Fast clock radio & solar panels

[Pinelli]

Just had a solar system connected at home, and for the last three days (since it was switched on), my old clock radio has been running fast - approximately twice the speed it should be running when the solar cells are working.

It's an older clock radio, and relies on mains power frequency for time keeping, so it seems that the inverter is adding enough noise to the mains power to make the clock misbehave.

I really don't mind about the clock, but my question is, could this have an impact on other appliances around the home?

So far the installation company doesn't seem to want to take it seriously, although I haven't really applied much pressure yet (just starting off).

Any thoughts?

[Aaron IIA]

Do yo have a CRO? It would be interesting to have a look at your waveform.

Aaron

[Pinelli]

I do indeed have access to a digital CRO, and I intend to bring it home and get a few screen shots of the power with and without solar panels switched on. Will share when it's done.

[Blknight.aus]

bet its a modified square wave output coming from the panel, the clock radio is timing off of the rising or falling edge of the mains sine wave, there'll be some noise on the supply line or a leaking cap in the supply side of the radio thats tripping the cut threshold of the edge trigger for the counter.

[Aaron IIA]

Have a look when you are exporting all generated power, and when using a lot of power, so running on generated and imported power.

Aaron

[Homestar]

CRO? :D. They haven't made those for a long time, but I know what you guys mean. All grid connected inverters run pure sine wave - they have to to be able to parallel to the grid. Your old clock radio doesn't have its own frequency crystal so yes, it's using the frequency of the mains it can see.

If you viewed the output on an Oscilloscope - or a CRO if you know anyone that runs an electronics museum, then you would see some noise near the peak of the sine wave causing the clock to trigger twice per pulse instead of once. Will look forward to seeming the screen shots when you check this.

I would push back a little bit on the installer - the noise levels induced into the mains have to meet a certain level (not sure what that is though). What brand of inverter? I wouldn't have thought the top quality units would do this, but if you bought on of those systems from the TV, then who knows.

Hope you get it sorted.

[JDNSW]

It would be interesting to see how much hash you have on AM radio! But I have difficulty seeing a waveform bad enough to affect your clock but that does not indicate a problem of some sort with the installation.

I have trouble thinking of other types of appliance that, as a class, would be affected by this, except for AM radios, but there may be individual appliances that don't like this sort of thing, mainly older ones that do not use a switch mode power supply.

John

[Pinelli]

Actually, Bacicat, I do have access to a CRO as well as a digital oscilloscope. Not quite a museum - it's a high school Physics lab :D Also got a kit somewhere in the cupboard to build and analyse a triode amplifier circuit.

Inverter is a Chinese manufacture, Sofar brand. Couldn't find any people having any issues with it online, and the company, which is a local company, seems to have a good rep around here, doing both residential and commercial installations.

I take your point about switch mode power supplies, JDNSW. You would expect most modern power supplies to filter out the crap reasonably well. I'm more pinged off by the lack of care by the installers at the moment. They were more interested in telling me amusing anecdotes about other strange electronic faults than dealing with my concerns.

[Pinelli]

Won't have a chance to look at the output waveform until tomorrow (ie when the sun is up) unless I send the boy up on the roof with a big torch, but have noticed the following graph of the power output of the panels over the last five days. It's been a bit cloudy the last couple of days.

Wonder if the noise is coming from when the inverter is switching in and out as the sun comes and goes?

https://www.aulro.com/afvb/

[pando]

Won't have a chance to look at the output waveform until tomorrow (ie when the sun is up) unless I send the boy up on the roof with a big torch, but have noticed the following graph of the power output of the panels over the last five days. It's been a bit cloudy the last couple of days.

Wonder if the noise is coming from when the inverter is switching in and out as the sun comes and goes?

http://www.aulro.com/app/uploads/33146/Screen_Shot_2015-11-23_at_8_27_03_PM.png

Chucking it out there.....

If the clock radio was running fast on the good sun days (20th - 21st) then I would rule out initially it was related to the inverter switching in and out as a normal operation.

When you get the sillyscope hooked up, would be interested (if it were me) whether load was factor on wave form and weather the wave form is still unsettled in a no load state. Not that would help diagnose the inverter itself but would at least prove that the problem lies there, at least to start the discussion with the installer.

I'd lean on the installer on the basis it is faulty and that their obligations in regards to power quality would have to be the same (or at least ball park) as whats supplied to your property via the network and would hazard a punt that wave form would be something that is mandated.