Today's Message Index:
----------------------
1. 12:34 AM - Re: Z-* Question (jonlaury)
2. 05:20 AM - Re: Making your own fuseable links (JOHN TIPTON)
3. 06:50 AM - Re: Re: Making your own fuseable links (Robert L. Nuckolls, III)
4. 01:33 PM - Re: Re: Making your own fuseable links (Robert L. Nuckolls, III)
Message 1
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| Subject: | Re: Z-* Question |
barber_seville(at)msn.com wrote:
> Charles Boyer and ?
>
>
Ingrid Bergman
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=481626#481626
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| Subject: | Re: Making your own fuseable links |
Hi Bob
I can see where we are now with Z11 rev: P (thank you user9253-Joe Gores for the
link), I'm sticking with Rev: M (no 30 amp in-line fuse or or E-Bus alternate
feed relay) - so it's a fusible link off the live side of the Battery contactor
Regards: John
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=481630#481630
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| Subject: | Re: Making your own fuseable links |
At 07:19 AM 7/13/2018, you wrote:
><jmtipton@btopenworld.com>
>
>Hi Bob
>
>I can see where we are now with Z11 rev: P (thank you user9253-Joe
>Gores for the link), I'm sticking with Rev: M (no 30 amp in-line
>fuse or or E-Bus alternate feed relay) - so it's a fusible link off
>the live side of the Battery contactor
>
>Regards: John
>
>
Wouldn't do that myself but as you wish . . .
Bob . . .
Message 4
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| Subject: | Re: Making your own fuseable links |
>
> Wouldn't do that myself but as you wish . . .
Got a private email seeking clarification of what
was correctly perceived as a terse reply. My
apologies.
Recall that the legacy 'rule of thumb' for always
hot feeders in TC aircraft suggested they
be protected at not more than 5A. This HAD to
be a rule of thumb . . . cause the 5A figure
was a constant whether we were talking about
28 vs. 14v and breakers vs. fuses.
I've asked if analysis was offered for mitigating
potential energy dissipation that drove
the 5A figure . . . nobody I knew was aware of
any such study.
Nonetheless, FMEA deliberations confirmed the
notion that such wires SHOULD be of some limited
ability to conduct post-crash energy.
So for the Z-figures, we adopted 7A in fuses
and 5A in breakers in 14v systems.
The 7A fuse seemed to give good coverage for
most boost pumps and electronic ignition systems
of the time. A little later on, the Endurance
Bus came along. At that time, it was possible
to craft an endurance load that did not exceed
the 7A-rule for always hot feeders.
At some later time, Z-13/8 came along which offered
an opportunity to support e-bus/battery bus loads
up to and including 10A. We also had builders
wanting to support e-bus loads in excess of 10A.
At this time, the e-bus alternate feed relay was
added to become a mini-battery contactor that supported
only e-bus loads. At that time, protection of that
feed path was boosted to 15A . . . and COULD be
larger still.
This because crash safety for the feed path
changed from ALWAYS HOT protected at 7A to
CREW CONTROLLED with no practical limit.
Emacs!
If one does not require a battery bus
but with 'larger' e-bus loads, then the alternate
feed relay is still recommended. The relay
is mounted close to the battery contactor
hence a short jumper between the two devices.
That jumper is easily fabricated with an
in-line fuse holder. the in-line fuse is MANY
times faster than a fusible link.
As we've discussed quite a few times over the
years, fusible links behave more like current
limiters . . . very slow compared to fuses.
They are not recommended for in situations
other than those illustrated in the Z-figures.
Bob . . .
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