I'm working in elevator world, i'm now in a strange situation.

The 3 Phase synchronous motor is connected by drive then main controller and a distribution board.

The faulty earth leakage circuit breaker keeps tripping when the motor just start to rotate.

I disconnected the UVW wires that connect the VFD to the motor, and the break was released and the earth leakage didn't trip.

The problem is that after checking the coils of the motor (UVW) by the continuity test between them and the motor chassis, there was no contact between them.

What is the possible diagnosis for this situation?


closed as off-topic by DoxyLover, winny, Transistor, Marla, Andy aka Jun 11 '18 at 9:13

This question appears to be off-topic. The users who voted to close gave this specific reason:

  • "Questions on the repair of consumer electronics, appliances, or other devices must involve specific troubleshooting steps and demonstrate a good understanding of the underlying design of the device being repaired. See also: Is asking on how to fix a faulty circuit on topic?" – DoxyLover, winny, Transistor, Marla
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    \$\begingroup\$ Faulty earth leakage breaker? \$\endgroup\$ – Solar Mike Jun 10 '18 at 21:03
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    \$\begingroup\$ And the word “faulty”....? \$\endgroup\$ – Solar Mike Jun 10 '18 at 21:08
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    \$\begingroup\$ So what do you think you should do with a faulty elcb? \$\endgroup\$ – Solar Mike Jun 10 '18 at 21:14
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    \$\begingroup\$ So get a tester and test it... current rating, leakage current and response time... \$\endgroup\$ – Solar Mike Jun 10 '18 at 21:16
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    \$\begingroup\$ Eliminate that as a possible problem - anyone with experience would approach this logically... \$\endgroup\$ – Solar Mike Jun 10 '18 at 21:20

VFD’s produce Common Mode noise that must be filtered. Check for EMI and replace or add filter.

The goal is to have all the Common Mode Noise return to the VFD. Here are some actions that will help reduce or eliminate the tripping of the GFCI. The motor cable should be VFD rated motor cable and the motor and shield should be grounded back to the VFD.

The GFCI measure current imbalance and not actual leakage to ground. So CM noise and imbalanced currents present the same symptom as ground fault leakage > x mA.


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