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Tundra10
Joined: 14 Jun 2010
Posts: 102
Location: Scarborough, Ontario
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 Posted: Tue Mar 06, 2012 2:58 pm Post subject: Lamar DSX1240-1 Alternator |
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Bob,
I failed at a search for a schematic of a typical internally regulated
alternator.
I am trying to understand the purpose of the wire to the alternator
via the 5A breaker and the "alternator switch".
One possibility is that it improves regulation by sensing the voltage
without the drop in the main feed wire. In this application, that
seems like overkill, so probably not it.
One website hinted at a way of preventing the alternator from charging
until the car was running. The control could be only used to turn the
alternator on, but not off.
Although a contactor could be installed per Z-24, that seems like a
poor way to patch the problem.
I don't know if my fellow builder is up to the task of modifying the
alternator. Unfortunately, he is in a different country than I, so I
can't just pop over to look at it. I expect it voids the warranty to
cut the regulator out. I expect the best thing is to recommend that
he obtain a more suitable alternator.
Jeff Page
Dream Aircraft Tundra #10
| Quote: | Time: 04:41:29 PM PST US
From: "Robert L. Nuckolls, III" <nuckolls.bob(at)aeroelectric.com>
Subject: Re: Lamar DSX1240-1 Alternator
overvoltage protection
At 02:28 PM 3/3/2012, you wrote:
Does anyone have additional information concerning the Lamar 40A
alternator, part number DSX1240-1 ?
A fellow builder purchased one from his engine builder and wants to
add overvoltage protection.
The website seems to be non-functional at the moment, so I have
attached the diagram provided in the minimal installation
instructions. If the attachment doesn't come through, you can see the
diagram here:
http://www.qenesis.com/Temp/LamarDSX1240-1.jpg
To me, it looks like the separate connection for the field wire should
work nicely with a typical overvoltage protection circuit designed to
pop the breaker.
This diagram has the look, feel and smell of the
classic, internally regulated automotive alternator.
Modification for external regulation (Like the
B&C products) -OR- external OV protection
for the existing regulator (like PlanePower)
are the most practical approaches.
Either one requires a knowledgeable disassembly
and surgery to add OV protection to the field
supply circuit. Alternatively, one can add a
b-lead contactor and ov sensing as depicted
here:
http://www.aeroelectric.com/PPS/Adobe_Architecture_Pdfs/Z24-Interim.pdf
My best recommendation is to accomplish the
necessary changes to remove the existing
regulator and re-wire for external regulation
typical of the Z-figures.
Bob . . .
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nuckolls.bob(at)aeroelect
Guest
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| Posted: Wed Mar 07, 2012 7:03 am Post subject: Lamar DSX1240-1 Alternator |
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At 04:56 PM 3/6/2012, you wrote:
--> AeroElectric-List message posted by: Jeff Page <jpx(at)qenesis.com>
Bob,
I failed at a search for a schematic of a typical internally regulated
alternator.
I am trying to understand the purpose of the wire to the alternator
via the 5A breaker and the "alternator switch".
Understand. Here's an exemplar schematic for an
internally regulated alternator. To the best of
my knowledge, this theme is consistent throughout
the modern alternator industry. This image was
excerpted from the MC33092 regulator data sheet which
you can get here:
http://aeroelectric.com/Mfgr_Data/Semiconductors/MC33092A.pdf
[img]cid:.0[/img]
One possibility is that it improves regulation by sensing the voltage
without the drop in the main feed wire. In this application, that
seems like overkill, so probably not it.
One website hinted at a way of preventing the alternator from charging
until the car was running. The control could be only used to turn the
alternator on, but not off.
Actually . . . pretty close. In this case, current supplied
through the ignition switch and warning light are used to
to effect an on/off control of the alternator although
switching the sense lead would do that too . . . the "LOSS
OF SENSE" circuit would detect an open sense line and
effectively control the alternator.
Although a contactor could be installed per Z-24, that seems like a
poor way to patch the problem.
I'm certainly amenable to a better idea. This problem
has been wrestled with by many folks over the years.
I don't know if my fellow builder is up to the task of modifying the
alternator. Unfortunately, he is in a different country than I, so I
can't just pop over to look at it. I expect it voids the warranty to
cut the regulator out. I expect the best thing is to recommend that
he obtain a more suitable alternator.
Yup. But as you can see in the exemplar schematic, there
are failure modes that can and have produced uncontrollable
runaways. The legacy recipe for success has been to gain
direct access to field excitation . . . which requires
modifications not unlike those offered by B&C and PlanePower.
