Today's Message Index:
----------------------
1. 05:15 AM - Re: Re: Interesting thread on overvoltage event (Charlie England)
2. 05:17 AM - Re: Interesting thread on overvoltage event (user9253)
3. 06:04 AM - Re: Interesting thread on overvoltage event (rv8ch)
4. 06:42 AM - Re: Re: Interesting thread on overvoltage event (Charlie England)
5. 06:58 AM - Re: Interesting thread on overvoltage event (rv8ch)
6. 07:33 AM - Re: Re: Interesting thread on overvoltage event (Robert L. Nuckolls, III)
7. 07:40 AM - Re: Is a battery contactor really needed? (eschlanser)
8. 01:32 PM - Re: Re: Interesting thread on overvoltage event (Jan de Jong)
9. 03:20 PM - Re: Re: Is a battery contactor really needed? (Robert L. Nuckolls, III)
Message 1
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| Subject: | Re: Interesting thread on overvoltage event |
There's no difference in how they control the field windings. The big
difference *access* to the wire going to the field, by the pilot, for
manual control, or the OV module, for automatic control. With external
regulation, you can easily interrupt the power feeding the regulator (or
even the field wire running from the reg to the alternator's field winding)
to remove power from the field winding if the regulator fails. But with an
(unmodified) IR alternator, you don't have access to either of those wires
(they're both inside the alternator), so if the regulator fails, there's no
way to remove power from the field if the regulator fails.
The IG terminal on an IR alternator does not supply/remove power from the
regulator; it's a 'instruction' terminal that gives the regulator an
instruction to turn on or off. If the regulator fails internally, it will
likely be unable to comply with the instruction from the IG terminal, so
you've lost external control of the alternator. Now the only option is to
open the B-lead to keep the OV away from the avionics and battery.
Charlie
On Wed, Apr 26, 2017 at 1:17 AM, Mickey Coggins <mick-matronics@rv8.ch>
wrote:
> Thanks for the info. My question is much more "novice". Perhaps I shoul
d
> describe it a different way.
>
> Imagine I took the B&C voltage regulator, and made it the size of a dime,
> and stuffed it into an Externally regulated alternator. How would that b
e
> different from what Denso does with their internally regulated alternator
?
>
> From what I see from the diagrams, the VR simply decides how much V to
> send out the F wire. Why would the external give more control?
>
> Thanks for any clarity! :)
>
>
> =8B
>
> Mickey Coggins
>
> On 25 April 2017 at 15:18, Robert L. Nuckolls, III <
> nuckolls.bob@aeroelectric.com> wrote:
>
>> At 04:45 AM 4/25/2017, you wrote:
>>
>>
>> One point that is not clear for me about the internal/external VR
>> discussion. I apologize in advance if this has been clarified somewhere
>> else and I just missed it.
>>
>> I don't understand why or how an external voltage regulator can safely
>> cut the field using the crowbar method and an internal regulator cannot.
>> If I look at the wiring diagrams there does not seem to be a difference.
>> Is it just that the external VR is more robust?
>>
>> Thanks for any clarity you can provide.
>>
>>
>> The externally regulated alternator has NO electronics
>> inside . . . just a rudimentary alternator.
>>
>> [image: Emacs!]
>>
>> Interrupting the 'field input' line offers total
>> control over alternator output.
>>
>> The internally regulated alternator has solid
>> state devices that control alternator output.
>> There is no field power input connection, only
>> a 'control' connection that talks to the
>> electronics.
>>
>> [image: Emacs!]
>>
>> There are failure modes INTERNAL to the alternator
>> that can cause an over voltage condition . . . a
>> * condition not controllable* from outside.
>>
>> Hence, the legacy preference for externally regulated
>> alternators that allow a system integrator to include
>> over voltage protection in some form. It doesn't
>> have to be the 'crowbar' style . . . there are several
>> satisfactory approaches.
>>
>> The crowbar ov module offers the simplest and most
>> robust configuration but it's not intended to displace
>> any other demonstrably functioning ov management system.
>>
>> Bob . . .
>>
>
>
Message 2
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| Subject: | Re: Interesting thread on overvoltage event |
> Why would the external give more control?
