Ferrite Choke questions

[bcroe]

You need to know the general frequency range of the interference, how strong it is, and how it is
propagating. Then an appropriate filter can be chosen. Throwing beads at it is just a shot in the dark.
Bruce Roe

[kb58]

What I have is a string inverter, though not traditional since its DC optimized per panel. In my case, the source of the interference is known, and is literally coming down the AC lines. If it were RF radiated interference, then I wouldn't have expected the chokes to do anything.

Wait, I'm confused, you say above that you wouldn't expect the chokes to do anything, yet earlier:

Well, bad news is it didn't work...

Which sounds like the RFI may be radiated instead of conducted - or both. How am I mixed up?

[NukeEngineer]

I'm a ham as well and will be facing this demon myself. From what I understand, microinverters/optimizers were never designed to be RFI shielded. Every single box, and its associated panel, and all the wiring, ends up forming a giant transmission antenna. Adding toroids way out at the end of one set of wires does nothing cutting down on the radiated energy. It's an big enough problem that I'm not sure that it is solvable short of moving away from microinverters/optimizers and replacing it with a traditional string converter.

What I have is a string inverter, though not traditional since its DC optimized per panel. In my case, the source of the interference is known, and is literally coming down the AC lines. If it were RF radiated interference, then I wouldn't have expected the chokes to do anything.

[kb58]

I'm a ham as well and will be facing this demon myself. From what I understand, microinverters/optimizers were never designed to be RFI shielded. Every single box, and its associated panel, and all the wiring, ends up forming a giant transmission antenna. Adding toroids way out at the end of one set of wires does nothing cutting down on the radiated energy. It's an big enough problem that I'm not sure that it is solvable short of moving away from microinverters/optimizers and replacing it with a traditional string converter.

[NukeEngineer]

Well, bad news is it didn't work. Good news is, they didn't "do anything particularly bad". I was able to dig deeper and you should never attach these to a single load line, AC or DC. It should be both the supply and return, or both hots, or both hots and the neutral. In other words, the current through the choke should be 0 across all the wires going through it.

Here's an example of chokes on a single line. https://www.youtube.com/watch?v=cgP4B3_K8c8

Worth a try, but I doubted they could filter the strong signal the meter generates. Chokes are for relatively small, but disruptive EMI/RFI.

[Mike90250]

They make choke material out of many different grades of Ferrite. You want a grade that ignores 120Hz, and becomes inductive around 60 KHz. DC current can saturate chokes, AC should not.

[NukeEngineer]

I got some 15mm ferrite chokes to try to filter the smart meter comms noise from my inverters, see my other thread.

I've got limited experience with these. So, is there is current limit on these? I'm clamping around the individual L1 and L2 lines, not both in the same choke. With a fairly small current, the bead I attached early this evening was buzzing. I'm worried that at 50 amps they might overheat or something.