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B lead circuit breaker
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ronburnett(at)charter.net
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PostPosted: Mon Oct 08, 2018 5:19 pm    Post subject: B lead circuit breaker Reply with quote

I have a Plane Power Alternator on my RV-6A and lately with the Aero Flash strobes on at some point the B lead CB will pop. It does reset. Today I flew a 2 leg cross country for 4 hours total, all with the strobes off after the popping event 2 minutes into the flight. How would I determine if their is a problem with the strobes that might cause this problem?

Thanks for any hints.

Ron Burnett

May you have the Lord's blessings today!
Sent from my iPad


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PostPosted: Mon Oct 08, 2018 5:51 pm    Post subject: B lead circuit breaker Reply with quote

Ron,
Do you have a voltmeter in the plane? I am guessing that the circuit breaker is popping because the voltage is going too high. Maybe a voltage regulator problem.
    -- Art Z.

On Mon, Oct 8, 2018 at 8:34 PM Ron Burnett <ronburnett(at)charter.net (ronburnett(at)charter.net)> wrote:

Quote:
--> AeroElectric-List message posted by: Ron Burnett <ronburnett(at)charter.net (ronburnett(at)charter.net)>

I have a Plane Power Alternator on my RV-6A and lately with the Aero Flash strobes on  at some point the B lead CB will pop.  It does reset.  Today I flew a 2 leg cross country for 4 hours total, all with the strobes off after the popping event 2 minutes into the flight. How would I determine if their is a problem with the strobes that might cause this problem?

--
https://CheerfulCurmudgeon.com/"We do not see the world as it is. We see the world as we are."


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PostPosted: Mon Oct 08, 2018 6:26 pm    Post subject: B lead circuit breaker Reply with quote

Art,

Yes, the volt meter shows 14.2 to 14.3 range in flight, unless it spikes I guess?
Ron Burnett

May you have the Lord's blessings today!Sent from my iPad
On Oct 8, 2018, at 8:51 PM, Art Zemon <art(at)zemon.name (art(at)zemon.name)> wrote:
Quote:
Ron,
Do you have a voltmeter in the plane? I am guessing that the circuit breaker is popping because the voltage is going too high. Maybe a voltage regulator problem.
-- Art Z.

On Mon, Oct 8, 2018 at 8:34 PM Ron Burnett <ronburnett(at)charter.net (ronburnett(at)charter.net)> wrote:

Quote:
--> AeroElectric-List message posted by: Ron Burnett <ronburnett(at)charter.net (ronburnett(at)charter.net)>

I have a Plane Power Alternator on my RV-6A and lately with the Aero Flash strobes on at some point the B lead CB will pop. It does reset. Today I flew a 2 leg cross country for 4 hours total, all with the strobes off after the popping event 2 minutes into the flight. How would I determine if their is a problem with the strobes that might cause this problem?

--
https://CheerfulCurmudgeon.com/"We do not see the world as it is. We see the world as we are."






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PostPosted: Mon Oct 08, 2018 7:37 pm    Post subject: B lead circuit breaker Reply with quote

At 08:18 PM 10/8/2018, you wrote:
Quote:
--> AeroElectric-List message posted by: Ron Burnett <ronburnett(at)charter.net>

I have a Plane Power Alternator on my RV-6A and lately with the Aero Flash strobes on at some point the B lead CB will pop. It does reset. Today I flew a 2 leg cross country for 4 hours total, all with the strobes off after the popping event 2 minutes into the flight. How would I determine if their is a problem with the strobes that might cause this problem?

Thanks for any hints.

Ron Burnett

What size is your alternator. What size is
your B-lead breaker.



Bob . . .


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user9253



Joined: 28 Mar 2008
Posts: 1326
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PostPosted: Tue Oct 09, 2018 4:36 am    Post subject: Re: B lead circuit breaker Reply with quote

The most likely cause of the "B" lead breaker popping is a bad connection on the breaker. A bad connection causes heat. If the connections are secure, then the breaker could be faulty. The B lead breaker should not trip for any reason except a short circuit in the B lead or inside of the alternator.
Check the breaker connections.


