Today's Message Index:
----------------------
1. 07:39 AM - Re: Revmaster R2300 PMA (dj_theis)
2. 08:35 AM - Re: Re: Revmaster R2300 PMA (Charlie England)
3. 09:05 AM - Re: Monarch EE Anti-Plugging Field Accelerating? (MMiller)
4. 09:57 AM - Re: Revmaster R2300 PMA (dj_theis)
5. 10:22 AM - Re: Re: Monarch EE Anti-Plugging Field Accelerating? (Robert L. Nuckolls, III)
6. 11:23 AM - Re: Re: Revmaster R2300 PMA (Robert L. Nuckolls, III)
7. 02:53 PM - RV10 Electrical System Safety (WILLIAM BOOTH)
8. 07:16 PM - RV10 Electrical System Safety & Operational Issues (WILLIAM BOOTH)
9. 07:21 PM - RV10 Electrical Issues (WILLIAM BOOTH)
Message 1
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| Subject: | Re: Revmaster R2300 PMA |
As I re-read my post from last night I realized it was too long and missing some
key information. Not to mention a few errors in the text.
There are two issues here. My intent to show the difference in performance of
a wet lead acid battery charge vs an AGM. The second is to try and expose the
failure mode of the Revmaster alternator.
First, some clarity. The scope trace was my first step to compare a lead acid
battery to an AGM. I'll repeat the scope trace and post this weekend the "loaded"
lead acid battery charge curve with a loaded AGM charge curve, using the
JD alternator and RR previously shown. Attached is the summary of the Kv curve
and charging with the (pretty much) fully charged wet cell battery. Note tha
the currents are "Peak" and not RMS. the half wave rectified amperage curve
peak values are dramatically larger than the RMS values. I will include RMS
calculations (that my scope can do) with the loaded charge system curves I'll
publish this weekend.
A few errors and ommissions I need to correct.
Only the red scope trace from my previous post (channel B) was a 10x probe.
With regard to the image of the burned stator:
> I find it more than interesting that only one of the coils making up the left
stator is burned while the other 4 appear perfect.
This should have read "right stator" not left.
Hope this helps a bit.
Dan Theis
--------
Scratch building Sonex #1362
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=500080#500080
Attachments:
http://forums.matronics.com//files/jd_am877577_peak_charge_amps_with_unloaded_wet_cell_542.pdf
http://forums.matronics.com//files/jd_am877577_ocv_664.pdf
Message 2
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| Subject: | Re: Revmaster R2300 PMA |
On 1/8/2021 9:35 AM, dj_theis wrote:
>
> As I re-read my post from last night I realized it was too long and missing some
key information. Not to mention a few errors in the text.
>
> There are two issues here. My intent to show the difference in performance of
a wet lead acid battery charge vs an AGM. The second is to try and expose the
failure mode of the Revmaster alternator.
>
> First, some clarity. The scope trace was my first step to compare a lead acid
battery to an AGM. I'll repeat the scope trace and post this weekend the "loaded"
lead acid battery charge curve with a loaded AGM charge curve, using the
JD alternator and RR previously shown. Attached is the summary of the Kv curve
and charging with the (pretty much) fully charged wet cell battery. Note
tha the currents are "Peak" and not RMS. the half wave rectified amperage curve
peak values are dramatically larger than the RMS values. I will include RMS
calculations (that my scope can do) with the loaded charge system curves I'll
publish this weekend.
>
> A few errors and ommissions I need to correct.
>
> Only the red scope trace from my previous post (channel B) was a 10x probe.
>
>
> With regard to the image of the burned stator:
>
>
>> I find it more than interesting that only one of the coils making up the left
stator is burned while the other 4 appear perfect.
>
> This should have read "right stator" not left.
>
> Hope this helps a bit.
>
> Dan Theis
Hi Dan,
I read through the earlier post & looked at the images, though I didn't
download the pdf files. I'm certainly no expert, but my thought is that
what your friend said about internal shorting of the coil would be the
most likely failure mode. Heat within a coil would eventually cause
insulation to fail, and once an internal short occurs, there'd be an
avalanche of heat due to the lowered resistance in the shorter path
through the coil.
