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1. 10:08 AM - Re: Fuse-able link (John Morgensen)
2. 11:33 AM - Re: Fuse-able link (Charlie England)
3. 07:03 PM - Re: Fuse-able link (user9253)
Message 1
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Subject: | Re: Fuse-able link |
Bob,
I sent you the old parts minus the "sleeve" and I fabricated a new
fuse-link that worked for about 2 flight hours with a new Plane Power
60amp alternator. It failed and when I pulled on the wire, it separated
in the middle of the fuse link 22ga. A picture is attached.
The old Plane Power Alternator was retained as a working spare.
I don't know what to do next. It is not popping the 5amp circuit breaker
but it is "frying" the 22ga wire.
600 hours on the plane. Originally, a PC680 battery replaced with an
EarthX900 two years ago. Plane Power 60amp internally regulated with
built in crowbar.
Z-13/8 architecture and the wire that is failing is from the "Main Power
Distribution Bus" bolt to pin 5 on the S700-2-10 switch.
At this point, I don't understand what is purpose the fuse-link and why
it has started failing.
Thanks for any help,
John Morgensen
On 12/20/2018 2:14 PM, Robert L. Nuckolls, III wrote:
> At 01:23 PM 12/20/2018, you wrote:
>> <john@morgensen.com>
>>
>> Two years ago I had an over-voltage event and the crowbar protection
>> behaved as expected. It popped the 5amp breaker. I had the alternator
>> (Plane Power 60amp internal) repaired and it has behaved normally
>> since then. The alternator stopped working this Sunday. The crimp had
>> failed on the 18ga to 22ga fuse-link. Closer inspection revealed that
>> the insulation under the heat shield on the fuse-link was almost
>> completely gone.
>>
>> Questions:
>>
>> 1. Should I have inspected the fuse-link after the over-voltage
>> incident before putting the plane back in service?
>>
>> 2. Is it acceptable to solder the joint between the 18ga and the 22ga
>> or is a crimp connector required?
>
> I would really like to have that fusible link
> assembly. Can you cut it out and fabricate
> a new one?
>
> When you say "gone" . . . is it melted, charred,
> evaporated? Was it Tefzel wire?
>
> That link normally carries 3A or less. I've
> demonstrated that 22AWG Tefzel will carry
> 20A indefinitely in the open air.
>
> Some combination of factors stacked up to
> cause this particular link to suffer
> damage. A good place to start is careful
> examination of the link.
>
>
> Bob . . .
>
Message 2
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Subject: | Re: Fuse-able link |
On 12/29/2018 12:06 PM, John Morgensen wrote:
>
> Bob,
>
> I sent you the old parts minus the "sleeve" and I fabricated a new
> fuse-link that worked for about 2 flight hours with a new Plane Power
> 60amp alternator. It failed and when I pulled on the wire, it
> separated in the middle of the fuse link 22ga. A picture is attached.
>
> The old Plane Power Alternator was retained as a working spare.
>
> I don't know what to do next. It is not popping the 5amp circuit
> breaker but it is "frying" the 22ga wire.
>
> 600 hours on the plane. Originally, a PC680 battery replaced with an
> EarthX900 two years ago. Plane Power 60amp internally regulated with
> built in crowbar.
>
> Z-13/8 architecture and the wire that is failing is from the "Main
> Power Distribution Bus" bolt to pin 5 on the S700-2-10 switch.
>
> At this point, I don't understand what is purpose the fuse-link and
> why it has started failing.
>
> Thanks for any help,
>
> John Morgensen
>
> On 12/20/2018 2:14 PM, Robert L. Nuckolls, III wrote:
>> At 01:23 PM 12/20/2018, you wrote:
>>> <john@morgensen.com>
>>>
>>> Two years ago I had an over-voltage event and the crowbar protection
>>> behaved as expected. It popped the 5amp breaker. I had the
>>> alternator (Plane Power 60amp internal) repaired and it has behaved
>>> normally since then. The alternator stopped working this Sunday. The
>>> crimp had failed on the 18ga to 22ga fuse-link. Closer inspection
>>> revealed that the insulation under the heat shield on the fuse-link
>>> was almost completely gone.
>>>
>>> Questions:
>>>
>>> 1. Should I have inspected the fuse-link after the over-voltage
>>> incident before putting the plane back in service?
>>>
>>> 2. Is it acceptable to solder the joint between the 18ga and the
>>> 22ga or is a crimp connector required?
>>
>> I would really like to have that fusible link
>> assembly. Can you cut it out and fabricate
>> a new one?
>>
>> When you say "gone" . . . is it melted, charred,
>> evaporated? Was it Tefzel wire?
>>
>> That link normally carries 3A or less. I've
>> demonstrated that 22AWG Tefzel will carry
>> 20A indefinitely in the open air.
>>
>> Some combination of factors stacked up to
>> cause this particular link to suffer
>> damage. A good place to start is careful
>> examination of the link.
>>
>>
>> Bob . . .
>>
John,
When you said, ' "Main Power Distribution Bus" bolt to pin 5 on the
S700-2-10 switch', did you mean literally, or was that just shorthand
for fuselink>18ga>breaker>20ga>pin5 ?
Are you absolutely certain that your wiring is an *exact* match for
what's shown in Z-13/8?
Any chance your OV crowbar got tied to the supply side of the CB,
instead of the load side?
Are you absolutely sure that nothing whatsoever got tied to that feed,
somewhere ahead of the CB?
Just spit balling here, but:
22ga wire will carry quite a bit more current than 5A without even
damaging the insulation, much less the wire. Burning it twice implies
either a much higher load on that wire, or (more likely) a dead short to
ground prior to the CB (if the CB is in the circuit). The crowbar
circuit could likely survive long enough to fry the wire without
damaging the crowbar. If that's happening, that implies either the
crowbar is misadjusted, or it's setpoint is drifting, or you're having
actual overvoltage events. Do you have data logging of your instruments?
Can you check the log for voltage levels over time?
Charlie
(BTW, top-posting after a bottom-posted reply makes for really hard reading)
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Message 3
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Subject: | Re: Fuse-able link |
That wire did not burn open from an overload. There was a dead short to
ground. Either a wire is shorted to ground or else the Over Voltage Module is
tripping (shorting to ground). And that short circuit is upstream from the circuit
breaker. In other words, something is wired incorrectly. Or else the circuit
breaker is defective.
If the wire is connected from the main power bus to pin 5 on the switch, then
it is NOT wired according to Z-13/8. The circuit breaker needs to be between
the fuselink and the over-voltage module.
--------
Joe Gores
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=486603#486603
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