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PostPosted: Tue Oct 09, 2018 9:08 am    Post subject: B lead circuit breaker Reply with quote

Bob,The B lead is 5 amps and I will check but I believe I have a 60 amp alternator. I have a dual EFII ignition that normally runs 12.5 amps without strobes and wig wags which are the old Van’s style bulbs which about double it with both on.
Ron Burnett
RV-6A O360

Sent from my iPhone

On Oct 8, 2018, at 10:36 PM, Robert L. Nuckolls, III <nuckolls.bob(at)aeroelectric.com (nuckolls.bob(at)aeroelectric.com)> wrote:
Quote:
At 08:18 PM 10/8/2018, you wrote:
Quote:
--> AeroElectric-List message posted by: Ron Burnett <ronburnett(at)charter.net (ronburnett(at)charter.net)>

I have a Plane Power Alternator on my RV-6A and lately with the Aero Flash strobes on at some point the B lead CB will pop. It does reset. Today I flew a 2 leg cross country for 4 hours total, all with the strobes off after the popping event 2 minutes into the flight. How would I determine if their is a problem with the strobes that might cause this problem?

Thanks for any hints.

Ron Burnett

What size is your alternator. What size is
your B-lead breaker.



Bob . . .


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user9253



Joined: 28 Mar 2008
Posts: 1326
Location: Riley TWP Michigan

PostPosted: Tue Oct 09, 2018 9:41 am    Post subject: Re: B lead circuit breaker Reply with quote

Usually the "B" lead refers to the heavy wire that carries the alternator output current. At 5 amps, you must be talking about a different circuit. Regardless, check the circuit breaker connections to be sure that they are secure.

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PostPosted: Tue Oct 09, 2018 9:54 am    Post subject: B lead circuit breaker Reply with quote

At 09:27 AM 10/9/2018, you wrote:
Quote:
Bob,
The B lead is 5 amps and I will check but I believe I have a 60 amp alternator. I have a dual EFII ignition that normally runs 12.5 amps without strobes and wig wags which are the old Van’s style bulbs which about double it with both on.

Okay, that's not the b-lead protection . . . it's
the field supply breaker which, if memory serves,
is upstream of their crowbar ov protection system.
If that breaker is nuisance tripping, then it's
likely the result of (1) poor ov sensor design that's
making it 'twitchy' and/or (2) some stimulus in the
system is causing the minor equivalent of a
load-dump overshoot from the regulator.

Does the tripping go away with the strobes off?



Bob . . .


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kenryan



Joined: 20 Oct 2009
Posts: 310

PostPosted: Tue Oct 09, 2018 10:26 am    Post subject: B lead circuit breaker Reply with quote

Do circuit breakers trip due to high voltage, or due to current overload?

On Mon, Oct 8, 2018 at 10:30 PM Ron Burnett <ronburnett(at)charter.net (ronburnett(at)charter.net)> wrote:

Quote:
Art,

Yes, the volt meter shows 14.2 to 14.3 range in flight, unless it spikes I guess?
Ron Burnett

May you have the Lord's blessings today!Sent from my iPad
On Oct 8, 2018, at 8:51 PM, Art Zemon <art(at)zemon.name (art(at)zemon.name)> wrote:
Quote:
Ron,
Do you have a voltmeter in the plane? I am guessing that the circuit breaker is popping because the voltage is going too high. Maybe a voltage regulator problem.
    -- Art Z.

On Mon, Oct 8, 2018 at 8:34 PM Ron Burnett <ronburnett(at)charter.net (ronburnett(at)charter.net)> wrote:

Quote:
--> AeroElectric-List message posted by: Ron Burnett <ronburnett(at)charter.net (ronburnett(at)charter.net)>

I have a Plane Power Alternator on my RV-6A and lately with the Aero Flash strobes on  at some point the B lead CB will pop.  It does reset.  Today I flew a 2 leg cross country for 4 hours total, all with the strobes off after the popping event 2 minutes into the flight. How would I determine if their is a problem with the strobes that might cause this problem?

--
https://CheerfulCurmudgeon.com/"We do not see the world as it is. We see the world as we are."








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PostPosted: Tue Oct 09, 2018 3:12 pm    Post subject: Re: B lead circuit breaker Reply with quote

Circuit breakers trip due to excessive current. Depending on the circuit breaker design, excessive heat can also trip a circuit breaker. That heat could be due to a loose terminal on the circuit breaker. High voltage could indirectly trip an alternator-field breaker if an over voltage protection device shorts to ground, thus causing excessive current.

