This process magnies osets and noise that are introduced by the measurements. In order to
limit the gain at extremely low frequencies, the transfer function is approximated by 1/(s + a),
where a is the S/W compensator pole. The pole introduced by a aects the motor ux phase
angle, and is chosen to be low enough such that the error introduced is small.
In typical applications that have short cables between the motor and the VFD the default value of
a, 2 rad/s, provides a good compromise between ux phase angle error and reduced gain at dc.
In long cable applications, the eect of compensating the cable voltage drop, resistive and
inductive, causes additional terms to be introduced in the motor ux calculation, i.e. V
motor
= V
vfd
– I*R
cable
– I*w*L
cable
. This requires that a be increased so as to avoid the sensitivity of osets and
measurement errors. However, there is an adverse eect on the starting torque capability.
Typically for cables longer than 5000 m, a can be set in the range of 4 to 6 rad/s. With such a
setting, enable High starting torque mode (2960) to maintain good starting torque capability.
Table 6-54 Flux Control Menu (3100) Parameters
Parameter ID Unit Default Min Max Description
Flux reg prop gain 3110 1.72 0.0 10.0 Flux PI regulator proportional gain term.
Flux reg integral
gain
3120 1.0 0.0 1200.0 Flux PI regulator integral gain term.
Flux lter time const 3130 sec 0.0667 0.0 10.0 Time constant of the low pass lter used on the
ux error.
Flux table menu
Note: To be re‐
leased in a later
software version.
3131 Submenu Flux shaping table parameters
Flux demand
Note: To be re‐
leased in a later
software version.
3150 pu 1.0 0.16 10.0 Set the ux demand, or desired V/Hz ratio. Use the
default setting to set the V/Hz ratio to nameplate
values.
Flux ramp rate
Note: To be re‐
leased in a later
software version.
3160 sec 0.5 0.0 5.0 Set the ramp time to go from zero to rated ux.
This time establishes the time to magnetize the
motor.
Energy saver min
ux
3170 % 100.0 10.0 125.0 Set the lowest value of ux, as a percentage of
rated motor ux that the drive will apply to an
unloaded motor.
Energy Saver is enabled if you enter a value that is
less than the ux demand. The control establishes
the amount of ux or motor voltage that minimi‐
zes the losses in the motor.
Flux droop 3195 % 0 0 200 Set ux droop for parallel drives, to keep the volt‐
age balanced between drives. This parameter is
used for ne adjustments on ux droop with the
main reference coming from an external PLC. Re‐
fer to Section Parallel Drive Control for a single IM.
Parameter Assignment/Addressing
6.8 Options for Stability Menu (3) - rst half
NXGPro+ Control Manual
130 Operating Manual, A5E50491925A
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