95
Parameter Description - Motor Data
Field weakening speed
The  eld weakening speed determines at which speed the peak
torque limit starts being reduced. It is necessary to reduce the peak
torque limit of the motor since the drive’s ability to force current
into the motor is limited by the applied voltage as rated speed is
reached.
If the drive tries to demand more torque than the motor can produce
given the available voltage and actual motor speed, it is possible
that the breakdown torque of the motor will be exceeded and as
a result the motor will appear to stall and run at less than desired
speed.
Generally this phenomenon can be identi ed as the car reaches
contract speed momentarily but then drops to a lower speed or the
car speed stalls at some speed lower than contract speed. Monitor
parameter ru.42. If the value is reaching 100% or higher, the votlage
limit is being reached. As a result the peak torque command must
be further limited in order to maintain control of the motor.
The solution is simply to reduce the value of LF.16 to about 60% of
synchronous speed (720 rpm for a 1200 rpm motor). A setting of
45% of synchronous speed should be used as the practical lower
limit of this parameter.
IM
Unit: rpm
Value range: 0.0...6000 rpm
Default setting: 960.0 rpm
Initial adjustment value: approx. 80% of synchronous
speed
For PM motors this parameter is not necessary and therefore
is not visible.
PM
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