Firmware ≤ 11.00 - DMS 8.0 EN - 10/2011 L 125
8400 StateLine C | Reference manual
Motor control (MCTRL)
V/f characteristic control (VFCplus)
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.
Stop!
• The V/f characteristic control is only suitable for asynchronous motors.
• 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 you pump or fan drive is not suitable for operation with a square-law V/f
characteristic, we recommend using the energy-saving V/f characteristic
control (VFCplusEco). Alternatively, you can use the V/f characteristic
control with 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 ... 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 square-law V/f characteristics, we recommend setting a lower
V
min
or using the energy-saving V/f characteristic control (VFCplusEco).
• 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 following values:
– rated frequency ≠ 50 Hz (star) or
– rated frequency ≠ 87 Hz (delta) or
– number of pole pairs ≠ 2
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)
( 204)
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