Today's Message Index:
----------------------
1. 11:08 AM - Test; List Server Issues... (Matt Dralle)
2. 06:00 PM - Re: OV protection circuit design (Pat Little)
3. 06:27 PM - Re: Re: OV protection circuit design (Charlie England)
4. 06:41 PM - Re: Re: OV protection circuit design (Robert L. Nuckolls, III)
5. 06:42 PM - Re: Re: OV protection circuit design (Robert L. Nuckolls, III)
6. 07:53 PM - Re: Re: OV protection circuit design (Pat Little)
7. 08:05 PM - Battery discharge during normal cruise (Paul Zimmer)
Message 1
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| Subject: | Test; List Server Issues... |
The Matronics Email List Server was having some issues and not accepting incoming
posts for a couple of days. I think I have it resolved now.
Sorry for the hassle.
Matt Dralle
Matt G Dralle | Matronics | 581 Jeannie Way | Livermore | CA | 94550
925-606-1001 V | 925-606-6281 F | dralle@matronics.com Email
http://www.matronics.com/ WWW | Featuring Products For Aircraft
Message 2
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| Subject: | Re: OV protection circuit design |
On Thu, Feb 27, 2020 at 10:05 AM user9253 <fransew@gmail.com> wrote:
>
> I suggest buying a fuse block that holds 15 or 20 fuses. A builder once
> said
> to install a fuse block that holds twice as many fuses as you anticipate
> needing, because you will need them. Every single load, no matter how
> small, should have its own unique fuse.
> Then replace the fuse-links with 30 amp fuses. Doing that will simplify
> the
> wiring. Looking at Z-20, I suspect the intent was two different wire
> sizes, with
> one a typo. If a 30 amp fuse is used instead of a fuse-link, then I would
> use 22
> AWG for all wires in the field circuit. 22 AWG is good for 7 amps. It
> takes 40
> amps to melt 22 wire.
> Charlie, the alternator B lead is separate and not shown on the diagram.
>
> --------
> Joe Gores
>
I like the simplification of using fuses instead of fuselinks (my design
has 22 fuses so far, another two won't be a problem). And I can appreciate
that if an OV occurs, and the CB trips, the fuse needs to be big enough to
not also blow and deny the pilot the chance to re-engage the breaker and
see if the OV condition repeats itself or not.
But why 30A? That seems very large as compared to a 5A CB.
And a separate thought - if the fuse is significantly bigger, and its sole
purpose is to protect the wire between the bus and the CB (am I
interpreting this correctly?), then that segment of wire would need to be a
lot bigger for the fuse to actually protect it. AC 43.13-1B says a 30A fuse
is needed to protect a 10AWG wire - is this a valid reason for having
differing wire sizes in different parts of the circuit?
Pat
Message 3
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| Subject: | Re: OV protection circuit design |
On 3/3/2020 7:55 PM, Pat Little wrote:
> On Thu, Feb 27, 2020 at 10:05 AM user9253 <fransew@gmail.com
> <mailto:fransew@gmail.com>> wrote:
>
> <fransew@gmail.com <mailto:fransew@gmail.com>>
>
> I suggest buying a fuse block that holds 15 or 20 fuses. A
> builder once said
> to install a fuse block that holds twice as many fuses as you
> anticipate
> needing, because you will need them. Every single load, no matter how
> small, should have its own unique fuse.
> Then replace the fuse-links with 30 amp fuses. Doing that will
> simplify the
> wiring. Looking at Z-20, I suspect the intent was two different
> wire sizes, with
> one a typo. If a 30 amp fuse is used instead of a fuse-link, then
> I would use 22
> AWG for all wires in the field circuit. 22 AWG is good for 7
> amps. It takes 40
> amps to melt 22 wire.
> Charlie, the alternator B lead is separate and not shown on the
> diagram.
>
> --------
> Joe Gores
>
>
> I like the simplification of using fuses instead of fuselinks (my
> design has 22 fuses so far, another two won't be a problem). And I can
> appreciate that if an OV occurs, and the CB trips, the fuse needs to
> be big enough to not also blow and deny the pilot the chance to
> re-engage the breaker and see if the OV condition repeats itself or not.
>
> But why 30A? That seems very large as compared to a 5A CB.
>
> And a separate thought - if the fuse is significantly bigger, and its
> sole purpose is to protect the wire between the bus and the CB (am I
> interpreting this correctly?), then that segment of wire would need to
> be a lot bigger for the fuse to actually protect it. AC 43.13-1B says
> a 30A fuse is needed to protect a 10AWG wire - is this a valid reason
> for having differing wire sizes in different parts of the circuit?
