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jgh2(at)charter.net
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 Posted: Mon Jul 16, 2012 4:23 am Post subject: Over-voltage Circuit Breaker Trips |
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Bob N./Fred S./et al,
Thanks for the suggestions!
My OV device was in heavy shrink wrap (not "potted") so it must be the B&C Specialities version. I exposed the trim pot and tried turning it 1.5 turns CCW and (later) 3 turns CW but the CB still trips. Since the circuit breaker and voltage regulator have been replaced the cause appears to be some hidden fault in the wiring or internal to the alternator.
The Van's alternator came with a removable plastic connector for the field wire but no positive method for securing the connector to the alternator. I made the field wire connection using an Amp female push tab. It feels secure but I'll try crimping the working end of the terminal slightly tighter on the alternator lug and revising the wire support strategy. The voltage regulator is grounded to a block of tabs on the firewall and the other connections appear secure and continuous.
Any further thoughts will be greatly appreciated.
Jack H.
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klehman(at)albedo.net
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| Posted: Mon Jul 16, 2012 7:22 am Post subject: Over-voltage Circuit Breaker Trips |
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Jack
If wired correctly understand that the OV CB can not be your problem. It
does nothing unless the OV triggers it. When the crowbar OV circuit
activates, it shorts the CB to ground and the CB pops. Bob does have a
little test procedure published on how to test or set the trip point of
the OV module. I would suggest checking the trigger voltage or replacing
the OV module.
There were a few homemade modules that were overly sensitive to small
voltage excursions and were nuisance tripping. Turning on or off any
electrical switch would often trip that unit in my aircraft. There was a
capacitor added to stabilize the voltage reference in the OV module to
fix that issue several years ago. Mine have never tripped since that
circuit mod.
I think you are doing the right thing by tracking this down just in case
the trips are being caused by a real over voltage. If you are still
confident that the regulator is OK then I'd probably dissemble and clean
every connection between the alternator, regulator, and battery. I have
not had any trouble using a PIDG connector on my alternator.
Ken
On 16/07/2012 8:22 AM, Jack Haviland wrote:
| Quote: |
Haviland<jgh2(at)charter.net>
Bob N./Fred S./et al,
Thanks for the suggestions!
My OV device was in heavy shrink wrap (not "potted") so it must be
the B&C Specialities version. I exposed the trim pot and tried
turning it 1.5 turns CCW and (later) 3 turns CW but the CB still
trips. Since the circuit breaker and voltage regulator have been
replaced the cause appears to be some hidden fault in the wiring or
internal to the alternator.
The Van's alternator came with a removable plastic connector for the
field wire but no positive method for securing the connector to the
alternator. I made the field wire connection using an Amp female push
tab. It feels secure but I'll try crimping the working end of the
terminal slightly tighter on the alternator lug and revising the wire
support strategy. The voltage regulator is grounded to a block of
tabs on the firewall and the other connections appear secure and
continuous.
Any further thoughts will be greatly appreciated.
Jack H.
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john.maccallum(at)bigpond
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| Posted: Mon Jul 16, 2012 2:44 pm Post subject: Over-voltage Circuit Breaker Trips |
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As an experiment I would obtain two .01 mfd ceramic capacitors and bypass the Terminals of the CB to ground. One on each terminal to ground and see if that fixes the problem.
Cheers
John MacCallum
Rv10 41016
Sent from my iPad
On 16/07/2012, at 22:22, Jack Haviland <jgh2(at)charter.net> wrote:
| Quote: |
Bob N./Fred S./et al,
Thanks for the suggestions!
My OV device was in heavy shrink wrap (not "potted") so it must be the B&C Specialities version. I exposed the trim pot and tried turning it 1.5 turns CCW and (later) 3 turns CW but the CB still trips. Since the circuit breaker and voltage regulator have been replaced the cause appears to be some hidden fault in the wiring or internal to the alternator.
The Van's alternator came with a removable plastic connector for the field wire but no positive method for securing the connector to the alternator. I made the field wire connection using an Amp female push tab. It feels secure but I'll try crimping the working end of the terminal slightly tighter on the alternator lug and revising the wire support strategy. The voltage regulator is grounded to a block of tabs on the firewall and the other connections appear secure and continuous.
Any further thoughts will be greatly appreciated.
Jack H.
|
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nuckolls.bob(at)aeroelect
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| Posted: Mon Jul 16, 2012 9:26 pm Post subject: Over-voltage Circuit Breaker Trips |
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At 07:22 AM 7/16/2012, you wrote:
| Quote: |
Bob N./Fred S./et al,
Thanks for the suggestions!
