Rockwell Automation 20G PowerFlex 750-Series AC Drives - Manual (Page 226)

226 Rockwell Automation Publication 750-RM002B-EN-P - September 2013
Chapter 4 Motor Control
Configuration
Enable Load Observer by setting P704 [InAdp LdObs Mode] to 2
“LoadObserver.” The total inertia value P76 [Total Inertia] is required for this
feature. Ideally it is measured during the inertia test as part of the drive startup.
The next best approach is to manually enter a reasonably close (calculated) value.
In Load Observer mode, P711 [Load Observer BW] is used to set the natural
frequency of a low pass filter in radians per second (R/S). Typical values for Load
Observer Bandwidth range from 10 to 150 with the higher values being more
responsive to disturbances but with increased system noise. There is no nominal
best setting, but 40 R/S is a suggested starting point. This selection may not
function well in sloppy geared systems. Unlike with Inertia Adaption, there is no
automatic parameter setting associated with the Load Observer.
The Load Observer can also be used in conjunction with P695 [Inertia
CompMode]. When used together, both the load torque and acceleration torque
required from the speed regulator are minimized.
Where can Load Observer be used?
Load Observer can be used on systems where load disturbances are preventing a
further increase in drive performance. The Load Observer can be applied to both
periodic load disturbances, such as a piston pump, and random load disturbances.
Load observer can be applied on systems that are not suitable for Inertia
Adaption. Load Observer cannot be active at the same time as Inertia Adaption.
Motor Control Modes P35 [Motor Ctrl Mode] selects the output mode of the drive to match the type of
motor control to use. The Default selection is a value of 1 = “Induction SV.” This
parameter is set during any of the assisted start up routines either via the HIM or
connected software tool wizard. The parameter settings follow.
• InductionVHz (0) – Induction motor, volts per Hertz control mode.
Connected to an induction motor. Used for variable torque applications
with improved efficiency energy savings and variable speed constant
torque applications such as conveyors. Can also be used in multi-motor or
synchronous motor applications.
• Induction SV (1) – Induction motor, sensorless vector control mode.
Connected to an induction motor. Used for most constant torque
applications. Provides excellent starting, acceleration, and running torque.
• Induct Econ (2) – Induction motor, economize control mode.
Used for additional energy savings in constant torque applications that
have constant speed reduced load periods.