DOC-0017-04-EN: AC20 Series - Hardware Installation Manual
122 (154) DOC-0017-04-EN-A 22.03.2023
Issues arising from long Motor Cable runs
Because cable capacitance and hence conducted emissions increase with motor cable length,
conformance to EMC limits is only guaranteed up to a maximum cable length as specified in the table in the
‘Cabling Requirement’ section above.
Screened/armoured cable has significant capacitance between the conductors and screen, which increases
linearly with cable length - typically 200pF/m, though this varies with cable type and current rating.
Long cable lengths may have the following undesirable effects:
- Inverter ‘overcurrent’ trip events as the cable capacitance is charged and discharged at the
switching frequency.
- Increased conducted emissions that degrade the performance of the internal EMC filter due to
common mode choke saturation.
- Increased heating inside the internal EMC filter (as a consequence of a saturated common mode
choke).
- RCD (Residual Current Devices) trips, due to increased high frequency earth current.
These effects can be overcome by adding the following:
- External EMC Filter (Input or Output), located as close as possible to the inverter
- AC Line Chokes
- AC Motor Chokes
Refer to ‘Chapter 7: Associated Equipment’ for recommended Associated Equipment.
For RCD trips, internal Y-Capacitor and Overvoltage Suppressors to earth connections can be removed by
means of a link disconnect. Refer to ‘Chapter 6: Installation’ for details on how to disconnect them from
earth.
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