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ceengland7(at)gmail.com
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 Posted: Fri Jul 18, 2014 11:17 am Post subject: Are 'serial' contactors really needed? |
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Someone's recent question/comment about master & starter contactors caused my ARADD (aviation related attention deficit disorder) to kick in.
I'm just beginning the wiring process on an electrically dependent auto engine conversion in an RV-7.Â
Given the typical automotive starter with self-contained contactor/bendix, and a starter contactor, could a case be made for switching the cockpit loads with smaller (lower coil current draw) contactors or even heavy duty switches, and using only the heavy starter contactor between the battery & starter?Â
I'm envisioning the starter button activating both the contactor and the starter's built-in contactor. This way, if either sticks, current would still be removed from the starter when the button is released. There would be no voltage available on the starter's heavy wire except during starting, as is current practice (pardon the pun). The only failed-on single point should be the momentary push-to-start button.
Motivation is saving a few ounces of contactor weight, and more importantly, saving the 2+amps of draw by the normal master contactor. If I elect to go with a single alternator (weight, simplicity), the 2 amp draw of the main contactor is a significant percentage of load in a failed alternator situation. Note that similar engine installs have flown for 45 minutes or more (typically plenty of time to find a runway) while operating 'battery only' using  common 18-20 AH SLA battery installations. Â
Thoughts?
Charlie
[quote][b]
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peter(at)sportingaero.com
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| Posted: Fri Jul 18, 2014 11:04 pm Post subject: Are 'serial' contactors really needed? |
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Charlie,
I believe the driver for a master contacted has been the airworthiness regs - FAR23 and CS23 - which require one switch to shut off all electrical power, or words to that effect. If the load is 10s of amps (heated pitot, incandescent landing light, stack of old radios, etc) then a contactor was the only sensible way to go.
There are now good reasons to question that kind of requirement, and do what you suggest. In my aeroplane, that has a conventional engine. The typical current draw is 8amps, which could be switched by a regular switch. Some aerobatic aeroplanes do that, by they often only use an SD-8. Also the load switched on first operation is likely to be small if all the services are switched off on shut down. I see no fundamental reason not to do what you suggest, although you may have to be a little more careful in how you operate.
The only draw back is the stuck starter relay scenario. Using a double pole momentary may work, but you could also consider a separate switch in the line to the starter piggy-back solenoid. That way if the starter relay fails closed at least it will be obvious.
Peter
On Jul 18, 2014 8:35 PM, "Charlie England" <ceengland7(at)gmail.com (ceengland7(at)gmail.com)> wrote:[quote] Someone's recent question/comment about master & starter contactors caused my ARADD (aviation related attention deficit disorder) to kick in.
I'm just beginning the wiring process on an electrically dependent auto engine conversion in an RV-7.Â
Given the typical automotive starter with self-contained contactor/bendix, and a starter contactor, could a case be made for switching the cockpit loads with smaller (lower coil current draw) contactors or even heavy duty switches, and using only the heavy starter contactor between the battery & starter?Â
I'm envisioning the starter button activating both the contactor and the starter's built-in contactor. This way, if either sticks, current would still be removed from the starter when the button is released. There would be no voltage available on the starter's heavy wire except during starting, as is current practice (pardon the pun). The only failed-on single point should be the momentary push-to-start button.
Motivation is saving a few ounces of contactor weight, and more importantly, saving the 2+amps of draw by the normal master contactor. If I elect to go with a single alternator (weight, simplicity), the 2 amp draw of the main contactor is a significant percentage of load in a failed alternator situation. Note that similar engine installs have flown for 45 minutes or more (typically plenty of time to find a runway) while operating 'battery only' using  common 18-20 AH SLA battery installations. Â
Thoughts?
Charlie
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ist" target="_blank">http://www.matronics.com/Navigator?AeroElectric-List
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acub(at)neo.rr.com
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| Posted: Sat Jul 19, 2014 5:01 am Post subject: Are 'serial' contactors really needed? |
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you may have replied to me by accident!
that wasn't my question.
my question was on a overvoltage module (ovm) from B&C using 60 amp breaker instead of a 5 amp will it hurt the ovm and will it work properly?
you may want to refer to my email again for all details thank you !
John
Sent from my iPhone
On Jul 19, 2014, at 2:53 AM, Peter Pengilly <peter(at)sportingaero.com (peter(at)sportingaero.com)> wrote:
[quote]
Charlie,
I believe the driver for a master contacted has been the airworthiness regs - FAR23 and CS23 - which require one switch to shut off all electrical power, or words to that effect. If the load is 10s of amps (heated pitot, incandescent landing light, stack of old radios, etc) then a contactor was the only sensible way to go.
