X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Received: from cdptpa-omtalb.mail.rr.com ([75.180.132.120] verified) by logan.com (CommuniGate Pro SMTP 5.2.2) with ESMTP id 2876313 for flyrotary@lancaironline.net; Mon, 28 Apr 2008 23:05:01 -0400 Received-SPF: pass receiver=logan.com; client-ip=75.180.132.120; envelope-from=echristley@nc.rr.com Received: from [192.168.0.19] (really [66.57.38.121]) by cdptpa-omta05.mail.rr.com with ESMTP id <20080429030421.CRMW720.cdptpa-omta05.mail.rr.com@[192.168.0.19]> for ; Tue, 29 Apr 2008 03:04:21 +0000 Message-ID: <48169076.4020406@nc.rr.com> Date: Mon, 28 Apr 2008 23:05:26 -0400 From: Ernest Christley User-Agent: Thunderbird 2.0.0.12 (X11/20080227) MIME-Version: 1.0 To: Rotary motors in aircraft Subject: Re: [FlyRotary] Re: the Kubota dynamo References: In-Reply-To: Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit SHIPCHIEF@aol.com wrote: > For this reason, I would think the permanent magnet altrnator would be used > all the time at capacity, and it would be sized to meet the minimum power > requirement of the aircraft. The Field Current controlled alternator would carry > all excess loads like recharging the start battery, and auxilliary equipment, > say the full avionics suite and entertainment air conditioning what have you. > Scott > It's a tempting idea, but I don't think it will work. The resistor to ground method (and the big wonkin' zener diode acts as a resistor), forces the generator to push 14.5V. The magnets have a limited amount of push in them, so they can only produce a certain amount of current at 14.5V. The stator wires are sized to handle more than this set amount of current. If you size the generator to handle most of the ships load, the generator will happily burn itself up in an effort to reach that 14.5V. Instead of the magnets push being used to make a head pressure, it will be used to drive current...and the stator wires can't handle but so much of that. Your faced with balancing when to have the alternator cut in against how much current can the stator wires handle, and I would think that a few tenths of a volt would be the difference between the alternator doing all the work before the generator burns itself up, vs the alternator doing all the work after the generator burns itself up. On this score, I'd check with someone smarter than me, though. -- http://www.ronpaultimeline.com