Siemens 1LA8, Operating Instructions Manual

Page: 40 / 174

4.12.2 Reducing bearing currents
Taking the following actions will reduce the bearing currents:
● Grounding:
– In addition to grounding the machines via the solid protective ground conductor,
supplement the high frequency grounding using braided flat copper straps or high
frequency stranded conductors.
– Ensure that the contacts cover a large area. Solid copper cables are not suitable for
high frequency grounding because of the skin effect.
● Use equipotential bonding conductors:
– Between motor and driven machine
– Between motor and converter
– Between terminal box and RF grounding point at the motor enclosure
● Use a separate RF equipotential bonding conductor:
– Between motor enclosure and protective ground rail of the converter
– Between motor enclosure and driven machine
● 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 must be connected at both ends to the motor and the converter; unshielded
cable ends must be kept as short as possible.
– To ensure good discharging of high-frequency currents, provide contacting over a large
surface area: with 360° contacting at the converter, at the motor for instance with EMC
screw fastenings at the cable entries.
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Concentric copper or aluminum shield Steel armor
Preparations for use
4.12 Converter operation
SIMOTICS TN Series N-compact 1LA8
40
Operating Instructions 05/2014