There are now good reasons to question that kind of requirement, and do what you suggest. In my aeroplane, that has a conventional engine. The typical current draw is 8amps, which could be switched by a regular switch. Some aerobatic aeroplanes do that, by they often only use an SD-8. Also the load switched on first operation is likely to be small if all the services are switched off on shut down. I see no fundamental reason not to do what you suggest, although you may have to be a little more careful in how you operate.
The only draw back is the stuck starter relay scenario. Using a double pole momentary may work, but you could also consider a separate switch in the line to the starter piggy-back solenoid. That way if the starter relay fails closed at least it will be obvious.
Peter
On Jul 18, 2014 8:35 PM, "Charlie England" <ceengland7(at)gmail.com (ceengland7(at)gmail.com)> wrote: | Quote: | Someone's recent question/comment about master & starter contactors caused my ARADD (aviation related attention deficit disorder) to kick in.
I'm just beginning the wiring process on an electrically dependent auto engine conversion in an RV-7.
Given the typical automotive starter with self-contained contactor/bendix, and a starter contactor, could a case be made for switching the cockpit loads with smaller (lower coil current draw) contactors or even heavy duty switches, and using only the heavy starter contactor between the battery & starter?
I'm envisioning the starter button activating both the contactor and the starter's built-in contactor. This way, if either sticks, current would still be removed from the starter when the button is released. There would be no voltage available on the starter's heavy wire except during starting, as is current practice (pardon the pun). The only failed-on single point should be the momentary push-to-start button.
Motivation is saving a few ounces of contactor weight, and more importantly, saving the 2+amps of draw by the normal master contactor. If I elect to go with a single alternator (weight, simplicity), the 2 amp draw of the main contactor is a significant percentage of load in a failed alternator situation. Note that similar engine installs have flown for 45 minutes or more (typically plenty of time to find a runway) while operating 'battery only' using common 18-20 AH SLA battery installations.
Thoughts?
Charlie
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[b]
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kleh(at)dialupatcost.ca
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| Posted: Sat Jul 19, 2014 5:05 am Post subject: Are 'serial' contactors really needed? |
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In regards to electric dependent engines, it is common to NOT feed it
through a battery "contactor" anyway. My engine runs off the battery bus
and will keep running if the master switch/contactor is off.
My battery contactors draw less than an amp each. Do consider the
architectures here that would de-energize them in a dead alternator
situation anyway.
Note that unlike continuous duty battery contactors, starter contactors
draw several amps, are rated for intermittent use only, and are designed
to interrupt large starter currents. There has been some question as to
whether a battery contactor will in fact open if the starter is running.
I will test that if my starter solenoid ever sticks on as my subaru
starter is wired through the battery contactor with no separate starter
contactor other than the integral starter solenoid. That seemed
reasonable to me and hopefully slightly safer than how all my cars are
wired. It also seemed reasonable to try preserve much of the intent of
killing all non essential electrical wiring with a contactor located at
the battery. The battery, with its ability to deliver large currents, is
the most dangerous electrical item on board.
Ken
On 19/07/2014 2:53 AM, Peter Pengilly wrote:
| Quote: | Charlie,
I believe the driver for a master contacted has been the airworthiness
regs - FAR23 and CS23 - which require one switch to shut off all
electrical power, or words to that effect. If the load is 10s of amps
(heated pitot, incandescent landing light, stack of old radios, etc)
then a contactor was the only sensible way to go.
There are now good reasons to question that kind of requirement, and do
what you suggest. In my aeroplane, that has a conventional engine. The
typical current draw is 8amps, which could be switched by a regular
switch. Some aerobatic aeroplanes do that, by they often only use an
SD-8. Also the load switched on first operation is likely to be small if
all the services are switched off on shut down. I see no fundamental
reason not to do what you suggest, although you may have to be a little
more careful in how you operate.
The only draw back is the stuck starter relay scenario. Using a double
pole momentary may work, but you could also consider a separate switch
in the line to the starter piggy-back solenoid. That way if the starter
relay fails closed at least it will be obvious.
Peter
On Jul 18, 2014 8:35 PM, "Charlie England" <ceengland7(at)gmail.com
<mailto:ceengland7(at)gmail.com>> wrote:
Someone's recent question/comment about master & starter contactors
caused my ARADD (aviation related attention deficit disorder) to
kick in.
I'm just beginning the wiring process on an electrically dependent
auto engine conversion in an RV-7.
Given the typical automotive starter with self-contained
contactor/bendix, and a starter contactor, could a case be made for
switching the cockpit loads with smaller (lower coil current draw)
contactors or even heavy duty switches, and using only the heavy
starter contactor between the battery & starter?
I'm envisioning the starter button activating both the contactor and
the starter's built-in contactor. This way, if either sticks,
current would still be removed from the starter when the button is
released. There would be no voltage available on the starter's heavy
wire except during starting, as is current practice (pardon the
pun). The only failed-on single point should be the momentary
push-to-start button.
