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gordonrsmith921@yahoo.com
Joined: 06 Oct 2009
Posts: 24
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 Posted: Mon Jun 14, 2010 2:45 pm Post subject: Permanent Magnet Alternators or Dynamo |
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In the AEC writings, Matronics postings and Z figures I see references to Permanent Magnet Alternators and Dynamos. Are they one in the same; is the physics basically the same? For instance in a Rotax or Jabiru system with a stator being energized by magnets on the flywheel technically the same as a B&C SD-8?
Can regulators for these systems be substituted and crisscrossed? I see where you have illustrated the use of a AM 101406 John Deere Regulator for the Z-9 Corvair system. I also recollect discussions about using of this same regulator as a more robust substitution for the Rotax Ducati and the Jabiru supplied regulator. Following this line of thought, could the AM 101406 be used also with the SD-8?
In the Z figures that incorporate Dynamos, I see some variables. I can’t quite understand the reasons for some of them.
- Some systems incorporate a self-excitation feature such as illustrated in Z-25. When is this recommended? Should it be used with the Jabiru or Rotax charging system?
- Shut down control of these systems generally incorporate a S704-1 relay with a OVM-14 crowbar over voltage module (or AEC9024) across the coil terminals. In some Z figures this S704-1 also utilizes a diode across the coil and some don’t. Does the internal electronics of the OVM-14 or AEC9024 preclude the use of such a diode in some cases?
- The S704-1 relay is employed sometimes in one of the legs of the Dynamo before the regulator and sometimes in the regulator output to the main bus. What is the reason behind this decision?
- In some Z figures the sense for the regulator is tied directly to the regular 12V.DC output and in others it comes from the main bus through the alternator switch. Is there a preferred reason for one or the other?
Gordon Smith
[quote][b]
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nuckolls.bob(at)aeroelect
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| Posted: Tue Jun 15, 2010 5:16 am Post subject: Permanent Magnet Alternators or Dynamo |
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At 05:43 PM 6/14/2010, you wrote:
In the AEC writings, Matronics postings and Z figures I see
references to Permanent Magnet Alternators and Dynamos. Are they one
in the same; is the physics basically the same? For instance in a
Rotax or Jabiru system with a stator being energized by magnets on
the flywheel technically the same as a B&C SD-8?
Yes . . .
Can regulators for these systems be substituted and crisscrossed? I
see where you have illustrated the use of a AM 101406 John Deere
Regulator for the Z-9 Corvair system. I also recollect discussions
about using of this same regulator as a more robust substitution for
the Rotax Ducati and the Jabiru supplied regulator. Following this
line of thought, could the AM 101406 be used also with the SD-8?
Probably but with limits. Unlike wound-field alternators
wherein vertually all brands of every size draw
no more than 3-4 amps of field current, rectifier/
regulators for PM alternators must carry ALL of
the machine's output current. Therefore, while a
larger r/r for the 30A J-D machine may work well
with the SD-8, the converse is not true.
In the Z figures that incorporate Dynamos, I see some variables. I
can't quite understand the reasons for some of them.
Some systems incorporate a self-excitation feature such as
illustrated in Z-25. When is this recommended? Should it be used
with the Jabiru or Rotax charging system?
The self-excitation feature was crafted for
those who were concerned about delayed reaction
(like hours?) for getting the SD-8 stand-by
power source turned on to support a system
that was now being fed by a dead battery. It's
a kind of band-aid for not have crafted and/or
timely implementation of plan-B.
Where the PM alternator is your primary power
source, the utility of a self-exitation feature
is still more diminished. So, no. If the feature
is not included on any particular drawing, it's
value is considered too low to be useful.
Shut down control of these systems generally incorporate a S704-1
relay with a OVM-14 crowbar over voltage module (or AEC9024) across
the coil terminals. In some Z figures this S704-1 also utilizes a
diode across the coil and some don't. Does the internal electronics
of the OVM-14 or AEC9024 preclude the use of such a diode in some cases?
The diode can be included in all cases and
serves some utility for increasing life
of the controlling switch but yes, it's
less necessary when the OVM-14 is part of
the coil control circuit. The 9024 has the
diode mounted on the board.
The S704-1 relay is employed sometimes in one of the legs of the
Dynamo before the regulator and sometimes in the regulator output to
the main bus. What is the reason behind this decision?
Putting the relay downstream of the r/r only
disconnts it from the airplane and MIGHT
allow a damaged r/r to continue to take
energy from the dynamo and suffer further
damage. Shutting down from the power INPUT
side to the r/r brings everything to a graceful
state of being when the alternator control
switch is OFF>
In some Z figures the sense for the regulator is tied directly to the
regular 12V.DC output and in others it comes from the main bus
through the alternator switch. Is there a preferred reason for one
or the other?
Doesn't matter. You are to be commended for
taking the time to study these drawings and
picking up on the variables!
Bob . . .
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