Rockwell Automation 7000L PowerFlex Medium Voltage AC Drive (C-Frame) - ForGe Control - Manual (Page 249)

Rockwell Automation Publication 7000L-UM301D-EN-P - June 2014 249
Commissioning Chapter 4
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:
or
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.
4. FluxSpeed Regulator [SYNCHRONOUS MOTORS]
Configuring the Field Current Reference
Excitation for the synchronous motor is provided by a current regulated field
supply, either a dc supply for a slip ring or dc brushless machine, or a three phase
ac supply for an ac brushless machine. The drive provides an analog current
reference as an input to the field supply. The analog current reference has a range
of 0–10V, where 0V corresponds to zero field current and 10V corresponds to
maximum field current. The scaling of the analog current reference must be
adjusted to achieve a linear relationship between the current reference and the
actual field current. If this is not done, the flux regulator may be unstable. The
scaling of the analog output can be adjusted using the following procedure:
1. Temporarily assign variable Autotune Lmd in Autotuning to the analog
output used to control the field supply e.g. ACB Port 1.
2. Set the analog output scale parameter e.g. Anlg Out1 Scale in Analog
Output to:
IMPORTANT Before the FluxSpeed regulator can be tuned, the analog output for the field
current reference must be set up.
Total inertia
total inertia of motor & load in kg-m
2
rated speed in rad / sec
  2 
rated power in watts
--------------------------------------------------------------------------------------------------------------------------------------------------------------- =
Total inertia 6.21 10
7 – 
total inertia of motor & load in lb-ft
2
rated speed in rpm
  2 
rated power in hp
-------------------------------------------------------------------------------------------------------------------------------------------------- =