Bob . . .
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Tundra10
Joined: 14 Jun 2010
Posts: 102
Location: Scarborough, Ontario
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| Posted: Wed Mar 07, 2012 8:18 am Post subject: Lamar DSX1240-1 Alternator |
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| Quote: | Understand. Here's an exemplar schematic for an internally regulated
alternator. To the best of my knowledge, this theme is consistent
throughout the modern alternator industry. This image was excerpted
from the MC33092 regulator data sheet which you can get here:
http://aeroelectric.com/Mfgr_Data/Semiconductors/MC33092A.pdf
|
Thanks, Bob. This is what I needed to read to understand the issue.
I guess this makes sense to the auto industry.
The IC does try to handle under and overvoltage conditions, but that
is like asking the fox to guard the henhouse.
Modifying this circuit would be difficult. Much easier to delete the
regulator in favor of an external one. Even easier still is selling
the existing alternator and purchasing a more suitable one, which is
what he has decided to do.
Thanks again for more education !
Jeff Page
Dream Aircraft Tundra #10
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nuckolls.bob(at)aeroelect
Guest
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| Posted: Thu Mar 08, 2012 3:31 pm Post subject: Lamar DSX1240-1 Alternator |
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At 10:16 AM 3/7/2012, you wrote:
| Quote: | --> AeroElectric-List message posted by: Jeff Page <jpx(at)qenesis.com>
Modifying this circuit would be difficult. Much easier to delete the
regulator in favor of an external one. Even easier still is selling
the existing alternator and purchasing a more suitable one, which is
what he has decided to do. |
Good. It's is difficult sometimes to make a useful trade between multiple solutions without have a good grasp of the "big picture". It's easy to be distracted by what one might call false economics. E.g., a cousin of mine was recipient of a nice Lincoln 4-door. He was in tall cotton until something broke. My first 'good' car was a '57 Chevy BelAire with all the goodies. I too was riding high until something broke. My next car was a '59 6-cyl, stick shift with a good heater and crank windows. Best return-on-investment in transportation I ever made. In spite of 1/2 the gas mileage, my total cost of ownership per mile traveled was less than buying a new Volkswagon Bug.
Availability of small externally regulated alternators is limited. I just checked the MPA catalog for single-tension, two-pivot externally regulated alternators. Couldn't fine anything under 90 amps. Doing the internal-to- external mod isn't real difficult. How much money does he have tied up in the alternator he has?
Bob . . . [quote][b]
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Tundra10
Joined: 14 Jun 2010
Posts: 102
Location: Scarborough, Ontario
|
| Posted: Fri Mar 09, 2012 9:13 am Post subject: Lamar DSX1240-1 Alternator |
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| Quote: | Modifying this circuit would be difficult. Much easier to delete the
regulator in favor of an external one. Even easier still is selling
the existing alternator and purchasing a more suitable one, which is
what he has decided to do.
|
Good. It's is difficult sometimes to make
a useful trade between multiple solutions
without have a good grasp of the "big picture".
It's easy to be distracted by what one might
call false economics. E.g., a cousin of mine
was recipient of a nice Lincoln 4-door. He
was in tall cotton until something broke. My
first 'good' car was a '57 Chevy BelAire
with all the goodies. I too was riding high
until something broke. My next car was a '59
6-cyl, stick shift with a good heater and
crank windows. Best return-on-investment in
transportation I ever made. In spite of 1/2
the gas mileage, my total cost of ownership
per mile traveled was less than buying a
new Volkswagon Bug.
Availability of small externally regulated
alternators is limited. I just checked the
MPA catalog for single-tension, two-pivot
externally regulated alternators. Couldn't fine
anything under 90 amps. Doing the internal-to-
external mod isn't real difficult. How much
money does he have tied up in the alternator
he has?
I think he plans to buy the B&C 40A alternator and the external
regulator/overvoltage protection products, which I think are twice the
cost of the alternator he bought from the engine shop.
Although the risk is low, if a runwaway alternator took out his
avionics and EFIS system, saving those few hundred dollars would seem
like a pretty poor choice.
Even if he modifies the alternator he has, he still needs to purchase
the external regulator/over voltage anyway.
Since he has less electrical experience than those of us on this list,
buying a product that requires no special modifications is an
expedient option.
Jeff Page
Dream Aircraft Tundra #10
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