Lenze 8400 BaseLine C - Manual (Page 85)

Lenze · 8400 BaseLine C · Reference manual · DMS 1.6 EN · 01/2014 · TD05
85
5 Motor control (MCTRL)
5.4 V/f characteristic control (VFCplus)
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _
5.4.3.3 Optimising the Imax controller
Using the Lenze setting of the current limitation controller, the drive is stable:
Most applications do not require optimisation.
The setting of the current limitation controller must be adapted if
• power control including great moments of inertia is performed.
• Recommendation: Increase of the reset time Ti ( C074 ) of the I
max
controller.
• overcurrent errors occur due to load impulses or too high acceleration ramps.
• Recommendation: Reduction of the gain Vp ( C073 ) and reset time Ti ( C074 ) of the I
max
cont-
roller.
5.4.3.4 Torque limitation
The previous chapter, " Optimising the Imax controller ", describes how the drive can be protected
from overload. During commissioning, these settings are carried out once and remain unchanged
afterwards. However, it is often necessary to limit the torque to a lower value for plant or process
reasons.
• To avoid overload in the drive train, the torque in motor mode can be limited via the
nTorqueMotLimit_a process input signal, and the torque in generator mode can be limited via
the nTorqueGenLimit_a process input signal:
Parameter Info Lenze setting
Value Unit
C073 VFC: Vp Imax controller 0.25
C074 VFC: Ti Imax controller 65 ms
Identifier
DIS code | data type
Information/possible settings
nTorqueMotLimit_a
C830/4 | INT
Torque limitation in motor mode
• Scaling: 16384 ≡ 100 % M
max
( C057 )
• Setting range: 0 … +199.9 %
• If keypad control is performed: Parameterisable via C728/1 .
nTorqueGenLimit_a
C830/5 | INT
Torque limitation in generator mode
• Scaling: 16384 ≡ 100 % M
max
( C057 )
• Setting range: -199.9 ... 0 %
• If keypad control is performed: Parameterisable via C728/2 .

Note!
• The accuracy of the torque limitation is limited because the actual torque ( C056/2 ) is
only calculated from the slip speed measured indirectly via the motor current. For this
purpose, the correct entry of the motor data is required.  Motor selection/Motor
data ( 65)
• To avoid instabilities during operation with active slip compensation, the torque limit
values are internally processed as absolute values.
• If slip compensation is deactivated ( C021 = 0) indirect torque limitation is executed
(differential signal between apparent motor current and nTorqueMotLimit_a or
nTorqueGenLimit_a). Above the no-load current of the motor, the accuracy of the in-
direct torque limitation is limited.