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l.p(at)talk21.com
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 Posted: Fri Jul 04, 2014 8:12 am Post subject: Alternator woes. |
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Bob.
If you could please comment on the following:
Allowing for a 0.7-0.9 volt drop across the diode from main to endurance bus, I am measuring varying voltages on the endurance bus in flight.
What should be 13.5-13.7v to allow for the battery to be charged at 14.4v, I am finding voltages that vary from 12.2v to 13.5v at constant cruise rpm.
Any idea for troubleshooting what is causing the voltage to vary so much?
Checking the voltage on the main bus, but now on the ground, I am seeing voltages that vary with engine rpm, 550 rpm at idle to 2200rpm, of 14.06v to 14.22v respectively.
Is this variance within tolerances of the LR3C regulator? I had expected that the regulator would keep the voltage within a tighter range.
As an aside, I am experiencing a strange anomoly that sometimes when I transmit the transponder turns itself off. Both are Garmin products, GNS530 and GTX330, and are powered from the endurance bus.
Comments invited please.
It is unfortunate that these woes come and go and I'd really like to cure them once and for all.
Aircraft is Long-EZ using an "all electric airplane on a budget" architecture, with all B and C equipment, 60A alternator, SD-8 dynamo and 32AH battery.
Many thanks.
Patrick Elliott.
G-LGEZ
[quote][b]
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user9253
Joined: 28 Mar 2008
Posts: 1920
Location: Riley TWP Michigan
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| Posted: Sat Jul 05, 2014 3:51 pm Post subject: Re: Alternator woes. |
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A loose or corroded connection can produce the symptom that you describe. Check every connection in the alternator field circuit and in the transponder circuit, both negative and positive sides. Any switches or circuit breakers or fuses in the problem circuit are also suspect. Bad connections are easier to find if the circuit is heavily loaded while checking for voltage drops in both negative an positive wires.
Joe
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Joe Gores |
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nuckolls.bob(at)aeroelect
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| Posted: Sun Jul 06, 2014 6:45 am Post subject: Alternator woes. |
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At 11:02 AM 7/4/2014, you wrote:
Bob.
If you could please comment on the following:
Allowing for a 0.7-0.9 volt drop across the diode from main to
endurance bus, I am measuring varying voltages on the endurance bus in flight.
What should be 13.5-13.7v to allow for the battery to be charged at
14.4v, I am finding voltages that vary from 12.2v to 13.5v at
constant cruise rpm.
Any idea for troubleshooting what is causing the voltage to vary so much?
Yes, as Joe has noted, these voltages are consistent
with intermittent alternator function. 13.6 on the
e-bus is consistent with alternator operating, 12.2
says the alternator is inoperative and you're running
battery only.
Checking the voltage on the main bus, but now on the ground, I am
seeing voltages that vary with engine rpm, 550 rpm at idle to
2200rpm, of 14.06v to 14.22v respectively.
Is this variance within tolerances of the LR3C regulator? I had
expected that the regulator would keep the voltage within a tighter range.
Yes, we COULD design for tighter regulation
but there's a risk of unstable operation over
the full constellation of system variables.
a plus or minus variation about the center
of your set-point over variations in load
is expected and acceptable.
As an aside, I am experiencing a strange anomoly that sometimes when
I transmit the transponder turns itself off. Both are Garmin
products, GNS530 and GTX330, and are powered from the endurance bus.
Where is your comm antenna located and what
kind of antenna is it?
Comments invited please.
It is unfortunate that these woes come and go and I'd really like to
cure them once and for all.
Aircraft is Long-EZ using an "all electric airplane on a budget"
architecture, with all B and C equipment, 60A alternator, SD-8 dynamo
and 32AH battery.
Your second problem has the 'smell' of an
RF overload due to strong fields in the
cockpit. This is of particular risk in
a plastic airplane.
Bob . . .
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