Rockwell Automation 21G PowerFlex 750-Series AC Drives Reference Manual - Manual (Page 49)

Rockwell Automation Publication 750-RM001F-EN-P - February 2012 49
General Device and Feedback Monitoring Configuration Chapter 5
Overspeed Response Time The P24 [OverSpd Response] parameter setting determines the maximum
reaction time from an overspeed event to the initiation of the configured P45
[Safe Stop Type]. The safety reaction time from an overspeed event that triggers a
Safe Stop Type, to the actual initiation of that Safe Stop Type, is equal to the value
of the P24 [OverSpd Response] parameter. The configurable options are 42, 48,
60, 84, 132, 228, and 420 ms.
The P24 [OverSpd Response] parameter setting also determines the speed
resolution that can be achieved. The Overspeed Response Time and the encoder
resolution affect the speed resolution accuracy as shown in the tables on the
following pages.
For example, an encoder resolution of 128 and Overspeed Response Time of 42
ms results in a speed resolution accuracy of ±19.865 RPM if your Safe Maximum
Speed is configured for 100.0 RPM. An SMS Speed fault may occur when
encoder 1 is at 80.135 RPM. However, the SMS Speed fault may not occur until
encoder 1 reaches 119.865 RPM.
If your encoder resolution is not listed in the tables, use these equations.
For rotary systems, the conversion from Overspeed Response Time [OverSpd
Response] to Speed Resolution in revolutions per minute is:
For linear systems, the conversion from Overspeed Response Time [OverSpd
Response] to mm/s is:
119.865
100
80.135
RPM Trip Zone
May Trip
No Trip
Speed Resolution =
(RPM)
15000
(OverSpd Response - 36) x Feedback Resolution
+
Speed (RPM) x 0.02
(OverSpd Response - 36)
Speed Resolution =
(mm/s)
250
(OverSpd Response - 36) x Feedback Resolution
+
Speed (RPM) x 0.02
(OverSpd Response - 36)