Siemens SINAMICS DCM Operating Instructions Manual page 90

Connecting
6.1 Instructions for EMC-compliant drive installation
If all the control components in the system (such as PLCs) demonstrate a level of
interference immunity that is suitable for industrial applications, then it is not necessary for
every drive to adhere to limit value "A1".
Non-grounded networks
Non-grounded networks (IT systems) are used in some branches of industry in order to
increase the availability of the plant. In the event of a ground fault, no fault current flows and
the plant can continue with production. If RFI suppression filters are brought into the
equation, however, a fault current does flow in the event of a ground fault, which may cause
the drives to shut down or the RFI suppression filter to potentially be destroyed. For this
reason, the product standard does not define any limit values for these networks. From an
economical perspective, any necessary EMC conformance measures should be taken on the
grounded primary side of the supply transformer.
EMC planning
If two units are not electromagnetically compatible, you can reduce the interference emission
level of the source of interference or increase the interference immunity of the potentially
susceptible equipment. Sources of interference are generally power electronics units with
high power consumption; reducing their interference emission levels requires complex filters.
Potentially susceptible equipment usually refers to controlgear and sensors, including their
evaluation circuit. There is less work involved in increasing the interference immunity of
inefficient units, meaning that - economically speaking - increasing interference immunity is
generally a more favorable option for industrial applications than reducing the interference
emission level. To adhere to limit value class A1 (defined by EN 55011), for example, the
interference emission level on a 150 - 500 kHz line supply connection may not exceed 79
dB(μV), while on a 500 kHz - 30 MHz line supply connection it must not exceed 73 dB (μV)
(9 mV and 4.5 mV respectively).
In industrial applications, EMC between units should be based on a carefully-balanced
combination of the interference emission and interference immunity levels.
The most cost-effective measure that can be put in place to achieve EMC conformance is to
physically separate sources of interference and potentially susceptible equipment - provided
that you have taken this option into account during the planning stage of your machine/plant.
In the first instance, it is necessary to determine whether each unit used is a potential source
of interference or potentially susceptible equipment. Within this context, converter units and
contactors, for example, can be counted as sources of interference, while examples of
potentially susceptible equipment are PLCs, encoders, and sensors.
The components in the control cabinet (sources of interference and potentially susceptible
equipment) must be physically separated, by means of partition plates if necessary, or by
installing them in metal enclosures.
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Operating Instructions, 1.2012, C98130-A7066-A1-05-7619
SINAMICS DCM DC Converter