---------------------------------------------------------- AeroElectric-List Digest Archive --- Total Messages Posted Sun 03/29/15: 3 ---------------------------------------------------------- Today's Message Index: ---------------------- 1. 01:12 PM - Re: Relays (Robert L. Nuckolls, III) 2. 07:15 PM - Re: Relays (user9253) 3. 08:06 PM - Re: Re: Relays (Robert L. Nuckolls, III) ________________________________ Message 1 _____________________________________ Time: 01:12:48 PM PST US From: "Robert L. Nuckolls, III" Subject: Re: AeroElectric-List: Relays Here's some additional materials that go toward understanding 'contact science' . . . whether you're talking about switches or relays. Relays are just remotely operated switches. The CONTACTS share the same physics. http://tinyurl.com/nda9su5 Here's a couple of documents produced by one of the 'granddaddies' of switch and relay business http://tinyurl.com/ngnjglx http://tinyurl.com/nenvxrx Bob . . . Bob . . . ________________________________ Message 2 _____________________________________ Time: 07:15:25 PM PST US Subject: AeroElectric-List: Re: Relays From: "user9253" Quote from the Tyco paper, > Some relay users connect a diode across the inductive load to prevent counter-voltage from reaching the contacts. . . . While this is an acceptable method of protecting the contacts, it does result in lengthened hold-up time of the inductive load. So Bob, this does not contradict the results of your lab experiments (If I remember your posts correctly.) that demonstrate that arc suppression diodes delay opening of relay contacts, but do not cause the contacts to open slower once they start opening. A hold-up delay of less than one second is of no consequence in most amateur built aircraft. Joe -------- Joe Gores Read this topic online here: http://forums.matronics.com/viewtopic.php?p=440026#440026 ________________________________ Message 3 _____________________________________ Time: 08:06:05 PM PST US From: "Robert L. Nuckolls, III" Subject: Re: AeroElectric-List: Re: Relays At 21:13 2015-03-29, you wrote: > >Quote from the Tyco paper, > > Some relay users connect a diode across the inductive load to > prevent counter-voltage from reaching the contacts. . . . While > this is an acceptable method of protecting the contacts, it does > result in lengthened hold-up time of the inductive load. > >So Bob, this does not contradict the results of your lab experiments >(If I remember your posts correctly.) that demonstrate that arc >suppression diodes delay opening of relay contacts, but do not cause >the contacts to open slower once they start opening. A hold-up >delay of less than one second is of no consequence in most amateur >built aircraft. Good eye!!!! There was a lengthy discussion here on the list some years ago. About that same time, I was deeply immersed in some failure studies of relays on the roll trim system on the Beechjet. Even the folks who supplied the relays couldn't figure out what was going on . . . and it took me several years of sifting the reports and doing the science to identify and demonstrate the root cause. Here's 'the meat' of a report I crafted for RAC. http://tinyurl.com/pstsggm Turns out that primary stresser for causing very lightly loaded contacts to stick was an effect not discussed or warned against in any relay applications document I could find. Some years earlier, I was able to explore and confirm that the form of coil suppression on a relay had very little effect on the contact spreading velocity once the relay started to open. Diodes have a PROFOUND effect on drop out delay . . . but that forcing function has almost no effect on spreading velocity . . . hence tendency to arc. Once the armature comes off the electro-magnet pole-piece, the AIR GAP produced therein weakens the magnetic force far more rapidly than the diode can retard it's decay. http://tinyurl.com/qgkgo88 It's tar-bucket stepped into by many authors in the 'relay arts'. A document from Tyco was often cited here on the list where one ASSUMED that because the diode retards drop-out response . . . if just logically followed that the contacts must spread more slowly as well. http://tinyurl.com/ndc6cvl Now, if we were using relays in systems wire TIMING was critical . . . the extended drop-out delay might cause other problems . . . but not reduced contact life due to aggravated arcing. 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.