Message-ID: <001a01c38887$5b64c8c0$1702a8c0@WorkGroup>
From: "Ed Anderson" <eanderson@carolina.rr.com>
To: "Rotary motors in aircraft" <flyrotary@lancaironline.net>
References: <list-2620610@logan.com>
Subject: Re: [FlyRotary] Re: alternator choice?
Date: Wed, 1 Oct 2003 21:49:02 -0400
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 ----- Original Message -----
From: "Mark Steitle" <msteitle@mail.utexas.edu>
To: "Rotary motors in aircraft" <flyrotary@lancaironline.net>
Sent: Wednesday, October 01, 2003 8:01 PM
Subject: [FlyRotary] Re: alternator choice?


> I'm not an expert in electronics.  I was following the advice of Bob
> Nuckols on the Aero-electric connection.  There are failure modes with
> internal regulators such as a "run-away" that can't be stopped by shutting
> off the field current.  This possibility necessitates using over-voltage
> protection at a very minimum.  The problem comes with how to hook OVP up
to
> an internally regulated alternator.  There's a schematic on the
> Aero-electric Connection at
> http://www.aeroelectric.com/articles/bleadov.pdf that shows how to do
> that.  Its not that hard to bypass the internal regulator and go with a
> Ford solid-state regulator.  They're reliable and very affordable.  Add
OVP
> and you're all set.
>
>    At 10:13 AM 10/1/2003 -0700, you wrote:
> >What was the reason for going external regulator? By going to a dual
> >alternator can't I just switch one off if it goes bonkers (or have an
> >overvoltage relay do that for me)?
> >
> >re

I can vouch for what Mark says.  For a long time I thought I could "turn
off" my auto alternator (internal regulator) by pulling the circuit breaker
that controls the voltage to the field coil.  I figured no voltage to the
field coil - no alternator generated voltage - Wrong!.  The test I conducted
turned out to be faulty.   I would pull the circuit breaker before starting
the engine and fire up the engine and sure enough NO VOLTAGE.  However, once
voltage is produced, my alternator (at least) no longer needs to have
external voltage to the field coils.  I can pull the circuit breaker and it
makes no difference, voltage will continue to be produced.  So once it is
generating voltage, it apparently dervies sufficient voltage for the field
coil from internal sources that it no longer needs external voltage source.


Ed Anderson
RV-6A N494BW Rotary Powered
Matthews, NC
eanderson@carolina.rr.com