Eliminated from:
9400 HighLine firmware version V08.00.24.00
Behaviour of the new version?
When the controller is inhibited, the identified speed is kept at zero to prevent the position from drifting.
Which products are affected?
9400 HighLine firmware version ≤ V07.01.06.00
What happens?
In the sensorless VFC and SLVC operating modes, the actual position of the encoder evaluation (FDB_dnActualPos_p) drifts in one direction although a controller inhibit has been set and hence the output frequency setpoint ought to be zero.
The drifting of the position is due to the torque controller which identifies the motor speed. When a controller inhibit is set, its I component is kept to zero. Its P component, however, still provides a small part which is misinterpreted as speed. Since this speed is integrated to a position, the observed drifting of the position is caused.
When does the problem occur?
Whenever a controller inhibit is set.
Possible diagnostics?
Display of the actual position at FDB_dnActualPos_p when the controller is inhibited.
Short-term measures/recommendations?
None
Evaluation:
The behaviour usually shows during commissioning but cannot be avoided.
Published in Service Message No. 26/2010
