Lenze 8400 motec - Manual (Page 96)

5 Motor control (MCTRL)
5.5 V/f characteristic control (VFCplus)
96 Lenze · 8400 motec · Reference manual · DMS 4.1 EN · 08/2013 · TD05
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5.5 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.
5.5.1 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 motec controller.
2. Select the Application parameters tab from the Workspace.
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.
• This dialog level only shows a simplified signal flow with the most important
parameters.
• When you click the >>More details button in the left-most position, a signal flow with
more details/parameters is displayed.

Stop!
• The following must be observed when operating drives with quadratic V/f
characteristic:
• 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 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.
permissible 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
.

Note!
When the auto DCB threshold ( C00019 ) is set > 0 rpm, there is no torque at the motor
shaft in the lower speed range!
 Automatic DC-injection braking (auto DCB) ( 151)