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CROWBARS?

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bobnoffs

Joined: 04 Jul 2012
Posts: 132
Location: northern wi.

Posted: Wed Jul 11, 2018 3:42 am Post subject: CROWBARS?

hi all,

 in the past a crowbar would stop the current from an overvoltage source quick enough to prevent avionics damage.

 is that really needed any more? 

 i have a honda [viking] engine with auto accessories. i don't hear of cars blowing out their glass dashboards.

 when i asked b and c about a ''crowbar'' they said theirs was only recommended for a permanent magnet alternator. 

 what are others doing with auto alternators?

 thanks

 bob noffs

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nuckolls.bob(at)aeroelect
Guest

Posted: Wed Jul 11, 2018 6:54 am Post subject: CROWBARS?

At 06:42 AM 7/11/2018, you wrote:

  	  Quote: 	
		  --> AeroElectric-List message posted by: "bobnoffs" <icubob(at)gmail.com>



 hi all,

  in the past a crowbar would stop the current from an overvoltage source quick enough to prevent avionics damage.

  is that really needed any more? 	


    OV protection is a legacy component of virtually

    all voltage regulators for aviation. You have two

    approaches to vetting component reliability: (1) Analyze

    or demonstrate component failure rates on the

    or of 1 in 10 to the 9th flight hours, i.e. never

    fails or (2) ASSUME that it will fail and

    mitigate that failure down to a low-risk maintenance

    event.



      



  	  Quote: 	
		   i have a honda [viking] engine with auto accessories. i don't hear of cars blowing out their glass dashboards.

  when i asked b and c about a 'crowbar' they said theirs was only recommended for a permanent magnet alternator. 

  what are others doing with auto alternators? 	


   Plane Power modifies the automotive alternators

   to derive field excitation from a source external

   to the alternator. Same with B&C.



   PP retains the built in regulator . . . for a time

   they added crowbar ov protection externally. Don't

   know what they do now. But even if they don't provide

   ov protection, it can be easily added to the field

   supply feeder. B&C's controllers for their automotive

   adaptations have ov protection built in . . . their

   PM product installations include/recommend the

   crowbar ov protection device which COULD be used

   on any other system that is not otherwise fitted

   with ov protection. 



 [img]cid:.0[/img]



   But if you have a candidate alternator regulator

   that you have reason to believe it never fails

   then you're certainly free to forego ov protaection.



 

 

   Bob . . .

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ceengland7(at)gmail.com
Guest

Posted: Wed Jul 11, 2018 7:44 am Post subject: CROWBARS?

On 7/11/2018 6:42 AM, bobnoffs wrote:

 	  Quote: 	
		   



 hi all,

   in the past a crowbar would stop the current from an overvoltage source quick enough to prevent avionics damage.

   is that really needed any more?

   i have a honda [viking] engine with auto accessories. i don't hear of cars blowing out their glass dashboards.

   when i asked b and c about a 'crowbar' they said theirs was only recommended for a permanent magnet alternator.

   what are others doing with auto alternators?

   thanks

   bob noffs



I think their answer was framed in the assumption that you're using only 
	


their products. The B&C regulators for conventional alternators have 

overvoltage protection built into them.



I've read 'rumors on the interwebs' that the latest auto tech often 

builds voltage regulation into the vehicle's system computer, that 

controls virtually everything else in the vehicle, too. Not a big deal 

to build in overvoltage protection too, in that environment. It's 

unlikely that the Viking is using the stock auto controller (pray that 

it doesn't; too many 'protections' in auto controllers that can kill you 

in an a/c).



I've run my dirt-simple RV-4 without OV protection for a long time, but 

with expensive avionics in the -7 I'm building, I *will* have OV protection.



Charlie



---

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jimkale(at)roadrunner.com
Guest

Posted: Wed Jul 11, 2018 7:55 pm Post subject: CROWBARS?

Different alternators have different failure mode.     I recently saw a friend’s Cessna 172 after it suffered some sort of over voltage condition.  If.   I had not seen it,  I would not have believed the damage.     Every electrical component was fried.   The insulation on every wire was burned.  I did not know an alternator was capable of that sort of damage.  I do know a crowbar would have   Prevented it though.  Like I said, if I had not personally seen the damage I would not have believed how bad it was.  Every wire and electrical component  in the airplane had to be replaced.  It is possible that not all alternators are capable of that sort of failure mode.  But it sure opened my eyes and I would not want to have been on board when it occurred.  Jim Kale, Enterprise, AL  

Sent from my iPhone

 	  Quote: 	
		   On Jul 11, 2018, at 10:45 AM, Charlie England <ceengland7(at)gmail.com> wrote:

> On 7/11/2018 6:42 AM, bobnoffs wrote:

> 

> 

> hi all,

>  in the past a crowbar would stop the current from an overvoltage source quick enough to prevent avionics damage.

>  is that really needed any more?

>  i have a honda [viking] engine with auto accessories. i don't hear of cars blowing out their glass dashboards.

>  when i asked b and c about a 'crowbar' they said theirs was only recommended for a permanent magnet alternator.

>  what are others doing with auto alternators?

>  thanks

>  bob noffs

> 

 I think their answer was framed in the assumption that you're using only their products. The B&C regulators for conventional alternators have overvoltage protection built into them.

 I've read 'rumors on the interwebs' that the latest auto tech often builds voltage regulation into the vehicle's system computer, that controls virtually everything else in the vehicle, too. Not a big deal to build in overvoltage protection too, in that environment. It's unlikely that the Viking is using the stock auto controller (pray that it doesn't; too many 'protections' in auto controllers that can kill you in an a/c).

 I've run my dirt-simple RV-4 without OV protection for a long time, but with expensive avionics in the -7 I'm building, I *will* have OV protection.

 Charlie

 ---

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bobnoffs

Joined: 04 Jul 2012
Posts: 132
Location: northern wi.

Posted: Thu Jul 12, 2018 2:46 am Post subject: CROWBARS?

well, i guess i should wire in a crowbar. seems like it should be pretty

straight forward to have it break the circuit to the field. i will take a

look in bob's book for ideas and go from there.

 thanks everyone for the advice.

 bob noffs



On Wed, Jul 11, 2018 at 10:54 PM, James Kale <jimkale(at)roadrunner.com> wrote:



[quote] 

 jimkale(at)roadrunner.com>



 Different alternators have different failure mode.     I recently saw a

 friend’s Cessna 172 after it suffered some sort of over voltage condition.

 If.   I had not seen it,  I would not have believed the damage.     Every

 electrical component was fried.   The insulation on every wire was burned

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nuckolls.bob(at)aeroelect
Guest

Posted: Thu Jul 12, 2018 4:50 am Post subject: CROWBARS?

At 05:45 AM 7/12/2018, you wrote:

  	  Quote: 	
		  well, i guess i should wire in a crowbar. seems like it should be pretty straight forward to have it break the circuit to the field. i will take a look in bob's book for ideas and go from there. 	


   The crowbar ov protection module can be added to

   any system wherein alternator field power is

   taken through a typical 5A breaker. The

   module is wired from field supply line to

   ground at any point downstream of that

   breaker. You can find examples in the Z-figures.



 

 

   Bob . . .

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