Rockwell Automation 7000L PowerFlex Medium Voltage AC Drive (C-Frame) - ForGe Control - Manual (Page 246)

246 Rockwell Automation Publication 7000L-UM301D-EN-P - June 2014
Chapter 4 Commissioning
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 L Magn 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.
4. After completing the flux regulator tuning, the drive waits for a few
seconds and adds a sinusoidal perturbation specified by parameter
Autotune Trq Stp to the torque command, causing the speed to vary. After
the initial transient has decayed (this usually takes a few seconds), the
variation in torque and speed are measured and used to calculate the
Total Inertia. The torque perturbation is then removed and the drive
performs a normal stop.
Parameter Autotune L Magn (221) is set to the measured magnetizing
inductance. Parameter FlxCmd RatedLoad in Flux Control Group 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 Lm Rated and
Rated Motor RPM (which gives the rated slip).If the auto-tuning is successful,
then parameter
Lm Rated (131) in Motor Model is set equal to Autotune L Magn,
parameter T Rotor (P132) in Motor Model is set equal to Autotune T Rotor, and
the flux regulator gains are recalculated, parameter Total Inertia (82) in Speed
Control is set equal to Autotune Inertia and the regulator gains are calculated.
If the auto-tuning fails then a warning is issued indicating the cause of the failure.
Following are the list of possible warnings:
L Magnetize 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.
L Magnetize High - indicates that the measured value of magnetizing inductance
is greater than 10.0 pu. This warning is intended to draw attention to an
unusually high value of magnetizing inductance. This may occur if the motor is
much smaller than the drive, and the nameplate parameters do not correspond to
the actual motor ratings. The flux regulator should be tuned using the manual
method described below.
T Rotor Low - indicates that the calculated value of rotor time constant is less
than 0.2 seconds. This is caused by a value of Lm Rated or Rated Motor RPM
which is too low.
T Rotor High - indicates that the calculated value of rotor time constant is
greater than 5.0 seconds. This is caused by a value of Lm Rated or
Rated Motor RPM which is too high.