Ultra high current DC blocker

Got a question for this thread may some people have answer for me
I use 1to1 isolation toroidal trafo 3.5 KVA in my system
Made one xccelent construction with good quality parts , nice star type of distribution, thick cables and copper bars , volt meter in the output and all working fine
Noticed that after that system become a bit more quiet and smooth not a huge diference but yes there is one ....
i am housed in a 230V single phase country and also my home is in the woods meaning that electricity doesn't suffer the same problems like a big town or one industrial area
no factories or offices ,no huge buildings , area in the woods one house here one house there ....
The problem is that even though system works just fine some nights when system is off yet transformer is connected and active there a loud buzz in the middle of night for a few minutes and then quiet ...At the time there is also no variation on the output voltage reading .
Then i noticed that the same loud buzz comes form the trafo ( with also no variation on the output voltage ) when some load is working in the house like a toaster or a hair dryer
To my understanding one trafo will buzz if excessive load exists on the secondary which here clearly is not the case
A second thing that might make one trafo to buzz is a non managable thing in the primary , which here can be the case when late at night trafo is buzzing at no load conditions and we can assume that the 230 V net has some DC within the AC
still this cannot explain why the exact same buzz and behavior exists when other loads come up in the sockets of the house ( with also no variation on the output voltage ).
thank you very much
 
  • Like
Reactions: Erlend Sæterdal
Hello Sakis!
Would I be correct in assuming you are using a Toroid transformer? An E-I would be much, much better here.

What I think is happening is you have distortion on the primary AC waveform that creates an effective DC potential across the primary. This will cause all transformers to conduct more heavily, but Toroid types are very suseptable to this. In addition, a Toroid is inherently a wide band device, while an E-I type is not. That means the E-I type would be more effective in reducing HF line noise from getting through to your equipment.

You'll need to hang a 'scope across the line, you can use another transformer to step the voltage down and isolate it so you can do this safely while seeing what the AC line looks like. For this application a small Toroid type would be best.

-Chris