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I have a single-phase inverter drive hooked up to an RCD supply, which keeps tripping when powered. Removing the RCD is not an option, so I'm looking into other ways to make this work.

Although dangerous, hypothetically, would removing the Earth connection from the drive solve the problem? In doing so, there would be no current leakage down to Earth.

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  • \$\begingroup\$ Make, model, link to user manual, single-phase / three-phase, does the RCD trip if you run the motor directly ... Put all the details in your question rather than bury them in the comments. \$\endgroup\$
    – Transistor
    Commented Mar 2, 2020 at 12:53
  • \$\begingroup\$ I don't understand. What is tripping? The inverter? Is this an off-grid system? Is the inverter powering the RCD or the other way around? \$\endgroup\$ Commented Mar 2, 2020 at 16:35

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Although dangerous, hypothetically, would removing the Earth connection from the drive solve the problem? In doing so, there would be no current leakage down to Earth.

The possible (or even likely) cause of the RCD tripping are common-mode EMI filter capacitors on the supply AC input inside the inverter drive. Given that they connect both live and neutral to earth, the capacitance on the live side is going to create a bigger earth current than the ones on neutral. This creates an imbalance current and could cause an RCD or GFCI trip.

Of course, there could be other currents to earth that "get there" not via the incoming earth wire but by some other leakage mechanism and so, removing the earth wire might not hypothetically "solve the problem".

But it would be dangerous to do. Consider this: -

enter image description here

C1 and C2 are the common-mode EMI reduction capacitors referred to above and, as can be seen they might connect to the case of the inverter as well as the incoming earth wire. If that earth wire is removed and the case isn't earthed by some other connection, then the case will attain an AC voltage that is 50% of the incoming AC voltage due to C1 and C2 acting as a potential divider. If those capacitors are 10 nF each you would get a nasty belt when touching the case.

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