Today's Message Index:
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1. 05:28 AM - Re: PM Alternator filter Capacitor - best practices (Robert L. Nuckolls, III)
2. 05:28 AM - Re: PM Alternator filter Capacitor - best practices (Robert L. Nuckolls, III)
3. 08:56 AM - Re: PM Alternator filter Capacitor - best practices (Tundra10)
4. 04:08 PM - Re: PM Alternator filter Capacitor - best practices (John Loram)
5. 08:15 PM - Re: Re: PM Alternator filter Capacitor - best practices (Robert L. Nuckolls, III)
6. 09:28 PM - Extending thermocouple leads (Radioflyer)
Message 1
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| Subject: | PM Alternator filter Capacitor - best practices |
At 10:18 PM 8/1/2012, you wrote:
So we're not trying to control the bandwidth of the regulator loop
with the cap? Does the battery do that? Guess I don't really know
what the frequency response of a lead-acid battery is. Probably
dependent on the state of charge and the condition of the battery.
And the load varies all over the place, both real and imaginary
components.... What would it look like with and without the cap if
the battery were out of the loop? ... Scary!
http://tinyurl.com/bqa6q9p
Finely tuned loop dynamics with these regulators is wishful
thinking. Here's an exemplar schematic for a PM regulator:
http://tinyurl.com/bwomjjz
I split out the two functions (regulation and
warning light)
http://tinyurl.com/c8usyw2
http://tinyurl.com/c6doa97
As you can see in the v-reg schematic,
there are no reactive components that
would shape closed-loop response. A battery
is a very poor 'filter' . . . it delivers
energy at 12.5 and below . . . accepts
energy at 13.8 and above. That's about
1.3 volts of span where the battery is
dynamically 'unhooked'.
It stands to reason that the capacitor
would have the greatest effect when the
alternator set point was too low (under
14.5) and the system was lightly loaded.
I'm running 3 phase (old Jab 3300).
Interesting. I think your regulator is
still quite similar . . . it just adds
another diode/scr pair.
Once I get this thing fired up I'll run some tests and let you know
what happens...
I have a fast switching, dynamic load bank
I built for tests at HBC some years back.
It would be interesting to use it along
with a data acquisition system on the
test bench to explore the closed loop
response of these systems.
Just thinking out loud, -john-
p.s. ran into a message the other day that you wrote back in 2007.
Said you worked for H.L Yoh as a civilian instructor in the early
60's... Same here! At the Naval ETA school on Treasure Island. Wasn't
that fun. I learned more electronics in six months instructing those
kids than four years of collage!
You got that right! I was teaching in the
top 4 weeks of a 26 week school at Great
Lakes. I went to work on a Friday and they
handed me a syllabus for my first section
of students along with a copy of "the bible",
Termnan's Electrical Engineering Handbook
http://tinyurl.com/cbvvjx9
and said, "you get your first class of 20
next Monday." As long as I stayed a day ahead
of the class . . . things went well . . .
and yes, a lot of fun. After four or
so passes through the class materials and
figuring out a half dozen ways to explain each
concept, it sorta creeps into your DNA. There's
no better way to learn something than to
be chartered to teach it.
Do you have access to a fast data acquisition
system that you could hook to your bus for
some hard data gathering?
I've used cousins to this critter . . .
http://tinyurl.com/3jtrxx4
on several tasks at HBC with great results.
Being able to jump on an airplane and get
hard data in flight without having to involve
a dozen folks from the instrumentation lab
was a powerful tool.
You might consider getting one of these
and use it to graph some of the performance
qualities of your system. It would be a great
augmentation of my ripple studies.
Bob . . .
Message 2
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| Subject: | PM Alternator filter Capacitor - best practices |
At 10:18 PM 8/1/2012, you wrote:
So we're not trying to control the bandwidth of the regulator loop
with the cap? Does the battery do that? Guess I don't really know
what the frequency response of a lead-acid battery is. Probably
dependent on the state of charge and the condition of the battery.
And the load varies all over the place, both real and imaginary
components.... What would it look like with and without the cap if
the battery were out of the loop? ... Scary!
http://tinyurl.com/bqa6q9p
Finely tuned loop dynamics with these regulators is wishful
thinking. Here's an exemplar schematic for a PM regulator:
http://tinyurl.com/bwomjjz
I split out the two functions (regulation and
warning light)
http://tinyurl.com/c8usyw2
http://tinyurl.com/c6doa97
As you can see in the v-reg schematic,
there are no reactive components that
would shape closed-loop response. A battery
is a very poor 'filter' . . . it delivers
energy at 12.5 and below . . . accepts
energy at 13.8 and above. That's about
1.3 volts of span where the battery is
dynamically 'unhooked'.
It stands to reason that the capacitor
would have the greatest effect when the
alternator set point was too low (under
14.5) and the system was lightly loaded.
I'm running 3 phase (old Jab 3300).
Interesting. I think your regulator is
still quite similar . . . it just adds
another diode/scr pair.
Once I get this thing fired up I'll run some tests and let you know
what happens...
I have a fast switching, dynamic load bank
I built for tests at HBC some years back.
It would be interesting to use it along
with a data acquisition system on the
test bench to explore the closed loop
response of these systems.
Just thinking out loud, -john-
p.s. ran into a message the other day that you wrote back in 2007.
Said you worked for H.L Yoh as a civilian instructor in the early
60's... Same here! At the Naval ETA school on Treasure Island. Wasn't
that fun. I learned more electronics in six months instructing those
kids than four years of collage!
