Today's Message Index:
----------------------
1. 08:34 AM - Re: AC current reading for Revmaster engine (user9253)
2. 09:09 AM - Re: Re: Too many Circuit breakers.... (Robert L. Nuckolls, III)
3. 01:09 PM - Re: Re: Too many Circuit breakers.... (Robert L. Nuckolls, III)
4. 07:24 PM - Re: Re: AC current reading for Revmaster engine (Robert L. Nuckolls, III)
Message 1
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| Subject: | Re: AC current reading for Revmaster engine |
Dan,
Your theory about battery current destroying the dynamo coils makes sense.
If correct, then I can think of a couple of solutions.
1. Replace the 30 amp fuses with 20 amp ones. And limit the aircraft load to 15
amps. If the regulator shorts out, then a fuse will blow.
2. Put a Schottky diode in series with the voltage regulator output. If the regulator
shorts out, the diode will block battery current.
--------
Joe Gores
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=507976#507976
Message 2
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| Subject: | Re: Too many Circuit breakers.... |
At 08:21 PM 9/27/2022, you wrote:
>
>Bob, and the rest of the AeroElectric crew,
>
>Thank you for all of the guidance. About to install this fun in the
>next week or two - just need to take a couple days away from work
>and a long weekend.
>
>Any final thoughts on this configuration?
Why the monkey motion in powering ignitions? What
are the anticipated failure modes that call for
those operational features. Multiple failures
during one tank of gas?
Recommend the ENGINE BUS as originally depicted.
One fuse/switch driving each ignition.
Why boost pump not on engine bus?
You've got a lot of 'stuff' on the e-bus.
Will the SD8 support everything on the
ebus? The e-bus is an ENDURANCE bus
crafted to be your 'plan-b' . . . ticket
to airport of intended destination in case of
main alternator failure.
Originally supported only by a well maintained
battery, a design goal was to power up only
those devices that get you home with
more electrical endurance than fuel.
Of course, this assumes that the builder
selects and maintains a battery such that
the design goal is met.
When supported by a s/b alternator, e-bus
loads can be greater but still, the idea
is to position the minimum number of switches
to re-configure for Plan-B. Have you done
those calculations?
>My only lingering question - to get rid of the diode drop
>(NTE53016), do I pose any risk in running a wire from the Master
>Relay (out) to the NC connection on the E Bus Relay(Blue)?
>(Redundant wire paths, diode keeps the Aux Bus Relay from being a
>single point of failure, but during normal operation, diode doesn't
>flow any current - it all goes through the added wire.)
The diode drop does not degrade performance
in any way. The diode is more reliable than
any relay or switch.
You show a mix of breakers/fuses. How come?
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 3
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| Subject: | Re: Too many Circuit breakers.... |
At 08:21 PM 9/27/2022, you wrote:
>
>Bob, and the rest of the AeroElectric crew,
>
>Thank you for all of the guidance. About to install this fun in the
>next week or two - just need to take a couple days away from work
>and a long weekend.
>
>Any final thoughts on this configuration?
P.S. you show the voltage sense lead to the LR3
tied to the battery. This puts a small but continuous
load on the battery even while parked. Suggest you
follow manufacturer's recommendations.
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 4
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| Subject: | Re: AC current reading for Revmaster engine |
>The conversation was a follow up of my question, "what is the
>temperature rating of the magnet wire being used."
>
>His response was that the coating was "designed to be soldered
>without direct abrasive removal of the insluation." (i.e. the heat
>from soldering would remove the insulation.). From memory, his
>suggestion was that the wire should be coated to achieve the desired
>insulation temperature rating. No specific level of improvement was
>defined other than the implicit message that the wire was not
>designed to be left uncoated in this type of an application.
This style of insulation on magnet wire
is primarily intended for the electronics
industry . . . the winding of inductors,
signal transformers. Used to buy the stuff
under the 'SolderEze' brand about 30 years
ago. Here's a contemporary example:
https://essexfurukawa.com/products/soderon-155-cu/product-datasheet/product-datasheet
63/37 solder is liquid at about 190C/333F.
Working temperature of tools would be set
for 220C or thereabouts. Other alloys of
solder would be higher.
The exemplar wire is rated at 155C . . . at
which some service life is expected. Usually
some tens of thousands of hours . . . with
an expected depression of 1/2 for each
10C rise in temperature.
So without having specific data on the
wire in question, we can safely assume
that operation at 350F is not a severe
stress on the wire. Class H insulation
is rated at 180C. So while this solderable
wire is not Class H, it's not terribly
fragile either.
>It's evident that the unusual localized heating that
>we've seen (and you show in the attachment) is suggestive
>of a very unusual heat source.
Precisely
>I don't think there is any other power source other than the battery,
>available to cause so much damage as we see on some of these stators.
>It also might explain a single coil buring up. As you've often brought up,
>an open wire will melt at a spot somewhere in the middle.
Yes, hanging out in free air where the
temperature coefficient of resistance
for copper creates a potential failure
location with heat energy fed from both
directions exacerbated by increase
in resistance.
It may well be that one winding on the
stator is singled out by a temperature
condition much higher than adjacent
poles but given the heat-sinking effect
of the stator iron, a melts-in-the-center
effect seems unlikely.
I'm still fond of the notion that faileded
windings get a thermal boost NOT from
I(squared)R losses in the wire but from
Eddy current losses in the iron on which
the wire is wound.
>Has anyone ran a short circuit test on a multi-coil stator
>like this? Would it not make some sense that one isolated
>coil could go through the rapid rise in resistance and burn
>up before the rest?
Not able to wrap my head around this idea.
I'm still thinking root cause is in the
poorly crafted magnetics. External forces
such as system loads and style of regulator
are secondary and much less influential.
Bob . . .
Un impeachable logic: George Carlin asked, "If black boxes
survive crashes, why don't they make the whole airplane
out of that stuff?"
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