Question:
How can oscillations
in idle running at higher speed (
> half of rated speed) be suppressed?
Answer:
Especially with big three-phase-drives (> 10 kW) or machines with a big number of poles in idle running as well as in case of resonances in the mechanics the appearance of oscillations in the motor current is more likely. A change between motoring mode and regenerating mode and therefore an oscillation of the torque-producing current component is detected by differentiation of the quadrature current component (Vector control mode) respectively differentiation of the dc-bus voltage (V/f-characteristic).
If necessary, the drive performance can be optimised by adapting the
oscillation damping. The oscillation damping is adapted to the drive power at the factory (default setting). The optimisation should be undertaken by checking the following criteria (values can be changes by factor 2…5):
- From experience, the parameter with most influence is code C0234 (damping factor). In case of tendency to oscillation usually the value has to be increased (default setting: 20 %).
- Furthermore, if necessary, the influence of damping C0236) should be increased (default setting: 0.2 Hz).
- The filter time C0235 (default setting: 5 ms) has less influence. If necessary, change in both directions (1…20 ms).
Annotation for vector control mode (C0006 = 1):
In case of slow oscillations of the speed controller the oscillation damping has no influence on the drive's performance.
