>I know you extroll the virtues of getting the main fuse/breaker off the
>panel to reduce noise in the system. I guess I don't understand how merely
>moving its location will do this.
>Looking at your wiring diagram the alternator output is connected to the hot
>side of the starter contactor and then through the master contactor. The
>feed then goes to the battery. Great except the main fuse block feed is
>connected at the same battery terminal. Isn't this the same electrically as
>running the feed to the main fuse block and then connecting to the battery?
Noises generated by the alternator are in form of an
AC ripple voltage that remains on the output after
power passes through the rectifier diode array. This
is a signeal with a voltage value of approx 700 mv peak to
peak but and a current capability equal to 5% of
the alternator's present load. . . 40A DC output
is accompanied by 2A of pk-pk ripple noise. This is
why ground-loop noise goes UP as loads on the alternator
are increased.
The best filter in the airplane is the battery. Especially
if it's an RG battery with a very low internal impedance
(on the order of 8 milliohms). The 2A pk-pk ripple
current impressed across 8 milliohms is only 16
pk-pk. Obviously, connecting the alternator directly
to the battery terminals is the way to go . . . indeed
that's what I show in the Electric Panel on a Budget
article on our website.
Any intervening wires between the battery and the
alternator increases the apparent impedance of the
battery and reduces its effectiveness as a filter.
So, the goal is to make the shortest possible, fatwire
connections between battery and alternator b-terminal
without taking it past the main bus!
The goal is to reduce the amount of wire shared by
both the alternator and mainbus feedline and to make
the connections between battery and alternator as
short and low a resistance as practical. Remember,
we're talking millohms here and every wire and joint
in the wire adds its little bit of ripple-noise amplifying
resistance.
The single point ground system we recommend is used to
get as much of the airframe's resistance out of crictical
systems power pathways. Moving the alternator b-lead
to the starter contactor on the firewall is doing the
same things for the hot side of the power system as
we do for the ground side.
Bob . . .
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( The only time you don't fail is the last )
( time you try something, and it works. )
( One fails forward toward success. )
( C.F. Kettering )
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http://www.aeroelectric.com
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