Rockwell Automation 7000A PowerFlex Medium Voltage AC Drive - Air-Cooled (A Frame) - Manual (Page 225)

Commissioning 4-71
7000 “A” Frame 7000A-RM001A-EN-P – January 2011
Speed Error
10 ms
63%
0%
Figure 4.19 –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.