Emc-Compliant Installation For Optimized Equipotential Bonding In The Drive System - Siemens SINAMICS G130 Engineering Manual

Fundamental Principles and System Description
Engineering Information

1.9.4.1.1 EMC-compliant installation for optimized equipotential bonding in the drive system

The purpose of any equipotential bonding measure is to ensure that all drive system components (transformer,
converter, motor, gearbox and driven machine) stay at exactly the same potential, - i.e. at ground potential, in order
to prevent the occurrence of undesirable equalizing currents in the system.
Effective equipotential bonding is based on the grounding of all drive components by means of a well-designed
grounding system at the site of installation (protective earth PE). This grounding system should be constructed,
where possible, as a meshed network with a large number of connections to the foundation ground so as to provide
optimized equipotential bonding in the low-frequency range.
Furthermore, the entire drive system including the gearbox and the driven machine must be properly grounded with
respect to high-frequency effects (functional earth FE). This high-frequency grounding must be such that there is
effective equipotential bonding in the high-frequency range between all drive components in each drive system so
that the high-frequency currents that are inevitably generated by converter-fed drive systems are safely controlled
and directed away from the protective ground PE.
The diagram shows a complete drive plus all the major grounding and equipotential bonding measures between the
individual components of the drive.
Drive system designed with all grounding and equipotential bonding measures to reduce bearing currents
The description below explains how proper installation can reduce the inductance of connections, particularly of those
which are colored orange and red in the diagram. On the one hand, this helps to minimize the voltage drops caused
by high-frequency currents in the drive system. On the other hand, most of the high-frequency currents remain in the
drive system in which they originate and so do not have any significant impact on the protective ground PE and thus
on other drive systems and loads.
Protective grounding of the components of the drive system [0]
All electrical and mechanical drive components (transformer, converter, motor, gearbox and driven machine plus (on
liquid-cooled systems) piping and cooling system) must first be bonded with the grounding system (protective earth
PE). These bonding points are shown in black in the diagram and are made with standard, heavy-power PE cables
that are not required to have any special high-frequency properties.
In addition to these connections, the converter (as the source of high-frequency currents) and all other components in
each drive system, i.e. motor, gearbox and driven machine, must be interconnected with respect to the high-
frequency point of view. As a source of interference, the converter must be solidly bonded for high-frequency currents
with the foundation ground. These connections must be made using special cables with good high-frequency
properties.
SINAMICS Engineering Manual – November 2015
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