Corrected from:
Response of the new version:
Any influence of the slip compensation possibly remaining when reaching standstill will be ramped down within one second (ramp slope: 1x rated motor slip per second), independently of the filter time constants set for the slip compensation.
In the case of passive loads (only friction, no forces due to weight or spring forces), there will thus be no longer any unexpectedly long overrun.
What happens?
The motor continues rotating for an unexpectedly long time at low speed after the setpoint speed has already reached standstill.
When does this behaviour occur?
The behaviour occurs after a quick motor stop to standstill when using V/f characteristic control with activated slip compensation.
The overrun behaviour is caused by the possibly remaining influence of the slip compensation after reaching standstill (speed setpoint = 0). The overrun time is proportional to the set time constants of the slip compensation (C966).
Background:
As a matter of principle, with asynchronous motors there is a load-dependent deviation (slip) between actual speed and setpoint speed. The slip compensation is used to compensate for this speed deviation. However, due to operation without feedback, there is no measured actual speed value available for slip compensation. The compensation is based on an arithmetical simulation of the operating state of the motor by means of a motor model.
Which products are affected?
- Servo inverter 9400 HighLine with firmware lower than V14.08.00
- Servo inverter 9400 Servo PLC HighLine with firmware lower than V08.08.00
The overrun time can be reduced by reducing the time constants of the slip compensation in C966.
Evaluation/recommendations:
None.
