Siemens SINAMICS G130 Engineering Manual page 133

Motor terminal box
Shield bonding to motor terminal box using
an EMC gland
Inside the cabinet units the housing of the chassis units equipped with the standard, category C3 line filter must be
connected to the PE busbar and the EMC shield busbar with very low inductance. This connection can be
established with a large contact area by means of the metal components used in the construction of the cabinet units.
The contact surfaces must be bare metal and each contact point must have a minimum cross-section of several cm².
This connection can also be established by means of short ground conductors with a larger cross-section
( ≥ 95 mm² ). These must be designed to provide low impedance over a wide frequency range (e.g. made of finely
stranded, braided round copper wires or finely stranded, braided flat copper strips).
SINAMICS G150 / S150 cabinet units and S120 Cabinet Modules are designed in such a way that low-inductance
connections between the housing of the integrated chassis units and the PE busbar and the EMC shield busbar is
ensured.
The rules to be followed for connecting chassis units to the PE busbar and the EMC shield busbar are the same as
those for connecting optional category C2 line filters to the PE busbar and the EMC shield busbar. The optional
category C2 line filters must always be used in combination with line reactors for optimal filtering.
Measures for reducing high-frequency, radiated, electromagnetic interference emissions
In addition to the steep voltage edges at each switching of an IGBT in the inverter, other causes for high-frequency
electromagnetic interference are high-frequency, switched-mode power supplies and extremely high-frequency
clocked microprocessors in the control units of SINAMICS converters.
To limit this interference radiation, closed converter cabinets acting as Faraday cages are required in addition to
shielded motor and signal cables, for which optimal shield bonding must be established at both ends.
If SINAMICS G130 chassis units and S120 chassis units are integrated in an open cabinet frame, the interference
radiation of the devices is not limited to a sufficient degree. To ensure compliance with category C3 of EMC product
standard EN 61800-3, the room where the equipment is installed must have a suitable high-frequency shielding that
ensures adequate shielding (e.g. installing the open cabinet frames in a container with a metallic closure).
If SINAMICS G130 chassis units and S120 chassis units are installed in standard converter cabinets with coated
sheet steel, the interference radiation will fulfill the requirements of category C3 as defined by EMC product standard
EN 61800-3 if the following measures are observed:
•
All metallic housing components and mounting plates in the converter cabinet must be connected, both to
one another and to the cabinet frame, via a large contact area with high electrical conductivity. Large
metallic connections or connections established by means of grounding strips with excellent high frequency
properties are ideal for this purpose.
•
Cabinet covers (e.g. doors, side panels, back walls, roof plates, and floor plates) must also be connected to
the cabinet frame with high electrical conductivity, ideally by means of grounding strips with excellent high
frequency properties.
•
All screwed connections on painted or anodized metallic components must either be equipped with special
contact washers that penetrate the non-conductive surface, thereby establishing a metallically conductive
contact, or the non-conductive surface between the parts to be connected must be removed prior to
assembly to establish a plane metallic connection.
•
For EMC reasons, ventilation openings must be kept as small as possible. The fact that satisfactory cabinet
ventilation requires certain minimum cross-section dimensions due to the laws of fluid mechanics must be
taken into account, however. An appropriate compromise is, therefore, necessary here. For SINAMICS
coverter cabinets ventilation grids are used with standard opening cross-section sizes of app. 200 mm
EMC gland
Shield bonding to the EMC shield busbar in the converter
using an EMC shield clip
EMC Installation Guideline
Engineering Information
SINAMICS Engineering Manual - May 2008
© Siemens AG
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