Earth leakage tripping with 3 phase motor
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.