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Transorb voltage for 14V system

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peter(at)mather.com
Guest

Posted: Sun Nov 05, 2006 11:08 am Post subject: Transorb voltage for 14V system

What is the optimum voltage of transorb for a 14V system. 15V seems a bit 

marginal. 18 seems OK?



Thanks in anticipation



Peter

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klehman(at)albedo.net
Guest

Posted: Sun Nov 05, 2006 7:03 pm Post subject: Transorb voltage for 14V system

Peter

18 volt seems to be the ones to use...  I used a few of them in a couple 

of places.

Ken



Peter Mather wrote:



 	  Quote: 	
		   

 <peter(at)mather.com>



 What is the optimum voltage of transorb for a 14V system. 15V seems a 

 bit marginal. 18 seems OK?



 Thanks in anticipation



 Peter

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nuckollsr(at)cox.net
Guest

Posted: Mon Nov 06, 2006 7:11 am Post subject: Transorb voltage for 14V system

At 06:35 PM 11/5/2006 +0000, you wrote:



 	  Quote: 	
		  



What is the optimum voltage of transorb for a 14V system. 15V seems a bit 

marginal. 18 seems OK?



Thanks in anticipation



Peter


	


    I am curious as to why you think you need one.

    The topic of spikes and other evils on the bus

    has been discussed here on the list since day-one,

    but to date, nobody has offered data from a repeatable

    experiment that illuminates sources, intensities and

    energy content of any perturbations of interest on

    an airplane or any other vehicular DC power system.



    Thus far, proponents of prophylactic measures such as



    Transorbs, MOVs, etc. have only cited the sales

    literature for such products that strongly suggest

    that you buy a lot of their product and sprinkle

    liberally about your system . . . at least having done

    so might make you feel good. See:



http://www.aeroelectric.com/Mfgr_Data/Semiconductors/AN9312.pdf



    Keep in mind too that a Transorb rated at 18v goes into

    a hard limit at over 25 volts when it's "working hard"

    at it's intended task. See:



http://www.aeroelectric.com/Mfgr_Data/Semiconductors/15ke.pdf

    Just be aware that to date, nobody has come forward

    with an engineering justification for sprinkling Transorbs

    around any part of the airplane's electrical system and

    then explained the simple-ideas that support their

    proposition. Those who have championed the Transorb

    most vigorously have overlooked and/or ignored the wide

    range of clamping voltage when the device is stressed

    over the full range of its ratings. An 18v Transorb

    does NOT guarantee that the device being "protected"

    will not suffer a spiking event that exceeds 18v by

    a considerable margin.



    Don't mis-interpret my suggestions here. Transorbs

    are marvelous devices and I've designed dozens of

    circuits that utilize these nifty gizmos to stand off

    the effects of lightning strokes! But the notion that

    they're useful for much of what folks tend to worry about

    in little airplanes is not supported in physics or practice.

        Bob . . .

      ---------------------------------------------------------

      < What is so wonderful about scientific truth...is that >

      < the authority which determines whether there can be   >

      < debate or not does not reside in some fraternity of   >

      < scientists; nor is it divine. The authority rests     >

      < with experiment.                                      >

      <                            --Lawrence M. Krauss       >

      ---------------------------------------------------------

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peter(at)mather.com
Guest

Posted: Mon Nov 06, 2006 8:19 am Post subject: Transorb voltage for 14V system

Bob



I'm building a RV9A and using a variant of Z-11 as the electrical system. 

Basically the endurance bus is provided by a composite design mini-power 

panel http://www.compositedesigninc.com/Mini_Power.htm  except that this has 

all the electrics connected to it except the alternator field, Critically, 

the non-switchable load is only a measured 0.8amp for a Dynon D10A and 

engine instruments.

I'm using a IR 125NQ015 diode mounted directly onto the power panel positive 

bus (this is a great device with 1/4" screw terminal for the incoming feed 

and its case as the output. This has a VF of only 0.33V so at my full load 

is only dissipating about 8 Watts.

I'm intending to use a 5000W axial transorb across the terminals of the 

power panel to provide both a level of spike protection but also overvoltage 

protection. I've conducted experiments with a 9V version of the transorb and 

demonstrated that I can blow either my endurance bus fuse or my alternator 

current limiter without damage to the transorb. In other words an 

overvoltage on the alternator should blow its own fuse and if any transients 

exist they would also be mopped up. The transorb voltage is obviously 

critical in this. I don't want it conducting in any normal situation, but do 

want it to let go as soon as any significant overvoltage condition exists.



