EMC issues, historical and now

[tgale]

I was just browsing the forum, for the first time in many years, and came across the posts from ‘Warpspeed” and ‘Betwixt’ concerning the EMC-related comments and contributions elsewhere from Ivor Catt in ‘Electronics World’ journal around May-June-July 2003 and maybe earlier.

There were other “alias” contributors such as Ivan L.E Fant, Ouida Dogg, and Oliver Fish as well as myself as “Eima Burdd”!.

I wonder if any of them are still active?

Another, more topical, subject that would be interesting to hear opinions and/or comments about is the EMC compatibility of solar panel installations, especially the inverters used in them, which (particularly the cheaper versions) radiate enormous amounts of radio-frequency interference to many users of the electromagnetic spectrum.

My new mail address is <deleted, see forum rules> since my old ISP became rubbish after the take-over by the national phone company KPN.

Wishing you all a Happy and more importantly a Healthy New Year 2024!

 

[cupoftea]

I doubt they radiate strongly in the high MHz range. Not strong enough to knock out eg police radios etc. Even hobbyy drone flyers wouldnt be bothered. Maybe the old FM or AM stations would suffer, but not the ones using the more modern digital modulations.

Go fly a drone over a solar farm...i bet there is no problem.

Though I believe in many cases its just a case of using a small NiZn common mode choke at the front end of the inverter etc...and Y caps downstream of it. With such, you wont be bothered with your radios etc.

If the inverter is in an earthed metal case, then i would doubt any problem at all.

I regularly kindly hear from Betwixt here..Warpspeed now and again still.

 

[D.A.(Tony)Stewart]

I agree that large PV panels act as large 2-way antenna to EMI when pulsed with suboptimal MPPT loads but certainly can pick up AM and SW radios or convert CM noise to differential being unbalanced sources.

If you have a problem, define it as well as you can.

 

[tgale]

I doubt they radiate strongly in the high MHz range. Not strong enough to knock out eg police radios etc. Even hobbyy drone flyers wouldnt be bothered. Maybe the old FM or AM stations would suffer, but not the ones using the more modern digital modulations.

Go fly a drone over a solar farm...i bet there is no problem.

Though I believe in many cases its just a case of using a small NiZn common mode choke at the front end of the inverter etc...and Y caps downstream of it. With such, you wont be bothered with your radios etc.

If the inverter is in an earthed metal case, then i would doubt any problem at all.

I regularly kindly hear from Betwixt here..Warpspeed now and again still.

Unfortunately these inverters do affect emergency communications - here we have the "C2000" comms links for them and they have become limited in range due to the interference they cause - here is one quote (however it is in Dutch) - <https://www.security.nl/posting/795...mers+zonnepanelen+zorgen+voor+C2000-storingen> and it being taken seriously even with the Government - <https://solarmagazine.nl/nieuws-zon...-c2000-door-zonnepanelen-snel-opgelost-worden> - and there are many others who are affected by this issue. As for installing a common-mode choke and downstream capacitors, that would involve an extra cost which the typical household over here would never welcome. It is my own experience that due to new house builds near me with solar installations, the area around 14 MHz "shortwave" and also around 2400 MHz are sometimes completely unusable - I have walked around the new building area with a portable receiver and found nearly all of the houses with panels are emitting such radiation - I also see these interfering signals using one of my spectrum analyzers in my workshop couples with appropriate antennas. I will shortly walk around these housing areas with a portable analyzer which I have available.

 

[tgale]

I agree that large PV panels act as large 2-way antenna to EMI when pulsed with suboptimal MPPT loads but certainly can pick up AM and SW radios or convert CM noise to differential being unbalanced sources.

If you have a problem, define it as well as you can.

As I have indicated elsewhere in this thread, I do plan to survey the new house-build area near me with a portable spectrum analyzer and indicate where the interference is higher and plot that on an official map of the area. With these measurements I will indeed be able to define these problems more clearly.

 

[D.A.(Tony)Stewart]

Why not use film caps to block EMI? Sell them to EMC emitters.
Tell them you are reporting interference to the regulators for reasons above.
You might be able to hear them on an AM quiet channel. or RSSI on Wifi with app.

Ferrite Balun clamps will be cheaper than new inverter cable loop corrections to make twisted pairs.

You will two types of Ferrite for HF and UHF noise.

 

[Easy peasy]

You would be amazed how much work there is out there for consultants solving ( ad-hoc & post-hoc ) emc issues on new site installations !!!

 

[tgale]

Why not use film caps to block EMI? Sell them to EMC emitters.
Tell them you are reporting interference to the regulators for reasons above.
You might be able to hear them on an AM quiet channel. or RSSI on Wifi with app.

Ferrite Balun clamps will be cheaper than new inverter cable loop corrections to make twisted pairs.

You will two types of Ferrite for HF and UHF noise.

Many installation companies over here and also elsewhere have been advised of this problem, and even offered solutions, but they will simply respond with something like "Our installations are economically sound and have been passed and comply with all environmental regulations. We are a professional business with qualified technicians, and our installation packages are already complete so we will not add to or change them unless we are informed of any new regulations which come into force.". In other words, 'We know what we are doing, we save the planet, and you are not the government!'... As for ferrite clamps, I am fully aware of their properties, but especially over here, their cost may be minimal but even a buyer of a new 600,000 euro house will object to an added cost of 10 euros - price of things is way more important to them than any issue concerning compatibility; an installation company will price their installation price down to the cent, citing that they are the cheapest but best and all the 'noise' about emissions are rubbish and only come from ignorant minority interests!

 

[cupoftea]

As for installing a common-mode choke and downstream capacitors, that would involve an extra cost which the typical household over here would never welcome.

Thanks, but i meant the actual inverters, inside them, they should have such components placed to solve EMC.
It would be good to see the schem of the inverters if poss...though i appreciate probably not.
I mean, just maybe they dont even have common mode chokes inside them. Maybe they never even passed an EMC test?

--- Updated Dec 29, 2023 ---

Also, it is an actual fact, that no offline SMPS will ever pass radiated EMC testing , if it is not encased in a earthed metal enclosure.
Maybe some resonant ones could possibly get around this...but even that is unlikely, since even the LLC usually hard switches the magnetising current at turn off.
Also, the PFC stage is not resonant and so will spew out loads of radiated emissions.
Most companies dont have to put their product through radiated EMC testing in order to sell it on the market.
Its just one of those things.

What is the earth wiring like?.....is it one big loop?....or does earth go to every bit of the installation, in a nice tight loop with the line and neutral?

Trace out the loops for UHF currents (common mode currents) that can flow from Line or Neutral to earth....if
you can trace out wide loop areas then you have a problem.
A loop of conductor is an antenna.
As discussed, the wiring of earth needs to be tight with the line and neutral in all cases and places.
You dont want loop antennas everywhere.

You often find that the earth wire that goes to the case of an offline converter, comes SEPARATELY to the line and neutral....
this is an EMC disaster in the making!!!
But it is regularly done all over the place.

I can almost gaurantee that you have an earth wiring problem as discussed...and that this is made worse by a possible lack of common mode filtration within the units.

Electricians unfortunately dont think about the area enclosed by earth/line or earth/neutral current loops when they wire up installations.

If you have a product such as yours, then the earth line and neutral for each individual product should all come together in the same 3 core cable....and after its split out of that...you still need to look into any loop areas of earth/line and earth/neutral.

I gaurantee your problem is earth loop wiring as discussed.....combined with a possible lack of common mode filtration in the units...but even with decent common mode filtration in each unit, the bad earth wiring will get you,