4 optimising the stalling behaviour, Optimising the stalling behaviour, 5motor control (mctrl) – Lenze E84DSxxx User Manual
Page 145
Lenze · 8400 protec StateLine · Reference manual · DMS 4.2 EN · 03/2013 · TD05
145
5
Motor control (MCTRL)
5.6
Sensorless vector control (SLVC)
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Tip!
For applications with high dynamic performance and speed/torque accuracy requirements
in the field weakening range, we recommend a time constant Ti ≤ 15 ms.
In this case, the maximum torque should be limited via the nTorqueMotLimit_a and
nTorqueGenLimit_a process input signals to 1.5 x M
N
to ensure stable operation in the field
weakening range.
5.6.4.4
Optimising the stalling behaviour
Motor stalling due to a torque overload in the field weakening range is prevented in sensorless
vector control by means of an inverter-internal stalling current monitoring. In the field weakening
range, hence at frequencies above the base frequency, it reduces the maximum current to prevent
the motor from stalling. The reduction depends on the current field frequency, the base frequency,
the DC-bus voltage and the maximum current (
). Generally it applies that a higher field
frequency causes a stronger limitation of the maximum current.
The field weakening behaviour of the sensorless vector control depends on the setting of the reset
time Ti of the torque controller (
).
The following applies to the reset time Ti (
) > 15 ms:
The behaviour in the field weakening range can be adapted via the override point of field weakening
(
). This parameter serves to shift the frequency-dependent maximum current characteristic:
•
> 0 Hz:
• The maximum current characteristic is shifted by the entered frequency to higher field
frequencies.
• The maximally permissible current and the maximum torque increase in the field weakening
range.
• The risk of motor stalling increases.
•
< 0 Hz:
• The maximum current characteristic is shifted by the entered frequency to lower field
frequencies.
• The maximally permissible current and the maximum torque are reduced in the field
weakening range.
• The risk of motor stalling is reduced.
Note!
We recommend to keep the Lenze setting (0 Hz).