4 -
Magnetization +
current impr.+
IxR-K.
In this operation mode, the current set with the parame-
ter Current during flux-formation 781 is impressed into
the motor for magnetization after release. The output
frequency is kept at zero Hz for the
Maximum flux-
formation time
780. After the time has elapsed, the out-
put frequency is increased according to the set accelera-
tion. If the output frequency reaches the value set with
the parameter
Frequency limit 624, the Starting current
623 is withdrawn. There is a smooth transition to the V/f
characteristic, and a load-dependent output current is
obtained. At the same time, the increase of the output
voltage by the IxR compensation becomes effective as
from this output frequency. The V/f characteristic is dis-
placed by the portion of voltage which depends on the
12 -
Magn. +
current impr.+
w. ramp stop
Operation mode 12 contains an additional function to
guarantee a starting behavior under difficult conditions.
The magnetization and starting current impression are
done according to operation mode 2. The ramp stop
takes the current consumption of the motor at the corre-
sponding operating point into account and controls the
frequency and voltage change by stopping the ramp. The
Controller status 275 signals the intervention of the
controller by displaying the message “RSTP“.
14 -
Magn. +
current impr.+
w. R+
IxR-K.
In this operation mode, the functions of operation mode
12 are extended by the compensation of the voltage drop
across the stator resistance. When the output frequency
reaches the value set with parameter
Frequency limit
624, the increase of the output voltage by the IxR com-
pensation becomes effective. The V/f characteristic is
displaced by the portion of voltage which depends on the
In contrast to field-oriented control systems, sensorless control systems feature a
current controller which controls the starting behavior. The PI controller checks the
current impression by parameter Starting current 623. The proportional and inte-
grating parts of current controller can be adjusted via parameters
Amplification 621
and Integral time 622, respectively. The control func
tions can be deactivated by
setting the parameters to 0.
621
Amplification 0.01 10.00 1.00
06/13 Operating Instructions ACU 135
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