LM23 Motor Lm
This is the per phase induction motor magnetizing inductance. The magnetizing
inductance can be monitored in parameter DG09 Magnetizing Current. If the actual
magnetizing current is too high, lower this inductance value in steps of 20. If it is too low,
raise the value.
This parameter is not applicable to PM Synchronous motors and therefore will not
appear.
LM24 Field Weakening Corner
The field weakening corner determines at which speed the peak torque limit starts being
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 identified 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 the modulation grade in parameter DG10 Modulation
Grade. If the value is reaching 100% or higher, the voltage limit is being reached; this
may be caused from a sag in the line voltage. As a result, the peak torque command
must be further limited to maintain control of the motor.
The solution is simply to reduce the value of LM24 to about 60% of synchronous speed
(720 rpm for a 1,200-rpm motor). A setting of 45% of synchronous speed should be used
as the practical lower limit of this parameter.
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