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Operator Interface and Cont...
2.8 Earthing Screened Cables
It is recommended that the screened control cables be connected with cable clamps at both ends to the metal cabinet of
the frequency converter with cable camps at both ends. Table 2.3 shows earth cabling for optimal results.
Table 2.3 Earthing Screened Cables
High Power Service Manual for Modular F Frame Drives
Correct earthing Control cables and cables for serial communication must be fitted with cable clamps at
both ends to ensure the best possible electrical connection.
Incorrect earthing Do not use twisted cable ends (pigtails) since these increase screen impedance at high
frequencies.
Earth potential protection When the earth potential between the frequency converter and the PLC or other
interface device is different, electrical noise may occur that can disturb the entire system. This can be
resolved by fitting an equalizing cable next to the control cable. Minimum cable cross section is 8 AWG.
50/60Hz earth loops When using very long control cables, 50/60Hz earth loops may occur that can disturb
the entire system. This can be resolved by connecting one end of the screen with a 100 nF capacitor and
keeping the lead short.
Serial communication control cables Low frequency noise currents between frequency converters can be
eliminated by connecting one end of the screened cable to frequency converter terminal 61. This terminal
connects to earth through an internal RC link. It is recommended to use twisted-pair cables to reduce the
differential mode interference between conductors.
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