X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Received: from [206.46.252.40] (HELO vms040pub.verizon.net) by logan.com (CommuniGate Pro SMTP 4.3.2) with ESMTP id 966524 for flyrotary@lancaironline.net; Sat, 28 May 2005 13:47:34 -0400 Received: from verizon.net ([71.98.177.250]) by vms040.mailsrvcs.net (Sun Java System Messaging Server 6.2 HotFix 0.04 (built Dec 24 2004)) with ESMTPA id <0IH7000ERO36B1I1@vms040.mailsrvcs.net> for flyrotary@lancaironline.net; Sat, 28 May 2005 12:47:30 -0500 (CDT) Date: Sat, 28 May 2005 13:47:29 -0400 From: Finn Lassen Subject: Re: [FlyRotary] Re: Amps consumed data In-reply-to: To: Rotary motors in aircraft Message-id: <4298AEB1.1010206@verizon.net> MIME-version: 1.0 Content-type: multipart/alternative; boundary=------------080708010103070509060607 X-Accept-Language: en-us, en References: User-Agent: Mozilla/5.0 (Windows; U; Windows NT 5.1; en-US; rv:1.4) Gecko/20030624 Netscape/7.1 (ax; PROMO) This is a multi-part message in MIME format. --------------080708010103070509060607 Content-Type: text/plain; charset=us-ascii; format=flowed Content-Transfer-Encoding: 7bit "crowbar" here means "shorting to ground". I haven't followed later discussions where Bob N. changed from that method (on the field lead) to using a relay in the output lead, if he indeed did. I don't see how the alternator can put out any voltage when its field winding is shorted. Finn Jim Sower wrote: > Finn Lassen wrote: > >> Yes, you'll need a relay in series with the "fat" wire, IF you have >> an internally regulated alternator that does NOT stop putting out >> voltage when the "thin" wire is disconnected. Looks like Bernie's >> alternator will not need that relay. No need to introduce an unneeded >> additional component - another point of possible failure. >> According to Nuckolls, even alternators with external regulators can >> run away and that's why he recommends the crowbar OV protector. >> Disconnecting the "thin" wire won't always stop the alternator from >> putting out. You have to disconnect the "fat" (B+) line to be >> assured of an end to an over voltage condition ... Jim S. >> Finn >> --------------080708010103070509060607 Content-Type: text/html; charset=us-ascii Content-Transfer-Encoding: 7bit "crowbar" here means "shorting to ground". I haven't followed later discussions where Bob N. changed from that  method (on the field lead) to using a relay in the output lead, if he indeed did.

I don't see how the alternator can put out any voltage when its field winding is shorted.

Finn

Jim Sower wrote:
Finn Lassen wrote:
Yes, you'll need a relay in series with the "fat" wire, IF you have an internally regulated alternator that does NOT stop putting out voltage when the "thin" wire is disconnected. Looks like Bernie's alternator will not need that relay. No need to introduce an unneeded additional component - another point of possible failure.
According to Nuckolls, even alternators with external regulators can run away and that's why he recommends the crowbar OV protector.  Disconnecting the "thin" wire won't always stop the alternator from putting out.  You have to disconnect the "fat" (B+) line to be assured of an end to an over voltage condition ... Jim S.
Finn

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