4.16.2 Insulated bearings when operating the converter
Operation with a medium-voltage converter with insulated coupling and insulated bearings
If the machine is fed from a 3-level voltage-source DC link converter without a sine-wave filter,
then shaft grounding is fitted at the NDE. The shaft grounding can be implemented as a
grounding device or incorporated in the tachometer. The DE and NDE bearings are insulated.
● Comply with the plates on the machine relating to bearing insulation and possible bridging
options.
● Use an insulated coupling to connect the motor to the driven machine. Otherwise, the
bearing insulation at the DE is bypassed. The consequence of that would be a circulating
current through the motor shaft and the surrounding grounding system.
WARNING
Defective shaft grounding
If the shaft grounding does not function correctly, the shaft can be at a high voltage level that
does not decay quickly enough when the machine comes to a standstill. This can lead to
death or serious injury as a result of electric shock, or bearing damage caused by current
flowing through the bearing.
● Regularly check the shaft grounding and maintain it at the maintenance intervals.
● Observe the operating instructions for the shaft grounding.
① Driving machine ④ Insulated bearings
② Motor ⑤ Insulated tachometer fitting
③ Insulated coupling ⑥ Shaft grounding
Figure 4-2 Schematic representation of a single drive
Preparations for use
4.16 Converter operation
SIMOTICS HV M 1RN76308PR900CG0-Z
36 Operating Instructions 07/2018
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