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● If the cable shield is connected as described, then it ensures the specified equipotential bonding between the motor
enclosure and converter. A separate RF equipotential bonding conductor is then not necessary.
Concentric copper or aluminum shield
● If the cable shield is not connected due to special secondary conditions, or not adequately connected, then the specified
equipotential bonding is not provided. In this particular case, use a separate RF equipotential bonding conductor:
–
Between the motor enclosure and protective ground rail of the converter.
–
Between motor enclosure and driven machine
–
Use braided flat copper straps or high-frequency cables with finely-stranded conductors for the separate RF
equipotential bonding cable.
–
Ensure that the contacts are made over a large area.
Overall system design
To specifically reduce bearing currents, you must consider the system as a whole, which comprises the motor, converter,
and driven machine. The following measures support you when reducing bearing currents and help to avoid damage:
● In the overall system, set up a properly meshed grounding system with low impedance.
● Use the common-mode filter (damping cores) at the converter output.
● Limit the rise in voltage by using output filters. Output filters dampen the harmonic content in the output voltage.
● The operating instructions for the converter are not part of this documentation. Refer to the configuration information for
the converter.
4.6.4
Insulated bearings when operated with a converter
If the machine is operated from a low-voltage converter, insulated bearings are fitted at the NDE and an insulated encoder
with insulated bearings (option).
Comply with the plates on the machine relating to bearing insulation and possible bridges.
①
Driving machine
②
Motor
③
Coupling
Figure 4-1
Schematic representation of a single drive
NOTICE
Bearing damage
The bearing insulation must not be bridged. Bearing currents can damage bearings.
Also for subsequent installation work, such as the installation of an automatic lubrication system or a non-insulated
•
vibration sensor, make sure that the bearing insulation cannot be bridged.
Please contact the service center if necessary.
•
1LE7
A5E36065207, 04/2018
④
Insulated bearings
⑤
Insulated tachometer fitting
Steel armor
11
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