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Mark and Jim,
Mirrors my reasons to modify the stock Mazda alternator.........As I
demonstrated at the "Roundup" last year the process is the same for
the Mitsubishi (sp)..........Remove the internal regulator.......Isolate the
field........Wire one brush to ground and the other to an existing external
connector that will go to the field terminal of the selected regulator.......
--
Kelly Troyer
Dyke Delta/13B/RD1C/EC2
-------------- Original message from "Mark R Steitle" <mark.steitle@austin.utexas.edu>: --------------
> Jim,
> I first explored this issue after Bob Knuckols expressed a dislike of
> internally regulated alternators...because they can fail in such a way
> that you cannot shut them down. Yes, you can interrupt the "B" lead,
> but this will not shut down the alternator. I imagine it could get hot
> enough to self-destruct and possibly catch fire.
>
> The modification I use removes the internal regulator assembly and puts
> a direct (external) feed line to one of the brushes. The other brush is
> tied to ground. Nothing else is connected to the field. With this
> arrangement, can you explain how removing power from one of the brushes
> will allow the alternator to continue producing power? I've tested my
> modified alternators with the engine running and it does in fact stop
> producing power when I cut the power to this lead.
>
> Another benefit to an external regulator is that you can precisely
> adjust the voltage, provided you use an adjustable regulator.
>
> Mark S.
>
> -----Original Message-----
> From: Rotary motors in aircraft [mailto:flyrotary@lancaironline.net] On
> Behalf Of Jim Sower
> Sent: Thursday, September 08, 2005 5:31 PM
> To: Rotary motors in aircraft
> Subject: [FlyRotary] Re: Overvoltage control (help Ed A)
>
> I've always been puzzled why folks would go to all the trouble of
> disabling a perfectly good internal regulator so as to install an
> external unit. If the Field circuit gets somehow internally shorted to
> the output circuit, the alternator is going to run away and create an
> over voltage condition. In that event, there's no way that turning off
> current to the Field is going to help you. Other than a short
> described, I don't know how an over voltage can occur. So my question
> is: is an internally regulated system all that much more apt to have an
>
> over voltage type failure, and if so why? I've had lots of trouble with
>
> externally regulated alternators, very little with internal regulators.
>
> My crowbar over voltage system is bullet proof. It's the only scheme
> that prevents damage caused by an internal short in the alternator.
> What, exactly, is the big attraction of external regulators? ... Jim S.
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