My OV device was in heavy shrink wrap (not "potted") so it must be
the B&C Specialities version. I exposed the trim pot and tried
turning it 1.5 turns CCW and (later) 3 turns CW but the CB still
trips. Since the circuit breaker and voltage regulator have been
replaced the cause appears to be some hidden fault in the wiring or
internal to the alternator.
|
Hmmmm . . . the fact that adjusting the
screw had no observable effects is mystifying.
If the OV module you have is fitted with a
muti-turn pot, it sounds like one of mine.
In any case, I'd like to see the one you
have. I don't have a mailing address for you
in my sales data base . . . irrespective of
where it came from, I'd like to trade with
you. Give me an address to mail you a new
one along with a stamped envelope to return
the old one to me.
Bob . . .
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Eric M. Jones
Joined: 10 Jan 2006
Posts: 565
Location: Massachusetts
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| Posted: Tue Jul 17, 2012 6:53 am Post subject: Re: Over-voltage Circuit Breaker Trips |
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| Quote: | If wired correctly understand that the OV CB can not be your problem. It does nothing unless the OV triggers it. When the crowbar OV circuit activates, it shorts the CB to ground and the CB pops. Bob does have a little test procedure published on how to test or set the trip point of
the OV module. I would suggest checking the trigger voltage or replacing
the OV module....Ken |
Au contraire, mon frere. The OV CB can easily be your problem: The OVP as currently designed WILL exceed the maximum Rated Breaking Capacity (Icn) in many or most applications.
The result of this is that many CBs, when popped for the first time are functionally and permanently ruined and might thereafter exhibit nuisance tripping. If just sitting on the shelf, be aware that someone might have tested them incorrectly. When the Icn is exceeded the CB might thereafter break at a current lower than specified on the label.
Testing the CB is easy, but must be done correctly (Google "testing circuit breakers") The fine details (like how much residual resistance is in the circuit, and the capability of the battery, and the exact type of breaker) matter.
And yes Bob disagrees, but the evidence is clear.
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_________________
Eric M. Jones
www.PerihelionDesign.com
113 Brentwood Drive
Southbridge, MA 01550
(508) 764-2072
emjones(at)charter.net |
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nuckolls.bob(at)aeroelect
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| Posted: Tue Jul 17, 2012 8:10 am Post subject: Over-voltage Circuit Breaker Trips |
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At 09:53 AM 7/17/2012, you wrote:
--> AeroElectric-List message posted by: "Eric M. Jones" <emjones(at)charter.net>
If wired correctly understand that the OV CB can not be your problem. It does nothing unless the OV triggers it. When the crowbar OV circuit activates, it shorts the CB to ground and the CB pops. Bob does have a little test procedure published on how to test or set the trip point of the OV module. I would suggest checking the trigger voltage or replacing
the OV module....Ken
Au contraire, mon frere. The OV CB can easily be your problem: The OVP as currently designed WILL exceed the maximum Rated Breaking Capacity (Icn) in many or most applications.
The result of this is that many CBs, when popped for the first time are functionally and permanently ruined and might thereafter exhibit nuisance tripping. If just sitting on the shelf, be aware that someone might have tested them incorrectly. When the Icn is exceeded the CB might thereafter break at a current lower than specified on the label.
Testing the CB is easy, but must be done correctly (Google "testing circuit breakers") The fine details (like how much residual resistance is in the circuit, and the capability of the battery, and the exact type of breaker) matter.
And yes Bob disagrees, but the evidence is clear.
"Many CBs" is non-qualified . . .
For every discussion in which I participated on this
subject I think I made it clear that the circuit breakers
being considered were the mil-spec, miniature breakers
or their commercial counterparts. I cited boat-loads
of testing for this style of breaker per Mil-C-5809
wherein one can read the requirement for continued
functionality of the device under test AFTER being
subjected to several cycles at thousands of amps in a
forced trip. I even crafted a page that spoke to circuit
breakers NOT qualified to those specifications:
http://tinyurl.com/7desrtb
The last breaker in that Shop Note had indeed been
subject to a single operation of a crow-bar ovm
module. Clearly this device was not a candidate for
use aboard aircraft whether upstream of a crowbar module
or not.
I will refer you to Mil-C-5809G, Table VII, wherein each
device under test is subjected to two operations each at
rated interruption current at sea level and rated altitude.
