4 v/f characteristic control (vfcplus), V/f characteristic control (vfcplus), 5motor control (mctrl) – Lenze 8400 TopLine User Manual

Page 157

Lenze · 8400 TopLine · Reference manual · DMS 6.0 EN · 06/2014 · TD05/TD14

157

Motor control (MCTRL)

5.4

V/f characteristic control (VFCplus)

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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.



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) or servo control (SC).

• 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

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 (

) is set > 0 rpm, there is no torque at the motor

shaft in the lower speed range!