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apilot2(at)gmail.com
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 Posted: Fri Feb 01, 2008 7:00 am Post subject: Alternator Circuit Breaker |
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Two different ways of saying the same thing. Sizing fuse/CB to max load you wish to allow, should be the same or less than max load the wire can carry. Nothing wrong with being more conservative than what 43.13 says the wire will carry, in picking your CB/fuse size.
On Feb 1, 2008 7:30 AM, linn Walters <pitts_pilot(at)bellsouth.net (pitts_pilot(at)bellsouth.net)> wrote:
[quote] --> RV10-List message posted by: linn Walters <pitts_pilot(at)bellsouth.net (pitts_pilot(at)bellsouth.net)>
Tim Olson wrote:
| Quote: | --> RV10-List message posted by: Tim Olson <Tim(at)MyRV10.com (Tim(at)MyRV10.com)>
>
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| Quote: | That's exactly my reasoning on using a 60A fuse (despite my 70A
alternator). The fact is, if I find myself drawing 60A off
my alternator, something is not right at all. None of my
avionics or equipment can draw that much, so my battery or
> wires are shorted or something. You don't size your fuse by
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| Quote: | the alternator, you size it to the max load you care to see
before you blow.
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Not really true. The size of the breaker is there to protect the wire,
which could cause a fire if it gets a large escess of current. The size
of the wire is dictated by the load. True of small wires and big ones too.
Linn
do not archive
[b]
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Tim Olson
Joined: 25 Jan 2007
Posts: 2879
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| Posted: Fri Feb 01, 2008 7:25 am Post subject: Alternator Circuit Breaker |
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Yes, that's true too. So basically:
1. You pick your alternator to fit your load. Plan for
perhaps 15-20% over capacity as a minimum, so that
you never work your alternator at 100%
2. You pick your wire size that will handle the load that
your alternator can provide, again, err'ing on
the high side so if you have a 70A alternator, make
sure your wire can handle > 69.999A as a minimum...and
you can use larger wire if you wish.
3. You pick your fuse to protect your wire and blow if too
much current is flowing either into or out of the
alternator lead. (Shorts can happen anywhere) But,
you can always choose to put a smaller fuse in, if
all the rest is kept in spec. You may be wasting
the possible capacity (i.e. you're paying for a 70A
alternator but you're giving up some capacity if you
plan it as a 60A system) but there is nothing wrong
with looking at your loads and putting a safe undersized
fuse in there.
You may not KNOW what your actual common max operating draw will
turn out to be, to within an amp or two, until you first fly, but
at that point, if you want to protect against drawing far in
excess of what is required, you can put in an appropriately
sized fuse.
In my case, I have a 70A alternator, chosen for it's lower turning
speed, and cooler operation, and plenty of capacity beyond my
requirements. I sized the wire to handle 70A from the alternator,
and used #2 back to the battery from the solenoid. Then, I stuck
in a 60A fuse. After running the plane, I find that my norm is
to pull maybe 30-36A, and 40-42A with everything on. Yeah,
during a low battery event I may pull a little more for a couple
minutes, tapering off quickly as it charges. But, 60A would be
a huge increase in current, so if I saw 60A, I would start
wondering what the heck was going wrong. Add in the slow blow
time to blow that 60A ANL, and the fact that it can handle
surges beyond 60A for a period of time, and there's no reason for
me to put greater than a 60A fuse in there. I could even go
with less if I wanted. In 320+ hours, I haven't had a nuisance
trip of any fuse or breaker in the plane, except for my HID's
initially....because you need to size the fuse on those to handle
the startup inrush current that tapers off.
So you're right, you want to protect the wire, but you can
always undersize your fuse to a reasonable point that it would
blow if you had a current draw that was indicative of a
serious issue. You could wire your LED lights with 12GA if
you really wanted to....but you still would want a small fuse
on them, because if your LED's are drawing 10A, something
is wrong.
Tim Olson - RV-10 N104CD - Flying
do not archive
linn Walters wrote:
| Quote: |
Tim Olson wrote:
>
>
> That's exactly my reasoning on using a 60A fuse (despite my 70A
> alternator). The fact is, if I find myself drawing 60A off
> my alternator, something is not right at all. None of my
> avionics or equipment can draw that much, so my battery or
> wires are shorted or something. You don't size your fuse by
> the alternator, you size it to the max load you care to see
> before you blow.
Not really true. The size of the breaker is there to protect the wire,
which could cause a fire if it gets a large escess of current. The size
of the wire is dictated by the load. True of small wires and big ones too.
Linn
do not archive
> A 60A ANL fuse won't blow until well over
> 60A anyway, so if that baby blows, I sure as heck don't
> want to push a reset button in flight and figure it out.
> That fuse/breaker is a very big problem indicator.
