The first typology is passive filtering: the most common
approach is to use filters based on resistors, inductors, and
capacitors (RLC filters) or CM chokes at the output of the
inverter so to reduce the common mode dv/dtat the motor
terminals. In particular, when the CM choke is used, only the
CM current in the motor ground line is reduced, whereas the
CM voltage amplitude is maintained unchanged at the motor
terminal such as the shaft voltage and the bearing currents. The
RLC filter has the advantage of contemporarily reducing the
differential mode, the CM voltages, and also the overvoltages
at the motor terminals when long cables are used