They both have equal control as long as they do not fail. What happens when the
voltage regulator fails? How do you shut off the failed regulator to prevent
over-voltage? Some internally regulated alternators have an ignition switch
terminal that controls the alternator. But that input does not make and break
the field circuit. All it does is command the internal regulator to shut off
the field. A failed internal regulator could ignore that command and continue
to supply excessive field current.
The external voltage regulator has easily accessible wires and circuit protection.
It is relatively easy to tap into the externally regulated alternator field
circuit to add a switch or automatic over-voltage protection.
Yes, it is possible to do the same thing with an internally regulated alternator,
but it requires much more skill and knowledge which the average homebuilder
does not have.
The internally regulated alternator gets its field current from within the alternator.
The externally regulated alternator gets its field current from the aircraft main
power bus.
Which is easiest to interrupt?
--------
Joe Gores
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=468798#468798
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| Subject: | Re: Interesting thread on overvoltage event |
user9253 wrote:
> The internally regulated alternator gets its field current from within the alternator.
> The externally regulated alternator gets its field current from the aircraft
main power bus.
> Which is easiest to interrupt?
This is exactly what triggered my question - in all the Z diagrams it shows the
field wire coming from the external VR with no circuit breaker or switch, so
it's counting on the good behavior of the VR to cut off the alternator - same
as with an internal VR.
Why do we have more trust in the external VR than the internal VR? Experience?
Known design differences? Perhaps I'm missing something fundamental. Curious
minds want to know! :)
--------
Mickey Coggins
http://www.rv8.ch/
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=468801#468801
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| Subject: | Re: Interesting thread on overvoltage event |
On Wed, Apr 26, 2017 at 8:03 AM, rv8ch <mick-matronics@rv8.ch> wrote:
>
>
> user9253 wrote:
> > The internally regulated alternator gets its field current from within
> the alternator.
> > The externally regulated alternator gets its field current from the
> aircraft main power bus.
> > Which is easiest to interrupt?
> This is exactly what triggered my question - in all the Z diagrams it
> shows the field wire coming from the external VR with no circuit breaker or
> switch, so it's counting on the good behavior of the VR to cut off the
> alternator - same as with an internal VR.
>
> Why do we have more trust in the external VR than the internal VR?
> Experience? Known design differences? Perhaps I'm missing something
> fundamental. Curious minds want to know! :)
>
> --------
> Mickey Coggins
> http://www.rv8.ch/
>
> In the Z diagrams, follow all the wires leaving the regulator. One of them
(the A terminal on the generic Ford model) goes through the alternator half
of the master switch, to a 5A breaker, which is tied to the main buss. The
5A breaker supplies the regulator with its power. So with external
regulators, you're removing the only source of electrons to the field by
completely removing power from the regulator. This also prevents letting
additional smoke out if the regulator 'guts' are shorted to ground
internally.
Message 5
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| Subject: | Re: Interesting thread on overvoltage event |
ceengland7(at)gmail.com wrote:
> In the Z diagrams, follow all the wires leaving the regulator. One of them (the
A terminal on the generic Ford model) goes through the alternator half of the
master switch, to a 5A breaker, which is tied to the main buss. The 5A breaker
supplies the regulator with its power. So with external regulators, you're
removing the only source of electrons to the field by completely removing power
from the regulator. This also prevents letting additional smoke out if the
regulator 'guts' are shorted to ground internally.
Duh - now I get it - the light has turned on! [Idea] Thanks!
--------
Mickey Coggins
http://www.rv8.ch/
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=468806#468806
Message 6
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| Subject: | Re: Interesting thread on overvoltage event |
At 08:56 AM 4/26/2017, you wrote:
>
>
>ceengland7(at)gmail.com wrote:
> > In the Z diagrams, follow all the wires leaving the regulator.
> One of them (the A terminal on the generic Ford model) goes through
> the alternator half of the master switch, to a 5A breaker, which is
> tied to the main buss. The 5A breaker supplies the regulator with
> its power. So with external regulators, you're removing the only
> source of electrons to the field by completely removing power from
> the regulator. This also prevents letting additional smoke out if
> the regulator 'guts' are shorted to ground internally.