You got that right! I was teaching in the
top 4 weeks of a 26 week school at Great
Lakes. I went to work on a Friday and they
handed me a syllabus for my first section
of students along with a copy of "the bible",
Termnan's Electrical Engineering Handbook
http://tinyurl.com/cbvvjx9
and said, "you get your first class of 20
next Monday." As long as I stayed a day ahead
of the class . . . things went well . . .
and yes, a lot of fun. After four or
so passes through the class materials and
figuring out a half dozen ways to explain each
concept, it sorta creeps into your DNA. There's
no better way to learn something than to
be chartered to teach it.
Do you have access to a fast data acquisition
system that you could hook to your bus for
some hard data gathering?
I've used cousins to this critter . . .
http://tinyurl.com/3jtrxx4
on several tasks at HBC with great results.
Being able to jump on an airplane and get
hard data in flight without having to involve
a dozen folks from the instrumentation lab
was a powerful tool.
You might consider getting one of these
and use it to graph some of the performance
qualities of your system. It would be a great
augmentation of my ripple studies.
Bob . . .
Message 3
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| Subject: | Re: PM Alternator filter Capacitor - best practices |
So should the capacitor and 1K resistor be deleted from Z13/8 ?
Note 20 indicates the purpose of the capacitor is to smooth the voltage if the
battery is offline. However, there is no intentional way of disconnecting the
battery, and there are very few failures that could result in the battery being
disconnected while the SD-8 still remains connected to the battery bus.
In Z13/8 the SD-8 is only turned on in the event of a main alternator failure.
Maybe in this circumstance, a little noise in the audio is not significant to
the completion of the flight (assuming the capacitor actually helps in a given
installation).
Jeff Page
Dream Aircraft Tundra #10
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=379872#379872
Message 4
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| Subject: | PM Alternator filter Capacitor - best practices |
Thank you for the schematics. Most instructive!
>
> p.s. ran into a message the other day that you wrote back in 2007.
> Said you worked for H.L Yoh as a civilian instructor in the
> early 60's... Same here! At the Naval ETA school on Treasure
> Island. Wasn't that fun. I learned more electronics in six
> months instructing those kids than four years of collage!
>
> You got that right! I was teaching in the
> top 4 weeks of a 26 week school at Great
> Lakes. I went to work on a Friday and they
> handed me a syllabus for my first section
> of students along with a copy of "the bible",
> Termnan's Electrical Engineering Handbook
>
> http://tinyurl.com/cbvvjx9
And thank you for Villard's Memoir. I loved reading every bit of it!
Like every self-respecting EE I have kept my copy of Terman.
>
> and said, "you get your first class of 20
> next Monday." As long as I stayed a day ahead
> of the class . . . things went well . . .
> and yes, a lot of fun. After four or
> so passes through the class materials and
> figuring out a half dozen ways to explain each
> concept, it sorta creeps into your DNA. There's
> no better way to learn something than to
> be chartered to teach it.
>
And in every other class you'd get one 'ringer'. A kid fresh out of
engineering school who would nail you to the chalk board at the slightest
slip-up!!! You either got those guys on your side right away or you were in
for some tough sledding!
> Do you have access to a fast data acquisition
> system that you could hook to your bus for
> some hard data gathering?
>
> I've used cousins to this critter . . .
>
> http://tinyurl.com/3jtrxx4
I have a couple of these first generation DI-148Us.
It will run at 11 KHz sampling rate on one channel.
Tell me more about your dynamic load bank. Sounds like just the ticket.
>...
> You might consider getting one of these
> and use it to graph some of the performance
> qualities of your system. It would be a great
> augmentation of my ripple studies.
>
>
> Bob . . .
>
>
I'd be happy to contribute!
I'm probably a month away from first start and another month coming down off
the high!!, -john-
Message 5
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| Subject: | Re: PM Alternator filter Capacitor - best practices |
At 10:55 AM 8/2/2012, you wrote:
So should the capacitor and 1K resistor be deleted from Z13/8 ?
Don't delete anything. We're having a discussion
about the notion that data gathered on an SD-8 with
a 'scope about 10 years ago doesn't confirm legacy
beliefs about what a capacitor across a power supply
does for us.
This capacitor MAY have some value in fast, low
energy transient mitigation and/or regulation
dynamics. John and I will continue to ponder
"out loud on the List" but don't take any
hypothesis as cause to rise up and evict
your capacitor.
The capacitor AND 1K resistor are also participants
in the self excitation system.
Note 20 indicates the purpose of the capacitor is to smooth the
voltage if the battery is offline. However, there is no intentional
way of disconnecting the battery, and there are very few failures
that could result in the battery being disconnected while the SD-8
still remains connected to the battery bus.
In Z13/8 the SD-8 is only turned on in the event of a main alternator
failure. Maybe in this circumstance, a little noise in the audio is
not significant to the completion of the flight (assuming the
capacitor actually helps in a given installation).
Good questions/suppositions all . . . we'll
endeavor to sort it out with greater
clarity.
Bob . . .
Message 6
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| Subject: | Extending thermocouple leads |
I think I understand how to do things right with thermocouples, but want to make
sure. I have a set of (GRT/EIS) J- type, CHT bayonet thermocouples. The 2 foot
leads are terminated from the factory in what I believe to be standard spade
terminals. I need to lengthen these leads about 12 feet to reach my MGL Avionics
quad CHT display instrument. So I plan to get some J-type wire, crimp on
some mating spade terminals and similarly terminate the other end very close to
the instrument. (One set of spades will be in the hot engine compartment and
the spades on the other end of the extension will be in the cabin.)
My understanding is that the parasitic couples at the spade terminals will be cancelled
out, so I should get accurate temp readings at the instrument. Correct?
Is it worth the trouble to search for stranded J-wire or is solid good enough?
--Jose
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=379921#379921
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