Lenze i950

13.4.8 Set
oscillaon damping
The oscillaon damping serves to reduce the oscillaons during no-load operaon which are
caused by energy oscillang between the mechanical system (mass inera) and the electrical
system (DC bus). Furthermore, the oscillaon damping can also be used to compensate for
resonances.
Damping is possible only for constant oscillaons at a steady-state operang
point.
Oscillaons occurring sporadically cannot be damped.
Oscillaon damping is not suitable for oscillaons occurring during dynamic pro-
cesses (e.
g. acceleraons or load changes). Oscillaon damping is only acve if
the setpoint speed is greater than 10 rpm and the DC-bus voltage exceeds a
value of 100 V.
The determinaon of the oscillaon is based on the acve current. In order to obtain the
alternang component of the acve current, this current is dierenated. This signal is then
passed through a PT1 lter.
0x2B0A:002
0x2B0A:001
0x2B0A:004
0x2B0A:002
0x2DD1:002
Zeitkonstante
Verstärkung
Rampen-Endfrequenz
Begrenzung
Istwert Wirkstrom
Sollwert
Drehfrequenz
Pendeldämpfung
Idencaon of the oscillaon
Before the oscillaon damping can be parameterised, the oscillaon must be idened. One
opon is to look at the motor current when the oscillaon damping is switched o (gain = 0
%). The oscillosc
ope funcon of the »PLC Designer« enables to record the following currents:
•
Q curr
ent
•
Total current
A passive load and connuous
operaon with constant speed (steady-state operaon) result
in a constant current. If the drive oscillates, the motor current oscillates as well. This makes it
possible to detect the frequency and amplitude of the oscillaon by means of the AC compo-
nent in the motor current. Hereinaer this AC component will be referred to as "current oscil-
laon".
Parameter seng
The gain of the oscillaon damping is to be set according to the following equaon:
= ×
×
Stromamplitude
Verstärkung der Schwingungsdämpfung 100%
2 Gerätemaximalstrom
The
me constant must be set so that the oscillaon can be dampened, but that higher-fre-
quency components are ltered from the signal. The me constant is determined from the
reciprocal value of the double current oscillaon frequency:
=
×
1
Zeitkonstante
2 Schwingfrequenz
The calculated oscillaon frequency can be limited before being added to the rotang eld
frequency. The maximum frequency can be derived from the amplitude of the current oscilla-
on, the rated motor current and the slip frequency of the connected motor:
×
= ×
-
2 Amplitude der Stromschwingung
max. Frequenz Nennschlupffrequenz
Motor Bemessungsstrom
Conguring the motor control
V
/f characterisc control for asynchronous motor (VFC open loop)
Set oscillaon damping
247