Lenze 8400 motec - Manual (Page 102)

5 Motor control (MCTRL)
5.5 V/f characteristic control (VFCplus)
102 Lenze · 8400 motec · Reference manual · DMS 4.1 EN · 08/2013 · TD05
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5.5.3.2 Adapting the Vmin boost
The V
min
boost ( C00016 ) of the motor voltage
• serves to select a load independent magnetising current which is required for asynchronous
motors.
• has an effect on output frequencies below the V/f base frequency ( C00015 ).
• optimises the torque behaviour of the motor.
The general linear and quadratic V/f characteristics are shown in the illustrations below. The
illustrations show the impacts of the parameters used to adapt the characteristic shape.
[5-2] Representation of the linear V/f characteristic (on the left) and quadratic V/f characteristic (on the right)

How to set the V
min
boost:
1. Operate motor in idle state at approx. 6 % of the rated motor speed.
2. Increase V
min
boost ( C00016 ) until the following motor current is reached:
Motor in short-time operation up to 0.5 n
rated
• for self-ventilated motors: I
motor
≈ I
rated motor
• for forced ventilated motors: I
motor
≈ I
rated motor
Motor in continuous operation up to 0.5 n
rated
• for self-ventilated motors: I
motor
≈ 0.8 I
rated motor
• for forced ventilated motors: I
motor
≈ I
rated motor
C00015
C00016
C00015
2
C00016
2
V [V]
out
f [Hz]
V
(100 %)
rmot
1/N/PE AC 264 V
3/PE AC 264 V
3/PE AC 550 V
1/N/PE AC 180 V
3/PE AC 320 V
C00015
C00016
V [V]
out
f [Hz]
V
(100 %)
rmot
1/N/PE AC 264 V
3/PE AC 264 V
3/PE AC 550 V
1/N/PE AC 180 V
3/PE AC 320 V

Note!
V
min
boost is automatically calculated by the motor parameter identification using the
data specified on the motor nameplate so that a no-load current of approx. 0.8 I
rated
motor
results at the slip frequency of the machine.
V/f control (VFCplus + encoder)
If V/f control (VFCplus + encoder) is selected, we recommend a decidedly lower V
min
boost:
• In this case, select a V
min
boost which ensures that approx. 50 % of the rated motor
current flows at slip frequency when the motor is idling.