[RE-wrenches]

[jberdner at sma-america.com]

David:

You might try a common mode choke and a de-coupling capacitors at the dc
input to the inverter.  Use a film type caps and keep this stuff as
close to the inverter as possible.  You might need to add some big
electrolytic's in addition to the film cap on the battery side.  

With #6 you might need a big core to get enough turns on it.
Use a ferrite core about 2.5 to 3" in diameter and make 5 or 6 wraps of
the positive around the core - let's say from the 10:00 to 2:00
position.  Then do the same thing with the negative but at the 8:00 to
4:00 position.

IN ASCII DRAW:

B+ ------      ----- Inv+
     |   \0000/   |
    CAP ( CORE ) CAP    
     |   /0000\   |
B- ------      ----- Inv-

This will help clean up the dc side but you may still get some
interference from the ac side.  If yes, then try a common mode choke on
the ac side as well but without the caps.

Hope this helps,

John Berdner



-----Original Message-----
From: David Palumbo, Independent Power & Light [mailto:ipl at sover.net] 
Sent: Tuesday, July 16, 2002 2:53 PM
To: Wrenches
Subject: [RE-wrenches]

We recently installed a small off grid 24v PV system utilizing an
Exeltech
XP1100 sine wave inverter and an Iota DLS 24v 25 amp battery charger.
The
system also has an Iota automatic generator transfer switch. The system
has
245 ahrs of battery storage and is grounded according to our standard
procedures.
It is installed in a small home that previously operated on gas lights
and a
small generator (Honda 3k inverter gen) for TV, microwave etc.

The television is picking up interference from our system. With the TV
powered by the inverter it has some audible static and visual snow, and
diagonal lines that were not there when the Honda ran the TV all alone.
When
the generator is run (without battery charger for now), and the
autotransfer
switch loads the gen with the TV, the TV picture and sound are no better
until the inverter is actually shut off. At this point we are back to
the
original TV picture and sound before our system was installed. When the
Iota
battery charger is on the TV is at its worse state of picture and
interference.

The tech help at Exceltech suggested that the 6 foot run to the inverter
using #6 AWG cable (1% voltage drop at 1,000 watts)is too far, that
placing
the inverter directly on top of the batteries would clear up the
problem.
This we just can't do although we did twist the cables around each other
as
also suggested. No relief. The inverter is seperated from the TV by a
wall
and by a distance of 16'. The batteries are located in a battery box in
the
same large room as the TV and are 14' away.

The tech help at Iota offered that earlier models of the charger had
interference issues but that these had been addressed in the newer
versions
(we are told that we have a newer version as indicated by the blue line
under the Iota model number). It was suggested that a jumper wire be
added
between the DC negative input to the charger and the ground terminal
(creating a ground loop). Again, no relief.

Any thoughts?

Barry Shaw
Independent Power & Light

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