> Tim
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wcurtis(at)nerv10.com
Guest
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| Posted: Fri Feb 01, 2008 8:33 am Post subject: Alternator Circuit Breaker |
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http://tinyurl.com/2ew2k5
http://tinyurl.com/2gwsn6
under $18
The 2202 red unit offers the same 5/16" size stud diameter as the starter and starter contacter. I had bought another one that was a bit smaller however it had 3/8" stud size. I wanted to keep the terminal stud sizes consistent.
William
http://wcurtis.nerv10.com/
------
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planesmith(at)hotmail.com
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| Posted: Fri Feb 01, 2008 11:53 am Post subject: Alternator Circuit Breaker |
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B&C Specialty Products is one source. See link below.
http://www.bandc.biz/cgi-bin/ez-catalog/cat_display.cgi?7X358218#c905-100
Vern Smith (#324 windows)
do not archive
> Subject: Re: Alternator Circuit Breaker
Climb to the top of the charts! Play the word scramble challenge with star power. Play now! [quote][b]
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orchidman
Joined: 10 Jul 2006
Posts: 277
Location: Oklahoma City - KRCE
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| Posted: Fri Feb 01, 2008 12:25 pm Post subject: Re: Alternator Circuit Breaker |
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Vern and all,
Thanks,
I found a source from Tim's post from AeroElectric. Googling the base # I found www.drillspot.com. They have the base and a 50 amp fuse.
Your link to www.bandc.biz has a better price by a couple dollars but they don't stock the 50 amp. So more thinking will be in order.
Williams link to fisheriessupply.com is a great link to the Feed Through Terminals.
Now I will start looking for the Shotkey diodes. A quick look at the BandC site looks like they have a 15 amp-25 amp max version for $7 or $18 with a heat sink.
With all of your help, it looks like I am starting to nail down the various small items that complete the wiring diagrams.
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_________________
Gary Blankenbiller
RV10 - # 40674
(N2GB Flying) |
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Tim Olson
Joined: 25 Jan 2007
Posts: 2879
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| Posted: Fri Feb 01, 2008 1:06 pm Post subject: Alternator Circuit Breaker |
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I do like the schottky diodes for going to an aux. Mainly because
the voltage drop is smaller than the other standard diodes, and
you'll never get a full charge on a battery if you're constantly
feeding it .7V less than optimal. The schottky for me was a
little harder to mount, but it was worth it for what it offers.
The reason it was tougher was that the base is one of the
contact surfaces, hence you need to insulate it from the airframe.
Tim Olson - RV-10 N104CD - Flying
do not archive
orchidman wrote:
| Quote: |
planesmith(at)hotmail.com wrote:
> B&C Specialty Products is one source. See link below.
>
> http://www.bandc.biz/cgi-bin/ez-catalog/cat_display.cgi?7X358218#c905-100 (http://www.bandc.biz/cgi-bin/ez-catalog/cat_display.cgi?7X358218#c905-100)
>
> Vern Smith (#324 windows)
>
Vern and all,
Thanks,
I found a source from Tim's post from AeroElectric. Googling the base # I found www.drillspot.com. They have the base and a 50 amp fuse.
Your link to www.bandc.biz has a better price by a couple dollars but they don't stock the 50 amp. So more thinking will be in order.
Williams link to fisheriessupply.com is a great link to the Feed Through Terminals.
Now I will start looking for the Shotkey diodes. A quick look at the BandC site looks like they have a 15 amp-25 amp max version for $7 or $18 with a heat sink.
With all of your help, it looks like I am starting to nail down the various small items that complete the wiring diagrams.
--------
Gary Blankenbiller
RV10 - # 40674
Fuselage SB
(N410GB reserved)
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=161915#161915
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planesmith(at)hotmail.com
Guest
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| Posted: Fri Feb 01, 2008 2:25 pm Post subject: Alternator Circuit Breaker |
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I think Tim hit the nail on the head. One possible source is:
http://www.periheliondesign.com/ (then click on the power schottky link)
They also offer a heat sink and insulator.
Vern (#324 windows)
do not archive
> Date: Fri, 1 Feb 2008 14:59:20 -0600
| Quote: | From: Tim(at)MyRV10.com
To: rv10-list(at)matronics.com
Subject: Re: Re: Alternator Circuit Breaker
--> RV10-List message posted by: Tim Olson <Tim(at)MyRV10.com>
I do like the schottky diodes for going to an aux. Mainly because
the voltage drop is smaller than the other standard diodes, and
you'll never get a full charge on a battery if you're constantly
feeding it .7V less than optimal. The schottky for me was a
little harder to mount, but it was worth it for what it offers.
The reason it was tougher was that the base is one of the
contact surfaces, hence you need to insulate it from the airframe.
Tim Olson - RV-10 N104CD - Flying
do not archive
orchidman wrote:
> --> RV10-List message posted by: "orchidman" <gary(at)wingscc.com>
>
>
> planesmith(at)hotmail.com wrote:
>> B&C Specialty Products is one source. See link below.