Motivation is saving a few ounces of contactor weight, and more
importantly, saving the 2+amps of draw by the normal master
contactor. If I elect to go with a single alternator (weight,
simplicity), the 2 amp draw of the main contactor is a significant
percentage of load in a failed alternator situation. Note that
similar engine installs have flown for 45 minutes or more (typically
plenty of time to find a runway) while operating 'battery only'
using common 18-20 AH SLA battery installations.
Thoughts?
Charlie
|
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nuckolls.bob(at)aeroelect
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| Posted: Sat Jul 19, 2014 6:05 am Post subject: Are 'serial' contactors really needed? |
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At 07:59 AM 7/19/2014, you wrote:
| Quote: | you may have replied to me by accident!
that wasn't my question.
my question was on a overvoltage module (ovm) from B&C using 60 amp
breaker instead of a 5 amp will it hurt the ovm and will it work properly?
|
Need to see your schematic . . . how do
you propose to use the crowbar ovm in
conjunction with a 60A breaker?
These devices are not intended to be used
in any manner other than what's depicted
in AEC or B&C drawings.
Bob . . .
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nuckolls.bob(at)aeroelect
Guest
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| Posted: Sat Jul 19, 2014 6:34 am Post subject: Are 'serial' contactors really needed? |
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In regards to electric dependent engines, it is common to NOT feed it through a battery "contactor" anyway. My engine runs off the battery bus and will keep running if the master switch/contactor is off.
Feeders from an always-hot bus are allowed in TC
aircraft when protected at 5A or less. This is
a crash-safety concern. For the OBAM aircraft,
one is free to wire it like any other vehicle
including automobiles that generally don't included
battery disconnect switching (except for some
racing jurisdictions).
Note that unlike continuous duty battery contactors, starter contactors draw several amps, are rated for intermittent use only, and are designed to interrupt large starter currents. There has been some question as to whether a battery contactor will in fact open if the starter is running.
Was that question posed here on the List?
The answer is YES . . . it will break the
power path to a stuck starter contactor . . .
The battery, with its ability to deliver large currents, is the most dangerous electrical item on board.
Precisely. I recall a conversation with an accident
investigator some years back who made the
anecdotal observation that when the airplane
burned after impact, it's battery was more
likely to be still inside a rather compact arrangement
of wreckage.
When the wreckage was widely scattered with
the battery separated from the rest
of the airplane, the incidences of post crash
fire seemed lower.
The typical current draw is 8amps, which could be switched by a regular
switch. Some aerobatic aeroplanes do that, by they often only use an
SD-8. Also the load switched on first operation is likely to be small if
all the services are switched off on shut down. I see no fundamental
reason not to do what you suggest, although you may have to be a little
more careful in how you operate.
The battery master disconnect does not have to be
a contactor. The first airplane in which I took
dual instruction had a fat toggle switch and
a fat starter push-button . . . no contactors
at all.
I'm envisioning the starter button activating both the contactor and
the starter's built-in contactor. This way, if either sticks,
current would still be removed from the starter when the button is
released. There would be no voltage available on the starter's heavy
wire except during starting, as is current practice (pardon the
pun). The only failed-on single point should be the momentary
push-to-start button.
Incidences of starter contactor sticking are
rare . . . the risk goes up markedly when the
pilot attempts to get the engine going with
a seriously discharged or perhaps an un-flightworthy
battery. Render due diligence in the maintenance
of your battery and don't worry about 'sicking
contactors'.
There'no prohibition for using the starter's
bui9lt in contactor-solenoid but be aware of
the extra abusive nature of pull-in spikes
with increased ware on the starter switch
cnotacts. This over-looked feature was root cause
for an AD against ACS-510 key-switches in
a bit of bureaucratic paper-thrashing that
at first produced a worthless 'fix' and was
later revised to add a spike suppression
diode to the contactor.
Bill and I pondered this phenomenon at
length in the early days of the B&C lightweight
starters and elected to side-step the
issue in it's entirety by suggesting an
EXTERNAL contactor with a lower operating
current and BUILT IN suppression diode.
This was a one-solution fits all contingency
installations and had nothing to do with
worries for contactors sticking shut.
Bob . . . [quote][b]
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nuckolls.bob(at)aeroelect
Guest
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| Posted: Sat Jul 19, 2014 6:36 am Post subject: Are 'serial' contactors really needed? |
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See http://tinyurl.com/ott27no
for an explanation of the extra-ordinarily
abusive inrush currents for the built-in
contactor-solenoid. This phenomenon has been
extra-ordinarily hard on key-starts switches in
cars too.
