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Date: Thu, 26 May 2005 23:56:00 -0500
From: Jim Sower <canarder@frontiernet.net>
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To: Rotary motors in aircraft <flyrotary@lancaironline.net>
Subject: Re: [FlyRotary] Re: Amps consumed data
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I think you've got it!!  ... Jim S.

Charlie England wrote:

> Most (all?) unmodified, internally regulated alternators would need an 
> overvoltage-controlled relay to disconnect the B lead in order to 
> protect the electronics from overvoltage in the case of a regulator 
> failure. Some failure modes of the regulator could cause continued 
> (unregulated) power to the field winding & therefore unregulated 
> output from the alternator.
>
> Was that as hard to read as it was to write?
>
> Charlie
> (flying without protection)
>
> Finn Lassen wrote:
>
>> Yes, you'll need a relay in series with the "fat" wire, IF you have 
>> an internally regulated alternator that does NOT stop putting out 
>> voltage when the "thin" wire is disconnected. Looks like Bernie's 
>> alternator will not need that relay. No need to introduce an unneeded 
>> additional component - another point of possible failure.
>>
>> Finn
>>
>> Jim Sower wrote:
>>
>>> Finn Lassen wrote:
>>>
>>>> The small wire goes to its separate circuit breaker. The crowbar is 
>>>> connected to this wire (and ground).
>>>> When the crowbar circuit senses an over-voltage, it clamps that 
>>>> wire to ground (and pops the circuit breaker).
>>>> Only works on your kind of alternator that stops putting out 
>>>> voltage on the fat wire when it doesn't get voltage in on the 
>>>> "thin" wire.  I have an internal regulator, so all I have is a 
>>>> "fat" (B+) wire.  I jump the B+ terminal of the Alt to the "F" 
>>>> terminal with a couple inches of 17 ga wire.  I connect and 
>>>> disconnect the B+ to the rest of the airplane with a "master" relay 
>>>> powered by the Alt switch on the panel and protected by Nuckolls' 
>>>> crowbar.  In an over voltage situation, the relay opens.  The Alt 
>>>> is disconnected from the airplane and I could care less what the 
>>>> voltage is. As someone else asked, does it really stop putting out 
>>>> voltage on the fat wire - easily measured on the fat wire with a 
>>>> voltmeter - voltage should drop to maybe 13.2 V as opposed to the 
>>>> 15 - 16 Volts when alternator is delivering power.
>>>>
>>>> Finn
>>>
>>>
>
>
>
>>>  Homepage:  http://www.flyrotary.com/
>>>  Archive:   http://lancaironline.net/lists/flyrotary/List.html
>>
>
>