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1. 06:23 AM - Re: Revmaster 'dual' alterantors (user9253)
2. 06:28 AM - Re: Re: Revmaster 'dual' alterantors (Robert L. Nuckolls, III)
3. 07:28 PM - Re: Revmaster 'dual' alterantors (dj_theis)
Message 1
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| Subject: | Re: Revmaster 'dual' alterantors |
Actually it is desired that the two windings be 180 degrees out of phase.
That way, only one winding will conduct at a time and the output will be pulsing
DC. If the two windings are in phase, no problem, just reverse the leads on
one of the windings. Then the windings will be 180 degrees out of phase.
--------
Joe Gores
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=498149#498149
Message 2
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| Subject: | Re: Revmaster 'dual' alterantors |
> >>So take a peek at the simplified proposal diagram.
> >>Hook the two Revmaster windings in series-aiding
> >>and bring out the center-tap. Connect in full wave
> >>configuration with only TWO junction rectifiers.
>
>I like the approach and two questions come to mind:
> How well the current will be equally divided by the two windings?
> This is half wave rectification, right?
No, full wave . . . the current doesn't
NEED to be exactly shared . . . each winding
conduct on 1/2 cycle of the time independently
of each other. Unlike the legacy, single winding
PMA and bridge rectifier approach, this
configuration splits the two halves onto
separate windings . . . but it's still
full wave rectification.
>I have not spun my engine yet but from examination of the windings I
>expect to see the two PMAs "IN PHASE" and as noted, single phase,
>not polyphase. Does this configuration change the expectation of
>roughly evenly divided current? If the two PMAs were out of phase
>by 180 degrees (which is possible if my talents with the "right hand
>rule" are off abit) I assume the center tap would not operate the
>same, if at all.
From what I understand, the Revmaster
PMA is wound BI-FILAR meaning two strands
of wire side-by-by side. This produces
two, identical windings that COULD and
perhaps SHOULD be wired in parallel. This
would cut the current in each winding to
1/2 of the total.
>I have to pull my engine once more before I start it (hopefully, yet
>this fall) and will examine the windings on the PMAs closely to
>convince myself of the phase relationship between the two halves.
The result is predictable. You have two, identical
windings sharing the same physical space
on the stator. Voltages induced by the
mechanics and magnetics are identical.
Given that the burning the 'active' winding
also burns the 'standby' winding, you do
not have redundant systems. You might as
well run the two windings in parallel
which would greatly reduce the stress on
the wires and may well drive the 'lithium'
failure rate to zero.
>One final note. I've thought about this a little (clearly not as
>much as Bob). I plan on installing thermo-couples as close to the
>center of each stator base as I can. My thought is to run the
>engine as deigned, with OEM regulators and running one halve at a
>time. I am planning on a Odyssey battery (PC680) with added (2)
>shunt resistors in the charge circuit to increase the load seen by
>the PMAs. I plan on trying to identify what the conditions are that
>lead to the high temperature in the PMAs. I hope to be able to
>install the TCs close enough to the windings to obtain a warning
>before they overheat. I think the expected meltdown of the "enamel"
>insulation is a bit over 200C. Can anyone confirm?
I don't know of any manufacturer of aviation
hardware that doesn't call out Class H insulation
for their magnet wire
https://tinyurl.com/y3a7o26s
Without going to some exotic wire coated
with un-obtainium, Class H is the best
you can buy off the shelf. So yeah, 200C
max operating for the copper . . .
Thermocoupling the windings is not a bad idea.
Are those stator windings varnished? Getting
a 'real' copper temperature number on a running
machine is not easy. The closest I ever
got to 'real' measurements was by bringing
leads for winding-under-observation outside
so that it could be quickly switched from
'service' to 'measure' mode by exciting the
winding with a calibrated current and then
measuring the voltage drop. Copper temperature
can be calculated by knowing the temperature coefficient
of resistance for copper. This had to be done
quickly (under 100 mS) 'cause the copper cools
very rapidly when the loads are removed and the
heat soaks out.
Generally speaking, with your 200C rated wire,
getting thermocouple readings over 170-180C
would be cause for concern.
We KNOW this design is thermally deficient . . .
too many of them have burned up in service.
Too many band-aids have been suggested
and attempted with little if any relief.
>In the long term, I'd like to install something like the CCCV
>regulator mentioned. Is there actually such a regulator designed
>and available for a PMA on an OBAM aircraft?
Sure, they're commercial off the shelf items.
I've got a couple on the bench now that I'm
going to use in a proof-of-concept study. But
after reading about the bi-filar windings
design, I'm not sure there's much value to
be secured by 'upgrading' the rectifier/regulator
design for this engine.
As currently configured, there is NO REDUNDANCY
of engine driven power sources. I'm beginning
to think one would be well advised to
simply parallel the two windings and treat
them as one. This alone would produce a profound
drop in wire temperatures for any given load.
Bob . . .
Message 3
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| Subject: | Re: Revmaster 'dual' alterantors |
[quote]
Actually it is desired that the two windings be 180 degrees out of phase.
That way, only one winding will conduct at a time and the output will be pulsing
DC. If the two windings are in phase, no problem, just reverse the leads on
one of the windings. Then the windings will be 180 degrees out of phase.
[/quote]
Ah, yes. that makes perfect sense. The end result is a full wave rectified waveform
output.
Thanks for the clarification Joe.
Dan Theis.[/quote]
--------
Scratch building Sonex #1362
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=498151#498151
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