Today's Message Index:
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1. 04:38 AM - Re: Alternator, battery and bus question (Charles Kuss)
2. 04:44 AM - Re: Alternator, battery and bus question (Charles Kuss)
3. 10:53 AM - Re: High intensity LEDs (markfw)
4. 03:04 PM - Re: Alternator, battery and bus question (nuckollsr)
5. 03:14 PM - Re: Always hot power for fuel injectors and ignition coils (cofford)
6. 03:20 PM - Re: Always hot power for fuel injectors and ignition coils (cofford)
7. 03:23 PM - Re: Alternator, battery and bus question (nuckollsr)
8. 03:47 PM - Re: Re: Always hot power for fuel injectors and ignition coils (Charlie England)
9. 06:56 PM - Re: Always hot power for fuel injectors and ignition coils (cofford)
10. 07:34 PM - Re: Always hot power for fuel injectors and ignition coils (user9253)
Message 1
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| Subject: | Re: Alternator, battery and bus question |
Excessive output can either immediately or slowly over time, damage or dest
roy one or more of the diodes in the alternators rectifier. The rectifier c
onverts the AC current into the DC current that your aircraft needs. Most a
lternators have six diodes in them. Normal failure mode is for a diode to f
ail open circuit. So for each diode that fails you will lose one sixth of t
he alternators output. More Insidious, is if a diode fails shorted. In that
case there will be no drop-off in the alternators output and an ammeter te
st will not show the failure. The failure will cause AC current to bleed in
to the system. Batteries hate AC current. AC current will destroy a brand n
ew battery in a few months.
Charlie
Sent from Yahoo Mail on Android
On Fri, Feb 14, 2020 at 10:08 PM, Krea Ellis<krea.ellis@gmail.com> wrote:
m>
What happens if an alternator is temporarily overloaded (let=99s say
it=99s rated at 40 amps) and you draw 45 amps. Assume the battery is
well maintained and fully charged. A current limiter (ANL/AML) is installed
as well.
You intend to load shed, but don=99t do so immediately. What are the
consequences?
My assumption is the voltage will drop and the battery will supplement the
alternator for some period of time until you can load shed and then the alt
ernator will carry the entire load? I assume the current limiter will not b
low with a short duration small overload.
Thanks in advance for educating me.
Krea Ellis
=C2- =C2- =C2- =C2- =C2- -Matt Dralle, List Admin.
-
S -
WIKI -
-
=C2- =C2- =C2- =C2- =C2- -Matt Dralle, List Admin.
Message 2
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| Subject: | Re: Alternator, battery and bus question |
The situation described in my last post is not likely to happen on an aircr
aft that has a fully charged battery. The most common way that rectifier di
odes get damaged is by jump starting a vehicle that has a dead battery. The
alternator is then forced to generate current at maximum output for an ext
ended length of time to refill the battery. That could cause the diodes to
overheat and fail. So the lesson is if you have a dead battery don't just j
ump start it. Recharge the battery before you start the engine.
Charlie
Sent from Yahoo Mail on Android
On Fri, Feb 14, 2020 at 10:08 PM, Krea Ellis<krea.ellis@gmail.com> wrote:
m>
What happens if an alternator is temporarily overloaded (let=99s say
it=99s rated at 40 amps) and you draw 45 amps. Assume the battery is
well maintained and fully charged. A current limiter (ANL/AML) is installed
as well.
You intend to load shed, but don=99t do so immediately. What are the
consequences?
My assumption is the voltage will drop and the battery will supplement the
alternator for some period of time until you can load shed and then the alt
ernator will carry the entire load? I assume the current limiter will not b
low with a short duration small overload.
Thanks in advance for educating me.
Krea Ellis
=C2- =C2- =C2- =C2- =C2- -Matt Dralle, List Admin.
-
S -
WIKI -
-
=C2- =C2- =C2- =C2- =C2- -Matt Dralle, List Admin.
Message 3
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| Subject: | Re: High intensity LEDs |
Bob,
If you have any more of the high intensity LED's I could use two of them in RED.
Please send them to:
Mark Wheeler
1009 Western Ave #1207
Seattle, WA 98104
I have asked once before but you may not have seen it. If so, please ignore this
message.
Thank you!
Mark
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http://forums.matronics.com/viewtopic.php?p=494816#494816
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| Subject: | Re: Alternator, battery and bus question |
> What happens if an alternator is temporarily overloaded (lets say its rated at
40 amps) and you draw 45 amps. Assume the battery is well maintained and fully
charged. A current limiter (ANL/AML) is installed as well.
An alternator is inherently overload-proof. The magnetics
prevent output at more than a few percent above nameplate
rating. This is temperature dependent. We have discussed
instances here on the list where a cold alternator attempting
to stuff electrons into a badly discharged batter will trip the
b-lead breaker on some single engine aircraft. This is rare
but not unheard-off . . . happened to me once and the ensuing
load-dump killed the regulator. Flew the whole drip in the
dark-panel mode.
A current limiter is exceedingly robust . . . they will carry
50 to 100 percent of rating indefinitely. This is why they
are used as DISTRIBUTION protection and have replaced the
legacy 60A breaker that was common on most single engine
aircraft with 60A alternators.