Bob . . . [quote][b]
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ceengland7(at)gmail.com
Guest
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| Posted: Sat Jul 19, 2014 7:18 am Post subject: Are 'serial' contactors really needed? |
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On 7/19/2014 9:34 AM, Robert L. Nuckolls, III wrote:
| Quote: |
In regards to electric dependent engines, it is common to NOT feed it through a battery "contactor" anyway. My engine runs off the battery bus and will keep running if the master switch/contactor is off.
Feeders from an always-hot bus are allowed in TC
aircraft when protected at 5A or less. This is
a crash-safety concern. For the OBAM aircraft,
one is free to wire it like any other vehicle
including automobiles that generally don't included
battery disconnect switching (except for some
racing jurisdictions).
Note that unlike continuous duty battery contactors, starter contactors draw several amps, are rated for intermittent use only, and are designed to interrupt large starter currents. There has been some question as to whether a battery contactor will in fact open if the starter is running.
Was that question posed here on the List?
The answer is YES . . . it will break the
power path to a stuck starter contactor . . .
The battery, with its ability to deliver large currents, is the most dangerous electrical item on board.
Precisely. I recall a conversation with an accident
investigator some years back who made the
anecdotal observation that when the airplane
burned after impact, it's battery was more
likely to be still inside a rather compact arrangement
of wreckage.
When the wreckage was widely scattered with
the battery separated from the rest
of the airplane, the incidences of post crash
fire seemed lower.
The typical current draw is 8amps, which could be switched by a regular
switch. Some aerobatic aeroplanes do that, by they often only use an
SD-8. Also the load switched on first operation is likely to be small if
all the services are switched off on shut down. I see no fundamental
reason not to do what you suggest, although you may have to be a little
more careful in how you operate.
The battery master disconnect does not have to be
a contactor. The first airplane in which I took
dual instruction had a fat toggle switch and
a fat starter push-button . . . no contactors
at all.
I'm envisioning the starter button activating both the contactor and
the starter's built-in contactor. This way, if either sticks,
current would still be removed from the starter when the button is
released. There would be no voltage available on the starter's heavy
wire except during starting, as is current practice (pardon the
pun). The only failed-on single point should be the momentary
push-to-start button.
Incidences of starter contactor sticking are
rare . . . the risk goes up markedly when the
pilot attempts to get the engine going with
a seriously discharged or perhaps an un-flightworthy
battery. Render due diligence in the maintenance
of your battery and don't worry about 'sicking
contactors'.
There'no prohibition for using the starter's
bui9lt in contactor-solenoid but be aware of
the extra abusive nature of pull-in spikes
with increased ware on the starter switch
cnotacts. This over-looked feature was root cause
for an AD against ACS-510 key-switches in
a bit of bureaucratic paper-thrashing that
at first produced a worthless 'fix' and was
later revised to add a spike suppression
diode to the contactor.
Bill and I pondered this phenomenon at
length in the early days of the B&C lightweight
starters and elected to side-step the
issue in it's entirety by suggesting an
EXTERNAL contactor with a lower operating
current and BUILT IN suppression diode.
This was a one-solution fits all contingency
installations and had nothing to do with
worries for contactors sticking shut.
Bob . . .
|
Just read your article (from link in subsequent post)on dual windings in starter solenoids; very helpful.
From your comments above, it sounds like I could simply wire the starter like the B&C design in fig 6 of the article, but directly from the battery to run the starter. This would remove the need for the typical heavy (and high coil current) master contactor, allowing a lighter duty relay or switch for the in-cabin loads.
Thanks,
Charlie
[quote][b]
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acub(at)neo.rr.com
Guest
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| Posted: Sat Jul 19, 2014 7:30 am Post subject: Are 'serial' contactors really needed? |
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why am I getting everybody's questions and answers to me from other people
Sent from my iPhone
On Jul 19, 2014, at 10:36 AM, "Robert L. Nuckolls, III" <nuckolls.bob(at)aeroelectric.com (nuckolls.bob(at)aeroelectric.com)> wrote:
[quote] See http://tinyurl.com/ott27no
for an explanation of the extra-ordinarily
abusive inrush currents for the built-in
contactor-solenoid. This phenomenon has been
extra-ordinarily hard on key-starts switches in
cars too.
Bob . . .
[b]
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jmjones2000(at)mindspring
Guest
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| Posted: Sat Jul 19, 2014 7:57 am Post subject: Are 'serial' contactors really needed? |
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Jon,
You must have subscribed to the AeroElectric connection email list. Anytime an email is sent to "aeroelectric-list(at)matronics.com (aeroelectric-list(at)matronics.com)" you will receive a copy of that email.
It is sort of a think tank with some very knowledgeable people that read and respond to questions.
Hope this answers your question.
