Rockwell Automation 20G PowerFlex 750-Series AC Drives - Manual (Page 254)

254 Rockwell Automation Publication 750-RM002B-EN-P - September 2013
Chapter 4 Motor Control
The Reference and Feedback 32-bit REAL value represents drive speed. The
scaling for the speed Reference and Feedback is dependent on drive P300 [Speed
Units]. For example, if P300 is set to Hz, a 32-bit REAL Reference value of 30.0
equals a Reference of 30.0 Hz. If P300 is set to RPM, a 32-bit REAL Reference
value of 1020.5 equals a Reference of 1020.5 RPM. Note that the commanded
maximum speed can never exceed the value of drive P520 [Max Fwd Speed].
Table 12 shows example References and their results for a PowerFlex 755 drive
that has its:
• P300 [Speed Units] set to Hz.
• P37 [Maximum Freq] set to 130 Hz.
• P520 [Max Fwd Speed] set to 60 Hz.
When P300 [Speed Units] is set to RPM, the other parameters are also in RPM.
Table 12 - PowerFlex 755 Drive Example Speed Reference/Feedback Scaling
When a network (communication adapter) is selected as the speed reference, a
32-bit word is used as the speed reference. If P308 [Direction Mode], is set to 1
“Bipolar,” the most significant bit (MSB) is used for direction control. Otherwise,
the MSB is ignored.
Network Reference Value Speed Command Value
(2)
(2) For this example, drive P300 [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 P520 [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 755 drive uses a Bipolar or Unipolar Direction mode. See the
drive documentation for details.
32.5 Hz 32.5 Hz 32.5
IMPORTANT When a 20-COMM Carrier (20-750-20COMM) is used to install a 20-COMM
adapter on a PowerFlex 750-Series drive, the upper word (Bits 16…31) of the
Logic Command Word and Logic Status Word are not accessible. The upper
word is only used and accessible on PowerFlex 750-Series communication
modules (20-750-*) and the embedded EtherNet/IP on PowerFlex 755 drives.