Siemens SINAMICS G130 Engineering Manual page 88

Fundamental Principles and System Description
Engineering Information
If, by means of a good stator grounding with an EMC-compliant installation and/or an isolating coupling, the
occurrence of rotor shaft currents is prevented, EDM currents are dominant in smaller motors with shaft heights of up
to 100. Circular currents play a secondary role here. So the resulting bearing currents are on a low-risk level for the
bearings and no further measures usually need to be taken. As the shaft height increases, the EDM currents change
slightly, while the circular currents continually increase. From shaft heights of 225 the circular currents become
dominant and critical for the bearings. Therefore, from shaft heights of 225, the use of an isolated bearing on the
NDE side of the motor is very highly recommended.
In principle a dv/dt filter or a sinusoidal filter can also be used at the output of the converter, as alternative to an
isolated bearing in the motor.
SINAMICS Engineering Manual – May 2008
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