5 Motor control (MCTRL)
5.9 Servo control (SC)
254
Lenze · 8400 HighLine · Reference manual · DMS 12.0 EN · 06/2017 · TD23
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Field weakening controller
The field weakening controller serves to adapt the magnetising current when the maximum control
voltage has been reached so that in steady operation approximately 95 % of the maximally possible
control voltage is output. Thus, there is a voltage reserve for dynamic load or speed variations.
[5-24] Recommendation for the setting of the gain and the time constant of the field weakening controller
Tip!
A field weakening controller set too slow can be recognised by the fact that the actual
speed value cannot follow the speed setpoint in the field weakening range. In this case,
carry out the setting of the field weakening controller as described in the formula. If the
speed setpoint still cannot follow the actual speed value, increase the setting in C00577
to
maximally twice the value and reduce the setting in C00578
according to the formula
mentioned above.
If the field weakening controller is set too fast, vibrations occur in the magnetising current,
in the direct-axis current and in the cross current, in the torque and in the speed in the field
weakening range. This is also audible by an increased motor noise (humming). The
vibrations can be dampened by a decrease of the proportional gain of the field weakening
controller.
Procedure:
• Operate the drive with max. required speed in the field weakening operation.
•Reduce Vp (C00577
) of the field weakening controller until the vibration response
cannot be detected anymore. Increase Tn (C00578
) according to the formula.
Parameters Info Lenze setting
Value Unit
C00577 SC: Vp field weakening controller 0.0010
C00578
SC: Tn field weakening controller 20.0 ms
L
m
: Mutual motor inductance (C00092)
L
sl
: Motor stator leakage inductance (C00085)
n
rated
= rated motor speed (C00087)
I
rated
= rated motor current (C00088)
V
P, FS
4774.65
L
h
[mH] L
ss
[mH]+
L
h
[mH]
2
n
N
[rpm] I
N
[A]⋅⋅
------------------------------------------------------------------
⋅=
C00577 4774.65
C00092 [mH] C00085 [mH]+
C00092 [mH]
2
C00087 [rpm] C00088 [A]⋅⋅
---------------------------------------------------------------------------------------------------------------
⋅=
T
n, FS
20 ms
0.0010
V
P, FS
-----------------
⋅=
C00578 20 ms
0.0010
C00577
--------------------
⋅=
Note!
Vp (C00577) can also be set to 0. In this case, Tn (C00578) should first be set to 2000 ms.
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