Eliminated from:
Inverter Drives 8400 StateLine, HighLine and TopLine from firmware version 12.00.00.00
Behaviour of the new version?
The stability of the current control can be increased by adapting the feedforward control of the field current and cross current controller. The action limits for this adaptation have been extended by the value range increase of the parameters C0985 in each case (adaptation of field current controller gain) and C0986 (adaptation of cross current controller gain).
Which products are affected?
Inverter Drives 8400 StateLine, HighLine and TopLine with a firmware version lower than 12.00.00.00
What happens?
In the case of a very dynamic setpoint change (speed or torque), it can be observed that the control is unstable; the drive tends to oscillate.
When does the problem occur?
The tendency to oscillate results from the parallel control of the cross current and the field current with identical control parameters C0075 and C0076. In the case of very dynamic control loops it may be required to increase the gain for one of the controllers in order to minimise the counteraction or oscillation of the control loops.
Diagnostics options?
In the case of dynamic applications, it may be difficult to distinguish an oscillation due to reached stability limits with high gain factors from the response that results due to the restriction. In both cases, an improvement can usually be achieved by optimising the current controller feedforward control.
Short-term measures/recommendations?
Usually the gain of the field current controller C0985 must be increased to improve stability.
Evaluation:
In the case of applications in which motors are actuated in a sensorless manner in SLVC, very dynamic setpoint changes are rather untypical. Thus the behaviour occurs very rarely. The remedy has a limited scope, since only maximum values of 10 % can be set for the parameters C0985 and C0986.
