Mailing List flyrotary@lancaironline.net Message #52190
From: <Lehanover@aol.com>
Subject: Re: [FlyRotary] Re: Alternator
Date: Wed, 22 Sep 2010 11:51:15 EDT
To: <flyrotary@lancaironline.net>
In a message dated 9/22/2010 11:07:43 A.M. Eastern Standard Time, bktrub@aol.com writes:
I don't know how likely an overvoltage condition is with the internal regulator in the denso alternator is, but if it did run away like that, you cook your computer and the big fan thingy attached to your motor stops moving and it gets real quiet.
 
I'm not sure, but I think that an overvoltage condtion is much more likely with a mechanical voltage regulator. Anyone out there know  more about these things?
 
Brian Trubee
My feeble understanding is that, in the alternator the flux field is spinning, as opposed to being stationary in the generator, and voltage output is controlled by how much voltage the regulator puts into the armature through the brushes and slip rings.
 
So to reduce the output voltage to near zero you must cut the voltage to the brushes. No flux field, no output.
So, a heavy double pole single throw switch in series with the brushes, should be adequate to eliminate the alternator as a problem.
 
If one brush is just grounded inside the alternator, then battery supply to the regulator could go through the same switch. Then you would have nothing in and nothing out.
 
A big diode on the alternator output would isolate the alternator from the battery(s) so a total meltdown could not take the battery(s) out with the alternator failure. 
 
Lynn E. Hanover
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