Rockwell Automation 20D PowerFlex 700S AC Drives with Phase II Control Reference Manual - Manual (Page 163)

Rockwell Automation Publication PFLEX-RM003E-EN-E - January 2011 163
Detailed Drive Operation Chapter 1
“Sum” mode is selected when [Speed/TorqueMode] is set to a value of “5”. This
mode allows an external torque command to be added to the speed regulator
output when desired.
“Absolute Min” mode is selected when [Speed/Torque Mode] is set to a value of
“6”. This mode selects the smallest absolute algebraic value to regulate to when
the torque reference and torque generated from the speed regulator are
compared.
Speed Limited Adjustable Torque (SLAT) Min mode and SLAT Max mode are
selected by values “7” and “8”, respectively. SLAT Min and SLAT Max are
improvements on the previous values of the “Min” and “Max” modes (values 3
and 4).
Zero Torque Mode
Operation in zero torque mode allows the motor to be fully fluxed and ready to
rotate when a speed command or torque command is given. This mode can be
used for a cyclical application where throughput is a high priority. The control
logic can select zero torque during the “rest” portion of a machine cycle instead of
stopping the drive. When the cycle start occurs, instead of issuing a start to the
drive, a speed regulator mode can be selected. The drive will then immediately
accelerate the motor without the need for “flux up” time.
Speed Regulation Mode
Operating as a speed regulator is the most common and simplest mode to set up.
Examples of speed regulated applications are blowers, conveyors, feeders, pumps,
saws, and tools.
In a speed regulated application, the speed regulator output generates the torque
reference. Note that under steady state conditions the speed feedback is steady
while the torque reference is a constantly adjusting signal. This is required to
maintain the desired speed. In a transient state, the torque reference changes
dramatically to compensate for a speed change. A short duration change in speed
is the result of increasing or decreasing the load very rapidly.
Note: Inertia Torque Add and Friction Compensation Torque Add are
summed with the output of the speed regulator. See
Inertia
Compensation on page 62 and Friction Compensation on page 57 .
IMPORTANT Zero Torque may excessively heat the motor if operated in this mode for
extended periods of time. A load or flux current is still present when the
drive is operating in zero torque mode. A motor with an extended speed
range or separate cooling methods (blower) may be required.