X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Received: from imo-d20.mx.aol.com ([205.188.139.136] verified) by logan.com (CommuniGate Pro SMTP 5.2.2) with ESMTP id 2876282 for flyrotary@lancaironline.net; Mon, 28 Apr 2008 22:34:10 -0400 Received-SPF: pass receiver=logan.com; client-ip=205.188.139.136; envelope-from=SHIPCHIEF@aol.com Received: from SHIPCHIEF@aol.com by imo-d20.mx.aol.com (mail_out_v38_r9.3.) id q.c0f.262c2d06 (41811) for ; Mon, 28 Apr 2008 22:33:22 -0400 (EDT) From: SHIPCHIEF@aol.com Message-ID: Date: Mon, 28 Apr 2008 22:33:22 EDT Subject: Re: [FlyRotary] Re: the Kubota dynamo To: flyrotary@lancaironline.net MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="part1_c0f.262c2d06.3547e2f2_boundary" X-Mailer: 7.0 for Windows sub 10618 X-Spam-Flag: NO --part1_c0f.262c2d06.3547e2f2_boundary Content-Type: text/plain; charset="US-ASCII" Content-Transfer-Encoding: 7bit Well that's how they do it? I know that the older Permanent Magnet Alternators were regulated by sending excess power to ground. that means the extra current that would allow voltage to run too high is sent via a regulated transistor to ground. That's a controlled resistance, so heat is released and you need a heat sink. Motorcycles use this system. Old English bikes like my BSA just used a large Zenir Diode that would spill all excess power to the heat sink above the 14.5 nominal volts that it was rated. I heard that newer PM alternators regulated differently so they didn't 'waste power', switching could do it and thus reduce the heat of that wasted power. Standard automotive alternators (Trucks boats airplanes) have non permanent electro-magnets in the rotating assembly. The regulator controls current thru slip rings to the electro magnet. This is called Field Current because it adjusts the magnetic field strength so the alternator voltage output is maintained at the nominal voltage (14.25 to 14.5 give or take) So the alternator only takes as much power from the engine as required to maintain the voltage up to the max current output of the alternator. If this alternator were turned off, it would just be a belt tensioner. 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 ************** Need a new ride? Check out the largest site for U.S. used car listings at AOL Autos. (http://autos.aol.com/used?NCID=aolcmp00300000002851) --part1_c0f.262c2d06.3547e2f2_boundary Content-Type: text/html; charset="US-ASCII" Content-Transfer-Encoding: quoted-printable Well that's how they do it?
I know that the older Permanent Magnet Alternators were regulated by sending= excess power to ground. that means the extra current that would allow volta= ge to run too high is sent via a regulated transistor to ground. That's a co= ntrolled resistance, so heat is released and you need a heat sink. Motorcycl= es use this system.
Old English bikes like my BSA just used a large Zenir Diode that would spill= all excess power to the heat sink above the 14.5 nominal volts that it was=20= rated.
I heard that newer PM alternators regulated differently so they didn't 'wast= e power', switching could do it and thus reduce the heat of that wasted powe= r.
Standard automotive alternators (Trucks boats airplanes) have non permanent=20= electro-magnets in the rotating assembly. The regulator controls current thr= u slip rings to the electro magnet. This is called Field Current because it=20= adjusts the magnetic field strength so the alternator voltage output is main= tained at the nominal voltage (14.25 to 14.5 give or take) So the alternator= only takes as much power from the engine as required to maintain the voltag= e up to the max current output of the alternator. If this alternator were tu= rned off, it would just be a belt tensioner.
For this reason, I would think the permanent magnet altrnator would be used=20= all the time at capacity, and it would be sized to meet the minimum power re= quirement of the aircraft. The Field Current controlled alternator would car= ry all excess loads like recharging the start battery, and auxilliary equipm= ent, say the full avionics suite and entertainment air conditioning what hav= e you.
Scott


**************
Need a new ride? Check out the lar= gest site for U.S. used car listings at AOL Autos.
(http://autos.ao= l.com/used?NCID=3Daolcmp00300000002851) --part1_c0f.262c2d06.3547e2f2_boundary--