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ronburnett(at)charter.net
Guest

Posted: Mon Oct 08, 2018 5:19 pm Post subject: B lead circuit breaker

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

art(at)zemon.name
Guest

Posted: Mon Oct 08, 2018 5:51 pm Post subject: B lead circuit breaker

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.

Â  Â  -- 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 onÂ  at some point the B lead CB will pop.Â  It does reset.Â  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."

ronburnett(at)charter.net
Guest

Posted: Mon Oct 08, 2018 6:26 pm Post subject: B lead circuit breaker

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."

nuckolls.bob(at)aeroelect
Guest

Posted: Mon Oct 08, 2018 7:37 pm Post subject: B lead circuit breaker

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 . . .

user9253

Joined: 28 Mar 2008
Posts: 1921
Location: Riley TWP Michigan

Posted: Tue Oct 09, 2018 4:36 am Post subject: Re: B lead circuit breaker

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.

_________________
Joe Gores

ronburnett(at)charter.net
Guest

Posted: Tue Oct 09, 2018 9:08 am Post subject: B lead circuit breaker

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 Vanâ€™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 . . .

user9253

Joined: 28 Mar 2008
Posts: 1921
Location: Riley TWP Michigan

Posted: Tue Oct 09, 2018 9:41 am Post subject: Re: B lead circuit breaker

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.

_________________
Joe Gores

nuckolls.bob(at)aeroelect
Guest

Posted: Tue Oct 09, 2018 9:54 am Post subject: B lead circuit breaker

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 Vanâ€™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 . . .

kenryan

Joined: 20 Oct 2009
Posts: 426

Posted: Tue Oct 09, 2018 10:26 am Post subject: B lead circuit breaker

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.

Â  Â  -- 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 onÂ  at some point the B lead CB will pop.Â  It does reset.Â  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."

user9253

Joined: 28 Mar 2008
Posts: 1921
Location: Riley TWP Michigan

Posted: Tue Oct 09, 2018 3:12 pm Post subject: Re: B lead circuit breaker

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

kenryan

Joined: 20 Oct 2009
Posts: 426

Posted: Tue Oct 09, 2018 4:27 pm Post subject: B lead circuit breaker

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.Â  Depending on the circuit breaker design, excessive heat can also trip a circuit breaker.Â  That heat could be due to a loose terminal on the circuit breaker.Â  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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ceengland7(at)gmail.com
Guest

Posted: Tue Oct 09, 2018 5:14 pm Post subject: B lead circuit breaker

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

           

           --------

           Joe Gores

         	
       

     	
     

     	          		Virus-free. www.avast.com 		 	 [url=#DAB4FAD8-2DD7-40BB-A1B8-4E2AA1F9FDF2] [/url]

ronburnett(at)charter.net
Guest

Posted: Tue Oct 09, 2018 5:34 pm Post subject: B lead circuit breaker

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 isnâ€™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."

user9253

Joined: 28 Mar 2008
Posts: 1921
Location: Riley TWP Michigan

Posted: Tue Oct 09, 2018 6:21 pm Post subject: Re: B lead circuit breaker

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.

_________________
Joe Gores

nuckolls.bob(at)aeroelect
Guest

Posted: Wed Oct 10, 2018 7:54 am Post subject: B lead circuit breaker

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 . . .

BARRY CHECK 6

Joined: 15 Mar 2011
Posts: 738

Posted: Wed Oct 10, 2018 9:20 am Post subject: B lead circuit breaker

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.Â  Check every connection in the charging circuit and in the strobe circuit.Â  Take apart connectors, clean them and put them back together. 	


 Â  I disagree . . .Â 

	




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

Wait a second Bob, arenâ€™t you the one the advocates the use of Dielectric Grease on connections just to prevent corrosion?

I agree with the Dielectric Grease idea.Â  Been doing it for decades.

Talking about tracing CRAZY electrical issues.Â  TWICE, I have come across bulbs that check good on continuity yet DO NOT LIGHT!

No, it was not corrosion, not this time.Â  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. Â â€”- hint, hint.

On a 12 VDC system the bulbs are really a 24 VDC bulb.Â  And on a 24 VDC system, yes you guessed it, they are really a 48 VDC BULB.Â  It is done that way to extend the life of the bulb.Â  Vibration is your enemy as well as weather.

So, what happens is the filament breaks but stays in contact with the â€˜postâ€™.Â  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.Â  But when operational voltage and CURRENT is applied the break heats up and opens.

My Rule: Â Do not believe the DMM, apply a separate and full voltage & current to the bulb.Â  If it lights, LQQK elsewhere for the problem.

Good time to Check Grounds.

BarryÂ 

-- 

Barry

"Chop'd Liver"

If you wash your hands before you go to the bathroom you may have the makings of a Crew Chief.

nuckolls.bob(at)aeroelect
Guest

Posted: Wed Oct 10, 2018 6:15 pm Post subject: B lead circuit breaker

 	  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 â€˜postâ€™.Â  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.Â  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: 202
Location: Deer Park, NY

Posted: Thu Oct 11, 2018 5:28 am Post subject: Re: B lead circuit breaker

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

_________________
Jerry King

nuckolls.bob(at)aeroelect
Guest

Posted: Thu Oct 11, 2018 8:20 am Post subject: B lead circuit breaker

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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Posted: Thu Oct 11, 2018 11:29 am Post subject: B lead circuit breaker

 	  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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