Lenze 8400 - Page 255

Lenze · 8400 HighLine · Reference manual · DMS 12.0 EN · 06/2017 · TD23 255
5 Motor control (MCTRL)
5.9 Servo control (SC)
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Field feedforward control
To have enough voltage reserve available for dynamic acceleration processes, a timely weakening
of the field is required. The field weakening is controlled by the field feedforward control.
The field feedforward control reciprocally reduces the magnetising current from the V/f base
frequency (C00015
) on. The starting point of the reduction can be shifted to low frequencies via the
field feedforward control (C00576
). Thus, more voltage reserve is available for acceleration
processes.
The field feedforward control (C00576
) must be specified in %, based on the rated slip of the
machine.
 Tip!
Generally, the Lenze setting is sufficient for most applications.
• We recommend to increase the field feedforward control for applications with very
dynamic acceleration processes in the field weakening range.
• Reduce the field feedforward control for very slow applications if necessary.
Parameters Info Lenze setting
Value Unit
C00576 SC: Field feedforward control 200.0 %
 Note!
The function of the field feedforward control and thus the field weakening control
requires a correct setting of the V/f base frequency (C00015
).
• The selection of the motor from the »Engineer« motor catalogue and the motor
parameter identification serve to set the V/f base frequency correctly.
• When third-party motors are entered, either the V/f base frequency (C00015
) has to
be calculated manually or a motor parameter identification has to be carried out.
Adapting the V/f base frequency
( 164)
Automatic motor data identification
( 141)
Due to an error in the device software, the field feedforward control of the servo control
only operates properly if the V/f base frequency (C00015
) is reduced by the following
factor after being set:
• 400-V devices: Factor 0.173
• 230-V devices: Factor 0.34
The same factor has to be considered for the field feedforward control (C00576
).
From version 14.00.00, the control parts can be called for an optimum jerk-free
transition to the field weakening range in a 500-
μs cycle. For this purpose, bit 5 has to be
set to "1" int in C02864/1
.
• With this setting, C00015
and C00576 do not have any influence anymore on the field
feedforward control.
• We recommend this setting for new applications.
From version 16.00.00 onwards, the dynamic performance of the field weakening
control is improved with C02864/1
, bit 9 = "1": like this, negative (field) current setpoints
are also permitted at the output of the field controller. If this causes higher torque peaks,
they can be reduced by either reducing the field weakening controller gain C00577
or by
increasing the reset time C00578
.