Operating Instructions ACTIVE 06/07156
156 Operating Instructions ACTIVE 06/07
15 V/f - Characteristic
The sensor-less control in configurations 110 and 111 is based on the proportional
change of output voltage compared to the output frequency according to the config-
ured characteristic.
By setting the V/f-characteristic, the voltage of the connected 3-phase motor is con-
trolled according to the frequency. The torque to be applied by the motor at the cor-
responding operating point demands the control of the output voltage proportional to
the frequency. At a constant output voltage / output frequency ratio of the frequency
inverter, the magnetization is constant in the nominal operating range of the 3-phase
motor. The rating point of the motor or end point of the V/f-characteristic is set via
the guided commissioning with the parameter
Cut-Off Voltage 603 and the parame-
ter
Cut-Off Frequency 604.
The lower frequency range, where an increased voltage is necessary for the start of
the drive, is critical. The voltage at output frequency = zero is set with the parameter
Starting Voltage 600. An increase in voltage deviating from the linear course of the
V/f-characteristic can be defined by the parameters
Voltage Rise 601 and Rise Fre-
quency
602. The percentage parameter figure is calculated from the linear V/f-
characteristic. Via the parameters
Minimum Frequency 418 and Maximum Frequency
419, the working range of the machine or the V/f-characteristic is defined.
603 (UC)
601 (UK)
600 (US)
U
418 (FMIN)
419 (FMAX)
602 (FK)
604 (FC) f
Working range
(FMIN): Minimum Frequency 418, (FMAX): Maximum Frequency 419,
(US): Starting Voltage 600,
(UK): Voltage Rise 601, (FK): Rise Frequency 602,
(UC): Cut-Fff Voltage 603, (FC): Cut-Off Frequency 604
Parameter Settings
No. Description Min. Max. Fact. sett.
600 Starting Voltage 0.0 V 100.0 V 5.0 V
601 Voltage Rise -100 % 200 % 10 %
602 Rise Frequency 0 % 100 % 20 %
603 Cut-Off Voltage 60.0 V 560.0 V 400.0 V
604 Cut-Off Frequency 0.00 Hz 999.99 Hz 50.00 Hz
Note: The guided commissioning takes the parameterized rated motor values
and reference data of the frequency inverter into account when it comes
to pre-setting the V/f-characteristic. In the case of three-phase ma-
chines, the speed can be increased at a constant torque if the motor
winding can be switched over from star to delta connection. If the data
for delta connection indicated on the name plate of the three-phase
motor were entered, the cut-off frequency is increased automatically by
the square root of three.
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