Reducing Bearing Currents - Siemens SIMOTICS FD 1MN1 Operating Instructions Manual

4.22.4

Reducing bearing currents

Taking the following actions will reduce the bearing currents:
● Ensure that the contacts are established over a large area. Solid copper cables are not
Equipotential bonding conductors:
Use equipotential bonding conductors:
● Between motor and driven machine
● Between motor and converter
● Between the terminal box and the RF grounding point at the motor enclosure.
Selecting and connecting the cable:
As far as possible, use symmetrically arranged, shielded connection cables. The cable
shielding, made up of as many strands as possible, must have good electrical conductivity.
Braided shields made of copper or aluminum are very suitable.
● The shield is connected at both ends, at the motor and converter.
● To ensure good discharging of high-frequency currents, provide contacting over a large
● If the cable shield is connected as described, then it ensures the specified equipotential
● If the cable shield is not connected due to special secondary conditions, or not adequately
SIMOTICS FD 1MN1
Operating Instructions 02/2019
suitable for high frequency grounding because of the skin effect.
surface area:
– as contact established through 360° at the converter
– at the motor, for instance with EMC glands at the cable entries
bonding between the motor enclosure and converter. A separate RF equipotential bonding
conductor is then not necessary.
Concentric copper or aluminum shield
connected, then the specified equipotential bonding is not provided. In this particular case,
use a separate RF equipotential bonding conductor:
– Between the motor enclosure and protective ground rail of the converter.
– Between motor enclosure and driven machine
– Use braided flat copper straps or high-frequency cables with finely-stranded conductors
for the separate RF equipotential bonding cable.
– Ensure that the contacts are established over a large area.
Preparations for use
4.22 Converter operation
Steel armor
53