>
> Pat
My take is a bit different. I really like fusible links for wires that
have near zero risk of failure, short (pardon the pun) of a catastrophic
fault. A bit of extra work, once. Then it's more compact (it's just part
of the wire run, instead of needing another fuse slot), and no risk
whatsoever of extra joints, fatigue failure of the link inside an actual
fuse, etc.
Not saying either approach is 'right'; I just prefer mine.
Charlie
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Message 4
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| Subject: | Re: OV protection circuit design |
>
>I like the simplification of using fuses instead
>of fuselinks (my design has 22 fuses so far,
>another two won't be a problem). And I can
>appreciate that if an OV occurs, and the CB
>trips, the fuse needs to be big enough to not
>also blow and deny the pilot the chance to
>re-engage the breaker and see if the OV condition repeats itself or not.
>
>But why 30A? That seems very large as compared to a 5A CB.=C2
The I(square)t operating constant for fuses
and breakers of the same RATING are wildly
different. Further, the ATC30 fuse is not
designed to be used as a LIMITER. Hence,
what seems to be overkill is really rather
rational. I've crowbared some 5A breakers that
would trip an upstream ATC20 fuse.
>And a separate thought - if the fuse is
>significantly bigger, and its sole purpose is to
>protect the wire between the bus and the CB (am
>I interpreting this correctly?), then that
>segment of wire would need to be a lot bigger
>for the fuse to actually protect it. AC 43.13-1B
>says a 30A fuse is needed to protect a 10AWG
>wire - is this a valid reason for having
>differing wire sizes in different parts of the circuit?
No, we're emulating a LIMITER . . . i.e. mitigation
of a hard fault on the order of hundreds of amps.
Same thing that a fusible link does. Just as
a 22AWG wire has been DEMONSTRATED to carry
20A continuously without damage, so too will
the 14AWG wire gamely step up to continuous
loads of 40A or more.
However, the thing we're holding at bay is
the hard fault that would open the 30A
fuse even if the protected feeder were
a 22AWG wire. In this case our EXPECTED
hard fault is the triggering of a crowbar
SCR which generates a predictable
fault current in excess of 100A.
AC43-13 is a compilation of rules-of-thumb;
it's not a properties of materials nor
engineering text. It doesn't apply here.
Bob . . .
Message 5
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| Subject: | Re: OV protection circuit design |
>
>I like the simplification of using fuses instead
>of fuselinks (my design has 22 fuses so far,
>another two won't be a problem). And I can
>appreciate that if an OV occurs, and the CB
>trips, the fuse needs to be big enough to not
>also blow and deny the pilot the chance to
>re-engage the breaker and see if the OV condition repeats itself or not.
>
>But why 30A? That seems very large as compared to a 5A CB.=C2
The I(square)t operating constant for fuses
and breakers of the same RATING are wildly
different. Further, the ATC30 fuse is not
designed to be used as a LIMITER. Hence,
what seems to be overkill is really rather
rational. I've crowbared some 5A breakers that
would trip an upstream ATC20 fuse.
>And a separate thought - if the fuse is
>significantly bigger, and its sole purpose is to
>protect the wire between the bus and the CB (am
>I interpreting this correctly?), then that
>segment of wire would need to be a lot bigger
>for the fuse to actually protect it. AC 43.13-1B
>says a 30A fuse is needed to protect a 10AWG
>wire - is this a valid reason for having
>differing wire sizes in different parts of the circuit?
No, we're emulating a LIMITER . . . i.e. mitigation
of a hard fault on the order of hundreds of amps.
Same thing that a fusible link does. Just as
a 22AWG wire has been DEMONSTRATED to carry
20A continuously without damage, so too will
the 14AWG wire gamely step up to continuous
loads of 40A or more.
However, the thing we're holding at bay is
the hard fault that would open the 30A
fuse even if the protected feeder were
a 22AWG wire. In this case our EXPECTED
hard fault is the triggering of a crowbar
SCR which generates a predictable
fault current in excess of 100A.
AC43-13 is a compilation of rules-of-thumb;
it's not a properties of materials nor
engineering text. It doesn't apply here.
Bob . . .
Message 6
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| Subject: | Re: OV protection circuit design |
On Tue, Mar 3, 2020 at 7:47 PM Robert L. Nuckolls, III <
nuckolls.bob@aeroelectric.com> wrote:
>
> I like the simplification of using fuses instead of fuselinks (my design
> has 22 fuses so far, another two won't be a problem). And I can appreciat
e
> that if an OV occurs, and the CB trips, the fuse needs to be big enough t
o
> not also blow and deny the pilot the chance to re-engage the breaker and
> see if the OV condition repeats itself or not.
