REFLECTOR: Circuit Breakers/Switches
Ron N Velocity XLFG
VelocityXL at fastmail.fm
Fri Feb 10 16:51:17 CST 2012
Does any one know why alternator in airplanes have an issue with over voltage?
Ron
----- Original Message -----
From: Mark Magee
To: Velocity Aircraft Owners and Builders list
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
To: Velocity Aircraft Owners and Builders list
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
Sent: Friday, February 10, 2012 8:59 AM
To: Velocity Aircraft Owners and Builders list
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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