Justin
On Jul 19, 2014, at 7:15, jon molek <acub(at)neo.rr.com (acub(at)neo.rr.com)> wrote:
[quote]why am I getting everybody's questions and answers to me from other people
Sent from my iPhone
On Jul 19, 2014, at 10:36 AM, "Robert L. Nuckolls, III" <nuckolls.bob(at)aeroelectric.com (nuckolls.bob(at)aeroelectric.com)> wrote:
| Quote: | See http://tinyurl.com/ott27no
for an explanation of the extra-ordinarily
abusive inrush currents for the built-in
contactor-solenoid. This phenomenon has been
extra-ordinarily hard on key-starts switches in
cars too.
Bob . . .
D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D
lectric-List"">http://www.matronics.com/Navigator?AeroElectric-List
D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D
//forums.matronics.com
D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D
ot;">http://www.matronics.com/contribution
D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D
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acub(at)neo.rr.com
Guest
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| Posted: Sat Jul 19, 2014 8:50 am Post subject: Are 'serial' contactors really needed? |
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yes thank you that explains it I know how to stop it but my main question was never answered maybe you can answer it
originally wrote
I'm installing a overvoltage module (Ovm 14) from B&C and wiring it as suggested in the external regulatored diagram. (of B&C)
problem is the regulator IN shows it's hooked to a 5 amp breaker my system is the Cessna type system that has a 60 amp breaker only will the 60 amp breaker work properly meaning if I hook to that will it kick it when overloaded ?& or will it burnout the Ovm?
or do you have another means of hooking the Ovm up ?(normally they use the field it has a 5amp)
john
Sent from my iPhone
On Jul 19, 2014, at 11:56 AM, Justin Jones <jmjones2000(at)mindspring.com (jmjones2000(at)mindspring.com)> wrote:
[quote]Jon,
You must have subscribed to the AeroElectric connection email list. Anytime an email is sent to "aeroelectric-list(at)matronics.com (aeroelectric-list(at)matronics.com)" you will receive a copy of that email.
It is sort of a think tank with some very knowledgeable people that read and respond to questions.
Hope this answers your question.
Justin
On Jul 19, 2014, at 7:15, jon molek <acub(at)neo.rr.com (acub(at)neo.rr.com)> wrote:
| Quote: | why am I getting everybody's questions and answers to me from other people
Sent from my iPhone
On Jul 19, 2014, at 10:36 AM, "Robert L. Nuckolls, III" <nuckolls.bob(at)aeroelectric.com (nuckolls.bob(at)aeroelectric.com)> wrote:
| Quote: | See http://tinyurl.com/ott27no
for an explanation of the extra-ordinarily
abusive inrush currents for the built-in
contactor-solenoid. This phenomenon has been
extra-ordinarily hard on key-starts switches in
cars too.
Bob . . .
D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D
lectric-List"">http://www.matronics.com/Navigator?AeroElectric-List
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ot;">http://www.matronics.com/contribution
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//forums.matronics.com
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ot;">http://www.matronics.com/contribution
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nuckolls.bob(at)aeroelect
Guest
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| Posted: Sat Jul 19, 2014 9:02 am Post subject: Are 'serial' contactors really needed? |
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Just read your article (from link in subsequent post)on dual windings in starter solenoids; very helpful.
From your comments above, it sounds like I could simply wire the starter like the B&C design in fig 6 of the article, but directly from the battery to run the starter. This would remove the need for the typical heavy (and high coil current) master contactor, allowing a lighter duty relay or switch for the in-cabin loads.
Thanks,
Charlie
You wrote:
Motivation is saving a few ounces of contactor weight, and more importantly, saving the 2+amps of draw by the normal master contactor.
Actually, 1A or less . . . See
http://tinyurl.com/mpcgp3t
and . . .
http://tinyurl.com/k6bwdqo
If I elect to go with a single alternator (weight, simplicity), the 2 amp draw of the main contactor is a significant percentage of load in a failed alternator situation.
What size alternator do you anticipate
installing?
Note that similar engine installs have flown for 45 minutes or more (typically plenty of time to find a runway) while operating 'battery only' using  common 18-20 AH SLA battery installations.
Is this a day-vfr fun machine or
do plan to travel? Is 45 minutes
your battery-only endurance
target . . . or would fuel endurance
be more attractive? Have you
crafted a load analysis for the purpose
of sizing the battery to your battery-
only endurance target?
Bob . . . [quote][b]
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nuckolls.bob(at)aeroelect
Guest
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| Posted: Sat Jul 19, 2014 9:27 am Post subject: Are 'serial' contactors really needed? |
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I'm installing a overvoltage module (Ovm 14) from B&C and wiring it as suggested in the external regulatored diagram. (of B&C) problem is the regulator IN shows it's hooked to a 5 amp breaker my system is the Cessna type system that has a 60 amp breaker only will the 60 amp breaker work properly meaning if I hook to that will it kick it when overloaded ?& or will it burnout the Ovm? or do you have another means of hooking the Ovm up ?(normally they use the field it has a 5amp)
If the system to which you are adding
ov protection is a 'Cessna type', then there
are two breakers. The 60A is the alternator
b-lead on the panel, Recommend that be replaced
with 60A current limiter on the firewall.
