|
|
Yes, you'll need a relay in series with the "fat" wire, IF you have an
internally regulated alternator that does NOT stop putting out voltage
when the "thin" wire is disconnected. Looks like Bernie's alternator
will not need that relay. No need to introduce an unneeded additional
component - another point of possible failure.
Finn
Jim Sower wrote:
Finn Lassen wrote:
The small wire goes to its separate circuit breaker. The crowbar is
connected to this wire (and ground).
When the crowbar circuit senses an over-voltage, it clamps that wire to
ground (and pops the circuit breaker).
Only works on your kind of alternator that stops putting out voltage on
the fat wire when it doesn't get voltage in on the "thin" wire. I have an internal regulator, so all I have is a "fat"
(B+) wire. I jump the B+ terminal of the Alt to the "F" terminal with
a couple inches of 17 ga wire. I connect and disconnect the B+ to the
rest of the airplane with a "master" relay powered by the Alt switch on
the panel and protected by Nuckolls' crowbar. In an over voltage
situation, the relay opens. The Alt is disconnected from the airplane
and I could care less what the voltage is. As
someone else asked, does it really stop putting out voltage on the fat
wire - easily measured on the fat wire with a voltmeter - voltage
should drop to maybe 13.2 V as opposed to the 15 - 16 Volts when
alternator is delivering power.
Finn
WALTER B KERR wrote:
Are you saying that you are running an internally regulated,
'one-wire'
alternator & you were measuring current, not voltage? If so, the
current
measurement dropping to zero when you break the B-lead doesn't mean
the
alternator isn't 'putting out.' There won't be any current flowing
because the circuit is no longer complete, but the alternator can
still
be producing voltage potential at the B-lead terminal. The only way
to
tell is to have a volt meter hooked directly to the B-lead terminal
when
you open the B-lead. Same idea as an electrical outlet in your
house:
120 VAC al the time but no current until you plug something in &
turn it on.
The aeroelectric list hand-wringing about 'load dump' should only be
relevant if you lose the connection to the *battery*. If the
regulator
fails & allows unregulated output from the alternator then the
B-lead
overvoltage disconnect relay described in the 'Connection' is what
prevents the high voltage from damaging the a/c electronics. By the
time
you get to this point, 'load dump' is meaningless because the result
of
load dump (overvoltage) has already happened & preventing load dump
is
no longer an issue.
We'll talk when you get here on Friday.
Charlie
---------------------------------
Maybe I misled you. There are 2 wires hooked to the alternator. Only one
wire of the 3 on the plug, but the heavy wire going to the battery is
where I measured current. Are you saying I should measure the voltage on
the small connector wire?
I'm sure you can straighten me out this week end when we're are talking.
Thanks
Bernie
Homepage: http://www.flyrotary.com/
Archive: http://lancaironline.net/lists/flyrotary/List.html
>> Homepage: http://www.flyrotary.com/
>> Archive: http://lancaironline.net/lists/flyrotary/List.html
|
|