Rockwell Automation 7000L PowerFlex Medium Voltage AC Drive (C-Frame) - ForGe Control - Manual (Page 251)

Rockwell Automation Publication 7000L-UM301D-EN-P - June 2014 251
Commissioning Chapter 4
operating conditions, the variations do not significantly affect the operation of
the flux regulator.
The other aspect of flux control is the variation of motor flux with speed. This is
determined by two parameters:
1. Base Speed in Flux Control
2. FlxCmd RatedLoad in Flux Control
In most applications, the motor runs at constant flux below rated speed and
constant voltage above rated speed. The motor flux is normally set to a level that
provides rated voltage at rated speed and full load. The flux level required to
achieve this is a function of the motor parameters. The flux regulator auto-tuning
determines a value of rotor flux that should provide rated motor voltage at full
load and rated speed and sets the flux command parameter to this value.
Speed Regulator
Refer details given for Induction motor section.
FluxSpeed regulator Auto-tuning [Synchronous Motor]
The FluxSpeed regulator is tuned with the motor running at constant speed
using the following procedure:
1. Ensure that the analog reference for the field current has been set up as
described previously, and that parameter
L Total Leakage has been set to
the correct value.
2. Set parameter Autotune Select in Autotuning to FluxSpeed Reg.
3. Start the drive. The motor accelerates normally up to the speed specified
by parameter
Autotune Spd Cmd. The motor magnetizing inductance is
calculated from the magnetizing current reference and the flux feedback
and parameter
Autotune Lm is set to this value. The flux command is then
set to a value that should produce rated voltage at rated speed and load.
The resulting change in the flux level may cause the magnetizing
inductance to change. This process is repeated until the magnetizing
inductance and flux command stabilize. If a position encoder is fitted to
the motor, the angle between the measured flux and the encoder zero is
measured and parameter
Encoder offset is adjusted to align the encoder
with the motor flux.
TIP If a position encoder is fitted to the motor, the FluxSpeed regulator auto-
tuning is performed with the encoder feedback turned off because it is
assumed that the encoder has not been aligned with the rotor axis yet. Since
less starting torque is produced with the encoder feedback off, this test should
be performed with reduced load. The encoder offset measurement is also most
accurate with no load on the motor.