X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Received: from relay01.roc.ny.frontiernet.net ([66.133.182.164] verified) by logan.com (CommuniGate Pro SMTP 5.0c2) with ESMTP id 718135 for flyrotary@lancaironline.net; Sun, 11 Sep 2005 01:53:18 -0400 Received-SPF: pass receiver=logan.com; client-ip=66.133.182.164; envelope-from=canarder@frontiernet.net Received: from filter04.roc.ny.frontiernet.net (filter04.roc.ny.frontiernet.net [66.133.183.71]) by relay01.roc.ny.frontiernet.net (Postfix) with ESMTP id 7F1FF364186 for ; Sun, 11 Sep 2005 05:52:33 +0000 (UTC) Received: from relay01.roc.ny.frontiernet.net ([66.133.182.164]) by filter04.roc.ny.frontiernet.net (filter04.roc.ny.frontiernet.net [66.133.183.71]) (amavisd-new, port 10024) with LMTP id 24631-06-11 for ; Sun, 11 Sep 2005 05:52:33 +0000 (UTC) Received: from [127.0.0.1] (unknown [70.98.128.118]) by relay01.roc.ny.frontiernet.net (Postfix) with ESMTP id 0309C364177 for ; Sun, 11 Sep 2005 05:52:32 +0000 (UTC) Message-ID: <4323C617.1060401@frontiernet.net> Date: Sun, 11 Sep 2005 00:52:23 -0500 From: Jim Sower User-Agent: Mozilla/5.0 (Windows; U; Windows NT 5.1; en-US; rv:1.7) Gecko/20040514 X-Accept-Language: en-us, en MIME-Version: 1.0 To: Rotary motors in aircraft Subject: Re: [FlyRotary] Re: Overvoltage control (help Ed A) References: In-Reply-To: Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit X-Antivirus: avast! (VPS 0536-5, 09/09/2005), Outbound message X-Antivirus-Status: Clean X-Virus-Scanned: by amavisd-new-2.3.2 (20050629) at filter04.roc.ny.frontiernet.net <...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/ > > > >