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Re: [RFI] Solar Inverter.

To: rfi@contesting.com
Subject: Re: [RFI] Solar Inverter.
From: Larry Benko <xxw0qe@comcast.net>
Date: Mon, 19 Mar 2012 22:29:46 -0600
List-post: <rfi@contesting.com">mailto:rfi@contesting.com>
Ditto on the "contract stipulation" requiring no EMI which is a good 
idea for ALL installations and purchases where objectionable 
interference may be a possibility.  However assuming that fixing the 
inverter is the problem at the present I would suggest that work I have 
done on eliminating RF interference on high power electronic ballasts 
would be similar to what the solution is for this problem.

Both the electronic ballasts and the solar inverter are kilowatt plus 
devices.  Both have 2 primary ports (DC in and AC out for the inverter) 
and both involve high power semiconductor switching devices.  I have not 
personally been involved with any solar inverters but have been 
successful in eliminating interference from several high power 
electronic ballasts.  These electronic ballasts produced S9+25dB 
interference levels at distances of 50ft.  Take a look at 
which shows measurements and what was done.   Ferrites alone were not 
adequate to eliminate the RF interference.

Larry, W0QE

On 3/19/2012 9:49 PM, Dale Svetanoff wrote:
> Neil,
> Considering the cost of cleaning up "dirty" inverters, my first thought is
> to ask your local ham friend if he had stipulated anything in the contract
> with the solar system provider to make them responsible for not interfering
> with his radio operation.  If he did not, he may be in for a very expensive
> cure to the problem.
> As in any RFI situation, you have a source (which appears to be the
> inverter) and a victim (the antenna(s) feeding his radio receivers).  The
> first thing to do would be to determine the coupling mechanism, as in is it
> via the low voltage/high current input wiring of the inverter or via the
> 120/240 VAC house wiring that is attached to the output.  One way to do
> that would be to place a dummy load (lots of incandescent light bulbs) on
> the output side of the inverter with the leads to the house wiring
> disconnected, and then power up the inverter.  If the noise is gone or
> reduced, then he knows that the house wiring is a major part of the
> coupling mechanism and filters on the inverter output should be beneficial.
> If the noise level hardly changes, then it would seem to be the input
> wiring to be the culprit.  In reality, I expect that both wiring systems
> may be radiating.
> I am not familiar with this particular brand of power filters, but they do
> appear to be "real" industrial grade filters.  Having worked for more than
> 13 years at a company that had a filter product line similar to these, I
> can tell you that yes, they will be pricey.  Do not be surprised if the
> filter costs exceed $1500 or more.  At that price point, it may be worth
> looking at what else could be done.  One suggestion is to increase the
> distance between source and victim - in this case, get the antennas further
> away from the house.  It may be necessary to move them by several hundred
> feet or to re-orient their position relative to the house and its wiring.
> Another suggestion, of course, is to open up the inverter to see how it is
> wired and constructed, and then plan a method of applying internal chokes
> and by-pass capacitors to knock down the offending hash.  Of course, this
> path is liable to void any warranty on the unit.
> Remember, the best cure for reducing RFI from a specific source is to
> reduce or eliminate the emissions either within the source itself or as
> close to the source device as possible.  So, if he ends up buying the
> filters, he needs to install then directly adjacent to the inverter and
> connected with the shortest possible leads.  He must also ensure that there
> is a proper, low impedance ground path between the filter case and the
> inverter case (assuming metal cases).  Note that while the inverter should
> be grounded to meet codes and for safety, that grounding path is likely to
> be long.  No matter, because we are talking common mode radiated emissions,
> what matters most is the path between filter and inverter because that is
> where the circulating currents will be located.
> Finally, an obvious question:  Is the inverter in a metal case or chassis?
> One would hope so.  If not, it needs to be.
> I really hope that your friend can throw this whole mess back at the
> installer or equipment manufacturer, where it belongs.  I hope I am wrong,
> but this could become a very costly fix.
> 73, Dale
> Sr. EMC Engineer
>> [Original Message]
>> From: Neil&  Heather<neil.goodell@myfairpoint.net>
>> To:<rfi@contesting.com>
>> Date: 3/19/2012 9:10:57
>> Subject: [RFI] Solar Inverter.
>> Good Evening all.
>> I received a call from a local ham who is experiencing serious RFI from
>> a 3500kwH system he has just tied in at his house.
>> He reports S-9+ when the inverter is on,shut off the inverter,noise is
> gone.
>> He also forwarded this link :
>>    http://www.radiuspower.com/inverter-emi-filters.html
>> Has anyone on the list had any experience with theses filters?
>> There are a bit pricey,but,at this point, the fellow ham is only
>> concerned that they work.
>> Any information on these filters,or others who may have tackled Solar
>> power Inverter RFI, are welcome.Thank you.
>> 73
>> Neil
>> AE1P
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