>
> But why 30A? That seems very large as compared to a 5A CB.=C3=82
>
>
> The I(square)t operating constant for fuses
> and breakers of the same RATING are wildly
> different. Further, the ATC30 fuse is not
> designed to be used as a LIMITER. Hence,
> what seems to be overkill is really rather
> rational. I've crowbared some 5A breakers that
> would trip an upstream ATC20 fuse.
>
>
> And a separate thought - if the fuse is significantly bigger, and its sol
e
> purpose is to protect the wire between the bus and the CB (am I
> interpreting this correctly?), then that segment of wire would need to be
a
> lot bigger for the fuse to actually protect it. AC 43.13-1B says a 30A fu
se
> is needed to protect a 10AWG wire - is this a valid reason for having
> differing wire sizes in different parts of the circuit?
>
>
> No, we're emulating a LIMITER . . . i.e. mitigation
> of a hard fault on the order of hundreds of amps.
> Same thing that a fusible link does. Just as
> a 22AWG wire has been DEMONSTRATED to carry
> 20A continuously without damage, so too will
> the 14AWG wire gamely step up to continuous
> loads of 40A or more.
>
> However, the thing we're holding at bay is
> the hard fault that would open the 30A
> fuse even if the protected feeder were
> a 22AWG wire. In this case our EXPECTED
> hard fault is the triggering of a crowbar
> SCR which generates a predictable
> fault current in excess of 100A.
>
> AC43-13 is a compilation of rules-of-thumb;
> it's not a properties of materials nor
> engineering text. It doesn't apply here.
>
>
> Bob . . .
>
Thanks for the comments. I have revised my drawing - now it looks a lot
more like Z-12 preliminary rev NP1
[image: alternator circuits revised.png]
Pat
Message 7
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| Subject: | Battery discharge during normal cruise |
Sorry for the following cut and paste of a previous thread. However after
being unable to respond with my follow up post due some unspecified error
on the matronics server, (which I thought was something I was doing wrong),
I have still been unable to add my follow up to the thread. Hopefully by
sending a new email, my follow up will get through.
Paul said:
I use and monitor two Hall effect current sensors on my RV. One measures
the current flow on the "B" lead from the main alternator, and the other
measures the current flow to/from the main battery.
What doesn't make sense to me is there are periodic and frequent current
flows to/from the battery (1 to 5 amps) during normal cruise operations,
this during periods of static and relatively light load (12-15 amps) on the
electrical system, much smaller than the capacity of the 60A Plane Power
alternator. I would expect all power to be supplied directly from the
alternator as it is supplying the current at a higher voltage (~14.5v or
so) than the battery. These periods of flow to/from the battery are short
in duration normally lasting only a few seconds.
Is this normal and to be expected, or does it suggest a problem with the
internally regulated alternator, or perhaps with the current sensor itself?
Any insight explaining what I am seeing will be appreciated.
Thanks
Bob said:
<snip>
These periods of flow to/from the battery are short
in duration normally lasting only a few seconds.
Is this normal and to be expected, or does it
suggest a problem with the internally regulated
alternator, or perhaps with the current sensor itself?
Any insight explaining what I am seeing will be appreciated.
The battery's physics reacts to BUS VOLTAGE.
Any period battery energy outflow MUST be
paired with a drop in bus voltage to something
below the battery's present open-circuit
voltage.
The voltage doesn't have to drop to
the battery's natural delivery
level (~12.5 volts for SVLA) . . .
a battery across an operating bus
will support small outflow currents
at voltages higher than 12.5.
What is your normal bus voltage and do
you notice any depression of voltage
that corresponds to battery outflow
events?
Paul said:
Bob . . .
I can=99t say that I=99ve noticed a bus voltage drop during the
se times of
battery outflow, but before I say one way or the other, I=99ll need t
o pay a
little closer attention, and perhaps record the engine monitor parameters
during a flight which would allow for an after the fact thorough analysis
of what actually went on. I=99ll circle back at a later date. Thank
s
Paul said:
Follow up. I flew for about 30 minutes, during which I recorded the data
collected and reported by my GRT EFIS. The sampling rate is about once per
second. I converted the data to an EXCEL spreadsheet, and the following
are the results.
During normal cruise (following start and battery recharge after start),
the bus voltage varied from ~13.7 to ~14.0V. The current flow to/from the
battery varied both in and out up to a max of 9 amps out all the while
battery voltage remains steady at ~13.9V. During these times of battery
discharge, load was static (which is to say the load was not deliberately
changed). I have a spreadsheet with the data from this flight that was
generated from the EFIS, which I don't think I'm able to attach to this
Email.
Thanks
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