An exemplar rating can be found in MS3320, Table III where
they speak to test currents of 2,000 to 6,000 amps depending
on breaker rating. The breaker is to remain functional after
being subjected to those test levels.
From the Eaton catalog:
[img]cid:.0[/img]
When the Crowbar OVM products from AEC or B&C or PlanePower
are installed per recommendations for breaker selection,
design goals are being met.
This style of breaker is exceedingly unlikely to ever have
been "tested" beyond their design requirements for qualification.
I watched some testing at Beech at the 3000A fault levels.
It's not a trivial task to generate that kind of test
level . . . it's not going to be 'exceeded' by the occasional,
mis-informed user of such devices. Further, using the crow-bar
shut-down technique downstream of such breakers isn't even
going to make the breathe hard much less break a sweat. I proved
this in the Beech test labs when crowbar shutdown was provisionally
qualified to be installed on the model 38P
http://tinyurl.com/7smb4k5
and later when the B&C standby alternator was added to the type
certificate for the A36.
My brother-in-law was similarly mis-educated by some grey-beard
journeymen when he got his ticket to string wires in buildings.
The tale being circulated was that any new breaker subject to
an hard fault trip was already 'damaged goods' and required
replacement.
This is counter-intuitive to both the reasons that breakers
exist, the skill of those who design them and specify them into
finished goods. This is old science who's utility should not be
polluted by those who have never been there, done that, or read
and understood the design and test data. If any breaker is at
risk for damage the first time it is tripped, then it's NOT suited
to the task and should be replaced with one that is.
Please refrain from personalizing this as "a disagreement"
between myself and others . . . please refer to the documents
cited and explain how they are not applicable to the discussion
at hand. Let us take care that we do not propagate shop and hangar
myths here on the List. Let us be specific on just WHAT KIND
of breaker is being discussed, what it's specifications are and
how it is expected to perform.
Bob . . .
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dlj04(at)josephson.com
Guest
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| Posted: Wed Jul 18, 2012 11:05 am Post subject: Over-voltage Circuit Breaker Trips |
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If it's true that a circuit breaker is damaged and can't be used once
it's been tripped with a dead short, why would you ever use a circuit
breaker? You might as well have a fuse.
As Bob mentioned, it is possible to create a fault current in excess of
a circuit breaker's rated interrupting capacity, but you're not going to
do it with a light lead-acid (or gel, or AGM, or LiPo) battery in a
small airplane with any kind of terminals and wire between the battery
and the breaker. You *might* exceed 5000 amps with a fresh NiCd battery
from a turbine aircraft *if* the CB and OVP were connected to a bus bar
or right at the battery terminals, but that would be about what it would
take.
--
David Josephson
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nuckolls.bob(at)aeroelect
Guest
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| Posted: Wed Jul 18, 2012 6:47 pm Post subject: Over-voltage Circuit Breaker Trips |
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At 02:04 PM 7/18/2012, you wrote:
--> AeroElectric-List message posted by: dlj04 <dlj04(at)josephson.com>
If it's true that a circuit breaker is damaged and can't be used once it's been tripped with a dead short, why would you ever use a circuit breaker? You might as well have a fuse.
As Bob mentioned, it is possible to create a fault current in excess of a circuit breaker's rated interrupting capacity, but you're not going to do it with a light lead-acid (or gel, or AGM, or LiPo) battery in a small airplane with any kind of terminals and wire between the battery and the breaker. You *might* exceed 5000 amps with a fresh NiCd battery from a turbine aircraft *if* the CB and OVP were connected to a bus bar or right at the battery terminals, but that would be about what it would take.
Exactly. There was a great kerfuffle in a Walmart
bag here on the List over this kind of data:
[img]cid:7.1.0.9.0.20120718213301.01e1a780(at)aeroelectric.com.0[/img]
This is an exemplar plot of breaker performance when subjected
to over-current impulses of up to 10x rated current. Certain
individuals chose to interpret these data not only as performance
scatter but as not-to-exceed limits as well.
The discussion was rooted in a projected crowbar trip current
of something like 700A which was in fact, greatly exaggerated.
There was also some consideration of single pulse current limits
on the SCR which is core to the crowbar ov module's operation.
When installed as depicted in AEC drawings, typical trip
currents were on the order of 150 amps . . . I did some tests
at B&C at 300 amps. Far less than the max interrupt rating of
the breaker and well within the capability of the SCRs.
A hard fault on an RG battery can easily exceed 1000A but
that's still less than what these miniature breakers are
qualified to stand off.
Bob . . .
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