Rockwell Automation 20-750-PNET Profinet Single Port Option Module - Manual (Page 47)

Rockwell Automation Publication 750COM-UM006A-EN-P - January 2013 47
Using the I/O Chapter 5
Using Reference/Feedback The Reference is a 32-bit REAL (floating point) word of control data produced
by the controller and consumed by the option module. The Feedback is a 32-bit
REAL (floating point) word of status data produced by the option module and
consumed by the controller.
• Reference word is always the second 32-bit word in the output image.
• Feedback word is always the second 32-bit word in the input image.
The Reference and Feedback 32-bit REAL values represent drive speed. The
scaling for the speed Reference and Feedback are dependent on drive Parameter
300 - [Speed Units]. For example, if Parameter 300 is set to Hz, a 32-bit REAL
Reference value of ‘30.0’ would equal a Reference of 30.0 Hz. If Parameter 300 is
set to RPM, a 32-bit REAL Reference value of ‘1020.5’ would equal a Reference
of 1020.5 RPM. Note that the commanded maximum speed can never exceed the
value of drive Parameter 520 - [Max Fwd Speed].
Table 3 shows example
References and their results for a PowerFlex 750-Series drive that has its:
• Parameter 300 - [Speed Units] set to Hz.
• Parameter 37 - [Maximum Freq] set to 130 Hz.
• Parameter 520 - [Max Fwd Speed] set to 60 Hz.
When Parameter 300 - [Speed Units] is set to RPM, the other parameters are also
in RPM.
Table 3 - PowerFlex 750-Series Drive Example Speed Reference/Feedback Scaling
Network
Reference Value Speed
Command Value
(2)
(2) For this example, drive parameter 300 - [Speed Units] is set to Hz.
Output Speed Network
Feedback Value
130.0 130 Hz 60 Hz (3)
(3) The drive runs at 60 Hz instead of 130 Hz or 65 Hz because drive Parameter 520 - [Max Fwd Speed] sets 60 Hz
as the maximum speed.
60.0
65.0 65 Hz 60 Hz (3) 60.0
32.5 32.5 Hz 32.5 Hz 32.5
0.0 0 Hz 0 Hz 0.0
-32.5 (1)
(1) The effects of values less than 0.0 depend on whether the PowerFlex 750-Series drive uses a bipolar or
unipolar direction mode. See the drive documentation for details.
32.5 Hz 32.5 Hz 32.5