Notch Filter (Band-Stop Filter) - Lenze i950 Commissioning Manual

13.8.2

Notch filter (band-stop filter)

Due to the high dynamic performance or limit frequency of the closed current control loop,
mechanical natural frequencies can be activated which may lead to an unstable speed control
loop in the case of resonance.
To mask out or at least damp these resonant frequencies, two notch filters are integrated in
the speed control loop of the inverter. In the Lenze setting, these filters are switched off:
Use of the notch filters depending on the resonant frequency
WARNING!
Improperly set notch filters have a negative impact on the response and disturbance behav-
iour of the speed control: increased overshoot of the motor speed in case of response behav-
iour and / or higher speed deviations (extreme case: complete instability of the drive)
In the case of impairment,
▶ the drive that is still running must either be coasted down by activating the inverter disable
or immediately be brought to a standstill via a brake.
▶ the speed controller must be optimised again afterwards.
▶ the test procedure must be repeated.
Output frequency
0...1/2 f
limit_speed_controller
1/2 f
limit_speed_controller...f_limit_speed-Controller
<f
limit_speed_controller
The notch filters are suitable for use with resonant frequencies equal to or higher than the
•
limit frequency of the speed controller:
Resonant frequencies ≥ f
•
For resonant frequencies lower than the limit frequency of the speed controller, the use of
•
suitable speed profiles with an S-shaped ramp is recommended.
0x2944:1
0x2944:2
0x2944:3
m
= 70 Hz ... 110 Hz
limit_speed_controller
Configuring the motor control
Parameterise filter elements in the setpoint path
0x2944:4
0x2944:5
0x2944:6
m*
Use of notch filters
No
yes, with restriction
yes, without restriction
Notch filter (band-stop filter)
261