A line choke can be used to provide improved protection against overvoltages on the line supply and to reduce the current harmonics produced by the drive. The recommended chokes can be used to limit the line current. They have been developed in line with standard EN 50178 (VDE 0160 level 1 high energy overvoltages on the line supply). The inductance values are defined for a voltage drop between phases of between 3% and 5% of the nominal line voltage. Values higher than this will cause loss of torque. These chokes should be installed upstream of the drive.

The use of line chokes is recommended in particular under the following circumstances:
Close connection of several drives in parallel
Line supply with significant disturbance from other equipment (interference, overvoltages)
Line supply with voltage imbalance between phases above 1.8% of the nominal voltage
Drive supplied by a line with very low impedance (in the vicinity of a power transformer 10 times more powerful than the drive rating)
Installation of a large number of frequency converters on the same line
Reduction of overload in cos Ø correction capacitors, if the installation has a power factor correction unit