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1. 10:49 AM - AeroElectric-List Digest: (Jesse Jenks)
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| Subject: | AeroElectric-List Digest: |
Time: 06:36:34 AM PST US
From: "Robert L. Nuckolls=2C III" <nuckolls.bob@aeroelectric.com>
Subject: Re: AeroElectric-List: planning
>So=2C I guess the jumper is what causes the run-on=2C and whatever I do
>I don't want it in there. I don't already have a separate contactor=2C
>so the way I understand it my options are=3B 1) use Z-22 with a relay=2C
>2) just use a push button rated for 30 amps and no relay.
Yes.
>Can you explain why run-on is a problem if it only lasts a couple seconds?
The design goal for engagement solenoids with
integral contactors is to effect immediate retraction
of the pinion gear when the starter button is
released. There ARE over-run clutches in the starter
gearing that prevents the engine from back-driving
the starter. These are VERY important . . .
For a small starter to be efficient=2C the armature
is highly geared down to crank the engine at 150
to 300 rpm. when the engine starts=2C it's suddenly
running at 4x that speed. Were it not for over-run
clutches=2C this would immediately spin the armature
up to 4x it's operating speed and probably throw
windings=2C commutator bars=2C or strip gear teeth.
The run-on phenomenon simply exercises the over-run
mechanism and increases pinion wear for reasons that
do not add value . . . and would not happen except
for an unintended consequence of using the solenoid/
contactor in a manner contrary to original design
goals.
Bob . . .
Thanks Bob. I think I finally get it.
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