Rockwell Automation 21G PowerFlex 750-Series AC Drives Reference Manual - Manual (Page 54)

54 Rockwell Automation Publication 750-RM001F-EN-P - February 2012
Chapter 5 General Device and Feedback Monitoring Configuration
Feedback Monitoring The P27 [Fbk Mode] parameter defines whether the feedback monitoring
devices are configured as a single encoder or as dual encoders. When two
encoders are used, the P27 [Fbk Mode] parameter also defines the type of
discrepancy checking that is performed between the two encoders.
You choose the type of feedback device, either sine/cosine or incremental for
encoder 1 by using the P28 [Fbk 1 Type] parameter. You also choose the feedback
type, resolution, and polarity of both encoders.
Configure the feedback type as rotary or linear by using the [Fbk
x Units]
parameter. Configure the resolution in lines per revolution or lines per millimeter
by using the [Fbk
x Resolution] parameter. In these parameter names the x is ‘1’
for encoder 1 and ‘2’ for encoder 2.
For dual encoder configurations, the resolution of the first encoder may be
different than the resolution of the second encoder. After discrepancy testing has
passed, the speed, relative position, and direction used by the safety option are
based on encoder 1.
Feedback Polarity
Configure the direction of polarity to be the same as the encoder or reversed by
using the P30 [Fbk 1 Polarity] parameter. The safety option defines the normal
positive direction for encoders as A leading B. To use encoders where B leads A,
you must enter 1 for the P30 [Fbk 1 Polarity] parameter. Set the P35 [Fbk 2
Polarity] parameter so that the resulting speed direction is of the same polarity as
encoder 1.
Single Encoder
If the P27 [Fbk Mode] parameter is set to 1 Encoder, the single encoder input is
processed redundantly and cross-checked in a 1oo2 architecture. The speed,
direction, and stopped status are derived from the single encoder by the 1oo2
architecture.
Refer to Considerations for Safety Ratings , on page 20 , for more information.
IMPORTANT Feedback device 1 can be a Sin/Cos or incremental feedback device. Feedback
device 2 can only be an incremental feedback device.
IMPORTANT For dual encoder configurations, the resolution of the first encoder may be
different than the resolution of the second encoder, but it must be equal to or
higher than the resolution of the second encoder.