IT system: EMC conformity evaluation of the drive system

Question:
IT system: Which points have to be taken into consideration in case of IT systems concerning the EMC conformity evaluation of the drive system?

Answer:
According to the EC directives, the entire drive system requires a conformity evaluation concerning the electromagnetic compatibility (EMC).

The product standard EN 61800-3 forms the basis of the conformity evaluation. Although this standard does not define any limit values of the radio interference voltage for IT systems, since a radio interference level measurement is not possible due to the fact, that there is no reference to the earth potential.
As a result,  the application of RFI filters recommended by Lenze for the compliance with the limit values of the electromagnetic compatibility is only valid for drive systems operated at power systems with a grounded neutral conductor (TN or TT systems).

The mode of functioning of RFI filters and mains filters from Lenze is based on the balanced earth reference of the external conductors. So that it is not possible to operate these filters at IT systems or systems grounded at the external conductor.
As described in the documentation for the drive controllers, the filters can be destroyed, when being operated at IT systems and an earth fault happens.

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