90 Rockwell Automation Publication 750COM-UM009A-EN-P - May 2017
Chapter 4 Using the I/O
When using a ControlLogix controller with the drive Add-on Profile, the 32-
bit REAL reference word is always DINT 1 in the output image (see Ta bl e 6
).
The 32-bit REAL feedback word is always DINT 1 in the input image.
When using a drive Add-on Profile, the reference and feedback are
automatically properly formatted and displayed as a controller tag. When using
a generic profile, a COP (copy) instruction or user-defined data type (UDDT)
is required to write values to the reference and read values from the feedback.
The reference and feedback 32-bit REAL values represent drive velocity. The
scaling for the speed reference and feedback is dependent on drive 10:1891 -
[Velocity Units]. For example, if Parameter 1891 is set to hertz, a 32-bit REAL
reference value of ‘30.0’ would equal a reference of 30.0 Hz. If Parameter 1891
is set to RPM, a 32-bit REAL reference value of ‘1020.5’ would equal a
reference of 1020.5 RPM. The commanded maximum speed can never exceed
the value of drive 10:1392 - [Max Speed Fwd]. Tab le 7
shows example
references and their results for a PowerFlex 755T drive that has its:
• 10:1891 - [Velocity Units] set to Hz.
• 10:422 - [Maximum Freq] set to 130 Hz.
• 10:1392 - [Max Speed Fwd] set to 60 Hz.
When 10:1891 - [Velocity Units] is set to RPM, the other parameters are also
in RPM.
Table 7 - PowerFlex755T Drives Example Velocity Reference/Feedback Scaling
Network Reference Value Velocity Command Value
(2)
Output Velocity Network Feedback Value
130.0 130 Hz 60 Hz
(3)
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)
32.5 Hz 32.5 Hz 32.5
(1) The effects of values less than 0.0 depend on whether the PowerFlex 755T drive uses a bipolar or unipolar direction mode. See the
drive documentation for details.
(2) For this example, drive 10:1891 - [Velocity Units] is set to Hz.
(3) The drive runs at 60 Hz instead of 130 Hz or 65 Hz because drive 10:1392 - [Max Speed Fwd] sets 60 Hz as the Maximum velocity.
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