Eliminated from:
EVS93xx-EK V8.1, EVS93xx-CK V8.1
Behaviour of the new version?
The internal time constant for the signal filtering of the DC-bus voltage has slightly been increased so that very short (transient) voltage peaks will no longer lead to a disconnection of the torque and resulting unrequested irregularities and disconnections.
What happens?
Dependent on the DC-bus voltage, the torque is set to zero for a short period of time but regenerated within few 10[ms] afterwards. The motion profile of the drive shows a corresponding jerk. It may happen that the following error monitoring is activated.
When does the problem occur?
The behaviour may occur in generator mode operation (e.g. when lowering hoists). The behaviour is caused because the DC-bus voltage is not filtered enough. Transient peaks in the DC-bus voltage profile may already trigger the behaviour since a very small filter time for the DC-bus voltage has been selected.
Which products/versions are affected?
EVS93xx-EK <= V7.1, EVS93xx-CK <= V7.1
Possible diagnostics?
Make an oscilloscope trace by means of an external oscilloscope and a voltage transformer and check it for voltage peaks during generator mode operation.
Short-term measures/recommendations?
Possible measures must lead to a prevention of short-term peaks on the DC-bus voltage.
Possible measures are:
- Extension of the DC-bus via DC-bus connection with further drive controllers
- Installation of brake resistors
- Reducing the dynamics (e.g. reducing the speed controller gain C0070, setting longer deceleration ramps)
- Increasing the following error tolerance if the behaviour leads to disconnection via following error messages
Evaluation:
The behaviour only occurs if the drive system is operated at its electrical limits (overvoltage). If the drive system is dimensioned correctly measures such as brake resistors or DC-bus connection of several drives ensure that the generator mode energy can be buffered/dissipated. If these measured are observed, the behaviour practically does not occur.