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PostPosted: Tue Oct 09, 2018 4:27 pm    Post subject: B lead circuit breaker Reply with quote

Thanks Joe. That's what I thought, but an earlier post alluded to voltage causing breaker trip. --Ken

On Tue, Oct 9, 2018 at 4:19 PM user9253 <fransew(at)gmail.com (fransew(at)gmail.com)> wrote:

Quote:
--> AeroElectric-List message posted by: "user9253" <fransew(at)gmail.com (fransew(at)gmail.com)>

Circuit breakers trip due to excessive current.  Depending on the circuit breaker design, excessive heat can also trip a circuit breaker.  That heat could be due to a loose terminal on the circuit breaker.  High voltage could indirectly trip an alternator-field breaker if an over voltage protection device shorts to ground, thus causing excessive current.

--------
Joe Gores




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PostPosted: Tue Oct 09, 2018 5:14 pm    Post subject: B lead circuit breaker Reply with quote

Ken,

We started with the thread being mis-titled, and wrong terms being used. Here's the deal. If his alternator has crowbar style overvoltage protection, *and* its regulator is having a hard time 'tracking' sudden changes in current demand, what could be happening is this: When the strobe is operating, current demand can go from zero to fairly high, and back to zero with the flashing of the strobe.  If the regulator can't track the sudden change from high current to near zero current, then alternator output voltage can spike high enough to trip the overvoltage protection circuit. When it trips, it 'crowbars' (shorts) the field supply line to ground. This causes a current spike that exceeds the field circuit breaker (mis-titled as 'B-lead circuit breaker') rating, tripping the breaker and shutting down the alternator.

If I were the OP, I'd try a flight with a lot of electrical loads on the alternator, so that the fluctuating strobe load is only a small percentage of total load. If the nuisance trip disappears, it would seem likely that he has a regulator problem.

Charlie

On 10/9/2018 7:25 PM, Ken Ryan wrote:

Quote:
Thanks Joe. That's what I thought, but an earlier post alluded to voltage causing breaker trip. --Ken

On Tue, Oct 9, 2018 at 4:19 PM user9253 <fransew(at)gmail.com (fransew(at)gmail.com)> wrote:

Quote:
--> AeroElectric-List message posted by: "user9253" <fransew(at)gmail.com (fransew(at)gmail.com)>

Circuit breakers trip due to excessive current.  Depending on the circuit breaker design, excessive heat can also trip a circuit breaker.  That heat could be due to a loose terminal on the circuit breaker.  High voltage could indirectly trip an alternator-field breaker if an over voltage protection device shorts to ground, thus causing excessive current.

--------
Joe Gores


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PostPosted: Tue Oct 09, 2018 5:34 pm    Post subject: B lead circuit breaker Reply with quote

Bob is correct in that it is the 5 amp Field CB that pops. First time was a year ago, once. Then 3 times on an 8 hour 4 leg cross country. First time Wig wags and strobe was on. Turns wig wags off, left strobes on, repopped a few minutes later, reset and landed. This was at the end of nearly four hours of flight.

Four days later took off with strobes on and CB popped. Turned strobe off and flew 4 hours home with no issues. Will check connection on Field wire to CB.
The voltage regulator is obviously built in the alternator.
That is all I know, which isn’t much.
Thanks,
Ron Burnett

May you have the Lord's blessings today!Sent from my iPad
On Oct 9, 2018, at 8:02 AM, Ken Ryan <keninalaska(at)gmail.com (keninalaska(at)gmail.com)> wrote:
Quote:
Do circuit breakers trip due to high voltage, or due to current overload?

On Mon, Oct 8, 2018 at 10:30 PM Ron Burnett <ronburnett(at)charter.net (ronburnett(at)charter.net)> wrote:

Quote:
Art,

Yes, the volt meter shows 14.2 to 14.3 range in flight, unless it spikes I guess?
Ron Burnett

May you have the Lord's blessings today!Sent from my iPad
On Oct 8, 2018, at 8:51 PM, Art Zemon <art(at)zemon.name (art(at)zemon.name)> wrote:
Quote:
Ron,
Do you have a voltmeter in the plane? I am guessing that the circuit breaker is popping because the voltage is going too high. Maybe a voltage regulator problem.
-- Art Z.

On Mon, Oct 8, 2018 at 8:34 PM Ron Burnett <ronburnett(at)charter.net (ronburnett(at)charter.net)> wrote:

Quote:
--> AeroElectric-List message posted by: Ron Burnett <ronburnett(at)charter.net (ronburnett(at)charter.net)>

I have a Plane Power Alternator on my RV-6A and lately with the Aero Flash strobes on at some point the B lead CB will pop. It does reset. Today I flew a 2 leg cross country for 4 hours total, all with the strobes off after the popping event 2 minutes into the flight. How would I determine if their is a problem with the strobes that might cause this problem?