>>
>> http://www.bandc.biz/cgi-bin/ez-catalog/cat_display.cgi?7X358218#c905-100 (http://www.bandc.biz/cgi-bin/ez-catalog/cat_display.cgi?7X358218#c905-100)
>>
>> Vern Smith (#324 windows)
>>
>
> Vern and all,
> Thanks,
> I found a source from Tim's post from AeroElectric. Googling the base # I found www.drillspot.com. They have the base and a 50 amp fuse.
> Your link to www.bandc.biz has a better price by a couple dollars but they don't stock the 50 amp. So more thinking will be in order.
>
> Williams link to fisheriessupply.com is a great link to the Feed Through Terminals.
>
> Now I will start looking for the Shotkey diodes. A quick look at the BandC site looks like they have a 15 amp-25 amp max version for $7 or $18 with a heat sink.
> With all of your help, it looks like I am starting to nail down the various small items that complete the wiring diagrams.
>
> --------
> Gary Blankenbiller
> RV10 - # 40674
> Fuselage SB
> (N410GB reserved)
>
>
>
>
> Read this topic online here:
>
> http://forums.matronics.com/viewtopic.php?p=161915#161915
>
>
>
>
>
>
>
> >
|
Need to know the score, the latest news, or you need your Hotmail®-get your "fix". Check it out. [quote][b]
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wcurtis(at)nerv10.com
Guest
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| Posted: Fri Feb 01, 2008 2:37 pm Post subject: Alternator Circuit Breaker |
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| Quote: | Now I will start looking for the Shotkey diodes. A quick look at the BandC site looks like they have a 15 amp-25 amp max version for $7 or $18 with a heat sink.
With all of your help, it looks like I am starting to nail down the various small items that complete the wiring diagrams.
|
The B&C diode is not a schottky diode but a bridge rectifier and has a rather large forward voltage of about 1 volt. A true schottky diode will have a max forward voltage drop of about .5 volts, but as low as .1 volts.
Here is a 60A Schottky for $30.
http://www.periheliondesign.com/powerschottkydiodes.htm
Radio shack 25A rectifier $3.29
<http://www.radioshack.com/product/index.jsp?productId 62584&cp=&pg=1&sr=1&origkw=diode&kw=diode&parentPage=search>
Some more Schottky
http://ixdev.ixys.com/DataSheet/L227.pdf
William
http://wcurtis.nerv10.com/
"Be who you are and say what you feel because those who mind don't matter and those who matter don't mind."
-- Dr. Suess
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carl.froehlich(at)cox.net
Guest
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| Posted: Fri Feb 01, 2008 4:53 pm Post subject: Alternator Circuit Breaker |
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William,
Some thoughts on your question:
| Quote: | I have a dual battery install with separate right/left busses that support
continued IFR flight without the alternator.
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Continued IFR without an alternator-- How is that possible? OK, maybe
possible, but prudent?
No, not prudent just as it is not prudent to fly on a single ignition. The
capability to do so however is desirable.
For my RV-8A install, the design criteria was continued IFR flight for three
hours with a failed alternator. The POH procedure however for an alternator
failure is to land as soon as it is safe to do so. Keep in mind while the
panel is fully up, including continuous transponder use and radios,
unnecessary loads are shed by opening both battery master relays (the relays
themselves being significant and unnecessary loads). Non-vital loads can be
restored anytime by shutting a master relay. Here is a link to Tim's web
page that has an old version of this power distribution system.
http://myrv10.com/tips/electrical.html
I have since updated this design as there are better components on the
market. The concept however remains the same, protect the most reliable
energy source (batteries), assume there will be a failure and allow the
system to degrade gracefully, not catastrophically, and do not have a single
point failure lead to total power loss. The most failure prone component is
the alternator. This is one of the reasons why I went with two equal sized
batteries and a single alternator.
You'll note that the electronic ignitions have no alternate power source,
just the battery they are wired to. For the LightSpeed EIs, operation on
single ignition is not discernible from dual operation. Note also however,
the direct connection of each ignition to each battery. This is done to
eliminate other electrical bus failure modes taking out that side's
ignition.
As you say, there are a lot of good designs that offer better electrical
power reliably than that of traditional certified aircraft. This is just
one attempt.
Carl
--
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hotwheels
Joined: 01 Jun 2007
Posts: 240
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| Posted: Sat Feb 02, 2008 8:52 pm Post subject: Alternator Circuit Breaker |
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MIDI fuses available from Mouser.com
576-04980900Z Fuse Holder
576-0498080.M
80A Fuse
Data Sheet Here...
http://www.littelfuse.com/data/en/Data_Sheets/498.pdf
Looking for last minute shopping deals?
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orchidman
Joined: 10 Jul 2006
Posts: 277
Location: Oklahoma City - KRCE
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