Equipotential Bonding - Siemens SINAMICS G120P PM330 Installation Manuals

4.6.5

Equipotential bonding

Equipotential bonding
● Equipotential bonding within a cabinet element has to be established by means of a
suitable mounting plate (back plane), to which all metallic housings of the devices and
additional components integrated in the cabinet element (e. g. converter or line filter) are
connected. The mounting plate has to be connected to the cabinet frame and to the PE or
EMC busbar of the cabinet element with excellent electrical conductivity and a large
contact area.
● Equipotential bonding between several cabinet elements has to be established by means
of a PE busbar which runs through all the cabinet elements. In addition, the frames of the
individual cabinet elements are screwed together several times with good conductivity
ensured through the use of contact washers. If extremely long rows of cabinets are
installed in two groups back to back, the two PE busbars of the cabinet groups must be
connected to each other wherever possible.
● Equipotential bonding within the drive system has to be established by connecting all
electrical and mechanical drive components (transformer, cabinet, motor, gearbox, and
driven machine) to the grounding system. These connections are established by means
of standard PE power cables, which do not need to have any special high-frequency
attributes. In addition to these connections, the converter (as the source of the high-
frequency interference) and all other components in each drive system (motor, gearbox,
and driven machine) must be interconnected with respect to the high-frequency point of
view. For this purpose cables with good high-frequency properties must be used.
Grounding and high-frequency equipotential bonding measures
The following figure illustrates all grounding and high-frequency equipotential bonding
measures using the example of a cabinet with a SINAMICS G120.
The ground connections represent the conventional grounding system for the drive
components.
They are made with standard, PE power conductors without special high-frequency
properties and ensure low-frequency equipotential bonding as well as protection against
injury.
The connections inside the SINAMICS cabinet provide a good electrical connection for high-
frequency currents between the metal housings of the integrated components and the EMC
shield busbar of the cabinet. These internal connections can be made over a large area
using metal components of the cabinet. In this case, the contact surfaces must be bare metal
and each contact point must have a minimum cross-section of several cm². Alternatively,
these connections can be established using short, finely-stranded, braided copper cables
with a higher cross-section (≥ 95 mm² / 000 (3/0) (-2) AWG).
The shield and the protective ground conductor of the motor cable provide the high-
frequency equipotential bonding between the converter and the motor terminal box.
Power Module PM330
Hardware Installation Manual, 10/2016, A5E32844552B AD
Connecting up, switching on
4.6 EMC compliant connection
53