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CROWBARS?

 
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bobnoffs



Joined: 04 Jul 2012
Posts: 81
Location: northern wi.

PostPosted: Wed Jul 11, 2018 3:42 am    Post subject: CROWBARS? Reply with 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


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nuckolls.bob(at)aeroelect
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PostPosted: Wed Jul 11, 2018 6:54 am    Post subject: CROWBARS? Reply with quote

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
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PostPosted: Wed Jul 11, 2018 7:44 am    Post subject: CROWBARS? Reply with quote

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
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PostPosted: Wed Jul 11, 2018 7:55 pm    Post subject: CROWBARS? Reply with quote

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

---
This email has been checked for viruses by Avast antivirus software.
https://www.avast.com/antivirus






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bobnoffs



Joined: 04 Jul 2012
Posts: 81
Location: northern wi.

PostPosted: Thu Jul 12, 2018 2:46 am    Post subject: CROWBARS? Reply with 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.
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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PostPosted: Thu Jul 12, 2018 4:50 am    Post subject: CROWBARS? Reply with quote

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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