X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Received: from [64.12.143.101] (HELO imo-m13.mail.aol.com) by logan.com (CommuniGate Pro SMTP 5.2.2) with ESMTP id 2876988 for flyrotary@lancaironline.net; Tue, 29 Apr 2008 11:58:06 -0400 Received-SPF: pass receiver=logan.com; client-ip=64.12.143.101; envelope-from=WRJJRS@aol.com Received: from WRJJRS@aol.com by imo-m13.mx.aol.com (mail_out_v38_r9.3.) id q.c62.2dd3c6a3 (37130) for ; Tue, 29 Apr 2008 11:57:12 -0400 (EDT) Received: from webmail-nb10 (webmail-nb10.sim.aol.com [207.200.69.202]) by cia-ma02.mx.aol.com (v121.5) with ESMTP id MAILCIAMA024-910a481745552e3; Tue, 29 Apr 2008 11:57:10 -0400 References: To: flyrotary@lancaironline.net Subject: Re: [FlyRotary] Re: the Kubota dynamo Date: Tue, 29 Apr 2008 11:57:09 -0400 X-AOL-IP: 66.253.96.220 In-Reply-To: X-MB-Message-Source: WebUI MIME-Version: 1.0 From: wrjjrs@aol.com X-MB-Message-Type: User Content-Type: multipart/alternative; boundary="--------MB_8CA7828D0F328B7_D58_1DDD_webmail-nb10.sysops.aol.com" X-Mailer: AOL Webmail 36240-STANDARD Received: from 66.253.96.220 by webmail-nb10.sysops.aol.com (207.200.69.202) with HTTP (WebMailUI); Tue, 29 Apr 2008 11:57:09 -0400 Message-Id: <8CA7828D0857BD3-D58-EEE@webmail-nb10.sysops.aol.com> X-Spam-Flag: NO ----------MB_8CA7828D0F328B7_D58_1DDD_webmail-nb10.sysops.aol.com Content-Transfer-Encoding: 7bit Content-Type: text/plain; charset="us-ascii" The load dumping circuits used a ziener diode. That was common in old brit bikes. Look at some of the old bikes with the big finned resistor sitting under the headlight. That is a very inefficient method. The switching model works much better. You do need high power solid state devices though. Bill Jepson -----Original Message----- From: SHIPCHIEF@aol.com To: Rotary motors in aircraft Sent: Mon, 28 Apr 2008 7:33 pm Subject: [FlyRotary] Re: the Kubota dynamo 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) ----------MB_8CA7828D0F328B7_D58_1DDD_webmail-nb10.sysops.aol.com Content-Transfer-Encoding: 7bit Content-Type: text/html; charset="us-ascii" The load dumping circuits used a ziener diode. That was common in old brit bikes. Look at some of the old bikes with the big finned resistor sitting under the headlight. That is a very inefficient method. The switching model works much better. You do need high power solid state devices though.
Bill Jepson


-----Original Message-----
From: SHIPCHIEF@aol.com
To: Rotary motors in aircraft <flyrotary@lancaironline.net>
Sent: Mon, 28 Apr 2008 7:33 pm
Subject: [FlyRotary] Re: the Kubota dynamo

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)
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