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gmcjetpilot
Joined: 04 Nov 2006
Posts: 170
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 Posted: Thu Jan 25, 2007 10:20 am Post subject: IR alternators in airplanes (JUST say NO to OV relays) |
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| Quote: | From: "Robert L. Nuckolls, III"
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| Quote: | >Can I use the LR3C from B&C to prevent OV
>problems? Or, does someone else sell such a
>device?
>
>Thanks David Weber
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>Internally regulated alternators are a what-you-
| Quote: | see-is-what-you-get. If it is your desire to have
these marvelous-but-not-perfect devices operated
within the design goals we've been using for
externally regulated alternators then some form of
external adaptation is necessary necessary.
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What does that mean?
Yea see-is-what-you-get inside of an internal
regulator:
http://img103.imageshack.us/my.php?image=slide2jo1.jpg
Here is a typical external or LR3C regulator
http://img62.imageshack.us/my.php?image=slide7bj9.jpg
or
http://img269.imageshack.us/my.php?image=slide6it5.jpg
OV protection is for externally regulated
alternators, NOT internally regulated. WHY?
Because internally regulated alternators are not
designed for external protection. External
regulators are old fashioned, even the LR3C needs
over voltage protection because they have
no protection at all (unless you use a modern
external voltage regulator, like a V120 below).
If you want OV protection for an Externally
regulated alternator use this regulator,
http://195.125.241.148/cgi-win/product.exe?V1200
OR if you are worried about your I-VR alternator,
buy a plane power alternator from Plane power,
which Vans Aircraft sells.
http://www.plane-power.com/
or
http://www.vansaircraft.com/cgi-bin/catalog.cgi?ident=1169746824-338-558&browse=engines&product=alternator-kit
The level of fear of OV is not justified by the facts
and its based on ignorance, urban legend and folklore.
Very few I-VR's have OV events and when they do
they are mild and easily controlled with RPM or
adding extra electrical load (say landing lights) or
its just not an issue.
If you want to add an OV monster relay on your
plane's I-VR ND alternator, please consider NOT
and doing the above.
The choice is about 10% technical, 40% preference
and 50% emotional, but OV relays are old time news.
The emotional part is what some vendors like B&C
use as a sales pitch with dark and stormy night
stories. If you are VFR and have modern avionics
that can handle 10-32 volts and 60 volts surge, as
most can, than considered NOT using an OV relay.
When you hear another OV happened with an I-VR,
ask really, what happened? The reality is not as
bad as the imagination might lead.
(*Call your manufacture to confirm. If operational
voltage is listed as 10-32 volts in the owners manual,
chance is the electronics has filtered protected power
supply.)
Just say NO to BIG, FAT, Heavy over voltage
relays. This is antiquated technology based on the
old days of externally regulated alternators that had
OV events and BAD ones at that. Modern OV
alternators are less likely to have over voltage
with their ON BOARD sophisticated regulators
that monitor things like temperature, which
external regulators could not ever dream of.
JUST SAY NO TO OV RELAYS, WELCOME
TO THE 21st CENTRY, I-VR ALTERNATORS
OR SOLID STATE OV PROTECTED EXTERNAL
VOLTAGE REGULATORS.
No offense to Bob, but OV relays are a step backwards.
Cheers, George
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gmcjetpilot
Joined: 04 Nov 2006
Posts: 170
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| Posted: Fri Jan 26, 2007 11:39 am Post subject: IR alternators in airplanes (JUST say NO to OV relays) |
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| Quote: | From: john(at)ballofshame.com (john(at)ballofshame.com)
External OV protection with an external regulator is solid state.
When the crowbar trips, the field is grounded, thus driving the
alternator output to 0. The fact that the field circuit breaker pops
some time later is beside the point. If you wanted to you could
wire the the field with a massive bus bar and leave the circuit
breaker out completely. The field wire will be at 0 potential going
into the regulator because it's grounded. Of course, doing this
would destroy your battery in short order.
Putting OV protection on internal regulators requires the relay
>to work and is much kludgier. Though the module might be the
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>same, they function COMPLETELY differently and shouldn't be
>confused.
John I'm aware how the OV relay / crow bar combo works on
an I-VR, and I know how a crow bar works on an E-VR.
Yes, they are different.
With the E-VR you kill the FIELD. Great! I understand you think
the crow bar will short the field to ground. Well from what I've
seen it removes power to the VR that collapses the FIELD.
It depends how you wire the crow bar, and according to Bob's
schematics the crow bar goes right on the CB not the field
terminal of the VR. Whether it shorts the field or shorts the
CB removing power to the FIELD, it's no matter; the real key
is the alternator FIELD collapses and power is not produced
by the alternator.
On the "Kludgier" OV relay for a I-VR, I agree it works different
and is a "Kludgier". That is my point.
You make a point I've made many times, I-VR and E-VR are
completely different and should not be confused. Trying to
use OLD technology originally made for E-VR, like the OV
relay, is not the way to go today.
Bob's new module will open an OV relay by removing
power to the relay. It may be an improvement to the original
crow bar, which was kind of unstable, but the concept is the
same, a BIG OLD OV RELAY.
My point is LEAVE the I-VR alternator alone and don't
mess with it. Wire it properly and operate it properly.
If you can't stand it and are in fear of OV do something
else.
The best on the market for I-VR are the Plane Power units,
where the I-VR has an integrated OV module that does
turn the power off to the VR and FIELD, verses an OV relay
which just cuts the out put with the FIELD still energized.
It should give peace of mind to those who are afraid of OV.
It does it elegantly with out a BIG OV RELAY.
John I basically agree with everything you said, but a typical
E-VR is stuck in the 70's. The $10 Ford alternator people use
has about 3 transistors and a diode voltage reference. Yes it
is solid state but OLD solid state. Even the B&C LR3C
that sells for $230 is really a three transistor old design. It
does have a crow bar in it, but that crow bar is an old idea.
The new stuff has solid state power switching. Short circuiting
CB's to trip/short them internally to remove power to the
FIELD (or shorting the field as you like) is really NOT the way
to go in the year 2000's.
I-VR's have more technology and have been the focus of
technological improvement, since most small alternators
made since the early 80's are all internally regulated. If you
are tempted to add a OV relay for peace of mind consider
NOT doing it, and if you really are worried, get a Plane
Power unit.
If you do have an E-VR alternator the $70 Transpo V1200
is a modern E-VR that uses technology that I-VR's have,
as well as OV protection. With the Transpo V1200, an OV
condition is shut down by removing power to the FIELD. It
does not short anything to ground like a crow bar.
Cheers George
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