X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Sender: To: lml@lancaironline.net Date: Thu, 15 Jun 2006 00:54:06 -0400 Message-ID: X-Original-Return-Path: Received: from smtp103.sbc.mail.mud.yahoo.com ([68.142.198.202] verified) by logan.com (CommuniGate Pro SMTP 5.0.9) with SMTP id 1154214 for lml@lancaironline.net; Wed, 14 Jun 2006 12:30:46 -0400 Received-SPF: none receiver=logan.com; client-ip=68.142.198.202; envelope-from=elippse@sbcglobal.net Received: (qmail 82045 invoked from network); 14 Jun 2006 16:03:19 -0000 Received: from unknown (HELO Computerroom) (elippse@sbcglobal.net@75.15.131.168 with login) by smtp103.sbc.mail.mud.yahoo.com with SMTP; 14 Jun 2006 16:03:18 -0000 X-Original-Message-ID: <000601c68fcc$0eba7980$a8830f4b@Computerroom> From: "Paul Lipps" X-Original-To: "Marv Kaye" Subject: Avionics renewal justification X-Original-Date: Wed, 14 Jun 2006 09:03:18 -0700 MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="----=_NextPart_000_0003_01C68F91.60AE66B0" X-Priority: 3 X-MSMail-Priority: Normal X-Mailer: Microsoft Outlook Express 6.00.2900.2869 X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2900.2869 This is a multi-part message in MIME format. ------=_NextPart_000_0003_01C68F91.60AE66B0 Content-Type: text/plain; charset="Windows-1252" Content-Transfer-Encoding: quoted-printable In light of some recent events, I'd like to post this following means of = justifying renewal of your avionics: To those of you who have a circuit breaker between your alternator's = output and your main buss, here's a wonderful way to fry your present = old avionics so you can replace them with new ones. This is a real help = in justifying new avionics to your significant other! If your alternator = field-circuit-breaker is connected to your main buss, then if your = alternator breaker opens, either through an overload or manually, your = main buss voltage will drop. The regulator, sensing this, will increase = the alternator's field current. 'Course, there is no load on the = alternator, so its voltage will rise. Eventually, in a few milliseconds, = the regulator will be pumping maximum current through the field. Since = we drive our alternators at 7000-9000 rpm, the alternator will put out = well in excess of 100 volts. Closing through the alternator-breaker will = put this high voltage on your buss. Your over-voltage protector, if = present, will crowbar and short the field supply, opening its breaker, = but by the time the field collapses, the damage will have been done. = Here's two things you can do to prevent this and keep your old avionics. = Any time your alternator breaker opens, pull your field breaker before = restoring the alternator's breaker. If you don't want to depend on your = memory in a time of stress, rewire your field circuit breaker to the = alternator side of the alternator breaker. That way the alternator's = field will serve as the alternator load and the regulator will be = sensing the alternator output, thus keeping it in regulation. If you = don't think this scenario could actually take place, I challenge you to = do this test on your plane at cruise rpm with lots of avionics load and = prove me wrong! Maybe you shouldn't try this while in heavy IFR! By the = way; putting one of those load-dump transient MOV (metal oxide varistor) = protectors on the output of the alternator will not protect against = this. Their power and current ratings are very high, but only for very = short transients. One or several seconds do not a short transient make! = Pumping hundreds or thousands of Watts through them for more than a few = milliseconds will turn them into slag! ------=_NextPart_000_0003_01C68F91.60AE66B0 Content-Type: text/html; charset="Windows-1252" Content-Transfer-Encoding: quoted-printable
In light of some recent events, I'd like to post = this=20 following means of justifying renewal of your = avionics:
    To those of you who have a = circuit=20 breaker between your alternator's output and your main buss, here's a = wonderful=20 way to fry your present old avionics so you can replace them with new = ones. This=20 is a real help in justifying new avionics to your significant other! If = your=20 alternator field-circuit-breaker is connected to your main buss, then if = your=20 alternator breaker opens, either through an overload or manually, your = main buss=20 voltage will drop. The regulator, sensing this, will increase the = alternator's=20 field current. 'Course, there is no load on the alternator, so its = voltage will=20 rise. Eventually, in a few milliseconds, the regulator will be pumping = maximum=20 current through the field. Since we drive our alternators at 7000-9000 = rpm, the=20 alternator will put out well in excess of 100 volts. Closing through the = alternator-breaker will put this high voltage on your buss. Your = over-voltage=20 protector, if present, will crowbar and short the field supply, opening = its=20 breaker, but by the time the field collapses, the damage will have = been=20 done. Here's two things you can do to prevent this and keep your old = avionics.=20 Any time your alternator breaker opens, pull your field breaker before = restoring=20 the alternator's breaker. If you don't want to depend on your memory in = a time=20 of stress, rewire your field circuit breaker to the alternator side of = the=20 alternator breaker. That way the alternator's field will serve as the = alternator=20 load and the regulator will be sensing the alternator output, thus = keeping it in=20 regulation. If you don't think this scenario could actually take place, = I=20 challenge you to do this test on your plane at cruise rpm with lots of = avionics=20 load and prove me wrong! Maybe you shouldn't try this while in heavy=20 IFR! By the way; putting one of those load-dump transient MOV = (metal oxide=20 varistor) protectors on the output of the alternator will not = protect=20 against this. Their power and current ratings are very high, but = only for=20 very short transients. One or several seconds do not a = short transient=20 make! Pumping hundreds or thousands of Watts through them for more than = a few=20 milliseconds will turn them into slag! 
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