Rockwell Automation 1557 MEDIUM VOLTAGE AC DRIVE - Manual (Page 239)

COMMISSIONING 9-39
1557-UM050F-EN-P – June 2013
CORRECTLY TUNED SPEED REGULATOR
8.
Set parameter "Spdreg bandwidth" to the normal operating value. Confirm that the response time is
equal to the inverse of the speed regulator bandwidth and that there is minimal overshoot. For example,
if the speed regulator bandwidth is set to 2 rad/sec, the speed should rise to 63% of its final value in 0.5
second.
9.
Set parameter "Speed ref step" to zero and stop the drive.
Calculating Total Inertia
If the system inertia cannot be measured, it can be calculated if the moment of inertia of the motor and load are
known. The value of parameter "Total inertia" is defined as the time required to accelerate the motor and load to
rated speed when rated torque is applied. It can be calculated using the following formula:
Total inertia = total inertia of motor & load in kg-m
2 X ( rated speed in rad/ sec) 2
rated power in watts
or
Total inertia = 6.21 x 10
-7
total inertia of motor and load in lb-ft
2
X ( rated speed in rpm)
2
rated power in hp
If there is a gearbox between the motor and load, the inertia of the load must be referred to the motor side of the
gearbox.
8. Flux Regulator and Speed Regulator
It is possible to tune the flux regulator and speed regulator at the same time using the following procedure:
1.
Set parameter “Autotune select” in “P Autotune” to 8.
2.
Start the drive. The flux regulator autotuning is performed, and if this is successful, the speed regulator
autotuning is also performed without stopping. If the flux regulator autotuning is not successful then the
autotuning of the speed regulator is not performed. In either case, when the test is complete the drive
performs a normal stop.
The tests performed are the same as described previously for the flux regulator and speed regulator autotuning.