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I tried making the below schematic and plugging it in to the AC mains of my home.

I designed it in order to test if it would have any filtering effect on the noise coming from an cheap AC fan that I use which interferes with nearby devices.

As soon as I plugged it in to the mains, the safety breaker AC main's RCD activated. Why did this happen?

I think the RCD activated due to the "large" capacitance I used, as it took enough time and current to charge the capacitors, so the RCD detected this initial "short circuit" current and activated.

Capacitors are 630 V 1 uF LS = 22.5 mm R463N410040N2M

Resistor is 1 Mohm, 200 V rated. I double checked the resistance, and it did not blow/burn.

schematic

simulate this circuit – Schematic created using CircuitLab

AC mains filtering RCD activation

AC mains filtering RCD activation

Next step would be to add a coil in series with the AC lines to reduce the initial current. But I would like to have a feedback on that one first.

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    \$\begingroup\$ What is a "safety breaker"? An automatic circuit breaker? An RCB? Your hookup is illegal in most parts of the world and a safety hazard everywhere. \$\endgroup\$
    – winny
    Commented Feb 14, 2022 at 10:47
  • \$\begingroup\$ @winny AC main's breaker. I added it to the question. It is not safe yes, I had a fuse on the outlet/socket I used. It did not blow up. \$\endgroup\$
    – Christianidis Vasilis
    Commented Feb 14, 2022 at 10:52
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    \$\begingroup\$ Ditto what winny says and, what is the voltage rating for the 1 Meg resistor? \$\endgroup\$
    – Andy aka
    Commented Feb 14, 2022 at 10:52
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    \$\begingroup\$ Can you be clear about what you mean by main breaker and, can you confirm that you don't mean a residual current device (earth leakage device). To me, it looks like it would trip an RCD rather than the main breaker. \$\endgroup\$
    – Andy aka
    Commented Feb 14, 2022 at 10:56
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    \$\begingroup\$ I'm guessing the "Main's breaker" is actually an RCD. 1µF from 220V to ground will create around 70 mA to ground, which is in most cases enough to trip an RCD. \$\endgroup\$
    – Klas-Kenny
    Commented Feb 14, 2022 at 10:56

1 Answer 1

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Typically the two "Y" caps from Live and Neutral to Earth are in the order of 2.2nF. You are exceeding this by a very large amount and it is unsafe.

Initial charge and leakage with 1 uF "Y" caps is too large and an RCD will trip.

Also all three capacitors are "X" type capacitors and they should not be used where "Y" type capacitors are required, the two that connect to Earth. The "X" type is rated to be safe between Live and Neutral.

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