[RFI] solar intertie inverter...RFI ???

Jim Brown jim at audiosystemsgroup.com
Sat Apr 24 10:48:56 PDT 2010


One of my neighbors, AE6RF, has several solar systems nearby, and they cause 
him  a lot of grief. As luck would have it, one of those houses was for sale 
as a result of the housing disaster, and I pretended to be a prospective 
buyer so that I could take a closer look at it. :)  

The inverter is not the only part of a solar system that can cause RFI. Two 
others are 1) charging regulators, which are usually pulse modulators, and 
2) circuits that pulse the batteries to prevent degradation. These circuits 
kick in at different times, and the current loop is usually physically large 
-- a simple series loop that includes the pulser and the batteries. 

There are (at least) two important elements of a solution. First, the 
waveshape of the pulses must be well controlled to minimize harmonic 
content. That's a circuit design issue, and modifying after the fact it can 
cause dissipation issues with the devices (because significant dissipation 
can occur during switching). Second, you need to reduce the area of that 
current loop to near zero by having the return conductor retrace its steps 
in the daisy chain. This is counter-intuitive to non-EMC designers, because 
it increases the resistance of the loop, but it's critical to killing RFI. 
That loop should also be twisted pair. 


Jim K9YC 

 On Sat, 24 Apr 2010 05:25:01 -0400, ny9h wrote:

>As i get ready to commit to a 10kw solar array, i wanted to feel 
>comfortable about NOT getting crud from the inverter. It's a Froniac


>So i got a location where the contractor has one installed.  i drove 
>over to Greenberg,PA.. (40 miles away)... and found the 60 foot wide array 
>I was hoping to use my car 706 to tune around, but the sky above had 
>big hi tension stuff,,,, ( what a place to have a house ??)
>I took my kenwood f6 in ssb & am .,..and probed around the inverter box.
>All was quiet except at the very top of the box, where i could find 
>some hash.Gone within a foot distance. I take this to mean there 
>exists the possibility that I might be able to ear some crud if I 
>have this system on my property. Is it nor reasonable to believe that 
>I could choke what little junk is coming from the box???
>I will insert a clause in the contract,  requiring the contractor to 
>modify the equipment or equipment enclosure to remove or reduce any 
>interference caused to, or from the owner's radio equipments.
>But does anyone , anywhere , have any experience with the Fronius product,
>being a EU build, I suspect it is actually very quiet.
>tnx  bill

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