Is your internally regulated alternator adjustable?  -----Original Message-----
From: Rotary motors in aircraft [mailto:flyrotary@lancaironline.net] On
Behalf Of Jim Sower
Sent: Friday, September 09, 2005 2:32 PM
To: Rotary motors in aircraft
Subject: [FlyRotary] Re: Overvoltage control (help Ed A)

If my crowbar overvoltage opens the B+ circuit, there's NO current flowing out of the alternator.  Absent current, there can be no heat generated.  The field can go to max output, there will be high voltage at the B+ terminal, but no heat generated.  Sounds to me like a bogus concern.  I think the key issue is "... Nuckolls expressed dislike ..." and no further support is "needed".

Still looking for a "real" reason ... Jim S.

Mark R Steitle wrote:

 

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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