B-14 Certification 590 Series DC Digital Drive
Increasing Motor Cable Length
Because cable capacitance and hence conducted emissions increase with motor cable length, conformance to EMC limits is only guaranteed with the
specified ac supply filter option up to a maximum cable length as specified in Appendix E: “Technical Specifications".
This maximum cable length can be improved using the specified external input or output filters.
Screened/armoured cable has significant capacitance between the conductors and screen, which increases linearly with cable length (typically 200pF/m
but varies with cable type and current rating).
Long cable lengths may have the following undesirable effects:
• Producing increased conducted emissions that degrade the performance of the EMC filter due to saturation.
• Causing RCDs (Residual Current Devices) to trip due to increased high frequency earth current.
• Producing increased heating inside the EMC ac supply filter from the increased conducted emissions.
These effects can be overcome by adding chokes or output filters at the output of the VSD.
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