It seems to me that all the analysis in the world won't help solve the
problem if you can't do anything about the stator itself. Has anyone
done data logging on one of the failed stators prior to, and during, a
real-world in-use failure? Was it asked to deliver more current than the
rated current? Did the associated rectifier/regulator fail at the same
time, or did it survive, and continue to work correctly?
If the rectifier/regulators aren't failing, then you're left with either
an overload (this is what the mfgr is hinting at with the SLA
prohibition), or a rating number that isn't realistic for the stator's
environment (bolted directly to a hot engine block with near-zero airflow).
The brute force cure for stator survival would be to limit output
current with a *current* regulator, set to limit current below the
stator's *real world* capabilities, in its real world environment. The
prohibition on SLA batteries won't solve anything, in and of itself,
because a larger 'wet cell' battery (to achieve the same CCA) could
easily have the same internal resistance as the previous SLA. All
they're really saying is to limit the load current, but they're
apparently unwilling or unable to give a real world number on the
alternator's current capability, in its environment.
FWIW,
Charlie
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| Subject: | Re: Monarch EE Anti-Plugging Field Accelerating? |
That Field Acceleration relay is interesting. Based on its name I assume the relay
picks during acceleration. Its contact shunts the motor field resistance,
increasing motor torque. The coil has two windings, with the shunt winding across
the fixed exciter voltage and the series winding in the loop circuit. Looking
at the diagram the windings appear to be connected differentially so the higher
starting current picks the relay, once the motor is up to speed the loop
current falls and the differentially connected shunt coil neutralizes the series
coil, dropping the relay.
The speed regulation here is not magic. In a DC shunt motor;
armature voltage is proportional to speed.
armature current is proportional to load.
as you weaken the motor field, armature current will rise and RPM will increase.
In a ward Leonard system the motor and generator armatures are in a loop, the generator
will output voltage to the motor. The generator voltage is proportional
to the generator field current. The field current has two components the shunt
field and the series field. The shunt field is set by the operator with the
rheostat. The series field has the current of the motor load. As the motor load
increases loop current rises, generator field strength increases and the generator
output voltage will rise.
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=500082#500082
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| Subject: | Re: Revmaster R2300 PMA |
Thanks Charlie,
> It seems to me that all the analysis in the world won't help solve the
> problem if you can't do anything about the stator itself. Has anyone
> done data logging on one of the failed stators prior to, and during, a
> real-world in-use failure? Was it asked to deliver more current than the
> rated current? Did the associated rectifier/regulator fail at the same
> time, or did it survive, and continue to work correctly?
Fully agree. I am working on investigating alternatives (if the failure is primarily
due to insufficient vacuum impregnation of the coils). I will be continuing
to collect data on my engine before I run it and plan on continued data
collection during operation, should if fail.
I do not believe the associated RR failed during the event that led to the burned
coil. Also, I don't believe the 30 amp fuses failed either. This is one of
the reasons I was looking (and found) the explanation for the inter coil short
phenomenon.
In all failures, heat will contribute to the problem and I think there is a sever
lack of cooling of the stator. Something else I want to instrument and test
with my engine.
Dan Theis
--------
Scratch building Sonex #1362
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=500083#500083
Message 5
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| Subject: | Re: Monarch EE Anti-Plugging Field Accelerating? |
At 08:22 PM 1/7/2021, you wrote:
>
>Hi Bob
>Yes the speed control rheostats are on a common shaft.
>I found this link:
>https://www.practicalmachinist.com/vb/monarch-lathes/field-acceleration-relay-226109/
>
>I believe it's Field Accelerating that is the hocus pocus I never
>fully understood too much that I believe helps increase torque?
"acceleration" implies that this is a dynamic thing
in effect only during changes of velocity . . . either
increasing or decreasing. In this case, it's probably
only a feature of start-up acceleration is proportional
to rotational mass * torque.
Torque: T = k*Ia*Bf
proportional to armature current * field
flux.
Torque is proportional to field flux x armature
current . . . period. From published schematics,
we see no provisions for controlling armature
excitation . . . all speed control magic happens
with field excitation.
So to speed up the acceleration of this machine's
rotating mass, I'm suspecting that there's s
system in place to apply full field current during
the first tens of milliseconds after turn-on.
