Today's Message Index:
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1. 07:02 AM - PM alternator (BobbyPaulk@comcast.net)
2. 08:38 AM - Re: Alternator (FLYaDIVE)
3. 09:24 AM - Re: Alternator (Robert L Nuckolls III)
4. 09:55 AM - Re: Alternator (Rob Turk)
5. 11:13 AM - Re: Alternator (Robert L Nuckolls III)
Message 1
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Bob,
I always thought the PM Alt was capable of more. The 6 burned coils kinda proved
that - to me anyway.
I was hoping the higher voltage at a lower rpm would make the R / R more efficient
and I could gain a few more amps at the lower rpm.
Anyway I would be interested in any new developments for a better R /R if you get
into that aspect. I also subscribe to your AeroElectric list.
Bobby
Message 2
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Right you are Bob N.!
Things will NOT change until many more 'builders'... Not Engineers, come
to the realization that: You can't fool Mother Physics! Physics is what it
is and no matter how much hoping and praying you do, you CAN'T change it!
When this issue first came up years ago I posted something like: You can't
get blood from a stone and why not just install a small AUTOMOTIVE
alternator with built in ACU! All sorts of responses surfaced... I don't
want to loose the extra HP the alternator will require. Too much weight.
What do I do with the built in unit... DUH! Remove it! The only
acceptable response was: I don't have room to install it - No room under
the cowl. Now, here I have feeling for the poor builder.
Small alternators such as the MITSUBISHI are as small a large man's hand
and put out 40 to 70 Amps. Simple, easy to install, easy to diagnose, easy
to regulate (built in), easy to replace if you breakdown at a remote
airport... Just SIMPLY EASY! So, why kill yourself trying to get blood
from a stone? And I like Jabiru Engines... I hate Rat-Tax (Rotex).
Barry
On Mon, Apr 27, 2015 at 6:21 PM, Robert L Nuckolls III <
bob.nuckolls@aeroelectric.com> wrote:
> bob.nuckolls@aeroelectric.com>
>
> At 15:39 2015-04-27, you wrote:
>
>> List
>> I was getting 14.6 volts steady at 1200 and 1400 rpm while taxiing out.
>> My amp meter hunts so I do not know what it was putting out ( Zero to 4
>> indicated ). After the first flight that had Icom radio, Dynon Efis, and
>> the Ro-tec E mag I figured about five to seven amps with the radio not
>> transmitting. The volt meter was still steady at 14.6.
>> One thing I did observe was when I put the battery tender on it it only
>> took about 10 minutes or less for the green light to come on. It usually
>> takes 25 to 30 minutes.
>> I believe the coils shorted out when I added load by turning on the
>> strobes. After I removed the coils it looks like the varnish could have
>> been rubbed off at the corner of the turn where the wires exit to the
>> backside of the coils. I could not really tell since the wire was blackened
>> and had no varnish left.
>> One circuit was burned black ( all 6 coils ) while the other circuit was
>> in tact.
>> I knew it was a trade off by going to one series circuit in lieu of the 2
>> parallel but I was used to turning off the transponder on short final and
>> the strobes after exiting the runway ( unless there was ground traffic).
>> Anyway I am afixin to order the CAMit 40 ~ 45 amp alternator and adapter
>> kit. That ought to fix the problem unless I have another self induced uh-oh!
>>
>> Thanks to all that responded ( no flames : )
>>
>> bobby
>>
>
>
> Sadly, your observations on the series-connected
> alternator 'experiment' were somewhat predictable.
> Sorry you've had to suffer the indignities imposed
> by the laws of physics.
>
> The PM alternator has been poorly exploited for the
> best it has to offer. PM alternators are simple, long
> lived, robust and not terribly inefficient. Unfortunately,
> the rectifier/regulator combinations have NOT evolved
> with the best that power electronics has to offer.
>
> We're doing the rudimentary proof of concept studies
> for a PM alternator R/R that will offer greater
> maximum output commensurate with the alternator's
> real ability to convert mechanical motion into
> electrical energy.
