Rockwell Automation 7000A PowerFlex Medium Voltage Drive (A-Frame) - Classic Control - Manual (Page 258)

4-84 Commissioning
7000A-UM150F-EN-P – June 2013 7000 “A” Frame
T rotor low – indicates that the calculated value of rotor time constant
is less than 0.1 seconds
T rotor high – indicates that the calculated value of rotor time constant
is greater than 5.0 seconds.
6. Speed Regulator
The tuning of the speed regulator is determined by two parameters in
the "Speed Control" group:
1. Spdreg bandwidth
2. Total inertia
Parameter "Spdreg bandwidth" is set to a value determined by the
requirements of the application, but parameter "Total inertia" is usually
unknown and must be measured.
Speed Regulator Autotuning
The Autotuning determines the total inertia by measuring the change in
speed that occurs when a low frequency sinusoidal torque perturbation
is applied to the motor. The inertia measurement is not affected by the
load torque as long as the drive does not hit torque limit. Do not
disconnect the driven load from the motor, as it is the total inertia of
motor and load that is being measured. The following procedure
should be used:
1. Ensure that parameters "Autotune spd cmd” and "Autotune trq stp"
in "Autotune" are set to default values.
2. Set parameter "Autotune select" in "Autotuning" to "Speed Reg".
3. Start the drive. The motor accelerates normally up to the speed
specified by parameter "Autotune spd cmd". When the motor
speed has settled at the commanded value, a sinusoidal
perturbation specified by parameter "Autotune trq stp" is added 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.