Take a peek at the attached exemplar DC
motor curve. Note that for a FIXED applied armature
voltage, motor performance is plotted by a straight
line running from max rpm at zero load to max torque
at zero rpm. This load line has SLOPE that is
defined by LOOP RESISTANCE. Add up all the resistance
for power supply source impedance, wires, brushes and
armature to get total loop resistance.
Divide that value into source voltage and you
get a value of absolute maximum current which
occurs at zero rpm (stall current) which is also
your start-up, inrush current.
Note that at zero rpm, max torque and stall the
available voltage is not changed. There is a FAMILY
of lines, parallel to the blue line that represent
a range of applied voltage. The slope is constant
as long as loop resistance is constant. Note the
yellow plot showing an increase in max rpm at zero
load; drop in torque (and stall current) at zero
rpm. This illustrates a 'hot' motor condition due
to increased resistance of the armature windings
due to temperature.
Let's consider another characteristic:
k
RPM ~ ------------
Bf
Speed is roughly inversely proportional to field flux.
So, if you want to get things moving right smartly,
you apply both full field and uncontrolled full
armature current. This will get you a speedy spin-up
to MINIMUM speed but at maximum torque.
You can then reduce field flux to bring the motor
up to operating speed at reduced torque.
This second characteristic offered a clever
means for controlling the speed of some pretty
beefy motors by fiddling with the relatively
minor field current(s).
>What is Base Speed?
That's a local vernacular probably unique
to the industry. We do know that at MAX
available voltage you get minimum operating
speed at maximum available torque . . . that
might well be the 'base speed'.
I have a lot of respect for the folks who designed
these machines. With no assist from electronics or
software, they squeezed an amazing amount of
functionality with 1930's technology. Examples
of similar intellectual agility include these
DC generator regulators
http://aeroelectric.com/Pictures/Regulators/Carbon_Pile_1a.jpg
http://aeroelectric.com/Pictures/Regulators/12VN7E_Delco-Remy_3.jpg
Then there's the second picture attached . . .
this piece of equipment is the size of a big
loaf of bread. It contains no electronics. Just
copper, Bakelite and steel. It contains 1 bit
comparators, analog-digital converters, etc. etc.
It's one of several controllers used to manage
a 1930's steam driven megawatt power plant.
The thought processes and talents that brought
your lathe into a practical reality are in the
same class.
Bob . . .
Un impeachable logic: George Carlin asked, "If black boxes
survive crashes, why don't they make the whole airplane
out of that stuff?"
Message 6
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| Subject: | Re: Revmaster R2300 PMA |
>
>The brute force cure for stator survival would be to limit output
>current with a *current* regulator, set to limit current below the
>stator's *real world* capabilities, in its real world environment.
>The prohibition on SLA batteries won't solve anything, in and of
>itself, because a larger 'wet cell' battery (to achieve the same
>CCA) could easily have the same internal resistance as the previous
>SLA. All they're really saying is to limit the load current, but
>they're apparently unwilling or unable to give a real world number
>on the alternator's current capability, in its environment.
Agreed. I've been pondering this thread periodically
for months. A possible contributor to 'single coil'
failures is the rather large positive temperature
coefficient of copper resistance.
Some months back we discussed the propensity for
a free-air span of copper wire to always burn
in two at or near center of the span . . . and
considered the effects of tempco on the physics
of the melt.
Once a single coil temperature rises above that
of its brothers, electrical energy dissipation within
that coil will climb above the rest with
a positive feedback.
It would be REALLY interesting/useful to mock up this
stator/rotor assembly on a vari-drive to get some
data. I'm not at all comfortable with the notion of
running ONE HALF of a system with demonstrated vulnerabilities
while keeping an equally inadequate half in reserve.
I'm thinking elegant solution might be to run BOTH
coils in a full-wave center tapped supply configuration
to a switchmode power supply fitted with accurate/stable
voltage regulation and calibrated current limiting.
Instead of walking a tight-rope of high probability
failure modes, designing a system that strives for
predictable stress limiting seems more in order.
Generators did it, alternators do it, why not a
PM alternator?
Bob . . .
Un impeachable logic: George Carlin asked, "If black boxes
survive crashes, why don't they make the whole airplane
out of that stuff?"
