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Buly,
Wow, you’re really going to put me
on the spot here. I’m assuming you have the small 55amp ND
alternator. Yes?
What we’ll need to do the conversion
is a small piece of 1/8” phenolic sheet. A soldering iron (I’m
sure Tracy has
one of these). A 12” length of 20 gauge tefzel wire, two ring
terminals, terminal crimper, wire stripper, a piece of shrink tubing and a
small grommet. We’ll also need a few metric screws, nuts &
washers. Sorry but I’m not sure of sizes though. Surgery
takes about 30 minutes. I’ve attached a picture for homework.
Note the brown piece of phenolic. This bridges the gap left by removing
the internal regulator. Also, the lead coming out of the brush block is
the field lead to the external regulator. The short white wire completes
the field circuit to ground.
Thanks,
Mark
From: Rotary motors in aircraft
[mailto:flyrotary@lancaironline.net] On
Behalf Of Bulent Aliev
Sent: Thursday, September 08, 2005
2:48 PM
To: Rotary
motors in aircraft
Subject: [FlyRotary] Re:
Overvoltage control (help Ed A)
Mark, I'm bringing my alternator to Soggy Bend for you to alter it. I
don't have the Things to do it myself:) What else do I need? It will be a good
learning experience for the rest.
On Sep 8, 2005, at 3:39 PM, Mark R Steitle wrote:
Ed,
I wrote up step-by-step
instructions a while back on converting an ND alternator from internal
regulator to external. If anyone is interested, let me know and I will
send it to them directly. This conversion makes it so that you can shut
the thing down by cutting the power to the field wire as is the method used by
the Perihelion Design OVM.
Mark S.
From: Rotary motors in aircraft [mailto:flyrotary@lancaironline.net]
On Behalf Of Ed Anderson
Sent:
Thursday, September 08, 2005 2:24 PM
To: Rotary motors in aircraft
Subject:
[FlyRotary] Re: Overvoltage control (help Ed A)
On
alternators with internal regulators (most Auto alternators), breaking the low
current Field circuit may not (will likely not) stop the alternator from
producing current. Most of the alternators need the field coil current to
"bootleg" their start in producing voltage, but once generating - do
not need the external field coil current to continue. That is why if
you have an alternator with an internal regulator, you can not depend on
opening the low current field coil circuit to kill the power and why you
would need a method similar to the one described in this thread of
breaking the high current (Power lead usually referred to as the "B"
lead) through a high capacity relay (Contactor) or a "fuse".
There are always side
effects when interrupting a high current flow (less if the current flow is
minimal). If there is a large inductive load (such as a large
DC motor) then the back EFM can produce a high voltage spike. There are
reports that alternators may increase their voltage dramatically if there
is a sudden loss of load -but, its never been clear to me if that is a
malfunctioning generator or caused by the lost of load - never been tempted to
experiment. However, I once had two batteries which connected to
the alternator through their contactors. I could switch the batteries on
and off the alternator line without any ill effects - not quite the same as
dumping a large load - but, after starting on just one battery, the load was
fairly high when put back on line. However, one battery was always
on-line.
So not certain what
effect breaking the "B" lead would be (since it would depend on
conditions) but since many designs have a "fuse" in the
"B" lead for that purpose, I am going to hazard my opinion that the
effects of breaking the "B" lead may be less serious than what-ever
bad situation is causing you to want to do that in the first place.
Ideally, of course, is to have an externally regulator alternator (or a
modified auto alternator with the internal regulator disabled so unable to
provide the field coil internally) and a low current circuit breaker tripping
mechanism for the field coil.
----- Original Message
-----
Sent: Thursday, September 08,
2005 2:14 PM
Subject: [FlyRotary] Re:
Overvoltage control (help Ed A)
If you don't have a
low current way to break the field current, and need to break the high
current line, then you have to used this OV module to trip a breaker
that's holding in a main contactor for
your high current "B" lead. If any of that was confusing, Ed can explain it :-)
Cheers,
Rusty
======================================
Help Ed. I almost
understand Rusty's comments, but Mark S left me in the dust. Us old dogs are
sometimes hard to train!
I think that with an
internal regulator; just because you break the field current supply , a
failed regulator may keep powering the field with the internal alternator
voltage. The continous breaker in the big alternator line can protect the
battery and airplane except what happens to the alternator in the meantime if
the interal regulator is applying a large field current to the field will the
alternator burn up quiet rapidly and possible start a fire?
Bernie, soggy Treasure Coast
although we had a bonanza just taxi in so must be drying out a little
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