Rockwell Automation 20G PowerFlex 750-Series AC Drives - Manual (Page 63)

Rockwell Automation Publication 750-RM002B-EN-P - September 2013 63
Drive Configuration Chapter 1
Draft/wind blows idle fans in reverse direction. Restarting at zero speed and
accelerating damages fans and could break belts. Flying start alleviates the
problem.
There could be occasions when the sweep as well as the CEMF detection fails at
low speeds. This is due to the low levels of motor detection signals. It has been
discovered that Sweep mode is more successful in these cases than Enhanced
mode.
When in Sweep mode the frequency is always swept in the direction of the
commanded frequency first.
Motor detection at low speeds can be difficult. Rather than get a false detection,
the sweep reverses at 3 Hz.