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jan_de_jong(at)casema.nl
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 Posted: Mon Mar 16, 2009 7:20 am Post subject: AeroElectric-List Digest: |
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Bob,
Your question to Gilles regarding Rotax/Ducati regulator reminded me of
something I mentioned on the Europa list last year.
Maybe of use here, maybe not.
-----
I think I found an interesting bit of forum:
http://www.pilots24.com/pilots24/forum/viewtopic.php?t=7756&sid=542ce097cbdde3a5ceba2e5bd0d71c38
Scroll down to 40% of the page.
Writer Arrow is convinced that he has found the problem with the
912/Ducati regulators, as follows.
The regulating bridge has 4 elements:
2 power diodes MR2510 and 2 thyristors TP154E (obsolete) or 2N6504.
One diode and one thyristor in series conduct part of one half sinus of
the alternator output, the other diode and other thyristor in series
conduct part of the other half sinus of the alternator output.
The thyristors have TO220AB packaging and are mounted directly to the
housing.
The diodes have MICRODE BUTTON CASE 193 leadless packaging and Ducati
designed a mounting technique: both diodes with their cathodes soldered
to a small copper sheet, copper sheet mounted to the housing using
silicone foil heat conducting isolation; wires to the PCB soldered to
both anodes and the copper sheet.
Everything potted with a potting compound.
The problem is that heating/cooling cycles work the electrical
connections to the diodes loose. The symptoms are as follows: charging
ok after startup (13.8V), losing it after half an hour, but the warning
light stays off.
The writer has a diagnostic test using a battery and two 12V lamps to
check continuity under heating.
The writer has a solution: parallelling the diodes with an external pair.
The writer has notified Rotax and asked them what they had done / were
doing about the problem (January 2008). The correspondence can be
followed at:
http://www.pilots24.com/pilots24/forum/viewtopic.php?p=48297&highlight=#48297
Scroll 30% down.
The upshot seems to be that Rotax knows there is a problem but it must
be because units are operated above 80°C. No redesign yet.
-----
More translation from German if required...
Regards,
Jan de Jong
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nuckolls.bob(at)aeroelect
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| Posted: Wed Mar 18, 2009 4:24 am Post subject: AeroElectric-List Digest: |
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At 10:21 AM 3/16/2009, you wrote:
<snip>
| Quote: | The writer has notified Rotax and asked them
what they had done / were doing about the
problem (January 2008). The correspondence can be followed at:
http://www.pilots24.com/pilots24/forum/viewtopic.php?p=48297&highlight=#48297
Scroll 30% down.
The upshot seems to be that Rotax knows there is
a problem but it must be because units are
operated above 80°C. No redesign yet.
-----
More translation from German if required...
Regards,
Jan de Jong
|
Thank you for turning me onto this information. It
confirms what I've suspected about the original
regulator design. Electronically, its architecture
is not all that different than most of the rectifier-
regulators on the market. B&C's little SD-8 R-R
is nearly identical circuitry.
Choice of components and thermal management is VERY
important given that the SCR's are 4-layer devices
in high voltage drop during conduction. This heats
everything up. So it doesn't surprise me that there
are secondary issues with respect to packaging and
manufacturing processes that put other components
at risk.
I assisted B&C's engineer in crafting a robust
R-R some years ago. We built the thing on a hefty
heatsink and had all the hot-components well bonded.
I don't see that in the B&C catalog any more . . .
don't know what the story is.
In any case, the Rotax R-R offering could
use some attention to details!
Bob . . .
----------------------------------------)
( . . . a long habit of not thinking )
( a thing wrong, gives it a superficial )
( appearance of being right . . . )
( )
( -Thomas Paine 1776- )
----------------------------------------
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rv8iator
Joined: 11 Apr 2006
Posts: 145
Location: Newberg, OR
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| Posted: Wed Mar 18, 2009 5:51 am Post subject: AeroElectric-List Digest: |
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Wow...
Great info. I am currently wiring a Kitfox w/ Rotax 912 Ducati Rect/VR.
Chris Stone
Kitfox 7
RV-8
--
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C. Stone (RV8iator) |
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