User guide

5 Motor control (MCTRL)
5.4 V/f characteristic control (VFCplus)
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Lenze · 8400 BaseLine C · Reference manual · DMS 1.6 EN · 01/2014 · TD05
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5.4 V/f characteristic control (VFCplus)
In case of the V/f characteristic control (VFCplus), the motor voltage of the inverter is determined by
means of a linear or quadratic characteristic depending on the field frequency or motor speed to be
generated. The voltage follows a preselected characteristic.
5.4.1 Parameterisation dialog/signal flow
 Proceed as follows to open the dialog for parameterising the motor control:
1. »Engineer« Go to the Project view and select the 8400 BaseLine C controller.
2. Go to Workspace and change to the Application parameters tab.
3. Select the motor control from the Overview dialog level in the Motor control list field:
• "6: VFCplus: V/f linear" for linear characteristic or
• "8: VFCplus: V/f quadr" for square-law characteristic
4. Click the Motor control V/f button to change to the Overview  Motor control V/f dialog
box.
 Stop!
• The following must be observed when operating drives with quadratic V/f characteri-
stic:
• Please always check whether the corresponding drive is suitable for operation with
a quadratic V/f characteristic!
• If your pump drive or fan drive is not suitable for operation with a quadratic V/f
characteristic, you must use either use the V/f characteristic control function with
a linear V/f characteristic or the sensorless vector control (SLVC).
• For adjustment, observe the thermal performance of the connected asynchronous
motor at low output frequencies.
• Usually, standard asynchronous motors with insulation class B can be operated for
a short time with their rated current in the frequency range 0 Hz ≤ f ≤ 25 Hz.
• Contact the motor manufacturer to get the exact setting values for the max. per-
missible motor current of self-ventilated motors in the lower speed range.
• If you select the quadratic V/f characteristic, we recommend to set a lower V
min
.
• The nameplate data of the motor (at least rated speed and rated frequency) must be
entered if, instead of a standard motor, an asynchronous motor is used with the fol-
lowing values:
•rated frequency ≠ 50 Hz (star) or
•rated frequency ≠ 87 Hz (delta) or
• number of pole pairs ≠ 2
 Note!
When the auto DCB threshold is set (C019) > 0 rpm, there is no torque at the motor shaft
in the lower speed range!
Automatic DC-injection braking (Auto-DCB)
( 97)