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1. 07:20 PM - Re: Anything 'unique' about incorporating EarthX? (blues750)
2. 07:26 PM - Re: Newbie with PM alternator feed question (blues750)
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Subject: | Re: Anything 'unique' about incorporating EarthX? |
[quote="nuckolls.bob(at)aeroelect"]
> With a B&C overvoltage protection module (nominal trip voltage of 16.2 volts),
I could have voltage to the battery greater than the BMS triiger voltage and
have loss of battery power supply at the same time I have no alternator electrical
source!
How so? At what voltage and how fast does the BMS
bring the battery back on line? What leads you
to believe that during the interval from onset of
an ov condition, alternator shut down and BMS
recovery . . . that the bus voltage will drop too
low for too long to keep the fan running?
Bob . . .
> [b]
Bob,
That's part of my dilemma, I cannot answer that question yet. Failure characteristics
with respect to time onset and voltage ouptut during a failure to an overvoltage
output by a generator or regulator of my type I do not know. If I
am recalling correctly, I have read that the B&C OVPM reacts within milliseconds
to an overvoltage issue. The Earthx BMS starts doing it's thing around 15.5
volts - but that is dependent on a few variables. I have asked the engineer
for some time, temp, charge state and charging voltage correlations to try
and determine how quickly the BMS will react and protect the cells and simultaneously
deprive me of needed power to my busses from the battery. Again, it is
my understanding after talking with the engineer at Earthx, that no voltage
is available from the battery (nothing allowed in or out) while the BMS is protecting
the battery I still need to followup with those questions, if they are
indeed the right questions to be asking! (I think so [Rolling Eyes] ) but was
trying to get more insight here first. Based on my understanding at this point,
I am concerned about a scenario in which the output from the alt and R/R
to my battery and busses is somehow slowly rising above 15-16 volts. The BMS
decides to act out and take my batteries offline. I can fly on the alternator
if necessary though maybe not ideal for some equipment or to what value the voltage
may rise. But to get my batteries back, I do need to alleviate the overvoltage
presented to them. Ideally, I would notice the overvoltage prior to the
BMS getting protective, simply shut down the alternator and proceed to the
hangar with my batteries supplying the required voltage as intended. But, having
to take my alternator off-line with my batteries off-line simultaneously does
not seem like proper design if that is indeed a real possibility.
Appreciate the initial feedback and comments, would gladly welcome any more related
to this scenario.
Dave
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=446282#446282
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Subject: | Re: Newbie with PM alternator feed question |
[quote="nuckolls.bob(at)aeroelect"]
>
> (1) Is dynamo current "self limiting" a characteristic of all 3 phase PM type
alternators? (dynamos?) Would gladly eliminate those three 20 amp c/b's if
not required!
the PM alternators will self-destruct if presented
with a hard short on their windings generated by
failure of the rectifier=regulator. Use in-line
fuses. One for the single phase machines, two for
the three phase machines. These need no be crew-
accessible.
Do you mean these "need to be" or "need not be" crew accessible? Why?
or why not?
> (2) Was planning on a 40A ANL type fuse for the 10 ga wire from the relay to
the primary bus.
What is the rated output of your altenrator?
An inline maxi-fuse of next-step higher value
would be fine and a lot less bulky.
30 Amp alternator, and I like the idea of the inline maxi-fuse versus the ANL because
of the reduced size. I thought ANL type was preferred because of the longer
response time and thus helped to avoid potential nuisance trips?
Bob . . .
> [b]
Thanks Bob! A real treat to be able to discuss topics with subject matter experts!
My cluebag continues to fill...
Dave
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=446283#446283
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