Inverter generates RF interference

[link]

I've got a grid tied solar array that generates a great deal of
interference with AM radio signals. I can't pick up any AM stations
inside the house when the inverter is running. At night when the
inverter is shut down my stations come in fine.

Any ideas on how to cut down this interference? I'm getting it on
radios powered by the mains power and battery power so it's actual RF
from the air but it doesn't seem to affect radios outside the house.

 

[Pszemol]

Any ideas on how to cut down this interference?

Does your "inverter" create sine wave or square wave?
If the second case, than this is the source of your problems.
I do not know the easy way out other than replacing
inverter for a sive wave electricity source...

You can also go the other way: install AM antena
and use it as a source for your radio receivers
if they have the antena plug exposed...

 

[link]

Does your "inverter" create sine wave or square wave?

It's a grid tied Sine Wave Inverter. Specifically a Xantrex SunTie
1500. It matches phase, frequency and voltage with the grid. This is
what has me puzzled? In reality, I think the sine wave is made up of
many discreet steps. The number "36" has been brought up before.
Xantrex offered a free upgrade last year. This upgrade really boosted
my energy production but at the same time it caused all this RF
interference. I guess for the extra 30% power I'm producing now I can
live with the RF, but I would like to be able to listen to the ball
games.

 

[Ken Weitzel]

It's a grid tied Sine Wave Inverter. Specifically a Xantrex SunTie
1500. It matches phase, frequency and voltage with the grid. This is
what has me puzzled? In reality, I think the sine wave is made up of
many discreet steps. The number "36" has been brought up before.
Xantrex offered a free upgrade last year. This upgrade really boosted
my energy production but at the same time it caused all this RF
interference. I guess for the extra 30% power I'm producing now I can
live with the RF, but I would like to be able to listen to the ball
games.

Can't help but be curious about where in the world you are?

The reason being, that if it is indeed RF, aren't
your neighbors gonna be a little upset with you?

Take care.

Ken

 

[Stan]

}I've got a grid tied solar array that generates a great deal of
}interference with AM radio signals.
Hmmm...the question becomes: is the interference being radiated to
each radio? OR, is it being "impressed" onto the AC lines into your
house? If that's the case, some low pass-filters will do the trick.

Stan.

 

[w_tom]

Maybe an inverter bought on price rather than based upon
numerical and technical specs. Any decent inverter includes
circuits to eliminate the RF noise. This being decades old
technology. However too many consumers cannot be bothered
with the science; which is why inferior inverters are sold.

Your solution. Big bucks for filters that would have
normally been part of the inverter for little additional
cost. To the benefit of others - did it come with a long list
of numerical specs? If not, then they are probably forgetting
to provide 'standard' functions - such as filters. America
needs more immigrants to explain these so basic technical
concepts to us. This noise problem demonstrating a
consequence when consumers don't first demand technical specs
- only buy on price. It is not a personal attack. Such
failures that were not acceptable 30 years ago are now more
common as products are bought based only upon one
specification- price. Its called a bean counter mentality.
Specs (or missing specs) would have made the RF interference
problem painfully obvious up front. No long 'page plus' list
of numerical specs? Then expect the worst.

 

[Asimov]

"link" bravely wrote to "All" (25 May 04 23:33:45)
--- on the heady topic of "Inverter generates RF interference"

li> From: link <[email protected]>

li> I've got a grid tied solar array that generates a great deal of
li> interference with AM radio signals. I can't pick up any AM stations
li> inside the house when the inverter is running. At night when the
li> inverter is shut down my stations come in fine.

li> Any ideas on how to cut down this interference? I'm getting it on
li> radios powered by the mains power and battery power so it's actual RF
li> from the air but it doesn't seem to affect radios outside the house.

Some things to try:
- wrap all the wires going to the inverter through a large ferrite toroid.
- add series inductors & bypass the line with capacitors.
- arrange the input/output wires at right angles to one another.
- shield the inverter inside a grounded electrical box.

.... She said it was either her or the Ham Radio... OVER...

 

[link]

Hmmm...the question becomes: is the interference being radiated to
each radio? OR, is it being "impressed" onto the AC lines into your
house? If that's the case, some low pass-filters will do the trick.

Stan.

It seems to be radiated to each radio rather than being impressed onto
the AC lines. I'm getting the interference on battery powered radios
as well as those powered by mains.

 

[link]

Maybe an inverter bought on price rather than based upon
numerical and technical specs.

No long 'page plus' list
of numerical specs? Then expect the worst.

It's a Xantrex Sun Tie XR 1500

http://www.xantrex.com/products/product.asp?did=133

The Inverter was purchased based on performance claims by the
manufacture; Performance claims that were never achieved until they
recalled and redesigned the units. This took about 3 years and some
diligent work from some very dedicated "Customers". This inverter is
supposed to be the top of the line model made here in the USA,
designed to be intertied into our USA electrical grid. This is the
third unit I've had. The first unit died an early death but it didn't
generate RF interference. The second unit also generated no
interference but also generated very little power. This third unit
really performs very well as far as power generation is concerned but
it also generates this RF interference.

It came with a pretty long list of specifications. The data sheet is
online and obtainable from the above link.

The (thick) maunal goes on to chart Efficiency Curves and Temperature
derating curves which I've verified with my own data collection system
which is also online (sometimes) at
http://www.daemonet.net/energy/index.php

 

[w_tom]

The specs do provide cursory information. IOW only some
important technical numbers are provided. Important is
Harmonic distortion of less than 5%. It means that AM radio
interference probably (only maybe) is not coming out of AC
power output. But, for example, I see no reference to any FCC
requirements. No reference to even claim it does not
broadcast excessive RF radiation. IOW by interfering with the
AM radio (which even computers are not permitted to do), it
does exactly what specifications claim.

Just like power supplies in computers and plug-in UPSes, the
inverter uses a PWM to create AC voltage. That is typical
source of RF interference. And just like those power supplies
and UPSes, the inverter should create just as minimal
interference.

Increased interference could indicate a partial failure or
weakness inside the inverter. Hard to say from so little
information on their web site. However a quick examination of
their box interior suggests nothing to eliminate RFI/EMI.

You could take it one step farther - to determine where
noise is being radiated from. From incoming DC voltage wire
(acting as an antenna)? On outgoing AC wire? From directly
inside box? Use the battery powered AM radio. And use radio
on different stations - powerful and weak - to categorize the
amount of interference energy being transmitted at different
locations. That information might help to further eliminate
the RFI/EMI problem - the reason for AM radio interference.

But again, those specs don't even claim to meet FCC
requirements. FCC Part 15 requires that the inverter not
interfere with radio reception.