X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Received: from web81207.mail.yahoo.com ([206.190.37.180] verified) by logan.com (CommuniGate Pro SMTP 5.0c2) with SMTP id 718636 for flyrotary@lancaironline.net; Sun, 11 Sep 2005 17:17:45 -0400 Received-SPF: none receiver=logan.com; client-ip=206.190.37.180; envelope-from=mike.lafleur@sbcglobal.net Received: (qmail 51520 invoked by uid 60001); 11 Sep 2005 21:17:01 -0000 Message-ID: <20050911211701.51518.qmail@web81207.mail.yahoo.com> Received: from [69.221.76.176] by web81207.mail.yahoo.com via HTTP; Sun, 11 Sep 2005 14:17:01 PDT Date: Sun, 11 Sep 2005 14:17:01 -0700 (PDT) From: Michael LaFleur Subject: Re: [FlyRotary] Re: Overvoltage control (help Ed A) To: Rotary motors in aircraft In-Reply-To: MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Transfer-Encoding: 8bit Jim, When I said "Don't you?", I meant the group. Not you specifically. I know you know better. :-) Mike --- Jim Sower wrote: > <...All charging systems should have protection for > this. Don't you? ...> > Yes. I've described it in some detail, about three > times so far, on > this thread. Now, the scenario of a "... load dump > where the battery is > disconnected ..." (and presumably all of the > aircraft systems (can't see > 100V with any load AT ALL - if then)) happening > simultaneously with > regulator failure to full output ... would be ... > ??? > > PVORT for three days now :o) ... Jim S. > > > Michael LaFleur wrote: > > >In the case of a load dump, where the battery is > >disconnected for a charging circuit, you will see > more > >than 100 volts. > > > >The alternator, being low impedance will cause > large > >positive transients. Simultabeously, the collapsing > >field will cause negative field decay transients. > >These can and will be in excess of 100 volts. All > >charging systems should have protection for this. > >Don't you? > > > >--- Jim Sower wrote: > > > > > > > >>Finn Lassen wrote: > >> > >> > >> > >>>I think the +100 volts statement relates to no > >>> > >>> > >>battery load. Have you > >> > >> > >>>/anyone actually /seen/ that happen? I guess if > >>> > >>> > >>the electrical system > >> > >> > >>>was designed so that a contactor could disconnect > >>> > >>> > >>the battery from the > >> > >> > >>>load circuits and the load circuits (avionics) > >>> > >>> > >>still be connected to > >> > >> > >>>the alternator you would have a situation where > >>> > >>> > >>you could wave your > >> > >> > >>>avionics goodbye. > >>>Perhaps. But that wouldn't be very clever. > >>> > >>> > >>Anyone who designed his > >> > >> > >>>system to protect his avionics from a Battery > over > >>> > >>> > >>voltage and ignored > >> > >> > >>>the Alternator deserves whatever happens. > >>>Let's say on top of that that one (or all) of the > >>> > >>> > >>three retifiers > >> > >> > >>>shorted out too, you'd have 100 volts A/C into > >>> > >>> > >>your avionics. Not a > >> > >> > >>>pretty picture. (I've seen Zener diodes short out > >>> > >>> > >>regularily due to > >> > >> > >>>overload/voltage; rectifier diodes usually fail > >>> > >>> > >>open - but not > >> > >> > >>>always). We're stretching a bit here aren't we? > > >>> > >>> > >>Back to the 100 V > >> > >> > >>>that we've already agreed can't happen, shorted > >>> > >>> > >>diodes causing AC > >> > >> > >>>(which I'm not at all sure can happen), all three > >>> > >>> > >>rectifiers (that's > >> > >> > >>>all SIX diodes shorting at the same time (none of > >>> > >>> > >>them failing open > >> > >> > >>>which is more common), zener failing, etc. If a > >>> > >>> > >>diode fails every > >> > >> > >>>1000 hrs, the whole bank failing would happen > >>> > >>> > >>every 1000^6 hours. > >> > >> > >>>That's a one with TWENTY ONE zeros behind it. > >>> > >>> > >>I think I can live with that ... Jim S. > >> > >> > >> > >>>Finn > >>> > >>>Jim Sower wrote: > >>> > >>> > >>> > >>>><... the alternator is capable of producing over > >>>> > >>>> > >>100 volts ...> > >> > >> > >>>>I don't think so ... > >>>>... > >>>>Bottom line, with the regulator failed (or > >>>> > >>>> > >>bypassed) to send full B+ > >> > >> > >>>>voltage to the field, the charging voltage never > >>>> > >>>> > >>exceed 18V in my > >> > >> > >>>>experience. > >>>> > >>>> > >>> > >>> > >>>-- > >>>Homepage: http://www.flyrotary.com/ > >>>Archive and UnSub: > >>> > >>> > >>http://mail.lancaironline.net/lists/flyrotary/ > >> > >> > >>> > >>> > > > > > >-- > >Homepage: http://www.flyrotary.com/ > >Archive and UnSub: > http://mail.lancaironline.net/lists/flyrotary/ > > > > > === message truncated ===