REFLECTOR: Circuit Breakers/Switches

Fri Feb 10 19:42:14 CST 2012

Ron,
This is a long read, maybe 10 minutes, but from what I've been told over
the years I think this article nails the aircraft alternator
overvoltage/failure problem:

http://www.nflite.com/ChargingSystem.html

Maybe the solid state circuit breakers being discussed on this thread are
easier on the alternator?

Mark Magee
N34XL XLFG

On Fri, Feb 10, 2012 at 4:51 PM, Ron N Velocity XLFG <VelocityXL at fastmail.fm
> wrote:

> **
> Does any one know why alternator in airplanes have an issue with over
> voltage?
>
> Ron
>
>
> ----- Original Message -----
>
> *From:* Mark Magee <edjonesbrady at gmail.com>
> *To:* Velocity Aircraft Owners and Builders list <reflector at tvbf.org>
> *Sent:* Friday, February 10, 2012 3:11 PM
> *Subject:* Re: REFLECTOR: Circuit Breakers/Switches
>
> Doug,
> I like your thinking. I've liked the resettable circuit breakers over the
> years due to occasional alternator issues: runaway, voltage regulator
> issues Ect. In flight where I pulled the field wire ALT breaker or toggle
> that fixed the alternator emergency. Yet after the alternator was sidelined
> I had some thrown breakers from a momentary surge/over-voltage condition on
> the bus. With the alternator removed and primary indications that the ALT
> was the culprit I would boldly re-energize (WITHOUT RISKING AN IN-FLIGHT
> FIRE!) any breakers that popped. Next we land on BATT only. As I recall
> that was one of the primary reason breakers were put in civilian aircraft.
> For the military there was always the 'unfriendlies' attempting to
> forcefully disable some of our circuits, which could be diagnosed and
> re-energized in flight, avoiding a you-know-what (in flight fire!).
>
>
> Mark B. Magee
> Sent from IPhone 4
>
> On Feb 10, 2012, at 1:45 PM, "Douglas Holub" <douglas.holub at gmail.com>
> wrote:
>
>   Fuses could be used in that fashion, but I have a seperate fuse for
> each avionics box. If my transponder fuse blows in flight, I don't want to
> replace it. There's a short somewhere. I'll replace the fuse on the ground
> after I've determined what caused the problem.
>
> The issue I have with PTC resettable fuses and manual circuit breakers is
> the temptation to re-energize the circuit if the problem is intermittent.
> If a chafed wire shorts out the comm, the PTC fuse or the breaker will shut
> down the current. Then if that chafed wire vibrates away from the shorting
> conductor, the symptom is gone and the comm could function normally again.
> I would be tempted to keep power cycling the comm in the hopes that it
> would start working again. But the sparks and current surges associated
> with a short circuit are not safe, so I prefer that a fuse permanently
> disable the circuit until I correct the problem.
>
> I know breakers are standard in production aircraft. But they're
> expensive, use more panel room, and fuses work better, IMHO. Ain't
> experimental aviation great?
>
> Doug Holub
> Standard FG, 135 hrs
>
> ----- Original Message -----
> *From:* Laurence Coen <lwcoen at hotmail.com>
> *To:* Velocity Aircraft Owners and Builders list <reflector at tvbf.org>
> *Sent:* Friday, February 10, 2012 2:07 PM
> *Subject:* Re: REFLECTOR: Circuit Breakers/Switches
>
> Tom,
>
> The Ztron box uses this type of technology if not in fact this particular
> device.  I use the PTC type resettable fuse.  A conventional fuse uses a
> low melting point metal element that melts on overload and interrupts the
> circuit.  This follows the KISS principal but having to replace it in
> flight doesn't.  Let's say your avionics stack goes dark.  This involves
> multiple devices only one of which developed a fault.  You turn them all
> off and replace the fuse.  Then turn them back on one at a time till the
> bad box again blows the fuse.  Now you leave that one off and again replace
> the the fuse assuming you had two spares.  A PTC works like a fuse but when
> you turn off the power it cools down and resets itself which makes life
> simpler.
>
> Here's how they work.  They consist of two metal plates separated by a
> layer of polymer/carbon particles that is solid at low temperature.  In
> this state the carbon clumps together and is conductive.  On over current
> the polymer melts and the carbon particles separate switching the device to
> the high resistance state.  Switching off the avionics stack in effect
> replaces the fuse.  In honor of St. Valentines'  Day I call this the "KISS,
> KISS" principal.
>
> Larry Coen
> N136LC
>
>  *From:* Tom Falls <tomfalls6 at gmail.com>
> *Sent:* Friday, February 10, 2012 8:59 AM
> *To:* Velocity Aircraft Owners and Builders list <reflector at tvbf.org>
> *Subject:* Re: REFLECTOR: Circuit Breakers/Switches
>
> I found this white paper on electronic CB's.
> http://www.ti.com/lit/an/slua131/slua131.pdf
>
> Sounds like "magic bullet" technology to me, but then I'm not very well
> versed in this electronic stuff (over my head). Also don't know whether or
> not this is the technique used by Ztron.
>
> Tom
>
> On Feb 10, 2012, at 7:58 AM, Mark Magee <edjonesbrady at gmail.com> wrote:
>
>   Brett,
> Can you give us the nutshell version of how these things function. I
> Googled 12V electronic circuit breaker last night and basically got
> nothing. Possibly my search terms were faulty.
> Despite my old Steam Gauge brain I am listening!
>
> Mark B. Magee
> N34XL XLFG
> Sent from IPhone 4
>
> On Feb 9, 2012, at 8:03 PM, "Brett Ferrell" <reflector at velocityxl.com>
> wrote:
>
>   We have the Vertical power system, which is sort of electronic
> breakers, though a more complicated version.  Thus far we're pretty happy
> with it, but we only have a few handful of hours so it's early to say
> definitively.
>
> Brett
>
>
> -------Original Message-------
> From: Tom Falls **
> To: Velocity Aircraft Owners and Builders list **
> Subject: Re: REFLECTOR: Circuit Breakers/Switches
> Sent: 09 Feb '12 20:41
>
> I was hoping there was more experience with ztron and/or other solid state
> CB's. I like the size, price, weight and simplicity of this technology. I'm
> not inclined to jump on the ztron product until I know they can execute
> well. I'll hold off as long as I can before purchasing anything and keep
> researching and hoping ztron or someone else has a proven safe and reliable
> product.
>
> Tom
>
> ****
>
>
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