Return-Path: Received: from hotmail.com ([216.32.180.115]) by truman.olsusa.com (Post.Office MTA v3.5.1 release 219 ID# 0-52269U2500L250S0V35) with SMTP id com for ; Fri, 23 Jul 1999 00:04:35 -0400 Received: (qmail 8748 invoked by uid 65534); 23 Jul 1999 04:07:01 -0000 Message-ID: <19990723040701.8747.qmail@hotmail.com> From: "Sean Walker" To: "LML" , "Pat Weston" References: <001a01bed495$70adb340$2a00a8c0@fat-albert> Subject: Re: Master relay Date: Fri, 23 Jul 1999 14:11:38 +1000 X-Mailing-List: lancair.list@olsusa.com Mime-Version: 1.0 <<<<<<<<<<<<<<<<--->>>>>>>>>>>>>>>> << Lancair Builders' Mail List >> <<<<<<<<<<<<<<<<--->>>>>>>>>>>>>>>> >> >From: Pat Weston >Subject: Re: Master relay >There is no > increased power generated from the coil or the contacts due to frequently > energizing and de-energizing the relay. I disagree > At no time is the > current more than that in the steady state, thus the power (current squared > times coil resistance) greater than when the set up is in the steady state. Do you mean to say that the pull in current is never more than the hold in current. My understanding of a coil, solenoid or contactor is that pull-in in current is greater and the hold-in current less due to the increased inductance due to the magnetic circuit being closed. Also it is a positive design feature as as the pull-in forse is greater than the holdin forse. a contiuous cycle of opening and closing would give an overall aversge increased power consumption. Increased power consumption = increased power that needs to be dissipated. > Thus a relay being turned on and off dissipates less power than one in a > permanently on state. > The heat from the contacts is produced only when the contacts are closed, a > load is applied and a current is flowing, thus if a relay is turned off, > there is no heat from the contacts. I tried to explain this in laymans terms as much as possible to simplify it to the average reader. May be I have miss understood something. Your comments contradict what have learnt in college, experienced in practice and information researched in ctalogue from Allen Bradley to Sprecher and Shuh. I am interested to read your comments. Sean Walker Checkpoint Engineering and Electrical Service Gunnedah, Australia cpeng@mpx.com.au >>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>> LML homepage: http://www.olsusa.com/Users/Mkaye/maillist.html