>
> The belt driven alternator is a low-risk albeit
> heavier and more expensive alternative. It may indeed
> be the most practical solution depending on you
> use your airplane.
>
> But it's possible that a modern R/R configuration will
> breath new life into the PM alternator concept with
> increased performance and system reliability.
>
> We shall see .. .
>
>
> Bob . . .
>
>
> -----------------------------
> Bob Nuckolls
> AeroElectric Connection
> P.O. Box 130
> Medicine Lodge, KS 67104-0130
> Mobile: 316-209-7528
> Web: http://aeroelectric.com
> ------------------------------
>
>
Message 3
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At 10:37 2015-04-28, you wrote:
>Right you are Bob N.!
>
>Things will NOT change until many more 'builders'... Not Engineers,
>come to the realization that: You can't fool Mother
>Physics! Physics is what it is and no matter how much hoping and
>praying you do, you CAN'T change it!
>
>When this issue first came up years ago I posted something
>like: You can't get blood from a stone and why not just install a
>small AUTOMOTIVE alternator with built in ACU! All sorts of
>responses surfaced...
To be sure, the universe runs on physics and
no matter what discipline one plies their
talents, it all comes down to properties of
materials and management of energy.
The evolution of the PM alternator has roots
on small bikes and RV's like snow-mobiles. They
often mounted a "lighting coil" on the crankcase
and spun a magnet close by to offer perhaps 20-30
watts of AC to light a headlamp.
The ghost of F. Kettering must have been smiling
down on the endeavor as individuals began to
ponder ways that the headlamp intensity could
be maintained over full range of engine rpm . . .
not limited to full bright at open throttle.
So the simple rectifier/regulator came along
with a crude voltage control profile that
prevented serious overcharging of the battery.
Keep in mind that ALL this was before rare
earth and SLVA technologies.
Yeah . . . it kinda worked okay. The regulators
were simple silicon controlled rectifiers that
were 'fired' as a dead short across the alternator
when the bus voltage got too high. Hence, the
alternator was fully loaded all the time. Furhter
it had to be inherently current limiting to keep
it from smoking when there were no system loads
and the battery was fully charged.
Then came rare earth magnets. About the same
time, SLVA batteries pushed their flooded
ancestors into a timely and well deserved
place in history. A new breed of R/R came along
which formed a bridge rectifier with SCR's in
two legs of the bridge for control by some
rudimentary electronics.
Again, not the best we knew how to do but
ADEQUATE to contemporary design goals. Examples
example of this now dated technology include
the successes logged by Rotax, B&C (The SD-8
was B&C's first product. I was a collaborator
on that development and helped them purchase
the sand-castings for Electro-Mech standby
generators for Bonanza's AND20000 pad
drive pad).
The improved alternators benefited from rare
earth, So while AVAILABLE AC power from
the alternator went up . . . DC power demands
on the airplanes being built went up too.
Sadly, the R/R did not evolve with the power
electronics side of the house.
There has never been anything inherently EVIL
or even grossly7 inept about the participants
in this saga. Each feature from alternator
to R/R, to battery, to evolution of the
all-electric OBAM aircraft was plotting along
with each technology driven by separate
marketing and business models most of which
hand nothing to do with the unique electrical
environment that was evolving on OBAM aircraft.
As a 45+ year observer and participant in art
and science of systems design and fabrication,
I can offer historical narrative above and
propose the next big step in the evolution
of the PM alternator as a practical, engine
driven power source.
The efficiency of the legacy triggered-bridge
rectifier is terrible. I judge that these
designs not only cripple the system's ability
to deliver at low rpm and may toss off 20
to 50% of total available energy as heat.
The next step borrows from the energy management
technologies ubiquitous in computers for decades.
In the mean time, I would be cautious about
bad-mouthing the PM alternator. Shortcomings
in performance had little to do with design
of the alternator and MUCH to do with design
of the R/R.
Did some development testing at B&C last week.
Will probably be back there again this week.
The ingredients that go into this recipe for
success have existed for decades . . . it's
a matter of picking the right combination . . .
for properties of materials and management of
energy.
