Today's Message Index:
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1. 06:54 AM - Re: Wire selection (Dave Morris \)
2. 08:03 AM - Re: Wire selection (Matt Prather)
3. 11:54 PM - 80 Amp Shunt ()
Message 1
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| Subject: | Re: Wire selection |
--> AeroElectric-List message posted by: "Dave Morris \"BigD\"" <BigD@DaveMorris.com>
I think I detect at least three problems with this logic.
At 10:48 PM 9/20/2005, you wrote:
>--> AeroElectric-List message posted by: Jim Oke <wjoke@shaw.ca>
>Theory is that for equal
>weight of wire, a number of small conductors will have more surface area
>and carry more current than than a single large conductor.
At DC, surface area isn't as important as cross section area.
>The idea is that if a short occurs in the middle of a wire,
>the CB at one end will open normally but current will be fed into the
>other end of the wire via the others in the run and then open the CB at
>the other end isolating the wire. The remaining conductors will still be
>available to power the device or buss but at a reduced capacity.
Once the breaker opens on one end, nothing will flow into the other
end. And what will reduce the capacity?
>So more breakers are needed = higher parts count + more installation
>time & effort + ongoing maintenance. Perhaps worthwhile if you need 200
>amps at a bus but not for a 5-10 amp landing light.
I agree. I think it's way overkill for OBAM. It's the kind of thing you
do in a spacecraft or an aircraft that is going to be shot at and has to
survive no matter the cost.
Dave Morris
Message 2
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| Subject: | Re: Wire selection |
--> AeroElectric-List message posted by: "Matt Prather" <mprather@spro.net>
Hi Dave,
Comments below.
> --> AeroElectric-List message posted by: "Dave Morris \"BigD\""
> <BigD@DaveMorris.com>
>
snip
>>The idea is that if a short occurs in the middle of a wire,
>>the CB at one end will open normally but current will be fed into the
>> other end of the wire via the others in the run and then open the CB at
>> the other end isolating the wire. The remaining conductors will still
>> be available to power the device or buss but at a reduced capacity.
>
> Once the breaker opens on one end, nothing will flow into the other
> end. And what will reduce the capacity?
>
snip
I think the idea is that there's a breaker on each end of each conductor.
The idea is that if a fault develops on only one of the wires in a bundle,
it will be powered from both ends of the bundle... The remaining
conductors aren't faulted. Thus, there will voltage on both ends. That
means that in order for the remaining wires in the bundle to stay hot, the
breaker on each end of the faulted wire will have to open. Does that
clear it up? I agree that this is ridiculous increase in parts count...
>
> Dave Morris
>
Regards,
Matt-
Message 3
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--> AeroElectric-List message posted by: <jlundberg@cox.net>
Does anyone know where to buy a 80amp/50mv shunt for an Electronics International
volt/amp meter. I bought a used digital meter at Oshkosh and it did not have
the shunt. I have found 50 and 75 amp from a marine supply but not the 80
amp version.
Thanks.
John Lundberg
Los Angeles, cA
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