Siemens SINAMICS PERFECT HARMONY GH180 - Page 319

The drive requires the use of a PLC to provide average I
ds
to each drive over a network. This is used
to modify the 󹪞ux demand through the 󹪞ux droop scaler.
Since 󹪞ux is provided through induction from the stator to the rotor which is fed by both drives,
󹪞ux feedback to each drive must be precise to control the contribution of each drive. By sampling
the I
ds
feedback of each drive, an average can be calculated to feedback as a reference to each
as a modi󹪝er of the 󹪞ux demand.
The PLC reads the average, individual drive reactive currents to the machine, and then divides
the current requirement into equal shares, and passes the I
ds
current demand share to each drive
through a network connection to the drive. It proportions the total current by the number of
drives connected to the motor, by determining the 󹪝eld-producing current share for each drive.
The drives total magnetizing current must be an equal share from each connected drive. This
then equalizes the torque capability of each drive for the motor total torque so that each drive
is contributing the same amount of torque and magnetizing current. The result is equal sharing
between each drive.
The success of balancing the 󹪞ux producing reactive currents between drives is more an exercise
of balancing the attenuator impedances than in any control algorithm or setting of droop
parameters.
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Figure 8-24 Parallel Drive Control with Induction Motor
Parameter for Flux Droop
The Flux Droop parameter (3195) can be used for scaling, or turning o󹪜 this feature by setting
to zero, the default value.
Note
Use of Flux Droop results in lower 󹪞ux on the machine. This can be adjusted by slightly increasing
the "Flux demand" (3150) parameter to greater than 1.0.
Spinning load must be disabled for running parallel drives on a single induction motor.
Advanced Operating Functions
8.20 Paralleling Multiple Drives
NXGPro+ Control Manual
Operating Manual, A5E50491925A 317