Bob . . .
-----------------------------
Bob Nuckolls
AeroElectric Connection
P.O. Box 130
Medicine Lodge, KS 67104-0130
Mobile: 316-209-7528
Web: http://aeroelectric.com
------------------------------
Message 4
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You said it, Bob. Modern technology switching regulators allow for wide
input and constant output with high reliability, high efficiency and low
weight.
On a Jabiru, a switching regulator must be designed to work with ~5:1
input range (minimum 7 volt AC @ 700rpm, maximum 35V@3300rpm.). The
original windings are designed to deliver 20A, so at cruise of 2700rpm
(~28V) it should deliver close to 500W of electrical power. If you'd use
an efficient switcher you can get ~85-90% available, which translates to
almost 30A@14.6V. Plenty for all but a flying Christmas tree. Oh, and a
switching regulator would make it possible to go to a 28V system as
well, saving weight on wiring.
Only concern I'd have with these is RF interference, these switchers
aren't particularly clean..
Rob
On 4/28/2015 6:23 PM, Robert L Nuckolls III wrote:
> <bob.nuckolls@aeroelectric.com>
>
> ...
> The next step borrows from the energy management
> technologies ubiquitous in computers for decades.
> In the mean time, I would be cautious about
> bad-mouthing the PM alternator. Shortcomings
> in performance had little to do with design
> of the alternator and MUCH to do with design
> of the R/R.
>
> Did some development testing at B&C last week.
> Will probably be back there again this week.
> The ingredients that go into this recipe for
> success have existed for decades . . . it's
> a matter of picking the right combination . . .
> for properties of materials and management of
> energy.
>
>
> Bob . . .
>
>
> -----------------------------
> Bob Nuckolls
> AeroElectric Connection
> P.O. Box 130
> Medicine Lodge, KS 67104-0130
> Mobile: 316-209-7528
> Web: http://aeroelectric.com
> ------------------------------
>
>
Message 5
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At 11:54 2015-04-28, you wrote:
>
>You said it, Bob. Modern technology switching regulators allow for
>wide input and constant output with high reliability, high
>efficiency and low weight.
>
>On a Jabiru, a switching regulator must be designed to work with
>~5:1 input range (minimum 7 volt AC @ 700rpm, maximum 35V@3300rpm.
The 5:1 range target assumes that the alternator's
maximum rated ENERGY output is uniform over the
range of RPM . . . which it is not.
>. The original windings are designed to deliver 20A, so at cruise of
>2700rpm (~28V) it should deliver close to 500W of electrical power.
What gage wire is used to wind those stators?
> If you'd use an efficient switcher you can get ~85-90% available,
> which translates to almost 30A@14.6V. Plenty for all but a flying
> Christmas tree. Oh, and a switching regulator would make it
> possible to go to a 28V system as well, saving weight on wiring.
Based on the present state of development studies,
I would expect a pretty good boost at cruise RPM
perhaps as much as 50% over present capabilities.
I would also expect USEFUL output to MUCH lower
rpm levels than with the current technology. But
hundreds of watts at idle is not in the cards
without some re-design of the alternators. That
would be the next phase of system upgrades.
>Only concern I'd have with these is RF interference, these switchers
>aren't particularly clean..
Switchmode regulators are widely used in a host
of RFI sensitive environments. There is NO design
that cannot be tailored to the most critical of
EMC environments.
I have desktop, consumer grade computer power supplies
sitting right next to amateur radio equipment capable
of sniffing microvolt level signals. I'm not suggesting
that there aren't occasional 'birdies' but I've yet
to be plagued by any of them. Got a nice HF transceiver
I'll be putting into service as soon as I can get a new
antenna up . . . I'll see if I need to modify those words.
In any case, there's a LOT of computers co-existing in
ham radio shacks . . . it can be done.
Bob . . .
-----------------------------
Bob Nuckolls
AeroElectric Connection
P.O. Box 130
Medicine Lodge, KS 67104-0130
Mobile: 316-209-7528
Web: http://aeroelectric.com
------------------------------
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