KFU 2-/4-
103
9.2.3 Magnetizing
Current
The
Rated magnetizing current
716
is a measure of the flux in the motor and thus of
the voltage which is present at the machine in no-load condition depending on the
speed. The guided commissioning determines this value at about 30% of the
Rated
current
371
. This current can be compared to the field current of an externally ex-
cited direct current machine.
In order to optimize the sensorless field-oriented control system, the machine must be
operated without load at a rotational frequency which is below the
Rated frequency
375.
The accuracy of the optimization increases with the adjusted
Switching fre-
quency
400
and when the drive is in no-load operation. The flux-forming actual cur-
rent value
Isd
215
to be read out should roughly match the set
Rated magnetizing
current
716
.
The field-orientated control with speed sensor feedback uses the parameterized
Rated magnetizing current
716
for the flux in the motor.
The dependence of the magnetizing on the frequency and voltage at the correspond-
ing operating point in question is taken into account by a magnetizing characteristic.
The characteristic is calculated via three points, in particular in the field weakening
area above the rated frequency. The parameter identification has determined the
magnetizing characteristic and set the parameters
Magnetizing current 50%
713
,
Magnetizing current 80%
713
and
Magnetizing current 110%
713
.
Parameter
Settings
No.
Description
Min.
Max.
Fact. sett.
713 Magnetizing current 50%
1.00 %
50.00 %
31.00 %
714 Magnetizing current 80%
1.00 %
80.00 %
65.00 %
715 Magnetizing current 110%
110.00 %
197.00 %
145.00 %
716 Rated magnetizing current
0.01
I
FUN
ü
I
FUN
0.3
I
FUN
9.2.4
Rated slip correction factor
The rotor time constant results from the inductivity of the rotor circuit and the rotor re-
sistance. Due to the temperature-dependence of the rotor resistance and the satura-
tion effects of the iron, the rotor time constant is also dependent on temperature and
current. The load behavior and thus the rated slip depend on the rotor time constant.
The guided commissioning determines the machine data during the parameter identi-
fication and sets the parameter
Rated slip correction factor
718
accordingly. For the
fine adjustment or a check of the rotor time constant, proceed as follows: Load the
machine at fifty percent of the
Rated frequency
375
. As a result, the voltage must be
approximately fifty percent of the
Rated voltage
370
, with a maximum tolerance of 5
%. If this is not the case, the correction factor must be changed accordingly. The lar-
ger the correction factor is set, the stronger the voltage drop when the machine is
loaded. The value calculated by the rotor time constants can be read out via the ac-
tual value
Current rotor time constant
227
. The adjustment should be done at a
winding temperature which is also reached during normal operation of the motor.
Parameter
Settings
No.
Description
Min.
Max.
Fact. sett.
718 Rated slip correction factor
0.01 %
300.00 %
100.00 %
