communicated by email and telephone with Bill Judge of Monkworkz. > >I passed along your offer of doing performance testing and >evaluation of the spike that trips OV protection if the B lead is >disconnected under load. At present Bill plans to keep testing in house. I am in contact with Bill . . . we're discussing ways in which I might be of service. Why would the b-lead contactor be opened under load? Sounds like the rather sophisticated ov management system described in the Monkworkz literature is being presented with the equivalent of a load-dump event. We're not privy to the functional dynamics of the sensor. MOST legacy ov protection devices are too 'twitchy'. The very first project I did for Electro-Mech back about 1975 was a solid state replacement for the RBM controls RBM138-1 electro-mechanical ov relay http://aeroelectric.com/Pictures/Relays/RBM138-1_A.jpg http://aeroelectric.com/Pictures/Relays/RBM138-1_B.jpg This device was widely used in Cessna Prospect Plant airplanes (310, 320). My replacement was solid state sensing, 1/4th the weight and volume and per customer's wishes, would trip in about 50 mS responding to a step from 28 to 32 volts. Much faster than suggested by Mil-STD-704 description for DC system performance. See figure 14 of http://aeroelectric.com/Reference_Docs/Mil-Std-704/704_excerpts.pdf Design rules tell us that a 32 volt transient in a 28v system can be EXPECTED to last up to 1 second. DO-160 qualification testing requires us to DEMONSTRATE an ability to stand off 40V for one second in 28v system; 20V in a 14V system. I've designed many ov management devices to customer procurement specs that were MUCH faster. Today, I would design to tolerate a bus in excess of 16 volts for 500 milliseconds. If voltage drops below 16 volts, the timer resets and starts awaits a new trip decision if the voltage goes back up. This protocol is 99.999% immune to all common transient excursions including alternator load-dump . . . but will perform as needed to mitigate an alternator runaway event. I'll inquire of Bill what his ov detection/ reaction philosophy is next time we talk. 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.