Today's Message Index:
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1. 09:39 AM - Re: Z13/8 all electric airplane (eschlanser)
2. 11:19 AM - Re: Re: Z13/8 all electric airplane (Robert L. Nuckolls, III)
3. 04:08 PM - Re: Z13/8 all electric airplane (eschlanser)
4. 05:42 PM - Re: Re: Z13/8 all electric airplane (Robert L. Nuckolls, III)
Message 1
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| Subject: | Re: Z13/8 all electric airplane |
Bob,
Instead of a polyswitch in the PM alternator circuit, may I suggest using the Linear OVP module from PerhelionDesign.com? http://www.periheliondesign.com/lovm.htm
Disclaimer: I have no connection with the company except for using the LOVP instead
of crowbar OVM/RELAY combinations in both main alternator (IR) and aux alternator
(SD8) circuits in my project's Z-13-8 derived electrical system.
I had considered using polyswitchs. True, the LOVP module is way more expensive
than polyswitches. But in return for the cost, the engineering work has been
done. It has provision for an Led lite annunciator and a reset feature. I don't
understand all the engineering, but it seems to me that a thermally activated
polyswitch is not under the pilot's control. After cooling, wouldn't it keep
trying to reset itself?
I'd like to see how you would use the Perhelion LOVP in Z13/8 as I struggled with
the wiring.
Eric S.
Z13/8 in a W-10 Tailwind/O-320 project
[/quote]
Actually, I've been contemplating replacement of
the breaker in that drawing with a polyswitch.
Given the low current demands for driving the
relay coil, this would be an excellent place
to incorporate a polyswitch. I'm wrestling
with annunciation issues. A popped breaker is,
not a great annunciator but it's not bad. If
we 'hide' a tripped condition by going solid
state polyfuse, then perhaps some form of OV
TRIP indication is called for.
I've got some ideas and will incorporate the
most elegant configuration into the Z-figures
that control PM alternators with the RELAY/OVM
combination.
Bob . . .[/quote]
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=401210#401210
Message 2
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| Subject: | Re: Z13/8 all electric airplane |
At 11:37 AM 5/23/2013, you wrote:
>
>Bob,
>
> Instead of a polyswitch in the PM alternator circuit, may I
> suggest using the Linear OVP module from PerhelionDesign.com?
> http://www.periheliondesign.com/lovm.htm
That is one of many ov management options
used in vehicular DC power systems . . .
> I had considered using polyswitchs. True, the LOVP module is way
> more expensive than polyswitches. But in return for the cost, the
> engineering work has been done. It has provision for an Led lite
> annunciator and a reset feature. I don't understand all the
> engineering, but it seems to me that a thermally activated
> polyswitch is not under the pilot's control. After cooling,
> wouldn't it keep trying to reset itself?
The polyswitch does not go open, only to a high
resistance state which keeps drawing enough current
to STAY in that high resistance state. This means
that fault current that would put wiring at risk is
limited to some acceptably low value. In the
case OV management for the PM alternator, the
NORMAL current that holds the relay closed will
not drip the polyswitch. A dead short OV module
connected across the relay would burn wires unless
a fuse, breaker or polyswitch did not respond to
limit the current. Fuses and breakers take the current
to zero . . . the polyswitch takes it to some low,
non-hazardous value. Either philosophy is consistent
with Z-13/8 design goals.
In the interim, I've once again backed off the incorporation
of the polyswitch. NOT because it fails to function
as advertised but because it's designed to mount to
an ECB. Artful incorporation of the polyswitch into
Z-13/8 PM alternator control calls for mounting it
into some fabricated assembly. I looked at a surface
mounted device on an ECB along with resistors to
drive a 'tripped' indicator light.
Too much monkey motion . . . so my track record is
still intact. Since my first introduction to the
realm of inrush limiters and polyfuses at LearJet
in 1980, I've not discovered an elegant way to
incorporate these critters into airframe system
wiring. They work fine as a component INTERNAL to
a black box.
> I'd like to see how you would use the Perhelion LOVP in Z13/8 as I
> struggled with the wiring.
You use it per the installation instructions. It's
wired in series with the device that you want to
shut down in the event of an ov condition.
The point of Z13/8 is to mitigate "struggling". The
drawing is not intended to be the epitome of systems
but simply an elegant solution that meets design goals
for the system.
There are certainly useful variations on the theme
that can and should be considered if the drawing
as-presented fails to meet some other design goal.
Assuming you perceive a need to depart from the
suggested wiring, what new or overlooked design goal
needs attention? In other words, what feature of Z-13/8
drives your willingness/need to "struggle"? What
changes are you considering and what is the anticipated
return on investment for the change?
Bob . . .
Message 3
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| Subject: | Re: Z13/8 all electric airplane |
Bob,
Thank you for the education on the polyswitch. Once again, you cleared up an electrical
design for me.
Z13/8 is awesome. The only reason I changed anything in Z13/8 was due to the advertising
for the LOVP. The marketing sold me on it. However, the LOVP has more
wires and connections than the crowbar OV, making it more involved to incorporate.
For this first timer, anything electrical is a struggle. I should have built the
absolute simplest system, Z11, first. Then, I could have worked my way up
to Z13/8 after getting some practical experience in the art.
Attending one of your seminars and studying the AEC have been great exposure to
the formal discipline of aircraft electrical science.
Thanks again for so generously sharing your experience,
Eric S.
[/quote]
Assuming you perceive a need to depart from the
suggested wiring, what new or overlooked design goal
needs attention? In other words, what feature of Z-13/8
drives your willingness/need to "struggle"? What
changes are you considering and what is the anticipated
return on investment for the change?
Bob . . .[/quote]
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=401260#401260
Message 4
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| Subject: | Re: Z13/8 all electric airplane |
At 06:01 PM 5/23/2013, you wrote:
>
>Bob,
>
> Thank you for the education on the polyswitch. Once again, you
> cleared up an electrical design for me.
>
> Z13/8 is awesome. The only reason I changed anything in Z13/8 was
> due to the advertising for the LOVP. The marketing sold me on it.
> However, the LOVP has more wires and connections than the crowbar
> OV, making it more involved to incorporate.
>
> For this first timer, anything electrical is a struggle. I should
> have built the absolute simplest system, Z11, first. Then, I could
> have worked my way up to Z13/8 after getting some practical
> experience in the art.
> Attending one of your seminars and studying the AEC have been
> great exposure to the formal discipline of aircraft electrical science.
>
>Thanks again for so generously sharing your experience,
You're most welcome . . . it's what we do. Without
a doubt, the LVOP performs as advertised. My best
counsel is to set system desing goals and then
work for lowest parts count, weight and cost of
ownership.
I fiddled with a little different technique for
incorporating the Polyswitch into the PM alternator
OV protection . . . even came up with a little ECB
to carry a surface mount device along with the companion
resistors for trip annunciation. It would have been a
new product to offer . . .
Problem was that it applied to a limited number
of total situations for replacing a CB . . . namely
the disconnect relay for a PM alternator.
The 9024 4-function module is slated to replace crowbar
ovm in the control of PM alternators. So to spend $resources$
to spruce up a low-volume application slated to be obsolete
just didn't make sense.
Getting on the List and standing your own design goals
against recipes for success is the very best way to
strive for the elegant solution. It's a collegial service
I enjoyed during my tenures at Electro-Mech and Beech.
No reason it shouldn't work here too.
Bob . . .
Bob . . .
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