KFU 2-/4-
202
Behavior in motor operation:
If the current set via parameter
Current limit
613
is exceeded, the activated current
limit value controller will reduce the output frequency until the current limit is no longer
exceeded. The output frequency is reduced as a maximum to the frequency set by
the parameter
Frequency limit
614
. If the
Current limit
613
is fallen short of, the out-
put frequency is raised back to the reference value.
Behavior in generator operation:
If the current set via parameter
Current limit
613
is exceeded, the activated current
limit value controller will increase the output frequency until the current limit is no
longer exceeded. The output frequency is increased, as a maximum, to the set
Max-
imum frequency
419
. If the current is below the
Current limit
613
, the output fre-
quency is reduced to the required reference value again.
Parameter
Settings
No.
Description
Min.
Max.
Fact. sett.
613 I limit
0.0 A
ü
I
FUN
ü
I
FUN
614 Frequency Limit
0.00 Hz
999.99 Hz
0.00 Hz
The control behavior of the current limit value controller can be set via the propor-
tional component, the parameter
Amplification
611
, and the integrating component,
the parameter
Integral time
612
. If an optimization of the controller parameters is
necessary in exceptional cases, a setting should be done by a jump alteration of the
parameter
Current limit
613
.
Parameter
Settings
No.
Description
Min.
Max.
Fact. sett.
611
Amplification
0.01
30.00
1.00
612 Integral time
1 ms
10000 ms
24 ms
Note:
The dynamics of the current limit value controller and the voltage con-
troller is influenced by the setting of the parameter
Dyn. voltage pre-con-
trol
605
.
16.5
Functions of Field-Orientated Control
The field-orientated control systems are based on a cascade control and the calcula-
tion of a complex machine model. In the course of the guided commissioning, a map
of the connected machine is produced by the parameter identification and transferred
to various parameters. Some of these parameters are visible and can be optimized
for various operating points.
16.5.1 Current
Controller
The inner control loop of the field-orientated control comprises two current controllers.
The field-orientated control thus impresses the motor current into the machine via two
components to be controlled.
This is done by:
controlling the flux-forming current value I
sd
controlling the torque-forming current value I
sq
By separate regulation of these two parameters, a decoupling of the system equiva-
lent to an externally excited direct current machine is achieved.
