13.8.2 Notch lter (band-stop lter)
Due to the high dynamic performance or limit frequency of the closed current control loop,
mechanic
al natural frequencies can be acvated 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 lters are integrated in
the speed control loop of the inverter. In the Lenze seng, these lters are switched o:
m m*
0x2944:6
0x2944:5
0x2944:4
0x2944:3
0x2944:2
0x2944:1
Use of the notch lters depending on the resonant frequency
WARNING!
Improperly set notch lters have a negave impact on the response and disturbance behav-
iour of the speed c
ontrol: increased overshoot of the motor speed in case of response behav-
iour and / or higher speed deviaons (extreme case: complete instability of the drive)
In the case of impairment,
▶
the drive that is sll running must either be coasted down by acvang the inverter disable
or immediately be brought to a standsll via a brake.
▶
the speed controller must be opmised again aerwards.
▶
the test procedure must be repeated.
Output frequency Use of notch lters
0...1/2 f
limit_speed_c
ontroller
No
1/2 f
limit_speed_controller...f_limit_speed-Controller
yes, with restricon
<f
limit_speed_controller
yes, without restricon
•
The not
ch lters are suitable for use with resonant frequencies equal to or higher than the
limit fr
equency of the speed controller:
•
Resonant frequencies ≥ f
limit_speed_controller
= 70 Hz ... 110 Hz
•
For resonant frequencies lower than the limit frequency of the speed controller, the use of
suitable speed proles with an S-shaped ramp is recommended.
Conguring the motor control
P
arameterise lter elements in the setpoint path
Notch lter (band-stop lter)
261