Rockwell Automation 20D PowerFlex 700S AC Drives with Phase II Control Reference Manual - Manual (Page 57)

Rockwell Automation Publication PFLEX-RM003E-EN-E - January 2011 57
Detailed Drive Operation Chapter 1
The flying start function works by using the voltage feedback from the motor to
determine the speed of the motor. When the speed is determined, the drive
provides flux up time for the motor. Then the drive begins ramping the motor to
the commanded speed from the speed determined by the voltage feedback. This
process will prevent an overcurrent trip and significantly reduce the time for the
motor to reach its desired frequency. Since the motor is “picked up” smoothly at
its rotating speed and ramped to the proper speed, little or no mechanical stress is
present. Note that if the voltage feedback from the motor is zero (0), the drive
will ramp the motor up to the commanded speed from zero speed.
Configuration
Sensorless flying start is enabled by setting parameter 153 [Control Options] bit
3 “Flying Start” = 1. When set to zero (0) the sensorless flying start function is
disabled.
Friction Compensation The friction compensation block is used to calculate breakaway torque and the
torque needed just to keep the motor running at a constant speed due to friction.
Parameter 64 [FricComp Spd Ref ] is linked to parameter 43 [Ramped Spd Ref ].
The speed reference is needed because the torque needed due to friction is much
more near zero speed than at higher speeds.
Friction compensation is enabled by setting parameter 151 [Logic Command] bit
11 “Frict Comp” to “1.”
Parameter 65 [FricComp Setup] is used to configure the friction compensation
algorithm. This is a packed word of 3 digits. Each digit has a possible selection of
10 levels.
• The least significant digit sets the speed threshold in intervals of 0.0005 pu
speed.
• The next (middle) digit sets the hysteresis band for the “units” digit in
intervals of 0.0005 pu velocity.
• The most significant digit sets the number of time steps from stick to slip,
each step is 0.002 sec.
Units
Hysteresis
Number of
Time Stops
N N N