Emc-Compliant Installation - Siemens SINAMICS G130 Engineering Manual

Fundamental Principles and System Description
Engineering Information
If we apply this formula to the converters and inverters in the SINAMICS range and assume the Infeed to be
400 V 3AC plus the maximum number of parallel motor cables n
motor cables A , then the magnitudes of the theoretical peak values î
max
motor cable shields are calculated to be:
•
Booksize format 1.5 kW - 100 kW
•
Chassis format 100 kW - 250 kW
•
Chassis format 250 kW - 800 kW
The associated rms values I
apply:
•
Pulse frequency f
•
300 m shielded motor cable (with n
Both the peak values and rms values increase in proportion to the line voltage or DC link voltage. Peak values are
not influenced by pulse frequency or cable length while rms values increase in proportion to pulse frequency and
cable length.
Since the above analysis does not take the grounding system inductance into account, the real values are generally
lower. If motor reactors or motor filters are installed, the leakage currents are reduced even further.
What proportion of the high-frequency leakage current I
connection depends on the line filters in the converter chassis unit or converter cabinet, as described on the previous
page. The oscillograms shown in the previous page provide a rough guide as to the reduction in leakage currents at
the PE connection that can be achieved depending on the line filters used. Even when line filters in accordance with
category C2 are installed, leakage current peak values of 300 mA may possibly occur at the PE connection with
converters in Booksize format and 10 A with the largest chassis units.
As the analysis above makes clear, high-frequency leakage currents at the line-side PE connection are not negligible,
even when relatively extensive RFI suppression measures are implemented. For this reason, it is not generally
possible to use residual-current circuit breakers (RCCBs) on SINAMICS drive systems. This applies to both RCCBs
with an operating threshold of 30 mA for personnel protection as well as to RCCBs with higher operating thresholds.

EMC-compliant installation

To ensure that the line filters can achieve the intended filtering effect, it is essential to install the entire drive system
correctly. The installation must be such that interference current can find a continuous, low-inductance path without
interruptions or weak points from the shield of the motor cable to the PE or EMC shield busbar and the line filter back
to the inverter.
For this reason, the lead used to link the converter and motor always has to be shielded and should be a
symmetrical, 3-wire, three-phase cable.
Shielded cables with symmetrically arranged three-phase conductors L1, L2 and L3 and an integrated, 3-wire,
symmetrically arranged PE conductor, such as the PROTOFLEX EMV cable, type 2YSLCY-J supplied by Prysmian,
are ideal.
Shielded, symmetrically arranged three-phase cable with 3-core PE conductor
Alternatively, it is also possible to use a shielded cable containing only three-phase conductors L1, L2 and L3 in a
symmetrical arrangement. In this case, the PE conductor must be installed separately.
Symmetrical 3-wire three-phase cables with concentric copper or aluminum shield
SINAMICS Engineering Manual – May 2008
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© Siemens AG
î
Leak
î
Leak
î
Leak
are approximately 10 times lower when the following supplementary conditions
Leak
matches factory setting
P
and A
max
and the maximum cross-sections of shielded
max
of the leakage currents carried by the
Leak
= 10 A – 30 A
= 30 A – 100 A
= 100 A – 300 A
)
max
carried by the motor cable shield reaches the line-side PE
Leak