Assuming one has installed PROPER b-lead protection in
the way of a current limiter, then all is well on the alternator
side of the equation. An alternator cannot open it's own
properly designed b-lead protection except in the case of
BADLY damaged (shorted) rectifiers. Haven't seen a case
of that since . . . oh . . . about 1975 on some Chrysler products.
> You intend to load shed, but dont do so immediately. What are the consequences?
The alternator will put out it's rated current indefinitely with no
potential for hazard to any equipment in the airplane. It essentially
becomes a constant current/constant voltage power supply
operating in the constant current mode until demands are
reduced whereupon bus voltage will rise to the regulation
set-point and normal operations resume.
>
> My assumption is the voltage will drop and the battery will supplement the alternator
for some period of time until you can load shed and then the alternator
will carry the entire load? I assume the current limiter will not blow with
a short duration small overload.
Correct.
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=494819#494819
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| Subject: | Re: Always hot power for fuel injectors and ignition |
coils
They system is FlyEFII System32. The manufacturer recommends using their own bus
manager system, which provides a diode-protected, arguably dual-feed switched
bus (the terminal on the bus manager is dual-fed, but the engine components
are all fed by a single wire). I'm sure the manufacturer's recommendations are
fine in most cases. That being said, I'm an engineer in the manned spaceflight
industry, and I don't like black boxes and easily avoidable single-point
failures.
The aircraft currently has no electrical system as I'm about to begin installing
one. I've been considering both Z12 and Z19 architectures without an endurance
bus.
Thanks,
Casey
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Message 6
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| Subject: | Re: Always hot power for fuel injectors and ignition |
coils
Thanks Charlie, agree with your reasoning and I am heading towards a similar solution,
though perhaps with a relay at the battery instead of a high-current switch.
Just wanted to make sure that I wasn't missing something.
Thanks,
Casey
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=494821#494821
Message 7
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| Subject: | Re: Alternator, battery and bus question |
[quote]The situation described in my last post is not likely to happen on an aircraft
that has a fully charged battery. The most common way that rectifier diodes
get damaged is by jump starting a vehicle that has a dead battery. The alternator
is then forced to generate current at maximum output for an extended
length of time to refill the battery. That could cause the diodes to overheat
and fail. So the lesson is if you have a dead battery don't just jump start it.
Recharge the battery before you start the engine. [quote]
The legacy prohibition for doing a ground power start on a aircraft
with a dead battery has more to do with risks to the battery than
to the alternators/generators.
Suppose you've got a PC680 or smaller battery on an airplane fitted
with a 60A or larger alternator. That little hunk of plastic enclosed lead
will quite willingly accept what ever the alternator offers. If bus loads are
low, then you're going to be pounding the little feller pretty hard.
Similarly, biz-jets might have a 40 a.h. battery charged by a PAIR of
300 or 400 amp starter generators. Same problem in spades.
There is little risk for jump starting most light aircraft 'cause you can't
get full output from the alternator at taxi rpms . . . so by the time you're
out at the runway ready to take off, recharge current has dropped off
substantially . . . but the risks are not zero. If you've got instrumentation
to manage battery recharge rates it's no big deal. But try to add 3 or 4
paragraphs on this topic to the pilot's handbook on a TC GA aircraft and
you'll have the sales wienies all over you.
We used to have some nice fat loads (landing lights and pitot heaters)
that would help manage recharge rates on SE aircraft. Those assets
are going away. Know what needs to be done and make sure you
CAN do it.
Solution is a placard: "Charging a dead battery with ships generators
is not recommended (or prohibited)." Risk goes away along with any
need to further educate a pilot. Best thing to do is recharge the battery
before spooling up for departure but there are alternatives for the astute
owner/operator.
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=494822#494822
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| Subject: | Re: Always hot power for fuel injectors and ignition |
coils
On Sat, Feb 15, 2020 at 5:25 PM cofford <cofford@gmail.com> wrote:
>
> Thanks Charlie, agree with your reasoning and I am heading towards a
> similar solution, though perhaps with a relay at the battery instead of a
> high-current switch. Just wanted to make sure that I wasn't missing
> something.
>
> Thanks,
> Casey
I considered another relay, but decided to use the switch since I found one
with the current capability, and it eliminated a set of contacts (control
for the relay), a coil, and multiple termination points connecting the
control to the relay. Given the redundant feeds, probably not worth
worrying about.
Charlie
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| Subject: | Re: Always hot power for fuel injectors and ignition |
coils
I had a chance to draw up some schematics. This is the dual battery system I've
been kicking around for a while.
https://drive.google.com/open?id=1vKln4Zl0CC24Si8QUW78MCfymVRQejvZ
As I've given this more thought, a Z12 architecture with one battery makes quite
a bit of sense. In that case, the schematic looks like this:
https://drive.google.com/open?id=1Q32syGUfgtm7dR-bksQex80r2olKD_Al
Goals here were:
1. Any single component failure does not result in loss of power to the engine
bus.
2. Any single failure does not require pilot action to keep power to the engine
bus.
3. Any redundancy must have the ability to be checked during preflight.
Comments are most welcome.
Thanks!!!
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http://forums.matronics.com/viewtopic.php?p=494826#494826
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| Subject: | Re: Always hot power for fuel injectors and ignition |
coils
On the single battery system:
If the EFIS has two voltmeter inputs, connect one to the main bus and one to
the engine bus. Switching the aux power relay on and off while comparing
the two voltmeters will confirm that the aux power relay is working.
--------
Joe Gores
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