[RE-wrenches] AM noise on batteryless inverters

[Exeltech]

RFI (radio frequency interference) from inverters
is a fact of life.  This is especially true at
lower frequencies, such as for AM radio.

There isn't a cure-all.  Each make and model of
inverter will differ in the amount of interference
it generates.  Steps to reduce the problem also
differ.

Ferrite cores (mentioned below) may help.  These
need to be installed around DC and AC leads.
Multiple cores on each DC leg are almost always
required due to the very low impedance presented
by the DC input side of the inverters.  Looping
AC conductors multiple times through a large
ferrite core will also be helpful.
 
Bypass capacitors are also often beneficial when
they're connected to the conductors on the battery
and load side of the ferrite cores.

Ensure all chassis screws are clean and tight.
Earth grounding the inverter chassis may help.
Experimenting will be needed with and w/o this
ground to see which works better.

Separate the radio receiver from the inverter as
far as possible.  Distance is your friend here.

Ham radio equipment tends to be less affected by
inverter RFI because the receivers are fed with
coaxial cable, which is self-shielding.  The coax
is connected to antennas that are commonly 50-100'
or more from the inverter.

There are some common steps you can try .. but in
the end .. steps unique to the particular site
may also be needed.


Dan



--- On Thu, 6/17/10, Darryl Thayer <daryl_solar at yahoo.com> wrote:

> From: Darryl Thayer <daryl_solar at yahoo.com>
> Subject: Re: [RE-wrenches] AM noise on batteryless inverters
> To: "RE-wrenches" <re-wrenches at lists.re-wrenches.org>
> Date: Thursday, June 17, 2010, 11:30 PM
> I have heard that putting small ferrite donuts
> around the AC and DC wires will reduce this
> noise.  Place them inside the inverter.  they are
> avaiable from DigiKey
> Darryl
> 
> --- On Thu, 6/17/10, jay peltz wrote:
> 
> > From: jay peltz <jay at asis.com>
> > Subject: AM noise on batteryless inverters
> > To: "RE-wrenches" <re-wrenches at lists.re-wrenches.org>
> > Date: Thursday, June 17, 2010, 8:35 PM
> > HI All,
> > 
> > Say I've had a question from a client about AM radio
> > noise from his battery-less inverter.
> > 
> > I'm wondering if there is any other folks out there
> > who have found this to be problem?
> >
> > Now I realize that most people listen to AM in the
> > evening when the  inverters are non-op so this
> > might not be a problem for most people.
> > 
> > Thanks in advance,
> > 
> > jay
> > peltz power