Rockwell Automation 1557 MEDIUM VOLTAGE AC DRIVE - Manual (Page 234)

9-34 COMMISSIONING
1557-UM050F-EN-P – June 2013
L magn low - indicates that the measured value of magnetizing inductance is less then 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".
L magn high - indicates that the measured value of magnetizing inductance is greater then 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 speed 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 “P motor Model”.
4. Stop the drive.
5. Set parameter “ L magnetizing “ in “P Motor Model “ to the recorded value of “ L magn measured”
6. Calculate an approximate value of the rotor time constant using the following formula :
rad/sec in slip Rated
g magnetizin L
rotor T

Where
Rated slip in rads /sec = 2

f
x
rpm n i speed s synchronou
rpm in speed rated - rpm in speed us (synchrono
Set the parameter “T rotor“ in “P Motor Model” to the calculated value.