Today's Message Index:
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1. 05:19 AM - Re: alternator (Robert L Nuckolls III)
2. 05:41 AM - Alternator and gauge (BobbyPaulk@comcast.net)
3. 10:21 AM - Re: alternator (Rob Turk)
4. 03:40 PM - Re: alternator (Robert L Nuckolls III)
5. 03:42 PM - Re: alternator (Robert L Nuckolls III)
Message 1
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At 15:51 2015-04-24, you wrote:
CAMit for sure. As you say, they know the engine very well (they
built them for many years) and today sell new engines with just this
alternator setup.
The aluminium spider needs to come off to change the belt, but that
should be easy with the old alternator parts removed, and only a
once-every-500-hours job.
Rob
On 4/24/2015 10:04 PM, BobbyPaulk@comcast.net wrote:
List,
I have two flights of about 30 minutes each on my Jabiru 3300 after
some repairs and a couple of modifications.
I changed the Alternator coils from 2 parallel circuits to 1 series
circuit in accordance with Jabiru AVDALSR-087-1. It was working fine
on the first flight and most of the second flight. Output was 14.6
volts while taxiing out. Halfway thru the second flight I turned on
strobe lights to put a load on the alternator. I figure I was drawing
no more than 11 amps. When I reduced power to enter downwind I
smelled wires burning and noticed the battery voltage was down to
12.2. I turned off the strobes and landed.
On inspection I found every other coil ( 6 ) in the alternator burned
black and the alternator no longer worked.
I am not going back with the original magnet / stator dynamo.
My question to the list is whether to go with the CAMit alternator or
the Rotec. I am leaning toward the CAMit version since they are very
familiar with the Jabiru / CAMit Engine.
Does anyone know if the belt on either one can be changed without
removing the aluminum back plate?
I was astounded to learn of what was touted to be
a 'Jabiru recommendation' to series up the windings
on the alternator for 'improved performance'.
This has the effect of DOUBLING the alternator's
AC output voltage . . . and yes, you'll see
improved bus voltage readings at low rpm.
To paraphrase the astute observation by one
of my favorite authors, "There ain't no such
thing as a free lunch."
Moving from parallel connection to series
connection doubles output voltage while
cutting current delivery capability by more
than 1/2. I.e. the POWER available from the
alternator is unchanged but delivered at
a higher voltage with lower current capability.
There ARE regulator designs which would exploit
virtually ALL the ENERGY available from the
alternator at ANY practical voltage.
In the legacy rectifier/regulator, current
flowing in alternator windings is a mirror
of that flowing out of the R/R. Rewiring the alternator
while retaining the legacy regulator is all
but guaranteed to produce the observed results.
Going from parallel to series COMBINED with an
upgrade of regulator technology would be a very good
thing to contemplate.
I'm having trouble believing that Jabiru
engineers made such a recommendation; I'll
bet it came from somebody down the distribution
chain. In any case, ill-conceived. Replacing
the alternator with a belt-driven, automotive
derivative is also a practical option.
Bob . . .
-----------------------------
Bob Nuckolls
AeroElectric Connection
P.O. Box 130
Medicine Lodge, KS 67104-0130
Mobile: 316-209-7528
Web: http://aeroelectric.com
------------------------------
Message 2
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| Subject: | Alternator and gauge |
Thanks to Dave and Rob for the info.
I was aware of the pressure sensor reading on the very low end of it's range so
I will set the low alarm to 1.5 PSI indicated and watch carefully.
Also I will be ordering the CAMit Alternator.
Thanks again
bobby
Message 3
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Hello Bob,
As astounding as it sounds, this mod indeed comes from the Jabiru
factory themselves. Run a search for AVDALSR87 on Google and you will
find the PDF listed as the first hit, direct from the Jabiru site. There
is a second version (AVDALSR87-2) with a bit more explanation around,
but nowhere does either version mention the loss of current delivery
capability. It just touts the ability to charge the battery at near-idle
speeds. Several people asked Jabiru about it and they claimed no loss of
power from this mod.
Considering the same current draw from the plane's electric system and
the internal losses (= heat) in the alternator coil quadrupling at equal
current draw with this mod (going from 1/2R to 2R), it is no surprise
the coil will burn up.
The belt driven alternative has two positive effects. First, there's
more electrical power available, also at low idle speed. Second, the
belt drive dampens torque pulses which helps keep the flywheel bolts
intact. Definitely te way to go.
Rob
> I was astounded to learn of what was touted to be
> a 'Jabiru recommendation' to series up the windings on the alternator
> for 'improved performance'. This has the effect of DOUBLING the
> alternator's AC output voltage . . . and yes, you'll see improved bus
> voltage readings at low rpm.
>
> To paraphrase the astute observation by one of my favorite authors,
> "There ain't no such thing as a free lunch."
>
> Moving from parallel connection to series connection doubles output
> voltage while cutting current delivery capability by more than 1/2.
> I.e. the POWER available from the alternator is unchanged but
> delivered at a higher voltage with lower current capability.
>
> There ARE regulator designs which would exploit virtually ALL the
> ENERGY available from the alternator at ANY practical voltage.
>
> In the legacy rectifier/regulator, current flowing in alternator
> windings is a mirror of that flowing out of the R/R. Rewiring the
> alternator while retaining the legacy regulator is all but guaranteed
> to produce the observed results.
>
> Going from parallel to series COMBINED with an upgrade of regulator
> technology would be a very good thing to contemplate.
>
> I'm having trouble believing that Jabiru engineers made such a
> recommendation; I'll bet it came from somebody down the distribution
> chain. In any case, ill-conceived. Replacing the alternator with a
> belt-driven, automotive derivative is also a practical option.
>
>
> Bob . . .
Message 4
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At 11:00 2015-04-25, you wrote:
>Hello Bob,
>
>As astounding as it sounds, this mod indeed comes from the Jabiru
>factory themselves. Run a search for AVDALSR87 on Google and you
>will find the PDF listed as the first hit, direct from the Jabiru
>site. There is a second version (AVDALSR87-2) with a bit more
>explanation around, but nowhere does either version mention the loss
>of current delivery capability. It just touts the ability to charge
>the battery at near-idle speeds. Several people asked Jabiru about
>it and they claimed no loss of power from this mod.
That's sad . . . but I guess not a great surprise.
More and more companies have become so siloed and
victim to the 'let's farm that out' syndrome that
they loose command and control over critical aspects
of their products.
>Considering the same current draw from the plane's electric system
>and the internal losses (= heat) in the alternator coil quadrupling
>at equal current draw with this mod (going from 1/2R to 2R), it is
>no surprise the coil will burn up.
Agreed.
>The belt driven alternative has two positive effects. First, there's
>more electrical power available, also at low idle speed. Second, the
>belt drive dampens torque pulses which helps keep the flywheel bolts
>intact. Definitely te way to go.
Yeah . . . but that PM alternator is so damned simple,
elegant and robust. With the right electronics, it COULD
be a significant ingredient in the recipe for success.
Rotax too . . .
I'm working on that . . .
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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Can anyone on the list give me a measurement of
AC volts developed by the stock, parallel wound
3300 PM alternator at idle speed. Need to know what
that speed is too . . .
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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