Dave;
Thank you for verifying what the problem
was, and an easy solution. I’ve also been seeing 14.5-15 volts at
times, and it has been on my mind this week that I needed to address that. I
had concluded it was likely caused by voltage drop in the field circuit, but
hadn’t really considered it is all the drops from the alt output, back to
the battery, and back to the field.
So to verify (for me and others who have
done the internal disconnect from output to voltage regulator/field supply); you
connected from the alternator output (‘B’ terminal) back to the
field via a relay; where the relay power has the over-voltage protection and
panel switch.
Now that you’ve done it seems obviousJ.
Al
-----Original Message-----
From: Rotary motors in aircraft
[mailto:flyrotary@lancaironline.net] On
Behalf Of David Leonard
Sent: Thursday, January 07, 2010
9:21 AM
To: Rotary motors in aircraft
Subject: [FlyRotary] High voltage
problem fixed for real
I finally figured out why my voltage had been creeping
up - I was losing a small bit of voltage with each crimp and connection and
section of wire in the alternator field circuit (went from the main buss,
through a fuse, 4' to a switch, then 4' back to the alternator. That
added up to 0.4 volts over the length of the circuit when the field was drawing
3.5 amps. If that draw ever goes up in flight the voltage drop would be
higher. More importantly there was a bad crimp in the
b-field wire which would have been causing an obvious drop in voltage between
the alternator output and the rest of the electrical system.
I fixed the crimp and installed a relay near the
alternator to handle the field voltage. This not only got my operating
voltage back down to 13.8 volts, but also removed the last bit of alternator
noise from the headsets. Cool!