4 remedies for undesired drive behaviour, Remedies for undesired drive behaviour, 5motor control (mctrl) – Lenze 8400 BaseLine C User Manual
Page 86

5
Motor control (MCTRL)
5.4
V/f characteristic control (VFCplus)
86
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:
: Acceleration time - main setpoint
: 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:
: Imax in motor mode
: Imax in generator mode)
Insufficient speed constancy at high load (setpoint and
motor speed are not proportional anymore)
• Increase slip compensation (
Important: Unstable drive due to overcompensation!
• With cyclic load impulses (e. g. centrifugal pump), a
smooth motor characteristic is achieved by smaller
values in
(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 (
)
• Reduce the reset time of the I
max
controller(
)
• Increase acceleration time (
• Increase deceleration time (
)