Rockwell Automation 20P PowerFlex Digital DC Drive User Manual
Page 309
Rockwell Automation Publication 20P-UM001I-EN-P - February 2013
309
Application Notes
Appendix C
Fine Tuning the Voltage Regulator in the Field Converter
When field weakening occurs, the voltage regulator keeps the armature voltage at
a constant level. The critical point for this regulator is at the beginning of field
weakening, because with the saturation of the motor field the system requires
more consistent changes in the field current in order to carry out a flux change.
Tune the regulator so that the armature voltage undergoes very small changes.
1.
Configure the following Test Generator parameters:
❏ Set Par 58 [TstGen Output] = 4 “Ramp Ref ”
❏ Set Par 59 [TstGen Frequency] = 0.2 Hz
❏ Set Par 60 [TstGen Amplitude] = 10 %
❏ Set Par 61 [TstGen Offset] = to the switching point from the armature
to the field regulation. For example: If Par 162 [Max Feedback Spd] =
2000 rpm, field weakening starts at 1500 rpm. Therefore, set Par 61
[TstGen Offset] = 75 %.
2.
Measure the field current and the armature voltage using analog outputs 1
and 2, by setting:
❏ Par 66 [Anlg Out1 Sel] = 18 “Fld Current”
❏ Par 67 [Anlg Out2 Sel] = 14 “Motor Volts”
3.
Start the drive.
4.
Check the armature voltage via analog output 2. After a possible short
oscillation, the voltage should remain constant. See the Field Voltage
Regulator examples below. You can change the Proportional and Integral
gains of the Field Voltage regulator via Pars 493 [Arm Volt Kp] and 494
[Arm Volt Ki].
5.
Stop the drive.
6.
Set Par 58 [TstGen Output] = 0 “NotConnected”.
IMPORTANT
In most cases, DC motors with independent excitation, work with a constant
field (Par 469 [Field Mode Sel] = 0 “Base Speed”). In this case it is not
necessary to optimize the regulator of the field current and the regulator of the
armature voltage.
IMPORTANT
Before the optimization of the voltage regulator, the speed and field current
regulators must have already been tuned. See Tune the Current Regulator on
page