Message 7
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| Subject: | RV10 Electrical System Safety |
=EF=BBHey guys I am way in over my head on this forum but a nice man from
BandC suggested I try. Attached is the electrical diagram of my recently p
urchased RV10. It was completed in 2009 and the avionics was switched to a G
armin 900x a year later. My issue is it safe and operationally sound. It is
an =9C###=9DX=9D design; if that is familiar.
Apparently the builder added a =9Cbus tie=9D in order to bypass a
diode (bridge rectifier type) because the draw to recharge the =9CAux
Battery=9D (2 wheel chair batteries 7Ah 12v wired in series) reduced t
he essential bus voltage to 12.6v. This =9Cbus tie=9D when on bo
osts both busses back to 13.6v. Is this how it was meant to be run?
Additionally with both alternators on, the displayed =9Calternator amp
erage=9D seems to be all over the scale; sometimes 45-50 amps when the
airplane has most accessories off. Feeding both alternators into a single
=9Cbus bar=9D seems to cause issues and is that safe?
Therefore it=99s been recommended that I swap out the Stby Alt for a 6
0A PP alternator and just use it as the primary power source. My preference
would be going to a =9CxxxZ=9D plan where each alternator power
s its own bus but I=99ve been advised against that. (The good news is m
y A&P figured out the shunt had not been changed per Garmin install instruct
ional, a 100A 50 milivolts currently on order.)
Sorry for the length of this. William Booth
Message 8
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| Subject: | RV10 Electrical System Safety & Operational Issues |
=EF=BB
=EF=BB Hey guys I am way in over my head on this forum but a nice man fro
m BandC suggested I try. Attached is the electrical diagram of my recently p
urchased RV10. It was completed in 2009 and the avionics was switched to a G
armin 900x a year later. My issue is it safe and operationally sound. It is
an =9C###=9DX=9D design, if that is familiar.
Apparently the builder added a =9Cbus tie=9D in order to bypass a
diode (bridge rectifier type) because the draw to recharge the =9CAux
Battery=9D (2 wheel chair batteries 7Ah 12v wired in series) reduced t
he essential bus voltage to 12.6v. This =9Cbus tie=9D when on,bo
osts both busses back to 13.6v. Is this how it was meant to be run?
Additionally with both alternators on, the displayed =9Calternator amp
erage=9D seems to be all over the scale; sometimes 45-50 amps when the
airplane has most accessories off. Feeding both alternators into a single
=9Cbus bar=9D seems to cause issues and is that safe?
Therefore it=99s been recommended that I swap out the Stby Alt for a 6
0A PP alternator and just use it as the primary power source. My preference
would be going to a =9CxxxZ=9D plan where each alternator power
s its own bus but I=99ve been advised against that. (The good news is m
y A&P figured out the shunt had not been changed per Garmin install instruct
ional, a 100A 50 milivolts currently on order.)
Sorry for the length of this. William Booth
Sent from my iPad
Message 9
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| Subject: | RV10 Electrical Issues |
Hey guys I am way in over my head on this forum but a nice man from BandC su
ggested I try. Attached is the electrical diagram of my recently purchased R
V10. It was completed in 2009 and the avionics was switched to a Garmin 900x
a year later. My issue is it safe and operationally sound. It is an
=9C###=9DX=9D design, if that is familiar.
Apparently the builder added a =9Cbus tie=9D in order to bypass a
diode (bridge rectifier type) because the draw to recharge the =9CAux
Battery=9D (2 wheel chair batteries 7Ah 12v wired in series) reduced t
he essential bus voltage to 12.6v. This =9Cbus tie=9D when on,bo
osts both busses back to 13.6v. Is this how it was meant to be run?
Additionally with both alternators on, the displayed =9Calternator amp
erage=9D seems to be all over the scale; sometimes 45-50 amps when the
airplane has most accessories off. Feeding both alternators into a single
=9Cbus bar=9D seems to cause issues and is that safe?
Therefore it=99s been recommended that I swap out the Stby Alt for a 6
0A PP alternator and just use it as the primary power source. My preference
would be going to a =9CxxxZ=9D plan where each alternator power
s its own bus but I=99ve been advised against that. (The good news is m
y A&P figured out the shunt had not been changed per Garmin install instruct
ional, a 100A 50 milivolts currently on order.)
Sorry for the length of this. I=99ve sent other versions of this tryin
g to get the photo the right size. William Booth
Sent from my iPad
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