--
https://CheerfulCurmudgeon.com/"We do not see the world as it is. We see the world as we are."










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Joined: 28 Mar 2008
Posts: 1326
Location: Riley TWP Michigan

PostPosted: Tue Oct 09, 2018 6:21 pm    Post subject: Re: B lead circuit breaker Reply with quote

The vast majority of electrical problems are due to bad connections. Check every connection in the charging circuit and in the strobe circuit. Take apart connectors, clean them and put them back together.

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PostPosted: Wed Oct 10, 2018 7:54 am    Post subject: B lead circuit breaker Reply with quote

At 09:21 PM 10/9/2018, you wrote:
Quote:
--> AeroElectric-List message posted by: "user9253" <fransew(at)gmail.com>

The vast majority of electrical problems are due to bad connections. Check every connection in the charging circuit and in the strobe circuit. Take apart connectors, clean them and put them back together.

I disagree . . . I can recall only one 'degraded
connection' that was so elusive that it took several
'teams' over a month to chase down . . . but only
because it was so buried in the hardware (pushed
back pin in a pressure bulkhead connector) and
only manifested at low temperatures requiring a
test flight to 41,000 feet to cool the thing
off before we could even begin to look.

All other bad connection manifested with rather
gross symptoms like those we've discussed here
on the List concerning switch failures, burned
terminals, etc.

This problem would be easy to 'divide and
conquer' if you had a data acquisition system
you could clip to the bus and watch for
transients that might be antagonizing the
ov protection system on the alternator.

Assuming that the design dynamics for the ov
sensor are correct, an ov trip can originate
from one source only . . . the alternator.
A too high output from the alternator suggests
that the regulator has lost control due
to failure.

On thing you might try is to replace the 5A
breaker. This will help you decide if
the 5A breaker has (1) degraded with age
(rare but not unheard of) but is indeed being
'crow barred' open by a triggering of the
alternator's ov protection.

Does this alternator have an externally mounted
ov module? Early versions of the PP
machines did. It was a plastic box mounted
to the back of the alternator. A wire ran
into the alternator through a cooling hole.


Bob . . .


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BARRY CHECK 6



Joined: 15 Mar 2011
Posts: 730

PostPosted: Wed Oct 10, 2018 9:20 am    Post subject: B lead circuit breaker Reply with quote

On Wednesday, October 10, 2018, Robert L. Nuckolls, III <nuckolls.bob(at)aeroelectric.com (nuckolls.bob(at)aeroelectric.com)> wrote:
Quote:
At 09:21 PM 10/9/2018, you wrote:
Quote:
--> AeroElectric-List message posted by: "user9253" <fransew(at)gmail.com (fransew(at)gmail.com)>

The vast majority of electrical problems are due to bad connections.  Check every connection in the charging circuit and in the strobe circuit.  Take apart connectors, clean them and put them back together.

  I disagree . . . 


Barry - I have to TOTALLY AGREE!
I do aircraft repairs weekly and the number of non working, lights, intercoms and antennas that come into the hanger almost weekly is probably way more than all the fellows here on the list see in a their life time...  Just had one last week Friday.  If I had to put a number to it, 90% were due to bad contacts due to corrosion.  You can not visually inspect a ground connection.  It must be undone, wire brushed, NEW star lock washers replaced and tightened securely...  Yes, tightened even beyond specs.  Then, you can spray some chromate paint over the connection for a bit more corrosion protection.
Wait a second Bob, aren’t you the one the advocates the use of Dielectric Grease on connections just to prevent corrosion?
I agree with the Dielectric Grease idea.  Been doing it for decades.
Talking about tracing CRAZY electrical issues.  TWICE, I have come across bulbs that check good on continuity yet DO NOT LIGHT!
No, it was not corrosion, not this time.  Care to take a SWAG at it?
I would bet the airport that no one would guess.
The failed bulbs were Marker Nav Light Bulbs.  —- hint, hint.
On a 12 VDC system the bulbs are really a 24 VDC bulb.  And on a 24 VDC system, yes you guessed it, they are really a 48 VDC BULB.  It is done that way to extend the life of the bulb.  Vibration is your enemy as well as weather.
So, what happens is the filament breaks but stays in contact with the ‘post’.  I have seen the problem happen twice and both times it was at the mounting post of the filament.
The low current of the DMM checks the bulb as good.  But when operational voltage and CURRENT is applied the break heats up and opens.
My Rule:  Do not believe the DMM, apply a separate and full voltage & current to the bulb.  If it lights, LQQK elsewhere for the problem.
Good time to Check Grounds.
Barry 
--
Barry
"Chop'd Liver"
If you wash your hands before you go to the bathroom you may have the makings of a Crew Chief.


