DeviceNet - PF753 - Speed Command

[stretch_af]

Sigh, DeviceNet noob...

I have a 1756-L55, with a DeviceNet module, and 10 PF700 all commanded with DeviceNet. One of the PF700's blew up recently.
There is a New PF753 fitted with a 20-Comm-D module (in Port 4) that I am trying to commission in its place.

To make things fun, there is also installed a 2262D-2R installed (in Port 5) for a remote Auto-Off-Hand selector switch, so that the drive can run without the input from the PLC.
I have the parameters for Hand function set, it does run in manual using a preset reference.

As for the DeviceNet, I have the scanlist and the Inputs and Outputs for the PF753 remapped accordingly. DeviceNet Diagnostics is happy.

The PF753 receives the start command and starts. Commanded speed stays at "0.00" however.
The controller is issuing a reference of 3300, that should be 33 hz.
P545 - is set for Port 4 Reference.
P874 - Port 4 Reference reads 0.00.
I have been pouring over manuals, I can't find what I'm missing.

Why isn't the speed reference making it into the drive?

 

[alan_505]

PowerFlex 700’s use 0 to 32767 for min speed to max speed.
When you send your speed reference to the VSD what does parameter 2 read?

 

[Ken Roach]

I haven't done this sort of interface for a while.

DPI Port 4 is the rightmost option module slot on the PowerFlex 753, so that sounds correct. And the drive is getting its start/stop commands from the network correctly, so this probably isn't a DeviceNet network protocol or connectivity issue.

> P545 - is set for Port 4 Reference

Parameter 545 is Speed Reference A Select. This points to the drive's speed reference when it's in Auto mode, and you can select Speed Reference A or B with discrete inputs or network command bits.

I think that to use the DeviceNet for a speed reference, you would set Parameter 545 equal to "874", which is the Port 4 network module reference value. That might be enumerated as a drop-down that says "DPI Port 4".

Parameter 930 should indicate which parameter is actually being used for Speed Reference, so it should read the value 874.


I know that the PowerFlex 750 series changed from the classic method where 0-32767 = Min Hz to Max Hz that A-B drives had been using since the days of the 1336 Classic on RIO. I don't think you can even configure PowerFlex 753 for a 16-bit Command and 16-bit Reference.

I did some Knowledgebase and user manual digging to check my recollections. If you were using a 20-COMM-D, then the units for the speed reference would be an integer number in 1/100 Hz, where the value "3300" gives you 33.00 Hertz.

https://rockwellautomation.custhelp.com/app/answers/answer_view/a_id/564587/loc/en_US

But when you use a 750-COMM-D option module, the value is a REAL. You have to use COP (not MOV) to do a bitwise copy of a REAL tag with the value 33.00 into the DINT element of the DeviceNet scanner that's mapped to the Reference for that drive.

 

[stretch_af]

Typo, I had the 20-750-Dnet module installed. I knew that was what I had installed.

And yup, it had to be a REAL. That was my issue, problem solved.
Thanks Ken