8.7 Flux-Feed Forward
8.7.1 Parameters for Flux Feed-Forward
Parameters for Flux Feed-Forward
Refer to Motor Parameter Menu (1000) in Section Options for Motor Menu (1) of
Chapter Parameter Assignments / Addressing for parameters associated with this function:
• Leakage inductance (1070)
• Saliency constant (1091)
8.7.2 Flux Feed-Forward
Flux feed-forward is a compensation input to increase performance of the ux loop. It works in
the following way:
1. The ux reference is preset to the no-load ux command when enabled. This eliminates a
delay in the response of the ux loop that would occur if starting from zero.
2. Next, the ux based on the load is compensated by feeding a reference proportional to the
torque command to the output of the ux regulator.
This compensates for the reduction of ux resulting from interaction with the torque current,
increasing the I
d
(reactive) current as a linear function of I
q
(torque) current.
The functionality of ux feed-forward is essentially the same for both induction motors (IM) and
synchronous motors (SM). The dierence between the motor types is as follows:
• IM: compensate for leakage inductance losses only using parameter Leakage inductance
(1070) to aect the amount of compensation.
• SM: compensate for the leakage inductance and a part of the mutual inductance, using
parameter Saliency constant (1091). This parameter applies only to SM control, and is used
instead of the leakage inductance parameter. Zeroing the saliency constant still provides the
no load feed-forward term, which essentially provides the no load ux reference. The
saliency constant provides additional compensation for the inductance losses due to
uctuations of torque current for which the ux regulator may be too slow to correct. Setting
it too high can cause the motor ux to be too high resulting in motor over-voltage or
saturation.
Advanced Operating Functions
8.7 Flux-Feed Forward
NXGPro+ Control Manual
240 Operating Manual, A5E50491925A
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