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PostPosted: Wed Oct 10, 2018 6:15 pm    Post subject: B lead circuit breaker Reply with quote

Quote:
If I had to put a number to it, 90% were due to bad contacts due to corrosion.
You can not visually inspect a ground connection. It must be undone, wire brushed,
NEW star lock washers replaced and tightened securely... Yes, tightened even
beyond specs. Then, you can spray some chromate paint over the connection
for a bit more corrosion protection.

I've never seen this kind of effort expended on a ground
to the airframe. A bizjet has HUNDREDS of such grounds.
All are made up with flat and clean faying surfaces assembled
to the proper compression specs (torque). The natural
crush that occurs in the terminal creates the gas-tight
interface that excludes moisture+air; hence corrosion.

A ground connection can look pretty bad on the surface
of components but still maintain electrical integrity
if assemble properly in the first place.


Quote:
Wait a second Bob, aren't you the one the advocates the use of
Dielectric Grease on connections just to prevent corrosion?
I agree with the Dielectric Grease idea. Been doing it for decades.

It sure doesn't hurt but recall that the purpose of
the grease is to fill voids in the surfaces that did
not get closed when the joint was made up in the
first place. A void full of grease won't admit
moisture+air.

Here's a ground cluster in the nose of a Beechjet

http://aeroelectric.com/Pictures/Grounding/MVC-699X.JPG

Bright? yes. Clean? yes. Grease? No, Overspray? No.
This installation was in s/n RK24, an experimental
flight test aircraft which was 20+ years old at the time.

If the airplane is operated in a particularly
wicked environs, like the sea coast, the surfaces
on and around such joints will enjoy protection
from accelerated corrosion but if the joint was
properly made up in the first place, the service
life of the joint is probably not extended much.


Quote:
Talking about tracing CRAZY electrical issues. TWICE, I have come
across bulbs that check good on continuity yet DO NOT LIGHT!
No, it was not corrosion, not this time. Care to take a SWAG at it?
I would bet the airport that no one would guess.The failed bulbs were Marker Nav Light Bulbs. hint, hint.
On a 12 VDC system the bulbs are reaally a 24 VDC bulb.
And on a 24 VDC system, yes you guessed it, they are really
a 48 VDC BULB. It is done that way to extend the life of
the bulb.

Where is this idea published? In chapter 12 of the
'Connection I speak to the relationship between
applied voltage and life/current/intensity of
the typical incandescent bulb.

[img]cid:.0[/img]
For every ~5% reduction in voltage from the
bulb's design center, life approximately doubles.
So in your hypothetical 50% drop from design
center, bulb life goes up HUNDREDS of times.
At the same time, light output drops to about
10% of the design center . . . and in fact
is quite redish in color.

[img]cid:.1[/img]
An exemplar navigation lamp is in the 21-26watt class
and operates at a color temperature strongly suggesting
a design optimized for light output/color . . . and NOT
de rated for service life.


Quote:
Vibration is your enemy as well as weather.

Also discussed in Chapter 12. In fact, we suggested a
keep-warm circuit to hold incandescent lamps at about
10% of nominal operating voltage when turned OFF. This
keeps the tungsten filament ABOVE the brittle/ductile
transition temperature making the bulb more resistant
to both vibration and warm-up shock when turned ON.

Yeah, the air around the airplane can carry a host
of antagonistic stressed into vulnerable locations,
like the metal parts of a lamp socket. Dielectric grease
on the shell and tip of a lamp base is a good thing.

Quote:
So, what happens is the filament breaks but stays in contact with
the ‘post’. I have seen the problem happen twice and both
times it was at the mounting post of the filament.
The low current of the DMM checks the bulb as good. But when
operational voltage and CURRENT is applied the break heats up and opens.

So does the bulb come back on when it cools only to
immediately go dark again?


Bob . . .


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racerjerry



Joined: 15 Dec 2009
Posts: 184
Location: Deer Park, NY

PostPosted: Thu Oct 11, 2018 5:28 am    Post subject: Re: B lead circuit breaker Reply with quote

Bob, I found an old Cessna Service Letter SE 72-15 that relates to over-sensitivity of the Cessna over-voltage protection circuit. Basically, they just add a big electrolytic capacitor (500uf 50v) across the sensor to help absorb short term voltage spikes and reduce sensitivity. Doesn't cure the problem at it's source, but it might make some false tripping go away.

