X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Received: from relay03.roc.ny.frontiernet.net ([66.133.182.166] verified) by logan.com (CommuniGate Pro SMTP 5.0c2) with ESMTP id 717992 for flyrotary@lancaironline.net; Sat, 10 Sep 2005 20:42:50 -0400 Received-SPF: pass receiver=logan.com; client-ip=66.133.182.166; envelope-from=canarder@frontiernet.net Received: from filter04.roc.ny.frontiernet.net (filter04.roc.ny.frontiernet.net [66.133.183.71]) by relay03.roc.ny.frontiernet.net (Postfix) with ESMTP id 444693581B3 for ; Sun, 11 Sep 2005 00:42:06 +0000 (UTC) Received: from relay03.roc.ny.frontiernet.net ([66.133.182.166]) by filter04.roc.ny.frontiernet.net (filter04.roc.ny.frontiernet.net [66.133.183.71]) (amavisd-new, port 10024) with LMTP id 29643-03-42 for ; Sun, 11 Sep 2005 00:42:06 +0000 (UTC) Received: from [127.0.0.1] (unknown [70.98.128.118]) by relay03.roc.ny.frontiernet.net (Postfix) with ESMTP id AC3AA358147 for ; Sun, 11 Sep 2005 00:42:03 +0000 (UTC) Message-ID: <43237D52.9000302@frontiernet.net> Date: Sat, 10 Sep 2005 19:41:54 -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: multipart/alternative; boundary="------------060002030304050109020308" 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 This is a multi-part message in MIME format. --------------060002030304050109020308 Content-Type: text/plain; charset=us-ascii; format=flowed Content-Transfer-Encoding: 7bit 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/ > > --------------060002030304050109020308 Content-Type: text/html; charset=us-ascii Content-Transfer-Encoding: 7bit

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/

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