---------------------------------------------------------- AeroElectric-List Digest Archive --- Total Messages Posted Wed 10/28/09: 2 ---------------------------------------------------------- Today's Message Index: ---------------------- 1. 09:10 AM - Re: What makes diode get warm (Eric Schlanser) 2. 06:16 PM - Re: What makes diode get warm (Robert L. Nuckolls, III) ________________________________ Message 1 _____________________________________ Time: 09:10:37 AM PST US From: Eric Schlanser Subject: RE: AeroElectric-List: What makes diode get warm - - Which Z diagram would it look like without the E buss? - Eric Time: 01:18:06 PM PST US From: "plaurence" Subject: RE: AeroElectric-List: What makes diode get warm Mike, If you have a second alternator, and using B&C's regulators, you really don't need the E buss. Peter //mail.yahoo.com ________________________________ Message 2 _____________________________________ Time: 06:16:16 PM PST US From: "Robert L. Nuckolls, III" Subject: Re: AeroElectric-List: What makes diode get warm At 01:06 PM 10/27/2009, you wrote: > >I have the B&C diode on the heat sink (smaller one). I was bench >testing things to make sure the flow was correct, I just took the >breaker panel and hooked up power to the main bus then the >E-bus. The diode did not heat up at all, the flow was in the >correct direction. I hooked up power to the E-bus and the diode did >prevent current to the main bus, the main would only read 0.4 volts >which I assume is normal. With this set up the diode again did not >heat up. I then hooked up one of the 50W MR16 landing light bulbs >to a CB thinking maybe I needed a load, again the diode did not heat up. Perhaps it did . . . just not enough for you to perceive it by feeling. Was your e-bus alternate feed switch OPEN during the test. If so, then the normal feed path diode would have been carrying all the e-bus loads and it would warm up. Why a diode on a heat-sink? How large are your anticipated e-bus loads? The diode-bridge rectifier mounted on a metal airframe surface is good for 10+ amps. Schottky diodes are a bit better yet. I've tested this guy to 20A http://aeroelectric.com/Catalog/AEC/9001/IM9001-700A.pdf when mounted on a surface .062" thick with no additional heat sinking. >So what make the diode heat up, is it more load on the system or is >it when there is power going to both buses, as when you have the >master on and the E-bus alternate feed on at the same time. If the alternate feedpath switch is closed, then the normal feed-path is bypassed and the diode will carry no current . . . nor will it warm up. >With both buses getting power the diode is getting power from both >sides. I hear you can fly around this way but not sure I will, my >plan now is the have my E-bus alternate feed under a guarded switch >that stay off when guarded. When the E-bus gets power from the main >via the diode there is a slight voltage drop . . . and is the time when it dissipates a few watts of power and will warm up. The degree of temperature rise depends on mass and configuration of the heat sink. > . . . the the E-bus alternate feed was on the flow from the > battery to the E-bus would win out and supply the E-bus since the > voltage from the main is lower. . . . The main bus voltage isn't 'lower' but a voltage drop in the normal feed path becomes insignificant when the alternate feed path bypasses the diode. > So would this meeting of currents be what heats up the diode? As > far as flying around with the E-bus alternate feed on I don't see > the need with my system I have a standby alternator. How about being able to fire up the comm radio for ATIS and clearance delivery before starting the engine? THIS is the time that the alternate feed path is also tested. > Once I am using standby power then I might consider turning the > alternate feed on for automatic switching in case the standby > alternator then quit. Thank for the help. The purpose of the alternate feed path switch is to allow battery only operations without having a battery contactor closed. You didn't mention which, if any of the Z-figures you based your system. If you're running Z-12, then having the switch "pre-closed" offers no degree of automation. I'll suggest you do a site search on "e-bus" at aeroelectric.com and review the conversation about how the e-bus came into being and what it's all about. There's about 30 hits that should offer some insight. Over the past 15 or so years, folks have tended to overload the e-bus and/or lost track of the e-bus design goals. It may well be that your design goals are served by not having an e-bus. It's a strong probability that your normal feed-path diode assembly is oversized. 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.