Rockwell Automation 20G PowerFlex 750-Series AC Drives - Manual (Page 260)

260 Rockwell Automation Publication 750-RM002B-EN-P - September 2013
Chapter 4 Motor Control
Speed Regulation A number of parameter are used to control speed regulation.
Overall Operation for Sensorless Vector Control and Volts per Hertz
Control
The drive takes the speed reference and adjusts it using a proportional and
integral regulator to compensate for slip and the programmed limits.
Overall Operation for Flux Vector Control
The drive takes the speed reference that is specified by the speed reference control
loop and compares it to the speed feedback. The speed regulator uses
proportional and integral gains along with other advanced tuning features to
adjust the torque reference that is sent to the motor. The torque reference is used
to operate the motor at the specified speed. The regulator is designed for optimal
bandwidth for changing speed and load. If an alternate feedback device is used
with automatic tachometer switchover, the alternate values of these parameters
are used.
Desired Speed Regulator Bandwidth - P636 [Speed Reg BW]
The Speed Regulator Bandwidth sets the speed loop bandwidth and determines
the dynamic behavior of the speed loop. As bandwidth increases, the speed loop
becomes more responsive and can track a faster changing speed reference. A
change to this parameter causes an automatic update of P645 [Speed Reg Kp],
P647 [Speed Reg Ki], and P644 [Spd Err Fltr BW]. To disable the automatic gain
and filter update, set this parameter to a value of zero. The configuration settings
for Inertia Adaption (PowerFlex 755 only) is automatically selected when this
feature is enabled.
The maximum allowable value of this parameter is limited by the ratio of P646
[Spd Reg Max Kp] to P76 [Total Inertia], and the type of speed feedback source
in use (encoder versus open loop). For operation following an automatic tach
switchover, the bandwidth specified in P648 [Alt Speed Reg BW] is used.
Total Inertia of Motor and Load - P76 [Total Inertia]
The Total Inertia is the time in seconds for a motor coupled to its load to
accelerate from zero to base speed at rated motor torque. This value is calculated
during an Inertia Tune, after the motor has ramped up to speed and down and
back down to zero speed. Adjusting this parameter causes the drive to calculate
and change the speed regulator gains.