KEB COMBIVERT F5 Reference Manual page 299

Problem
Motor noise (Vibration)
Motor noise (squealing/grinding
sound), but not vibration; does
not affect ride quality
Unable to run induction motor
in open loop.
Diagnostics and Troubleshooting
Cause/Solution/Troubleshoot
Increase the Sample Rate for Encoder (LE04) from 4ms (default) to 8ms.
Verify correct motor data and whether motor learn has been performed.
Reduce speed control gains (KP Proportional, KI Integral, KI Offset).
Note, the default settings for an unroped PM motor may be too high.
For induction motors, set the LC01 Control Mode to Open Loop V/Hz.
If the issue is still present, then it is a mechanical issue.
Check whether the (Voltage) Modulation Grade limit is being reached
(100% or above). Refer to Voltage Modulation Grade limit reached for
further troubleshooting.
If occurs after Inertia/ FFTC Learn with Serial or Analog Speed control
reduce LC44 Torque Command Filter.
Check whether the Sample Rate for Encoder (LE04) is too high or too
low; 4-8ms is typical.
Check whether the setting for Encoder Multiplier Factor (LE05) is
correct. For TTL incremental encoder, this value can only be set to a
value of 2; for absolute encoders (e.g. EnDat) typically found on PM
motors, the setting should be a value of 8.
Verify correct motor data. Re-enter as needed.
Perform a motor data learn if not yet completed.
For open loop induction motors, the Low Speed Torque Boost may
need to be decreased or increased.
Verify there are no mechanical issues preventing the motor from
rotating freely.
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