Message-Id: <3.0.3.32.19990722015211.00af3c20@olsusa.com>
Date: Thu, 22 Jul 1999 01:52:11 -0400
To: lancair.list@olsusa.com
From: Marvin Kaye <marvkaye@olsusa.com>
Subject: Re: Master relay
Mime-Version: 1.0

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Posted for "Sean Walker" <sean_oz@hotmail.com>:

Hello from Down Under,

I'm new to the list so please bare with me until I get up to speed. On the
question of relays in the Automotive and Mains Connected electrical
systems, a continuously rated component is rated to carry its maximum
specified load continuously, and has the ability to dissipate the built up
heat accordingly. An intermittent or low duty cycle component would have
and average load capacity with an ability to handle higher peaks. These
rules are general to most electrical equipment.

A relay ( contactor or any other switch ) is also rated the number of times
it opens and closes. The more often a relay opens and closes the more heat
generated. Heat is generated from two sources, the first is the coil. More
current is drawn when a coil is open as it is energised to close than its
closed or holdin current. So the amount of heat generated is greater if the
relay opens and closes repeatedly. The second source of heat is the
contacts which follow the same rules as for the coil the more open/close
cycles you have the more heat.

Heat can also be generated from bad connections as well. A poor connection
behind the relay could cause the same problem.

My understanding of relays ( I am an electrician/engineer ) is they should
not be too hot to touch. Not being familiar  with the type of relay your
using and the load on it is difficult to say what your problem is. Check
that the relay is able to carry the load required.  Have you tested the
load on the relay? Have you added more equipment which would increase the
load? If the relay is not working as a load sensing, current limmiting
device ( i.e. not a circuit breaker ) than fitting a higher rated relay is
an option.

Please treat all my comments carefuly as I am not an expert on aircraft
wiring ( learning quickly though ) any problems or modifications I would
recomend talking to the manufacture of the relay and a LAME ( Ausi term -
Licenced Aircraft Maintence Engineer )

Below is a web address from a site I read ages ago if I remeber right and
have not confused the sitethe is some good information to be had from it.

             http://www.aeroelectric.com/

Hope this helps.
Sean Walker
Checkpoint Engineering
Australia
cpeng@mpx.com.au


{Sean, and everyone else... Please stop posting dual formatted messages.  I
have made countless requests in very polite terms that you set your email
programs into the text only mode for posts to the LML.  I have been very
patient in this regard and taken the time necessary to reformat and
resubmit messages that were improperly formatted as a courtesy to both the
posters and the rest of the subscribers... I don't want anyone to miss any
messages if at all possible.  I am, however, tired of this unnecessary
activity, and am no longer going to provide this particular added service.
Any posts which arrive dual formatted will be rejected and there will be no
more explanatory letters following that action to the offending posters.
The directions for setting up both MS Outlook Express and Netscape
Communicator are on the LML homepage in the List Posting Guidelines...
please check there if you need help with making these settings. This will
be the last you'll hear about this subject, and I'm sorry for the rant.
Thank you.    <Marv>    ]

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