Malfunctioning of Seimens PLC input card and Lenze PLC drives

Hi;

In our corrugator plant, there are one Corrugator and five Flexo graphic printing machines. One of them is a BOBST brand French made printing machine having Lenze 9300 PLC drives with Siemens PLC. We faced an issue that two Lenze drives and one PLC input card have become malfunctioned within three years. The cost of these drives is too high. OEM stated that this is because of harmonics. We did a power quality analysis and found the THDI up to 16% for that infected machine. The measurements had been done at main LT-room from where the power is being distributed to all machines. We found that the harmonics of corrugator was much higher as compare to BOBST but only one drive of corrugator malfunctioned during past three years. We are confused if we install or not the Active harmonic filters because these are much costly and there is no guarantee that drives would not malfunction after installation of AHF.

If anyone has experience in this regards, please share or give advice how do I proceed.

By harmonics, are you sure they mean on the supply side ?
I havent experienced anything like this, but I would be surprised that harmonics on the supply should be a problem for a VFD.
I would suspect voltage spikes could damage a VFD, not harmonics.

You could have the damaged VFDs analyzed to pinpoint exactly what part is defective, which could point to the culprit.