REFLECTOR: Circuit Breakers/Switches

Fri Feb 10 20:31:26 CST 2012

Excellent read

Mark Magee <edjonesbrady at gmail.com> wrote:

>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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>
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