Return-Path: Received: from victoria.pe.net ([64.38.64.7]) by ns1.olsusa.com (Post.Office MTA v3.5.3 release 223 ID# 0-64832U3500L350S0V35) with ESMTP id com for ; Mon, 1 Jan 2001 20:33:06 -0500 Received: from ieee.org (IP-87-194.tem.pe.net [64.38.87.194]) by victoria.pe.net (8.9.3/8.9.1) with ESMTP id RAA22945; Mon, 1 Jan 2001 17:41:14 -0800 (PST) Message-ID: <3A51318A.84DF6169@ieee.org> Date: Mon, 01 Jan 2001 17:40:26 -0800 From: "Charles R. Patton" Reply-To: charles.r.patton@ieee.org Reply-To: lancair.list@olsusa.com To: Robert Smiley CC: lancair.list@olsusa.com Subject: Re: alternators/brushes References: <3A50DBF3.A0FF9DCC@ieee.org> <000d01c07453$22b88700$a0ca0041@saltlk1.ut.home.com> X-Mailing-List: lancair.list@olsusa.com Mime-Version: 1.0 <<<<<<<<<<<<<<<<--->>>>>>>>>>>>>>>> << Lancair Builders' Mail List >> <<<<<<<<<<<<<<<<--->>>>>>>>>>>>>>>> >> Basically, yes, I don't feel that you have to worry about high altitude, corona initiated arcs. In general I would be careful to be sure that BEMF collapse is prevented. This amounts to being sure that a load always exists on the output of the alternator. For instance opening the master relay could unload the alternator completely in some configurations. The best solution would be to have a 25 to 50V (on 12 V systems) MOV directly from the field and output terminals to ground (frame). This is good practice anyway to protect the avionics. As I recall, specifications for car electronics plan on 50 to 60 V spikes, in lieu of the use of MOV’s. As previously discussed though, there may be problems with the brushes "dusting." Carbon dust can complete a low voltage path and thereby initiate a low voltage arc that has absolutely nothing to do with altitude. Why and if brushes act worse in (high altitude) service will have to be answered by someone else. Robert Smiley wrote: > In plain language, are you saying we do not need to worry about electrical > arcs in auto -mitsubishi alternators below 18,000 MSL? >>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>> LML website: http://www.olsusa.com/Users/Mkaye/maillist.html LML Builders' Bookstore: http://www.buildersbooks.com/lancair Please send your photos and drawings to marvkaye@olsusa.com. >>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>