Rockwell Automation 7000 PowerFlex Medium Voltage AC Drive (B Frame) - Classic Control - Manual (Page 238)

Commissioning 4-79
7000 “B” Frame 7000-UM150I-EN-P – June 2013
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 Autotuning 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.
Flux Regulator Autotuning
The flux regulator is tuned with the motor running at constant speed
using the following procedure:
1. Ensure that parameters "Rated motor rpm" in "Motor Rating" and
"L total leakage" in "Motor Model" are set to the correct value.
2. Set parameter "Autotune select" in "Autotuning" to Flux 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 measured current
and 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
commands stabilise. The drive then performs a normal stop.
Parameter "Autotune Lm" is set to the measured magnetizing
inductance and parameter "Autotune select" is set to Off. Parameter
"Flux Command Base Speed" in "Flux Command" is set to a value
which is intended to produce rated voltage at rated speed and load. The
value of parameter "Autotune T rotor" is calculated from parameters "L
magnetizing" and "Rated Motor rpm" (which gives the rated slip).
If the flux regulator Autotuning is successful, then parameter "L
magnetizing" in "Motor Model" is set equal to "Autotune Lm",
parameter "T rotor" in "Motor Model" is set equal to "Autotune T
rotor", and the flux regulator gains are recalculated. If the flux
regulator Autotuning fails then parameters "L magnetizing" and "T
rotor" are not changed and a warning is issued indicating the cause of
the failure.
L magn low - indicates that the measured value of magnetizing
inductance is less than 1.0 pu. This warning is intended to draw
attention to an unusually low value of magnetizing inductance. This
may occur if the motor is much larger than the drive and the
nameplate parameters do not correspond to the actual motor ratings.
In this case, the measured magnetizing inductance is probably
correct and parameter "L magnetizing" should manually be set equal
to "Autotune Lm".