Growatt SPF 5000 ES high pitched sound when loaded

[bai_shefa]

Hello,

I have a system with two inverters in parallel (single phase), firmware 040 05 701; 041 05 701. Batteries 4xSLA 12V / 24Ah (They are small, only to support parallel operation).
First I would like to share some of the experience I had with the SPF 5000 ES.
For little over a year and a half since the system is in use, there was one major problem. On one of the inverters, the PV input capacitor (270uF/500V), did failed with short circuit in it. I have a third spare inverter, that I put in place of the damaged one. It has firmware 040.06-041.06_20220104. When it is loaded over ~50% from time to time, PV voltage collapses. This problem is being discussed here: https://diysolarforum.com/threads/pv-voltage-drop-during-inverter-load-spf5000-es.48429/. So, I replaced the capacitor of the damaged inverter and put it back to work. Now when it is loaded over 30%, a high pitched sound comes out of it. I thought it might be, because of the capacitor I put in (it is from old Siemens motor inverter). That's why I took the MPPT board from the spare unit and mounted it to the working one. Same thing, the sound is still there. Here is a link to a video with the sound: https://www.dropbox.com/scl/fi/kber...ey=g1kitorq69fq3u7bddfi6mzf3&st=0hzuo51v&dl=0.
My question is: Is this normal sound for most of these inverters, or may be it is indication of some other failing capacitors? I honestly don't remember, if this sound was there before the inverter failed.

 

[timselectric]

I have the same units and they don't make any sound, other than the fans.

 

[stromy]

These sounds can be emitted from capacitors or from inductors. They do not necessarily mean the emitting component is defective.
Its called "singing capacitors" or "whining inductors". E.g. see here: https://product.tdk.com/system/file...1/singing_capacitors_piezoelectric_effect.pdf
The real problem can only be avoided by the manufacturer of the component. However sometimes inverter software is "tweaked" to somehow reduce the audible noise, e.g. by "switching slower" or outside of human hearing frequency. This usually means additional losses.
If everything else works, and you cannot live with the singing/whining, then you can either replace the whole inverter, or the emitting components.
Diagnosing the components requires working on live dangerous voltages. You need somebody with proper experience and tools for this.

 

[bai_shefa]

Hello, thanks everyone!
Yes, I completely agree that the sound is emitted by a capacitor or most likely by one of the inductors. I suspect one of the two in the upper left of the photo: From there the sound is heard the loudest. I also think the sound is coming from instability in the control loop of one, of the switching regulators. I don't blame the element that makes the sound. I think one of the capacitors has changed parameters and that is causing this instability. And I think if it stays like that, sooner or later it will cause failure in the MOSFETs. Of course, this is just my opinion. I could be wrong and the inverter will work like this for another 10 years. Noise does not cause problems with comfort, because the inverters are in a service room. Diagnostics will be really difficult and dangerous at these voltages. Rather it will be trial and error. I can replace some capacitors and try, but it will be quite laborious.