Also 5A breaker for the alternator field supply.
This breaker would feed one side of the
split-rocker battery-master/alternator switch. The
OVM would mount right at them master
to the feedpoint that's wired to the 5A
breaker.
Bob . . .
Bob . . . [quote][b]
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ceengland7(at)gmail.com
Guest
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| Posted: Sat Jul 19, 2014 10:39 am Post subject: Are 'serial' contactors really needed? |
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On 7/19/2014 12:01 PM, Robert L. Nuckolls, III wrote:
| Quote: | Just read your article (from link in subsequent post)on dual windings in starter solenoids; very helpful.
From your comments above, it sounds like I could simply wire the starter like the B&C design in fig 6 of the article, but directly from the battery to run the starter. This would remove the need for the typical heavy (and high coil current) master contactor, allowing a lighter duty relay or switch for the in-cabin loads.
Thanks,
Charlie
You wrote:
Motivation is saving a few ounces of contactor weight, and more importantly, saving the 2+amps of draw by the normal master contactor.
Actually, 1A or less . . . See
http://tinyurl.com/mpcgp3t
and . . .
http://tinyurl.com/k6bwdqo
If I elect to go with a single alternator (weight, simplicity), the 2 amp draw of the main contactor is a significant percentage of load in a failed alternator situation.
What size alternator do you anticipate
installing?
Note that similar engine installs have flown for 45 minutes or more (typically plenty of time to find a runway) while operating 'battery only' using  common 18-20 AH SLA battery installations.
Is this a day-vfr fun machine or
do plan to travel? Is 45 minutes
your battery-only endurance
target . . . or would fuel endurance
be more attractive? Have you
crafted a load analysis for the purpose
of sizing the battery to your battery-
only endurance target?
Bob . . .
|
Wow; to speak Mississippi, who'd a thunk that <11 watts could heat that chunk of metal to 160 degrees in free air.
Alternator is a Denso off a Suzuki Samurai; 60 A. Total continuous load is ~25A; calculated load can reduce to <16A for engine-only operation, but I suspect that it goes significantly lower in the real world. The reason is, as I've mentioned, similar engines (Mazda rotary with electronic injection/ignition & automotive high pressure electric fuel pump), have flown for >45 minutes on battery-only using 'typical' 18-20AH SLA batteries.
The plane will be used day-vfr initially, but will have a panel that's capable of IFR flight (if I ever become capable). Load for IFR would go up by ~15A max (heated pitot).
Yes, I'd like to have the fuel endurance option. I actually have a 2nd Denso alternator, and a 20A dynamo, one of which may yet find its way onto the engine as 2nd source of energy. But it's really hard to add the weight & complexity for a vfr only a/c.
Charlie
[quote][b]
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user9253
Joined: 28 Mar 2008
Posts: 1927
Location: Riley TWP Michigan
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| Posted: Sun Jul 20, 2014 1:25 am Post subject: Re: Are 'serial' contactors really needed? |
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| Quote: | | my question was on a overvoltage module (ovm) from B&C using 60 amp breaker instead of a 5 amp will it hurt the ovm and will it work properly? |
A 60 amp breaker will most likely damage the OVM. No, it will not work properly and could cause a fire. An alternator has two separate circuits: field circuit and stator circuit. The 60 amp breaker protects the battery and wiring from a shorted alternator stator winding. A 5 amp breaker protects the electrical system from a shorted alternator field. The crowbar type OVM is designed to trip a 5 amp breaker.
Joe
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peter(at)sportingaero.com
Guest
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| Posted: Sun Jul 20, 2014 2:18 am Post subject: Are 'serial' contactors really needed? |
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I was replying to Charlie's questions about using a switch instead of a contactor - that's why it is addressed to Charlie.
Why try to re-design the B&C implementation? Circuit breakers are reasonably cheap, just go buy a 5a c/b!
I don't know how the B&C circuit was designed, but using a 60A c/b will probably mean it doesn't work properly (takes too long to work) so I suspect something expensive you are trying to protect will be damaged.
Peter
On 19/07/2014 13:59, jon molek wrote:
[quote] you may have replied to me by accident!
that wasn't my question.
my question was on a overvoltage module (ovm) from B&C using 60 amp breaker instead of a 5 amp will it hurt the ovm and will it work properly?
 you may want to refer to my email again for all details thank you !
