Rockwell Automation 7000 PowerFlex Medium Voltage AC Drive (B Frame) - Classic Control - Manual (Page 239)

4-80 Commissioning
7000-UM150I-EN-P – June 2013 7000 “B” Frame
L magn 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 "L
magnetizing" 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
"L magnetizing" or "Rated motor rpm" which is too high.
Flux Regulator Manual Tuning
1. Adjust the reference command to a value between 20 and 30 Hz.
2. Start the drive and wait for it to accelerate to the commanded speed.
3. Record the value of parameter "L magn measured" in "Motor
Model".
4. Stop the drive.
5. Set parameter "L magnetizing" in "Motor Model" to the recorded
value of "L magn measured"
6. Calculate an approximate value of the rotor time constant using
the following formula:
T rotor =
L magnetizing
Rated slip in rad/sec
Where,
Rated slip in rads/sec = 2πf X
(synchronous speed in rpm – rated speed in rpm)
Synchronous speed in rpm
Set the parameter "T rotor" in "Motor Model" to the calculated value.