And YES, I think crowbar circuits can be kinda' tough on alternator field circuit breakers and could cause eventual degradation; especially after a long series of false trips. Brings to mind a U.L. report of a homeowner who habitually 'tested' his residential circuit breakers using a screwdriver. As you might suspect, the outcome was not good.

SE 72-15 https://support.cessna.com/custsupt/contacts/pubs/ourpdf.pdf?as_id=34475

Jerry King


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nuckolls.bob(at)aeroelect
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PostPosted: Thu Oct 11, 2018 8:20 am    Post subject: B lead circuit breaker Reply with quote

At 08:28 AM 10/11/2018, you wrote:
Quote:
--> AeroElectric-List message posted by: "racerjerry" <gnking2(at)verizon.net>

Bob, I found an old Cessna service bulletin SE 72-15 that relates to over-sensitivity of the Cessna over-voltage protection circuit. Basically, they just add a big electrolytic capacitor (500uf 50v) across the sensor to help absorb short term voltage spikes and reduce sensitivity. Doesn't cure the problem at it's source, but it might make some false tripping go away.

Really! Hadn't seen that one. I'd like to get a copy.
The 3-wire 'firecracker' OV module used on the single
engine airplanes is a derivative of a design I proposed
to Cessna back about 1970. I left Cessna in 69 to
work on the Mobilizer hospital patient transporter but
I was still very much in contact with the old gang at
the airplane patch.

A few weeks after I had lunch with one of the guys
in the electrical group and gave him the details, I
was told that the idea had been rejected in favor of
another approach. It was several years later that I
discovered that they had out sourced the design to
an outfit in Emporia KS and that indeed, the original
concept was found acceptable.

Hadn't heard about any nuisance tripping cures.


Quote:
And YES, I think crowbar circuits can be kinda' tough on alternator field circuit breakers and could cause eventual degradation; especially after a long series of false trips. Brings to mind a U.L. report of a homeowner who habitually 'tested' his residential circuit breakers using a screwdriver. As you might suspect, the outcome was not good.

Can't speak to breakers in a home but typical
breakers popular in aircraft are qualified to some
pretty robust requirements not the least of which is
endurance. Here's an exemplar call-out for a Klixon
product.

[img]cid:.0[/img]


http://aeroelectric.com/Pictures/Breakers/Klixon_1.jpg


When I first proposed the crowbar shutdown method for alternators
in aircraft, the idea was driven by a Beech procurement spec
that called for any offering of an ov 'relay' be tested under
worst case conditions and withstand 50 simulated ov events
on a test stand.

Reasonably priced relays at that time were hard pressed to open
the field on a 100A, 28v alternator in full-bore runaway
50 times in a row.

Read an article in ELECTRONICS that spoke to crowbar systems
used in computer power supplies and it made sense for our
problem as well. NO SERIES switching except for the breaker
which was only being asked to do what it was designed to do . . .
break a large, RESISTIVE load.

Ability of the system to withstand repeated trips was
not limited by anything I was supplying . . . but by
the ability of the circuit breaker to shoulder the stresses.
A breaker with stellar qualification numbers.

Note: not ALL breakers are so qualified. Here's one
example . . .

http://aeroelectric.com/Pictures/Breakers/Breaker_Failure_1a.jpg

Short answer is that crowbar trips are a 'walk in the
park' for the field supply breaker.


Bob . . .


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nuckolls.bob(at)aeroelect
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PostPosted: Thu Oct 11, 2018 11:29 am    Post subject: B lead circuit breaker Reply with quote

Quote:

SE 72-15 https://support.cessna.com/custsupt/contacts/pubs/ourpdf.pdf?as_id=34475

Jerry King

Interesting . . . I wonder what was different in aircraft
after those serial blocks. I 'salted' the idea
into Cessna for the 3-wire firecracker about 1970,
very shortly after I left Cessna. So it was very
early in the deployment of the product. I'm wondering
if they upsized the value of the timing capacitor
in production and used the SB as a 'band aid' for
units already fielded . . .

[img]cid:.0[/img]

Purely hypothetical now. It would be cool to see
if any of the gray beards still around would
remember the details . . . I suspect they're
all gone by now. They were well into their
careers . . . I was about 27 at the time.

Thanks for the find Jerry!



Bob . . .


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