John
Sent from my iPhone
On Jul 19, 2014, at 2:53 AM, Peter Pengilly <peter(at)sportingaero.com (peter(at)sportingaero.com)> wrote:
| Quote: |
Charlie,
I believe the driver for a master contacted has been the airworthiness regs - FAR23 and CS23 - which require one switch to shut off all electrical power, or words to that effect. If the load is 10s of amps (heated pitot, incandescent landing light, stack of old radios, etc) then a contactor was the only sensible way to go.
There are now good reasons to question that kind of requirement, and do what you suggest. In my aeroplane, that has a conventional engine. The typical current draw is 8amps, which could be switched by a regular switch. Some aerobatic aeroplanes do that, by they often only use an SD-8. Also the load switched on first operation is likely to be small if all the services are switched off on shut down. I see no fundamental reason not to do what you suggest, although you may have to be a little more careful in how you operate.
The only draw back is the stuck starter relay scenario. Using a double pole momentary may work, but you could also consider a separate switch in the line to the starter piggy-back solenoid. That way if the starter relay fails closed at least it will be obvious.
Peter
On Jul 18, 2014 8:35 PM, "Charlie England" <ceengland7(at)gmail.com (ceengland7(at)gmail.com)> wrote: | Quote: | Someone's recent question/comment about master & starter contactors caused my ARADD (aviation related attention deficit disorder) to kick in.
I'm just beginning the wiring process on an electrically dependent auto engine conversion in an RV-7.Â
Given the typical automotive starter with self-contained contactor/bendix, and a starter contactor, could a case be made for switching the cockpit loads with smaller (lower coil current draw) contactors or even heavy duty switches, and using only the heavy starter contactor between the battery & starter?Â
I'm envisioning the starter button activating both the contactor and the starter's built-in contactor. This way, if either sticks, current would still be removed from the starter when the button is released. There would be no voltage available on the starter's heavy wire except during starting, as is current practice (pardon the pun). The only failed-on single point should be the momentary push-to-start button.
Motivation is saving a few ounces of contactor weight, and more importantly, saving the 2+amps of draw by the normal master contactor. If I elect to go with a single alternator (weight, simplicity), the 2 amp draw of the main contactor is a significant percentage of load in a failed alternator situation. Note that similar engine installs have flown for 45 minutes or more (typically plenty of time to find a runway) while operating 'battery only' using  common 18-20 AH SLA battery installations. Â
Thoughts?
Charlie
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acub(at)neo.rr.com
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| Posted: Sun Jul 20, 2014 3:14 am Post subject: Are 'serial' contactors really needed? |
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I tried using five amp breaker it won't kick the alternator in
have to have a 60 amp I guess
Sent from my iPhone
On Jul 20, 2014, at 6:14 AM, Peter Pengilly <peter(at)sportingaero.com (peter(at)sportingaero.com)> wrote:
[quote] I was replying to Charlie's questions about using a switch instead of a contactor - that's why it is addressed to Charlie.
Why try to re-design the B&C implementation? Circuit breakers are reasonably cheap, just go buy a 5a c/b!
I don't know how the B&C circuit was designed, but using a 60A c/b will probably mean it doesn't work properly (takes too long to work) so I suspect something expensive you are trying to protect will be damaged.
Peter
On 19/07/2014 13:59, jon molek wrote:
| Quote: | you may have replied to me by accident!
that wasn't my question.
my question was on a overvoltage module (ovm) from B&C using 60 amp breaker instead of a 5 amp will it hurt the ovm and will it work properly?
you may want to refer to my email again for all details thank you !
John
Sent from my iPhone
On Jul 19, 2014, at 2:53 AM, Peter Pengilly <peter(at)sportingaero.com (peter(at)sportingaero.com)> wrote:
| Quote: |
Charlie,
I believe the driver for a master contacted has been the airworthiness regs - FAR23 and CS23 - which require one switch to shut off all electrical power, or words to that effect. If the load is 10s of amps (heated pitot, incandescent landing light, stack of old radios, etc) then a contactor was the only sensible way to go.
There are now good reasons to question that kind of requirement, and do what you suggest. In my aeroplane, that has a conventional engine. The typical current draw is 8amps, which could be switched by a regular switch. Some aerobatic aeroplanes do that, by they often only use an SD-8. Also the load switched on first operation is likely to be small if all the services are switched off on shut down. I see no fundamental reason not to do what you suggest, although you may have to be a little more careful in how you operate.
The only draw back is the stuck starter relay scenario. Using a double pole momentary may work, but you could also consider a separate switch in the line to the starter piggy-back solenoid. That way if the starter relay fails closed at least it will be obvious.
