Rockwell Automation 20G PowerFlex 750-Series AC Drives - Manual (Page 60)

60 Rockwell Automation Publication 750-RM002B-EN-P - September 2013
Chapter 1 Drive Configuration
This plot shows a very short time base of the Enhanced mode. If the drive detects
the counter EMF of the motor it can instantly re-connect to the motor and
accelerate to the commanded speed. If the drive cannot measure the CEMF (this
is where the plot picks up) it sends current pulses to the motor in an attempt to
excite the motor allowing the drive to detect the speed of the motor. This usually
happens only at very low speeds. Once the drive has detected the motor it
accelerates to the commanded speed.
PowerFlex 753 Flying Start - Enhanced Mode
Frequency Speed TP 138 Current
Current pulses, motor excitation
Attempt to measure
counter EMF
Output Current
Motor “caught,” Normal Accel