Without wishing to start any further spike protection or alternator 

overvoltage wars, I'm very interested in your views on this approach.



Best regards



Peter

---

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nuckollsr(at)cox.net
Guest

Posted: Mon Nov 06, 2006 8:32 pm Post subject: Transorb voltage for 14V system

At 04:16 PM 11/6/2006 +0000, you wrote:



 	  Quote: 	
		  



Bob



I'm building a RV9A and using a variant of Z-11 as the electrical system. 

Basically the endurance bus is provided by a composite design mini-power 

panel http://www.compositedesigninc.com/Mini_Power.htm  except that this 

has all the electrics connected to it except the alternator field, 

Critically, the non-switchable load is only a measured 0.8amp for a Dynon 

D10A and engine instruments.

I'm using a IR 125NQ015 diode mounted directly onto the power panel 

positive bus (this is a great device with 1/4" screw terminal for the 

incoming feed and its case as the output. This has a VF of only 0.33V so 

at my full load is only dissipating about 8 Watts.

I'm intending to use a 5000W axial transorb across the terminals of the 

power panel to provide both a level of spike protection  . . .


	




    From what spikes?



 	  Quote: 	
		     . . . but also overvoltage protection. I've conducted experiments with 

 a 9V version of the transorb and demonstrated that I can blow either my 

 endurance bus fuse or my alternator current limiter without damage to the 

 transorb. In other words an overvoltage on the alternator should blow its 

 own fuse and if any transients exist they would also be mopped up. The 

 transorb voltage is obviously critical in this. I don't want it 

 conducting in any normal situation, but do want it to let go as soon as 

 any significant overvoltage condition exists.



Without wishing to start any further spike protection or alternator 

overvoltage wars, I'm very interested in your views on this approach.


	


    What kind of alternator? And did you measure the voltage

    across the transorb just prior to fuse opening and bringing

    an ov event to heel?



     Bob . . .

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peter(at)mather.com
Guest

Posted: Tue Nov 07, 2006 5:44 am Post subject: Transorb voltage for 14V system

Bob



I didn't measure the voltage the transorb opened but it was clearly enough 

open at 12.5 volts which was the battery voltage to blow a 25amp fuse.

I'm using a prestolite externally regulated 60amp alternator with a 

Zeftronics regulator.



I don't know if there are any transients that a transorb might solve but I'm 

only intending to put one across the power panel and at $10 it seems like 

cheap insurance with no obvious downside



Best regards



Peter

---

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nuckollsr(at)cox.net
Guest

Posted: Wed Nov 08, 2006 5:55 am Post subject: Transorb voltage for 14V system

At 01:42 PM 11/7/2006 +0000, you wrote:



 	  Quote: 	
		  



Bob



I didn't measure the voltage the transorb opened but it was clearly enough 

open at 12.5 volts which was the battery voltage to blow a 25amp fuse.


	


   I'm lost. Was this experiment conducted just to see if

   you could open the 25A fuse with a conducting Transorb?

   It's not that the experiment didn't yield meaningful data,

   I'm not clear where you're proposing to connect a Transorb

   of any voltage and what you expect it to do for you.



 	  Quote: 	
		  I'm using a prestolite externally regulated 60amp alternator with a 

Zeftronics regulator.


	


   Okay, from an architecture perspective, this looks like

   Z-11. Where would you install the Transorb in Z-11?

 	  Quote: 	
		  I don't know if there are any transients that a transorb might solve but 

I'm only intending to put one across the power panel and at $10 it seems 

like cheap insurance with no obvious downside


	


   One can probably buy really cheap insurance against

   pink elephant stampedes and meteor strikes too. Of course

   it's your airplane and you can do anything you like. But for

   the benefit of 1300+ folks who watch this List go by, let

   us be clear on features that meet quantifiable and demonstrable

   design goals . . . and those that are cheap and simply feel good.



   When you ask the question about sizing a Transorb for use

   in your system, the question is unanswerable without knowing

   exactly what you expect the device to accomplish and whether

   or not it's capable of meeting your expectations.



   Bob . . .

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