>Duh - now I get it - the light has turned on! [Idea] Thanks!
What you have 'discovered' is the process
by which an FMEA is accomplished. You study
power, control, and potential fault paths
for EVERY component in a system . . . to deduce:
a. How can this part fail?
b. If it fails, how will I know it?
c. Can it fail in a 'hidden' condition . . .
with a potential for misery in the cockpit?
-or-
d. is the failure pre-flight detectable?
e. if it does fail, what are the consequences
and what's the most elegant path to
resolution?
Unlike the reliability studies that
endeavor to build confidence in numbers
that may or may not have practical
validity (who tests batches of components
for a million hours?), the FMEA assumes
that EVERY part WILL fail.
Then the system integrator figures out how
to mitigate that failure . . . i.e. PLAN-B.
I've seen massive spread sheets that go into
minute detail on every little component or
feature in a system wherein the author proudly
announces "Eureka! We have achieved MTBF
Nirvana!"
I find it takes a tiny fraction of the time
and effort to conduct and resolve a simple
FMEA that offers a demonstrable degree of
probability for comfortable termination
of flight.
Congrats my friend with the hopes that
this new insight will serve you well . . .
Bob . . .
Message 7
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| Subject: | Re: Is a battery contactor really needed? |
It's been a couple of years since I designed my plane's electrical system with
no battery contactor.
What brand or style battery contactor is preferred/acceptable for a OBAM airplane
with a Z - (x) wiring system? I installed the barrel style starter contactor
but replaced it with the flat style when Bob recommended that change. Now I'm
wondering if there's a new style of battery contactor that has superseded the
barrel style.
One advantage to eliminating the battery contactor is keeping the voltage available
for starting that would be lost to the battery contactor.
Eric - W10 with Z-8 inspired elec system.[/u]
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=468812#468812
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| Subject: | Re: Interesting thread on overvoltage event |
Yes, thanks.
Told myself something wrong once and believed it ever after.
Jan de Jong
On 4/15/2017 2:38 PM, MMiller wrote:
> <mmill@optonline.net> In a PM generator like the Rotax, frequency is
> not a function of the number of coils in the stator, it's a function
> of the number of magnets in the rotor divided by two. Divided by two
> because the magnets are installed in the rotor with the poles
> alternating. Just look at the flux lines of one circuit. Two magnets
> in series inducing a field through the laminated stator of two coils.
> The two coils are connected in series with one of the coils "crossed"
> so the magnetic effect is additive.
Message 9
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| Subject: | Re: Is a battery contactor really needed? |
At 09:39 AM 4/26/2017, you wrote:
>
>It's been a couple of years since I designed my plane's electrical
>system with no battery contactor.
>
>What brand or style battery contactor is preferred/acceptable for a
>OBAM airplane with a Z - (x) wiring system? I installed the barrel
>style starter contactor but replaced it with the flat style when Bob
>recommended that change. Now I'm wondering if there's a new style of
>battery contactor that has superseded the barrel style.
The 'whisky barrel' style contactors have
a track record that goes back nearly 100
years. Process and materials improvements
have been applied throughout that time . . .
they are of excellent value.
The recommended change for starter contactors
was based on the fact that even low duty-cycle
whisky-barrel devices featured large area, low
pressure contact surfaces compared to the
more modern devices designed specifically for
starter control. But assuming you've got a
Plan-B in place for managing a battery contactor
failure (or its wiring, switch, terminals, etc)
then the style is of little significance.
If it were my airplane, the battery contactor
would be one of these . . .
http://tinyurl.com/koq788n
. . . or its several cousins.
Contactor failure in the whisky-barrel styles
is rare and it usually announces an impending failure
with finicky starter performance. So the first time
you get an intermittent starter behavior accompanied
by a black panel or 'chattering' starter contactor,
then it's time to replace the critter (assuming your
battery satisfactorily passes cap and load tests).
>One advantage to eliminating the battery contactor is keeping the
>voltage available for starting that would be lost to the battery contactor.
energy demands of a battery contactor
are trivial compared with that required
to energize the starter . . . hence
no energy conservation benefits there . . .
Bob . . .
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