Peter
On Jul 18, 2014 8:35 PM, "Charlie England" <ceengland7(at)gmail.com (ceengland7(at)gmail.com)> wrote: | Quote: | Someone's recent question/comment about master & starter contactors caused my ARADD (aviation related attention deficit disorder) to kick in.
I'm just beginning the wiring process on an electrically dependent auto engine conversion in an RV-7.
Given the typical automotive starter with self-contained contactor/bendix, and a starter contactor, could a case be made for switching the cockpit loads with smaller (lower coil current draw) contactors or even heavy duty switches, and using only the heavy starter contactor between the battery & starter?
I'm envisioning the starter button activating both the contactor and the starter's built-in contactor. This way, if either sticks, current would still be removed from the starter when the button is released. There would be no voltage available on the starter's heavy wire except during starting, as is current practice (pardon the pun). The only failed-on single point should be the momentary push-to-start button.
Motivation is saving a few ounces of contactor weight, and more importantly, saving the 2+amps of draw by the normal master contactor. If I elect to go with a single alternator (weight, simplicity), the 2 amp draw of the main contactor is a significant percentage of load in a failed alternator situation. Note that similar engine installs have flown for 45 minutes or more (typically plenty of time to find a runway) while operating 'battery only' using common 18-20 AH SLA battery installations.
Thoughts?
Charlie
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acub(at)neo.rr.com
Guest
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| Posted: Sun Jul 20, 2014 3:24 am Post subject: Are 'serial' contactors really needed? |
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you're saying instead of hooking it to the reg in from the alternator to the regulator ,Hook it to the field which has a five amp
that's what I thought I would do but didn't know if it would work
do I still need to change to a voltage limiter on the firewall ?if so what is it ?where do I get one?
Thank you
John
Sent from my iPhone
On Jul 19, 2014, at 1:26 PM, "Robert L. Nuckolls, III" <nuckolls.bob(at)aeroelectric.com (nuckolls.bob(at)aeroelectric.com)> wrote:
[quote]
I'm installing a overvoltage module (Ovm 14) from B&C and wiring it as suggested in the external regulatored diagram. (of B&C) problem is the regulator IN shows it's hooked to a 5 amp breaker my system is the Cessna type system that has a 60 amp breaker only will the 60 amp breaker work properly meaning if I hook to that will it kick it when overloaded ?& or will it burnout the Ovm? or do you have another means of hooking the Ovm up ?(normally they use the field it has a 5amp)
If the system to which you are adding
ov protection is a 'Cessna type', then there
are two breakers. The 60A is the alternator
b-lead on the panel, Recommend that be replaced
with 60A current limiter on the firewall.
Also 5A breaker for the alternator field supply.
This breaker would feed one side of the
split-rocker battery-master/alternator switch. The
OVM would mount right at them master
to the feedpoint that's wired to the 5A
breaker.
Bob . . .
Bob . . .
[b]
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acub(at)neo.rr.com
Guest
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| Posted: Sun Jul 20, 2014 3:31 am Post subject: Are 'serial' contactors really needed? |
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that's my thinking also but according to the drawing it says to hook to the regulator and not the field if he wanted to hook it to the field it would've said so
so I'm confused do I split the regulator in or split the field the field has the breaker on & the regulator in doesn't
Sent from my iPhone
| Quote: | On Jul 20, 2014, at 5:25 AM, "user9253" <fransew(at)gmail.com> wrote:
> my question was on a overvoltage module (ovm) from B&C using 60 amp breaker instead of a 5 amp will it hurt the ovm and will it work properly?
A 60 amp breaker will most likely damage the OVM. No, it will not work properly and could cause a fire. An alternator has two separate circuits: field circuit and stator circuit. The 60 amp breaker protects the battery and wiring from a shorted alternator stator winding. A 5 amp breaker protects the electrical system from a shorted alternator field. The crowbar type OVM is designed to trip a 5 amp breaker.
Joe
--------
Joe Gores
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=426989#426989
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acub(at)neo.rr.com
Guest
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| Posted: Sun Jul 20, 2014 3:36 am Post subject: Are 'serial' contactors really needed? |
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it sounds to me it's saying hook it to a five amp breaker the controls the system
Sent from my iPhone
| Quote: | On Jul 20, 2014, at 5:25 AM, "user9253" <fransew(at)gmail.com> wrote:
> my question was on a overvoltage module (ovm) from B&C using 60 amp breaker instead of a 5 amp will it hurt the ovm and will it work properly?
A 60 amp breaker will most likely damage the OVM. No, it will not work properly and could cause a fire. An alternator has two separate circuits: field circuit and stator circuit. The 60 amp breaker protects the battery and wiring from a shorted alternator stator winding. A 5 amp breaker protects the electrical system from a shorted alternator field. The crowbar type OVM is designed to trip a 5 amp breaker.
Joe
--------
Joe Gores
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=426989#426989
|
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