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Update: Strange alternator behavior at Startup

 
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nuckollsr(at)cox.net
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PostPosted: Wed Mar 01, 2006 6:51 am    Post subject: Update: Strange alternator behavior at Startup Reply with quote

At 07:18 AM 2/28/2006 -0800, you wrote:

Quote:


Robert L. Nuckolls, III wrote:
>
<nuckollsr(at)cox.net>
>
> At 07:01 AM 2/28/2006 -0500, you wrote:
>
>>
>> <mstewart(at)iss.net>
>>
>> Oh.
>> Well that is very interesting Brian. Could it be that my IGN wire is
>> dead?
>> I have the IGN with voltage applied before cranking (I think. I have not
>> checked it since initial install) and I have an idiot light installed
>> which does work as expected. I will check that IGN wire next time I have
>> the cowl off to verify it is supplying power before cranking. Based on
>> your note below, it is quite possible the IGN wire is doing nothing.
>> Wonder why temperature is at play though.
>>
>> Ill check it and report back.
>
> Brian, have you been holding out on us?

Uh, no. I thought this was common knowledge about IR alternators.

Just yanking your chain my friend. We do know that SOME alternators
under SOME conditions will come up self excited and that this feature
is incidental to the system design requirements. After some thought about
this thread, I'm almost convinced that there's something amiss with
the system cited. It should snap to attention within seconds of
startup and at ordinary idle/taxi RPM levels.

Quote:
> I've not been aware of
> any automotive products that would ultimately self-excite at
> any time interval or speed conditions. An interesting phenomenon to
> contemplate.

Almost every IR alternator I have played with exhibits this characteristic.

Now it may be that new ones have no residual magnetism in the field
armature and therefore cannot self excite. OTOH, *I* have not run into
one that would not self excite once you turned it fast enough.

Good data point. Since I've never attempted to utilize
this capability in a design, I've never explored the
feature in practice.
Quote:
>
> Just last year I shared the following from my experience with
> the alternators on Bonanzas and Barons:

Yeah. I just assumed that is how they were supposed to work too. And
just the act of using them for awhile builds up magnetism in the
armature. I suspect that, even if they don't self-excite when brand new,
they will after having been used for several hours.

It stands to reason that since the retentivity of ANY magnetic
material is never zero, that the ability to self-excite probably
exists at SOME RPM even if scary to contemplate. It stands to
reason that many examples in the wild will exhibit the behavior
at fairly ordinary RPM levels.

Bob . . .


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brian



Joined: 02 Jan 2006
Posts: 643
Location: Sacramento, California, USA

PostPosted: Wed Mar 01, 2006 7:37 am    Post subject: Update: Strange alternator behavior at Startup Reply with quote

On Mar 1, 2006, at 6:47 AM, Robert L. Nuckolls, III at Startup wrote:

Quote:
>>
>> Brian, have you been holding out on us?
>
> Uh, no. I thought this was common knowledge about IR alternators.

Just yanking your chain my friend.

Sorry. I tend to err on the literal side. Wink

Quote:
We do know that SOME alternators
under SOME conditions will come up self excited and that this
feature
is incidental to the system design requirements. After some
thought about
this thread, I'm almost convinced that there's something amiss
with
the system cited. It should snap to attention within seconds of
startup and at ordinary idle/taxi RPM levels.

My experience with a LOT of alternators at this point is that they
need some RPM substantially higher than idle to self-excite. That is
why they use a small amount of current from the battery bus to
bootstrap them.

Quote:
>
> Almost every IR alternator I have played with exhibits this
> characteristic.
>
> Now it may be that new ones have no residual magnetism in the field
> armature and therefore cannot self excite. OTOH, *I* have not run
> into
> one that would not self excite once you turned it fast enough.

Good data point. Since I've never attempted to utilize
this capability in a design, I've never explored the
feature in practice.

And I have messed with enough of them to believe
this is a common behavior.

Quote:
>> Just last year I shared the following from my experience with
>> the alternators on Bonanzas and Barons:
>
> Yeah. I just assumed that is how they were supposed to work too. And
> just the act of using them for awhile builds up magnetism in the
> armature. I suspect that, even if they don't self-excite when
> brand new,
> they will after having been used for several hours.

It stands to reason that since the retentivity of ANY magnetic
material is never zero, that the ability to self-excite probably
exists at SOME RPM even if scary to contemplate. It stands to
reason that many examples in the wild will exhibit the behavior
at fairly ordinary RPM levels.

Right.
Brian Lloyd 361 Catterline Way
brian-yak at lloyd dot com Folsom, CA 95630
+1.916.367.2131 (voice) +1.270.912.0788 (fax)

I fly because it releases my mind from the tyranny of petty things . . .
Antoine de Saint-Exupry


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Brian Lloyd
brian-yak at lloyd dot com
+1.916.367.2131 (voice) +1.270.912.0788 (fax)

I fly because it releases my mind from the tyranny of petty things . . .
- Antoine de Saint-Exupery
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