User guide

5 Motor control (MCTRL)
5.4 V/f characteristic control (VFCplus)
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Lenze · 8400 BaseLine C · Reference manual · DMS 1.6 EN · 01/2014 · TD05
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5.4.4 Remedies for undesired drive behaviour
Drive behaviour Remedy
Inadequately smooth running at low speeds, especially
in the case of operation with a long motor cable
Automatic motor data identification
( 70)
Problems in case of high starting duty (great mass iner-
tia)
Adapting the Vmin boost
( 84)
Drive does not follow the speed setpoint. The current controller intervenes in the set field frequen-
cy to limit the controller output current to the maximum
current (C0022, C0023). Therefore:
• Prolong acceleration/deceleration time:
C012
: Acceleration time - main setpoint
C013
: Deceleration time - main setpoint
• Consider a sufficient magnetising time of the motor.
Depending on the motor power, the magnetising
time amounts to 0.1 ... 0.2 s.
• Increase permissible maximum current:
C022
: Imax in motor mode
C023
: Imax in generator mode)
Insufficient speed constancy at high load (setpoint and
motor speed are not proportional anymore)
•Increase slip compensation (C021
).
Important: Unstable drive due to overcompensation!
• With cyclic load impulses (e. g. centrifugal pump), a
smooth motor characteristic is achieved by smaller
values in C021
(possibly negative values).
Controller cannot follow dynamic processes, i.e. too
short acceleration/deceleration times in terms of load
ratios.
• Increase the gain of the I
max
controller (C073)
• Reduce the reset time of the I
max
controller(C074)
• Increase acceleration time (C012
• Increase deceleration time (C013)